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Home My WebLink AboutAppendix D Stormwater Management Design Report 1 of 2 GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT #211237 1 TABLE OF CONTENTS REPORT Introduction ..........................................................................................................................2 Existing Site & Stormwater .................................................................................................2 Cattail Creek Runoff Analysis .............................................................................................3 Proposed Stormwater Design ...............................................................................................3 Stormwater Phasing Plan .....................................................................................................4 Groundwater Considerations ...............................................................................................5 APPENDICES Appendix A: Drainage Area Maps Appendix B: Predevelopment Runoff Calculations Appendix C: Storm Sewer Facilities Calculations Appendix D: StormTech Chamber Details Appendix E: GW Monitoring Data Appendix F: Whole Foods Stormwater Design Report GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT #211237 2 INTRODUCTION This project includes the proposed re-development of a portion of the existing Gallatin Valley Mall property. The re-development includes the demolition and re-development of a portion of the existing Gallatin Valley Mall and construction of four (4) new commercial buildings. A large portion of the existing parking lot will also be re-developed to add landscape and sidewalk islands, and re-align the parking stalls. The property is located within the Bozeman city limits and is currently zoned B-2 commercial. A combination of site grading, curb and gutter, storm chases, and underground detention chambers will be used to manage stormwater runoff on the site. This report is intended to evaluate the drainage design for the future mall re-development. EXISTING SITE & STORMWATER The property generally slopes from south to north, and is currently drained by a series of storm catch basins around the perimeter of the Mall that collect and convey runoff to both an existing detention pond at the northwest corner of the property as well as to upper Cattail Creek via a discharge outfall located at the central portion of the northern property boundary. The satellite businesses (Petco, Whole Foods, Rocky Mountain Bank, and Taco Bell) along the southern perimeter of the Mall property currently drain to a series of retention swales in the landscaped areas around these businesses. These other satellite businesses along Huffine Lane have drainage features that will not be disturbed by the proposed re-development project. These drainage systems are expected to continue to function in their current condition. It should be noted that the Whole Foods satellite business and the parking lot area adjacent to the north was previously designed and approved under C.O.B. project number 20412. Therefore, this portion of the property has been improved to meet C.O.B. design criteria. This portion of the site was designed with infiltration chambers to retain and account for all the runoff produced by the re- development; therefore the future mall re-development will not need to account for runoff from this area. The stormwater design report for the Whole Foods project is attached in Appendix F. However, the remaining portions of the property do not meet current City of Bozeman design standards since it was developed over 30 years ago. The proposed stormwater design for the re- development is intended to bring the entire property into compliance with current standards. GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT #211237 3 CATTAIL CREEK RUNOFF ANALYSIS There is a lack of documentation for the existing mall stormwater design, and the site is currently discharging an unknown amount of runoff into Cattail Creek. Cattail Creek is currently being directed by a 36” culvert running north under the parking lot and mall building. Runoff is conveyed via a 24” outlet pipe from the existing detention pond and an unknown amount of runoff collected via 12” storm pipes from the east side of the property. In order to determine the allowed discharge into Cattail Creek the entire 37-acre lot was analyzed as if it were an undeveloped lot sloping down to the north. A C coefficient of 0.2 was assigned to the contributing area. Assuming these condition a time of concentration was found to be approx. 53 min. and a 10-year storm event would produce 0.69 in/hr of rainfall. The runoff rate from the entire lot into Cattail Creek was found to be 5.18 cfs. This allowable runoff will be utilized by two detention systems that are described later in this report. Calculations for the predevelopment runoff are attached in Appendix B PROPOSED STORMWATER DESIGN The proposed re-development for the rest of the mall is broken up into 4 main construction phases. Each of these phases was evaluated to determine the amount of runoff that will be generated. The proposed stormwater design includes the use of two StormTech detention systems to capture and treat runoff from the 10-year 2-hour storm event. A series of storm mains and inlets will convey runoff to these systems. Each detention system will have an outlet into Cattail Creek, Chamber 1 will be located on the east side of the culvert and Chamber 2 will be on the west side. Both systems were designed in detention, however the half inch requirement governed the required storage volume for the 10-year event. A storm main and inlets will run along the front of the mall to collect sheet flow runoff from the parking lot. The mains will send the runoff to the east and west around the mall and to the detention systems. A drainage area map showing the proposed system is attached in Appendix A. GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT #211237 4 StormTech Detention System #1 located on the east side of the culvert is designed to store the 10-year runoff from Drainage Area 1, 2A, & 3 of the re-development. 20,083 cf of storage is required to meet the half inch requirement which governs this design, and the proposed system has 21,474 cf of storage. StormTech Detention System #2 located on the west side of the culvert is designed to store the 10-year runoff from Drainage Area 2B & 4 of the re-development. 27,503 cf of storage is required to meet the half inch requirement which governs this design, and the proposed system has 28,093 cf of storage. System 1 has an outlet flow of 1.83 cfs and system 2 has an outlet flow of 3.35 cfs, therefore a total of 5.18 cfs will flow to Cattail Creek which is equal to the 5.18 cfs pre-development rate. Sizing and outlet flow calculations are attached in Appendix C STORMWATER PHASING PLAN The redevelopment of the mall is broken down into four phases for construction. StormTech Chamber 1 will be installed with Phase 1 and Chamber 2 will be installed in Phase 4. The storm mains will be installed with each of their respective construction phases. The only exception is Ph 2, where the runoff from Drainage Area 2A will be sent to StormTech Chamber 1, and the runoff from Drainage Area 2B will be temporarily directed to the existing storm main leading westerly and northerly to the existing detention pond until StormTech Chamber 2 is installed in Phase 4 (see figure 1 below for temporary connection). There is no documentation for the storage volume of the existing detention pond, it is currently storing runoff from most of the mall and surrounding parking lot. The mall site is almost entirely hardscaped, and the proposed development is still mostly hardscape so no additional runoff will be generated from the build out of this site. The Whole Foods development is collecting all the runoff generated from its development in StormTech chambers so the pond will already be receiving less runoff than it was previously. Because no additional runoff will we generated the existing pond will have capacity to store the runoff produced from the redevelopment of the mall. GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT #211237 5 Figure 1. GROUNDWATER CONSIDERATIONS Three groundwater (GW) monitoring wells were installed in the mall parking lot in 2021, and were regularly inspected in Spring of 2021 to record fluctuations in the groundwater elevation during the typical peak season for groundwater. The GW monitoring results and map are included in Appendix E for reference. In summary, the monitoring wells are located on the southern portion of the exiting mall building and span the site laterally from east to west with Well #1 being on the eastern portion of the site and Well #3 being on the western portion. Well #2, the center well, had the highest recorded seasonal high groundwater (SHGW) elevation at 4841.25 feet. Well #3 on the western side of the parking lot had the lowest recorded SHGW elevation at 4839.69 feet. Well #1 had a recorded SHGW elevation of 4841.15 feet. The SHGW elevations are used to design the elevations of the proposed stormwater facilities, which primarily consist of StormTech infiltration systems. Empirical GW data is only available for the areas within the vicinity of the three GW monitoring wells. In order to evaluate the expected SHGW elevations throughout the entire site, the slope of the GW table was analyzed to determine the slope of GW. As such, the empirical date from the monitoring wells can be projected throughout the site in order to model the SHGW elevations. GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT #211237 6 To establish the slope of the GW table, GW contours from the 1995 Slagle Map were obtained using the Gallatin County GIS mapper as shown on the exhibit in Appendix E. In summary, groundwater generally flows