Loading...
HomeMy WebLinkAbout012 TruNorth Stormwater Demand Report STORMWATER DESIGN REPORT FOR: THE TRU NORTH CENTER BOZEMAN, MT 0 ••® E-R I • A- R i N,G e No. 89370PE WWC Engineering/Madison 895 Technology Blvd Ste 203 Bozeman, MT 59718 (406) 586-0262 March 2024 TruNorth Center Stormwater System Report Introduction This design report will give an overview of the proposed stormwater system for the site of TruNorth Center located at the corner of East Main Street and Haggerty Lane. TruNorth Center is an individual Site Plan within a previously approved Master Site Plan. The property is located at Section 8, Township 2 South, Range 6 East, Block 1, Lot 1 of Plat H-29-E The stormwater system will include utilizing existing curb inlets, manholes, storm piping and on- site underground detention storage. Water will be conveyed by a combination of piping and sheet flow to the existing storm water collection system. The existing system was analyzed and has capacity for this development. The following references were used in the preparation of this report: a. City of Bozeman Modifications to Montana Public Works Standard Specifications. Sixth Edition, Addendum No 3 b. City of Bozeman Design Standards and Specifications Policy, March 2004, Addendum No. 7 c. Circular DEQ 8, Montana Standards for Subdivision Storm Drainage, 2002 Edition Existing Stormwater Facilities The existing stormwater facility was previously installed in 2018 during the construction of Heebs Grocery store (now Town and Country Grocery Store), a building included in the Master Site Plan. The site was installed with curb inlets, storm manholes, storm piping and a detention pond. The system discharges to an on-site underground detention pond and eventually distributes water to an existing wetland located on the East side of Haggerty Lane. The stormwater collection system was previously approved by the City of Bozeman but needed to be re-analyzed for the development of TruNorth Center. The Master Site Plan application featured a development with a slightly different building layout, thus requiring a review of the stormwater system. Existing curb inlets, storm manholes, storm piping and detention pond calculations were reviewed and updated. The existing structures that are being utilized are highlighted in Appendix D, KLJ Supporting Documents, for clarification. Existing Capacities The existing capacities of several structures were analyzed to determine if possible runoff/storage could be accommodated. The following structures were reviewed: Existing Curb Inlet#2 on East Main, Existing Curb Inlet#3 on Haggerty Lane, 36" Standard Inlet#2, 36" Standard Inlet#3, 24" Standard Inlet#14, Storm Pipe between Inlet#14 and#3, &underground detention storage. The calculations of the existing capacity,provided