Loading...
HomeMy WebLinkAbout009 Stormwater Design Report   Range 5 Apartments ‐ Stormwater Design Report  Page 1  January 2024  TABLE OF CONTENTS  Overview .........................................................................................................................................  2  Existing Conditions ........................................................................................................................... 2  Stormwater Design .......................................................................................................................... 3  Proposed Stormwater Improvements ............................................................................................. 3  Fowler Lane Stormwater Trunk Main .............................................................................................. 4  Off‐Site Flow .................................................................................................................................... 5  Drainage Basin Summary ................................................................................................................. 6    APPENDIX  Appendix A .................................................................................  Geotechnical Investigation Report  Appendix B ....................................................................................................... Drainage Basin Maps  Appendix C ............................................................................................. Drainage Basin Calculations  Appendix D ......................................................................... Stormwater Facilities Maintenance Plan  Appendix E  ................................................................................... Groundwater Monitoring Results                                Range 5 Apartments ‐ Stormwater Design Report  Page 2  January 2024  OVERVIEW  The purpose of this report is to detail the stormwater management design for the proposed Range 5  Apartments project. The proposed project will develop the 20.515‐acre site with a city street grid, a large  city park, and two apartment sites containing 312 dwelling units in a combination of 36‐plex and 12‐plex  apartment buildings. The property is legally described as Tract 2 of Certificate of Survey No. 1996, located  in the northwest ¼ of Section 23, Township 2 South, Range 5 East of the P.M.M., City of Bozeman,  Montana.  The property is largely surrounded by county properties in agricultural use to the north, south and west.  The property to the east of the project site is currently vacant land that is annexed into the city and zoned  for residential development in the future. Fowler Lane Runs along the western side of the property.   Proposed infrastructure improvements for the project include extensions of the city street grid and  extensions of the city water and sanitary sewer systems within the street grid. Fowler Lane will be widened  across the project frontage to a city minor arterial standard. Apex Drive will be installed along the northern  property boundary, and Bennett Boulevard will be extended from its current location on the southeastern  property corner, west to Fowler Lane. Edgerton Avenue and Gabriel Avenue will be installed in a north /  south alignment across the property between Bennett and Apex. These two streets are situated in  approximately the same location as they are proposed on the Buffalo Run project to the south, so that  future development of the properties between this project and buffalo run can connect the streets.   The proposed development of the two apartment sites on the property will include 11 residential  buildings, garages, car ports, open space areas, and associated parking lots. The purpose of this design  report is to size the conveyance systems and facilities for the on‐site improvements proposed with this  project and provide preliminary sizing for the storage facilities for the proposed infrastructure  improvements. A separate design report will be prepared for the infrastructure improvements submittal  that provides complete sizing for the infrastructure conveyance and storage facilities.   EXISTING CONDITIONS  The project currently has a single residential building along Fowler Lane with surrounding agricultural  fields. The property generally slopes gently from south to north at approximately 1.5%. A subsurface soils  investigation was performed by IMEG Corp in June of 2023. Groundwater monitoring was performed by  IMEG Corp throughout the spring and summer of 2023. The investigation and monitoring indicated that  seasonally high groundwater varied between 0.04 below ground surface (bgs) and 2.85 bgs. Groundwater  monitoring results can be found in Appendix D for reference.   There is a large area of existing wetlands on the east side of the site associated with the irrigation ditch  that flows from south to north along the eastern side of the property. A large, existing irrigation ditch  currently flows across the property along the east side of Fowler Lane as well, while another roadside  ditch flows along the west side of Fowler Lane. A fourth ditch also flows south to north across the center  of the property. After conversation between the applicant and the ditch company, it is understood that  this ditch has not been in use for several years and can be abandoned across the project.   As part of the Buffalo Run project off‐site improvements Fowler Lane is scheduled to be paved across the  project frontage from Buffalo Run to Stucky Road. As part of these Fowler Lane improvements, the  irrigation ditch along the east side of Fowler will be relocated to the west side of the street and the    Range 5 Apartments ‐ Stormwater Design Report  Page 3  January 2024  western ditch will be widened. Therefore, the existing ditch across the project frontage along the east side  of Fowler Lane will no longer need to be maintained and can be abandoned.      STORMWATER DESIGN  The proposed stormwater improvements for the project site are designed to meet the City of Bozeman  Design Standards and Specifications Policy (2004 – w/ addendums approved through 03/13/20). The  design storm return interval for sizing retention and detention facilities in the City of Bozeman is 10‐years.  The storm duration for these design events is 2‐hours. Conveyance facilities are required to have sufficient  capacity to convey a 25‐year storm event.   The Montana Post‐Construction Storm Water BMP Design Guidance Manual recommends 3 feet of  separation between seasonal high groundwater levels and stormwater retention/detention facilities.  Given the high levels of groundwater on Tract 2, this recommendation is not feasible, so the stormwater  facilities have been designed with separation less than 3 feet. The groundwater monitoring results for the  project indicate that the peak seasonal high groundwater (SHGW) elevation in each monitoring well lasted  for approximately one week. In general, the groundwater elevations monitored before and after that one‐ week peak were ~6” lower than the peak elevation, with the average groundwater elevations across the  monitoring period being ~1’ lower than the peak SHGW elevations. So, although the stormwater facilities  are set at or slightly above the SHGW elevations, the groundwater table is only expected to be within 6”  of the facilities for a short period of time each year.     PROPOSED STORMWATER IMPROVEMENTS  Stormwater management for the development on Tract 2 will be handled by on‐site retention ponds and  a series of underground infiltration chamber systems. Retention facilities are summarized at the end of  this document in Table 2. The systems designed as detention facilities are summarized in Table 3.  For the most part, stormwater runoff generated from the proposed City Road network will be directed to  separate retention/detention facilities from those that receive runoff from the site’s private  improvements. Although all proposed stormwater systems will currently be maintained by the property  owner, this separation of facilities is intended to allow the city to take over maintenance of the  infrastructure related facilities in the future, if they choose.   Since the public street and utility improvements will be permitted through a separate infrastructure  improvements submittal, the proposed stormwater facilities treating the public improvements have only  been sized for storage capacity with this report. An additional stormwater design report will be provided  during infrastructure review and approval that will further detail the proposed facilities and will provide  sizing and conveyance calculations for the proposed curb, inlets, and pipes that drain the public  improvements.    Retention Ponds: The retention ponds have been sized to retain the 10‐year 2‐hour storm event with a  maximum water storage depth of 1.5 feet. The ponds will have 4:1 maximum side slopes and will be finish  graded with topsoil and seeded for easy maintenance.     Range 5 Apartments ‐ Stormwater Design Report  Page 4  January 2024  Chamber Systems: The proposed underground infiltration systems will be StormTech SC 160 LP chamber  systems. These systems are plastic arched‐shaped chambers with washed rock bedding/backfill that  provide adequate stormwater detention volume while infiltrating stormwater into the ground. The area  underneath the chamber will be excavated down to native gravels and backfilled with well‐draining  material to ensure the systems have adequate infiltration. The detention scenarios for the chamber  systems were sized by applying the DEQ infiltration rate for gravel (2.6 inches per hour) from Circular DEQ  8, Appendix C, Table 2 to the footprint area of each chamber system. Appendix C states that the infiltration  rates provided can be increased by 50% with the use of sediment reducing pre‐treatment facilities. All the  chamber systems are designed with a weir to divert the initial flow from any storm event to a lined isolator  row for pre‐treatment and sediment collection. Therefore, the 2.6 in/hr infiltration rate was increased to  3.9 in/hr for the chamber design. This infiltration rate is believed to be extremely conservative since  infiltration tests on native gravel in Bozeman on other projects have produced infiltration rates that are  significantly higher than 3.9 in/hr.   Hydrodynamic Separators: Due to site constraints, the existing grade of Fowler Lane, and high  groundwater, designing a storage facility above the groundwater table was not feasible for the western  half of Fowler or the western end of Apex Drive. Instead, runoff from this area will flow to inlets located  at the intersection of the two roads and on to 2 hydrodynamic separators (HDS) which will discharge to  the proposed Fowler trunk main. The HDS will be further detailed during infrastructure review but have  been preliminarily sized to provide 100% trash removal and oil removal and 80% TSS removal for the  Runoff Treatment Flow Rate from these streets. The Runoff Treatment Flow Rate was calculated using the  guidelines outlined in Section 3.3 of the Montana Post Construction Stormwater BMP Design Guidance  Manual. These calculations can be found in Appendix C on the sheets for Hydrodynamic Separator‐1 and  2. These off‐site flows are summarized in Table 1 below.   FOWLER LANE STORMWATER TRUNK MAIN  In discussion with City Engineering Department staff, it was determined that the city intends to create a  storm water trunk main along the east side of Fowler Lane to direct runoff from the Fowler Lane right‐of‐ way north to a future regional stormwater facility. Part of the reason for this trunk main is that the large  irrigation ditch along the west side of Fowler Lane will make it difficult for stormwater from the western  half of the street right‐of‐way to be conveyed across the ditch to storage facilities in the future.   The Buffalo Run project south of the project site initiated this trunk main with the installation of an 18”  dia. storm pipe in the eastern boulevard of Fowler Lane across their project frontage. According to the  design report for that project, the 18” pipe was sized to accommodate runoff from the future 100’ Fowler  Lane ROW (62’ TBC to TBC) from Blackwood Road to the north end of their project site (approximately  Kurk Drive). The Buffalo Run design placed the trunk main under the future curb line for Fowler will be  when it is widened to a 62’ wide street. The project provided interim storm ponds in the Fowler boulevard  for the eastern half of the 38’ street section and provided a hydrodynamic separator (HDS) on the trunk  main to treat runoff from the west half of the street section. This HDS was sized to treat the stormwater  quality volume for future 62’ buildout condition of Fowler Lane.   The portion of the trunk main to be installed across the Range 5 project frontage is sized to accommodate  the entire drainage area proposed to contribute to the Buffalo Run trunk main (100’ of ROW from  Blackwood to Kurk) as well as the western half of the Fowler ROW from Kurk Drive to approximately Apex    Range 5 Apartments ‐ Stormwater Design Report  Page 5  January 2024  Drive (50’ of ROW). The east half of the Fowler ROW from Kurk Drive to Apex Drive is expected to be  treated on‐site by the respective property owners. The eastern portion of the Fowler ROW across the  Range 5 frontage will be conveyed to a retention pond via a storm chase.   The proposed trunk main across the Range 5 frontage is proposed to be shifted east of the location shown  in Buffalo Run to beneath the 10’ shared use path. The reason for this shift is that like Buffalo Run an HDS  will be needed beneath the future curb line for Fowler to treat the stormwater quality volume from the  west half of Fowler and a portion of the east half. However, unlike Buffalo Run, the drainage area flowing  through the trunk main at this location in Range 5 will produce too much flow to be treated by an HDS.  So, the HDS is proposed to be installed off‐line of the trunk main to treat Fowler runoff and then discharge  runoff into the trunk main. The HDS has been preliminary sized for this report with the help of Contech  and will be detailed and finalized with the infrastructure improvements submittal for this project.   The trunk main was sized based on the future 100’ ROW of Fowler Lane with a 62’ TBC to TBC street  section and 10’ shared use paths on either side. These assumptions produced a weighted C‐Value of 0.82  for the street section. The expected drainage area contributing to the trunk main at the north end of the  project site will be ~7.2 acres which includes the Fowler Lane ROW from Blackwood Road to Apex Drive,  and a small portion of Apex Drive. This 7.2‐acre drainage area is expected to produce a runoff flow rate of  13.80 CFS during the 25‐year design storm at a relatively conservative time of concentration of 10.73  minutes.   Since the final time of concentration and final drainage area for the full build‐out of the trunk main  upstream of the project site is currently unknown, the proposed trunk main will be upsized to account for  potential additional future flows. Most of the proposed trunk main will be constructed of 21” PVC pipe,  which will provide 26.40 CFS conveyance capacity when flowing 75% full at the average 1.60% slope. To  daylight the trunk main into the borrow ditch on the east side of Fowler Lane, the pipe will have very little  cover as it crosses beneath Apex Drive. Therefore, the segment of the trunk main crossing Apex will be  constructed of 30” equivalent RCP arch pipe laid at 0.5% slope. This portion of pipe will provide 23.75 CFS  conveyance capacity. North of Apex Drive there will be two additional sections of 21” pipe to temporarily  convey runoff northwest to the roadside borrow ditch. These sections of pipe are proposed to be 21” PVC  laid at 0.50%, which will provide a conveyance capacity of 17.41 CFS. It is expected that in the future when  this trunk main is continued north, these pipes would be removed and the trunk main would be able to  continue to be laid at 1.6% from STMH T‐4.    OFF‐SITE FLOW   The northernmost portion of Fowler Lane at the Apex Drive intersection is the lowest point on the project  site, and runoff from this area is therefore unable to be conveyed to an on‐site storage facility. This small,  0.18‐acre area will continue the existing drainage pattern for the Fowler Lane section and will flow north  into the roadside ditches on either side of the street, generating an estimated 0.51 cfs runoff rate during  the 25‐year storm event. Runoff from this drainage basin will combine with the runoff from the two HDS  in Fowler and Apex to create a total off‐site runoff rate of 3.65 cfs, only 0.51 cfs of which will be untreated.   Except for a small portion of the western half of Fowler, all this proposed off‐site flow will be discharged  into the eastern borrow ditch along Fowler Lane. For comparison purposes, the pre‐development runoff  rate onto the property to the north of the project site was 4.88 cfs, none of which was treated.  