downgradient to the north is a similar fashion to the exiting surface topography. The southernmost GW contour has an elevation of 4,850’ while the northernmost GW contour has an elevation of 4,800 feet. The distance between the GW contours was measured using the Gallatin County GIS mapper measuring tool and is approximately 3,800 feet. Therefore, the slope of the GW table is 1.32%. It is understood that groundwater flow is dependent of a wide variety of subsurface conditions, but the combination of using empirical site data with this linear model is adequate for the purposes of estimating the SHGW elevations for the proposed stormwater facilities. APPENDIX A Drainage Area Maps APPENDIX B Predevelopment Runoff Calculations TRACT 1, COS. 467A REQUIRED VOLUME 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area DA C Area (ft2 )C * Area Open Land EX 1 0.20 1630271 326054 Total 1630271 326054 A = Area (acres) 37.43 Storm C = Weighted C Factor 0.20 Return (yrs)Cf 2 to 10 1 2. Calculate Tc (Pre-Development)11 to 25 1.1 Tc Overland Flow 26 to 50 1.2 Tc = 1.87 (1.1-CCf)D1/2/S1/3 51 to 100 1.25 S = Slope of Basin (%) 1.320 C = Rational Method Runoff Coefficient 0.2 Cf = Frequency Adjustment Factor 1 D = Length of Basin (ft) 1200 Tc (Pre-Development) (minutes) 53 3. Calculate Rainfall Intensity (Duration = Pre-Development Tc) i = 0.64x-0.65 (10-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.89 (Tc Pre-Development) i = rainfall intensity (in./hr.) 0.69 4. Calculate Runoff Rate (Pre-Development) Q = CiA C = Rational Method Runoff Coefficient 0.2 (open land) i = rainfall intensity (in./hr.) 0.69 (calculated above) A = Area (acres) 37.43 (calculated above) Q = Runoff Rate (Pre-Development) (cfs) 5.18 APPENDIX C Storm Sewer Facilities Calculations DRAINAGE AREA # 1 DRAINAGE AREA #1 RUNOFF VOLUME FROM DA#1 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 0 0 Hardscape 0.95 285605 271325 Total 285605 271325 A = Area (acres)6.56 C = Weighted C Factor 0.95 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.95 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 6.56 Q = RUNOFF (cfs)2.54 V = REQUIRED VOL (ft3)18291 Check the half inch requirement (per DSSP II.A.4) 1. Determine Area of Hardscape within Drainage Area #1 Contributing Area Area (ft 2 ) Hardscape 285605 2. Calculate 1/2" runoff volume over hardscape (aka Runoff Reduction Volume [RRV] as calculated in Montana Post- Construction Storwater BMP Manual - Equation 3-1) RRV = [P*Rv*A]/12 P = Water quality rainfall depth 0.50 inches Rv = Dimensionless runoff coefficient 0.95 0.05 + 0.9*I I = Percent impervious cover (decimal)1.00 decimal A = Entire drainage area 6.56 acres RRV = Runoff Reduction Volume 0.2595 acre-ft RRV = Runoff Reduction Volume 11305 cubic feet Because the runoff volume from the 10-yr, 2-hr storm (for flood control) is greater than the runoff volume produced by the half inch rainfall (for water quality) the proposed detention facility #1 is sized to handle the larger volume (18291 cf). DRAINAGE AREA # 2A DRAINAGE AREA #2A RUNOFF VOLUME FROM DA#2A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 0 0 Hardscape 0.95 99209 94249 Total 99209 94249 A = Area (acres)2.28 C = Weighted C Factor 0.95 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.95 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 2.28 Q = RUNOFF (cfs)0.88 V = REQUIRED VOL (ft3)6354 Check the half inch requirement (per DSSP II.A.4) 1. Determine Area of Hardscape within Drainage Area #2A Contributing Area Area (ft 2 ) Hardscape 99209 2. Calculate 1/2" runoff volume over hardscape (aka Runoff Reduction Volume [RRV] as calculated in Montana Post- Construction Storwater BMP Manual - Equation 3-1) RRV = [P*Rv*A]/12 P = Water quality rainfall depth 0.50 inches Rv = Dimensionless runoff coefficient 0.95 0.05 + 0.9*I I = Percent impervious cover (decimal)1.00 decimal A = Entire drainage area 2.28 acres RRV = Runoff Reduction Volume 0.0902 acre-ft RRV = Runoff Reduction Volume 3927 cubic feet Because the runoff volume from the 10-yr, 2-hr storm (for flood control) is greater than the runoff volume produced by the half inch rainfall (for water quality) the proposed detention facility #1 is sized to handle the larger volume (6354 cf). DRAINAGE AREA # 2B DRAINAGE AREA #2B RUNOFF VOLUME FROM DA#2A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 0 0 Hardscape 0.95 186182 176873 Total 186182 176873 A = Area (acres)4.27 C = Weighted C Factor 0.95 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.95 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 4.27 Q = RUNOFF (cfs)1.66 V = REQUIRED VOL (ft3)11924 Check the half inch requirement (per DSSP II.A.4) 1. Determine Area of Hardscape within Drainage Area #2B Contributing Area Area (ft 2 ) Hardscape 186182 2. Calculate 1/2" runoff volume over hardscape (aka Runoff Reduction Volume [RRV] as calculated in Montana Post- Construction Storwater BMP Manual - Equation 3-1) RRV = [P*Rv*A]/12 P = Water quality rainfall depth 0.50 inches Rv = Dimensionless runoff coefficient 0.95 0.05 + 0.9*I I = Percent impervious cover (decimal)1.00 decimal A = Entire drainage area 4.27 acres RRV = Runoff Reduction Volume 0.1692 acre-ft RRV = Runoff Reduction Volume 7370 cubic feet Because the runoff volume from the 10-yr, 2-hr storm (for flood control) is greater than the runoff volume produced by the half inch rainfall (for water quality) the proposed detention facility #2 is sized to handle the larger volume (11924 cf). DRAINAGE AREA #3 RUNOFF VOLUME FROM DA#3 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 0 0 Hardscape 0.95 122535 116408 Total 122535 116408 A = Area (acres)2.81 C = Weighted C Factor 0.95 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.95 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 2.81 Q = RUNOFF (cfs)1.09 V = REQUIRED VOL (ft3)7848 Check the half inch requirement (per DSSP II.A.4) 1. Determine Area of Hardscape within Drainage Area #3 Contributing Area Area (ft 2 ) Hardscape 122535 2. Calculate 1/2" runoff volume over hardscape (aka Runoff Reduction Volume [RRV] as calculated in Montana Post- Construction Storwater BMP Manual - Equation 3-1) RRV = [P*Rv*A]/12 P = Water quality rainfall depth 0.50 inches Rv = Dimensionless runoff coefficient 0.95 0.05 + 0.9*I I = Percent impervious cover (decimal)1.00 decimal A = Entire drainage area 2.81 acres RRV = Runoff Reduction Volume 0.1113 acre-ft RRV = Runoff Reduction Volume 4850 cubic feet Because the runoff volume from the 10-yr, 2-hr storm (for flood control) is greater than the runoff volume produced by the half inch rainfall (for water quality) the proposed detention facility #1 is sized to handle the larger volume (7848 cf). DRAINAGE AREA #4 RUNOFF VOLUME FROM DA#4 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2)C * Area Landscape 0.2 0 0 Hardscape 0.95 508628 483197 Total 508628 483197 A = Area (acres)11.68 C = Weighted C Factor 0.95 2. Calculate Required Volume Q = CIA V=7200Q C = Weighted C Factor 0.95 I = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 11.68 Q = RUNOFF (cfs)4.52 V = REQUIRED VOL (ft3)32575 Check the half inch requirement (per DSSP II.A.4) 1. Determine Area of Hardscape within Drainage Area #4 Contributing Area Area (ft 2 ) Hardscape 508628 2. Calculate 1/2" runoff volume over hardscape (aka Runoff Reduction Volume [RRV] as calculated in Montana Post- Construction Storwater BMP Manual - Equation 3-1) RRV = [P*Rv*A]/12 P = Water quality rainfall depth 0.50 inches Rv = Dimensionless runoff coefficient 0.95 0.05 + 0.9*I I = Percent impervious cover (decimal)1.00 decimal A = Entire drainage area 11.68 acres RRV = Runoff Reduction Volume 0.4622 acre-ft RRV = Runoff Reduction Volume 20133 cubic feet Because the runoff volume from the 10-yr, 2-hr storm (for flood control) is greater than the runoff volume produced by the half inch rainfall (for water quality) the proposed detention facility #2 is sized to handle the larger volume (32575 cf). DETENTION CHAMBER # 1 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 ) C * Area Landscape 0.2 0 0 Hardscape 0.95 507349 481982 *DA 1, 2A, & 3 Total 507349 481982 A = Area (acres)11.6471 C = Weighted C Factor 0.95 3. Calculate Tc (Pre-Development) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%)1.32% Return (yrs)Cf C = Rational Method Runoff Coefficient 0.2 2 to 10 1 Cf = Frequency Adjustment Factor 1 11 to 25 1.1 D = Length of Basin (ft)1200 26 to 50 1.2 51 to 100 1.25 Tc (Pre-Development) (minutes)53 4. Calculate Rainfall Intensity (Duration = Pre-Development Tc) i = 0.64x-0.65 (10-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs)0.89 (Tc Pre-Development) i = rainfall intensity (in./hr.)0.69 5. Calculate Runoff Rate (Pre-Development) Q = CiA C = Rational Method Runoff Coefficient 0.2 (open land) i = rainfall intensity (in./hr.)0.69 (calculated above) A = Area (acres)11.65 (calculated above) Q = Min. Release Rate Req. (Pre-Development) (cfs)1.61 6. Calculate Required Chamber Volume Total Area (acres) = 11.65 acres Weighted C =0.95 Design Release Rate (cfs) =1.83 cfs Duration(min) Duration(hrs) Intensity (in/hr)Qin (cfs)Runoff Volume Release Volume Required Storage (ft3) 92 1.53 0.48 5.36 29607 10102 19506 93 1.55 0.48 5.33 29719 10211 19508 94 1.57 0.48 5.29 29831 10321 19510 95 1.58 0.47 5.25 29942 10431 19511 96 1.60 0.47 5.22 30052 10541 19511 97 1.62 0.47 5.18 30161 10651 19510 98 1.63 0.47 5.15 30269 10760 19509 99 1.65 0.46 5.11 30377 10870 19507 100 1.67 0.46 5.08 30484 10980 19504 101 1.68 0.46 5.05 30590 11090 19501 OUTLET STRUCTURE SLOT Q=CLH3/2 Q = Discharge (cfs)1.83 (set above) C = Weir Coefficient 3.33 (per COB Design Standards) H = Head (ft)1.5 L = Horizontal Length (ft)0.30 L = Slot Width (inches)3.6 Check the half inch requirement (per DSSP II.A.4) 1. Determine Area of Hardscape within Drainage Basin Contributing Area Area (ft 2 ) Hardscape 507,349 2. Calculate 1/2" runoff volume over hardscape (aka Runoff