capacity, and additional TruNorth Center Stormwater System Report runoff proposed are shown in Appendix C, Existing Capacities—Based on KLJ's Report. These structures are also highlighted in Appendix D, KLJ Supporting Documents, for clarification. Peak Flow(Runoff) Calculations The project area was divided into drainage areas shown on the stormwater exhibit, provided in Appendix A. These areas were used to determine the stormwater runoff flows at 10-year, 25-year and 100-year storm events. To be conservative and cohesive with the previously approved KLJ report,the 100-year storm event was selected. Peak flow calculations are provided in Appendix B. The stormwater from the development will discharge to three designated locations. The Northern portion of the site will continue to discharge to the existing curb inlet located within East main via sheet flow. The Eastern portion of the site will continue to discharge to the existing curb inlet located within Haggerty Lane via sheet flow. The Southern portion and majority of the site will discharge to existing underground detention system by a combination of sheet flow to inlets and underground roof drain piping that connects to the existing 24" standard inlet #14. All three designated locations distribute water to the wetlands located East of Haggerty Lane. The existing curb inlets, manholes,piping, and detention storage have additional capacity to accommodate this runoff. Conclusion To be conservative and based on slight changes to the drainage plan, existing inlets #14, #2 and #3 were all calculated based off the total square footage of 1,558 sf. This allowed for each inlet to show that it can handle the worst-case scenario for additional runoff from the development. Based on the calculations provided in the appendix, the existing system has the capacity to accommodate additional runoff from the proposed TruNorth development. Appendices A. Stormwater Exhibit B. Peak Flow Calculations C. Existing Capacities—Based on KLJ's report. D. KLJ Supporting Documents. TruNorth Center Stormwater System Report A. Stormwater Exhibit w 0 m z 3 EAST MAIN ST EXISTING CURB INLET #2 p� PER KLJ STORM REPORT. POO\•C 'ao'6'v SCALE o 0 0 15' '� -� s z�s �As z°s s eAs/L s �As eAs �As ryas uAr =, �- �„s �as UP UP UP UP UF' UP UP UP \ IIP —lip UP UP UP UP \ DISCHARGES TO EXISTING EAST MAIN INLET(EX2) RUNOFF AREA #3 TO si /� 1 g \4815 EXISTING CURB INLET \ \ I S 6` s� TOTAL AREA = 218 SF - - - - - - - - - - - - - \\- - - - - - S\ - O -\ - IESS ❑❑❑❑ \ N.1. 