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Home My WebLink About2021-03-30_HAVEN DRAINAGE REPORT WITH ATTACHMENTS HAVEN FINAL DRAINAGE REPORT BOZEMAN, MONTANA CERTIFICATION I hereby state that this Final Drainage Report has been prepared by me or under my supervision and meets the standard of care and expertise which is usual and customary in this community of professional engineers. The analysis has been prepared utilizing procedures and practices specified by the City of Bozeman and within the standard accepted practices. ____________________________________________ ___________________________ Mike Russell, P.E. Date 03/17/2021 March 17, 2020 Project No. 20069 DRAINAGE REPORT HAVEN BOZEMAN, MONTANA 59715 OVERVIEW NARRATIVE The purpose of this drainage plan is to present a summary of calculations to quantify the stormwater runoff for the Haven project improvements. All design criteria and calculations are in accordance with The City of Bozeman Design Standards and Specifications Policy, dated March 2004. The site stormwater improvements have been designed with the intent to meet the current City of Bozeman drainage regulations for the entire site (both private on-site improvements and public ROW improvements) to the extent feasible. The site is located north of Bozeman Pond in Southwest Bozeman and is approximately 3.08 acres. The project area currently consists of unimproved land. The project will include the construction of two new buildings, connections to existing water and sewer infrastructure surrounding the proposed development, parking areas, and other surface and landscape improvements. Stormwater facilities proposed for the development include a chamber system and surface pond for retention and infiltration/treatment of runoff. Calculations for each sub-basin are included in this submittal. P:2021-03-17_HAVEN DRAINAGE REPORT 2 (03/17/21) JAZ/mr I. Design Approach The modified rational method was used to determine peak runoff rates and volumes. The rational formula provided in The City of Bozeman Standard Specifications and Policy was used to calculate the peak runoff rates on site, time of concentration, rainfall intensities, etc. To be conservative, we treated most watersheds as if they were predominately impervious cover, therefore we assumed a time of concentration of 5-minutes. For impervious surfaces, a runoff coefficient of 0.95 was assumed, and for pervious surfaces, a runoff coefficient of 0.15 was assumed. Infiltration rates were not considered in the sizing of each dry well. II. Proposed Watershed Descriptions For the following sections, please refer to Exhibit A of this report, which graphically shows and labels the onsite watersheds as well as the proposed drainage and conveyance facilities. No percolation rates have been included in these calculations to be conservative. All calculations used the 10-year, 2-hour design storm frequency for rainfall data. Sub-Basin #1 (Red) Sub-Basin #1 includes the sidewalk, boulevard, and paved area of the cul-de-sac tie-in with the existing roadway. The required site retention volume was calculated to be 716 ft3. Chamber System #1 provides 739 ft3 of storage, so adequate storage is provided for Sub- Basin #1. Sub-Basin #2 (Green) Sub-Basin #2 includes runoff from the remaining area of the site not described above in Sub-Basin #1. Runoff generated in Sub-Basin #2 is captured by a series of landscape and hardscape area inlets where it is then conveyed through a storm pipe network to a surface pond located along the north side of the vistor parking area, between the back of curb and the 50-foot stream setback. The required site retention volume was calculated to be 3,429 ft3. The surface pond provides 4,615 ft3 of storage, so adequate storage is provided for Sub- Basin #2. A stage storage table and pond exhibit are provided in the appendices of this report. III. Water Quality The City of Bozeman Design Standards and Specifications Policy states the requirement to capture or reuse the runoff generated from the first 0.5 inches of rainfall from a 24-hour storm. We meet this requirement by retaining all storm runoff on site with no discharge into the City storm drain system for the 10-year, 2-hour design storm. IV. Outlet Structures All runoff will be captured and retained on site. There are no outlet structures proposed for this project. P:2021-03-17_HAVEN DRAINAGE REPORT 3 (03/17/21) JAZ/mr