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HomeMy WebLinkAboutStormwaterDR resubmittal pkg 073021190 NORTHSTAR LANE BOZEMAN, MT 59718 406-581-5730 www.headwatersmt.net Page 1 of 8 Storm Water Management Design Report Gallatin Park Mixed Use 325 Gallatin Park Drive Bozeman, Montana July 2021 Headwaters Engineering, Inc. Project #: 1204.001 Prepared For: RB53, LLC 510 West Hemlock Bozeman, MT 59715 190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 2 of 8 Storm Water Management Design Report Table of Contents I. Project Background……………………………………………………………………………………………….. 3 1. Introduction………………………………………………………………………………………………………………. 3 2. Soil and Groundwater……………………………………………………………………………………………….. 3 3. Land Use……………………………………………………………………………………………………………………. 3 II. Existing Conditions…………………………………………………..………………………………………………. 4 1. Drainage Basins and Pre-Development Peak Flows…………………………………………………… 4 III. Proposed Drainage Plan and Post-Development Peak Flows…………………………………. 4 1. Major Drainage System…………………………………………………………………………………………….. 5 2. Minor Drainage System…………………………………………………………………………………………….. 5 3. Initial Stormwater Facility and Initial Abstraction………………………………………………………. 6 4. Maintenance…………………………………………………………………………………………………………….. 6 IV. Conclusion………………………………………………………………………………………….……………………. 7 List of Tables Table 1. Estimated Pre-Development Peak Flows……………………………………………………………………….. 5 Table 3. Estimated Post-Development Peak Flows……………………………………………………………………… 5 Table 4. Required Pond Volumes ……………………………………..………………………………………………………… 5 Table 5. Proposed Drainage Conveyance Structures Capacities …………………………………………………… 6 Appendix A—Calculations Grading and Drainage Exhibits Pre/Post Development Drainage Basin Flows Conveyance Structure Modeling Storm Pond Calculations List of References City of Bozeman Design Standards and Specifications Policy, March 2004, and all addenda. Gallatin Park Subdivision Design Report – Appendix E (1999 TD&H) 190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 3 of 8 I. Project Background Introduction The Gallatin Park Mixed Use Project consists of 4 buildings with a total of 13 residential units on the second floor and 13 commercial units on the main floor. The site is on the 1.061-acre Lot 4A of the Amended Plat of Lot 3 & Lot 4 of Block 1 of the Gallatin Park Subdivision. The existing lot covers approximately 3.07 acres in Section 2, T2S, R5E, PMM in Bozeman, Gallatin County, Montana. This design report outlines the storm water analysis conducted for the site and describes the storm water drainage and management facilities required for the Gallatin Park Mixed Use project by state and local regulations. The storm water plan follows the design standards set forth by the City of Bozeman in Design Standards and Specifications Policy, March 2004 and subsequent addenda. Soil and Groundwater The NRCS Soil Survey identifies the major soil type on the site to be Turner loam (457A). These soils belong to hydrologic soil group B as they are comprised primarily of loams and silt loams with moderately high saturated hydraulic conductivity. A geotechnical investigation by Caste Rock Geotechnical Engineering on November 4th, 2019, mentioned finding groundwater at roughly five-foot-deep in the three test pits dug onsite. The presence of groundwater will likely affect construction methods. Groundwater was roughly 5.0’ below the ground surface and the bio- retention island is set roughly 9 inches above native ground, therefore groundwater will not be an issue for the bioretention pond. An additional test pit was excavated on the northeast edge of the property on June 3rd, 2021 and the groundwater level matched the water level in the existing regional storm pond. The existing regional storm pond is a detention pond where the water level is set by the elevation of the outlet structure. The regional storm pond volumes were calculated using the available volume above the outlet structure elevation. All of the stormwater from the site will flow to the existing regional storm pond. The front of the lot has a small area which will flow towards Gallatin Park Drive. As shown in Figure 2, the water from Gallatin Park Drive flows generally north where it is collected by a curb inlet and discharged into the Regional Storm Pond. Land Use The pre-development land use on the site was vacant lot from the Gallatin Park Subdivision in 2000. The land is currently zoned M-1 and the proposed use is for commercial units with residential units on the second story. Figure 1 – Vicinity map of 5-acre Offsite basin OSA 190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 