2S E IFFR L. \ 1 RUNOFF AREA #4 NO LONGER INCLUDED -%ry` I'^ I I FOR EXISTING CURB INLET #3. \ 1340 EAST A 1 DISCHARGED TO PRIVATE SITE DETENTION. RUNOFF AREA #1 TO A TOTAL AREA = 361 SF I EXISTING CURB INLET #2 MAIN ST DRAWN BY: JMW � � � � _ TOTAL AREA = 187 SF III 1 1 1 s F 11 1 A REVIEWED BY: CGB I e ° 1 \�' ZI? PROJECT ENGINEER:CGB I I RUNOFF AREA #2 NO LONGER INCLUDED \� �� 1 I \ ��^\ FOR EXISTING CURB INLET #2 A 1 I \ d\ DESIGNED BY:CGB I DISCHARGES TO PRIVATE SITE DETENTION \ DISCHARGES TO r �R TOTAL AREA = 727 sF. US EXISTING HAGGARTY y RF P u i i........ V V \ 1 I I INLET(EX3) IM ❑ � I I ❑ \-� \ \ �WS WS WSJ 1 1 \ RUNOFF AREA F,L� IH E S FS FS FS \ 1 \ EXISTING CURB INLET #3 [p� JV/E o V y 1 G E G I A TOTAL AREA = 145 SF ^) M 1342 EAST �M MAIN ST T \� \ / EXISTING CURB INLET1 \ _ DISCHARGES TO / E r I I \ PER KLJ STORM wl \ PRIVATE SITE c 4 REPORT. \ \ /I 1 ❑ DETENTION PI / G EXISTING 36" ❑ STANDARD INLET #14 Is I\ P� EXT'G CURB & GUTTER P r� \ I RUNOFF AREA #6 NO LONGER INCLUDED / 11 \ \1 I •�� WS WS FOR EXISTING CURB INLET #3 IFS F F F FS s FS FS— DISCHARGES TO PRIVATE SITE DETENTION \ I' TOTAL AREA = 615 SF. ElIT � � \ EXT'G EXT'G I EXISTING STORM PIPE I \ sf \�� ' PAVEMENT '^ BETWEEN INLET #14 AND I \ \INLET #3 I \\ \ \ PAVEMENT 3 \ \ Q �r \ \ - - - --------------- ST \`EXISTING36„ 1 \ \ \ S ST STANDARD INLET #2 I \I EXTISTING - - - - V \ �°TA A � EXISTING 36 �\ UNDERGROUND __ _ _ _ I\ " 3 STANDARD INLET #3 \.\ - DETENTION STORAGE -' -- \.�A\ o W e L STORMWATER DRAINAGE EXHIBIT LEGEND OVERALL AREAS: bl � BLUE = PROPOSED RUNOFF BASINS RED = EXISTING RUNOFF BASINS EXT'G CURB INLET #2 - EAST MAIN ® -322 SF BEING DISCHARGED TO EXT'G Cl #2 AREA OF OVERLAP FROM SP AND MSP EXT'G UNDERGROUND DETENTION - ON-SITE P1 V SHEET NOTES: #1 = 187 SF 1,558 SF BEING DISCHARGED TO ON-SITE P-1 AREAAREA #2 = 727 SF EXT'G CURB INLET #3 - HAGGERTY LANE Y STORM AREA #3 = 218 SF -831 SF BEING DISCHARGED TO EXT'G Cl #3 AREA #4 = 361 SF TRUNORTH CENTER AREA #5 = 145 SF STORMWATER AREA #6 = 615 SF o S PROJECT:23-102 a DATE:FEBRUARY 2023 B. Peak Flow Calculations TruNorth Center Peak Flow Calculations(cfs) Peak Flow Summary(cfs) Area Design Rainfall Freq. (Acre) C 100 Yr 25 Yr 10 Yr Ext'g Cl#2-East Main -0.008 0.80 -0.06 -0.03 -0.02 On-Site Inlet#14 0.036 0.80 0.24 0.10 0.07 Ext'g Cl#3-Haggerty Lane -0.019 0.80 -0.21 -0.09 -0.06 On-Site Inlet#3 0.036 0.80 0.35 0.14 -0.06 On-Site Inlet#2 0.800 0.80 0.26 0.11 0.07 Storm Information Design Rainfall Freq. 100 25 10 IDF coefficient a 1.01 0.78 0.64 IDF coefficient b 0.00 0.00 0.00 IDF coefficient n 0.67 0.64 0.65 Adjustment Factor Cf: 1.25 1.1 1 Peak Q Values for Roadway Discharge to Ext'q Curb Inlet#2 East Main Total Area: -0.008 acres -322 SF Composite C: 0.80 (COB STDS) Average slope: 1.50 percent Travel Distance 166.00 feet Design Rainfall Freq. 100 25 10 C*Cf 1.00 0.88 0.80 (Shall not exceed 1.00) Total tc: 2.10 4.63 6.31 minutes intensity at t, 9.53 4.02 2.77 in/hr peak runoff: -0.06 -0.03 -0.02 cfs Discharge to On-site Detention Standard Inlet#14 Total Area: 0.036 acres 