Reduction Volume [RRV] as calculated in Montana Post- Construction Storwater BMP Manual - Equation 3-1) RRV = [P*Rv*A]/12 P = Water quality rainfall depth 0.50 inches Rv = Dimensionless runoff coefficient 0.95 0.05 + 0.9*I I = Percent impervious cover (decimal)1.00 decimal A = Entire drainage area 11.65 acres RRV = Runoff Reduction Volume 0.461 acre-ft RRV = Runoff Reduction Volume 20,083 cubic feet DETENTION CHAMBER # 2 REQUIRED VOLUME 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2) C * Area Landscape 0.2 0 0 Hardscape 0.95 694810 660070 *DA4 & 2B Total 694810 660070 A = Area (acres)15.9507 C = Weighted C Factor 0.95 3. Calculate Tc (Pre-Development) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%)1.32% Return (yrs)Cf C = Rational Method Runoff Coefficient 0.2 2 to 10 1 Cf = Frequency Adjustment Factor 1 11 to 25 1.1 D = Length of Basin (ft)1200 26 to 50 1.2 51 to 100 1.25 Tc (Pre-Development) (minutes)53 4. Calculate Rainfall Intensity (Duration = Pre-Development Tc) i = 0.64x-0.65 (10-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs)0.89 (Tc Pre-Development) i = rainfall intensity (in./hr.)0.69 5. Calculate Runoff Rate (Pre-Development) Q = CiA C = Rational Method Runoff Coefficient 0.2 (open land) i = rainfall intensity (in./hr.)0.69 (calculated above) A = Area (acres)15.95 (calculated above) Q = Min. Release Rate Req. (Pre-Development) (cfs)2.21 6. Calculate Required Pond Volume Total Area (acres) = 15.95 acres Weighted C =0.95 Design Release Rate (cfs) =3.35 cfs Duration(min) Duration(hrs) Intensity (in/hr)Qin (cfs)Runoff Volume Release Volume Required Storage (ft3) 57 0.95 0.66 10.03 34292 11457 22835 58 0.97 0.65 9.91 34501 11658 22843 59 0.98 0.65 9.80 34708 11859 22849 60 1.00 0.64 9.70 34913 12060 22853 61 1.02 0.63 9.59 35115 12261 22854 62 1.03 0.63 9.49 35316 12462 22854 63 1.05 0.62 9.40 35514 12663 22851 64 1.07 0.61 9.30 35710 12864 22846 65 1.08 0.61 9.21 35905 13065 22840 66 1.10 0.60 9.12 36097 13266 22831 OUTLET STRUCTURE SLOT Q=CLH3/2 Q = Discharge (cfs)3.35 (set above) C = Weir Coefficient 3.33 (per COB Design Standards) H = Head (ft)1.5 L = Horizontal Length (ft)0.55 L = Slot Width (inches)6.6 Check the half inch requirement (per DSSP II.A.4) 1. Determine Area of Hardscape within Drainage Basin Contributing Area Area (ft 2) Hardscape 694,810 2. Calculate 1/2" runoff volume over hardscape (aka Runoff Reduction Volume [RRV] as calculated in Montana Post- Construction Storwater BMP Manual - Equation 3-1) RRV = [P*Rv*A]/12 P = Water quality rainfall depth 0.50 inches Rv = Dimensionless runoff coefficient 0.95 0.05 + 0.9*I I = Percent impervious cover (decimal)1.00 decimal A = Entire drainage area 15.95 acres RRV = Runoff Reduction Volume 0.631 acre-ft RRV = Runoff Reduction Volume 27,503 cubic feet APPENDIX D StormTech Chamber Details Advanced Drainage Systems, Inc.FOR STORMTECHINSTALLATION INSTRUCTIONSVISIT OUR APPSiteAssistMC-3500 STORMTECH CHAMBER SPECIFICATIONS1.CHAMBERS SHALL BE STORMTECH MC-3500.2.CHAMBERS SHALL BE ARCH-SHAPED AND SHALL BE MANUFACTURED FROM VIRGIN, IMPACT-MODIFIED POLYPROPYLENECOPOLYMERS.3.CHAMBERS SHALL MEET THE REQUIREMENTS OF ASTM F2418, "STANDARD SPECIFICATION FOR POLYPROPYLENE (PP) CORRUGATEDWALL STORMWATER COLLECTION CHAMBERS" CHAMBER CLASSIFICATION 45x76 DESIGNATION SS.4.CHAMBER ROWS SHALL PROVIDE CONTINUOUS, UNOBSTRUCTED INTERNAL SPACE WITH NO INTERNAL SUPPORTS THAT WOULDIMPEDE FLOW OR LIMIT ACCESS FOR INSPECTION.5.THE STRUCTURAL DESIGN OF THE CHAMBERS, THE STRUCTURAL BACKFILL, AND THE INSTALLATION REQUIREMENTS SHALL ENSURETHAT THE LOAD FACTORS SPECIFIED IN THE AASHTO LRFD BRIDGE DESIGN SPECIFICATIONS, SECTION 12.12, ARE MET FOR: 1)LONG-DURATION DEAD LOADS AND 2) SHORT-DURATION LIVE LOADS, BASED ON THE AASHTO DESIGN TRUCK WITH CONSIDERATIONFOR IMPACT AND MULTIPLE VEHICLE PRESENCES.6.CHAMBERS SHALL BE DESIGNED, TESTED AND ALLOWABLE LOAD CONFIGURATIONS DETERMINED IN ACCORDANCE WITH ASTM F2787,"STANDARD PRACTICE FOR STRUCTURAL DESIGN OF THERMOPLASTIC CORRUGATED WALL STORMWATER COLLECTION CHAMBERS".LOAD CONFIGURATIONS SHALL INCLUDE: 1) INSTANTANEOUS (<1 MIN) AASHTO DESIGN TRUCK LIVE LOAD ON MINIMUM COVER 2)MAXIMUM PERMANENT (75-YR) COVER LOAD AND 3) ALLOWABLE COVER WITH PARKED (1-WEEK) AASHTO DESIGN TRUCK.7.REQUIREMENTS FOR HANDLING AND INSTALLATION:·TO MAINTAIN THE WIDTH OF CHAMBERS DURING SHIPPING AND HANDLING, CHAMBERS SHALL HAVE INTEGRAL, INTERLOCKINGSTACKING LUGS.·TO ENSURE A SECURE JOINT DURING INSTALLATION AND BACKFILL, THE HEIGHT OF THE CHAMBER JOINT SHALL NOT BE LESSTHAN 3”.·TO ENSURE THE INTEGRITY OF THE ARCH SHAPE DURING INSTALLATION, a) THE ARCH STIFFNESS CONSTANT SHALL BEGREATER THAN OR EQUAL TO 450 LBS/FT/%. THE ASC IS DEFINED IN SECTION 6.2.8 OF ASTM F2418. AND b) TO RESIST CHAMBERDEFORMATION DURING INSTALLATION AT ELEVATED TEMPERATURES (ABOVE 73° F / 23° C), CHAMBERS SHALL BE PRODUCEDFROM REFLECTIVE GOLD OR YELLOW COLORS.8.ONLY CHAMBERS THAT ARE APPROVED BY THE SITE DESIGN ENGINEER WILL BE ALLOWED. UPON REQUEST BY THE SITE DESIGNENGINEER OR OWNER, THE CHAMBER MANUFACTURER SHALL SUBMIT A STRUCTURAL EVALUATION FOR APPROVAL BEFOREDELIVERING CHAMBERS TO THE PROJECT SITE AS FOLLOWS:·THE STRUCTURAL EVALUATION SHALL BE SEALED BY A REGISTERED PROFESSIONAL ENGINEER.·THE STRUCTURAL EVALUATION SHALL DEMONSTRATE THAT THE SAFETY FACTORS ARE GREATER THAN OR EQUAL TO 1.95 FORDEAD LOAD AND 1.75 FOR LIVE LOAD, THE MINIMUM REQUIRED BY ASTM F2787 AND BY SECTIONS 3 AND 12.12 OF THE AASHTOLRFD BRIDGE DESIGN SPECIFICATIONS FOR THERMOPLASTIC PIPE.·THE TEST DERIVED CREEP MODULUS AS SPECIFIED IN ASTM F2418 SHALL BE USED FOR PERMANENT DEAD LOAD DESIGNEXCEPT THAT IT SHALL BE THE 75-YEAR MODULUS USED FOR DESIGN.9.CHAMBERS AND END CAPS SHALL BE PRODUCED AT AN ISO 9001 CERTIFIED MANUFACTURING FACILITY.IMPORTANT - NOTES FOR THE BIDDING AND INSTALLATION OF MC-3500 CHAMBER SYSTEM1.STORMTECH MC-3500 CHAMBERS SHALL NOT BE INSTALLED UNTIL THE MANUFACTURER'S REPRESENTATIVE HAS COMPLETED APRE-CONSTRUCTION MEETING WITH THE INSTALLERS.2.STORMTECH MC-3500 CHAMBERS SHALL BE INSTALLED IN ACCORDANCE WITH THE "STORMTECH MC-3500/MC-4500 CONSTRUCTION GUIDE".3.CHAMBERS ARE NOT TO BE BACKFILLED WITH A DOZER OR AN EXCAVATOR SITUATED OVER THE CHAMBERS.STORMTECH RECOMMENDS 3 BACKFILL METHODS:·STONESHOOTER LOCATED OFF THE CHAMBER BED.·BACKFILL AS ROWS ARE BUILT USING AN EXCAVATOR ON THE FOUNDATION STONE OR SUBGRADE.·BACKFILL FROM OUTSIDE THE EXCAVATION USING A LONG BOOM HOE OR EXCAVATOR.4.THE FOUNDATION STONE SHALL BE LEVELED AND COMPACTED PRIOR TO PLACING CHAMBERS.5.JOINTS BETWEEN CHAMBERS SHALL BE PROPERLY SEATED PRIOR TO PLACING STONE.6.MAINTAIN MINIMUM - 6" (150 mm) SPACING BETWEEN THE CHAMBER ROWS.7.INLET AND OUTLET MANIFOLDS MUST BE INSERTED A MINIMUM OF 12" (300 mm) INTO CHAMBER END CAPS.8.EMBEDMENT STONE SURROUNDING CHAMBERS MUST BE A CLEAN, CRUSHED, ANGULAR STONE MEETING THE AASHTO M43 DESIGNATION OF #3OR #4.9.STONE MUST BE PLACED ON THE TOP CENTER OF THE CHAMBER TO ANCHOR THE CHAMBERS IN PLACE AND PRESERVE ROW SPACING.10.THE CONTRACTOR MUST REPORT ANY DISCREPANCIES WITH CHAMBER FOUNDATION MATERIALS BEARING CAPACITIES TO THE SITE DESIGNENGINEER.11.ADS RECOMMENDS THE USE OF "FLEXSTORM CATCH IT" INSERTS DURING CONSTRUCTION FOR ALL INLETS TO PROTECT THE SUBSURFACESTORMWATER MANAGEMENT SYSTEM FROM CONSTRUCTION SITE RUNOFF.NOTES FOR CONSTRUCTION EQUIPMENT1.STORMTECH MC-3500 CHAMBERS SHALL BE INSTALLED IN ACCORDANCE WITH THE "STORMTECH MC-3500/MC-4500 CONSTRUCTION GUIDE".2.THE USE OF EQUIPMENT OVER MC-3500 CHAMBERS IS LIMITED:·NO EQUIPMENT IS ALLOWED ON BARE CHAMBERS.·NO RUBBER TIRED LOADER, DUMP TRUCK, OR EXCAVATORS ARE ALLOWED UNTIL PROPER FILL DEPTHS ARE REACHED IN ACCORDANCEWITH THE "STORMTECH MC-3500/MC-4500 CONSTRUCTION GUIDE".·WEIGHT LIMITS FOR CONSTRUCTION EQUIPMENT CAN BE FOUND IN THE "STORMTECH MC-3500/MC-4500 CONSTRUCTION GUIDE".3.FULL 36" (900 mm) OF STABILIZED COVER MATERIALS OVER THE CHAMBERS IS REQUIRED FOR DUMP TRUCK TRAVEL OR DUMPING.USE OF A DOZER TO PUSH EMBEDMENT STONE BETWEEN THE ROWS OF CHAMBERS MAY CAUSE DAMAGE TO CHAMBERS AND IS NOT AN ACCEPTABLEBACKFILL METHOD. ANY CHAMBERS DAMAGED BY USING THE "DUMP AND PUSH" METHOD ARE NOT COVERED UNDER THE STORMTECH STANDARDWARRANTY.CONTACT STORMTECH AT 1-888-892-2694 WITH ANY QUESTIONS ON INSTALLATION REQUIREMENTS OR WEIGHT LIMITS FOR CONSTRUCTION EQUIPMENT.©2022 ADS, INC.PROJECT INFORMATIONADS SALES REPPROJECT NO.ENGINEERED PRODUCTMANAGER211237BOZEMAN, MT StormTech888-892-2694 | WWW.STORMTECH.COM®Chamber System4640 TRUEMAN BLVDHILLIARD, OH 430261-800-733-7473DATE: DRAWN: JGPROJECT #: CHECKED: N/ATHIS DRAWING HAS BEEN PREPARED BASED ON INFORMATION PROVIDED TO ADS UNDER THE DIRECTION OF THE SITE DESIGN ENGINEER OR OTHER PROJECT REPRESENTATIVE. THE SITE DESIGN ENGINEER SHALL REVIEW THIS DRAWING PRIOR TO CONSTRUCTION. IT IS THE ULTIMATERESPONSIBILITY OF THE SITE DESIGN ENGINEER TO ENSURE THAT THE PRODUCT(S) DEPICTED AND ALL ASSOCIATED DETAILS MEET ALL APPLICABLE LAWS, REGULATIONS, AND PROJECT REQUIREMENTS.DATEDRWCHKDESCRIPTION211237BOZEMAN, MTSHEETOF26NOTES•MANIFOLD SIZE TO BE DETERMINED BY SITE DESIGN ENGINEER. SEE TECH NOTE #6.32 FOR MANIFOLD SIZING GUIDANCE.•DUE TO THE ADAPTATION OF THIS CHAMBER SYSTEM TO SPECIFIC SITE AND DESIGN CONSTRAINTS, IT MAY BE NECESSARY TO CUT AND COUPLE ADDITIONAL PIPE TO STANDARD MANIFOLDCOMPONENTS IN THE FIELD.•THE SITE DESIGN ENGINEER MUST REVIEW ELEVATIONS AND IF NECESSARY ADJUST GRADING TO ENSURE THE CHAMBER COVER REQUIREMENTS ARE MET.•THIS CHAMBER SYSTEM WAS DESIGNED WITHOUT SITE-SPECIFIC INFORMATION ON SOIL CONDITIONS OR BEARING CAPACITY. THE SITE DESIGN ENGINEER IS RESPONSIBLE FORDETERMININGTHE SUITABILITY OF THE SOIL AND PROVIDING THE BEARING CAPACITY OF THE INSITU SOILS. THE BASE STONE DEPTH MAY BE INCREASED OR DECREASED ONCE THIS INFORMATION ISPROVIDED.•NOT FOR CONSTRUCTION: THIS LAYOUT IS FOR DIMENSIONAL PURPOSES ONLY TO PROVE CONCEPT & THE REQUIRED STORAGE VOLUME CAN BE ACHIEVED ON SITE.