V. Appendices Appendix A – Exhibit A – Stormwater Basins Appendix B – Stage Storage and Pond Exhibit Appendix C – Hydrology Calculations Appendix D – Surface Improvements O&M Plan Appendix E – Geotechnical Investigation P:2021-03-17_HAVEN DRAINAGE REPORT 4 (03/17/21) JAZ/mr Appendix A EXHIBIT A – STORMWATER BASINS 1 2 2 2 EXHIBIT A NORTH 025 SCALE:1" = 50' 5025 P:2021-03-17_HAVEN DRAINAGE REPORT 5 (03/17/21) JAZ/mr Appendix B STAGE STORAGE AND POND EXHIBIT P:2021-03-17_HAVEN DRAINAGE REPORT 6 (03/17/21) JAZ/mr Appendix C HYDROLOGY CALCULATIONS Project: HAVEN Project #: 20069 Date: 03/17/2021 Design Storm Frequency =10 years Discharge Rate, d =0.00 cfs Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 10894 0.250 0.95 1 0.95 0.95 0.24 1837 0.042 0.15 1 0.15 0.15 0.01 1 0.00 0.00 0 1 0.00 0.00 0 1 0.00 0.00 0 12731 0.2923 0.2439 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =0.24 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 9.16 2.23 5 3.22 0.79 10 2.05 0.50 15 1.58 0.38 20 1.31 0.32 25 1.13 0.28 30 1.00 0.24 35 0.91 0.22 40 0.83 0.20 45 0.77 0.19 50 0.72 0.18 55 0.68 0.17 60 0.64 0.16 75 0.55 0.14 90 0.49 0.12 105 0.44 0.11 120 0.41 0.10 150 0.35 0.09 180 0.31 0.08 360 0.20 0.05 720 0.13 0.03 1440 0.08 0.02 716.27 ft3 0.79 (ft3/s) 1341.01 0.00 1341.01 1709.19 0.00 1709.19 825.49 0.00 825.49 1052.13 0.00 1052.13 716.27 0.00 716.27 774.46 0.00 774.46 647.66 0.00 647.66 683.57 0.00 683.57 561.98 0.00 561.98 607.63 0.00 607.63 527.23 0.00 527.23 545.12 0.00 545.12 487.62 0.00 487.62 508.15 0.00 508.15 440.92 0.00 440.92 465.36 0.00 465.36 382.58 0.00 382.58 413.66 0.00 413.66 300.17 0.00 300.17 345.94 0.00 345.94 134.08 0.00 134.08 235.51 0.00 235.51 = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft 3) (ft 3) = 0.8346 Cwd x Cf =0.83 Runoff Volume Discharge Volume Site Detention = Pervious Totals Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS POST-IMPROVEMENT CONDITIONS (RED) Surface Type = Project: HAVEN Project #: 20069 Date: 03/17/2021 Design Storm Frequency =10 years Discharge Rate, d =0.00 cfs Input values for runoff coefficients from appropriate tables. Area Area Runoff Coefficient Frequency Factor Calculation Value A A/(43560 ft2/acre)C Cf C x Cf C' C' x A (ft2)(Acres)=(C x Cf) < or = 1 (Acres) 40954 0.940 0.95 1 0.95 0.95 0.89 79748 1.831 0.15 1 0.15 0.15 0.27 1 0.00 0.00 0 1 0.00 0.00 0 1 0.00 0.00 0 120702 2.7709 1.1678 Weighted Runoff Coefficient, Cwd SCjAj SAj Cwd x Cf x SAj =1.17 Where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j Rainfall Rainfall Peak Flow Duration, t Intensity, i = Cwd x SAj x i (min) (in/hr)(ft3/s) 1 9.16 10.70 5 3.22 3.76 10 2.05 2.40 15 1.58 1.84 20 1.31 1.53 25 1.13 1.32 30 1.00 1.17 35 0.91 1.06 40 0.83 0.97 45 0.77 0.90 50 0.72 0.84 55 0.68 0.79 60 0.64 0.75 75 0.55 0.65 90 0.49 0.57 105 0.44 0.52 120 0.41 0.48 150 0.35 0.41 180 0.31 0.37 360 0.20 0.23 720 0.13 0.15 1440 0.08 0.09 3,429.29 ft3 3.76 (ft3/s) Impervious RATIONAL METHOD FOR RUNOFF CALCULATIONS POST-IMPROVEMENT CONDITIONS (GREEN) Surface Type Pervious Totals = 0.4214 Cwd x Cf =0.42 Runoff Volume Discharge Volume Site Detention = = Cwd x SAj x i x t = d x t = Runoff Volume - Discharge Volume (ft3) (ft 3) (ft 3) 641.93 0.00 641.93 1127.54 0.00 1127.54 1437.11 0.00 1437.11 1656.24 0.00 1656.24 1831.69 0.00 1831.69 1980.48 0.00 1980.48 2110.97 0.00 2110.97 2228.00 0.00 2228.00 2334.60 0.00 2334.60 2432.85 0.00 2432.85 2524.24 0.00 2524.24 2609.86 0.00 2609.86 2690.57 0.00 2690.57 2909.12 0.00 2909.12 3100.81 0.00 3100.81 3272.70 0.00 3272.70 3429.29 0.00 3429.29 3707.85 0.00 3707.85 3952.17 0.00 3952.17 5037.28 0.00 5037.28 6420.32 0.00 6420.32 8183.09 0.00 8183.09 = P:2021-03-17_HAVEN DRAINAGE REPORT 7 (03/17/21) JAZ/mr Appendix D SURFACE IMPROVEMENTS O&M PLAN March 17, 2021 Project No. 20069 STORM DRAINAGE FACILITY MAINTENANCE PLAN FOR HAVEN BOZEMAN, MONTANA OVERVIEW NARRATIVE The purpose of this maintenance plan is to outline the necessary details related to ownership, responsibility and cleaning schedule for the storm drainage facilities for Haven. This plan has been completed in accordance with The City of Bozeman Design Standards and Specifications Policy, dated March 2004. The site stormwater improvements have been designed with the intent to meet the current City of Bozeman drainage regulations for the entire site to the extent feasible. Specific site information and criteria are described below: I. Ownership of Facilities