4 of 8 Figure 2 – Storm Flow – Gallatin Park Drive II. Existing Conditions The Gallatin Park Mixed Use project lies between Gallatin Park Drive and a natural low area which encompasses the existing regional storm pond. The project’s land slopes generally to the northeast at a grade of approximately 2%. The existing high point of the property is located on the south boundary with the low point in the north corner of the parcel. The existing grading pushed all runoff from the site naturally to the existing regional storm pond on the north boundary. The overflow from the regional storm pond must overtop Gallatin Park Drive and flow to the northwest, ultimately to the East Gallatin River. The overtopping elevation of Gallatin Park Drive is 4686.0. This leaves 2.4’ from the maximum water level of the regional storm pond and building 2 first floor elevation. Drainage Basins and Pre-development Peak Flows Headwaters has identified the major contributing drainage basin from lands offsite and one onsite drainage basin as shown on drawing C-4 and the Basin Exhibit found in Appendix A. The 5-acre off-site basin stretches from the southwest from the property to the centerline of the railroad tracks, roughly 600’ away. Estimate of runoff and their respective calculations for the existing drainage basin was completed using the Modified Rational Method. The offsite basin model uses a pre-development runoff coefficient C = 0.20 which does not necessarily represent the typical ground cover we see today. The onsite basin also uses a pre-development runoff coefficient of C = 0.20. Given the size of the existing offsite basin, and possible future development, a runoff coefficient of C=0.70 was used for post development. Several storm event return intervals such as the 10-year, 25-year and 100-yr were used in the analysis of the existing storm water conveyance structures in or near the site. A summary of estimated pre-development 190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 5 of 8 peak runoff rates as well as existing drainage conveyance structure capacities can be found in Tables 1 and 2. Detailed calculations are available in Appendix A. Table 1. Estimated Pre-Development Peak Flows (see GD-1) Sub Area Description Area Tc Q10 Q25 Q100 (acres) (min) (cfs) (cfs) (cfs) OSA Offsite Basin - Rational 5 30 1.0 1.2 1.6 B Onsite Basin - Rational 1.06 20 0.34 0.54 III. Proposed Drainage Plan and Estimated Post-Development Peak Flows The proposed drainage plan will build off of the existing or natural drainage system in place. Headwaters’ drainage plan consists of two separate drainage systems. First, the major drainage system or backbone is designed to have a much higher conveyance capacity and shall convey the excess runoff from the 100-year storm without inundating any building structures. Secondly, the minor drainage system fits within the major drainage system and feeds into it. The minor drainage system(s) are designed to accommodate moderate and relatively frequent storm events without inconveniencing the public. The minor system is comprised of the streets, sidewalk chases, and swales designed to convey runoff from the 10 & 25-year events, and retention or detention ponds designed to attenuate the 10-year storm event. Table 3 presents a summary of the expected post-development peak flow rates passing through the proposed project. Appendix E of the Subdivision’s Design Report also addresses storm water. Table 3. Estimated Post-Development Peak Flows (see GD-1) Sub Area Description Area C Tc Q10 Q25 Q100 (acres) (min) (cfs) (cfs) (cfs) OSA Offsite Basin 5 0.70* 25 4.0 4.8 6.4 B Onsite Basin 1.06 0.73 15 1.24 2.0 B 10yr 24hr flow 1.06 0.73 1440 0.06 * The remaining lands not currently developed in the 5-acre basin are modeled as developed (C=0.70) for the future event. Major Drainage System The major drainage system in the area is comprised of the natural low area which contains the regional storm pond and which has a controlled outlet and 36” arch pipe to the north. If the storm exceeds the outlet structure capacity, which was to be designed to handle the 25-year flow, it will fill the pond and top Gallatin Park Drive. As discussed above, any overflow water will overtop Gallatin Park Drive at an elevation of 4686.0 which leaves 2.4’ of freeboard on the lowest building first floor. After overtopping Gallatin Park Drive, the natural drainage will carry it to the East Gallatin River as the water has historically traveled. Site grading onsite shall be completed so that any runoff resulting from storm events greater than