*INVERT ABOVE BASE OF CHAMBERISOLATOR ROW PLUS(SEE DETAIL)PLACE MINIMUM 17.50' OF ADSPLUS175 WOVEN GEOTEXTILE OVER BEDDINGSTONE AND UNDERNEATH CHAMBER FEET FOR SCOUR PROTECTION AT ALLCHAMBER INLET ROWSBED LIMITS30'15'0146.40'56.83'139.92'54.83'DCBAEFGCONCEPTUAL ELEVATIONS: CHAMBER 2MAXIMUM ALLOWABLE GRADE (TOP OF PAVEMENT/UNPAVED):12.50MINIMUM ALLOWABLE GRADE (UNPAVED WITH TRAFFIC):6.50MINIMUM ALLOWABLE GRADE (UNPAVED NO TRAFFIC):6.00MINIMUM ALLOWABLE GRADE (TOP OF RIGID CONCRETE PAVEMENT):6.00MINIMUM ALLOWABLE GRADE (BASE OF FLEXIBLE PAVEMENT):6.00TOP OF STONE:5.50TOP OF MC-3500 CHAMBER:4.5024" x 24" BOTTOM MANIFOLD INVERT:0.9224" ISOLATOR ROW PLUS INVERT:0.9218" x 18" BOTTOM MANIFOLD INVERT:0.9018" BOTTOM CONNECTION INVERT:0.90BOTTOM OF MC-3500 CHAMBER:0.75BOTTOM OF STONE:0.00PROPOSED LAYOUT: CHAMBER 2150STORMTECH MC-3500 CHAMBERS16STORMTECH MC-3500 END CAPS12STONE ABOVE (in)9STONE BELOW (in)40STONE VOID28093INSTALLED SYSTEM VOLUME (CF)(PERIMETER STONE INCLUDED)(COVER STONE INCLUDED)(BASE STONE INCLUDED)8207SYSTEM AREA (SF)406.5SYSTEM PERIMETER (ft)MAX FLOWINVERT*DESCRIPTIONITEM ONLAYOUTPART TYPE2.06"24" BOTTOM CORED END CAP, PART#: MC3500IEPP24BC / TYP OF ALL 24" BOTTOMCONNECTIONS AND ISOLATOR PLUS ROWSAPREFABRICATED END CAP1.77"18" BOTTOM CORED END CAP, PART#: MC3500IEPP18BC / TYP OF ALL 18" BOTTOMCONNECTIONSBPREFABRICATED END CAPINSTALL FLAMP ON 24" ACCESS PIPE / PART#: MC350024RAMPCFLAMP2.06"24" x 24" BOTTOM MANIFOLD, ADS N-12DMANIFOLD1.77"18" x 18" BOTTOM MANIFOLD, ADS N-12EMANIFOLD8.0 CFS OUTOCS (DESIGN BY ENGINEER / PROVIDED BY OTHERS)FCONCRETE STRUCTURE35.8 CFS IN(DESIGN BY ENGINEER / PROVIDED BY OTHERS)GCONCRETE STRUCTUREW/WEIR StormTech888-892-2694 | WWW.STORMTECH.COM®Chamber System4640 TRUEMAN BLVDHILLIARD, OH 430261-800-733-7473DATE: DRAWN: JGPROJECT #: CHECKED: N/ATHIS DRAWING HAS BEEN PREPARED BASED ON INFORMATION PROVIDED TO ADS UNDER THE DIRECTION OF THE SITE DESIGN ENGINEER OR OTHER PROJECT REPRESENTATIVE. THE SITE DESIGN ENGINEER SHALL REVIEW THIS DRAWING PRIOR TO CONSTRUCTION. IT IS THE ULTIMATERESPONSIBILITY OF THE SITE DESIGN ENGINEER TO ENSURE THAT THE PRODUCT(S) DEPICTED AND ALL ASSOCIATED DETAILS MEET ALL APPLICABLE LAWS, REGULATIONS, AND PROJECT REQUIREMENTS.DATEDRWCHKDESCRIPTION211237BOZEMAN, MTSHEETOF36NOTES•MANIFOLD SIZE TO BE DETERMINED BY SITE DESIGN ENGINEER. SEE TECH NOTE #6.32 FOR MANIFOLD SIZING GUIDANCE.•DUE TO THE ADAPTATION OF THIS CHAMBER SYSTEM TO SPECIFIC SITE AND DESIGN CONSTRAINTS, IT MAY BE NECESSARY TO CUT AND COUPLE ADDITIONAL PIPE TO STANDARD MANIFOLDCOMPONENTS IN THE FIELD.•THE SITE DESIGN ENGINEER MUST REVIEW ELEVATIONS AND IF NECESSARY ADJUST GRADING TO ENSURE THE CHAMBER COVER REQUIREMENTS ARE MET.•THIS CHAMBER SYSTEM WAS DESIGNED WITHOUT SITE-SPECIFIC INFORMATION ON SOIL CONDITIONS OR BEARING CAPACITY. THE SITE DESIGN ENGINEER IS RESPONSIBLE FORDETERMININGTHE SUITABILITY OF THE SOIL AND PROVIDING THE BEARING CAPACITY OF THE INSITU SOILS. THE BASE STONE DEPTH MAY BE INCREASED OR DECREASED ONCE THIS INFORMATION ISPROVIDED.•NOT FOR CONSTRUCTION: THIS LAYOUT IS FOR DIMENSIONAL PURPOSES ONLY TO PROVE CONCEPT & THE REQUIRED STORAGE VOLUME CAN BE ACHIEVED ON SITE.*INVERT ABOVE BASE OF CHAMBERISOLATOR ROW PLUS(SEE DETAIL)PLACE MINIMUM 17.50' OF ADSPLUS175 WOVEN GEOTEXTILE OVER BEDDINGSTONE AND UNDERNEATH CHAMBER FEET FOR SCOUR PROTECTION AT ALLCHAMBER INLET ROWSBED LIMITS30'15'0150.18'43.00'139.92'41.00'DCBAEGFCONCEPTUAL ELEVATIONS: CHAMBER 1MAXIMUM ALLOWABLE GRADE (TOP OF PAVEMENT/UNPAVED):12.50MINIMUM ALLOWABLE GRADE (UNPAVED WITH TRAFFIC):6.50MINIMUM ALLOWABLE GRADE (UNPAVED NO TRAFFIC):6.00MINIMUM ALLOWABLE GRADE (TOP OF RIGID CONCRETE PAVEMENT):6.00MINIMUM ALLOWABLE GRADE (BASE OF FLEXIBLE PAVEMENT):6.00TOP OF STONE:5.50TOP OF MC-3500 CHAMBER:4.5024" ISOLATOR ROW PLUS INVERT:0.9218" x 18" BOTTOM MANIFOLD INVERT:0.9018" x 18" BOTTOM MANIFOLD INVERT:0.9018" BOTTOM CONNECTION INVERT:0.90BOTTOM OF MC-3500 CHAMBER:0.75BOTTOM OF STONE:0.00PROPOSED LAYOUT: CHAMBER 1114STORMTECH MC-3500 CHAMBERS12STORMTECH MC-3500 END CAPS12STONE ABOVE (in)9STONE BELOW (in)40STONE VOID21474INSTALLED SYSTEM VOLUME (CF)(PERIMETER STONE INCLUDED)(COVER STONE INCLUDED)(BASE STONE INCLUDED)6294SYSTEM AREA (SF)386.4SYSTEM PERIMETER (ft)MAX FLOWINVERT*DESCRIPTIONITEM ONLAYOUTPART TYPE2.06"24" BOTTOM CORED END CAP, PART#: MC3500IEPP24BC / TYP OF ALL 24" BOTTOMCONNECTIONS AND ISOLATOR PLUS ROWSAPREFABRICATED END CAP1.77"18" BOTTOM CORED END CAP, PART#: MC3500IEPP18BC / TYP OF ALL 18" BOTTOMCONNECTIONSBPREFABRICATED END CAPINSTALL FLAMP ON 24" ACCESS PIPE / PART#: MC350024RAMPCFLAMP1.77"18" x 18" BOTTOM MANIFOLD, ADS N-12DMANIFOLD1.77"18" x 18" BOTTOM MANIFOLD, ADS N-12EMANIFOLD8.0 CFS OUTOCS (DESIGN BY ENGINEER / PROVIDED BY OTHERS)FCONCRETE STRUCTURE20.9 CFS IN(DESIGN BY ENGINEER / PROVIDED BY OTHERS)GCONCRETE STRUCTUREW/WEIR StormTech888-892-2694 | WWW.STORMTECH.COM®Chamber SystemACCEPTABLE FILL MATERIALS: STORMTECH MC-3500 CHAMBER SYSTEMSPLEASE NOTE:1.THE LISTED AASHTO DESIGNATIONS ARE FOR GRADATIONS ONLY. THE STONE MUST ALSO BE CLEAN, CRUSHED, ANGULAR. FOR EXAMPLE, A SPECIFICATION FOR #4 STONE WOULD STATE: "CLEAN, CRUSHED, ANGULAR NO. 4 (AASHTO M43) STONE".2.STORMTECH COMPACTION REQUIREMENTS ARE MET FOR 'A' LOCATION MATERIALS WHEN PLACED AND COMPACTED IN 9" (230 mm) (MAX) LIFTS USING TWO FULL COVERAGES WITH A VIBRATORY COMPACTOR.3.WHERE INFILTRATION SURFACES MAY BE COMPROMISED BY COMPACTION, FOR STANDARD DESIGN LOAD CONDITIONS, A FLAT SURFACE MAY BE ACHIEVED BY RAKING OR DRAGGING WITHOUT COMPACTION EQUIPMENT. FOR SPECIAL LOAD DESIGNS, CONTACT STORMTECH FORCOMPACTION REQUIREMENTS.4.ONCE LAYER 'C' IS PLACED, ANY SOIL/MATERIAL CAN BE PLACED IN LAYER 'D' UP TO THE FINISHED GRADE. MOST PAVEMENT SUBBASE SOILS CAN BE USED TO REPLACE THE MATERIAL REQUIREMENTS OF LAYER 'C' OR 'D' AT THE SITE DESIGN ENGINEER'S DISCRETION.NOTES:1.CHAMBERS SHALL MEET THE REQUIREMENTS OF ASTM F2418, "STANDARD SPECIFICATION FOR POLYPROPYLENE (PP) CORRUGATED WALL STORMWATER COLLECTION CHAMBERS" CHAMBER CLASSIFICATION 45x76DESIGNATION SS.2.MC-3500 CHAMBERS SHALL BE DESIGNED IN ACCORDANCE WITH ASTM F2787 "STANDARD PRACTICE FOR STRUCTURAL DESIGN OF THERMOPLASTIC CORRUGATED WALL STORMWATER COLLECTION CHAMBERS".3.THE SITE DESIGN ENGINEER IS RESPONSIBLE FOR ASSESSING THE BEARING RESISTANCE (ALLOWABLE BEARING CAPACITY) OF THE SUBGRADE SOILS AND THE DEPTH OF FOUNDATION STONE WITH CONSIDERATIONFOR THE RANGE OF EXPECTED SOIL MOISTURE CONDITIONS.4.PERIMETER STONE MUST BE EXTENDED HORIZONTALLY TO THE EXCAVATION WALL FOR BOTH VERTICAL AND SLOPED EXCAVATION WALLS.5.REQUIREMENTS FOR HANDLING AND INSTALLATION:·TO MAINTAIN THE WIDTH OF CHAMBERS DURING SHIPPING AND HANDLING, CHAMBERS SHALL HAVE INTEGRAL, INTERLOCKING STACKING LUGS.·TO ENSURE A SECURE JOINT DURING INSTALLATION AND BACKFILL, THE HEIGHT OF THE CHAMBER JOINT SHALL NOT BE LESS THAN 3”.·TO ENSURE THE INTEGRITY OF THE ARCH SHAPE DURING INSTALLATION, a) THE ARCH STIFFNESS CONSTANT SHALL BE GREATER THAN OR EQUAL TO 450 LBS/FT/%. THE ASC IS DEFINED IN SECTION 6.2.8 OFASTM F2418. AND b) TO RESIST CHAMBER DEFORMATION DURING INSTALLATION AT ELEVATED TEMPERATURES (ABOVE 73° F / 23° C), CHAMBERS SHALL BE PRODUCED FROM REFLECTIVE GOLD OR YELLOWCOLORS.MATERIAL LOCATIONDESCRIPTIONAASHTO MATERIALCLASSIFICATIONSCOMPACTION / DENSITY REQUIREMENTDFINAL FILL: FILL MATERIAL FOR LAYER 'D' STARTS FROM THE TOP OF THE 'C'LAYER TO THE BOTTOM OF FLEXIBLE PAVEMENT OR UNPAVED FINISHEDGRADE ABOVE. NOTE THAT PAVEMENT SUBBASE MAY BE PART OF THE 'D'LAYERANY SOIL/ROCK MATERIALS, NATIVE SOILS, OR PER ENGINEER'S PLANS.CHECK PLANS FOR PAVEMENT SUBGRADE REQUIREMENTS.N/APREPARE PER SITE DESIGN ENGINEER'S PLANS. PAVEDINSTALLATIONS MAY HAVE STRINGENT MATERIAL ANDPREPARATION REQUIREMENTS.CINITIAL FILL: FILL MATERIAL FOR LAYER 'C' STARTS FROM THE TOP OF THEEMBEDMENT STONE ('B' LAYER) TO 24" (600 mm) ABOVE THE TOP OF THECHAMBER. NOTE THAT PAVEMENT SUBBASE MAY BE A PART OF THE 'C'LAYER.GRANULAR WELL-GRADED SOIL/AGGREGATE MIXTURES, <35% FINES ORPROCESSED AGGREGATE. MOST PAVEMENT SUBBASE MATERIALS CAN BE USED IN LIEU OF THISLAYER.AASHTO M145¹A-1, A-2-4, A-3ORAASHTO M43¹3, 357, 4, 467, 5, 56, 57, 6, 67, 68, 7, 78, 8, 89, 9, 10BEGIN COMPACTIONS AFTER 24" (600 mm) OF MATERIAL OVERTHE CHAMBERS IS REACHED. COMPACT ADDITIONAL LAYERS IN12" (300 mm) MAX LIFTS TO A MIN. 95% PROCTOR DENSITY FORWELL GRADED MATERIAL AND 95% RELATIVE DENSITY FORPROCESSED AGGREGATE MATERIALS.BEMBEDMENT STONE: FILL SURROUNDING THE CHAMBERS FROM THEFOUNDATION STONE ('A' LAYER) TO THE 'C' LAYER ABOVE.CLEAN, CRUSHED, ANGULAR STONEAASHTO M43¹3, 4AFOUNDATION STONE: FILL BELOW CHAMBERS FROM THE SUBGRADE UP TOTHE FOOT (BOTTOM) OF THE CHAMBER.CLEAN, CRUSHED, ANGULAR STONEAASHTO M43¹3, 4PLATE COMPACT OR ROLL TO ACHIEVE A FLAT SURFACE.2,345"(1140 mm)18"(450 mm) MIN*8'(2.4 m)MAX12" (300 mm) MIN77" (1950 mm)12" (300 mm) MIN6"(150 mm) MINDEPTH OF STONE TO BE DETERMINEDBY SITE DESIGN ENGINEER 9" (230 mm) MINDCBA*TO BOTTOM OF FLEXIBLE PAVEMENT. FOR UNPAVEDINSTALLATIONS WHERE RUTTING FROM VEHICLES MAY OCCUR,INCREASE COVER TO 24" (600 mm).6" (150 mm) MINPERIMETER STONE(SEE NOTE 4)EXCAVATION WALL(CAN BE SLOPED OR VERTICAL)MC-3500END CAPSUBGRADE SOILS(SEE NOTE 3)PAVEMENT LAYER (DESIGNEDBY SITE DESIGN ENGINEER)NO COMPACTION REQUIRED.ADS GEOSYNTHETICS 601T NON-WOVEN GEOTEXTILE ALLAROUND CLEAN, CRUSHED, ANGULAR STONE IN A & B LAYERS4640 TRUEMAN BLVDHILLIARD, OH 430261-800-733-7473DATE: DRAWN: JGPROJECT #: CHECKED: N/ATHIS DRAWING HAS BEEN PREPARED BASED ON INFORMATION PROVIDED TO ADS UNDER THE DIRECTION OF THE SITE DESIGN ENGINEER OR OTHER PROJECT REPRESENTATIVE. THE SITE DESIGN ENGINEER SHALL REVIEW THIS DRAWING PRIOR TO CONSTRUCTION. IT IS THE ULTIMATERESPONSIBILITY OF THE SITE DESIGN ENGINEER TO ENSURE THAT THE PRODUCT(S) DEPICTED AND ALL ASSOCIATED DETAILS MEET ALL APPLICABLE LAWS, REGULATIONS, AND PROJECT REQUIREMENTS.DATEDRWCHKDESCRIPTION211237BOZEMAN, MTSHEETOF46 StormTech888-892-2694 | WWW.STORMTECH.COM®Chamber SystemINSPECTION & MAINTENANCESTEP 