1,558 SF C: 0.80 (COB STDS) Average slope: 1.50 percent Travel Distance 240.00 feet Design Rainfall Freq. 100 25 10 C*Cf 1.00 0.88 0.80 (Shall not exceed 1.00) Total tc: 2.53 5.57 7.59 minutes intensity at tc 8.42 3.57 2.45 in/hr peak runoff: 0.24 0.10 0.07 cfs Discharge to Ext'q Curb Inlet#3 Haggerty Lane Total Area: -0.019 acres -831 sf C: 0.80 (COB STDS) Average slope: 1.50 percent Travel Distance 53.00 feet Design Rainfall Freq. 100 25 10 C*Cf 1.00 0.88 0.80 (Shall not exceed 1.00) Total tc: 1.19 2.62 3.57 minutes intensity at tc 13.97 5.79 4.01 in/hr peak runoff: -0.21 -0.09 -0.06 cfs TruNorth Center Storm Design Page 1 of 2 TruNorth Center Peak Flow Calculations(cfs) Peak Q Values for Roadway Discharge to On-site Detention Standard Inlet#3 Total Area: 0.036 acres 1,558 SF C: 0.80 (COB STDS) Average slope: 1.50 percent Travel Distance 81.00 feet Design Rainfall Freq. 100 25 10 C*Cf 1.00 0.88 0.80 (Shall not exceed 1.00) Total tc: 1.47 3.23 4.41 minutes intensity at t, 12.12 5.06 3.49 in/hr peak runoff: 0.35 0.14 0.10 cfs TruNorth Center Storm Design Page 2 of 2 C. Existing Capacities — Based on KLJ Report TruNorth Center Curb Inlet, Storm Manhole, Pipe & Detention Capacity Calculations Capacity- Based on KLJ Report EX Curb Inlet#2 - East Main EX Curb Inlet#3 - Haggerty Q (Capacity)= 5.57 cfs (100yr Pred) Q(Capacity) =9.44 cfs (100yr Pred) Q (Provided)= 1.15 cfs (100yr Post) Q (Provided)= 1.79 cfs (100yr Post) Q (Added)=-0.06cfs (100yr) Q (Added)= -0.21 cfs (100yr) Q (provided) > Q(updated) = Q (provided) > Q(updated) _ 1.15 cfs > 1.09 cfs 1.79 cfs > 1.58 cfs 24" Standard Inlet#14 36" Standard Inlet#3 Q(Capacity) = 6.83 cfs Q (Capacity) = 5.38 cfs Q (Provided) = 1.20 cfs Q (Provided)= 1.12 cfs Q (Added) = 0.24 cfs (100yr) Q (Added) = 0.35 cfs (100yr) Q(capacity) > Q (updated) = Q (capacity) > Q(updated) _ 6.83 cfs > 1.44 cfs 5.38 cfs > 1.47 cfs 24" Standard Inlet#2 Pipe Capacity Inlet 14-3 Q(Capacity) = 5.83 cfs Q (Capacity) = 3.41 cfs Q (Provided) = 2.15 cfs (100yr) Q (Provided) = 1.71 cfs (100yr) Q (Added) = 0.26 cfs (100 yr) Q (Added) = 0.24 cfs (100yr) Q(capacity) > Q(updated) = Q (capacity) > Q (updated) _ 5.83 cfs >2.41 cfs 3.41 cfs > 1.95 cfs P1 On-Site Detention Q (Capacity) =0.178 of storage Q (Provided) = 0.092 of storage Q (Added)0.0014 of storage Q (capacity) > Q updated = 0.178 of>0.093 of TruNorth Center Capacity Calculations Page 1 of 1 D. KLJ Supporting Documents EXHIBIT 1 - PRE-DEVELOPED DRAINAGE MAP EXHIBIT 1 - PRE-DEVELOPED DRAINAGE MAP BLACKMORE CROSSING PRE-DEVELOPED DRAINAGE DATA + r>` BASIN AREA TIME CF CONC.ID WEIGHTED Cn (ACRES) (MINUTES) 0.51 15.1 88 �Q / S'TRF�T ,. / / E-2 - 5.0 95 144 �/ksOJ E 3 3.86 16.7 92 Nq 1?9NF�FiOw Time of concentration assumed to reflect the pre-demolition state EX 2 NLET 2 POINTS OF FLOW FROM SITE FLOW RATE(CFS) EX 1 w C sHgLLo NCE4TRATED - LOCATION 2 YR 10 YR 100 YR INLET I) (PAV r sHEETFLDw �!