The Below  table compares the pre‐development and post development off‐site runoff values.     Range 5 Apartments ‐ Stormwater Design Report  Page 6  January 2024  Table 1: Off‐Site Flow (Pre vs Post‐Development)  Drainage Basin Area (Ac.) C‐Value Tc (25‐yr) (min.) Peak Flow (cfs) Treatment  Type  Pre‐Development 20.52 0.21 34.44 4.88 None  Post‐Development           (DB 1, DB Off‐Site) 1.24 Varies (~0.80) Varies (5.4 avg.) 3.65 HDS, None    DRAINAGE BASIN SUMMARY  The development has been broken into multiple drainage basins that correspond to the  retention/detention facilities that runoff generated by areas flows to. Basins were given C‐factors based  on the land cover type per the COB DSSP. C‐values for the proposed roads sections are included in  Appendix C. As explained previously, for the purpose of this report, inlet and pipe sizing for the road  improvements have been preliminarily calculated but are not included in this report. This information will  be provided with infrastructure review and approval through the City of Bozeman Engineering  Department.     Table 2: Hydrodynamic Separator Facilities Summary  Drainage Basin  Area (Ac.) C‐Value Treatment Flow  Rate (cfs) Facility Name  1 (1A, 1B) 0.76 0.82 0.47 HDS 1  1 (1C, 1D) 0.30 0.76 0.17 HDS 2    Table 3: Retention Facilities Summary  Drainage Basin  Area (Ac.) C‐Value Volume  Required (ft3)  Volume  Provided (ft3)  Facility  Name  2 1.94 0.67 3,820 4,640 Pond 2  7 2.33 0.68 4,686 5,575 Pond 7  8 2.45 0.65 4,713 4,995 Pond 8  9 0.09 0.95 246 297 Pond 9  10 0.09 0.76 201 215 Pond 10  11 1.55 0.79 3,632 4,350 Pond 11                          Range 5 Apartments ‐ Stormwater Design Report  Page 7  January 2024  Table 4: Detention Facilities Summary  Drainage Basin  Area (Ac.) C‐Value Volume  Required (ft3)  Volume  Provided (ft3) Facility Name  3 0.34 0.73 383 605 Stormtech System 3  4 0.64 0.76 843 940 Stormtech System 4  5 0.43 0.76 520 712 Stormtech System 5  6 0.36 0.76 444 606 Stormtech System 6  12 1.09 0.83 1,618 1,703 Stormtech System 12  13 0.60 0.88 912 1,000 Stormtech System 13  14 1.39 0.78 1,928 2,043 Stormtech System 14  15 1.02 0.77 1,423 1,427 Stormtech System 15  16 1.74 0.78 2,423 2,527 Stormtech System 16  17 0.77 0.81 1,103 1,187 Stormtech System 17  18 0.73 0.78 1,003 1,082 Stormtech System 18  19 0.90 0.81 1,290 1,402 Stormtech System 19    Appendix A  Geotechnical Investigation Report – IMEG – June 30, 2023                                      June 30, 2023 2B Holdings, LLC Attn: Ben Nistler E-mail: ben@nhbmt.biz RE: Geotechnical Investigation Report 4840 Fowler Lane Gallatin County, Montana IMEG# 23001313.01 Dear Ben, Per your request, IMEG has conducted a subsurface soils investigation for the above referenced property located in the Northwest Quarter of Section 23, Township 2 South, Range 5 East in Gallatin County Montana. The scope of services was to conduct a subsurface soils investigation and provide a soils investigation report for residential structures. The report documents the subsurface conditions, soil properties, and provides foundation design and general earthwork recommendations. Proposed Construction It is understood that residential structures are proposed for construction. It has been assumed the structures will be constructed with slab on grade with stem wall foundations and will utilize typical wood framing. In determining the allowable bearing capacity and settlement estimates, it has been assumed that the foundation footings will not be subjected to unusual loading conditions such as eccentric loads. A footing is eccentrically loaded if the load transferred to the footing is not directed through the center of the footing. This creates a bending moment in the footing and results in a non-uniform load transfer to the underlying soil. If any of the foundation footings will be eccentrically loaded, please contact this office so we can appropriately revise our allowable bearing capacity and settlement estimates. Site Description The subject property has a total area of 20.518 acres and access is provided by Fowler Lane. The subject property is relatively flat and is bordered by residential lots to the north, south, and east, and Fowler Lane to the west. No other significant topographical or geological features were observed in the direct vicinity of the desired building sites. 2B Holdings, LLC – Geotechnical Investigation – 4840 Fowler Lane, Bozeman MT June 30, 2023 Page 2 of 12 Subsurface Soil and Conditions On March 8, 2023 a member of the staff of IMEG visited the site to conduct a subsurface soils investigation. The subsurface soils investigation consisted of examining eight exploratory test pit excavations. The exploratory test pits were excavated with a Bobcat E88 tracked excavator. The locations of the exploratory test pits were determined based on the location of the location of underground utilities. The soil profiles revealed by the exploratory excavations were logged and visually classified according to ASTM D 2488, which utilizes the nomenclature of the Unified Soil Classification System (USCS). The relative density of each soil layer was estimated based on probing of the excavation sidewalls with a rock hammer and the overall stability of the excavations. Any evidence of seepage or other groundwater conditions were also noted. The location of the exploratory test pits are shown on the included Test Pit Location Map. The following paragraphs briefly summarize the subsurface soils and conditions observed in the exploratory test pits excavated for the field investigation. The soil horizons are described as they were encountered in the test pit excavations, starting with the horizon nearest the surface and proceeding with each additional horizon encountered with depth. Please refer to the attached test pit logs for more detailed information. The first soil horizon encountered in each exploratory excavation was a Silty Clay Organics. This material was black in color, moist and soft in consistency. This material was encountered to depths varying from approximately 1.0 feet to 1.5 feet below grounds surface (bgs) in the exploratory excavations. Organic soils are highly compressible and are not suitable for foundation support. This material must be removed from beneath all foundation elements and in any area that will receive asphalt and/or concrete pavements. Underlying the Silty Clay Organics in exploratory excavations 2, 3, 4, and 6 was a Sandy Lean Clay with Gravel (CL). This material was encountered to depths varying from approximately 1.67 feet to 4.0 feet. This material was light brown to brown in color, soft to medium stiff in consistency and moist. Underlying the Silty Clay Organics in exploratory excavations 1,5,7, and 8 was a Clayey Gravel with Sand, Cobbles, and Boulders (GC). This material was encountered to depths varying from approximately 2.0 feet to 2.5 feet. This material was brown in color, medium dense in consistency and moist. Underlying the Sandy Lean Clay and Clayey Gravel in each exploratory excavation was a Poorly Graded Gravel with Sand and Cobbles (GP). This material was present to the end of each excavation at depths varying from approximately 5.3 feet to 8.3 feet bgs. This material was grayish brown to brown in color, medium dense in consistency and moist to wet. It should be noted that groundwater was encountered at the end of each exploratory excavation. Based on the subsurface investigation, it is recommended that the loads from the proposed structures be transmitted to the Poorly Graded Gravel with Sand and Cobbles or to a structural fill pad overlying this material. 2B Holdings, LLC – Geotechnical Investigation – 4840 Fowler Lane, Bozeman MT June 30, 2023 Page 3 of 12 Groundwater Groundwater was encountered at the bottom of each of the exploratory excavations. Groundwater monitoring performed by IMEG began on April 28, 2023 and is currently ongoing. To date the seasonally high groundwater elevation across the subject property has varied from 0.04 feet bgs to 2.85 feet bgs. The highest groundwater levels were found near the north and eastern property boundaries. Given the shallow depth to groundwater across the site, basement and crawl space foundations are not feasible. Slab-on-grade with stem wall foundations may be utilized anywhere within the subdivision. Seismicity The Bozeman area is located in an earthquake zone known as the intermountain seismic belt, which is a zone of earthquake activity that extends from northwest Montana to southern Arizona. In general, this zone is expected to experience moderately frequent, potentially damaging earthquakes. With that in mind, it is important that the structure be designed to withstand horizontal seismic accelerations that may be induced by such an earthquake, as is required by the International Building Code. The USGS provides seismic design parameters for the design of buildings and bridges across the United States. These parameters are based on the 2015 National Earthquake Hazards Reduction Program (NEHRP) Recommended Seismic Provisions. The primary intent of the NEHRP Recommended Seismic Provisions is to prevent, for typical buildings and structures, serious injury and life loss caused by damage from earthquake ground shaking. The following seismic design parameters were determined for the subject property using the USGS Seismic Design Application: Approximate site Location: Latitude = 45.6540° N Longitude = 111.0815° W Maximum Considered Earthquake (MCE) Spectral Response Acceleration Parameters: Short Period (SS) = 0.690g 1-Second Period (S1) = 0.217g Site Coefficients and Adjusted MCE Spectral Response Acceleration Parameters: SMS = 0.690g SM1 = 0.470g Design Spectral Response Acceleration Parameters: SDS = 0.574g SD1 = 0.313g 2B Holdings, LLC – Geotechnical Investigation – 4840 Fowler Lane, Bozeman MT June 30, 2023 Page 4 of 12 The seismic site class for this project is D. Liquefaction In general terms, liquefaction is defined as the condition when saturated, loose, fine sand-type soils lose their support capabilities due to the development of excessive pore water pressure, which can develop during a seismic event. Loose silty sandy soils, if located below the groundwater table, have the potential to liquefy during a major seismic event. Our subsurface investigation did not encounter any loose sand or silt horizons within the depth of excavation that will be located within the water table, and it is our opinion that the potential for differential settlement resulting from liquefaction during a moderate seismic event is low. Foundation Recommendations Based on the subsurface soils encountered in the exploratory excavations, it is recommended that each structure utilize a slab-on-grade with stem wall foundation. Please find the following as general recommendations for all foundation elements: • In order to keep the footing out of the active frost zone it is recommended that the bottom of all footing elevations be a minimum of 48 inches below finished grade. • All foundation footings are to bear on Poorly Graded Gravel with Sand and Cobbles or on properly placed and compacted structural fill overlying this material. All foundation footings shall be dimensioned for an allowable bearing capacity of 2,500 pounds per square foot (psf). • It is recommended that typical strip footings for this structure have a minimum width of 16 inches and column footings should have a minimum width of 24 inches, provided the soils allowable bearing capacity is not exceeded. • The foundation subgrade must remain in a dry condition throughout construction of the foundation elements. • If construction takes place during the colder months of the year, the subgrade must be protected from freezing. This may require the use of insulating blankets and/or ground heaters. Allowable Bearing Capacity The bearing capacity of a soil is defined as the ultimate pressure per unit area by the foundation that can be supported by the soil in excess of the pressure caused by the surrounding soil at the footing level. Bearing capacity is determined by the physical and chemical properties of the soil located beneath the proposed structures footings. 2B Holdings, LLC – Geotechnical Investigation – 4840 Fowler Lane, Bozeman MT June 30, 2023 Page 5 of 12 It is recommended that the loads from the proposed structures be transmitted to the Poorly Graded Gravel with Sand and Cobbles or to a structural fill pad overlying this material. For this scenario it is recommended that an allowable bearing capacity of 2,500 pounds per square foot be used to dimension all foundation footings. Settlement While the soil at the site may be able to physically support the footings, it is also important to analyze the possible settlement of the structure. In many cases, settlement determines the allowable bearing capacity. When a soil deposit is loaded by a structure, deformations within the soil deposit will occur. The total vertical deformation of the soil at the surface is called total settlement. Total settlement is made up of two components: elastic settlement and consolidation settlement. Elastic settlement is the result of soil particles rearranging themselves into a denser configuration due to a load being imposed on them and usually occurs during the construction process and shortly after. Consolidation settlement occurs more slowly and over time as water within the pore spaces of a soil are forced out and the soil compresses as the stress from the load is transferred from the water molecules to the soil particles. Consolidation settlement is more of a concern with fine-grained soils with low permeability and high in-situ moisture contents. The degree of settlement is a function of the type of bearing material, the bearing pressure of the foundation elements, local groundwater conditions, and in some cases determines the allowable bearing capacity for a structures’ footings. In addition to analyzing total settlement, the potential for differential settlement must also be considered. Differential settlement occurs in soils that are not homogeneous over the length of the foundation or in situations where the foundation rests on cut and fill surfaces. If the foundation rests on structural fill overlaying properly prepared soils with rock, differential settlement is expected to be well within tolerable limits. Areas that have significantly more fill under the foundation footings (four feet of more) create greater potential for differential settlement. In these cases, the structural fill must be installed properly and tested frequently. Compaction efforts and structural fill consistence are vital in minimizing differential settlement. For this project it is not anticipated that significant quantities of structural fill will be required. For this project, total settlement is expected to consist of elastic settlement. A settlement analysis based on conservative soil parameter estimates, the recommended allowable bearing capacity, and the assumption that all recommendations made in this report are properly adhered to, indicates the total and differential settlement are expected to be ¾-inch or less. Structures of the type assumed can generally tolerate this amount of movement, however, these values should be checked by a structural engineer to verify that they are acceptable. Please note that the settlement estimates are based on loads originating from the proposed structures. If additional loads are introduced, such as the placement of large quantities of fill, our office should be contacted to re-evaluate the settlement estimates. 