1)INSPECT ISOLATOR ROW PLUS FOR SEDIMENTA.INSPECTION PORTS (IF PRESENT)A.1.REMOVE/OPEN LID ON NYLOPLAST INLINE DRAINA.2.REMOVE AND CLEAN FLEXSTORM FILTER IF INSTALLEDA.3.USING A FLASHLIGHT AND STADIA ROD, MEASURE DEPTH OF SEDIMENT AND RECORD ON MAINTENANCE LOGA.4.LOWER A CAMERA INTO ISOLATOR ROW PLUS FOR VISUAL INSPECTION OF SEDIMENT LEVELS (OPTIONAL)A.5.IF SEDIMENT IS AT, OR ABOVE, 3" (80 mm) PROCEED TO STEP 2. IF NOT, PROCEED TO STEP 3.B.ALL ISOLATOR PLUS ROWSB.1.REMOVE COVER FROM STRUCTURE AT UPSTREAM END OF ISOLATOR ROW PLUSB.2.USING A FLASHLIGHT, INSPECT DOWN THE ISOLATOR ROW PLUS THROUGH OUTLET PIPEi)MIRRORS ON POLES OR CAMERAS MAY BE USED TO AVOID A CONFINED SPACE ENTRYii)FOLLOW OSHA REGULATIONS FOR CONFINED SPACE ENTRY IF ENTERING MANHOLEB.3.IF SEDIMENT IS AT, OR ABOVE, 3" (80 mm) PROCEED TO STEP 2. IF NOT, PROCEED TO STEP 3.STEP 2)CLEAN OUT ISOLATOR ROW PLUS USING THE JETVAC PROCESSA.A FIXED CULVERT CLEANING NOZZLE WITH REAR FACING SPREAD OF 45" (1.1 m) OR MORE IS PREFERREDB.APPLY MULTIPLE PASSES OF JETVAC UNTIL BACKFLUSH WATER IS CLEANC.VACUUM STRUCTURE SUMP AS REQUIREDSTEP 3)REPLACE ALL COVERS, GRATES, FILTERS, AND LIDS; RECORD OBSERVATIONS AND ACTIONS.STEP 4)INSPECT AND CLEAN BASINS AND MANHOLES UPSTREAM OF THE STORMTECH SYSTEM.NOTES1.INSPECT EVERY 6 MONTHS DURING THE FIRST YEAR OF OPERATION. ADJUST THE INSPECTION INTERVAL BASED ON PREVIOUSOBSERVATIONS OF SEDIMENT ACCUMULATION AND HIGH WATER ELEVATIONS.2.CONDUCT JETTING AND VACTORING ANNUALLY OR WHEN INSPECTION SHOWS THAT MAINTENANCE IS NECESSARY.CATCH BASINORMANHOLEMC-3500 ISOLATOR ROW PLUS DETAILNTS24" (600 mm) HDPE ACCESS PIPE REQUIRED USEFACTORY PRE-CORED END CAPPART #: MC3500IEPP24BC OR MC3500IEPP24BWSTORMTECH HIGHLY RECOMMENDSFLEXSTORM INSERTS IN ANY UPSTREAMSTRUCTURES WITH OPEN GRATESCOVER PIPE CONNECTION TO END CAP WITH ADSGEOSYNTHETICS 601T NON-WOVEN GEOTEXTILEMC-3500 CHAMBEROPTIONAL INSPECTION PORTMC-3500 END CAPONE LAYER OF ADSPLUS175 WOVEN GEOTEXTILE BETWEENFOUNDATION STONE AND CHAMBERS8.25' (2.51 m) MIN WIDE CONTINUOUS FABRIC WITHOUT SEAMSSUMP DEPTH TBD BYSITE DESIGN ENGINEER(24" [600 mm] MIN RECOMMENDED)INSTALL FLAMP ON 24" (600 mm) ACCESS PIPEPART #: MC350024RAMP4640 TRUEMAN BLVDHILLIARD, OH 430261-800-733-7473DATE: DRAWN: JGPROJECT #: CHECKED: N/ATHIS DRAWING HAS BEEN PREPARED BASED ON INFORMATION PROVIDED TO ADS UNDER THE DIRECTION OF THE SITE DESIGN ENGINEER OR OTHER PROJECT REPRESENTATIVE. THE SITE DESIGN ENGINEER SHALL REVIEW THIS DRAWING PRIOR TO CONSTRUCTION. IT IS THE ULTIMATERESPONSIBILITY OF THE SITE DESIGN ENGINEER TO ENSURE THAT THE PRODUCT(S) DEPICTED AND ALL ASSOCIATED DETAILS MEET ALL APPLICABLE LAWS, REGULATIONS, AND PROJECT REQUIREMENTS.DATEDRWCHKDESCRIPTION211237BOZEMAN, MTSHEETOF56 StormTech888-892-2694 | WWW.STORMTECH.COM®Chamber SystemMC-SERIES END CAP INSERTION DETAILNTSNOTE: MANIFOLD STUB MUST BE LAID HORIZONTALFOR A PROPER FIT IN END CAP OPENING.MANIFOLD HEADERMANIFOLD STUBSTORMTECH END CAPMANIFOLD HEADERMANIFOLD STUB12" (300 mm)MIN SEPARATION12" (300 mm) MIN INSERTION12" (300 mm)MIN SEPARATION12" (300 mm)MIN INSERTIONPART #STUBBCMC3500IEPP06T6" (150 mm)33.21" (844 mm)---MC3500IEPP06B---0.66" (17 mm)MC3500IEPP08T8" (200 mm)31.16" (791 mm)---MC3500IEPP08B---0.81" (21 mm)MC3500IEPP10T10" (250 mm)29.04" (738 mm)---MC3500IEPP10B---0.93" (24 mm)MC3500IEPP12T12" (300 mm)26.36" (670 mm)---MC3500IEPP12B---1.35" (34 mm)MC3500IEPP15T15" (375 mm)23.39" (594 mm)---MC3500IEPP15B---1.50" (38 mm)MC3500IEPP18TC18" (450 mm)20.03" (509 mm)---MC3500IEPP18TWMC3500IEPP18BC---1.77" (45 mm)MC3500IEPP18BWMC3500IEPP24TC24" (600 mm)14.48" (368 mm)---MC3500IEPP24TWMC3500IEPP24BC---2.06" (52 mm)MC3500IEPP24BWMC3500IEPP30BC30" (750 mm)---2.75" (70 mm)NOMINAL CHAMBER SPECIFICATIONSSIZE (W X H X INSTALLED LENGTH)77.0" X 45.0" X 86.0" (1956 mm X 1143 mm X 2184 mm)CHAMBER STORAGE109.9 CUBIC FEET (3.11 m³)MINIMUM INSTALLED STORAGE*175.0 CUBIC FEET (4.96 m³)WEIGHT134 lbs.(60.8 kg)NOMINAL END CAP SPECIFICATIONSSIZE (W X H X INSTALLED LENGTH)75.0" X 45.0" X 22.2" (1905 mm X 1143 mm X 564 mm)END CAP STORAGE14.9 CUBIC FEET (0.42 m³)MINIMUM INSTALLED STORAGE*45.1 CUBIC FEET (1.28 m³)WEIGHT49 lbs.(22.2 kg)*ASSUMES 12" (305 mm) STONE ABOVE, 9" (229 mm) STONE FOUNDATION, 6" SPACING BETWEENCHAMBERS, 6" (152 mm) STONE PERIMETER IN FRONT OF END CAPS AND 40% STONE POROSITYMC-3500 TECHNICAL SPECIFICATIONNTS90.0" (2286 mm)ACTUAL LENGTH86.0" (2184 mm)INSTALLEDBUILD ROW IN THIS DIRECTIONNOTE: ALL DIMENSIONS ARE NOMINALLOWER JOINTCORRUGATIONWEBCRESTCRESTSTIFFENING RIBVALLEYSTIFFENING RIBBC75.0"(1905 mm)45.0"(1143 mm)25.7"(653 mm)FOOT77.0"(1956 mm)45.0"(1143 mm)STUBS AT BOTTOM OF END CAP FOR PART NUMBERS ENDING WITH "B"STUBS AT TOP OF END CAP FOR PART NUMBERS ENDING WITH "T"END CAPS WITH A WELDED CROWN PLATE END WITH "C"END CAPS WITH A PREFABRICATED WELDED STUB END WITH "W"UPPER JOINT CORRUGATION22.2"(564 mm)INSTALLEDCUSTOM PRECORED INVERTS AREAVAILABLE UPON REQUEST.INVENTORIED MANIFOLDS INCLUDE12-24" (300-600 mm) SIZE ON SIZEAND 15-48" (375-1200 mm)ECCENTRIC MANIFOLDS. CUSTOMINVERT LOCATIONS ON THE MC-3500END CAP CUT IN THE FIELD ARE NOTRECOMMENDED FOR PIPE SIZESGREATER THAN 10" (250 mm). THEINVERT LOCATION IN COLUMN 'B'ARE THE HIGHEST POSSIBLE FORTHE PIPE SIZE.PART #STUBBCMC3500IEPP06T6" (150 mm)33.21" (844 mm)---MC3500IEPP06B---0.66" (17 mm)MC3500IEPP08T8" (200 mm)31.16" (791 mm)---MC3500IEPP08B---0.81" (21 mm)MC3500IEPP10T10" (250 mm)29.04" (738 mm)---MC3500IEPP10B---0.93" (24 mm)MC3500IEPP12T12" (300 mm)26.36" (670 mm)---MC3500IEPP12B---1.35" (34 mm)MC3500IEPP15T15" (375 mm)23.39" (594 mm)---MC3500IEPP15B---1.50" (38 mm)MC3500IEPP18TC18" (450 mm)20.03" (509 mm)---MC3500IEPP18TWMC3500IEPP18BC---1.77" (45 mm)MC3500IEPP18BWMC3500IEPP24TC24" (600 mm)14.48" (368 mm)---MC3500IEPP24TWMC3500IEPP24BC---2.06" (52 mm)MC3500IEPP24BWMC3500IEPP30BC30" (750 mm)---2.75" (70 mm)NOMINAL CHAMBER SPECIFICATIONSSIZE (W X H X INSTALLED LENGTH)77.0" X 45.0" X 86.0" (1956 mm X 1143 mm X 2184 mm)CHAMBER STORAGE109.9 CUBIC FEET (3.11 m³)MINIMUM INSTALLED STORAGE*175.0 CUBIC FEET (4.96 m³)WEIGHT134 lbs.(60.8 kg)NOMINAL END CAP SPECIFICATIONSSIZE (W X H X INSTALLED LENGTH)75.0" X 45.0" X 22.2" (1905 mm X 1143 mm X 564 mm)END CAP STORAGE14.9 CUBIC FEET (0.42 m³)MINIMUM INSTALLED STORAGE*45.1 CUBIC FEET (1.28 m³)WEIGHT49 lbs.(22.2 kg)*ASSUMES 12" (305 mm) STONE ABOVE, 9" (229 mm) STONE FOUNDATION, 6" SPACING BETWEENCHAMBERS, 6" (152 mm) STONE PERIMETER IN FRONT OF END CAPS AND 40% STONE POROSITYMC-3500 TECHNICAL SPECIFICATIONNTS90.0" (2286 mm)ACTUAL LENGTH86.0" (2184 mm)INSTALLEDBUILD ROW IN THIS DIRECTIONNOTE: ALL DIMENSIONS ARE NOMINALLOWER JOINTCORRUGATIONWEBCRESTCRESTSTIFFENING RIBVALLEYSTIFFENING RIBBC75.0"(1905 mm)45.0"(1143 mm)25.7"(653 mm)FOOT77.0"(1956 mm)45.0"(1143 mm)STUBS AT BOTTOM OF END CAP FOR PART NUMBERS ENDING WITH "B"STUBS AT TOP OF END CAP FOR PART NUMBERS ENDING WITH "T"END CAPS WITH A WELDED CROWN PLATE END WITH "C"END CAPS WITH A PREFABRICATED WELDED STUB END WITH "W"UPPER JOINT CORRUGATION22.2"(564 mm)INSTALLEDCUSTOM PRECORED INVERTS AREAVAILABLE UPON REQUEST.INVENTORIED MANIFOLDS INCLUDE12-24" (300-600 mm) SIZE ON SIZEAND 15-48" (375-1200 mm)ECCENTRIC MANIFOLDS. CUSTOMINVERT LOCATIONS ON THE MC-3500END CAP CUT IN THE FIELD ARE NOTRECOMMENDED FOR PIPE SIZESGREATER THAN 10" (250 mm). THEINVERT LOCATION IN COLUMN 'B'ARE THE HIGHEST POSSIBLE FORTHE PIPE SIZE.4640 TRUEMAN BLVDHILLIARD, OH 430261-800-733-7473DATE: DRAWN: JGPROJECT #: CHECKED: N/ATHIS DRAWING HAS BEEN PREPARED BASED ON INFORMATION PROVIDED TO ADS UNDER THE DIRECTION OF THE SITE DESIGN ENGINEER OR OTHER PROJECT REPRESENTATIVE. THE SITE DESIGN ENGINEER SHALL REVIEW THIS DRAWING PRIOR TO CONSTRUCTION. IT IS THE ULTIMATERESPONSIBILITY OF THE SITE DESIGN ENGINEER TO ENSURE THAT THE PRODUCT(S) DEPICTED AND ALL ASSOCIATED DETAILS MEET ALL APPLICABLE LAWS, REGULATIONS, AND PROJECT REQUIREMENTS.DATEDRWCHKDESCRIPTION211237BOZEMAN, MTSHEETOF66 APPENDIX E GW Monitoring Data :(// :(// :(// *5281':$7(5021,725,1*:(//),*85( 3URMHFW(QJLQHHU3URMHFW*DOODWLQ0DOO)XGUXFNHUV*DOODWLQ&RXQW\07:HOO,QIRUPDWLRQEJV EHORZJURXQGVXUIDFHDJV DERYHJURXQGVXUIDFH0: 0: 0: *URXQGZDWHU,QIRUPDWLRQ0: 0: 0:'U\ 'U\'U\ 'U\ 'U\ 'U\'U\ 'U\0RQLWRU:HOO'DWD'HSWKWR*URXQG:DWHUElevation3URMHFW1XPEHU *DOODWLQ0DOO*URXQGZDWHU0RQLWRULQJ3URMHFW/RFDWLRQ:HOO,':HOO'HSWK)HHW7RSRI:HOO(OHYDWLRQ*URXQG(OHYDWLRQ'DWH APPENDIX F Whole Foods Stormwater Design Report GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT April 28, 2021 #200526 1 TABLE OF CONTENTS REPORT Introduction ..........................................................................................................................2 Existing Site & Stormwater .................................................................................................2 Groundwater Considerations ...............................................................................................3 Proposed Stormwater Design ...............................................................................................4 Retention Pond Design ........................................................................................................5 Infiltration Chamber Design ................................................................................................6 APPENDICES Appendix A: Drainage Area Map Appendix B: Storm Sewer Facilities Calculations Appendix C: Falling Head Infiltration Test Appendix D: StormTech Chamber Details Appendix E: GW Monitoring Data GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT April 28, 2021 #200526 2 INTRODUCTION This project includes the proposed re-development of a portion of the existing Gallatin Valley Mall property. The re-development includes the demolition of the existing “Fuddruckers” restaurant, construction of a commercial building for use as a grocery store, and construction of an additional commercial building containing several commercial/restaurant spaces. A large portion of the existing parking lot will also be