Haven Haven will own all stormwater facilities which includes the chamber system, surface pond and piping within the site boundary. II. Inspection Thresholds for Cleaning Infiltration Chamber If sediment in isolator row exceeds 3 inches or grate is more than 25% clogged with debris, clean grate and/or structure and vacuum isolator row. Surface Pond Remove vegetation and debris at pipe inlets to pond. Fix erosion and scouring. Remove vegetation and debris from trash rack. If piping or erosion is visible, consult engineer. III. Cleaning Infiltration Chamber To clean grate of structure, remove and disposed of debris clogging the grate. To clean structure, use catch basin vacuum to remove sediment and debris. To clean isolator row, use a JetVac. P:2021-03-17_HAVEN_O&M 2 (03/17/21) JAZ/mr Surface Pond Remove vegetation and debris from trash racks and pond inlets. Check for slumping or sloughing of pond slopes. IV. Schedule Infiltration Chamber Inspection: Every 6 months Vacuum Isolator Row: Every 5 years or as needed based on inspection Surface Pond Inspection: Every 6 months and after storm events V. Responsible Party Haven Haven will be responsible for the inspection and maintenance of all stormwater facilities located within the project limits. I agree to the above operation, maintenance and replacement schedule detailed above. Signature: __________________________________________ Haven Representative Checklist continued on next page INSPECTOR’S NAME:DATE:NAME & ADDRESS OF STORMWATERFACILITY:GENERAL OBSERVATIONS (IS WATERFLOWING?):WEATHER:Checked? (Y/N)Maintenance Needed? (Y/N)Observations and Remarks Look for debris, trash and sediment blocking catch basin grate. If found, remove. Replace grate if damaged.Inspect filter if installed. Change if torn or clogged.Look for sediment and trash in catch basin sump. Clean out if sediment fills 60% of the sump or comes within 6” of a pipe.Look for damage or cracks to frame, grate, basin walls or bottom. If found, repair or replace.Check integrity of ladder rungs, cleanout gate, and orifice plate. If bent or obstructed, take appropriate action. Check for undercutting, scouring, and slumping. If found, repair or maintain.Remove all trash and loose sediment. Remove sediment if it will impede water flow or clog downstream structures.Remove vegetation that impedes water movement. Remove vegetation over 9” in height, and all trees and shrubs impeding flow.Repair check dams as necessary.Remove any dumped yard waste.In ditches and swales, check for integrity of grass, check dams, inlets, and outlets. Remove shrubs and trees. CATCH BASINS AND INLETS CONVEYANCES Stormwater System Inspection Checklist G-6 | Page Checked? (Y/N)Maintenance Needed? (Y/N)Observations and Remarks Inlets and outlets: remove vegetation and debris. Fix erosion and scouring. Fix cause of sediment found below outlet.Remove vegetation and debris from trash rack.Add rock to energy dissipater if missing.If necessary, repair rock on spillway. Remove trees, shrubs, and vegetation over 4”. If piping or erosion is visible, consult engineer. Check for slumping or sloughing of walls. If over 4” of slumping, consult with an engineer. Fix any erosion or scouring. If leaks, piping or soft spots are found, consult with an engineer.If liner visible on bottom, check for holes or replace.Clean any oil sheen from water with oil-absorbent pads or vactor truckChecksediment depth near inlet.If more than one footexists,or there is build upnear inlet,the pond needs to becleaned. On the pond walls, mow grass to 4 – 9”. Remove clippings. Reseed bare areas.On pond surface, emergent vegetation over 50% of the area indicates sediment removal needed.On pond bottom, remove tree seedlings.Around the pond,remove trees and shrubs that shadesidewallgrassorthatmighthaveproblemrootsnearpipes and structures.Remove invasive and poisonous plants.Remove algae if over 10% of surface.Check integrity of access ramp; ensure stable and clear for heavy equipment.Check integrity and operation of all fences, gates, and locks. Repair as needed for ease of access.Remove rodents and insects if evidence found.Remove vegetation on fences. POND COMPONENTS OF THE POND ACCESS AND SAFETY VEGETATION G-7 | Page POST CONSTRUCTION BMP INSPECTION CHECKLIST MonthlySchedule/Frequency AnnuallyAnnually Inspect pond area, sidewalls, and shoreline for erosion, settlement, and rodent damage Inspect exterior of catch basins