2B Holdings, LLC – Geotechnical Investigation – 4840 Fowler Lane, Bozeman MT June 30, 2023 Page 6 of 12 Lateral Pressures Lateral pressures imposed upon foundation and retaining walls due to wind, seismic forces, and earth pressures may be resisted by the development of passive earth pressures and/or frictional resistance between the base of the footings and the supporting soils. If a foundation or retaining wall is restrained from moving, the lateral earth pressure exerted on the wall is called the at-rest earth pressure. If a foundation or retaining wall is allowed to tilt away from the retained soil, the lateral earth pressure exerted on the wall is called the active earth pressure. Passive earth pressure is the resistance pressure the foundation or retaining wall develops due to the wall being pushed laterally into the earth on the opposite side of the retained soil. Each of these pressures is proportional to the distance below the earth surface, the unit weight of the soil, and the shear strength properties of the soil. It is recommended that all foundation and retaining walls be backfilled with well-draining granular material. Well-draining granular backfill has a more predictable behavior in terms of the lateral earth pressure exerted on the foundation or retaining wall and will not generate expansive related forces. If backfill containing significant quantities of clayey material is used, the seepage of water into the backfill could potentially generate horizontal swelling pressures well above at-rest values. Additionally, seepage into a clayey backfill material will also cause significant hydrostatic pressures to build up against the foundation wall due to the low permeability of clay soils and will make the backfill susceptible to frost action. Subsurface walls that are restrained from moving at the top are recommended to be designed for an equivalent fluid pressure of 62 pounds per cubic foot (pcf) (at-rest pressure); the equivalent fluid pressure is the product of the retained soils unit weight and its coefficient of active or at-rest earth pressure. Any subsurface walls that are allowed to move away from the restrained soil, such as cantilevered retaining walls, are recommended to be designed for an equivalent fluid pressure of 45 pcf (active pressure). For passive pressures, an equivalent fluid pressure of 270 pcf is recommended, and the coefficient of friction between the cast-in-place concrete and the Clayey Gravel with Sand, Cobbles, and Boulders and/or the Sandy Lean Clay with Gravel is 0.3. These recommended values were calculated assuming a near horizontal backfill and that the on-site soils, with the exception of the organics, will be used as foundation wall backfill. It is also assumed that the backfill will be compacted as recommended in this report. Also, please note that these design pressures do not include a factor of safety and are for static conditions, they do not account for additional forces that may be induced by seismic loading. Subgrade Preparation and Structural Fill In general, the excavation for the foundation must be level and uniform and continue down to the Poorly Graded Gravel with Sand and Cobbles. If any soft spots, saturated soils, or boulders are encountered, they will need to be removed and backfilled with structural fill. The excavation width must extend a minimum of one footing width from the outer edges of the footings or half the height of the required structural fill, whichever is greater. For example, if 6 feet of structural fill is required, the width of the excavation must 2B Holdings, LLC – Geotechnical Investigation – 4840 Fowler Lane, Bozeman MT June 30, 2023 Page 7 of 12 extend out a distance of 3 feet on either side of the foundation footings. Prior to placing any required structural fill, it is recommended that the native subgrade be compacted to an unyielding condition. Structural fill is defined as all fill that will ultimately be subjected to structural loadings, such as those imposed by footings, floor slabs, pavements, etc. None of the soils encountered in the exploratory excavations are suitable for use as structural fill. Structural fill will need to be imported where it is required. Imported structural fill is recommended to be a well graded gravel with sand that contains less than 15 percent of material that will pass a No. 200 sieve and that has a maximum particle size of 3 inches. Also, the fraction of material passing the No. 40 sieve shall have a liquid limit not exceeding 25 and a plasticity index not exceeding 6. Additionally, the structural fill shall consist of durable materials that will not degrade due to moisture or the compaction effort, i.e. no shale or mudstone rock fragments should be present. It would also be acceptable to utilize a ¾-inch crushed washed rock as structural fill. Structural fill must be placed in lifts no greater than 12-inches (uncompacted thickness) and be uniformly compacted to a minimum of 97 percent of its maximum dry density, as determined by ASTM D698. Typically, the structural fill must be moisture conditioned to within + 2 percent of the materials optimum moisture content to achieve the required density. ¾-inch crushed washed rock is recommended to be compacted to an unyielding condition. It is recommended that the structural fill be compacted with a large vibrating smooth drum roller. Please note that if a moisture-density relationship test (commonly referred to as a proctor) needs to be performed for a proposed structural fill material to determine its maximum dry density in accordance with ASTM D698, a sample of the material must be delivered to this office a minimum of three full working days prior to density testing being needed. At no time should surface water runoff be allowed to flow into and accumulate within the excavation for the foundation elements. If necessary, a swale or berm should be temporarily constructed to reroute all surface water runoff away from the excavation. Excavation should not proceed during large precipitation events. If any of the foundation footings are found to be located on a test pit, the area will need to be excavated down to the full depth of the test pit and structural fill be placed and compacted in controlled lifts as described in this report to bring the area back up to the desired grade. Foundation Wall Backfill Approved backfill material should be placed and compacted between the foundation wall and the edge of the excavation. Structural fill is recommended as foundation wall backfill in all areas that will support concrete slabs-on-grade or asphalt paving improvements. The on-site soils with the exception of the organics encountered during the field investigation are suitable for reuse as foundation wall backfill along the exterior of the foundation where asphalt and concrete pavements will not be located, provided it is not too moist and any cobbles larger than 6 inches in size are removed. The organic soil shall not be used as foundation wall backfill. 2B Holdings, LLC – Geotechnical Investigation – 4840 Fowler Lane, Bozeman MT June 30, 2023 Page 8 of 12 The foundation wall backfill shall be placed in uniform lifts and be compacted to a minimum of 95 percent of the material’s maximum dry density, as determined by ASTM D698. The foundation wall backfill will need to be compacted with either walk behind compaction equipment or hand operated compaction equipment in order to avoid damaging the foundation walls. If walk behind compaction equipment is used lifts should not exceed 8-inches (loose thickness) and if hand operated compaction equipment is used lifts should not exceed 4-inches (loose thickness). Interior Slabs-on-Grade For any interior slabs-on-grade, it is recommended that, at a minimum, the organic soil be removed. The native subgrade then needs to be compacted to a minimum of 95 percent of its maximum dry density, as determined by ASTM D698. Following compaction of the native subgrade, structural fill be placed and compacted to within 6-inches of the desired bottom of slab elevation. For all interior concrete slabs-on-grade, preventative measures must be taken to stop moisture from migrating upwards through the slab. Moisture that migrates upwards through the concrete slab can damage floor coverings such as carpet, hardwood and vinyl, in addition to causing musty odors and mildew growth. Moisture barriers will need to be installed to prevent water vapor migration and capillary rise through the concrete slab. Capillarity is the result of the liquid property known as surface tension, which arises from an imbalance of cohesive and adhesive forces near the interface between different materials. With regards to soils, surface tension arises at the interface between groundwater and the mineral grains and air of a soil. The height of capillary rise within a given soil is controlled by the size of the pores between the soil particles and not the size of the soil particles directly. Soils that have small pore spaces experience a higher magnitude of capillary rise than soils with large pore spaces. Typically, soils composed of smaller particles (such as silt and clay) have smaller pore spaces. In order to prevent capillary rise through the concrete slab-on-grade it is recommended that 6 inches of ¾- inch washed rock (containing less than 10 percent fines) be placed and compacted once the excavation for the slab is complete. The washed rock has large pore spaces between soil particles and will act as a capillary break, preventing groundwater from migrating upwards towards the bottom of the slab. Water vapor is currently understood to act in accordance with the observed physical laws of gases, which state that the water vapor will travel from an area of higher concentration to that of a lower concentration until equilibrium is achieved. Because Earth contains large quantities of liquid water, water vapor is ubiquitous in Earth’s atmosphere, and, as a result, also in soils located above the water table (referred to as the vadose zone). Typically, the concentration of water vapor in the vadose zone is greater than that inside the residence. This concentration difference may result in an upward migration of water vapor from the vadose zone through the concrete slab-on-grade and into the building. In order to prevent this upward migration of water vapor through the slab, it is recommended that a 15-mil extruded polyolefin plastic that complies with ASTM E1745 (such as a Stego Wrap 15-mil Vapor Barrier) 2B Holdings, LLC – Geotechnical Investigation – 4840 Fowler Lane, Bozeman MT June 30, 2023 Page 9 of 12 be installed. The vapor barrier should be pulled up at the sides and secured to the foundation wall or footing. Care must be taken during and after the installation of the vapor barrier to avoid puncturing the material, and all joints are to be sealed per the manufacture’s recommendations. Once the excavation for any interior slabs-on-grade is completed as described in the first paragraph of this section, and the ¾ inch washed rock and moisture barriers have been properly installed, it will be acceptable to form and cast the steel reinforced concrete slab. It is recommended that interior concrete slabs-on-grade have a minimum thickness of 4 inches, provide all slab reinforcement is designed by a licensed structural engineer. Exterior Slabs-on-Grade For exterior areas to be paved with concrete slabs such as sidewalks and/or patios, it is recommended that, at a minimum, the organic soil be removed. The subgrade then needs to be compacted to a minimum of 95 percent of its maximum dry density, as determined by ASTM D698. Then for non-vehicular traffic areas, a minimum of 6 inches of ¾-inch minus rock needs to be placed, and 4 inches of 4000 pounds per square inch (psi) concrete placed over the ¾-inch minus rock. For areas with vehicular traffic, a minimum of 9 inches of ¾-inch minus rock should be placed, followed by 6 inches of 4000 psi concrete. Exterior slabs that will be located adjacent to the foundation walls need to slope away from the structure at a minimum grade of 2 percent and should not be physically connected to the foundation walls. If they are connected, any movement of the exterior slab will be transmitted to the foundation wall, which may result in damage to the structure. Site Grading Surface water should not be allowed to accumulate and infiltrate the soil near the foundation. Proper site grading will ensure surface water runoff is directed away from the foundation elements and will aid in the mitigation of excessive settlement. If the soils beneath the house are allowed to experience an increase in moisture content, additional settlement of the structures may occur. Please find the following as general site grading recommendations: • Finished grade must slope away from the building a minimum of 5 percent within the first 10 feet, in order to quickly drain ground surface and roof runoff away from the foundation walls. Please note that in order to maintain this slope; it is imperative that any backfill placed against the foundation walls be compacted properly. If the backfill is not compacted properly, it will settle and positive drainage away from the structure will not be maintained. • Permanent sprinkler heads for lawn care should be located a sufficient distance from the structure to prevent water from draining toward the foundation or saturating the soils adjacent to the foundation. 2B Holdings, LLC – Geotechnical Investigation – 4840 Fowler Lane, Bozeman MT June 30, 2023 Page 10 of 12 • Rain gutter down spouts are to be placed in such a manner that surface water runoff drains away from the structure. • All roads, walkways, and architectural land features must properly drain away from all structures. Special attention should be made during the design of these features to not create any drainage obstructions that may direct water towards or trap water near the foundation. Asphalt Paving Improvements For areas to be paved with asphalt, it is recommended that, as a minimum, the organic soil be removed. The native subgrade then needs to be compacted at ± 2 percent of its optimum moisture content to 95 percent of its maximum dry density. Following compaction of the native subgrade, a layer of geotextile (such as Mirafi 160N) shall be installed. Next a 12-inch layer of compacted 6-inch minus gravel can be placed. Next by a 6-inch layer of compacted 1-inch minus road mix shall be installed. Both gravel courses must be compacted at ± 2 percent of their optimum moisture content to 95 percent of their maximum dry density. A 3-inch-thick layer of asphalt pavement can then be placed and compacted over this cross- section. If asphalt paving is to be placed on foundation wall backfill, the backfill must be compacted to 95 percent of its maximum dry density, as determined by ASTM D698. It is recommended the backfill be placed in uniform lifts and be compacted to an unyielding condition. Underground Utilities We recommend specifying non-corrosive materials or providing corrosion protection unless additional tests are performed to verify the onsite soils are not corrosive. It is recommended that ¾-inch minus gravel be used as a bedding material, where bedding material is defined as all material located within 6 inches of the utility pipe(s). The bedding material should be thoroughly compacted around all utility pipes. Trench backfill shall be compacted to a minimum of 95 percent of its maximum dry density in paved or landscaped areas and a minimum of 97 percent of its maximum dry density beneath foundation footings. Backfilling around and above utilities shall meet the requirements of Montana Public Works Standard Specifications. Construction Administration The foundation is a vital element of a structure; it transfers all of the structure’s dead and live loads to the native soil. It is imperative that the recommendations made in this report are properly adhered to. A representative from IMEG should observe the construction of any foundation or drainage elements recommended in this report. The recommendations made in this report are contingent upon our involvement. If the soils encountered during the excavation differ than those described in this report or any unusual conditions are encountered, our office should be contacted immediately to examine the conditions, re-evaluate our recommendations and provide a written response. 2B Holdings, LLC – Geotechnical Investigation – 4840 Fowler Lane, Bozeman MT June 30, 2023 Page 11 of 12 If construction and site grading take place during cold weather, it is recommended that appropriate winter construction practices be observed. All snow and ice shall be removed from cut and fill areas prior to site grading taking place. No fill should be placed on soils that are frozen or contain frozen material. No frozen soils can be used as fill under any circumstances. Additionally, Concrete should not be placed on frozen soils and should meet the temperature requirements of ASTM C 94. Any concrete placed during cold weather conditions shall be protected from freezing until the necessary compressive strength has been attained. Once the footings are placed, frost shall not be permitted to extend below the foundation footings, as this could heave and crack the foundation footings and/or foundation walls. It is the responsibility of the contractor to provide a safe working environment with regards to excavations on the site. All excavations should be sloped or shored in the interest of safety and in accordance with local and federal regulations, including the excavation and trench safety standards provided by the Occupational Safety and Health Administration (OSHA). Report Limitations and Guidelines for Use This report was prepared to be used exclusively by 2B Holdings, LLC for residential improvements to be constructed at 4840 Fowler Lane, located in the Northwest Quarter of Section 23, Township 2 South, Range 5 East in Bozeman, Montana. All of the work was performed in accordance with generally accepted principles and practices used by geotechnical engineers and geologists practicing in this or similar localities. This report should not be used by anyone it was not prepared for, or for uses it was not intended for. Field investigations and preparation of this report was conducted in accordance with a specific set of requirements set out by the client, which may not satisfy the requirements of others. This report should not be used for nearby sites or for structures on the same site that differ from the structures that were proposed at the time this report was prepared. Any changes in the structures (type, orientation, size, elevation, etc.) proposed for this site must be discussed with our company for this report to be valid. The recommendations made in this report are based upon data obtained from test pits excavated at the locations indicated on the attached Test Pit Location Map. It is not uncommon that variations will occur between these locations, the nature and extent of which will not become evident until additional exploration or construction is conducted. These variations may result in additional construction costs, and it is suggested that a contingency be provided for this purpose. If the soils encountered during the excavation differ than those described in this report or any unusual conditions are encountered, our office should be contacted immediately to examine the conditions and re-evaluate our recommendations and provide a written response. This report is valid as a complete document only. No portion of this report should be transmitted to other parties as an incomplete document. Misinterpretation of portions of this report (i.e. test pit logs) is possible when this information is transmitted to others without the supporting information presented in other portions of the report. OL GC GP 1.5 2.5 8.3 0 TO 1.5 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; low plasticity; very soft. 1.5 TO 2.5 FEET: CLAYEY GRAVEL WITH SAND, COBBLES AND BOULDERS; (GC); dark brown to brown; moist; medium plasticity; medium dense; approximately 40 percentsubangular gravels; approximately 25 percent fine to coarse grain sand; approximately 35 percent clayey fines. 