re-developed to add landscape and sidewalk islands, and re-align the parking stalls. The property is located within the Bozeman city limits and is currently zoned B-2 commercial. A combination of site grading, curb and gutter, storm chases, retention ponds, and underground infiltration chambers will be used to manage stormwater runoff on the site. EXISTING SITE & STORMWATER The property generally slopes from south to north, and is currently drained by a series of storm catch basins around the perimeter of the Mall that collect and convey runoff to an existing detention pond at the northwest corner of the property. The satellite businesses (Petco, Fuddruckers, Rocky Mountain Bank, and Taco Bell) along the southern perimeter of the Mall property currently drain to a series of retention swales in the landscaped areas around these businesses. With the exception of Rocky Mountain Bank, the other satellite businesses along Huffine Lane have drainage features that will not be disturbed by the proposed re-development project. These drainage systems are expected to continue to function in their current condition. The existing catch basins in the Mall parking lot were surveyed in September 2020, and both the catch basins and the existing detention pond contained standing groundwater. The detention pond and manholes were drained and cleaned to increase their functionality, but with the groundwater inundation this detention system likely does not meet current City of Bozeman design standards. Preliminary plans are underway to re-develop the entire Mall property in the next few years. Therefore, the proposed stormwater design for this re-development project only focuses on GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT April 28, 2021 #200526 3 capturing and treating stormwater within the re-development area, and stormwater that will drain to the re-development area from the surrounding mall property. This was discussed with the City Engineering Department, and it was determined that the area being re-developed needs to meet current standards, but the remainder of the property could continue to function in its current condition. As the entire property is re-developed in the next few years the entire property will be brought into compliance with current standards. However, since the current plans for re- development are still preliminary, bringing the entire site into compliance at this time is not feasible. Therefore, the majority of stormwater runoff on the remainder of the Mall property outside of the re-development area will continue to drain to the existing catch basins in the parking lot, and be conveyed to the existing detention pond. The existing catch basins and storm piping that pass through the re-development area will be left intact to continue to convey stormwater to the detention pond from the eastern portion of the parking lot. However, their grates will be replaced with solid covers so that they do not collect runoff from the re-development area. Additionally, the re-development area has been graded so that the existing catch basins within this area are no longer at low points that collect stormwater. GROUNDWATER CONSIDERATIONS Three groundwater monitoring wells were installed in the mall parking lot, and have been regularly inspected this spring to record fluctuations in the groundwater elevation during the typical peak season for groundwater. The GW monitoring results and map are included in Appendix E for reference. Of the 3 installed wells, 2 of wells, Well #2 and #3, are located in the direct vicinity of the 5 proposed Stormtech infiltration chambers. Well #2, the center well, had the highest recorded GW elevation at 4841.25’. Well #3 on the western side of the parking lot had the lowest recorded GW elevation at 4839.69. Since the western edge of the project is directly adjacent to the Bozeman Pond in the adjacent park, it is assumed that the GW elevation on the project site drops from east to west as it approaches this adjacent pond. Water elevations in this adjacent pond were noted to be several feet lower than groundwater elevations in the inlets along the south side of the mall during the summer and fall of 2020. GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT April 28, 2021 #200526 4 Since Well #2 is located in close proximity to the proposed Chamber E Stormtech System, the SHGW elevation in Well #2 (4841.25) was used for the design of Chamber E. Chamber E is designed so that the bottom of the stone storage layer is above this SHGW elevation. Similarly, since Well #3 is located in close proximity to Chambers A and B, the SHGW elevation in Well #3 (4839.69) was used for the design of these chambers. Chambers C and D are located approximately halfway between Wells # 2 and #3, so the SHGW elevation from both wells was averaged for the design of these 2 systems. This is based on the assumption that the GW table drops uniformly from east to west as mentioned previously. 4841.25 (Well #2) + 4839.69 (Well #3) = 9680.94 / 2 = 4840.47 Based on this calculation, the SHGW elevation used for design of Chambers C and D is 4840.47. The GW monitoring wells and their SHGW elevations have been added to the drainage area map in Appendix A for reference. Due to minimum cover requirements and the existing grades of the parking lot in the vicinity of these chamber systems, the bottoms of some of these chamber systems are extremely close to the SHGW elevation. However, it should be noted that this peak SHGW elevation is only expected to be maintained for several weeks in the spring each year. For the majority of the year, these chambers systems are expected to be located several feet above the water table. For reference, the average groundwater elevation in the inlets along the south side (front) of the mall was measured at elevation 4838.90 during the summer of 2020. PROPOSED STORMWATER DESIGN Storm sewer pipes were sized to convey the 25-yr storm using Manning’s Equation. For each inlet, the contributing area, weighted C factor, and time of concentration were calculated. These values were input into Manning’s Equation to check capacity and flow characteristics for inlets and storm drain pipes. For the purposes of this report, each pipe section was named to match the associated upstream structure. Pipe sizing calculations are included in Appendix B. The proposed ponds and StormTech infiltration systems are sized according to City of Bozeman Design Standards to capture and retain or detain the volume of the 10-year 2-hour storm event. GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT April 28, 2021 #200526 5 The proposed stormwater design for the re-development area of the Mall includes the use of a series of stepped retention ponds and five StormTech infiltration systems to capture and treat runoff from the 10-year 2-hour storm event. Runoff generated from larger storm events such as the 25-year or 100-year events will pond in the low points of the parking lot in front of the Mall and will either infiltrate into the StormTech systems, or flow west across the parking lot to the pond in the adjacent park. The parking lot in front of the mall was modeled in case ponding occurred from a large storm event. This parking area in front of the mall is capable of holding an additional 35,000 ft3 of water below the sidewalk elevation along the front of the mall. However, the parking lot grading is such that diversion of the ponded stormwater to the adjacent park to the west is much more likely than a large ponding event. RETENTION POND DESIGN The stepped retention ponds will capture and treat runoff from the proposed north / south drive entrance and proposed buildings along the eastern side of the redevelopment area. The ponds are designed to hold a maximum water storage depth of 1.0’ during the design storm event, and are 2.5’ deep overall. The ponds will collect runoff from the adjacent drive lanes via curb cuts, and will be stepped so that in the case of a large storm event water can overtop the higher ponds and flow into the downstream ponds. The ponds are anticipated to capture and retain runoff from the majority of smaller storm events, but during the 10-year storm event water will enter a StormTech infiltration chamber that is located beneath the last pond in the chain. Since the proposed retention ponds are located over existing asphalt parking lot, the proposed design for the Retention Ponds includes over-excavating the pond footprint down to the native gravel depth. This excavation will be backfilled with a well-draining gravel to provide a conduit for the stormwater to infiltrate through. Above the gravel drain, the pond will be finish graded with 6” of topsoil and seeded based on the landscaping plan recommendations. GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT April 28, 2021 #200526 6 INFILTRATION CHAMBER DESIGN The StormTech infiltration systems will be placed at the north end of the re-developed parking lot and will collect runoff from the parking lot and the roof drains from the proposed grocery building. The majority of the existing parking lot asphalt will be preserved where possible and is graded to low points in the landscape islands south of the drive lane along the front of the Mall. The proposed StormTech infiltration chambers are designed to detain stormwater runoff using the arch-shaped chambers and void space in the surrounding washed rock, while the runoff infiltrates into the ground. Similar to the retention pond design, the footprint of these chambers will be over-excavated down to native gravels to remove any existing parking lot fill beneath the chambers. This excavation will be back-filled with a well-draining gravel to ensure infiltration. The chambers were sized by applying an infiltration rate for gravel subgrades to the footprint area of the chambers to determine the discharge (infiltrate rate) from each system. These