AnnuallyAnnuallyAnnually QuarterlyMonthly and after storm events Quarterly and after storm eventsQuarterly, and after storm eventsQuarterly and after storm events Quarterly Inspect ditches, check dams, and all visible pipes and culverts for trash, obstructions and other problems Inspect bioswales for vegetation cover and bare areasInspect fences, gates and locks Quarterly Prepared by RESources for Sustainable Communities for the Birch Bay Watershed & Aquatic Resources Management (BBWARM) District. This project was been funded wholly or in part by the U.S. Environmental Protection Agency under assistance agreement WS-96073401 to Whatcom County. The content of this document do not necessarily reflect the views and policies of the Environmental Protection Agency, nor does mention of trade names or commercial products constitute endorsement or recommendations for use. Inspect pond area for oil sheens or trash Inspect access ramps for ease of heavy equipment access Inspect inside catch basins, including flow restrictor/orifice plate Inspect spillway for vegetation overgrowth and ease of heavy equipment access Inspect interior of catch basins for debris and sediment Pond area sediment accumulation (pond bottom) Inspect pond area for undesirable or poisonous vegetation and noxious weedsInspect water levels in the pondInspect trash racks, debris barriers, and energy dissipaters Inspect inlets and outlets for trash, obstructions, and vegetation Activity Semi-annually, during growing seasonAfter storm events G-5 | Page P:2021-03-17_HAVEN DRAINAGE REPORT 8 (03/17/21) JAZ/mr Appendix E GEOTECHNICAL INVESTIGATION 1091 Stoneridge Drive • Bozeman, Montana • Phone (406) 587-1115 • Fax (406) 587-9768 www.chengineers.com • E-Mail: info@chengineers.com October 28, 2019 HAVEN Attn: Erica Coyle E-mail: erica@havenmt.org RE: Soils Investigation – Lot 3A, Van Horn Subdivision; Bozeman, Montana (190488) Dear Erica, Per your request, C&H Engineering and Surveying Inc. (C&H Engineering) has conducted a subsurface soils investigation on the above referenced property. The subject property is found in the Southwest Quarter of Section 11, Township 2 South, Range 5 East in Bozeman, Montana. The scope of services was to conduct a subsurface investigation and provide a soils investigation report. The report documents the sites’ soil and groundwater conditions, subsurface soil properties, and provides foundation design and general earthwork recommendations. Proposed Construction It is understood that mixed-use structure(s) up to 3 stories in height are proposed for construction. It has been assumed that each structure will be constructed with a slab-on-grade with stem wall foundation. It has also 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 if necessary. Subsurface Soil and Conditions On October 4, 2019 Noah J. Schaible, E.I., of C&H Engineering visited the site to conduct a subsurface soils investigation. The subsurface soils investigation consisted of examining five exploratory test pit excavations. The exploratory test pits were excavated with a DEERE 410C backhoe provided by Val Mencas Excavation. The soil profiles revealed by the excavations were logged and visually classified according to ASTM D 2488, which utilizes the nomenclature of the Unified Soil Classification System (USCS). Representative samples of each soil layer were collected from the trench sidewalls at varying depths for further classification in the lab. The relative density of each soil layer was estimated based on probing of the excavation sidewalls and the overall stability of the excavation. Any evidence of seepage or other SOILS INVESTIGATION REPORT #190488 – LOT 3A, VAN HORN SUBDIVISION, BOZEMAN, MONTANA 2 groundwater conditions were also noted. The locations of the test pits are shown on the included Test Pit Location Map. The five test pits (TP) excavated for the field investigation exhibited nearly identical soil profiles. The following paragraphs briefly summarize the subsurface soils and conditions observed in the 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 test pit was a Silty Clay Organic Soil of low plasticity (OL). This material was dark brown to black in color, moist, and soft. This material was encountered to depths varying from 1.0 to 1.5 feet below grounds surface (bgs). Organic soils are highly compressible and are not suitable for foundation support. This material must also be