2.5 TO 8.3 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); dark brown to brown; moist; medium dense; approximately 50 percent subangular gravels; approximately 40 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 8.3 feet. NOTES MW-1 GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Bobcat E88 EXCAVATION CONTRACTOR Elevation Excavating LLC GROUND WATER LEVELS: DATE STARTED 3/8/23 COMPLETED 3/8/23 AT TIME OF EXCAVATION 8.30 ft AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 7.5 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 1 PROJECT NUMBER 23001313 CLIENT 2B Holdings LLC PROJECT LOCATION 4840 Fowler Lane, Bozeman MT PROJECT NAME MW Wells & TP Logs GENERAL BH / TP / WELL - GINT STD US.GDT - 6/29/23 13:52 - \\FILES\ACTIVE\PROJECTS\2023\23001313.01\DESIGN\_REFERENCE\GEOTECHNICALREPORT\TP LOGS & MAP\TEST PIT LOGS (23001313).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL CL GP 1.0 1.7 8.3 0 TO 1 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; low plasticity; very soft. 1 TO 1.667 FEET: SANDY LEAN CLAY WITH GRAVEL; (CL); light brown to brown; moist;medium plasticity; medium stiff; approximately 10 percent subangular gravels; approximately 30 percent fine to coarse grain sand; approximately 60 percent clayey fines. 1.667 TO 8.3 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); dark brown to brown; moist; medium dense; approximately 50 percent subangular gravels; approximately 40 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 8.3 feet. NOTES MW-2 GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Bobcat E88 EXCAVATION CONTRACTOR Elevation Excavating LLC GROUND WATER LEVELS: DATE STARTED 3/8/23 COMPLETED 3/8/23 AT TIME OF EXCAVATION 8.30 ft AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 7.5 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 2 PROJECT NUMBER 23001313 CLIENT 2B Holdings LLC PROJECT LOCATION 4840 Fowler Lane, Bozeman MT PROJECT NAME MW Wells & TP Logs GENERAL BH / TP / WELL - GINT STD US.GDT - 6/29/23 13:52 - \\FILES\ACTIVE\PROJECTS\2023\23001313.01\DESIGN\_REFERENCE\GEOTECHNICALREPORT\TP LOGS & MAP\TEST PIT LOGS (23001313).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL CL GP 1.0 2.5 7.0 0 TO 1 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; low plasticity; very soft. 1 TO 2.5 FEET: SANDY LEAN CLAY WITH GRAVEL; (CL); light brown to brown; moist;medium plasticity; medium stiff; approximately 10 percent subangular gravels; approximately 30 percent fine to coarse grain sand; approximately 60 percent clayey fines. 2.5 TO 7 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); dark brown to brown; moist; medium dense; approximately 50 percent subangular gravels; approximately 40 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.0 feet. NOTES MW-3 GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Bobcat E88 EXCAVATION CONTRACTOR Elevation Excavating LLC GROUND WATER LEVELS: DATE STARTED 3/8/23 COMPLETED 3/8/23 AT TIME OF EXCAVATION 7.00 ft AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 3 PROJECT NUMBER 23001313 CLIENT 2B Holdings LLC PROJECT LOCATION 4840 Fowler Lane, Bozeman MT PROJECT NAME MW Wells & TP Logs GENERAL BH / TP / WELL - GINT STD US.GDT - 6/29/23 13:52 - \\FILES\ACTIVE\PROJECTS\2023\23001313.01\DESIGN\_REFERENCE\GEOTECHNICALREPORT\TP LOGS & MAP\TEST PIT LOGS (23001313).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL CL GP 1.5 3.0 8.0 0 TO 1.5 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; low plasticity; very soft. 1.5 TO 3 FEET: SANDY LEAN CLAY WITH GRAVEL; (CL); light brown to brown; moist; medium plasticity; medium stiff; approximately 10 percent subangular gravels;approximately 30 percent fine to coarse grain sand; approximately 60 percent clayey fines. 3 TO 8 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); dark brown to brown; moist; medium dense; approximately 50 percent subangular gravels; approximately 40 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 8.0 feet. NOTES MW-4 GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Bobcat E88 EXCAVATION CONTRACTOR Elevation Excavating LLC GROUND WATER LEVELS: DATE STARTED 3/8/23 COMPLETED 3/8/23 AT TIME OF EXCAVATION 8.00 ft AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 7.5 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 4 PROJECT NUMBER 23001313 CLIENT 2B Holdings LLC PROJECT LOCATION 4840 Fowler Lane, Bozeman MT PROJECT NAME MW Wells & TP Logs GENERAL BH / TP / WELL - GINT STD US.GDT - 6/29/23 13:52 - \\FILES\ACTIVE\PROJECTS\2023\23001313.01\DESIGN\_REFERENCE\GEOTECHNICALREPORT\TP LOGS & MAP\TEST PIT LOGS (23001313).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL GC GP 1.3 2.0 5.3 0 TO 1.33 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; low plasticity; very soft. 1.33 TO 2 FEET: CLAYEY GRAVEL WITH SAND, COBBLES AND BOULDERS; (GC); dark brown to brown; moist; medium plasticity; medium dense; approximately 40 percent subangular gravels; approximately 25 percent fine to coarse grain sand; approximately 35 percent clayey fines. 2 TO 5.3 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); darkbrown to brown; moist; medium dense; approximately 50 percent subangular gravels;approximately 40 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 5.3 feet. NOTES MW-5 GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Bobcat E88 EXCAVATION CONTRACTOR Elevation Excavating LLC GROUND WATER LEVELS: DATE STARTED 3/8/23 COMPLETED 3/8/23 AT TIME OF EXCAVATION 5.30 ft AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 5 PROJECT NUMBER 23001313 CLIENT 2B Holdings LLC PROJECT LOCATION 4840 Fowler Lane, Bozeman MT PROJECT NAME MW Wells & TP Logs GENERAL BH / TP / WELL - GINT STD US.GDT - 6/29/23 13:52 - \\FILES\ACTIVE\PROJECTS\2023\23001313.01\DESIGN\_REFERENCE\GEOTECHNICALREPORT\TP LOGS & MAP\TEST PIT LOGS (23001313).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL CL GP 1.5 4.0 7.5 0 TO 1.5 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; low plasticity; very soft. 1.5 TO 4 FEET: SANDY LEAN CLAY WITH GRAVEL; (CL); light brown to brown; moist; medium plasticity; medium stiff; approximately 10 percent subangular gravels;approximately 30 percent fine to coarse grain sand; approximately 60 percent clayey fines. 4 TO 7.5 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); dark brown to brown; moist; medium dense; approximately 50 percent subangular gravels;approximately 40 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.5 feet. NOTES MW-6 GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Bobcat E88 EXCAVATION CONTRACTOR Elevation Excavating LLC GROUND WATER LEVELS: DATE STARTED 3/8/23 COMPLETED 3/8/23 AT TIME OF EXCAVATION 7.50 ft AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 7.5 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 6 PROJECT NUMBER 23001313 CLIENT 2B Holdings LLC PROJECT LOCATION 4840 Fowler Lane, Bozeman MT PROJECT NAME MW Wells & TP Logs GENERAL BH / TP / WELL - GINT STD US.GDT - 6/29/23 13:52 - \\FILES\ACTIVE\PROJECTS\2023\23001313.01\DESIGN\_REFERENCE\GEOTECHNICALREPORT\TP LOGS & MAP\TEST PIT LOGS (23001313).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL GC GP 1.0 2.3 7.8 0 TO 1 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; low plasticity; very soft. 1 TO 2.25 FEET: CLAYEY GRAVEL WITH SAND, COBBLES AND BOULDERS; (GC);dark brown to brown; moist; medium plasticity; medium dense; approximately 40 percent subangular gravels; approximately 25 percent fine to coarse grain sand; approximately 35 percent clayey fines. 2.25 TO 7.8 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); darkbrown to brown; moist; medium dense; approximately 50 percent subangular gravels; approximately 40 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.8 feet. NOTES MW-7 GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Bobcat E88 EXCAVATION CONTRACTOR Elevation Excavating LLC GROUND WATER LEVELS: DATE STARTED 3/8/23 COMPLETED 3/8/23 AT TIME OF EXCAVATION 7.80 ft AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 7.5 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 7 PROJECT NUMBER 23001313 CLIENT 2B Holdings LLC PROJECT LOCATION 4840 Fowler Lane, Bozeman MT PROJECT NAME MW Wells & TP Logs GENERAL BH / TP / WELL - GINT STD US.GDT - 6/29/23 13:52 - \\FILES\ACTIVE\PROJECTS\2023\23001313.01\DESIGN\_REFERENCE\GEOTECHNICALREPORT\TP LOGS & MAP\TEST PIT LOGS (23001313).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL GC GP 1.0 2.5 7.5 0 TO 1 FEET: SILTY CLAY ORGANIC SOIL; (OL); dark brown to black; moist; low plasticity; very soft. 1 TO 2.5 FEET: CLAYEY GRAVEL WITH SAND, COBBLES AND BOULDERS; (GC); darkbrown to brown; moist; medium plasticity; medium dense; approximately 40 percent subangular gravels; approximately 25 percent fine to coarse grain sand; approximately 35 percent clayey fines. 2.5 TO 7.5 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); dark brown to brown; moist; medium dense; approximately 50 percent subangular gravels; approximately 40 percent fine to coarse grain sand; approximately 10 percent clayey fines. Bottom of test pit at 7.5 feet. NOTES MW-8 GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Bobcat E88 EXCAVATION CONTRACTOR Elevation Excavating LLC GROUND WATER LEVELS: DATE STARTED 3/8/23 COMPLETED 3/8/23 AT TIME OF EXCAVATION 7.50 ft AFTER EXCAVATION --- AT END OF EXCAVATION ---DEPTH(ft)0.0 2.5 5.0 7.5 SAMPLE TYPENUMBERPAGE 1 OF 1 TEST PIT NUMBER TP 8 PROJECT NUMBER 23001313 CLIENT 2B Holdings LLC PROJECT LOCATION 4840 Fowler Lane, Bozeman MT PROJECT NAME MW Wells & TP Logs GENERAL BH / TP / WELL - GINT STD US.GDT - 6/29/23 13:52 - \\FILES\ACTIVE\PROJECTS\2023\23001313.01\DESIGN\_REFERENCE\GEOTECHNICALREPORT\TP LOGS & MAP\TEST PIT LOGS (23001313).GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION Appendix B  Drainage Basin Map                                      S S S UGTUGTUGTUGTUGTUGTUGTUGTUGTUGTUGTUGTUGTUGTUGTUGTUGTUGTUGTOHEOHEOHEOHEOHEOHEOHEOHEOHEOHEOHEOHEOHEOHEGASGASGASGASGASGASGASGASGASGASGASGASGASGASST ST FO W V ST STST STBLDG #336-PLEX BLDG #1 12-PLEX BLDG #2 12-PLEXBLDG #1012-PLEX BLDG #11 12-PLEX BLDG #912-PLEX BLDG #436-PLEX BLDG #5 36-PLEX BLDG #736-PLEX BLDG #636-PLEX BLDG #8 36-PLEX BLDG #12 36-PLEX W LANDING8''STLANDINGLANDING LANDINGUPUPUP UPUPUPUPUPUPUP STSTST FF4''W4''W6''SS6''SS4''W4''WFF4''SS F F2''W 6''SS FF4''SS F 4''SS 6''SS FF6''SS4''SSF4''SS F 6''SS FF4''W 6''SS OSW OSW OSW OSW OSW CO CO CO CO CO CO CO CO CO CO CO CO 21''ST21''ST21''ST21''ST21''ST21''ST21''ST21''ST21''ST21''ST21''ST21''STSTST ST ST ST ST 15''ST (43.81) DB 3 DB 4 DB 2 DB 8 DB 5 DB 7 DB 9DB 10 DB 12 DB 11 DB 17 DB 18 DB 15 DB 16 DB 13 DB 2 DB 14 DB 6 4945 49504946 4947 4948 4949 4951 4952 4953 49 5 0 49484 9 4 9 495 1 4952 4950 49514946 4950495149524946 4947 49454 9 4 6 4950 4951 4952 4953 4950 4951 49 5 2 4953 4950 4951 49534954494649474950 49 4 7 494 8 4 9 4 9 4951 4952 4945494 4 49 4 6 49474950 4948 4949 4951 4952 495049474948 4949 4951495049474948 4949 4951 4952 4945 494249434944 4946 4941494249434944494149424943 49454941494249434944494249434944 4941 4946 4947 4 9 5 0 49 4 9 4 9 5 1 4952495149524945 4945 49454950494649474948494949514952 4953 4953494549504944 4944 4944 49464947494849494951 495249454950494449464947494849494951 49524942494349414942 4943 4944 4944 4944 4945 4944 4952 4952 4952 49534953 49534953 4953 49544954 4953 BENNET BOULEVARD APEX DRIVE BUFFALO RUN AVENUEHOMESTEAD AVENUEFOWLER LANEDB 19A DB 19B DB 16A DB 16B DB 13B DB 13A 49504946 4947 49484949 3' CURB CHASE STORMTECH SYSTEM 3REQ. STORAGE: 383 CFPRO. STORAGE: 605 CF STORMTECH SYSTEM 17 REQ. STORAGE: 1,103 CFPRO. STORAGE: 1,187 CF STORMTECH SYSTEM 14REQ. STORAGE: 1,928 CFPRO. STORAGE: 2,043 CF STORMTECH SYSTEM 6REQ. STORAGE: 444 CF PRO. STORAGE: 606 CF STORMTECH SYSTEM 5REQ. STORAGE: 520 CFPRO. STORAGE: 712 CF STORMTECH SYSTEM 16REQ. STORAGE: 2,423 CFPRO. STORAGE: 2,527 CF STORMTECH SYSTEM 13REQ. STORAGE: 912 CFPRO. STORAGE: 1,000 CF STORMTECH SYSTEM 4REQ. STORAGE: 843 CF PRO. STORAGE: 940 CF POND 7REQ. STORAGE: 4,686 CFPRO. STORAGE: 5,575 CF POND 8REQ. STORAGE: 4,713 CFPRO. STORAGE: 4,995 CF POND 9REQ. STORAGE: 246 CFPRO. STORAGE: 297 CF POND 10 REQ. STORAGE: 201 CF PRO. STORAGE: 215 CF EX. DITCH ℄ EDGE OF DELINEATEDWETLAND STORMTECH SYSTEM 12REQ. STORAGE: 1,618 CF PRO. STORAGE: 1,703 CF DB 11 POND 2REQ. STORAGE: 3,820 CF PRO. STORAGE: 4,640 CF DB 19 DB 2A DB 2B DB 1BDB 1A DB 1 DB 1C DB 1D DB 11A DB 11B DB 7C DB 7 DB 7 DB 7A DB 7B DB 7B (44.69) (43.92) (45.19) (52.46) (53.91) (44.00) (47.22)(46.35) (50.13) (47.67) (53.88) -1.1% POND 11REQ. STORAGE: 3,632 CF PRO. STORAGE: 4,350 CF STORMTECH SYSTEM 19REQ. STORAGE: 1,290 CFPRO. STORAGE: 1,402 CF STORMTECH SYSTEM 18REQ. STORAGE: 1,003 CFPRO. STORAGE: 1,082 CF STORMTECH SYSTEM 15REQ. STORAGE: 1,423 CFPRO. STORAGE: 1,427 CF 2' CURB CHASE ST INLET 16-A ST MH 17 ST INLET 16-B ST MH 13 ST INLET 13-A ST INLET 13-B ST INLET 12 ST MH 15 ST MH 14 ST MH 18 ST INLET 19-B ST MH 12 ST INLET 19-A ST INLET 5-A ST INLET 5-B ST MH 5 ST INLET 3-B ST INLET 3-A ST INLET 4-A ST MH 3 ST INLET 4-B ST MH 4 ST INLET 6 ST MH 6 ST INLET 8-A ST INLET 7-A ST INLET 8-B ST INLET 7-B ST INLET 8-C ST INLET 8-D ST INLET 1-A ST INLET 1-B HDS 1 ST INLET 1-C HDS 2 STMH T-3 STMH T-4 STMH T-5 STMH T-2 STMH T-1 STMH 19 ST INLET 11-A 3' CURB CHASE DB PARK PROJECT NO: DATE: ENGINEER: REVISIONS DATENO.DESC. 23007 January 26, 2024 ELC DB MAP 0 50'100' SCALE 1" = 50' N LEGEND DRAINAGE BASIN BOUNDARY DRAINAGE BASIN COVER TYPE - PERVIOUS STORM MANHOLE STORM INLET STORM CATCH BASIN STORM POND / SWALE SYMBOL DESCRIPTION ST DRAINAGE BASIN COVER TYPE - IMPERVIOUS DRAINAGE BASIN COVER TYPE - ROOF SHEET OF 21RANGE 5 APARTMENTSDRAINAGE BASIN MAP - ON SITEBOZEMAN, MONTANACIVIL SITE PLANDRAINAGE BASIN COVER TYPE - ROW LOCAL DRAINAGE BASIN COVER TYPE - ROW FOWLER TIME OF CONCENTRATION PATH DRAINAGE DIRECTION 1 01/26/2024 2nd City Submittal DB OFF-SITE UTILUTILWDDDDDDDDDDDDDDDD18SD18SD18SD18SDDDDDDDDDSSSSSSSSSSSSSSSSSSSSSSSco coSOHESTSTW V STSTWLANDINGLANDING UP UP UP UP UP UP UP UP OSWOSWOSWOSW CO COCOCO CO COCO21''ST21''STSTSTBLACKWOOD ROADKURK DRIVEBENNETT BLVDFOWLER LANE DB "FOWLER - KURK TO BENNETT" DB "FOWLER - BLACKWOOD TO KURK" FUTURE 100' ROW SECTION50' WEST HALF OF FUTURE 100' ROW SECTION STMH T-1 W GRAF STREETEDGERTON AVE GABRIEL AVE S 30TH AVE S 31ST AVE EDGERTON AVE GABRIEL AVE BUFF A L O R U N PROJ E C T RANG E 5 PROJ E C T BLACKWOOD ROADPROJECT NO: DATE: ENGINEER: REVISIONS DATENO.DESC. 23007 January 26, 2024 ELC 1 01/26/2024 2nd City Submittal DB MAP 0 150'300' SCALE 1" = 150' N LEGEND DRAINAGE BASIN BOUNDARY DRAINAGE BASIN COVER TYPE - PERVIOUS STORM MANHOLE STORM INLET STORM CATCH BASIN STORM POND / SWALE SYMBOL DESCRIPTION ST DRAINAGE BASIN COVER TYPE - IMPERVIOUS DRAINAGE BASIN COVER TYPE - ROOF SHEET OF 22RANGE 5 APARTMENTSDRAINAGE BASIN MAP - SOUTH FOWLERBOZEMAN, MONTANACIVIL SITE PLANDRAINAGE BASIN COVER TYPE - ROW LOCAL DRAINAGE BASIN COVER TYPE - ROW FOWLER TIME OF CONCENTRATION PATH DRAINAGE DIRECTION Appendix C  Drainage Basin & Storage Facility Calculations                                      LOCAL ROADS (35' TBC TO TBC) Land Use Width (ft) Runoff Coefficient (C)  Width x C HARDSCAPED 45 0.95 42.8 LANDSCAPED 15 0.20 3.0 Total 60 45.8 Weighted C:0.76 LOCAL ROAD BOULEVARD Land Use Width (ft) Runoff