discharge rates were then compared to the proposed inflow rates from the contributing areas to the systems during the 10-year 2-hour storm event to determine the required detention volumes for each system. The gravel infiltration rate used for these sizing calculations was determined to be 26 inches per hour. This infiltration rate was calculated by averaging the infiltration rates from 2 sets of Falling head infiltration tests that were performed on the gravel subgrade beneath the mall parking lot this winter. An explanation of how these tests were performed as well as their results, can be found in Appendix C. The following table provides the proposed pond and StormTech Chambers sizes, depths, and storage volumes. Calculations used to determine these system sizes can be found in Appendix B. Details on the design of the StormTech Chambers can be found in Appendix D. GALLATIN VALLEY MALL RE-DEVELOPMENT – STORMWATER DESIGN REPORT April 28, 2021 #200526 7 Table 1 Pond / Chamber Contributing Drainage Areas Contributing Area (SF)C-Value Pond Storage Depth (FT) Infiltration Area (Sf) Required Storage Volume (CF) Chamber A 1 78,780 0.86 N/A 1,360 1,483 Chamber B 2, 2A-E 84,005 0.77 N/A 1,241 1,432 Chamber C 3, 4 105,010 0.87 N/A 1,760 2,012 Chamber D 5, 6 56,862 0.76 N/A 855 941 Chamber E 5 94,242 0.87 N/A 1,206 1,496 Pond A-1 5 94,242 0.87 1.00 N/A 108 Pond A-2 5 94,242 0.87 1.00 N/A 432 Pond A-3 5 94,242 0.87 1.00 N/A 140 Pond A-4 5 94,242 0.87 1.00 N/A 95 Pond A-5 5 94,242 0.87 1.00 N/A 108 Pond A-6 5 94,242 0.87 1.00 N/A 162 2,5412,090 Provided Storage Volume (CF) 1,692 1,537 2,208 1,054 APPENDIX A Drainage Area Map APPENDIX B Storm Sewer Facilities Calculations DRAINAGE AREA # 1 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 69845 66353 Landscape 0.2 8934 1787 Total 78780 68140 A = Area (acres)1.81 C = Weighted C Factor 0.86 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 2.33 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)454 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)3.00 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft)0.13 (0.15' below top of curb) S = slope (ft/ft)0.0152 L = length of gutter (ft)29 V = mean velocity (ft/s)3.69 Tc Gutter Flow (minutes) =0.13 Tc Total =5.00 DRAINAGE AREA # 2 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 32117 30511 Landscape 0.2 1660 332 Total 33777 30843 A = Area (acres)0.78 C = Weighted C Factor 0.91 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 2.04 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)466 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)3.18 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft)0.13 (0.15' below top of curb) S = slope (ft/ft)0.0062 L = length of gutter (ft)13 V = mean velocity (ft/s)2.35 Tc Gutter Flow (minutes) =0.09 Tc Total =5.00 DRAINAGE AREA # 2A 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Roof 0.95 6963 6615 Landscape 0.2 16122 3224 Total 23085 9839 A = Area (acres)0.53 C = Weighted C Factor 0.43 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 5.04 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.20 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)110 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)10.07 Tc Total =10.07 DRAINAGE AREA # 2B 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Roof 0.95 2246 2133 Landscape 0.2 0 0 Total 2246 2133 A = Area (acres)0.05 C = Weighted C Factor 0.95 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.50 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)40 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.03 Tc Total =5.00 DRAINAGE AREA # 2C 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2)C * Area Hardscape 2C 0.95 1275 1211 Landscape 2C 0.20 385 77 Total 1659 1288 A = Area (acres)0.04 C = Weighted C Factor 0.78 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 2.81 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)120 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.45 Tc Total =5.00 DRAINAGE AREA # 2D 1. Calculate Area and Weighted C Factor Contributing Area DA C Area (ft 2)C * Area Roof 2D 0.95 23239 22077 Total 23239 22077 A = Area (acres)0.53 C = Weighted C Factor 0.95 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.00 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)110 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.96 Tc Total =5.00 DRAINAGE AREA # 3 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 93217 88556 Landscape 0.2 11793 2359 Total 105010 90915 A = Area (acres)2.41 C = Weighted C Factor 0.87 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.81 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)706 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)4.08 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft)0.13 (0.15' below top of curb) S = slope (ft/ft)0.006 L = length of gutter (ft)13 V = mean velocity (ft/s)2.32 Tc Gutter Flow (minutes) =0.09 Tc Total =5.00 DRAINAGE AREA # 4 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 38005 36104 Landscape 0.2 14585 2917 Roof 0.95 4273 4059 Total 56862 43080 A = Area (acres)1.31 C = Weighted C Factor 0.76 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.35 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)351 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)3.17 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft)0.13 (0.15' below top of curb) S = slope (ft/ft)0.0188 L = length of gutter (ft)441 V = mean velocity (ft/s)4.11 Tc Gutter Flow (minutes) =1.79 Tc Total =5.00 DRAINAGE AREA # 5 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 62883 59739 Landscape 0.2 10532 2106 Total 73415 61845 A = Area (acres)1.69 C = Weighted C Factor 0.84 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 2.59 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)266 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)2.22 Tc Gutter Flow Tc = L/V/60 V = (1.486/n)R2/3 S1/2 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft)0.13 (0.15' below top of curb) S = slope (ft/ft)0.0093 L = length of gutter (ft)153 V = mean velocity (ft/s)2.90 Tc Gutter Flow (minutes) =0.88 Tc Total =5.00 DRAINAGE AREA # 6 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2 )C * Area Hardscape 0.95 1453 1381 Landscape 0.2 0 0 Total 1453 1381 A = Area (acres)0.03 C = Weighted C Factor 0.95 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc = 1.87 (1.1-CCf)D1/2/S1/3 Storm S = Slope of Basin (%) 1.50 Return (yrs)Cf C = Rational Method Runoff Coefficient 0.95 2 to 10 1 Cf = Frequency Adjustment Factor 1.1 11 to 25 1.1 D = Length of Basin (ft)70 26 to 50 1.2 51 to 100 1.25 Tc Overland Flow (minutes)1.37 Tc Total =5.00 Chamber A REQUIRED VOLUME 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area DA C Area (ft2 )C * Area Hardscape 1 0.95 69845 66353 Landscape 1 0.20 8934 1787 Total 78780 68140 A = Area (acres) 1.81 Storm C = Weighted C Factor 0.86 Return (yrs)Cf 2 to 10 1 2. Calculate Infiltration Rate 11 to 25 1.1 Existing Soil Condition =Gravel 26 to 50 1.2 Percolation Rate (in/hour) =26 51 to 100 1.25 Percolation Rate (ft/sec) =0.00060 Infiltration Length (ft) = 56 Infiltration Width (ft) = 25 Infiltration Area (sf) = 1360 Total Area (acres) =1.81 acres Weighted C =0.86 Discharge Rate (cfs) =0.82 cfs Duration(min)Duration (hrs) Intensity (in/hr)Qin (cfs)Runoff Volume Release Volume Required Storage (ft3) 12 0.20 1.82 2.85 2,052 589 1,463 13 0.22 1.73 2.71 2,110 638 1,472 14 0.23 1.65 2.58 2,166 688 1,478 15 0.25 1.58 2.47 2,219 737 1,482 16 0.27 1.51 2.36 2,269 786 1,483 17 0.28 1.45 2.27 2,318 835 1,483 18 0.30 1.40 2.19 2,365 884 1,481 19 0.32 1.35 2.11 2,410 933 1,477 20 0.33 1.31 2.04 2,454 982 1,471 21 0.35 1.27 1.98 2,496 1,031 1,464 PROVIDED VOLUME (ft3)1,692 Chamber B REQUIRED VOLUME 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area DA C Area (ft2 )C * Area Hardscape 2 0.95 32117 30511 Landscape 2 0.20 1660 332 Roof 2A 0.95 6963 6615 Landscape 2A 0.20 16122 3224 Roof 2B 0.20 2246 449 Hardscape 2C 0.95 1275 1211 Landscape 2C 0.20 385 77 Roof 2D 0.95 23239 22077 Total 84005 64496 A = Area (acres) 1.93 Storm C = Weighted C Factor 0.77 Return (yrs)Cf 2 to 10 1 2. Calculate Infiltration Rate 11 to 25 1.1 Existing Soil Condition =Gravel 26 to 50 1.2 Percolation Rate (in/hour) =26 51 to 100 1.25 Percolation Rate (ft/sec) =0.00060 Infiltration Length (ft) = 42 Infiltration Width (ft) = 32 Infiltration Area (sf) = 1241 Total Area (acres) =1.93 acres Weighted C =0.77 Discharge Rate (cfs) =0.747 cfs Duration(min)Duration (hrs) Intensity (in/hr)Qin (cfs)Runoff Volume Release Volume Required Storage (ft3)15 0.25 1.58 2.33 2,100 672 1,428 16 0.27 1.51 2.24 2,148 717 1,431 17 0.28 1.45 2.15 2,194 762 1,432 18 0.30 1.40 2.07 2,238 807 1,432 19 0.32 1.35 2.00 2,281 852 1,430 20 0.33 1.31 1.94 2,322 896 1,426 21 0.35 1.27 1.87 2,362 941 1,421 22 0.37 1.23 1.82 2,401 986 1,415 PROVIDED VOLUME (ft3)1,537 Chamber C REQUIRED VOLUME 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area DA C Area (ft2 )C * Area Hardscape 3 0.95 93217 88556 Landscape 3 0.20 11793 2359 Roof 3 0.95 0 0 Total 105010 90915 A = Area (acres) 2.41 Storm C = Weighted C Factor 0.87 Return (yrs)Cf 2 to 10 1 2. Calculate Infiltration Rate 11 to 25 1.1 Existing Soil Condition =Gravel 26 to 50 1.2 Percolation Rate (in/hour) =26 51 to 100 1.25 Percolation Rate (ft/sec) =0.00060 Infiltration Length (ft) = 63 Infiltration Width (ft) = 28 Infiltration Area (sf) = 1760 Total Area (acres) =2.41 acres Weighted C =0.87 Discharge Rate (cfs) =1.06 cfs Duration(min)Duration (hrs) Intensity (in/hr)Qin (cfs)Runoff Volume Release Volume Required Storage (ft3) 13 0.22 1.73 3.61 2,815 826 1,989 14 0.23 1.65 3.44 2,889 890 2,000 15 0.25 1.58 3.29 2,960 953 2,007 16 0.27 1.51 3.15 3,028 1,017 2,011 17 0.28 1.45 3.03 3,093 1,081 2,012 18 0.30 1.40 2.92 3,155 1,144 2,011 19 0.32 1.35 2.82 3,215 1,208 2,008 20 0.33 1.31 2.73 3,274 1,271 2,002 21 0.35 1.27 2.64 3,330 1,335 1,995 