/ 229' �\ 1 0.27 0.61 1.13 f `r ���/ O 2.06 3.54 5.57 r 1;- p SNP��OG�g51 E 3 /1f �,' - 3 2.91 5.59 9.44 1 W . z ' VW—, SHALLOW CONCENTRATiEb f ¢ (PAVED) i � � � `-,•-, `r�� Note: �. -,► + LEGEND Highlighted Information Is to show E-1 e'�a+i't � ►l �f BASIN general location of existing structures and/or is used in capacity 1 POINT OF DISCHARGE calculations. (. SHE OW 5 All ! {� DITCH O = i POND - n1 S\ r y Tc PATH CURTISS ST. "�Y 57 N 't o so ,00 <<KLI I F FEET Nov 08,2016-12:07pm-P:1PrivatelMT\CitylB0zemaM11415006 East Main CommerciakCadd+Model files\Drainage.dwg NN EXHIBIT Z - POST-DEVELOPED DRAINAGE MAP EXHIBIT 2 - POST-DEVELOPED DRAINAGE MAP BLACKMORE CROSSING • POST-DEVELOPED DRAINAGE DATA BASIN AREA TIME OF CONC. WEIGHTED Cn \ ~ • ID (ACRES) (MINUTES) E-1 0.37 8.4 87 E 2 E-2 0.49 14.1 89 \... O E-3 0.54 4 A 89 P-1 4.31 10.0* 97 IOfLE� 2 \ •Based on minimum for conservative analysis E \ POINTS OF FLOW FROM SITE FLOW RATE(CFS) LOCATION 2 YR 10 YR 100 YR \ I 1 N 1 0.22 0.51 0.96 Fp 3 O 0.30 0.63 1.15 o' P 3 2.90 5.58 13.36 1 � LEGEND E-1 e E 1 BASIN Note: Highlighted information is to show E 1 POINT OF DISCHARGE general location of existing structures ' J&H F 1R DITCH and/or is used in capacity POND calculations. � 1 ^ Tc PATH CURTI C� BASIN LINE N 2� so 100 K Ll SCALE FEET «v Nov 08,2016-12:07pm-P:1Private\MT\CitylBozeman%11415006 East Main Commercial\CaddWodel files\Drainage.dwg EXHIBIT 3 - INLET SIZING AND SCHEMATIC EXHIBIT 3 - PIPE SIZING AND SCHEMATIC INLET DATA BLACKMORE CROSSING INLET INLET CAPACITY, 100-YEAR TYPE IN 1 1 36"STD. 5.38 1.79 / / 0 LEGEND 2 36"STD. 5.38 2.15 E-2 E-1 BASIN 3 36"STD. 5.38 1.12 / 4 O POINT OF DISCHARGE 36"STD. 5.38 1.07 5 24"STD. 6.83 2.16 CATCHMENT AREA 6 36"STD. 5.38 1.68 S TAN AR BASIN LINE �1 I T 7 36"STD. 5.38 0.32 / ppp EX 2 INLET 2 8 24"STD. 6.83 1.02 / 17 / _ 9 24"STD. 6.83 0.97 b b 24-STAN D 10 24"STD. 6.83 0.96 � r INLE� Note: 1 Highlighted 11 24"STD. 6.83 0.11 E 1 7� 14 information is to 12 24"STD. 6.83 2.35 11 E O 24"STANDARD show general 13 24"STD. 6.83 0.07 INLET location of existing structures and /or is 14 24"STD. 6.83 1.20 24"STANDA n4 used in capacity 15 36"STD. 5.38 0.23 INLET 36"s1rANE calculations. 16 36"STD. 5.38 0.28 INLET 17 24"STD. 6.83 1.65 O a 1.ASSUMES 6"OF PONLING MAXIMUM. 00 �� N Rye � . ° 1 3 ..-. � PIPE DATA 36' ARD MANNINGS MANNING 100-YEAR PIPE SIZE SLOPE CAPACITY VELOCITY INFLOW 'A/ f n__1__ Y7 0 ID (INC-fES) (°io) (CFS) (FPS) (CFS) 17-4 12 1.85 4.86 6.19 1.65 5-4 12 1.00 3.57 4.55 2.16 6' STANdAR f� INLET 4-3 12 1.86 4.87 6.20 4.87 6 16-15 12 1.46 4.32 5.50 0.28 E-1 8 36" TAND I 15-14 12 1.00 3.57 4.55 0.51 INLET 24"STAN A 14-3 12 0.91 3.41 4.34 1.71 � INLE I E _ 9 12-11 12 1.00 3.57 4.55 2.35 7 24"STANDA 36"S 11-10 12 1.14 3.81 4.86 2.47 INL I LET 10-9 12 0.96 3.50 4.46 3.50 11 9-8 15 0.50 4.58 3.73 4.47 24"STANDARD �NLET 8-3 15 1.59 8.17 6.66 5.49 ❑ I 24"STANDA D 7-6 12 5.86 5.051. 