Coefficient (C)  Width x C HARDSCAPED 5.0 0.95 4.8 LANDSCAPED 7.5 0.20 1.5 Total 12.5 6.3 Weighted C:0.50 FOWLER ROAD (38' TBC TO TBC) Land Use Width (ft) Runoff Coefficient (C)  Width x C HARDSCAPED 48 0.95 45.6 LANDSCAPED 32 0.20 6.4 Total 80 52.0 Weighted C:0.65 FOWLER ROAD FUTURE (62' TBC TO TBC) Land Use Width (ft) Runoff Coefficient (C)  Width x C HARDSCAPED 82 0.95 77.9 LANDSCAPED 18 0.20 3.6 Total 100 81.5 Weighted C:0.82 FOWLER ROAD FUTURE WEST BLVD Land Use Width (ft) Runoff Coefficient (C) Width x C HARDSCAPED 10 0.95 9.5 LANDSCAPED 9 0.20 1.8 Total 19 11.3 Weighted C:0.59 FOWLER ROAD TEMP EAST BLVD Land Use Width (ft) Runoff Coefficient (C) Width x C HARDSCAPED 10 0.95 9.5 LANDSCAPED 21 0.20 4.2 Total 31 13.7 Weighted C:0.44 Right-of-Way Weighted C-Value Calculations Basis for Calculations Time of Concentration (Ttotal) (minutes)Rainfall Intensity (I) (in/hr) Ttotal = To + Tc Rainfall Frequency Equation To = Time of Concentration for Overland Flow 10 year I = 0.64(X-.65) Tc = Time of Concentration for Channel Flow 25 year I = 0.78(X-.64) Whereas:100 year I = 1.01(X-.67) To = 1.87 (1.1-CCf)D1/2 Tc = L/V/60 Whereas: (Sb)1/3 X = Storm Duration (hr) C = Runoff Coefficient L = Length of Channel (ft) = Ttotal / 60 Cf = Frequency Adjustment Factor V = Mean Velocity (ft/sec) D = Length of Basin (ft)V = 1.486 Gutter Capacity Sb = Slope of Basin (%) n Q = (1.486/n)AR2/3 S1/2 n = Manning's Coefficient R = Hydraulic Radius (ft) Hydraulic Radius = Area (ft2) / Wetted Perimeter (ft)Integral Curb & Gutter 0.136 Sc = Slope of Channel (ft/ft) Rational Method Peak Runoff (Q) Q = CIA Off-Site Flow Drainage Basin Area (Ac.) C-Value Tc (25-yr) (min.)Peak Flow (cfs)Treatment Type Pre-Development 20.52 0.21 34.44 4.88 None Post-Development (DB 1, DB Off-Site)1.24 Varies (~0.80) Varies (5.4 avg.) 3.65 HDS, None Hydrodynamic Separator Facilities Summary Drainage Basin Area (Ac.) C-Value Treatment Flow Rate (cfs)Facility Name 1A, 1B 0.76 0.82 0.47 HDS 1 1C, 1D 0.30 0.76 0.17 HDS 2 Retention Facilities Summary Drainage Basin Area (Ac.) C-Value Volume Required (ft3) Volume Provided (ft3)Facility Name 2 1.94 0.67 3,820 4,640 Pond 2 7 2.33 0.68 4,686 5,575 Pond 7 8 2.45 0.65 4,713 4,995 Pond 8 9 0.09 0.95 246 297 Pond 9 10 0.09 0.76 201 215 Pond 10 11 1.55 0.79 3,632 4,350 Pond 11 Detention Facilities Summary Drainage Basin Area (Ac.) C-Value Volume Required (ft3) Volume Provided (ft3) 3 0.34 0.73 383 605 4 0.64 0.76 843 940 5 0.43 0.76 520 712 6 0.36 0.76 444 606 12 1.09 0.83 1,618 1,703 13 0.60 0.88 912 1,000 14 1.39 0.78 1,928 2,043 15 1.02 0.77 1,423 1,427 16 1.74 0.78 2,423 2,527 17 0.77 0.81 1,103 1,187 18 0.73 0.78 1,003 1,082 Stormtech System 16 Stormtech System 17 Stormtech System 18 Facility Name Stormtech System 6 Stormtech System 12 Stormtech System 13 Stormtech System 14 Stormtech System 15 R2/3(Sc)1/2 Drainage Basin Time of Concentration and Peak Runoff Calculations Stormtech System 3 Stormtech System 4 Stormtech System 5 Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB ‐ R.o.w.‐FOWLER 1A 30,031 0.69 0.82 0.5653 DB ‐ R.o.w.‐FOWLER 1B 3,093 0.07 0.82 0.0582 Total 33,124 0.76 0.6235 Weighted C:0.82 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow)0.59 C * Cf 0.59 0.65 0.74 D - Length of Basin (ft)19 Sb - Slope of Basin (%)2.00 To - Time of Conc. - Overland (min.)3.3 2.92 2.35 L - Length of Channel (ft)599 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft) 0.136 Sc - Slope of Channel (ft/ft)0.0175 V - Velocity (ft/sec)4 4 4Tc - Time of Conc. - Channel (min.)2.5 2.5 2.5 Time of Concentration (Ttotal)5.8 5.42 4.85 X - Storm Duration (hr) 0.10 0.09 0.08I - Intensity (in/hr) 2.92 3.63 5.45 Q - Peak Runoff (cfs) 1.82 2.27 3.4 Pipe Pipe Size (in) Flow Depth - d (in)Slope (ft/ft) Manning's n Velocity Provided Capacity (cfs) Required Capacity (cfs) On-Site 12" PVC 15 14.07 0.005 0.009 5.94 7.10 2.27 Area of Hardscape Total Area (ft2) = 33,124 Weighted C = 0.82 Area of Hardscape (ft2) =27,382 Runoff Reduction Volume (RRV) Requirement Reference: (Eq. 3-1, Montana Post-Construction Storm Water BMP Design Guidance Manual) RRV = (PRvA)/12 P = Water Quality Rainfall Depth (in.) 0.5 I = % Impervious Cover 0.83 Rv = Runoff Coefficient (.05+0.9*I)0.79 A = Site Drainage Area (acres)0.76 Req. Runoff Reduction Volume (ft3)= 1,096 Rainfall Frequency (yr) Pipe Capacity 0.5" Retention Requirement (DSSP II.A.4) HYDRODYNAMIC SEPARATOR 1 Contributing Area & Runoff Coefficient Tabulation Runoff Curve Number (CN) P = Rainfall Depth (in.)0.5 Q = Runoff Depth (acre-ft)0.397 CN = Runoff Curve Number 99 TC = Time of Concentration (hrs)See Adjacent Exhibit 4-II Sheet Flow (TT1) n = Mannings N 0.24 (dense grass) L = Flow Length (ft)8 P2 = 2 yr 24 hr Rainfall (In)1.13 (Per MDEQ Circular DEQ 8 - App A - Table 1) S = Slope (ft/ft)0.02 T1= (.007(nl)0.8) / (P20.5 S0.4) (hrs)0.053 Shallow Concentrated Flow (TT2) S = slope (ft/ft)0.0175 (Gutter Slope) V = Average Velocity (ft/s) = 20.3282*(s)0.5 2.69 L = Length (ft)599 (Gutter Length) T2 = L / (3600V) (hrs) 0.062 Open Channel Flow (TT3) S = Pipe Slope (ft/ft)0.005 From Pipe Capacity Section Above V = Average Velocity 5.94 From Pipe Capacity Section Above L = Pipe Length 44 T3 = L / (3600V) (hrs) 0.002 Tc = T1 + T2 + T3 (hrs)0.117 Initial Abstraction (Ia) = 0.2*((1000/CN)-10)0.02 Ia/P 0.04 Runoff Treatment Flow (RTF) qu = Unit Peak Discharge 1,000 From Exhibit 4-II A = Drainage Area (sq. mi)0.001188Q = Runoff Depth 0.397 RTF = qu*A*Q (cfs)0.47 0.5" Runoff Treatment Flow Rate Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB ‐ R.o.w.‐LOCAL 1C 2,925 0.07 0.76 0.0510 DB ‐ R.o.w.‐LOCAL 1D 10,023 0.23 0.76 0.1749 Total 12,947 0.30 0.2259 Weighted C:0.76 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow)0.5 C * Cf 0.5 0.55 0.63 D - Length of Basin (ft)12.5 Sb - Slope of Basin (%)2.00 To - Time of Conc. - Overland (min.)3.15 2.89 2.49 L - Length of Channel (ft)331 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft) 0.136 Sc - Slope of Channel (ft/ft)0.008 V - Velocity (ft/sec)2.7 2.7 2.7Tc - Time of Conc. - Channel (min.)2.04 2.04 2.04 Time of Concentration (Ttotal)5.19 4.93 4.53 X - Storm Duration (hr) 0.09 0.08 0.08I - Intensity (in/hr) 3.14 3.86 5.70 Q - Peak Runoff (cfs) 0.71 0.87 1.29 Pipe Pipe Size (in) Flow Depth - d (in)Slope (ft/ft) Manning's n Velocity Provided Capacity (cfs) Required Capacity (cfs) On-Site 12" PVC 15 14.07 0.006 0.009 6.50 7.77 0.87 Area of Hardscape Total Area (ft2) = 12,947 Weighted C = 0.76 Area of Hardscape (ft2) =9,667 Runoff Reduction Volume (RRV) Requirement Reference: (Eq. 3-1, Montana Post-Construction Storm Water BMP Design Guidance Manual) RRV = (PRvA)/12 P = Water Quality Rainfall Depth (in.) 0.5 I = % Impervious Cover 0.75 Rv = Runoff Coefficient (.05+0.9*I)0.72 A = Site Drainage Area (acres)0.30 Req. Runoff Reduction Volume (ft3)= 390 HYDRODYNAMIC SEPARATOR 2 Contributing Area & Runoff Coefficient Tabulation Rainfall Frequency (yr) Pipe Capacity 0.5" Retention Requirement (DSSP II.A.4) Runoff Curve Number (CN) P = Rainfall Depth (in.)0.5 Q = Runoff Depth (acre-ft)0.362 CN = Runoff Curve Number 98.6 TC = Time of Concentration (hrs)See Adjacent Exhibit 4-II Sheet Flow (TT1) n = Mannings N 0.24 (dense grass) L = Flow Length (ft)6.5 P2 = 2 yr 24 hr Rainfall (In)1.13 (Per MDEQ Circular DEQ 8 - App A - Table 1) S = Slope (ft/ft)0.02 T1= (.007(nl)0.8) / (P20.5 S0.4) (hrs)0.045 Shallow Concentrated Flow (TT2) S = slope (ft/ft)0.008 (Gutter Slope) V = Average Velocity (ft/s) = 20.3282*(s)0.5 1.82 L = Length (ft)331 (Gutter Length) T2 = L / (3600V) (hrs) 0.051 Open Channel Flow (TT3) S = Pipe Slope (ft/ft)0.006 From Pipe Capacity Section Above V = Average Velocity 6.50 From Pipe Capacity Section Above L = Pipe Length 0 T3 = L / (3600V) (hrs) 0 Tc = T1 + T2 + T3 (hrs)0.096 Initial Abstraction (Ia) = 0.2*((1000/CN)-10)0.028 Ia/P 0.056 Runoff Treatment Flow (RTF) qu = Unit Peak Discharge 1,000 From Exhibit 4-II A = Drainage Area (sq. mi)0.000464Q = Runoff Depth 0.362 RTF = qu*A*Q (cfs)0.17 0.5" Runoff Treatment Flow Rate Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB ‐ R.o.w.‐FOWLER FOWLER - BLACKWOOD TO KURK 133,478 3.06 0.82 2.5127 DB ‐ R.o.w.‐FOWLER FOWLER - KURK TO BENNETT 133,712 3.07 0.82 2.5171 Total 267,190 6.13 5.0297 Weighted C:0.82 10 25 100 Cf - Frequency Adjustment Factor 11.11.25 C - Runoff Coefficient (Overland Flow)0.59 C * Cf 0.59 0.65 0.74 D - Length of Basin (ft)19 Sb - Slope of Basin (%)2.00 To - Time of Conc. - Overland (min.)3.3 2.92 2.35 L - Length of Channel (ft)400n - Manning's Coefficient 0.013R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0150 V - Velocity (ft/sec)3.7 3.7 3.7 Tc - Time of Conc. - Channel (min.)1.8 1.8 1.8 Pipe Dist (ft)3,610 Pipe Velocity (ft)13.64 Tp - Time of Conc. - Pipe Flow (min.)4.41 4.41 4.41 Time of Concentration (Ttotal) - 5 min. minimum 9.51 9.13 8.56 X - Storm Duration (hr)0.16 0.15 0.14I - Intensity (in/hr)2.12 2.60 3.72Q - Peak Runoff (cfs)10.66 13.09 18.73 Pipe Pipe Size (in)Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs) Required Capacity (cfs) 18" SDR-35 PVC 21 15.75 0.016 0.009 26.40 13.09 Drainage Basin: TRUNK MAIN @ STMH T-1 Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Pipe Capacity Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB ‐ R.o.w.‐FOWLER FOWLER - BLACKWOOD TO KURK 133,478 3.06 0.82 2.5127 DB ‐ R.o.w.‐FOWLER FOWLER - KURK TO BENNETT 133,712 3.07 0.82 2.5171 DB ‐ R.o.w.‐FOWLER 1A 30,031 0.69 0.82 0.5653 DB ‐ R.o.w.‐FOWLER 1B 3,093 0.07 0.82 0.0582 Total 300,313 6.89 5.6533 Weighted C:0.82 10 25 100 Cf - Frequency Adjustment Factor 11.11.25 C - Runoff Coefficient (Overland Flow)0.59 C * Cf 0.59 0.65 0.74 D - Length of Basin (ft)19 Sb - Slope of Basin (%)2.00 To - Time of Conc. - Overland (min.)3.3 2.92 2.35 L - Length of Channel (ft)400n - Manning's Coefficient 0.013R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0150 V - Velocity (ft/sec)3.7 3.7 3.7 Tc - Time of Conc. - Channel (min.)1.8 1.8 1.8 Pipe Dist (ft)4,220 Pipe Velocity (ft)11.92 Tp - Time of Conc. - Pipe Flow (min.)5.9 5.9 5.9 Time of Concentration (Ttotal) - 5 min. minimum 11.00 10.62 10.05 X - Storm Duration (hr)0.18 0.18 0.17I - Intensity (in/hr)1.93 2.36 3.34Q - Peak Runoff (cfs)10.9 13.36 18.9 Pipe Pipe Size (in)Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs) Required Capacity (cfs) 30" Equiv. Concrete Arch 22.5" x 36.25" 16.9" (75%) 0.005 0.012 23.75 13.36 Drainage Basin: TRUNK MAIN @ STMH T-3 Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Pipe Capacity Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB ‐ R.o.w.‐FOWLER FOWLER - BLACKWOOD TO KURK 133,478 3.06 0.82 2.5127 DB ‐ R.o.w.‐FOWLER FOWLER - KURK TO BENNETT 133,712 3.07 0.82 2.5171 DB ‐ R.o.w.‐FOWLER 1A 30,031 0.69 0.82 0.5653 T DB ‐ R.o.w.‐FOWLER 1B 3,093 0.07 0.82 0.0582 DB ‐ R.o.w.‐LOCAL 1C 2,925 0.07 0.76 0.0510 DB ‐ R.o.w.‐LOCAL 1D 10,023 0.23 0.76 0.1749 Total 313,261 7.19 5.8792 Weighted C:0.82 10 25 100 Cf - Frequency Adjustment Factor 11.11.25 C - Runoff Coefficient (Overland Flow)0.59 C * Cf 0.59 0.65 0.74 D - Length of Basin (ft)19 Sb - Slope of Basin (%)2.00 To - Time of Conc. - Overland (min.)3.3 2.92 2.35 L - Length of Channel (ft)400 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0150 V - Velocity (ft/sec)3.7 3.7 3.7 Tc - Time of Conc. - Channel (min.)1.8 1.8 1.8 Pipe Dist (ft)4,296Pipe Velocity (ft)11.92 Tp - Time of Conc. - Pipe Flow (min.)6.01 6.01 6.01 Time of Concentration (Ttotal) - 5 min. minimum 11.11 10.73 10.16 X - Storm Duration (hr)0.19 0.18 0.17 I - Intensity (in/hr)1.92 2.35 3.32Q - Peak Runoff (cfs)11.26 13.80 19.52 Pipe Pipe Size (in)Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs)Required Capacity (cfs) 21" SDR-35 PVC 21 19.70 0.005 0.009 17.41 13.80 Drainage Basin: TRUNK MAIN @ STMH T-4 Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Pipe Capacity Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB ‐ R.o.w.‐LOCAL OFF SITE 1,463 0.03 0.74 0.0249 DB ‐ R.o.w.‐FOWLER OFF SITE 6,551 0.15 0.82 0.1233 Total 8,014 0.18 0.1482 Weighted C:0.81 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow) 0.44 C * Cf 0.44 0.48 0.55 D - Length of Basin (ft)31 Sb - Slope of Basin (%)1.50 To - Time of Conc. - Overland (min.)6 5.6 5 L - Length of Channel (ft)63 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0140 V - Velocity (ft/sec)3.58 3.58 3.58 Tc - Time of Conc. - Channel (min.)0.29 0.29 0.29 Time of Concentration (Ttotal) - 5 min. minimum 6.29 5.89 5.29 X - Storm Duration (hr)0.10 0.10 0.09 I - Intensity (in/hr)2.77 3.45 5.14 Q - Peak Runoff (cfs)0.41 0.51 0.76 Gutter Capacity (0.15' Freeboard) n - Manning's Coefficient 0.013 A - Area (ft2)1.25 R - Hydraulic Radius(ft)0.136Sc - Slope of Channel (ft/ft)0.014 Gutter Capacity (cfs) 4.47 Drainage Basin: Off Site POST DEVELOPMENT Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Design Rainfall Frequency (year):10 Storage Method:Retention Rational Method Peak Runoff Equation:Q = CIA Discharge Method:N/A Q = Peak Runoff Rate (cfs)Facility Type: Pond C = Runoff Coefficient Facility Make/Model:N/A I = Rainfall Intensity (in/hr):0.41 A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coe. (C)A (Ac) x C DB - Impervious 2 394 0.009 0.95 0.0086 DB - Pervious 2 7383 0.170 0.2 0.0339 DB - Roof 2 136 0.003 0.95 0.0030 DB - Impervious 2A 2078 0.048 0.95 0.0453 DB - Pervious 2A 11733 0.269 0.2 0.0539 DB - Roof 2A 9027 0.207 0.95 0.1969 DB ‐ R.o.w.‐LOCAL 2A 7953 0.183 0.76 0.1388 DB ‐ R.o.w.‐FOWLER 2A 26934 0.618 0.82 0.5070 DB - Impervious 2B 944 0.022 0.95 0.0206 DB - Pervious 2B 4234 0.097 0.2 0.0194 DB - Roof 2B 6552 0.150 0.95 0.1429 DB ‐ R.o.w.‐LOCAL 2B 7098 0.163 0.76 0.1238 DB ‐ R.o.w.‐FOWLER 2B 0 0.000 0.82 0.0000 Totals 84,466 1.94 1.2940 Weighted C:0.67 Total Area (Acres) = 1.94 Weighted C =0.67 Intensity (in/hr) = 0.41 Duration (hr)2.00 Q (cfs) =0.53 Req. Runoff Volume (ft3)=3,820 Proposed Retention Pond Volume (ft3)4,640 Generated Runoff Volume - 10 year Storage Facility Calculations FACILITY 2 Basis For Calculations Storage Facility Information Contributing Area & Runoff Coefficient Tabulation Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method: Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface Chambers C = Runoff Coefficient Facility Make/Model:ADS Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coe. (C)A (Ac) x C DB - Impervious 3 410 0.01 0.95 0.0090 DB - Pervious 3 1,360 0.03 0.20 0.0062 DB - Roof 3 1,565 0.04 0.95 0.0341 DB ‐ R.o.w.‐LOCAL 3 11,564 0.27 0.76 0.2018 DB ‐ R.o.w.‐FOWLER 300.00 0.65 0.0000 Totals 14899 0.34 0.2511 Weighted C:0.73 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft): 41.5 Infiltration Footprint Width (ft): 14.5 Infiltration Footprint Area (ft2):601 Infiltration Discharge Rate (cfs)0.05 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.65 0.16 572 188.861 382.8 0.65 0.16 575 192.117 383.0 0.64 0.16 578 195.373 383.1 0.63 0.16 582 198.629 383.2 0.63 0.16 585 201.886 383.3 0.62 0.16 588 205.142 383.3 0.61 0.15 592 208.398 383.3 0.61 0.15 595 211.654 383.3 0.60 0.15 598 214.910 383.2 0.60 0.15 601 218.167 383.1 0.59 0.15 604 221.423 383.0 0.58 0.15 607 224.679 382.8 Required Detention Volume (ft3):383 Proposed Storage Volume (ft3)605 (Volume determined using the ADS sizing tool) 59 60 61 62 63 64 65 66 67 68 69 58 Storage Facility Calculations FACILITY 3 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Detention Rational Method Peak Runoff Equation: Q = CIA Infiltration Q = Peak Runoff Rate (cfs)Subsurface Chambers C = Runoff Coefficient ADS Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coe. (C)A (Ac) x C DB - Impervious 4 0 0.00 0.95 0.0000 DB - Pervious 4 0 0.00 0.20 0.0000 DB - Roof 4 0 0.00 0.95 0.0000 DB ‐ R.o.w.‐LOCAL 4 27,915 0.64 0.76 0.4870 DB ‐ R.o.w.‐FOWLER 400.00 0.65 0.0000 Totals 27,915 0.64 0.4870 Weighted C:0.76 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft): 56 Infiltration Footprint Width (ft): 16.5 Infiltration Footprint Area (ft2):924 Infiltration Discharge Rate (cfs)0.08 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.51 0.25 1,268 425.530 842.1 0.51 0.25 1,273 430.536 842.3 0.50 0.24 1,278 435.542 842.4 0.50 0.24 1,283 440.548 842.6 0.50 0.24 1,288 445.555 842.6 0.49 0.24 1,293 450.561 842.7 0.49 0.24 1,298 455.567 842.7 0.48 0.24 1,303 460.573 842.7 0.48 0.23 1,308 465.580 842.6 0.48 0.23 1,313 470.586 842.5 0.47 0.23 1,318 475.592 842.4 0.47 0.23 1,323 480.598 842.2 Required Detention Volume (ft3):843 Proposed Storage Volume (ft3)940 (Volume determined using the ADS sizing tool) 86 87 88 89 90 91 92 93 94 95 96 85 Storage Facility Calculations FACILITY 4 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) Storage Method: Discharge Method: Facility Type: Facility Make/Model: Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method: Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface Chambers C = Runoff Coefficient Facility Make/Model:ADS Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coe. (C)A (Ac) x C DB - Impervious 5 0 0.00 0.95 0.0000 DB - Pervious 5 0 0.00 0.20 0.0000 DB - Roof 5 0 0.00 0.95 0.0000 DB ‐ R.o.w.‐LOCAL 5 18,564 0.43 0.76 0.3239 DB ‐ R.o.w.