the 10-year and less than the 100-year will flow through parking lots and down conveyance swales without inundating any structures or causing significant erosion onsite. The 100-year onsite event of 1.2 cfs will flow through the parking lot and out of the curb cut without inundating the first floor of any building. Minor Drainage System The proposed minor drainage system includes interior parking lot sheet flow into the existing regional detention pond as well as one small bioretention pond. The pond locations are shown on the attached “Basin Map”. The City of Bozeman Design Standards and Specifications Policy requires that detention pond volume be adequate to accommodate the difference in peak runoff between the pre-development and post- development design storm of 10 years, while retention ponds must contain the entire 10-year 2-hour design storm volume. Table 4 shows the calculated pond volumes. Since the impervious area exceeds the originally 190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 6 of 8 contemplated area for this site, we added the small bio-retention pond. The originally contemplated runoff coefficient was 0.70 and the design is 0.73. The existing pond design was also verified using current standards. The extra capacity in the existing pond more than accommodates the difference in proposed impervious area onsite, or will allow for 0.1’ of groundwater to pool above the outlet structure due to plugging or release rate. Table 4. Pond Volumes Pond Type Location Contributing Volume Subarea (cft) B Detention Site’s Contribution(0.73) B 827cf (actual flows from site) B Detention Designed at Runoff Coeff. = 0.70 w/ subdivision 765cf (portion of pond allocated to this site) B Bio-Retention Middle B 100cf (Additional pond to make up difference) 1 Detention Regional 23.3 ac 23,724 cf (Regional Size w/ current stds) 1 Detention Design Size 24,146 cf (Pond size per as-builts) It is required that retention ponds and storage structures drain to prevent long-term standing water. The bioretention pond is to have a 12” washed rock base placed on native soils (silt loam). The silt loam has an infiltration rate per DEQ 8 of 0.7 inches per hour. Since the bioretention pond is 6” deep, it will take 8.6 hours for the surface water to drain from the bioretention pond. The Contech CDS Separator is designed to always hold water between the outlet pipe elevation and the sediment storage. The separator will handle back to back storms without reduced settling ability. The curb and gutter in the parking lot will direct the runoff to the curb cut which empties to the 2’ swale and flows thru a hydrodynamic separator before flowing to the existing regional detention pond. The proposed curb cut has a capacity of 2.6 cfs which passes the 100-year onsite storm event without overtopping the curb. The separator will also treat the first 0.5” of precipitation from a 24-hour storm. Table 5. Proposed Drainage Conveyance Structure Capacity Description Contributing Depth Slope Q10PST Q25PST Q100PST Capacity Passes Subareas (ft) (%) (cfs) (cfs) (cfs) (cfs) Design Storm Curb & Gutter B 0.50 0.5 0.74 1.2 4.2 Y 24” Curb Cut B 0.40 0.5 0.74 1.2 2.6 Y 8” Separator Pipe B(24 hr) 0.67 0.5 0.06 1.13 Y Initial Stormwater Facility and Initial Abstraction The latest version of DEQ 8 as well as the City of Bozeman requires that the first 0.5 inch of precipitation must be captured and not be allowed to become direct runoff. Since the existing regional storm pond was designed before this requirement, this was not likely addressed. The bioretention pond will retain and infiltrate the flow captured, thus meeting initial abstraction requirements. The remaining flow from the 0.5 inch storm runoff from a 24 hour storm will be treated using the proposed Contech CDS hydrodynamic separator which is designed to remove 80% of TSS. Maintenance Regular maintenance of storm water facilities is necessary for proper functioning of the drainage system. In general, regular mowing of any grass swales and unclogging of curb cuts and curb lines be required to prevent standing water and clogging. More substantial maintenance, such as sediment removal with heavy equipment, may be required in coming decades to restore pond volume and swale function. Sediment removal from the regional storm pond is the responsibility of the Gallatin Park Subdivision Owners Association.. The Hydrodynamic Separator is to be visually inspected every 6 months to check for build-up of sediment in the bottom of the unit. If the sediment depth exceeds 75% of the sump depth or 18 inches deep, the sediment is to