6.431. 0.32 INLET "•-••---�-�..„„ . 6-2 12 10.35 5.051. 6.431. 2.00 ........... CU RTISS ST, --- ----- 12 1,MANNINGS EQLATION IS ONLY VALID FOR RELA-IVELY FLAT SLOPES. FOR PURPOSES OF THIS INLET ANALYSIS,SLOPES WERE LIMITEE TO2.00%. _ -_ - 13 D so o so ,00 K L' ll -._ INLE FEET SCALE \\ Oct 03,2)17-8:11 am-P:\Private\MT\City\B¢eman\11415006 cast Main Commercial\CaddWodel files\Drainage.dwg I EXHIBIT 4 - PRE-DEVELOPED DRAINAGE REPORT Post Dev - Matt C 10-21-16 Type 11 24-hr WQ Rainfall=0.50" Prepared by {enter your company name here) Printed 11/8/2016 HydroCAD® 10.00-14 s/n 07691 ©2015 HydroCAD Software Solutions LLC Page 45 Summary for Subcatchment P-1: BLACKMORE BEND SITE Runoff = 1.68 cfs @ 12.02 hrs, Volume= 0.092 af, �epth> 0.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr WQ Rainfall=0.50" Area (ac) CN Description 3.943 98 Paved parking, HSG D 0.368 84 50-75% Grass cover, Fair, HSG D 4.311 97 Weighted Average 0.368 8.54% Pervious Area 3.943 91.46% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Subcatchment P-1: BLACKMORE BEND SITE Hydrograph 1 �4hr' 1.68 cfsTy peIII WQ Rai4a1k 56 ku6o4ff Ar6a�=4.311 ac Runoff Wuwn&0.092 of 1 g Runoff Deptlh:�0.267 LL Tc=10.0 mint �NI 917 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Note: Highlighted information is to show general location of existing structures and/or is used in capacity calculations. Post Dev - Matt C 10-21-16 Type 1124-hr WQ Rainfall=0.50" Prepared by {enter your company name here) Printed 11/8/2016 HydroCAD® 10.00-14 s/n 07691 ©2015 HydroCAD Software Solutions LLC Page 52 Pond P1: DETENTION - Chamber Wizard Field A Chamber Model = ADS N-12 60 (ADS N-12®Pipe) Inside= 59.5"W x 59.5"H => 19.30 sf x 20.001 = 386.0 cf Outside= 67.0"W x 67.0"H => 22.91 sf x 20.001 = 458.2 cf 67.0" Wide + 23.0" Spacing = 90.0" C-C Row Spacing 6 Chambers/Row x 20.00' Long +5.58' Header x 2 = 131.17' Row Length +18.0" End Stone x 2 = 134.17' Base Length 3 Rows x 67.0" Wide + 23.0" Spacing x 2 + 18.0" Side Stone x 2 = 23.58' Base Width 6.0" Base + 67.0" Chamber Height + 6.0" Cover = 6.58' Field Height 18 Chambers x 386.0 cf+ 20.58' Header x 19.30 sf x 2 = 7,742.6 cf Chamber Storage 18 Chambers x 458.2 cf+ 20.58' Header x 22.91 sf x 2 = 9,191.2 cf Displacement 20,833.4 cf Field - 9,191.2 cf Chambers = 11,642.1 cf Stone x 0.0% Voids = 0.0 cf Stone Storage Chamber Storage = 7,742.6 cf= 0.178 of Overall Storage Efficiency = 37.2% 18 Chambers Note: 771.6 cy Field Highlighted information is to show 431.2 cy Stone general location of existing structures and/or is used in capacity calculations.