‐FOWLER 500.00 0.65 0.0000 Totals 18,564 0.43 0.3239 Weighted C:0.76 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft): 48.5 Infiltration Footprint Width (ft): 14.5 Infiltration Footprint Area (ft2):705 Infiltration Discharge Rate (cfs)0.06 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.59 0.19 780 259.739 519.9 0.58 0.19 784 263.559 520.1 0.58 0.19 788 267.378 520.2 0.57 0.19 792 271.198 520.3 0.57 0.18 795 275.018 520.4 0.56 0.18 799 278.837 520.4 0.56 0.18 803 282.657 520.4 0.55 0.18 807 286.477 520.4 0.55 0.18 811 290.296 520.3 0.54 0.18 814 294.116 520.2 0.54 0.17 818 297.936 520.1 0.54 0.17 822 301.756 519.9 Required Detention Volume (ft3):520 Proposed Storage Volume (ft3)712 (Volume determined using the ADS sizing tool) 69 70 71 72 73 74 75 76 77 78 79 68 Storage Facility Calculations FACILITY 5 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method: Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface Chambers C = Runoff Coefficient Facility Make/Model:ADS Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coe. (C)A (Ac) x C DB - Impervious 6 0 0.00 0.95 0.0000 DB - Pervious 6 0 0.00 0.20 0.0000 DB - Roof 6 0 0.00 0.95 0.0000 DB ‐ R.o.w.‐LOCAL 6 15,842 0.36 0.76 0.2764 DB ‐ R.o.w.‐FOWLER 600.00 0.65 0.0000 Totals 15,842 0.36 0.2764 Weighted C:0.76 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft): 48.5 Infiltration Footprint Width (ft): 12.5 Infiltration Footprint Area (ft2):603 Infiltration Discharge Rate (cfs)0.05 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.60 0.17 658 215.626 442.8 0.60 0.16 662 218.893 443.0 0.59 0.16 665 222.160 443.2 0.58 0.16 669 225.427 443.3 0.58 0.16 672 228.694 443.4 0.57 0.16 675 231.961 443.5 0.57 0.16 679 235.228 443.6 0.56 0.16 682 238.495 443.6 0.56 0.15 685 241.762 443.6 0.55 0.15 689 245.029 443.5 0.55 0.15 692 248.296 443.4 0.54 0.15 695 251.563 443.4 Required Detention Volume (ft3):444 Proposed Storage Volume (ft3)606 (Volume determined using the ADS sizing tool) 67 68 69 70 71 72 73 74 75 76 77 66 Storage Facility Calculations FACILITY 6 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) Design Rainfall Frequency (year):10 Storage Method:Retention Rational Method Peak Runoff Equation:Q = CIA Discharge Method:N/A Q = Peak Runoff Rate (cfs)Facility Type: Pond C = Runoff Coefficient Facility Make/Model:N/A I = Rainfall Intensity (in/hr):0.41 A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac) Runoff Coe. (C)A (Ac) x C DB - Impervious 7 538 0.012 0.95 0.0117 DB - Pervious 7 9,155 0.210 0.2 0.0420 DB - Roof 7 0 0.000 0.95 0.0000 DB ‐ R.o.w.‐LOCAL 7A 11,792 0.271 0.76 0.2057 DB - Impervious 7B 2,759 0.063 0.95 0.0602 DB - Pervious 7B 13,121 0.301 0.2 0.0602 DB - Roof 7B 10,455 0.240 0.95 0.2280 DB ‐ R.o.w.‐LOCAL 7B 38,586 0.886 0.76 0.6732 DB - Impervious 7C 9,191 0.211 0.95 0.2004 DB - Pervious 7C 1,237 0.028 0.2 0.0057 DB - Roof 7C 4,587 0.105 0.95 0.1000 Totals 101,421 2.33 1.5873 Weighted C:0.68 Total Area (Acres) = 2.33 Weighted C =0.68 Intensity (in/hr) = 0.41 Duration (hr)2.00 Q (cfs) =0.65 Req. Runoff Volume (ft3)=4,686 Proposed Retention Pond Volume (ft3)5,575 Generated Runoff Volume - 10 year Storage Facility Calculations FACILITY 7 Basis For Calculations Storage Facility Information Contributing Area & Runoff Coefficient Tabulation Design Rainfall Frequency (year):10 Storage Method:Retention Rational Method Peak Runoff Equation:Q = CIA Discharge Method:N/A Q = Peak Runoff Rate (cfs)Facility Type: Pond C = Runoff Coefficient Facility Make/Model:N/A I = Rainfall Intensity (in/hr):0.41 A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac) Runoff Coe. (C)A (Ac) x C DB - Impervious 8 3,595 0.083 0.95 0.0784 DB - Pervious 8 27,234 0.625 0.2 0.1250 DB - Roof 8 15,463 0.355 0.95 0.3372 DB ‐ R.o.w.‐LOCAL 8 60,510 1.389 0.76 1.0557 DB ‐ R.o.w.‐FOWLER 8 0 0.000 0.65 0.0000 Totals 106,802 2.45 1.5964 Weighted C:0.65 Total Area (Acres) = 2.45 Weighted C =0.65 Intensity (in/hr) = 0.41 Duration (hr)2.00 Q (cfs) =0.65 Req. Runoff Volume (ft3)=4,713 Proposed Retention Pond Volume (ft3)4,995 Generated Runoff Volume - 10 year Storage Facility Calculations FACILITY 8 Basis For Calculations Storage Facility Information Contributing Area & Runoff Coefficient Tabulation Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB ‐ R.o.w.‐LOCAL 9 3,813 0.09 0.95 0.0832 Total 3,813 0.09 0.0832 Weighted C:0.95 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow)0.95 C * Cf 0.95 1.05 1.19 D - Length of Basin (ft)0 Sb - Slope of Basin (%)1.75 To - Time of Conc. - Overland (min.)00 0 L - Length of Channel (ft)160 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.011 V - Velocity (ft/sec)3.17 3.17 3.17 Tc - Time of Conc. - Channel (min.)0.84 0.84 0.84 Time of Concentration (Ttotal) - 5 min. minimum 5.00 5.00 5.00 X - Storm Duration (hr)0.08 0.08 0.08 I - Intensity (in/hr)3.22 3.83 5.34Q - Peak Runoff (cfs)0.27 0.32 0.44 0.09 0.95 0.41 2.00 0.03 246 297 Drainage Basin: 9 Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Generated Runoff Volume - 10 year Req. Runoff Volume (ft3)= Proposed Retention Pond Volume (ft3) Total Area (Acres) = Weighted C = Intensity (in/hr) = Duration (hr) Q (cfs) = Design Rainfall Frequency (year):10 Storage Method:Retention Rational Method Peak Runoff Equation: Q = CIA Discharge Method:N/A Q = Peak Runoff Rate (cfs)Facility Type: Pond C = Runoff Coefficient Facility Make/Model:N/A I = Rainfall Intensity (in/hr):0.41 A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coe. (C)A (Ac) x C DB - Impervious 10 0 0.000 0.95 0.0000 DB - Pervious 10 0 0.000 0.2 0.0000 DB - Roof 10 0 0.000 0.95 0.0000 DB ‐ R.o.w.‐LOCAL 10 3,900 0.090 0.76 0.0680 Totals 3,900 0.09 0.0680 Weighted C:0.76 Total Area (Acres) = 0.09 Weighted C =0.76 Intensity (in/hr) = 0.41 Duration (hr)2.00 Q (cfs) =0.03 Req. Runoff Volume (ft3)=201 Proposed Retention Pond Volume (ft3)215 Generated Runoff Volume - 10 year Storage Facility Calculations FACILITY 10 Basis For Calculations Storage Facility Information Contributing Area & Runoff Coefficient Tabulation Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac) Runoff Coefficient (C)A (Ac) x C DB - Impervious 11A 23,347 0.54 0.95 0.5092 DB - Pervious 11A 4,720 0.11 0.2 0.0217 DB - Roof 11A 11,131 0.26 0.95 0.2428 DB ‐ R.o.w.‐LOCAL 11A 0 0.00 0.76 0.0000 DB ‐ R.o.w.‐FOWLER 11A 0 0.00 0.65 0.0000 Total 39,199 0.90 0.7736 Weighted C:0.86 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow)0.2 C * Cf 0.2 0.22 0.25 D - Length of Basin (ft)18 Sb - Slope of Basin (%)6.50 To - Time of Conc. - Overland (min.)3.83 3.74 3.61 L - Length of Channel (ft)456 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0200 V - Velocity (ft/sec)4.28 4.28 4.28 Tc - Time of Conc. - Channel (min.)1.78 1.78 1.78 Time of Concentration (Ttotal) - 5 min. minimum 5.61 5.52 5.39 X - Storm Duration (hr)0.09 0.09 0.09 I - Intensity (in/hr)2.99 3.59 5.08 Q - Peak Runoff (cfs)2.31 2.78 3.93 Gutter Capacity (0.15' Freeboard) n - Manning's Coefficient 0.013 A - Area (ft2)1.25 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.02 Gutter Capacity (cfs)5.34 Pipe Pipe Size (in) Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs) Required Capacity (cfs) 12" SDR-35 PVC 12 11.26 0.006 0.009 4.29 2.78 Drainage Basin: 11A Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Pipe Capacity Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac) Runoff Coefficient (C)A (Ac) x C DB - Impervious 11B 14,297 0.33 0.95 0.3118 DB - Pervious 11B 3,222 0.07 0.2 0.0148 DB - Roof 11B 4,154 0.10 0.95 0.0906 DB ‐ R.o.w.‐LOCAL 11B 0 0.00 0.76 0.0000 DB ‐ R.o.w.‐FOWLER 11B 0 0.00 0.65 0.0000 Total 21,674 0.50 0.4172 Weighted C:0.84 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow) 0.86 C * Cf 0.86 0.95 1.08 D - Length of Basin (ft)204 Sb - Slope of Basin (%)1.50 To - Time of Conc. - Overland (min.)5.6 3.59 0.58 L - Length of Channel (ft)49 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0060 V - Velocity (ft/sec)2.34 2.34 2.34 Tc - Time of Conc. - Channel (min.)0.35 0.35 0.35 Time of Concentration (Ttotal) - 5 min. minimum 5.95 5.00 5.00 X - Storm Duration (hr)0.10 0.08 0.08 I - Intensity (in/hr)2.87 3.83 5.34 Q - Peak Runoff (cfs)1.2 1.60 2.23 Gutter Capacity (0.15' Freeboard) n - Manning's Coefficient 0.013 A - Area (ft2)1.25 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.006 Gutter Capacity (cfs)2.93 Channel Chase Width (in) Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs) Required Capacity (cfs) 18" Curb Cut 18 5 0.020 0.013 4.20 1.60 Drainage Basin: 11B Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Curb Chase Capacity Design Rainfall Frequency (year):10 Storage Method:Retention Rational Method Peak Runoff Equation: Q = CIA Discharge Method:N/A Q = Peak Runoff Rate (cfs)Facility Type: Pond C = Runoff Coefficient Facility Make/Model:N/A I = Rainfall Intensity (in/hr):0.41 A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coe. (C) A (Ac) x C DB - Impervious 11 500 0.011 0.95 0.0109 DB - Pervious 11 6218 0.143 0.2 0.0285 DB - Roof 11 0 0.000 0.95 0.0000 DB ‐ R.o.w.‐LOCAL 11 0 0.000 0.76 0.0000 DB - Impervious 11A 23347 0.536 0.95 0.5092 DB - Pervious 11A 4720 0.108 0.2 0.0217 DB - Roof 11A 11131 0.256 0.95 0.2428 DB ‐ R.o.w.‐LOCAL 11A 0 0.000 0.76 0.0000 DB - Impervious 11B 14297 0.328 0.95 0.3118 DB - Pervious 11B 3222 0.074 0.2 0.0148 DB - Roof 11B 4154 0.095 0.95 0.0906 DB ‐ R.o.w.‐LOCAL 11B 0 0.000 0.76 0.0000 Totals 67,590 1.55 1.2303 Weighted C:0.79 Total Area (Acres) = 1.55 Weighted C =0.79 Intensity (in/hr) = 0.41 Duration (hr)2.00 Q (cfs) =0.50 Req. Runoff Volume (ft3)=3,632 Proposed Retention Pond Volume (ft3)4,350 Generated Runoff Volume - 10 year Storage Facility Calculations FACILITY 11 Basis For Calculations Storage Facility Information Contributing Area & Runoff Coefficient Tabulation Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac) Runoff Coefficient (C)A (Ac) x C DB - Impervious 12 34,397 0.79 0.95 0.7502 DB - Pervious 12 7,416 0.17 0.2 0.0341 DB - Roof 12 5,838 0.13 0.95 0.1273 DB ‐ R.o.w.‐LOCAL 12 0 0.00 0.76 0.0000 DB ‐ R.o.w.‐FOWLER 12 0 0.00 0.65 0.0000 Total 47,651 1.09 0.9115 Weighted C:0.83 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow)0.9 C * Cf 0.9 0.99 1.13 D - Length of Basin (ft)219 Sb - Slope of Basin (%)2.00 To - Time of Conc. - Overland (min.)4.39 2.42 -0.55 L - Length of Channel (ft)133 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0120 V - Velocity (ft/sec)3.31 3.31 3.31 Tc - Time of Conc. - Channel (min.)0.67 0.67 0.67 Time of Concentration (Ttotal) - 5 min. minimum 5.06 5.00 5.00 X - Storm Duration (hr)0.08 0.08 0.08 I - Intensity (in/hr)3.19 3.83 5.34 Q - Peak Runoff (cfs)2.91 3.49 4.87 Gutter Capacity (0.15' Freeboard) n - Manning's Coefficient 0.013 A - Area (ft2)1.25 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.012 Gutter Capacity (cfs)4.14 Pipe Pipe Size (in) Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs) Required Capacity (cfs) 12" SDR-35 PVC 10 9.38 0.02 0.009 4.81 3.49 Drainage Basin: 12 Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Pipe Capacity Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method:Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface C = Runoff Coefficient Facility Make/Model:Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac)Runoff Coe. (C)A (Ac) x C DB - Impervious 12 34397 0.79 0.95 0.7502 DB - Pervious 12 7416 0.17 0.20 0.0341 DB - Roof 12 5838 0.13 0.95 0.1273 Totals 47651 1.09 0.9115 Weighted C:0.83 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft):94.5 Infiltration Footprint Width (ft):18.5 Infiltration Footprint Area (ft2):1,650 Infiltration Discharge Rate (cfs)0.15 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.49 0.45 2,420 804.573 1,615.8 0.49 0.45 2,430 813.513 1,616.3 0.48 0.44 2,439 822.452 1,616.6 0.48 0.44 2,448 831.392 1,617.0 0.48 0.44 2,458 840.332 1,617.2 0.47 0.43 2,467 849.272 1,617.4 0.47 0.43 2,476 858.211 1,617.5 0.47 0.43 2,485 867.151 1,617.6 0.47 0.42 2,494 876.091 1,617.5 0.46 0.42 2,503 885.030 1,617.5 0.46 0.42 2,511 893.970 1,617.4 0.46 0.42 2,520 902.910 1,617.2 Required Detention Volume (ft3):1,618 Proposed Storage Volume (ft3)1,703 (Volume determined using the ADS sizing tool) 91 92 93 94 95 96 97 98 99 100 101 90 Storage Facility Calculations FACILITY 12 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB - Impervious 13A 1,660 0.04 0.95 0.0362 DB - Pervious 13A 115 0.00 0.2 0.0005 DB - Roof 13A 639 0.01 0.95 0.0139 Total 2,414 0.06 0.0507 Weighted C:0.91 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow) 0.88 C * Cf 0.88 0.97 1.10 D - Length of Basin (ft)120 Sb - Slope of Basin (%)3.35 To - Time of Conc. - Overland (min.)3.01 1.81 0 L - Length of Channel (ft)0.1 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0100 V - Velocity (ft/sec)3.02 3.02 3.02 Tc - Time of Conc. - Channel (min.)00 0 Time of Concentration (Ttotal) - 5 min. minimum 5.00 5.00 5.00 X - Storm Duration (hr)0.08 0.08 0.08 I - Intensity (in/hr)3.22 3.83 5.34 Q - Peak Runoff (cfs)0.16 0.19 0.27 Gutter Capacity (0.15' Freeboard) n - Manning's Coefficient 0.013 A - Area (ft2)1.25 R - Hydraulic Radius(ft)0.136Sc - Slope of Channel (ft/ft)0.01 Gutter Capacity (cfs)3.78 Pipe Pipe Size (in) Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs) Required Capacity (cfs) 8" SDR-35 PVC 8 7.50 0.01 0.009 1.88 0.19 Drainage Basin: 13A Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Pipe Capacity Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB - Impervious 13B 15,298 0.35 0.95 0.3336 DB - Pervious 13B 2,289 0.05 0.2 0.0105 DB - Roof 13B 5,921 0.14 0.95 0.1291 Total 23,508 0.54 0.4733 Weighted C:0.88 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow) 0.88 C * Cf 0.88 0.97 1.10 D - Length of Basin (ft)134 Sb - Slope of Basin (%)2.38 To - Time of Conc. - Overland (min.)3.57 2.14 0 L - Length of Channel (ft)113 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0160 V - Velocity (ft/sec)3.82 3.82 3.82 Tc - Time of Conc. - Channel (min.)0.49 0.49 0.49 Time of Concentration (Ttotal) - 5 min. minimum 5.00 5.00 5.00 X - Storm Duration (hr)0.08 0.08 0.08 I - Intensity (in/hr)3.22 3.83 5.34Q - Peak Runoff (cfs)1.52 1.81 2.53 Gutter Capacity (0.15' Freeboard) n - Manning's Coefficient 0.013 A - Area (ft2)1.25 R - Hydraulic Radius(ft)0.136Sc - Slope of Channel (ft/ft)0.016 Gutter Capacity (cfs) 4.78 Pipe Pipe Size (in) Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs) Required Capacity (cfs) 12" SDR-35 PVC 12 11.26 0.01 0.009 5.54 2.00 (DB 13A & 13B) Drainage Basin: 13B Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Pipe Capacity Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method:Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface C = Runoff Coefficient Facility Make/Model:Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac)Runoff Coe. (C)A (Ac) x C DB - Impervious 13A 1,660 0.04 0.95 0.0362 DB - Pervious 13A 115 0.00 0.20 0.0005 DB - Roof 13A 639 0.01 0.95 0.0139 DB - Impervious 13B 15,298 0.35 0.95 0.3336 DB - Pervious 13B 2,289 0.05 0.20 0.0105 DB - Roof 13B 5,921 0.14 0.95 0.1291 Totals 25,922 0.60 0.5239 Weighted C:0.88 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft):63 Infiltration Footprint Width (ft):16.5 Infiltration Footprint Area (ft2):983 Infiltration Discharge Rate (cfs)0.09 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.51 0.27 1,364 452.701 911.0 0.51 0.27 1,369 458.027 911.2 0.50 0.26 1,375 463.353 911.5 0.50 0.26 1,380 468.679 911.6 0.50 0.26 1,386 474.005 911.8 0.49 0.26 1,391 479.330 911.9 0.49 0.26 1,397 484.656 912.0 0.48 0.25 1,402 489.982 912.0 0.48 0.25 1,407 495.308 912.0 0.48 0.25 1,413 500.634 911.9 0.47 0.25 1,418 505.960 911.8 0.47 0.25 1,423 511.286 911.7 Required Detention Volume (ft3):912 Proposed Storage Volume (ft3)1,000 (Volume determined using the ADS sizing tool) 86 87 88 89 90 91 92 93 94 95 96 85 Storage Facility Calculations FACILITY 13 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method:Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface C = Runoff Coefficient Facility Make/Model:Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac)Runoff Coe. (C)A (Ac) x C DB - Impervious 14 38,323 0.88 0.95 0.8358 DB - Pervious 14 13,547 0.31 0.20 0.0622 DB - Roof 14 8,655 0.20 0.95 0.1887 Totals 60,525 1.39 1.0867 Weighted C:0.78 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft):84 Infiltration Footprint Width (ft):27 Infiltration Footprint Area (ft2):1,968 Infiltration Discharge Rate (cfs)0.18 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.48 0.52 2,919 991.624 1,927.3 0.48 0.52 2,930 1,002.287 1,927.6 0.47 0.52 2,941 1,012.949 1,927.8 0.47 0.51 2,952 1,023.612 1,927.9 0.47 0.51 2,962 1,034.275 1,928.0 0.47 0.51 2,973 1,044.937 1,928.0 0.46 0.50 2,983 1,055.600 1,927.9 0.46 0.50 2,994 1,066.262 1,927.7 0.46 0.50 3,004 1,076.925 1,927.5 0.45 0.49 3,015 1,087.588 1,927.2 0.45 0.49 3,025 1,098.250 1,926.9 0.45 0.49 3,035 1,108.913 1,926.5 Required Detention Volume (ft3):1,928 Proposed Storage Volume (ft3)2,043 (Volume determined using the ADS sizing tool) 94 95 96 97 98 99 100 101 102 103 104 93 Storage Facility Calculations FACILITY 14 