removed from beneath all interior and exterior slabs as well as beneath all asphalt and/or concrete paving improvements. This material may be stockpiled onsite and used for final site grading purposes. The second soil horizon encountered in exploratory excavation 3 was a Clayey Gravel with Sand (GC). This material was brown in color, medium stiff, and estimated to contain approximately 25 percent fines with medium plasticity, and no dilatancy, approximately 30 percent coarse to fine grained sand, and approximately 45 percent subrounded gravels and cobbles. This material was encountered to a depth of 5.0 feet bgs. The second soil horizon encountered in exploratory excavations 1, 2, 4, 5, and the third soil horizon in exploratory excavation 3 was a Poorly Graded Gravel with Sand and Cobbles (GP). This material was brownish gray in color, dense, and estimated to contain approximately 30 percent coarse to fine grained sand, and approximately 70 percent subrounded gravels and cobbles. This material was encountered to the end of excavation, depths varying from 7 feet to 8.0 feet bgs. Based on the subsurface investigation it is recommended that all foundation footings bear on the Poorly Graded Gravel with Sand and Cobbles, or on structural fill overlying this material. This material is suitable for foundation support, provided the recommendations in this report are properly implemented. Groundwater Groundwater was encountered in all of the exploratory excavations at approximately 7.0 feet bgs. Based on our experience in the general area, it is likely that the seasonal high groundwater elevation is 3 to 4 feet below existing grade Please understand that our subsurface investigation is not a detailed groundwater study, and groundwater conditions may change dramatically due to conditions that are out of our control. Our assessment of the groundwater conditions is based on the conditions observed within the exploratory test pits on the day of the excavation, our general experience in the project area, and SOILS INVESTIGATION REPORT #190488 – LOT 3A, VAN HORN SUBDIVISION, BOZEMAN, MONTANA 3 any available literature regarding groundwater conditions in the vicinity of the subject property. If more detailed knowledge of the seasonally high groundwater elevation across the subject property is desired, it is recommended that groundwater monitoring wells installed during the field investigation be checked weekly from the early spring to late summer months. Foundation Recommendations Based on the subsurface soils and conditions encountered in the five exploratory excavations, it will be acceptable to 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 footing elevation be located a minimum of 4 feet below finished grade. • It is recommended that typical strip footings for these structures 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 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 & Settlement The bearing capacity of a soil is defined as the ultimate pressure per unit area by the foundation load 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. It is recommended that all foundation footings bear on the Poorly Graded Gravel with Sand and Cobbles, or on structural fill 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 and differential settlement were estimated using conservative soil parameters. Based on conservative soil parameter estimates, the recommended bearing capacity, and the assumption that all recommendations made in this report will be properly implemented, it is expected that total and differential settlement will be ½-inch or less. The allowable bearing capacity may be increased by one third for short term loading conditions such as those from wind or seismic forces. SOILS INVESTIGATION REPORT #190488 – LOT 3A, VAN HORN SUBDIVISION, BOZEMAN, MONTANA 4 Subgrade Preparation and Structural Fill In general, the excavation for the foundation footings must be level and uniform and continue down to the Poorly Graded Gravel with Sand and Cobbles, or to the bottom of footing elevation, whichever is deeper. If any soft spots, 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 to a distance equal to ½ the height of the required structural fill, whichever is greater. Once the excavation is completed the native soil shall be proof rolled with a large vibrating roller to an unyielding condition. Any areas that are found to be pumping or rutting shall be sub- excavated and replaced with structural fill. 