be removed using a vac-truck to suck out the sediment and dispose of it at a disposal site. The sediment 190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 7 of 8 depth can also be measured from the top of the unit. If the sediment is measured to be 5.7’ or less below the top of the separator unit, then the sediment needs to be removed. Floatables (trash) are to be netted out and disposed of prior to removing sediment with the vac-truck. Any oils or hydrocarbons are to be removed using absorbent pads prior to vac-trucking out the sediment. Reference the Contech CDS Inspection and Maintenance Guide for additional details. All maintenance and repair should be prioritized and scheduled in advance. Structure & pipes should be visually inspected yearly. Typical maintenance items include removing obstructions, cleaning and flushing pipes, mowing grass and weeds, tree maintenance to prevent limbs from falling and blocking swales, and establishing groundcover on bare ground. See the Stormwater Maintenance Manual filed at the Courthouse for additional information. IV. Conclusion Storm water analysis and calculations indicate that the proposed storm water management plan for the Gallatin Park Mixed Use project is adequate to safely convey the 10-year, 25-year, and 100-year storm events while satisfying state and local regulations for peak attenuation and stormwater storage. Furthermore, the proposed first floor elevations for the structures are all above the estimated 100-yr Base flood Elevation as determined by Headwaters Engineering. H:\1204\001\DOCS\Design\Storm\StormwaterDR.doc 190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 8 of 8 Appendix A Exhibits & Calculations & O&M WSWSWSSS SSSSSSSSSSSSSS SS E E GGGG G G G EWSWSWSWSWSWSWSWSWSWSWSWSEEE E E E E EEEEEEE E EEEEE T T T T T T G G G G G 8 SS 8 SS 8 SS 8 SS 8 SS 8 W 8 W 8 W 8 W 8 W N GRAPHIC SCALE 1 inch = ft. 0 ( IN FEET ) 20 40 40 DRAWN BY: DATE: Plot Date: 6/9/2021 5:25 PM H:\1204\001\ACAD\SHEETS\BASINS.dwg REVISION DATE: 190 NORTHSTAR LANE, BOZEMAN, MT 59718 HEADWATERSMT.NET 406-581-5730 PROJECT #: LOCATION: GALLATIN PARK MIXED USE BASIN MAP JRM 03/2021 06/2021 1204.001 BOZEMAN BASIN B GALLATIN PARK DRIVE REGIONAL STORM POND 100 CF BIORETENTION POND 11"X17": 1"= 40 ftN GRAPHIC SCALE1 inch = ft.0( IN FEET )10202020HEADWATERSPROJECT NUMBERDRAWING NUMBERDRAWN BY:DATE:2021VERIFY SCALETHESE PRINTS MAY BEREDUCED. LINE BELOWMEASURES ONE INCH ONORIGINAL DRAWING. MODIFY SCALE ACCORDINGLYH:\1204\001\ACAD\SHEETS\C4-GRADING.dwg Plot Date: 6/10/2021 8:42 AM© HEADWATERS ENGINEERING, INC.REVISION DATE:190 NORTHSTAR LANE, BOZEMAN, MT 59718HEADWATERSMT.NET406-581-5730PROJECT LOCATIONC-41204.001GALLATIN PARK MIXED USE325 GALLATIN PARK DRIVEGRADING PLANJRM03/23/2106/11/21BOZEMANMONTANAGALLATIN PARK DRIVE3' SIDE SETBACK 3' REAR SETBACKBUILDING 2SLAB ELEV=4690.10BUILDING 3SLAB ELEV=4691.30EXISTING 1" WATER SVC PRIVATE OPENSPACE BLOT 2BLOCK 1LOT 5BLOCK 1PRIVATE OPENSPACE BEXISTING REGIONAL STORM PONDSURFACE FLOW OF STORMWATER TO EXISTING REGIONALSTORM POND (GALLATIN PARKSUBDIVISION)5'X6" CONCRETE CROSSWALK W/ REBAR 18" O.C.7.0' THICKENED EDGE WALK 7' WALK 5' SIDEWALK5' SIDEWALK5'X6" CONCRETE CROSSWALK W/ REBAR 18" O.C.GALLATIN PARK DRIVETRUNCATED DOME, TYPFLOW-THRUCURBGARAGE DOOR,TYP100 CF, 132 SFBIORETENTION AREA, SEEDETAIL ON SHEET C-6PROPOSED BOULDERRETAINING WALL, SEEDETAIL, SHEET C-6EXISTING 5' SIDEWALKREPLACE 4" SIDEWALKWITH 6" SIDEWALKW/REBAR 18" O.C.GARAGE DOOR, TYP6" CONC. W/FIBERMESH IN FRONT OFGARAGE DOORS, TYP.6" CONC. W/FIBERMESH IN FRONT OFGARAGE DOORS, TYP.6" SIDEWALKCURB6" SIDEWALKCURBGARAGE DOOR,TYPEXISTING 5' SIDEWALKACCESSIBLEPARKINGSTRIPINGNOTES:1. ALL TBC RADII ARE 3.0' UNLESS OTHERWISE NOTED.2. ALL CURB & GUTTER SHALL INSTALLED PER DETAIL ONSHEET C-3.3. SEE LANDSCAPE PLAN FOR LOCATION OF PROPOSEDLANDSCAPING.4. CATCH TBC=FLAG + 0.40'5. SPILL TBC = FLAG + 0.55'6. TRANS TBC = FLAG + 0.45'7. SP=SPILL, LOW=LOW POINT, HI=HIGH POINT, GB=GRADEBREAK, CA=CATCH, TBC=TOP BACK CURB, SW=SIDEWALK.8. THE CONTRACTOR IS TO VERIFY THE CROSS WALKS ANDACCESSIBLE PARKING SPACES HAVE A CROSS SLOPE LESSTHAN 2% PRIOR TO PAVING.PROPERTY BOUNDARY PROPERTY BOUNDARY PROPERTY BOUNDARY2.0%MAX2.0%MAXPAVE=87.76TBC=88.16BUILDING 1 GARAGE DOORRAMPS ARE ALL TYPE 1BUILDING 2 GARAGE DOORRAMPS ARE ALL TYPE 2BUILDING 3 GARAGE DOORRAMPS ARE ALL TYPE 3REPLACE 4" SIDEWALKWITH 6" SIDEWALKW/REBAR 18" O.C.REMOVE & REPLACEW/ LAYDOWN CURBREMOVE & REPLACEW/ LAYDOWN CURB5' TAPER, TYP5' TAPER, TYP91.090.590.08 9 . 5 89. 0 89.5 88 . 5 88.0 87.5 87.0 88.589.089.589.089 . 512"X8' SIDEWALK CHASE12"X8' SIDEWALK CHASE9 0 . 