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method:Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface C = Runoff Coefficient Facility Make/Model:Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac)Runoff Coe. (C)A (Ac) x C DB - Impervious 15 21,168 0.49 0.95 0.4616 DB - Pervious 15 10,626 0.24 0.20 0.0488 DB - Roof 15 12,794 0.29 0.95 0.2790 DB - Impervious 0 0 0.00 0.95 0.0000 DB - Pervious 0 0 0.00 0.20 0.0000 DB - Roof 0 0 0.00 0.95 0.0000 Totals 44,587 1.02 0.7895 Weighted C:0.77 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft):55 Infiltration Footprint Width (ft):25 Infiltration Footprint Area (ft2):1,388 Infiltration Discharge Rate (cfs)0.13 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.47 0.37 2,136 714.417 1,421.9 0.47 0.37 2,144 721.938 1,422.2 0.47 0.37 2,152 729.458 1,422.5 0.47 0.37 2,160 736.978 1,422.7 0.46 0.36 2,167 744.498 1,422.8 0.46 0.36 2,175 752.018 1,423.0 0.46 0.36 2,183 759.539 1,423.0 0.45 0.36 2,190 767.059 1,423.0 0.45 0.36 2,198 774.579 1,423.0 0.45 0.35 2,205 782.099 1,422.9 0.44 0.35 2,212 789.619 1,422.8 0.44 0.35 2,220 797.140 1,422.6 Required Detention Volume (ft3):1,423 Total Provided Volume: 1,427 (Volume determined using the ADS sizing tool) 101 Storage Facility Calculations FACILITY 15 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) 95 96 97 98 99 100 102 103 104 105 106 Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB - Impervious 16A 5,540 0.13 0.95 0.1208 DB - Pervious 16A 1,351 0.03 0.2 0.0062 DB - Roof 16A 2,357 0.05 0.95 0.0514 Total 9,248 0.21 0.1784 Weighted C:0.84 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow) 0.81 C * Cf 0.81 0.89 1.01 D - Length of Basin (ft)64 Sb - Slope of Basin (%)4.80 To - Time of Conc. - Overland (min.)2.57 1.85 0.78 L - Length of Channel (ft)0.1 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0100 V - Velocity (ft/sec)3.02 3.02 3.02 Tc - Time of Conc. - Channel (min.)00 0 Time of Concentration (Ttotal) - 5 min. minimum 5.00 5.00 5.00 X - Storm Duration (hr)0.08 0.08 0.08 I - Intensity (in/hr)3.22 3.83 5.34 Q - Peak Runoff (cfs)0.57 0.68 0.95 Gutter Capacity (0.15' Freeboard) n - Manning's Coefficient 0.013 A - Area (ft2)1.25 R - Hydraulic Radius(ft)0.136Sc - Slope of Channel (ft/ft)0.01 Gutter Capacity (cfs)3.78 Pipe Pipe Size (in) Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs) Required Capacity (cfs) On-Site 8" PVC 8 7.50 0.005 0.009 1.33 0.68 Drainage Basin: 16A Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Pipe Capacity Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method:Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface C = Runoff Coefficient Facility Make/Model:Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac)Runoff Coe. (C)A (Ac) x C DB - Impervious 16A 5,540 0.13 0.95 0.1208 DB - Pervious 16A 1,351 0.03 0.20 0.0062 DB - Roof 16A 2,357 0.05 0.95 0.0514 DB - Impervious 16B 34,139 0.78 0.95 0.7445 DB - Pervious 16B 15,824 0.36 0.20 0.0727 DB - Roof 16B 16,619 0.38 0.95 0.3624 Totals 75,830 1.74 1.3581 Weighted C:0.78 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft):113 Infiltration Footprint Width (ft):23 Infiltration Footprint Area (ft2):2,434 Infiltration Discharge Rate (cfs)0.22 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.48 0.65 3,648 1,226.429 2,421.3 0.48 0.65 3,661 1,239.617 2,421.8 0.47 0.64 3,675 1,252.804 2,422.2 0.47 0.64 3,688 1,265.992 2,422.5 0.47 0.64 3,702 1,279.179 2,422.7 0.47 0.63 3,715 1,292.366 2,422.8 0.46 0.63 3,728 1,305.554 2,422.9 0.46 0.62 3,742 1,318.741 2,422.8 0.46 0.62 3,755 1,331.929 2,422.7 0.45 0.62 3,768 1,345.116 2,422.4 0.45 0.61 3,780 1,358.303 2,422.1 0.45 0.61 3,793 1,371.491 2,421.8 Required Detention Volume (ft3):2,423 Proposed Storage Volume (ft3)2,527 (Volume determined using the ADS sizing tool) 93 Storage Facility Calculations FACILITY 16 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) 94 95 96 97 98 99 100 101 102 103 104 Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method:Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface C = Runoff Coefficient Facility Make/Model:Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac)Runoff Coe. (C)A (Ac) x C DB - Impervious 17 19,823 0.46 0.95 0.4323 DB - Pervious 17 6,224 0.14 0.20 0.0286 DB - Roof 17 7,680 0.18 0.95 0.1675 Totals 33,726 0.77 0.6284 Weighted C:0.81 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft):70 Infiltration Footprint Width (ft):16.5 Infiltration Footprint Area (ft2):1,160 Infiltration Discharge Rate (cfs)0.10 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.49 0.31 1,669 565.639 1,102.9 0.49 0.31 1,675 571.924 1,103.1 0.48 0.30 1,681 578.209 1,103.2 0.48 0.30 1,688 584.494 1,103.3 0.48 0.30 1,694 590.779 1,103.3 0.47 0.30 1,700 597.064 1,103.3 0.47 0.30 1,707 603.348 1,103.3 0.47 0.29 1,713 609.633 1,103.2 0.47 0.29 1,719 615.918 1,103.1 0.46 0.29 1,725 622.203 1,102.9 0.46 0.29 1,731 628.488 1,102.7 0.46 0.29 1,737 634.773 1,102.5 Required Detention Volume (ft3):1,103 Proposed Storage Volume (ft3)1,187 (Volume determined using the ADS sizing tool) 91 92 93 94 95 96 97 98 99 100 101 90 Storage Facility Calculations FACILITY 17 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method:Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface C = Runoff Coefficient Facility Make/Model:Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac)Runoff Coe. (C)A (Ac) x C DB - Impervious 18 20,630 0.47 0.95 0.4499 DB - Pervious 18 7,200 0.17 0.20 0.0331 DB - Roof 18 4,054 0.09 0.95 0.0884 Totals 31,884 0.73 0.5714 Weighted C:0.78 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft):48 Infiltration Footprint Width (ft):23 Infiltration Footprint Area (ft2):1,055 Infiltration Discharge Rate (cfs)0.10 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.50 0.29 1,505 503.007 1,002.3 0.50 0.28 1,511 508.723 1,002.6 0.49 0.28 1,517 514.439 1,002.8 0.49 0.28 1,523 520.155 1,002.9 0.48 0.28 1,529 525.871 1,003.0 0.48 0.28 1,535 531.587 1,003.1 0.48 0.27 1,540 537.303 1,003.2 0.47 0.27 1,546 543.019 1,003.2 0.47 0.27 1,552 548.735 1,003.1 0.47 0.27 1,558 554.451 1,003.0 0.47 0.27 1,563 560.167 1,002.9 0.46 0.26 1,569 565.883 1,002.8 Required Detention Volume (ft3):1,003 Proposed Storage Volume (ft3)1,082 (Volume determined using the ADS sizing tool) 89 90 91 92 93 94 95 96 97 98 99 88 Storage Facility Calculations FACILITY 18 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB - Impervious 19A 13,728 0.32 0.95 0.2994 DB - Pervious 19A 4,781 0.11 0.2 0.0220 DB - Roof 19A 1,748 0.04 0.95 0.0381 DB ‐ R.o.w.‐LOCAL 19A 0 0.00 0.76 0.0000 DB ‐ R.o.w.‐FOWLER 19A 0 0.00 0.65 0.0000 Total 20,257 0.47 0.3595 Weighted C:0.77 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow) 0.73 C * Cf 0.73 0.80 0.91 D - Length of Basin (ft)64 Sb - Slope of Basin (%)3.00 To - Time of Conc. - Overland (min.)3.84 3.08 1.94 L - Length of Channel (ft)146 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0100 V - Velocity (ft/sec)3.02 3.02 3.02 Tc - Time of Conc. - Channel (min.)0.81 0.81 0.81 Time of Concentration (Ttotal) - 5 min. minimum 5.00 5.00 5.00 X - Storm Duration (hr)0.08 0.08 0.08 I - Intensity (in/hr)3.22 3.83 5.34 Q - Peak Runoff (cfs)1.16 1.38 1.92 Gutter Capacity (0.15' Freeboard) n - Manning's Coefficient 0.013 A - Area (ft2)1.25 R - Hydraulic Radius(ft)0.136Sc - Slope of Channel (ft/ft)0.01 Gutter Capacity (cfs)3.78 Pipe Pipe Size (in) Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs) Required Capacity (cfs) 10" SDR-35 PVC 10 9.38 0.008 0.009 3.04 1.38 Drainage Basin: 19A Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Pipe Capacity Land Use Drainage Basin Number Contributing Area (sf) Contributing Area (Ac) Runoff Coefficient (C) A (Ac) x C DB - Impervious 19B 11,384 0.26 0.95 0.2483 DB - Pervious 19B 2,448 0.06 0.2 0.0112 DB - Roof 19B 5,318 0.12 0.95 0.1160 DB ‐ R.o.w.‐LOCAL 19B 0 0.00 0.76 0.0000 DB ‐ R.o.w.‐FOWLER 19B 0 0.00 0.65 0.0000 Total 19,150 0.44 0.3755 Weighted C:0.85 10 25 100 Cf - Frequency Adjustment Factor 1 1.1 1.25 C - Runoff Coefficient (Overland Flow) 0.95 C * Cf 0.95 1.05 1.19 D - Length of Basin (ft)124 Sb - Slope of Basin (%)1.40 To - Time of Conc. - Overland (min.)2.79 1.02 -1.63 L - Length of Channel (ft)48 n - Manning's Coefficient 0.013 R - Hydraulic Radius(ft)0.136 Sc - Slope of Channel (ft/ft)0.0064 V - Velocity (ft/sec)2.42 2.42 2.42 Tc - Time of Conc. - Channel (min.)0.33 0.33 0.33 Time of Concentration (Ttotal) - 5 min. minimum 5.00 5.00 5.00 X - Storm Duration (hr)0.08 0.08 0.08 I - Intensity (in/hr)3.22 3.83 5.34 Q - Peak Runoff (cfs)1.21 1.44 2 Gutter Capacity (0.15' Freeboard) n - Manning's Coefficient 0.013 A - Area (ft2)1.25 R - Hydraulic Radius(ft)0.136Sc - Slope of Channel (ft/ft)0.0064 Gutter Capacity (cfs)3.02 Pipe Pipe Size (in) Flow Depth - d (in)Slope (ft/ft) Manning's n Provided Capacity (cfs) Required Capacity (cfs) On-Site 10" PVC 10 9.38 0.0075 0.009 2.95 2.82 Drainage Basin: 19B Contributing Area & Runoff Coefficient Tabulation Time of Concentration & Runoff Rate Rainfall Frequency (yr) Pipe Capacity Basis For Calculations Storage Facility Information Design Rainfall Frequency:10 year Storage Method:Detention Rational Method Peak Runoff Equation: Q = CIA Discharge Method:Infiltration Q = Peak Runoff Rate (cfs)Facility Type:Subsurface C = Runoff Coefficient Facility Make/Model:Stormtech Chambers ‐ 160LP I = Rainfall Intensity (in/hr) (I = 0.64x-0.65) A = Drainage Basin (acres) Land Use Drainage Basin Number Contributing Area (sf)Contributing Area (Ac)Runoff Coe. (C)A (Ac) x C DB - Impervious 19A 13,728 0.32 0.95 0.2994 DB - Pervious 19A 4,781 0.11 0.20 0.0220 DB - Roof 19A 1,748 0.04 0.95 0.0381 DB - Impervious 19B 11,384 0.26 0.95 0.2483 DB - Pervious 19B 2,448 0.06 0.20 0.0112 DB - Roof 19B 5,318 0.12 0.95 0.1160 Totals 39,407 0.90 0.7350 Weighted C:0.81 Infiltration Rate Native Soil @ Infiltration Depth:Gravel Soil Infiltration Rate (in/hr):3.9 Reference: Circular DEQ 8, App C, Table 2 Infiltration Rate (ft/sec) =0.00009 Infiltration Footprint Length (ft):94.5 Infiltration Footprint Width (ft):18.5 Infiltration Footprint Area (ft2):1,358 Infiltration Discharge Rate (cfs)0.12 Rainfall Intensity (in/hr) (I = 0.64x-0.65) Runoff Rate (cfs) (Q = CIA) Runoff Volume (ft3) (=Q-(Storm Duration x 60)) Discharge Volume (ft3) Required Detention Volume (ft3) (= Runoff Volume - Infiltration Volume) 0.50 0.37 1,936 647.473 1,288.8 0.50 0.36 1,944 654.830 1,289.1 0.49 0.36 1,952 662.188 1,289.3 0.49 0.36 1,959 669.546 1,289.5 0.48 0.36 1,967 676.903 1,289.7 0.48 0.35 1,974 684.261 1,289.8 0.48 0.35 1,981 691.619 1,289.8 0.47 0.35 1,989 698.976 1,289.8 0.47 0.35 1,996 706.334 1,289.8 0.47 0.34 2,003 713.691 1,289.7 0.47 0.34 2,011 721.049 1,289.5 0.46 0.34 2,018 728.407 1,289.3 Required Detention Volume (ft3):1,290 Proposed Storage Volume (ft3)1,402 (Volume determined using the ADS sizing tool) 88 Storage Facility Calculations FACILITY 19 Contributing Area & Runoff Coefficient Tabulation Required Detention Volume Storm Duration (min) 89 90 91 92 93 94 95 96 97 98 99 Appendix D  Stormwater Facilities Maintenance Plan                Range 5 Apartments – Stormwater Facilities Operation & Maintenance Plan Page 1  January 2024  STORMWATER FACILITIES OPERATION & MAINTENANCE PLAN  FOR: Range 5 Apartments    PROPERTY DESCRIPTION  Tract 2, COS 1996  NW ¼ Sec. 23, T2S, R5E, of PMM  City of Bozeman, Gallatin County, Montana  RESPONSIBLE PARTY  2B Holdings, LLC.  7555 Cottonwood Road  Bozeman, MT 59718  (406) 570‐7345  STORMWATER FACILITIES DESCRIPTION  Storm Ponds: The storm ponds for the property were designed to capture runoff from the  adjacent street rights‐of‐way and portions of the apartment site. The ponds were designed with  4:1 max. side slopes and a maximum water storage depth of 1.5 ft. The ponds should be finish  graded with 6” of topsoil and fully vegetated with grass per the approved landscape plans.   Storm Chases: Concrete storm chases of varying widths are designed across the property to  convey runoff from parking lots and streets to ponds in locations where insufficient cover exists  to install storm inlets with pipes. The chases should be installed per City of Bozeman Standard  Drawing No. 02529‐14 with a 6” minimum channel depth, and channel widths as specified on the  site plan.   Storm Sewer Network: The on‐site storm sewer network is comprised of pre‐cast concrete curb  inlets and manholes, and ADS HP storm pipe that conveys runoff to the site storm ponds and  chamber systems. The storm sewer network for the adjacent streets is also comprised of pre‐cast  concrete inlets and manholes, but the storm sewer piping within the rights‐of‐way is either SDR‐ 35 PVC pipe or RCP pipe, per city standards. The on‐site system is installed as depicted on the  approved “Range 5 Apartments Civil Site Plan Set”, while the street storm sewer system is  installed based on the “Range 5 Apartments Infrastructure Improvements Plan Set”, both by  White Mountain Engineering.   Infiltration Chamber Systems: The proposed chamber systems for the project are ADS Stormtech  SC‐160LP Chamber Systems. These systems are detailed in the approved “Range 5 Apartments  Civil Site Plan Set” and are generally comprised of open‐bottomed plastic arches surrounded with  washed angular stone to provide storage and infiltration of runoff. Runoff enters each system  through a manhole with an internal weir that directs initial runoff to the isolator row of the  system. This row is lined with a woven geotextile fabric and an inspection port for easy cleaning  of accumulated debris and sediment. On the other side of the weir is the invert to the pipe    Range 5 Apartments – Stormwater Facilities Operation & Maintenance Plan Page 2  January 2024  manifold that distributes remaining runoff into the rest of the chamber system. The ADS Isolator  Row O&M Manual is included with this plan for reference.   Hydrodynamic Separators: The two hydrodynamic Separators are located in Apex Drive and  Fowler Lane to treat stormwater from these street sections by providing trash, sediment, and  hydrocarbons removal. The units are Contech CDS 2025‐5‐C systems. The units have a center  screen for capture of solids and trash as well as a bottom chamber sump for sediment  accumulation. The Contech CDS Inspection & Maintenance Guide is included with this plan for  reference.   INSPECTION & MAINTENANCE SCHEDULE  The stormwater facilities on site will be inspected and maintained based on the below schedule.  Inspection and maintenance will be performed by the responsible party, the facility employees, or a  contracted third party.   Inspection: Routine inspection of stormwater facilities will include visual inspection to ensure the  facilities are functioning properly and there are no debris accumulated in or clogging the  stormwater facilities. Inspections should also be performed after major storm events producing  approximately 0.5” of rainfall in a 24‐hour period. These inspections shall include observations of  the above ground stormwater facilities for areas of erosion or areas of ponding, and removal of  accumulated trash or debris in facilities. The Stormtech systems and hydrodynamic separators  should be inspected by checking the Stormtech isolator row and hydrodynamic separator sump  for accumulated sediment.   Maintenance: Maintenance shall be performed as necessary based on inspections, and at regular  intervals throughout the year based on the schedule below.   Routine summer and fall maintenance to above ground facilities will generally include removal of  trash, grass clippings, leaves, accumulated sediment, and obstructions, and regular mowing of  vegetated facilities from May to October. Overgrown vegetation should regularly be trimmed  from around pipe and chase outlets during the summer and fall months to prevent clogging.  Winter maintenance will generally include shoveling and chipping of ice in areas where snow and  ice is preventing drainage into chases or inlets. Spring maintenance will include removal of  accumulated sediment or trash from chases, inlets, and ponds, and inspection for areas of sparse  or dead vegetation because of snow storage or plowing operations.   Major maintenance will be scheduled as necessary to repair or replace damaged storm structures  and to revegetate areas of erosion or sparse or dead vegetation. Maintenance to storm ponds  that requires the use of equipment should only be done during summer or fall months when the  facility is dry to avoid rutting or damaging the pond.   Inlets and manholes should be vacuumed or shoveled out when sediment accumulation in the  sumps has reached or exceeded the lowest pipe invert in the structure.    The Stormtech systems and hydrodynamic separators should be inspected and maintained as  outlined in the attached manuals.     