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. The Poorly Graded Gravel with Sand and Cobbles may be used as structural fill, provided the material is not too moist and any particles larger than 6 inches in size are removed. Structural fill may also be imported if desired. 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. The gravel and sand particles also need to be made up of durable rock materials that will not degrade when compacted; no shale or mudstone fragments should be present. 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. 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 beginning placement of the structural fill. 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 lifts 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 SOILS INVESTIGATION REPORT #190488 – LOT 3A, VAN HORN SUBDIVISION, BOZEMAN, MONTANA 5 edge of the excavation. The native soils with the exception of the organics, are suitable for use as foundation wall backfill along the exterior of the foundation, provided they are not overly moist and the maximum particle size is not greater than 6 inches. Structural fill is recommended as foundation wall backfill in all areas that will support concrete slabs-on-grade or other paving improvements. The 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). 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. 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. • 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. Interior Slabs-on-Grade In preparation for any interior slabs-on-grade, the excavation must continue down through any overlying organic soil to a minimum of 6 inches below the proposed bottom of slab elevation. If required, structural fill can then be placed and compacted to 6 inches below the bottom of slab elevation. SOILS INVESTIGATION REPORT #190488 – LOT 3A, VAN HORN SUBDIVISION, BOZEMAN, MONTANA 6 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. 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. 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) 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 the interior slab-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, unless the slab will be supporting vehicles, then the recommended minimum thickness is 6 inches, or as directed by the structural engineer. Exterior Slabs-on-Grade For exterior areas to be paved with concrete slabs, it is recommended that, at a minimum, the topsoil and any organics be removed. The subgrade soils then need to be compacted to an unyielding condition. 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. Asphalt Paving Improvements For areas to be paved with asphalt, it is recommended that, as a minimum, the topsoil and any organics be removed. The native subgrade then needs to be rolled at ± 2 percent of its optimum moisture content to a minimum of 95 percent of its maximum dry density. Following compaction of the native subgrade a layer of woven geotextile (Mirafi 500X) shall be installed. Next a 12- SOILS INVESTIGATION REPORT #190488 – LOT 3A, VAN HORN SUBDIVISION, BOZEMAN, MONTANA 7 inch layer of compacted 6-inch minus gravel needs to be placed, followed by a 3-inch layer of compacted 1-inch minus road mix. Both gravel courses must be compacted at ± 2 percent of their optimum moisture content to a minimum of 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 a minimum of 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 as described in the section “Foundation Wall Backfill”. Construction Administration The foundation is a vital element of a structure; it transfers all of the structures 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 C&H Engineering 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 and re-evaluate our recommendations. If construction and site grading take place during cold weather, it is recommended that approved 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 The recommendations made in this report are based on information obtained from the test pits excavated at the locations shown on the included Test Pit Location Map. It is not uncommon for variations to occur between these points, the nature and extend of which do not become evident until additional exploration or construction is conducted. The variations may result in additional construction costs, and it is suggested that a contingency be provided for