0 9 0 . 5 9 1 . 0 9 1 . 5 92. 0 89 . 0CLUSTERMAILBOXLAYDOWN CURB8%RAMP8%RAMP8%RAMP8%RAMP8%RAMP8%RAMP2.0%MAX24" CURB CUTLANDSCAPEROCK ON FABRIC2.0%MAX 2.0%MAXRAMPRAMPRAMP RAMPRAMPRAMPRAMP2.0%MAX8%RAMP8%RAMPLANDINGLANDINGRAMPRAMPRAMPRAMP2.0%MAX2.0%MAX2.0%MAX0.5%0.5%1.17%1.0%5.0%2' TAPER, TYP2' TAPER, TYPLAYDOWN CURBBUILDING 1ASLAB ELEV=4688.40BUILDING 1BSLAB ELEV=4689.00BUILDING 1 GARAGE DOORRAMPS ARE ALL TYPE 1TOP WALL=4692.0TOP WALL=4692.0PAVE=88.050.1' LIP0.1' LIP0.1' LIP0.1' LIP0.1' LIP0.1' LIP0.1' LIPPAVE=88.28TBC=88.68PAVE=88.50PAVE=88.70TBC=89.0PAVE=89.15TBC=89.700.1' LIP0.1' LIP 0.1' LIP0.1' LIPPAVE=89.15TBC=89.70PAVE=89.00TBC=89.5018" CURB CUTPAVE=89.55TBC=90.00BSW=91.87PAVE=89.00BSW=90.07PAVE=89.77PAVE=89.45TBC=89.95PAVE=89.50TBC=90.00AAOVERFLOW=89.0STORM SWALETO PONDTYPE 1WHEELCHAIRRAMPTYPE 2WHEELCHAIR RAMPTYPE 2WHEELCHAIR RAMP6'X10' BIKE PAD6'X8' BIKE PAD0.5%HYDRODYNAMICSEPARATOREXISTING POND OUTLETSTRUCTURE HW#: DATE: ENGINEER: RAINFALL FREQ =10 YR (DURATION = 1) BASIN AREA PRE =5 AC STORM EVENT INTENSITY(YR)A B (IN/HR) PRE-DEV Tc =30.0 MIN 0.50 2 0.36 0.6 0.55 5 0.52 0.64 0.81PRE-DEV C =0.20 10 0.64 0.66 1.01250.78 0.64 1.22 STORM A =0.64 50 0.92 0.66 1.45 B =0.66 100 1.01 0.67 1.61 STORM INTENSITY =1.01 IN/HR PRE-DEV Qp =1.01 CFS BASIN AREA PRE =5 AC POST-DEV Tc =25.0 MIN 0.00 POST-DEV C =0.7 STORM INTENSITY =1.14 IN/HR POST-DEV Qp =3.99 CFS Gallatin Park Mixed Use JRM 3/16/2021 POST-DEVELOPMENT Qp = C i A Offsite Basin A i = A * (Tc/60) -B STORM i COEFF PRE-DEVELOPMENT MODIFIED RATIONAL METHOD (CITY OF BOZEMAN) H:\1204\001\DOCS\Design\Storm\OS-A 1 OF 1 PRINTED: 3/16/2021 HW#: DATE: ENGINEER: RAINFALL FREQ =25 YR (DURATION = 1) BASIN AREA PRE =5 AC STORM EVENT INTENSITY(YR)A B (IN/HR) PRE-DEV Tc =30.0 MIN 0.50 2 0.36 0.6 0.55 5 0.52 0.64 0.81PRE-DEV C =0.20 10 0.64 0.66 1.01250.78 0.64 1.22 STORM A =0.78 50 0.92 0.66 1.45 B =0.64 100 1.01 0.67 1.61 STORM INTENSITY =1.22 IN/HR PRE-DEV Qp =1.22 CFS BASIN AREA PRE =5 AC POST-DEV Tc =25.0 MIN 0.00 POST-DEV C =0.7 STORM INTENSITY =1.37 IN/HR POST-DEV Qp =4.78 CFS PRE-DEVELOPMENT MODIFIED RATIONAL METHOD (CITY OF BOZEMAN)i = A * (Tc/60) -B STORM i COEFF Gallatin Park Mixed Use JRM 3/16/2021 POST-DEVELOPMENT Qp = C i A Offsite Basin A - 25 yr H:\1204\001\DOCS\Design\Storm\OS-A 1 OF 1 PRINTED: 3/16/2021 HW#: DATE: ENGINEER: RAINFALL FREQ =100 YR (DURATION = 1) BASIN AREA PRE =5 AC STORM EVENT INTENSITY(YR)A B (IN/HR) PRE-DEV Tc =30.0 MIN 0.50 2 0.36 0.6 0.55 5 0.52 0.64 0.81PRE-DEV C =0.20 10 0.64 0.66 1.01250.78 0.64 1.22 STORM A =1.01 50 0.92 0.66 1.45 B =0.67 100 1.01 0.67 1.61 STORM INTENSITY =1.61 IN/HR PRE-DEV Qp =1.61 CFS BASIN AREA PRE =5 AC POST-DEV Tc =25.0 MIN 0.00 POST-DEV C =0.7 STORM INTENSITY =1.82 IN/HR POST-DEV Qp =6.36 CFS PRE-DEVELOPMENT MODIFIED RATIONAL METHOD (CITY OF BOZEMAN)i = A * (Tc/60) -B STORM i COEFF Gallatin Park Mixed Use JRM 3/16/2021 POST-DEVELOPMENT Qp = C i A Offsite Basin A - 100 yr H:\1204\001\DOCS\Design\Storm\OS-A.xls 1 OF 1 PRINTED: 6/10/2021 HW#: DATE: ENGINEER: RAINFALL FREQ =10 YR (DURATION = 1) BASIN AREA PRE =23.3 AC STORM EVENT INTENSITY(YR)A B (IN/HR) PRE-DEV Tc =40.0 MIN 0.67 2 0.36 0.6 0.46 5 0.52 0.64 0.67PRE-DEV C =0.20 10 0.64 0.66 0.84250.78 0.64 1.01 STORM A =0.64 50 0.92 0.66 1.20 B =0.66 100 1.01 0.67 1.33 STORM INTENSITY =0.84 IN/HR PRE-DEV Qp =3.90 CFS POND VOLUME: BASIN AREA PRE =23.3 AC POST-DEV Tc =40.0 MIN 0.00 DETENTIONPOST-DEV C =0.7 STORM INTENSITY =0.84 IN/HR POST-DEV Qp =13.64 CFS 1204.001 JRM 6/3/2021 POST-DEVELOPMENT Qp = C i A CONST.RELEASE GALLATIN PARK REGIONAL POND 1 i = A * (Tc/60) -B STORM i COEFF (CF) 17749.49 TRIANGLE RELEASE (CF) PRE-DEVELOPMENT MODIFIED RATIONAL METHOD (CITY OF BOZEMAN) AVERAGE VOLUME(CF) 23424.06 29098.63 H:\1204\001\DOCS\Design\Storm\CityofBozeman Pond Regional.xls 1 OF 2 PRINTED: 6/10/2021 POND VOLUME CALC'S Triangle Release Constant Release DURATION INTENSITY Qp POND VOLUME POND VOLUME (MIN)(IN/HR)(CFS)(CF)(CF) 38.00 0.87 14.11 23052.84 16516.30 39.00 0.85 13.87 23221.32 16612.52 40.00 0.84 13.64 23385.00 16703.5741.00 0.82 13.42 23544.09 16789.65 42.00 0.81 13.21 23698.78 16870.96 43.00 0.80 13.01 23849.22 16947.6844.00 0.79 12.81 23995.60 17019.9945.00 0.77 12.62 24138.05 17088.05 46.00 0.76 12.44 24276.73 17152.01 47.00 0.75 12.26 24411.77 17212.0248.00 0.74 12.09 24543.29 17268.2149.00 0.73 11.93 24671.42 17320.7150.00 0.72 11.77 24796.27 17369.66 51.00 0.71 11.62 24917.95 17415.15 52.00 0.70 11.47 25036.56 17457.3053.00 0.69 11.33 25152.20 17496.22 54.00 0.69 11.19 25264.97 17532.01 55.00 0.68 11.06 25374.94 17564.7556.00 0.67 10.92 25482.20 17594.5457.00 0.66 10.80 25586.84 17621.47 58.00 0.65 10.67 25688.93 17645.61 59.00 0.65 10.55 25788.54 17667.0460.00 0.64 10.44 25885.74 17685.8561.00 0.63 10.33 25980.60 17702.09 62.00 0.63 10.21 26073.18 17715.84 63.00 0.62 10.11 26163.54 17727.1664.00 0.61 10.00 26251.74 17736.1365.00 0.61 9.90 26337.83 17742.78 66.00 0.60 9.80 26421.88 17747.19 67.00 0.60 9.71 26503.92 17749.41 68.00 0.59 9.61 26584.01 17749.49 69.00 0.58 9.52 26662.20 17747.48 70.00 0.58 9.43 26738.54 17743.4371.00 0.57 9.34 26813.06 17737.4072.00 0.57 9.25 26885.81 17729.4273.00 0.56 9.17 26956.82 17719.53 74.00 0.56 9.09 27026.15 17707.79 75.00 0.55 9.01 27093.82 17694.2376.00 0.55 8.93 27159.88 17678.8977.00 0.54 8.85 27224.35 17661.81 78.00 0.54 8.78 27287.27 17643.03 GALLATIN PARK REGIONAL POND 1 H:\1204\001\DOCS\Design\Storm\CityofBozeman Pond Regional.xls 2 OF 2 PRINTED: 6/10/2021 HW#: DATE: ENGINEER: RAINFALL FREQ =10 YR (DURATION = 1) BASIN AREA PRE =1.063 AC STORM EVENT INTENSITY(YR)A B (IN/HR) PRE-DEV Tc =15.0 MIN 0.25 2 0.36 0.6 0.83 5 0.52 0.64 1.26PRE-DEV C =0.20 10 0.64 0.66 1.60250.78 0.64 1.89 STORM A =0.64 50 0.92 0.66 2.30 B =0.66 100 1.01 0.67 2.56 STORM INTENSITY =1.60 IN/HR PRE-DEV Qp =0.34 CFS POND VOLUME: BASIN AREA PRE =1.063 AC POST-DEV Tc =15.0 MIN 0.00 DETENTIONPOST-DEV C =0.7 STORM INTENSITY =1.60 IN/HR POST-DEV Qp =1.19 CFS PRE-DEVELOPMENT MODIFIED RATIONAL METHOD (CITY OF BOZEMAN) AVERAGE VOLUME(CF) 765.61 951.08 i = A * (Tc/60) -B STORM i COEFF (CF) 580.15 TRIANGLE RELEASE (CF) 1204.001 JRM 6/3/2021 POST-DEVELOPMENT Qp = C i A CONST.RELEASE REGIONAL POND 1-Onsite Portion 0.70 H:\1204\001\DOCS\Design\Storm\CityofBozeman Pond Regiona-Onsite 0.70.xls1 OF 2 PRINTED: 6/10/2021 POND VOLUME CALC'S Triangle Release Constant Release DURATION INTENSITY Qp POND VOLUME POND VOLUME (MIN)(IN/HR)(CFS)(CF)(CF) 14.25 1.65 1.23 753.48 539.83 15.25 1.58 1.18 767.82 547.85 16.25 1.52 1.13 781.12 554.7417.25 1.46 1.08 793.48 560.61 18.25 1.40 1.04 805.00 565.57 19.25 1.36 1.01 815.75 569.6820.25 1.31 0.98 825.78 573.0321.25 1.27 0.94 835.17 575.67 22.25 1.23 0.92 843.97 577.66 23.25 1.20 0.89 852.20 579.0424.25 1.16 0.87 859.92 579.8625.25 1.13 0.84 867.16 580.1526.25 1.10 0.82 873.95 579.94 27.25 1.08 0.80 880.32 579.28 28.25 1.05 0.78 886.29 578.1729.25 1.03 0.77 891.88 576.66 30.25 1.01 0.75 897.13 574.76 31.25 0.98 0.73 902.04 572.4932.25 0.96 0.72 906.64 569.8833.25 0.94 0.70 910.93 566.93 34.25 0.93 0.69 914.94 563.67 35.25 0.91 0.68 918.69 560.1136.25 0.89 0.66 922.17 556.2637.25 0.88 0.65 925.40 552.14 38.25 0.86 0.64 928.40 547.75 39.25 0.85 0.63 931.18 543.1240.25 0.83 0.62 933.73 538.2441.25 0.82 0.61 936.08 533.14 42.25 0.81 0.60 938.24 527.81 43.25 0.79 0.59 940.20 522.27 44.25 0.78 0.58 941.97 516.53 45.25 0.77 0.57 943.57 510.59 46.25 0.76 0.57 945.00 504.4647.25 0.75 0.56 946.26 498.1448.25 0.74 0.55 947.37 491.6549.25 0.73 0.54 948.32 484.98 50.25 0.72 0.54 949.12 478.15 51.25 0.71 0.53 949.78 471.1652.25 0.70 0.52 950.30 464.0153.25 0.69 0.52 950.68 456.71 54.25 0.68 0.51 950.94 449.26 REGIONAL POND 1-Onsite Portion 0.70 H:\1204\001\DOCS\Design\Storm\CityofBozeman Pond Regiona-Onsite 0.70.xls2 OF 2 PRINTED: 6/10/2021 HW#: DATE: ENGINEER: RAINFALL FREQ =10 YR (DURATION = 1) BASIN AREA PRE =1.063 AC STORM EVENT INTENSITY(YR)A B (IN/HR) PRE-DEV Tc =15.0 MIN 0.25 2 0.36 0.6 0.83 5 0.52 0.64 1.26PRE-DEV C =0.20 10 0.64 0.66 1.60250.78 0.64 1.89 STORM A =0.64 50 0.92 0.66 2.30 B =0.66 100 1.01 0.67 2.56 STORM INTENSITY =1.60 IN/HR PRE-DEV Qp =0.34 CFS POND VOLUME: BASIN AREA PRE =1.063 AC POST-DEV Tc =15.0 MIN 0.00 DETENTIONPOST-DEV C =0.73 STORM INTENSITY =1.60 IN/HR POST-DEV Qp =1.24 CFS 1204.001 JRM 6/3/2021 POST-DEVELOPMENT Qp = C i A CONST.RELEASE REGIONAL POND 1-Onsite Portion 0.73 i = A * (Tc/60) -B STORM i COEFF (CF) 630.22 TRIANGLE RELEASE (CF) PRE-DEVELOPMENT MODIFIED RATIONAL METHOD (CITY OF BOZEMAN) AVERAGE VOLUME(CF) 826.89 1023.56 H:\1204\001\DOCS\Design\Storm\CityofBozeman Pond Regiona-Onsite 0.73.xls1 OF 2 PRINTED: 6/10/2021 POND VOLUME CALC'S Triangle Release Constant Release DURATION INTENSITY Qp POND VOLUME POND VOLUME (MIN)(IN/HR)(CFS)(CF)(CF) 14.25 1.65 1.28 798.55 581.43 15.25 1.58 1.23 813.94 590.34 16.25 1.52 1.18 828.25 598.0817.25 1.46 1.13 841.58 604.77 18.25 1.40 1.09 854.02 610.50 19.25 1.36 1.05 865.67 615.3720.25 1.31 1.02 876.57 619.4421.25 1.27 0.99 886.80 622.78 22.25 1.23 0.96 896.40 625.44 23.25 1.20 0.93 905.43 627.4824.25 1.16 0.90 913.92 628.9325.25 1.13 0.88 921.90 629.8326.25 1.10 0.86 929.42 630.22 27.25 1.08 0.84 936.50 630.13 28.25 1.05 0.82 943.16 629.6029.25 1.03 0.80 949.43 628.63 30.25 1.01 0.78 955.34 627.27 31.25 0.98 0.76 960.90 625.5232.25 0.96 0.75 966.13 623.4233.25 0.94 0.73 971.05 620.97 34.25 0.93 0.72 975.67 618.20 35.25 0.91 0.71 980.01 615.1236.25 0.89 0.69 984.07 611.7437.25 0.88 0.68 987.88 608.07 38.25 0.86 0.67 991.45 604.14 39.25 0.85 0.66 994.78 599.9540.25 0.83 0.65 997.88 595.5141.25 0.82 0.64 1000.77 590.83 42.25 0.81 0.63 1003.45 585.92 43.25 0.79 0.62 1005.93 580.79 44.25 0.78 0.61 1008.22 575.45 45.25 0.77 0.60 1010.32 569.90 46.25 0.76 0.59 1012.25 564.1647.25 0.75 0.58 1014.00 558.2348.25 0.74 0.57 1015.59 552.1149.25 0.73 0.57 1017.02 545.82 50.25 0.72 0.56 1018.29 539.35 51.25 0.71 0.55 1019.42 532.7252.25 0.70 0.54 1020.40 525.9353.25 0.69 0.54 1021.24 518.98 54.25 0.68 0.53 1021.94 511.88 REGIONAL POND 1-Onsite Portion 0.73 H:\1204\001\DOCS\Design\Storm\CityofBozeman Pond Regiona-Onsite 0.73.xls2 OF 2 PRINTED: 6/10/2021 Gallatin Park Mixed Use 3/15/2021POST DEVELOPMENT Actual 0.7 Weighted C 1.06065197 Weighted C 1.060652 Area (sf)46202 Area (sf)46202 Area (Acres)1.06 Area (Acres)1.06 Area Impervious (0.9)36201 Area Impervious (0.9)34701 Area Gravel (0.8)0 Area Gravel (0.8)0 Area Unimproved (0.2)Area Unimproved (0.2)1500 Area Landscaped (0.1)10001 Area Landscaped (0.1)10001 Weighted C=0.73 Weighted C=0.70 Project Description Friction Method Manning Formula Solve For Discharge Input Data Roughness Coefficient 0.010 Channel Slope 0.00500 ft/ft Normal Depth 0.67 ft Diameter 0.67 ft Results Discharge 1.13 ft³/s Flow Area 0.35 ft² Wetted Perimeter 2.10 ft Hydraulic Radius 0.17 ft Top Width 0.00 ft Critical Depth 0.50 ft Percent Full 100.0 % Critical Slope 0.00601 ft/ft Velocity 3.19 ft/s Velocity Head 0.16 ft Specific Energy 0.83 ft Froude Number 0.00 Maximum Discharge 1.21 ft³/s Discharge Full 1.13 ft³/s Slope Full 0.00500 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 100.00 % Downstream Velocity Infinity ft/s Separator Outlet Pipe 6/10/2021 9:33:58 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page GVF Output Data Upstream Velocity Infinity ft/s Normal Depth 0.67 ft Critical Depth 0.50 ft Channel Slope 0.00500 ft/ft Critical Slope 0.00601 ft/ft Separator Outlet Pipe 6/10/2021 9:33:58 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of2Page Project Description Friction Method Manning Formula Solve For Discharge Input Data Roughness Coefficient 0.013 Channel Slope 0.00500 ft/ft Normal Depth 0.40 ft Left Side Slope 1.00 ft/ft (H:V) Right Side Slope 1.00 ft/ft (H:V) Bottom Width 1.50 ft Results Discharge 2.68 ft³/s Flow Area 0.76 ft² Wetted Perimeter 2.63 ft Hydraulic Radius 0.29 ft Top Width 2.30 ft Critical Depth 0.42 ft Critical Slope 0.00423 ft/ft Velocity 3.53 ft/s Velocity Head 0.19 ft Specific Energy 0.59 ft Froude Number 1.08 Flow Type Supercritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Downstream Velocity Infinity ft/s Upstream Velocity Infinity ft/s Normal Depth 0.40 ft Critical Depth 0.42 ft Channel Slope 0.00500 ft/ft 2' Curb Cut 3/16/2021 5:03:13 PM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page 2' Curb Cut GVF Output Data Critical Slope 0.00423 ft/ft 3/16/2021 5:03:13 PM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of2Page 190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 6 of 7 Initial Stormwater Facility and Initial Abstraction The latest version of DEQ 8 as well as the City of Bozeman requires that the first 0.5 inch of precipitation must be captured and not be allowed to become direct runoff. Since the existing regional storm pond was designed before this requirement, this was not likely addressed. The bioretention pond will retain all of the design storm, thus meeting initial abstraction requirements. The remaining flow from the 0.5 inch runoff from a 24 hour storm will be treated using the hydrodynamic separator to remove 80% of TSS. Maintenance Regular maintenance of storm water facilities is necessary for proper functioning of the drainage system. In general, regular mowing of any grass swales and unclogging of curb cuts and curblines be required to prevent standing water and clogging. More substantial maintenance, such as sediment removal with heavy equipment, may be required in coming decades to restore pond volume and swale function. Sediment removal from the regional storm pond is the responsibility of the HOA. The Hydrodynamic Separator is to be visually inspected every 6 months to check for build-up of sediment in the bottom of the unit. If the sediment depth exceeds 75% of the sump depth or 18 inches deep, the sediment is to be removed using a vac-truck to suck out the sediment and dispose of it at a disposal site. The sediment depth can also be measured from the top of the unit. If the sediment is measured to be 5.7’ or less below the top of the separator unit, then the sediment needs to be removed. Floatables (trash) are to be netted out and disposed of prior to removing sediment with the vac-truck. Any oils or hydrocarbons are to be removed using absorbent pads prior to vac-trucking out the sediment. Reference the Contech CDS Inspection and Maintenance Guide for additional details. All maintenance and repair should be prioritized and scheduled in advance. Structure & pipes should be visually inspected yearly. Typical maintenance items include removing obstructions, cleaning and flushing pipes, mowing grass and weeds, tree maintenance to prevent limbs from falling and blocking swales, and establishing groundcover on bare ground. See the Stormwater Maintenance Manual filed at the Courthouse for additional information. IV. Conclusion Storm water analysis and calculations indicate that the proposed storm water management plan for the Gallatin Park Mixed Use project is adequate to safely convey the 10-year, 25-year, and 100-year storm events while satisfying state and local regulations for peak attenuation and stormwater storage. Furthermore, the proposed first floor elevations for the structures are all above the estimated 100-yr Base flood Elevation as determined by Headwaters Engineering. H:\1204\001\DOCS\Design\Storm\StormwaterDR.doc CDS® Inspection and Maintenance Guide ENGINEERED SOLUTIONS Gallatin Park Mixed Use 325 Gallatin Park Drive Storm Water Facilities Operation & Maintenance Manual Overview The Gallatin Park Subdivision HOA is responsible for maintaining the regional storm pond. The site HOA is responsible for maintenance of all of the onsite Storm Water Facilities, sidewalk chases, curb cuts, storm structures, storm swales and the storm water bioretention area per the schedule below. Maintenance The storm sidewalk chases, curb cuts and curb lines are to have the sediment removed by hand on a yearly basis or an updated maintenance schedule as determined by monitoring the sediment build-up of the inlets quarterly. Any removed sediment shall be removed from the site and disposed of properly as to not discharge into state waters. The Hydrodynamic Separator is to be visually inspected every 6 months to check for build-up of sediment in the bottom of the unit. If the sediment depth exceeds 75% of the sump depth or 18 inches deep, the sediment is to be removed using a vac-truck to suck out the sediment and dispose of it at a disposal site. The sediment depth can also be measured from the top of the unit. If the sediment is measured to be 5.7’ or less below the top of the separator unit, then the sediment needs to be removed. Floatables (trash) are to be netted out and disposed of prior to removing sediment with the vac-truck. Any oils or hydrocarbons are to be removed using absorbent pads prior to vac-trucking out the sediment. Reference the Contech CDS Inspection and Maintenance Guide for additional details. The storm water bioretention pond and grass swales shall be monitored every five years for sediment build-up. When the sediment build-up starts to decrease the capacity of the pond, the sediment shall be removed mechanically and hauled from the site. It the extraction of the sediment removes the vegetation from the bottom of the pond, it should be reseeded or re-sodded and appropriate storm water BMPs are to be installed until the vegetation is stabilized. If the gravel storage within the bioretention pond is compromised, it shall be removed and replaced with clean screened gravels. The owners of the first constructed building will be responsible for maintenance of all of the above items until an HOA is in place or until a second building is constructed. If two buildings are occupied, a HOA must be created which will take over all maintenance. Budget It is estimated that the yearly budget estimates to complete the above items is $1,000. This amount includes some contingency to build up a fund to allow bigger scale maintenance such as gravel replacement within the bioretention pond. 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 would 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. ©2017 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, stormwater, earth stabilization and wastewater treament 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. 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 1.3 3.0 0.9 1.3 1.0 CDS2020 5 1.3 3.5 1.1 1.3 1.0 CDS2025 5 1.3 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.CDS Maintenance Guide - 7/18 (PDF)