22 0.37 1.23 2.56 3,385 1,398 1,986 PROVIDED VOLUME (ft3)2,208 Chamber D REQUIRED VOLUME 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area DA C Area (ft 2)C * Area Hardscape 4 0.95 38005 36104 Landscape 4 0.20 14585 2917 Roof 4 0.95 4273 4059 Total 56862 43080 A = Area (acres) 1.31 Storm C = Weighted C Factor 0.76 Return (yrs)Cf 2 to 10 1 2. Calculate Infiltration Rate 11 to 25 1.1 Existing Soil Condition =Gravel 26 to 50 1.2 Percolation Rate (in/hour) =26 51 to 100 1.25 Percolation Rate (ft/sec) =0.00060 Infiltration Length (ft) =49 Infiltration Width (ft) =18 Infiltration Area (sf) =855 Total Area (acres) =1.31 acres Weighted C =0.76 Discharge Rate (cfs) =0.51 cfs Duration(min)Duration (hrs) Intensity (in/hr)Qin (cfs)Runoff Volume Release Volume Required Storage (ft3) 12 0.20 1.82 1.80 1297 371 927 13 0.22 1.73 1.71 1334 401 933 14 0.23 1.65 1.63 1369 432 937 15 0.25 1.58 1.56 1403 463 939 16 0.27 1.51 1.49 1435 494 941 17 0.28 1.45 1.44 1465 525 941 18 0.30 1.40 1.38 1495 556 939 19 0.32 1.35 1.34 1524 587 937 20 0.33 1.31 1.29 1551 618 934 21 0.35 1.27 1.25 1578 648 930 PROVIDED VOLUME (ft3)1,054 Chamber E REQUIRED VOLUME 1. Calculate Area and Weighted C Factor (Post-Development) Contributing Area DA C Area (ft2 )C * Area Hardscape 5 0.95 62883 59739 Landscape 5 0.20 10532 2106 Roof 5 0.95 20827 19786 Total 94242 81631 A = Area (acres) 2.16 Storm C = Weighted C Factor 0.87 Return (yrs)Cf 2 to 10 1 2. Calculate Infiltration Rate 11 to 25 1.1 Existing Soil Condition =Gravel 26 to 50 1.2 Percolation Rate (in/hour) =26 51 to 100 1.25 Percolation Rate (ft/sec) =0.00060 Infiltration Length (ft) = 49 Infiltration Width (ft) = 25 Infiltration Area (sf) = 1206 Total Area (acres) =2.16 acres Weighted C =0.87 Discharge Rate (cfs) =0.73 cfs Duration(min)Duration (hrs) Intensity (in/hr)Qin (cfs)Runoff Volume Release Volume Required Storage (ft3) 22 0.37 1.23 2.30 3,039 958 2,081 23 0.38 1.19 2.24 3,087 1,002 2,085 24 0.40 1.16 2.18 3,133 1,045 2,088 25 0.42 1.13 2.12 3,178 1,089 2,089 26 0.43 1.10 2.07 3,222 1,132 2,090 27 0.45 1.08 2.02 3,265 1,176 2,089 28 0.47 1.05 1.97 3,307 1,219 2,087 29 0.48 1.03 1.92 3,348 1,263 2,085 30 0.50 1.00 1.88 3,388 1,307 2,081 31 0.52 0.98 1.84 3,427 1,350 2,077 PROVIDED VOLUME (ft3) POND A-1 108 POND A-2 432 POND A-3 140 POND A-4 95 POND A-5 108 POND A-6 162 CHAMBER E 1496 PROVIDED VOLUME (ft3)2,541 PIPE # 1 REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA # C Area (ft 2)C * Area Hardscape 1 0.95 69845 66353 Landscape 1 0.20 8934 1787 Total 78780 68140 A = Area (acres) 1.81 C = Weighted C Factor 0.86 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #1) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.86 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 1.81 (calculated above) Q 25-yr Pipe Flow Rate (cfs)= 5.99 MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY) PIPE # 1 Location: ST INLET 1 OUTLET PIPE INPUT D= 15 inches d= 14.07 inches Mannings Formula n= 0.013 mannings 57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.02 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.013 1.20 3.30 0.36 8.22 9.83 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d  D PIPE # 2 REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA # C Area (ft 2)C * Area Hardscape 2 0.95 32117 30511 Landscape 2 0.20 1660 332 Total 33777 30843 A = Area (acres) 0.78 C = Weighted C Factor 0.91 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #2) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.91 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 0.78 (calculated above) Q 25-yr Pipe Flow Rate (cfs)= 2.71 MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY) PIPE # 2 Location: ST INLET 2 OUTLET PIPE INPUT D= 12 inches d= 11.26 inches Mannings Formula n= 0.013 mannings 57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.01 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.013 0.77 2.64 0.29 5.01 3.83 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d  D PIPE # 2B REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA # C Area (ft 2)C * Area Roof 2A 0.95 6963 6615 Landscape 2A 0.20 16122 3224 Roof 2B 0.95 2246 2133 Total 25330 11973 A = Area (acres) 0.58 C = Weighted C Factor 0.47 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.17 (DA #2A) i = rainfall intensity (in./hr.) 2.44 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.47 (calculated above) i = rainfall intensity (in./hr.) 2.44 (calculated above) A = Area (acres) 0.58 (calculated above) Q 25-yr Pipe Flow Rate (cfs)= 0.67 MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY) PIPE # 2B Location: STMH 2B-4 INPUT D= 8 inches d= 7.50 inches Mannings Formula n= 0.013 mannings 57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.0075 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.013 0.34 1.76 0.19 3.31 1.13 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d  D PIPE # 2C-1 REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA # C Area (ft2)C * Area Hardscape 2C 0.95 1275 1211 Landscape 2C 0.2 385 77 Total 1659 1288 A = Area (acres) 0.04 C = Weighted C Factor 0.78 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs)0.08 (DA #2c) i = rainfall intensity (in./hr.)3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.78 (calculated above) i = rainfall intensity (in./hr.)3.83 (calculated above) A = Area (acres)0.04 (calculated above) Q 25-yr Pipe Flow Rate (cfs)=0.11 MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY) PIPE # 2C-1 Location: STMH 2C-1 INPUT D= 6 inches d= 5.63 inches Mannings Formula n= 0.013 mannings 57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.006 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.013 0.19 1.32 0.15 2.44 0.47 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d  D PIPE # 2C-2 REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA # C Area (ft 2)C * Area Roof 2A 0.95 6963 6615 Landscape 2A 0.20 16122 3224 Roof 2B 0.95 2246 2133 Hardscape 2C 0.95 1275 1211 Landscape 2C 0.20 385 77 Total 26989 13260 A = Area (acres) 0.62 C = Weighted C Factor 0.49 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.17 (DA #2A) i = rainfall intensity (in./hr.) 2.44 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.49 (calculated above) i = rainfall intensity (in./hr.) 2.44 (calculated above) A = Area (acres) 0.62 (calculated above) Q 25-yr Pipe Flow Rate (cfs)= 0.74 MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY) PIPE # 2C-2 Location: STMH 2C-2 INPUT D= 12 inches d= 11.26 inches Mannings Formula n= 0.013 mannings 57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.0075 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.013 0.77 2.64 0.29 4.34 3.32 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d  D PIPE # 2D REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA # C Area (ft 2)C * Area Roof 2D 0.95 23239 22077 Total 23239 22077 A = Area (acres) 0.53 C = Weighted C Factor 0.95 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs) 0.08 (DA #2D) i = rainfall intensity (in./hr.) 3.83 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.95 (calculated above) i = rainfall intensity (in./hr.) 3.83 (calculated above) A = Area (acres) 0.53 (calculated above) Q 25-yr Pipe Flow Rate (cfs)= 1.94 MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY) PIPE # 2D Location: ST INLET 2D-5 OUTLET PIPE INPUT D= 12 inches d= 11.26 inches Mannings Formula n= 0.013 mannings 57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.006 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.013 0.77 2.64 0.29 3.88 2.97 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d  D PIPE # 2E REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA # C Area (ft 2 ) C * Area Roof 2A 0.95 6963 6615 Landscape 2A 0.20 16122 3224 Roof 2B 0.20 2246 449 Hardscape 2C 0.95 1275 1211 Landscape 2C 0.20 385 77 Roof 2D 0.95 23239 22077 Total 50229 33653 A = Area (acres) 1.15 C = Weighted C Factor 0.67 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs)0.17 (DA #2A) i = rainfall intensity (in./hr.)2.44 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.67 (calculated above) i = rainfall intensity (in./hr.)2.44 (calculated above) A = Area (acres)1.15 (calculated above) Q 25-yr Pipe Flow Rate (cfs)=1.89 MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY) PIPE # 2E Location: ST MH 2E OUTLET PIPE INPUT D= 12 inches d= 11.26 inches Mannings Formula n= 0.013 mannings 57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.01 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.013 0.77 2.64 0.29 5.01 3.83 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d  D PIPE # 2F REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor Contributing Area DA # C Area (ft 2)C * Area Hardscape 2 0.95 32117 30511 Landscape 2 0.2 1660 332 Roof 2A 0.95 6963 6615 Landscape 2A 0.20 16122 3224 Roof 2B 0.20 2246 449 Hardscape 2C 0.95 1275 1211 Landscape 2C 0.20 385 77 Roof 2D 0.95 23239 22077 Total 84005 64496 A = Area (acres) 1.93 C = Weighted C Factor 0.77 2. Calculate Rainfall Intensity (Duration = Max Tc from Contributing Drainage Areas) i = 0.78x-0.64 (25-yr Storm, Fig. I-3, COB Design Standards) x = storm duration (hrs)0.17 (DA #2A) i = rainfall intensity (in./hr.)2.44 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.77 (calculated above) i = rainfall intensity (in./hr.)2.44 (calculated above) A = Area (acres)1.93 (calculated above) Q 25-yr Pipe Flow Rate (cfs)=3.62 MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY) PIPE # 2F Location: ST INLET 2F OUTLET PIPE INPUT D= 15 inches d= 14.07 inches Mannings Formula n= 0.013 mannings 57.7 degrees Q=(1.486/n)ARh2/3S1/2 S= 0.01 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh2/3S1/2 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Area,ft2 Wetted Perimeter, ft Hydraulic Radius, ft velocity ft/s flow, cfs PVC 0.013 1.20 3.30 0.36 5.81 6.95 PE (<9"dia) 0.015 PE (>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 Manning's n-values d  D