Range 5 Apartments – Stormwater Facilities Operation & Maintenance Plan Page 3  January 2024  Inspection & Maintenance Schedule  BMP  Inspection Frequency  A=Annual, M=Monthly, S=After Major  Storm, Q=Quarterly, SA=Semi Annually  Maintenance Frequency  Catch Basin / Storm Inlet SA 1 / year  Storm Chase Q 2‐3 / year  Storm Pond Q 3‐4 / year  Stormtech System SA See Manual  Hydrodynamic Separator SA See Manual  Table Source: Stormwater Equipment Manufacturers Association    Isolator® Row O&M Manual 2 Looking down the Isolator Row from the manhole opening, woven geotextile Fabric is shown between the chamber and stone base. StormTech Isolator Row with Overflow Spillway (not to scale) The Isolator® Row Introduction An important component of any Stormwater Pollution Prevention Plan is inspection and maintenance. The StormTech Isolator Row is a technique to inexpensively enhance Total Suspended Solids (TSS) and Total Phosphorus (TP) removal with easy access for inspection and maintenance. The Isolator RowThe Isolator Row is a row of StormTech chambers, either SC-160, SC-310, SC-310-3, SC-740, DC-780, MC-3500 or MC-7200 models, that is surrounded with filter fabric and connected to a closely located manhole for easy access. The fabric-wrapped chambers provide for sediment settling and filtration as stormwater rises in the Isolator Row and passes through the filter fabric. The open bottom chambers and perforated sidewalls (SC-310, SC- 310-3 and SC-740 models) allow stormwater to flow both vertically and horizontally out of the chambers. Sediments are captured in the Isolator Row protecting the adjacent stone and chambers storage areas from sediment accumulation. ADS geotextile fabric is placed between the stone and the Isolator Row chambers. The woven geotextile provides a media for stormwater filtration, a durable surface for maintenance, prevents scour of the underlying stone and remains intact during high pressure jetting. A non-woven fabric is placed over the chambers to provide a filter media for flows passing through the chamber’s sidewall. The non-woven fabric is not required over the SC-160, DC-780, MC-3500 or MC-7200 models as these chambers do not have perforated side walls. The Isolator Row is designed to capture the “first flush” runoff and offers the versatility to be sized on a volume basis or a flow-rate basis. An upstream manhole provides access to the Isolator Row and includes a high/low concept such that stormwater flow rates or volumes that exceed the capacity of the Isolator Row bypass through a manifold to the other chambers. This is achieved with an elevated bypass manifold or a high-flow weir. This creates a differential between the Isolator Row row of chambers and the manifold to the rest of the system, thus allowing for settlement time in the Isolator Row. After Stormwater flows through the Isolator Row and into the rest of the chamber system it is either exfiltrated into the soils below or passed at a controlled rate through an outlet manifold and outlet control structure. The Isolator Row may be part of a treatment train system. The treatment train design and pretreatment device selection by the design engineer is often driven by regulatory requirements. Whether pretreatment is used or not, StormTech recommend using the Isolator Row to minimize maintenance requirements and maintenance costs. Note: See the StormTech Design Manual for detailed information on designing inlets for a StormTech system, including the Isolator Row. ECCENTRICHEADER MANHOLEWITHOVERFLOWWEIR STORMTECHISOLATOR ROW OPTIONAL PRE-TREATMENT OPTIONAL ACCESS STORMTECH CHAMBERS 3 Inspection The frequency of inspection and maintenance varies by location. A routine inspection schedule needs to be established for each individual location based upon site specific variables. The type of land use (i.e. industrial, commercial, residential), anticipated pollutant load, percent imperviousness, climate, etc. all play a critical role in determining the actual frequency of inspection and maintenance practices. At a minimum, StormTech recommends annual inspections. Initially, the Isolator Row should be inspected every 6 months for the first year of operation. For subsequent years, the inspection should be adjusted based upon previous observation of sediment deposition. The Isolator Row incorporates a combination of standard manhole(s) and strategically located inspection ports (as needed). The inspection ports allow for easy access to the system from the surface, eliminating the need to perform a confined space entry for inspection purposes. If upon visual inspection it is found that sediment has accumulated, a stadia rod should be inserted to determine the depth of sediment. When the average depth of sediment exceeds 3 inches throughout the length of the Isolator Row, clean-out should be performed. Maintenance The Isolator Row was designed to reduce the cost of periodic maintenance. By “isolating” sediments to just one row, costs are dramatically reduced by eliminating the need to clean out each row of the entire storage bed. If inspection indicates the potential need for maintenance, access is provided via a manhole(s) located on the end(s) of the row for cleanout. If entry into the manhole is required, please follow local and OSHA rules for a confined space entries. Maintenance is accomplished with the JetVac process. The JetVac process utilizes a high pressure water nozzle to propel itself down the Isolator Row while scouring and suspending sediments. As the nozzle is retrieved, the captured pollutants are flushed back into the manhole for vacuuming. Most sewer and pipe maintenance companies have vacuum/JetVac combination vehicles. Selection of an appropriate JetVac nozzle will improve maintenance efficiency. Fixed nozzles designed for culverts or large diameter pipe cleaning are preferable. Rear facing jets with an effective spread of at least 45” are best. JetVac reels can vary in length. For ease of maintenance, ADS recommends Isolator Row lengths up to 200" (61 m). The JetVac process shall only be performed on StormTech Isolator Rows that have AASHTO class 1 woven geotextile (as specified by StormTech) over their angular base stone. Isolator Row Inspection/Maintenance StormTech Isolator Row (not to scale) Note: Non-woven fabric is only required over the inlet pipe connection into the end cap for SC-160LP, DC-780, MC-3500 and MC-7200 chamber models and is not required over the entire Isolator Row. Isolator Row Step By Step Maintenance Procedures Step 1 Inspect Isolator Row for sediment. A) Inspection ports (if present) i. Remove lid from floor box frame ii. Remove cap from inspection riser iii. Using a flashlight and stadia rod,measure depth of sediment and record results on maintenance log. iv. If sediment is at or above 3 inch depth, proceed to Step 2. If not, proceed to Step 3. B) All Isolator Row i. Remove cover from manhole at upstream end of Isolator Row ii. Using a flashlight, inspect down Isolator Row through outlet pipe 1. Mirrors on poles or cameras may be used to avoid a confined space entry 2. Follow OSHA regulations for confined space entry if entering manhole iii. If sediment is at or above the lower row of sidewall holes (approximately 3 inches), proceed to Step 2. If not, proceed to Step 3. Step 2 Clean out Isolator Row using the JetVac process. A) A fixed floor cleaning nozzle with rear facing nozzle spread of 45 inches or more is preferable B) Apply multiple passes of JetVac until backflush water is clean C) Vacuum manhole sump as required Step 3 Replace all caps, lids and covers, record observations and actions. Step 4 Inspect & clean catch basins and manholes upstream of the StormTech system. ADS “Terms and Conditions of Sale” are available on the ADS website, www.ads-pipe.com The ADS logo and the Green Stripe are registered trademarks of Advanced Drainage Systems, Inc. Stormtech® and the Isolator® Row are registered trademarks of StormTech, Inc. © 2022 Advanced Drainage Systems, Inc. #11011 2/22 CS  )( Sample Maintenance Log Date Stadia Rod Readings Sedi- ment Depth (1)–(2) Observations/Actions InspectorFixed point to chamber bottom (1) Fixed point to top of sediment (2) 3/15/11 6.3 ft none New installation. Fixed point is CI frame at grade DJM 9/24/11 6.2 0.1 ft Some grit felt SM 6/20/13 5.8 0.5 ft Mucky feel, debris visible in manhole and in Isolator Row, maintenance due NV 7/7/13 6.3 ft 0 System jetted and vacuumed DJM adspipe.com 800-821-6710 CDS® Inspection and Maintenance Guide ENGINEERED SOLUTIONS Maintenance The CDS system should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit. For example, unstable soils or heavy winter sanding will cause the grit chamber to fill more quickly but regular sweeping of paved surfaces will slow accumulation. Inspection Inspection is the key to effective maintenance and is easily performed. Pollutant transport and deposition may vary from year to year and regular inspections will help ensure that the system is cleaned out at the appropriate time. At a minimum, inspections should be performed twice per year (e.g. spring and fall) however more frequent inspections may be necessary in climates where winter sanding operations may lead to rapid accumulations, or in equipment washdown areas. Installations should also be inspected more frequently where excessive amounts of trash are expected. The visual inspection should ascertain that the system components are in working order and that there are no blockages or obstructions in the inlet and separation screen. The inspection should also quantify the accumulation of hydrocarbons, trash, and sediment in the system. Measuring pollutant accumulation can be done with a calibrated dipstick, tape measure or other measuring instrument. If absorbent material is used for enhanced removal of hydrocarbons, the level of discoloration of the sorbent material should also be identified during inspection. It is useful and often required as part of an operating permit to keep a record of each inspection. A simple form for doing so is provided. Access to the CDS unit is typically achieved through two manhole access covers. One opening allows for inspection and cleanout of the separation chamber (cylinder and screen) and isolated sump. The other allows for inspection and cleanout of sediment captured and retained outside the screen. For deep units, a single manhole access point allows both sump cleanout and access outside the screen. The CDS system should be cleaned when the level of sediment has reached 75% of capacity in the isolated sump or when an appreciable level of hydrocarbons and trash has accumulated. If absorbent material is used, it should be replaced when significant discoloration has occurred. Performance will not be impacted until 100% of the sump capacity is exceeded however it is recommended that the system be cleaned prior to that for easier removal of sediment. The level of sediment is easily determined by measuring from finished grade down to the top of the sediment pile. To avoid underestimating the level of sediment in the chamber, the measuring device must be lowered to the top of the sediment pile carefully. Particles at the top of the pile typically offer less resistance to the end of the rod than consolidated particles toward the bottom of the pile. Once this measurement is recorded, it should be compared to the as-built drawing for the unit to determine weather the height of the sediment pile off the bottom of the sump floor exceeds 75% of the total height of isolated sump. Cleaning Cleaning of a CDS systems should be done during dry weather conditions when no flow is entering the system. The use of a vacuum truck is generally the most effective and convenient method of removing pollutants from the system. Simply remove the manhole covers and insert the vacuum hose into the sump. The system should be completely drained down and the sump fully evacuated of sediment. The area outside the screen should also be cleaned out if pollutant build-up exists in this area. In installations where the risk of petroleum spills is small, liquid contaminants may not accumulate as quickly as sediment. However, the system should be cleaned out immediately in the event of an oil or gasoline spill should be cleaned out immediately. Motor oil and other hydrocarbons that accumulate on a more routine basis should be removed when an appreciable layer has been captured. To remove these pollutants, it may be preferable to use absorbent pads since they are usually less expensive to dispose than the oil/water emulsion that may be created by vacuuming the oily layer. Trash and debris can be netted out to separate it from the other pollutants. The screen should be power washed to ensure it is free of trash and debris. Manhole covers should be securely seated following cleaning activities to prevent leakage of runoff into the system from above and also to ensure that proper safety precautions have been followed. Confined space entry procedures need to be followed if physical access is required. Disposal of all material removed from the CDS system should be done in accordance with local regulations. In many jurisdictions, disposal of the sediments may be handled in the same manner as the disposal of sediments removed from catch basins or deep sump manholes. Table 1: CDS Maintenance Indicators and Sediment Storage Capacities 800.925.5240www.ContechES.com SUPPORT• DRAWINGS AND SPECIFICATIONS ARE AVAILABLE AT WWW.CONTECHSTORMWATER.COM. • SITE-SPECIFIC DESIGN SUPPORT IS AVAILABLE FROM OUR ENGINEERS. ©2023 CONTECH ENGINEERED SOLUTIONS LLC, A QUIKRETE COMPANY CONTECH ENGINEERED SOLUTIONS LLC PROVIDES SITE SOLUTIONS FOR THE CIVIL ENGINEERING INDUSTRY. CONTECH’S PORTFOLIO INCLUDES BRIDGES, DRAINAGE, SANITARY SEWER, AND STORMWATER TREATMENT PRODUCTS. FOR INFORMATION, VISIT WWW.CONTECHES.COM OR CALL 800.338.1122 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS AN EXPRESSED WARRANTY OR AN IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. SEE THE CONTECH STANDARD CONDITION OF SALES (VIEWABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. THE PRODUCT(S) DESCRIBED MAY BE PROTECTED BY ONE OR MORE OF THE FOLLOWING US PATENTS: 5,322,629; 5,624,576; 5,707,527; 5,759,415; 5,788,848; 5,985,157; 6,027,639; 6,350,374; 6,406,218; 6,641,720; 6,511,595; 6,649,048; 6,991,114; 6,998,038; 7,186,058; 7,296,692; 7,297,266; 7,517,450 RELATED FOREIGN PATENTS OR OTHER PATENTS PENDING. CDS Maintenance 10/17 ENGINEERED SOLUTIONS CDS Model Diameter Distance from Water Surface to Top of Sediment Pile Sediment Storage Capacity ft m ft m y3 m3 CDS1515 3 0.9 3.0 0.9 0.5 0.4 CDS2015 4 1.2 3.0 0.9 0.9 0.7 CDS2015 5 1.5 3.0 0.9 1.3 1.0 CDS2020 5 1.5 3.5 1.1 1.3 1.0 CDS2025 5 1.5 4.0 1.2 1.3 1.0 CDS3020 6 1.8 4.0 1.2 2.1 1.6 CDS3025 6 1.8 4.0 1.2 2.1 1.6 CDS3030 6 1.8 4.6 1.4 2.1 1.6 CDS3035 6 1.8 5.0 1.5 2.1 1.6 CDS4030 8 2.4 4.6 1.4 5.6 4.3 CDS4040 8 2.4 5.7 1.7 5.6 4.3 CDS4045 8 2.4 6.2 1.9 5.6 4.3 CDS5640 10 3.0 6.3 1.9 8.7 6.7 CDS5653 10 3.0 7.7 2.3 8.7 6.7 CDS5668 10 3.0 9.3 2.8 8.7 6.7 CDS5678 10 3.0 10.3 3.1 8.7 6.7 CDS Inspection & Maintenance Log CDS Model: Location: Water Floatable Describe Maintenance Date depth to Layer Maintenance Personnel Comments sediment1 Thickness2 Performed —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— 1. The water depth to sediment is determined by taking two measurements with a stadia rod: one measurement from the manhole opening to the top of the sediment pile and the other from the manhole opening to the water surface. If the difference between these measurements is less than the values listed in table 1 the system should be cleaned out. Note: to avoid underestimating the volume of sediment in the chamber, the measuring device must be carefully lowered to the top of the sediment pile. 2. For optimum performance, the system should be cleaned out when the floating hydrocarbon layer accumulates to an appreciable thickness. In the event of an oil spill, the system should be cleaned immediately. Appendix E  Groundwater Monitoring Results  Project Engineer: Noah SchaibleProject:Well Information:bgs = below ground surface ags = above ground surfaceMW-1 MW-2 MW-3 MW-4 MW-5 MW-6 MW-7 MW-81.82 2.10 2.70 2.60 5.60 3.00 3.00 3.20Date Depth to Ground Water (feet-bgs)MW-1 MW-2 MW-3 MW-4 MW-5 MW-6 MW-7 MW-804/28/23 2.68 2.85 2.20 2.25 0.05 2.10 2.34 2.0505/04/23 3.10 3.40 2.45 2.74 0.38 2.69 2.96 2.6305/11/23 3.61 3.95 2.61 2.99 0.45 3.07 3.45 3.0805/15/23 3.91 4.17 1.76 3.18 0.72 3.24 3.65 3.3005/27/23 3.16 4.40 3.06 3.47 0.84 3.38 3.69 2.9006/02/23 2.41 4.25 3.33 3.61 1.05 3.35 3.43 2.5906/09/23 2.68 3.68 2.48 2.59 0.04 2.42 2.78 1.9906/15/23 2.10 3.63 2.74 2.83 0.45 2.59 2.80 1.9406/23/23 2.94 3.79 2.85 3.04 0.70 2.92 3.13 2.4806/30/23 3.18 3.90 2.86 3.09 0.71 3.03 3.28 2.6607/07/23 2.49 4.07 2.99 3.31 0.86 3.21 3.38 2.5407/13/23 2.98 4.26 3.14 3.47 1.07 3.38 3.56 2.7907/20/23 3.59 4.48 3.37 3.77 1.36 3.74 3.89 3.1807/27/23 4.31 4.95 3.83 5.18 1.71 4.28 4.42 3.72SHGW: 2.10 2.85 1.76 2.25 0.04 2.10 2.34 1.94TotalAverage GW Depth: 3.08 3.98 2.83 3.25 0.74 3.10 3.34 2.70Difference: 0.98 1.13 1.07 1.00 0.70 1.00 1.00 0.760.96Groundwater Information:Monitor Well DataProject Number: 230013134840 Fowler LaneProject Location:1143 Stoneridge Drive • Bozeman, Montana • Phone (406) 587-1115 Well IDGround Elevation Well Depth (feet bgs)Top of Well (feet ags) 700 ft N➤➤N