this purpose. This report is for the exclusive use of HAVEN. In the absence of our written approval, we make OL GP 1.0 8.0 0 TO 1 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft. 1 TO 8 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); moist;dense; approximately 70 percent subrounded gravels; approximately 30 percent fine to coarse grain sand. Bottom of test pit at 8.0 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Deere 410 C Backhoe EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS: DATE STARTED 10/4/19 COMPLETED 10/4/19 AT TIME OF EXCAVATION 7.00 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 1 PROJECT NUMBER 190488 CLIENT Haven PROJECT LOCATION Lot 3A, Van Horn Subdivision PROJECT NAME Soils Investigation Report GENERAL BH / TP / WELL - GINT STD US.GDT - 10/27/19 16:48 - G:\C&H\19\190488\GEOTECHNICAL\TEST PIT LOGS\190488.GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL GP 1.0 7.0 0 TO 1 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft. 1 TO 7 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); moist;dense; approximately 70 percent subrounded gravels; approximately 30 percent fine to coarse grain sand. Bottom of test pit at 7.0 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Deere 410 C Backhoe EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS: DATE STARTED 10/4/19 COMPLETED 10/4/19 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 2 PROJECT NUMBER 190488 CLIENT Haven PROJECT LOCATION Lot 3A, Van Horn Subdivision PROJECT NAME Soils Investigation Report GENERAL BH / TP / WELL - GINT STD US.GDT - 10/27/19 16:48 - G:\C&H\19\190488\GEOTECHNICAL\TEST PIT LOGS\190488.GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL GC GP 1.0 5.0 8.0 0 TO 1 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft. 1 TO 5 FEET: CLAYEY GRAVEL WITH SAND; (GC); brown; moist; medium plasticity; nodiltancy; medium stiff; approximately 45 percent subrounded gravels; approximately 30 percent fine to coarse grain sand; approximately 25 percent clayey fines. 5 TO 8 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); moist; dense; approximately 70 percent subrounded gravels; approximately 30 percent fine to coarse grain sand. Bottom of test pit at 8.0 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Deere 410 C Backhoe EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS: DATE STARTED 10/4/19 COMPLETED 10/4/19 AT TIME OF EXCAVATION 7.00 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 3 PROJECT NUMBER 190488 CLIENT Haven PROJECT LOCATION Lot 3A, Van Horn Subdivision PROJECT NAME Soils Investigation Report GENERAL BH / TP / WELL - GINT STD US.GDT - 10/27/19 16:48 - G:\C&H\19\190488\GEOTECHNICAL\TEST PIT LOGS\190488.GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL GP 1.5 8.0 0 TO 1.5 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft. 1.5 TO 8 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); moist; dense; approximately 70 percent subrounded gravels; approximately 30 percent fine tocoarse grain sand. Bottom of test pit at 8.0 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Deere 410 C Backhoe EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS: DATE STARTED 10/4/19 COMPLETED 10/4/19 AT TIME OF EXCAVATION 7.00 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 190488 CLIENT Haven PROJECT LOCATION Lot 3A, Van Horn Subdivision PROJECT NAME Soils Investigation Report GENERAL BH / TP / WELL - GINT STD US.GDT - 10/27/19 16:48 - G:\C&H\19\190488\GEOTECHNICAL\TEST PIT LOGS\190488.GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION OL GP 1.0 8.0 0 TO 1 FEET: ORGANIC SOIL; (OL); dark brown to black; moist; soft. 1 TO 8 FEET: POORLY GRADED GRAVEL WITH SAND AND COBBLES; (GP); moist;dense; approximately 70 percent subrounded gravels; approximately 30 percent fine to coarse grain sand. Bottom of test pit at 8.0 feet. NOTES GROUND ELEVATION LOGGED BY Noah J. Schaible, E.I. EXCAVATION METHOD Deere 410 C Backhoe EXCAVATION CONTRACTOR Val Mencas Excavation, LLC GROUND WATER LEVELS: DATE STARTED 10/4/19 COMPLETED 10/4/19 AT TIME OF EXCAVATION 7.00 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 5 PROJECT NUMBER 190488 CLIENT Haven PROJECT LOCATION Lot 3A, Van Horn Subdivision PROJECT NAME Soils Investigation Report GENERAL BH / TP / WELL - GINT STD US.GDT - 10/27/19 16:48 - G:\C&H\19\190488\GEOTECHNICAL\TEST PIT LOGS\190488.GPJU.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION