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Drainage Reports - 05/12/2017 (2)
�1 ATWELL City of Fort Collins Approved Plans Approved by Date: S i Final Drainage Report for Maverik City of Fort Collins, Colorado Developer: Maverik Inc. 880 West Center Street Salt Lake City, UT 84054 801.335.3851 Contact: Rick Magness Engineer: Atwell, LLC 143 Union Blvd, Suite 700 Lakewood, CO 80228 303.462.1100 Contact: Kevin J. Rohrbough, PE Project Number 15001770 February, 28 2017 1 I hereby certify that this Final Drainage Report for the design of Maverik was prepared by me or under my direct supervision in accordance with the provisions of the Urban Drainage and Flood Control District Manual and the Fort Collins ' Amendments for the owners thereof. I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by others. NL, Rigis-tdred P ofessional Engineer State of Colorado No. jqjq2 1 hereby certify that the drainage facilities for Maverik shall be constructed according to the design presented in this report. I understand that the City of Fort Collins does not and will not assume liability for the drainage facilities designed and/or certified by my engineer. I understand that the City of Fort Collins review drainage plans but cannot, on behalf of Maverik, guarantee that final drainage design review will absolve The Maverik, LLC and/or their successors and/or assigns of future liability for improper design. I further understand that approval of the Final Development Plan does not imply approval of my engineer's drainage design. ��Nc ame of Developer 7 Table of Contents General Location and Description 1 Drainage Basins and Sub -Basins 1 Drainage Design Criteria 4 Drainage Facility Design 6 Conclusions 6 References 7 Appendix A — Maps & Figures Historic and Developed Imperviousness Maps FIRM Map Hydrologic Soils Report Rainfall Intensity Runoff Coefficients Appendix B — Stormwater Calculations Composite Run-off Coefficients Time of Concentration Minor Storm Runoff Calculations Major Storm Runoff Calculations Detention Volume by Modified FAA Method Proposed Pond Volume Outlet Structure Design CRS Drain Time Calculations Inlet Calculations Spill Containment System SOP Historic Drainage Plan Back Pocket Final Drainage Plan Back Pocket ' AM1 L, LLC I. General Location and Description ' The purpose of this report is to provide a reference for the City of Fort Collins and the developer to use for the construction and maintenance of drainage facilities for the Maverik development site in Fort Collins, Colorado. The Maverik development site occupies 1.77 acres that is located in the Maverik Subdivision Filing No. 1. The site is located within the Northwest one -quarter of Section 15, Township 7 North, Range 68 West of the 6t' Principal Meridian. The parcel's street frontage is along 1-25 Frontage Road with an address of 4333 E. Mulberry Street. The site is bounded by the Americas Best Value Inn & Suites property to the south and west; Frontage Road to the east; and CDOT ROW for Intersate-25 to the north. A vicinity map is included within Appendix A of this report. The proposed development site currently has a round brick building that formerly served as a restaurant. The east side of the site generally slopes from north to south at about a 1 percent grade, while the west side generally slopes from east to west. Both sides of the site drain to grated inlets within the existing parking lot that discharge flow into an existing detention pond on the north side of the site. This detention pond has a 24" controlled ' outlet pipe that discharges to a roadside drainage swale along the 1-25 off -ramp to E. Mulberry Street. The swale conveys flows southwest to Boxelder Creek. Soils on the site are identified as Fort Collins loam, which is a Hydrologic Group B soil. Refer to the soils map in Appendix A of this report for additional soils information. The proposed use for the redeveloped property is a convenience store and fueling station. The proposed development will contain a convenience store replacing the existing restaurant building along with the fueling station to the northeast with surrounding parking. A rest area with tot lot and dog park will also be provided along the northeastern boundary. The development parcel lies within the limits of the Boxelder Creek Regional Master Plan. The project site is identified as outside of the 100-yr floodplain (Zone X) as shown on the flood insurance rate map number 08069C1003G, dated May 2, 2012 (a copy is included in Appendix A). III. Drainage Basins and Sub -Basins As stated in section I, the east side of the site generally slopes from north to south at Final Prainage peport Maverik WA I AMYL, PLC about 1 percent, while the west side generally slopes from east to west. Both the existing Americas Best Value Inn & Suites property and the proposed Maverik site will be analyzed as they both drain to an existing detention pond in the northwest corner of the proposed site. The outfall drainage way is identified as a tributary of Boxelder Creek in the aforementioned Regional Master Plan. Under existing conditions, runoff from the site reaches the outfall drainage way via area drains in the parking lot on the southwest side of the site and west of the pond. A fuel spill containment system is required around the fuel pumps and underground fuel storage tanks to prevent a fuel spill entering the stormwater system. A trench drain will be placed around the fuel pumps and tanks to collect any spilled fuel. The trench drains will be connected with PVC pipe to a concrete vault designed to trap up to 150 gallons of spilled fuel for cleanup. The vault will also allow drainage water to pass through, leaving the spilled fuel floating behind an internal baffle. The vault is connected to the existing storm pipe that drains to the detention pond with PVC pipe. A Standard Operating Procedures document (SOP) is included in Appendix B. Overall the site. (including the Americas Best Value Inn and Suites) has been divided into three main basins (A, B, and C) with Basin A being split into two -sub basins: Sub -Basin Al: (2.80 acres; Q100 = 18.7 cfs) Sub -Basin Al contains most of the existing Americas Best Value Inn & Suites site including the building, pool area and surrounding parking. The existing detention pond and southwest half of the proposed convenience store are also contained in Sub -Basin Al. All flows in Sub -Basin Al will drain to the existing detention pond through the existing storm sewer system located on site. Sub -Basin A2: (0.90 acres; Q100 = 7.1 cfs) Sub -Basin A2 contains much of the new construction including a portion of the convenience store, a portion of the new canopy, and much of the parking lot. Sub -Basin A2 drains to a proposed 2' valley pan and an existing grated inlet near the south driveway entrance which then conveys the flows to the existing detention pond through the existing storm system. In the case the existing inlet becomes clogged, the emergency flow path of Sub -Basin A2 is to the west where it will spill into the proposed valley pan within Sub -Basin A3 and ultimately to the detention pond through the proposed curb cut. Sub -Basin A3: (0.65 acres; Q100 = 4.6 cfs) Sub -Basin A3 contains much of the new construction including a portion of the convenience store, a portion of the new canopy, and the recreation area & dog park. Sub -Basin A3 drains to a proposed 2' valley pan Final Prainage keport Maverik PA6� 2 AMLL, LLC which then conveys the flows to the existing detention pond through a curb cut. The ' proposed 2' valley pans and curb cut will ensure positive drainage to the existing pond in the case of clogged inlets. Much of the fuel containment system is within Sub -Basin A-3 including much of the trench drain, the concrete containment vault, and PVC connection ' into the existing storm pipe. The trench drains around the underground fuel storage tanks and fuel pumps will capture spilled fuel and drain to the concrete vault that will trap the spilled fuel so it can be cleaned out before it enters the stormwater system. Any storm runoff that is also captured in the trench drains will pass through the vault while the spilled fuel is withheld. The vault is connects with PVC pipe to the existing storm pipe ' that drains into the detention pond. An SOP for the fuel spill containment system is included in Appendix B. Basin B: (0.08 acres; Q100 = 0.1 cfs) Basin B consists of a small strip of land in the northern corner of the site. The basin drains to the existing roadside ditch that is along the access road to the north and west of the site. Drainage from Basin B does not flow to the existing detention pond. ' Basin C: (0.12 acres; Q100 = 0.2 cfs) Basin C consists of a small strip of land on the southwest and southeast sides of the site between the existing parking area and property ' line. This small area sheet flows offsite to Frontage Road and the adjacent property to the southwest. ' Historic basins follow the same layout as the proposed basins with the only changes being Basin A will be split into three sub -basins with proposed development instead of the existing two sub -basins. For a comparison of Historic and Proposed basins, see the table below: Basin Historic Proposed Historic Proposed Historic Prop. Designation Area Area Q100 Q100 Imp. Imo. ' Basin A1: 2.92 ac. 2.80 ac. 19.5 cfs 18.7 cfs 83.9% 82.4% Basin A2: 1.43 ac. 0.90 ac. 8.8 cfs 7.1 cfs 65.9% 78.6% ' Basin A3----------------------- 0 �-- ac- 4-6 cfs 78.8% - - - Basin A: 4.35 ac. ------------ 4.35 ac. ------------ 28.3 cfs -------------------------- 30.4 cfs 78.8% 81.1 % ' ------------------------------------------------------------------------------------------------------------ Basin B: 0.09 ac. 0.08 ac. 0.2 cfs 0.01 cfs 10.0% 10.0% ' Basin C: 0.12 ac. 0.12 ac. 0.2 cfs 0.02 cfs 10.0% 10.0% Final brainacie peport Maverik PAGE 5 ATWFLL, LLC Additional information for all basins located in Appendix B of this report. III. Drainage Design Criteria Drainage analysis and stormwater facility design has been prepared in accordance with the Urban Drainage and Flood Control District's Urban Storm Drainage Criteria Manual and the Fort Collins Amendments to the UDFCD Criteria Manual. Historic and Developed runoff calculations for the 2-year and 100-year rainfall events have been completed using the rational method. Refer to the appendix of this report for rational calculations. Design rainfall was based on the City of Fort Collins Rainfall Intensity Table (Reference A). Runoff Coefficients were based on off City of Fort Collins Table RO-11. The 100 year storm had a 1.25x frequency factor applied. Detention Storage has been determined using the Modified FAA Method. A fuel spill containment system is required around the fuel pumps and underground fuel storage tanks to prevent a fuel spill entering the stormwater system. This system is described above and an SOP is included in Appendix B. The City of Fort Collins Low Impact Development (LID) requirements state that 25% of vehicle use pavements be pervious and 50% of impervious area be treated by LID techniques. Even though the site is an existing urban area and impervious amounts are only increasing from 78.0% to 81.1 % because of the convenience store and parking, the site will feature several LID techniques. An imperviousness map is included in Appendix A that shows the historic and developed conditions. The following table breaks down the LID usage on site. Approximately 4800 sf of updated parking area will utilize permeable pavers which represents two thirds of the total additional paved areas. Planters and trees will be added throughout the site including along perimeter roads and parking islands. Vegetative buffers will also be utilized along walks and parking areas. Final Prainage Veport Maverik PAGF 4 ' A11N LL, LLC 50% On -Site Treatment by LID Requirement New Impervious Area 6,147 sq. ft. Required Minimum Impervious Area to be Treated 3,074 sq. ft. Area of Paver Section #1 2,220 sq. ft. Run-on area for Paver Section #1 3,000 sq. ft. Area of Paver Section #2 1,710 sq. ft. Run-on area for Paver Section #2 1,200 sq. ft. Area of Paver Section #3 456 sq. ft. Run-on area for Paver Section #3 100 sq. ft. Area of Paver Section #4 186 sq. ft. Run-on area for Paver Section #4 0 sq. ft. Area of Paver Section #5 168 sq. ft. Run-on area for Paver Section #5 0 sq. ft. Impervious Area Treated by LID Treatment Method #1 (Porous Pavement Pavers) 9,039 sq. ft. Total Impervious Area Treated 9,039 sq. ft. 25% Porous Pavement Requirement New Pavement Area 7022 sq. ft. Required Minimum Area of Porous Pavement 1756 sq. ft. Area of Paver Section #1 2,220 sq. ft. Area of Paver Section #2 1,710 sq. ft. Area of Paver Section #3 456 sq. ft. Area of Paver Section #4 186 sq. ft. Area of Paver Section #5 168 sq. ft. Total Porous Pavement Area 4,739 sq. ft. Actual % of Porous Pavement Provided 67% Final lirainacge peport Maverik PAGE 5 AfWFFL , LLC IV. Drainage Facility Design The existing on -site detention pond will be reused in its existing location. The existing ' detention pond was found to have a capacity of 0.35 acre-feet with a depth of just less than four feet. No existing outlet structure or spillway was found on the existing pond. Pond release is currently controlled by the existing 24" RCP pipe at the low end of the pond with a 100 year release at approximately 21 cfs. The pond drains to the existing swale along the access road just beyond the northwest property line. In -flow to the pond ' comes from two existing 18" RCP pipes that connect to the existing storm sewer system on site. The storm sewer system and inlet pipes will remain. ' Proposed updates to the detention pond include raising the berm around the perimeter of the pond by approximately one foot and increasing side slopes to 3:1 to increase pond ' volume to 0.38 acre-feet and provide a minimum of 1 foot of freeboard. An emergency spillway draining to the adjacent roadside ditch will also be provided. A new outlet structure will also be provided that connects to the existing 24" RCP at the low end of the ' pond. The structure will consist of a modified CDOT Type C inlet with trash rack and orifice plate. The outlet structure will provide water quality and 100-year release of 14.2 cfs based of FAA Method calculations located in Appendix B of this report. A variance has been applied for with the City of Fort Collins to allow an increased release rate to match the maximum pond volume that we can fit on the updated site. Original calculations would have required a 0.7 acre-foot pond with a 6.9 cfs release. The designed pond with a 14.2 cfs release is still significantly less than the existing release at 21 cfs. ' At the time of construction of the pond and outlet structure, the outfall ditch downstream of the pond will be re -graded and all debris removed to provide improved drainage all the Iway to Boxelder Creek. V. Conclusions This study is in compliance with the UDFCD Urban Storm Drainage Criteria Manual and the Fort Collins Amendments to the UDFCD Criteria Manual. This study is also consistent with the overall drainage concept in previously prepared regional drainage study (References 3). The proposed development and proposed drainage facilities will ' result in no adverse impacts created by the quantity or quality of storm water generated by this project. Final nrainage peport Maverik PAGZ 6 AMU, UC VI. References 1. Urban Storm Drainage Criteria Manual; Denver Regional Council of Governments; August 2011. 2. Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual; City of Fort Collins; December 12, 2012 3. Final Boxelder Creek Regional Stormwater Master Plan; Larimer County & Boxelder Creek Regional Alliance; October 2006 4. Floor Insurance Rate Map, Larimer County, Map Number 08069C1003G; Federal Emergency Management Agency; May 2, 2012 final nrainage Veport Maverik PA6� I Appendix A Maps & Figures K.a C211b0kpm Call bn p faa M canon w mfNc COO wmaw uwrn w r.or rn .0 wvotl.0 r. M. 4O WK 110f m� wwww. MlIO �. M aNa w in tlnauvsK M fOlRe[WI9W. 4{1EIrE w [.i+k uu as voi �.auc o, s.R .tlsn n TE RO GE ROAD (PRIVATE �w. wHw ri (PRIVATE ROW VARIES) R�OVd 1. M UN�LIIM'S �N�s�w: m�iun .ro .+ v.rcwaw alum s�owrto ��aMitla Ewcan ro uw.uc ... ,asafwrt. re tlnf. o M rs. a sol»a fwe.m __ pN MMO.Vwn KIM. < N % tl fwKWli�V Y;w M11 N� > �.,�p �NTNYib y� 5y (p iIm 1 t afwf O slrt Z� �1U<-0 so IN oo \ ® Wop y 00 00 00 3 J "mm ♦ \ ♦ - In l In aa In `♦ P�\ jN� L U a ENNROTEST SYSTEMS COP.P ♦ �l-J \ $ j uj d WV, SO 87151- OS- W i \\ K w ? Q Z W M r U Me p ♦ \ e ♦ I lQDATE 6/13/2016 ♦ OTICRBON EWC LLC ♦ 87152-17- W I ♦ ♦ ♦ ' IMP RE VIOtJSN SS `LANOSCAPE/LAMNS 10% 48,874 SE ♦ �' / 9 ♦♦ ' 40# / ROOFS 951[ 40,481 SF w ♦ ' ' ' ♦ ASPHALT/CONCRETE 95% 109.375 SE 4 d+. C85 cH 6G AR BIG LKEI No 1 I 1 III 00 � I I I I I I II II ARLIILAND PROFERI UC 87152-07-WI m rtxT) I uxe . so n IMPIMP RFC LANDSCAPE/LAWNS 10% 37.151 SF PAYERS 50% 4.739 SF ROOFS 95R 34.530 SF ASPHALT/CONCRETE 95% 121.270 SF pnft .M2 a NIn YOZ JIA L." ' o m�aw5 MZ<aw ��<ZIL w JZQM O r Ir 00 in a� O O O w a. ufn5lne ° L r « W im N E me Ycn Lu 11 125 I� n W s 88 W II • fj in Z p a § $ IE,g O$ -_ (% fY� u Y E E u � O y 5 � L p.� 1'�. 9 5 (r °F € c uQ1 J Z V >� g8 �1 i 03 TnY N « oSiEffi� a c LL. IJL ra 0 6 3i ouch° �e9 sE --------/-- _ —-------- - - - E!! v e ® e e v e ® v® V V CN C Y - E f • U ° — _.b R U O IV Z w 3 < m tt) �, c w ��3 3AI80 a. •y JUTLAND rn LANE GOpCHMAN LAND ^_ tGNIj ` A936 Q Q l ND � SbyJ�� `G nitl0 Vl` s p PLEASURE DRIVE I p,H i rNi v 4 n F r v 4928 0 CD f (] T >r ae o d w\ ,\\w a\ 0 9 ai i 0 i� \ a w c6ce 9y 9Z6b zwf�ss�i�, y b86013Ndd SNIOf w N � I~i o S 3 Z U 3 Lo N I w Q w N � & | \ ^`' � __ _ � .tea wMat*,_ [ EU (L ■ � . \ \ ) \D ® f) (» 0 . 0 < /» \j� / 2 Lq }` �k �0 ■ $ , ,# %� � zQ ! G w.a � __ __ s_ m_ __ __ & 2 � � � � 0 Z IW V W J a O O a7 C — m O O CoT N C r O y j coO LP 2 C5 L m O m L (0 l00 L N �7 9 N J C la C U U U it f0 O 7 0 m `� y c - E `" E U) 0 a) vN N E !c N A Y O l0 N N C U la •� U uri W L � y a U 1�0 fop N p N n O E w n m� m nv m m 'D .0 m c� H a m m c N J U) U o 0 E a y y n e L m>( m m d d v a- E W 4) O Q m fOp n m CL m E 0 N 0 N m m O u L C n L d O U) N a s O — m L O. ym C C m V 0 v v U m O N N mu�o`m 0 m =� m S O Q m�aa4 (D ooC 0 o �° 0, 0Oc fcv m daE m �' noyL y3g Za0aui4) m Eo U d° y m L jo a o ca�i rn ayi�'° El' m a°0E E c dyod —Z'on`o tn0acu vD mN �> m 3 tnvm E mo mi a Zw 7 E EQ coy a m— c m 0 T o o c n m rn m E c E L 0 £ T .d. m d m n L m m 'D rn iv `3 m m '0 `o m e i' O _ m O C L C «V: Ny n 2 T u m L m m p d Vi fa ym 0 m E o�TJ m o in acid$ P� ,=m E���c �c yv� am�� S�5 Ot N m m m O— C O O U m ? N m t N f7i 21 10 N �i 0 Bm �� 2 JLO yi-i c �m n�«° a m y' 0) m —Z E 21 —� N m' o'gm m mEmE 3 uSEm$ aE iO�U iCL AV) fon$ oc�v FL-co�E`o m n m > y m m m t m c n a ry m m m 0 m E m o It K a ❑ U U O O Z m M m N y y C 'N 0K cc O //l 'tp Lo c 0 U. c }} u . i N m d n m v n A o 0 m O Q O N C w 0 a p a p 0 m N S C d a 0 a ma ❑ ❑ m U ❑a 00 z C , U ❑ m C)z o aen ma m m c c c Elo N a o 0) G \ N • \ • a .O Vl Q N Lnd 1w O O N N 0 al N �a m Z Hydrologic Soil Group—Ladmer County Area, Colorado Hydrologic Soil Group Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 34 Fort Collins loam, 0 to 1 percent slopes B 10.9 63.6% 73 Nunn Gay loam, 0 to 1 percent slopes C 5.5 32.3% 76 Nunn day loam, wet, 1 to 3 percent slopes C 0.7 4.1 % Totals for Area of Interest 17.1 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long -duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink -swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or VD), the first letter is ' for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. ' LSDA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/16/2015 Page 3 of 4 Hydrologic Soil Group—Larimer County Area, Colorado Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff. None Specified Tie -break Rule: Higher USDA Natural Resources Web Soil Survey 11/16/2015 Conservation Service National Cooperative Soil Survey Page 4 of 4 ' (11) Section 4.0 is amended to read as follows: 4.0 Intensity-Duration-Freauencv Curves for Rational Method: The one -hour rainfall Intensity -Duration -Frequency tables for use the Rational Method of runoff analysis are provided in Table RA-7 and in Table RA-8. ' Table RA-7 -- City of Fort Collins Rainfall Intensity -Duration -Frequency Table for Use with the Rational Method (5 minutes to 30 minutes) Duration (min) 5 2-Year Intensity (ice) 2.85 10-Year Intensity (ice) 4.87 100-Year Intensity (in/hr) 9.95 6 2.67 4.56 9.31 7 2.52 4.31 8.8 8 2.4 4.1 8.38 9 2.3 3.93 8.03 10 2.21 3.78 7.72 11 2.13 3.63 7.42 12 2.05 3.5 7.16 13 1.98 3.39 6.92 14 1.92 3.29 6.71 15 1.87 3.19 6.52 16 1.81 3.08 6.3 17 1.75 2.99 6.1 18 1.7 2.9 5.92 19 1.65 2.82 5.75 20 1.61 2.74 5.6 21 1.56 2.67 5.46 22 1.53 2.61 5.32 23 1.49 2.55 5.2 24 1.46 2.49 5.09 25 1.43 2.44 4.98 26 1.4 2.39 4.87 27 1.37 2.34 4.78 28 1.34 2.29 4.69 29 1.32 2.25 4.6 30 1.3 2.21 4.52 33 Table RA-8 -- City of Fort Collins Rainfall Intensity -Duration -Frequency Table for Use with the Rational Method (31 minutes to 60 minutes) Duration (min) 31 2-Year Intensity (in/hr) 1.27 10-Year Intensity (in/hr) 2.16 100-Year Intensity (in/hr) 4.42 32 1.24 2.12 4.33 33 1.22 2.08 4.24 34 1.19 2.04 4.16 35 1.17 2.0 4.08 36 1.15 1.96 4.01 37 1.16 1.93 3.93 38 1.11 1.89 3.87 39 1.09 1.86 3.8 40 1.07. 1.83 3.74 41 1.05 1.8 3.68 42 1.04 1.77 3.62 43 1.02 1.74 3.56 44 1.01 1.72 3.51 45 0.99 1.69 3.46 46 0.98 1.67 3.41 47 0.96 1.64 3.36 48 0.95 1.62 3.31 49 0.94 1.6 3.27 50 0.92 1.58 3.23 51 0.91 1.56 3.18 52 0.9 1.54 3.14 53 0.89 1.52 3.1 54 0.88 1.5 3.07 55 0.87 1.48 3.03 56 0.86 1.47 2.99 57 0.85 1.45 2.96 58 0.84 1.43 2.92 59 0.83 1.42 2.89 60 0.82 1.4 2.86 34 RAINFALL INTENSITY -DURATION -FREQUENCY CURVE 10.00 9.00 8.00 A "ii�iiiii��a�iiiiiiiiiii■i"■ Figure RA-16 City of Fort Collins Rainfall Intensity -Duration -Frequency Curves (13) Section 5.0 is deleted in its entirety. (14) Section 6.0 is deleted in its entirety. (IS) Section 7.0 is deleted in its entirety. (16) Section 7.1 is deleted in its entirety. (17) Section 7.2 is deleted in its entirety. (18) Section 7.3 is deleted in its entirety. (19) Section 8.0 is deleted in its entirety. (20) Table RA-1 is deleted in its entirety. 36 Table RO-11 Rational Method Runoff Coefficients for Composite Analysis Character of Surface Runoff Coefficient Streets, Parking Lots, Drives: Asphalt 0.95 Concrete 0.95 Gravel 0.5 Roofs 0.95 Recycled Asphalt 0.8 Lawns, Sandy Soil: Flat <2% 0.1 Average 2 to 7% 0.15 Steep >7% 0.2 Lawns, Heavy Soil: Flat <2% 0.2 Average 2 to 7% 0.25 Steep >7% 0.35 (4) A new Section 2.9 is added, to read as follows: 2.9 Composite Runoff Coefficient Drainage sub -basins are frequently composed of land that has multiple surfaces or zoning classifications. In such cases a composite runoff coefficient must be calculated for any given drainage sub -basin. The composite runoff coefficient is obtained using the following formula: n E(Ci *A;) C = '-1 A (RO-8) r Where: C = Composite Runoff Coefficient Ci = Runoff Coefficient for Specific Area (A;) A; = Area of Surface with Runoff Coefficient of C;, acres or feet2 n = Number of different surfaces to be considered A, = Total Area over which C is applicable, acres or feet2 ' (5) Anew Section 2.10 is added, to read as follows: 41 2.10 Runoff Coefficient Adiustment for Infreauent Storms The runoff coefficients provided in tables RO-10 and RO-I I are appropriate for use with the 2-year storm event. For storms with higher intensities, an adjustment of the runoff coefficient is required due to the lessening amount of infiltration, depression retention, evapo-transpiration and other losses that have a proportionally smaller effect on storm runoff. This adjustment is applied to the composite runoff coefficient. These frequency adjustment factors are found in Table RO-12. Table RO-12 Rational Method Runoff Coefficients for Composite Analysis Storm Return Period Frequency Factor ears C 2 to 10 1.00 11 to 25 1.10 26 to 50 1.20 51 to 100 1.25 Note: The product of C times Cf cannot exceed the value of 1, in the cases where it does a value of 1 must be used (6) Section 3.1 is deleted in its entirety. (7) Section 3.2 is deleted in its entirety. (8) Section 3.3 is deleted in its entirety. (9) A new Section 4.3 is added, to read as follows: 4.3 Computer Modeline Practices (a) For circumstances requiring computer modeling, the design storm hydrographs must be determined using the Stormwater Management Model (SWMM). Basin and conveyance element parameters must be computed based on the physical characteristics of the site. (b) Refer to the SWMM Users' Manual for appropriate modeling methodology, practices and development. The Users' Manual can be found on the Environmental, Protection Agency (EPA) website (http://www.er)a.eov/ednnrmri/models/swmm/index.htm). (c) It is the responsibility of the design engineer to verify that all of the models used in the design meet all current City criteria and regulations. 4.3.1 Surface Storaee. Resistance Factors. and Infiltration Table RO-13 provides values for surface storage for pervious and impervious surfaces and the infiltration rates to be used with SWMM. Table RO-13 also lists the appropriate infiltration decay rate, zero detention depth and resistance factors, or Manning's "n" values, for pervious and impervious surfaces to be used for SWMM modeling in the city of Fort Collins. Stormwater ' Alternative ComplianceNariance Application City of Fort Collins Water Utilities Engineering Engineer Name Atwell, LLC Attn: Kevin J. Rohrbough, PE Phone 303-462-1100 Street Address 143 Union Blvd. Ste 700 ' City Lakewood State CO Zip 80228 Owner Name Maverik, Inc. Phone 801-335-3868 ' Street Address 880 West Center St. City North Salt Lake State UT Zip 84054 Project Name Maverik Convenience Store and Fuel Sales Project/Application Number from Development Review (i.e. FDP123456) FDP160024 'Legal description and/or address of property Lot 1 Maverik Subdivision Filing No. 1; NW 1/4 of Sect. 15, T71N, R68W of the 6th PM, Fort Collins, Larimer County, Colorado ' Description of Project Existing restaurant site (with adjacent hotel) where the restaurant is being replaced with a convenience store and fuel sales. ' Existing Use (check one): C; residential !%', non-residential ("e mixed -use ('� vacant ground Proposed Use (check one): ('? residential ir' non-residential C'• mixed -use CA other If non-residential or mixed use, describe in detail convenience store and fuel sales 'State the requirement from which alternative compliance/variance is sought. (Please include applicable Drainage Criteria Manual volume, chapter and section.) Detention pond must release at 2 year historic rate - Fort Collins Amendments 2012 - V2 C10 3.2.3 What hardship prevents this site from meeting the requirement? The detention pond is existing and there is very little room to expand the pond (surrounded by an existing parking lot and roadside ditch that are to remain). ' What alternative is proposed for the site? Attach separate sheet it necessary Under normal conditions, this site would require a 0.7 acre-foot pond with a 6.9 cfs 100-year release rate. What is proposed is to reduce the pond volume required to store the 100-year runoff to 0.38 acre-feet by increasing the allowable 100-year release rate to 14.2 cfs (wich is still less than the existing 100-year release rate approximated at 21 cfs controlled by an open ended pipe). Attach separate sheet if necessary page 1117 C. o_1_n_,fln,uO,ffoM. 04 ge .Ihe,existi4q.-PonO',which ,wis,f6und.'to"hav'o.n6,outlot<tfrUdtd"- re, jpi,.wcjy,,Qr pip end ttbAtrrfeht§.such a'p'-,fl d 6-d Ooh-&-and'n- AtIM two _existing 6 will be; ...�rp 9 se prclp .,,e,. !91. t6_11 significantly improved; in one. h. �, Mevegetate,all'dlsturbed"areas. page The owner agrees to comply with the provisions of the zoning ordinance, building code and all other applicable sections of the City Code, Land Use Code, City Plan and all other laws and ordinances affecting the construction and occupancy of the proposed building that are not directly approved by this variance. The owner understands that if this variance is approved, the structure and its occupants may be more susceptible to flood or runoff damage as well as other adverse drainage issues. Signature of The engineer hereby certifies that descriptions is correct. Signature of n above information, along with the reference plans and project 1nsnot7 48992 i- IT 1 PE STAMP I r Date complete application submitted: �Z� ZD%l Date ofapprovaUdenial: 3 3 oZ t % Variance: 0 approved ❑ denied Staffjustification/notes/condiitions: u t /Te . ,7� �n Q �O' J • /S no7 V f.7/� T �1n�iW r1 �r —7b o / l ka , 1 j U C'�9 1,e(/4-1[ rayC 4 *"IeC 4 of -P r v ' 1 aTtl' CAJrpv, • Approved by: Entered in UtilityFile Databa yes []no Appendix B Stormwater Calculations Y C1 Oi L R)C �NCR 666 R - 0) x w w atS o6 oC 666 R I c ILY �L m Q Q C� 6 0 U, I O O O 0 C 00) O Q a of o c`r'n r' V a W m Nl rn � V C o 0 0 O O N o O N -a N N 7 7 C c0 J J C W w QC7p ¢a m In O O CO1D N c o 0 co OR f0 O 0 00 M V 0 0 0 0 0 O O O 06 O O W m 0 0 0 rn uo Ln r O O O 0 00 W 0 0 0 0 O O O O O O OD o 0 C7 O O M o v 0 0 a� coC) N N N_ N_ Cl) rn O a0 n CO O O O 00 0 O V O o 0 O O O O O O Cn Ln o N O O ro m rn N O O 0 00 � O O O C OD r r t- A 0) O 0 o c N 0 0 cq r r O O O 0 00 (O O o c c O O O C O OD N O O 07 O O m o li G C Q �! Q m U r O Z o NO N LL to Q iu H aI Z o 0 w ,c w0?�U QU LL Z 0 m ~ Z O 0 5 1 � 0 m � U N Y Q w W U Z F C E W O a a a O N LL Yi IN (d OC 0 O i j E a o o v o 0 n HU N C X W r J m = 2 m U H O N M N T N N ,y ~ w � J IL g U r �'? W ao " O < It ao U F- ui fu 6 vi ~ E N N tG <V t+i w F J w y r r o o r CR � o 0 J > O O O O O W t W a O IV fV O O N tV Q z N N O O ^ O O O W J C �" E u i G> a A OO UU N v VU a 7 O7 ui vi ui z z 5 W Irua w H J N O O O O O 7 O G ow N N Q ci N t7 v O ~ f Q Z = W J cq co n CR Q U O O O O O O O O O H Q � a Q m a o N m m o Q Q Cl C O fV C C G O m m 7 N d Q cy ¢ co U w N_ 2 Q V Q m U 0 = z = = Y 0 m N ZUC W oa° 'nZ w o z W aul H S W U,p 00 w H 1 LL N o p � FIX-, � z �0z 0 C2 ca 1�IIIIIi�il� ZUK 00� N �aZ N 2 W (7 ' a, N 7 M 00 y 1 ouw .NO O LU S 2 W ZZQ 7y F � 2 NCO O ,II�II�III�I� Project Name: Maverik Title: Existing Pond By: GDB Tributary Area (ac.): 4.35 Volume Equation: Modified FAA Required Volume: WQCV = See Below Minor Required Volume = 0.02 ac-ft 784 cubic feet 100 Year Required Volume = 0.38 ac-ft 16,553 cubic feet Job No. 15001770 Date: Apr-16 Revised Drainage Basin: Basin A V = Volume in cubic feet (cu-ft) h = Contour Interval in feet (ft.) A1,A2 = Area enclosed by successive Contours in square feet (sq-ft) Allowable Release Rate: 010OR = 6.9 cfs Contour Elev. ft. Area sf A1+A2 sf (A1xA2)A1/2 s (A1+A2)+ (At+A2)A1l2 sf In (ft) h/3 (ft) Volume (Cu-ff) Accumul. Volume (cu-ft) Accumul. Volume (ac-ft 4927.5 5 5 0.00 600 55 655 0.50 0.17 109 4928 595 114 0.00 4448 1514 5962 0.50 0.17 994 4928.5 3853 1 1 1 1108 0.03 8750 4344 13094 0-50 0.17 2182 4929 4897 3290 0.08 10356 5170 15526 0.50 0.17 2588 4929.5 5459 5878 0.13 11474 5730 17204 0.50 0.17 2867 4930 6015 8745 020 12544 6267 18811 0 50 0.17 3135 4930.5 6529 11880 0.27 13601 6795 20396 0.50 0.17 3399 4931 7072 15280 0.35 Minor Water Surface Elevation = 4928.34 depth = 0.84 100 Year Water Surface Elevation Incl WQCV = 4931.19 depth = 3.69 100 Year Freeboard Elevation = 4932.19 Project Name: Maverik Title: Updated Pond By: GDB Tributary Area (ac.): 4.35 Volume Equation: Modified FAA Required Volume: Minor Required Volume = 100 Year Required Volume = 0.07 ac-ft 3,049 cubic feet 0.38 ac-ft 16,553 cubic feet Job No. 15001770 Date: Apr-16 Drainage Basin: Basin A V = Volume in cubic feet (cu-ft) In = Contour Interval in feet (ft.) A1,A2 = Area enclosed by successive Contours in square feet (sq-ft) Allowable Release Rate: Q10OR = 14.2 cfs Minor Water Surface Elevation b W V 4 1� _tltl YyW Y 0000 0000 °0000 0000 °00 00 0000� 2��• Y e'tl al 83_e <' 05 e$ e a8 9V 'E fi S CF �og LL d 9S el e _a�sso"ss � W W ns za3��E2g F�0 e R' n o ',Y Ay E 5 pY p = > > E o E V • � 3 O a ------eeeeeOepaag ;laaa �veo ee e�<o I I_ 110 0�¢ a a; a i d a � " c 3 8 • n 3y�s a 0 E sssssssss s sa o"araaa"aa'"aa' a000�o o 66eooe „ ei0 000006. Rsssssss...sosaio o6600e0000ece of 6'a 0000 ooaa"aaaaaassssd 6euedueueee eo0 E ssssss��s8 ss"ss' sags' o sas�ee�p ooaaaalaaassss o oo e,ol66io _0000 dgae d,alc ee a000aeap 8ia g<�� gggg 8881'''eA., as a3a88 S�2j '.o ool'88818So8$$8 a o ao 00000a o o of oo, O mRm .-Qj rvn� �a S� ^�iORnn,Xu RRI iR N '--- - 8 �RSS88R888'RR:St8R888�RR:R8R388-RS,9A8�8RS�F�.. mam^ «R6o )a 7/ 04 > (71 3 0 k) !Zz<ƒa &m & e 7 ) E 0 \ \j k $ > 3 % 0t .k> k ' u �!LUm _ E j )� #kak2/2\| k2( ) )/ ) m ¥t {?3 $ ) E! aly f 0 �!)))! \z {(/ !� m §d)!E ' .a)%))!k ofca '� fps;!Ga ®E»> UJW / a!% �)$! B02k9.0 °© }� -- C6 /a=�o J)-- �G\f�)) 7! �22 §T :EWW 2 . J | 0 - . ! v STAGE -DISCHARGE SIZING OF THE WEIRS AND ORIFICES (INLET CONTROL) Project: Maverik Basin ID: Detention Pond Noul,nf (l,Jcr I ISvn,luJl 11wu4 (Mr : .J Mnu .nr lithe. I V V. Current Routing Order is 07 Desion klformellon flnoutl: Circular Opening: Diameter in Inches OR Rectangdar Opening'. Width in Feet Length (Height for Vertical) Percentage of Open Area After Trash Rack Reduction Orifice Coefficient Wee Coefficient Orifice Elevation (Bottom for Vertical) i #1 Honz. #2 Hortz. #1 Van #2 Vert. Dia. = Inc 111 S WzI 2.92 1 1 62 It L or H =1 2.92 1 1 1.13 h. % open = C, _ C. _ 50 1 100 0.65 1 0.65 3,00 1_ 4930.00 1 4,928.20 Calculation of Collection Canacitc Net Opening Area (after Trash Rack Relluceon) 0, = 426 1 83 s, t. OPTIONAL: User-Overide Net Opening Area k = Penrneler as Weir Length L. = 876 h OPTIONAL. User-Ovende Weir Length L. = it Top Elevation of Vertical Orifice Opening. Top = 4929.33 h Center Elevation of Vertical Orifice Opening, Can = 4928.77 it. Routing 3: Single Stage - Water flows through WQCV plate and #1 horizontal opening into #1 vertical opening. This flow will be applied to culvert sheet (#2 vertical 3 horizontal openings Is not used). Horizontal orifices Ivenical Orifices LaoMs fO WQCV. 101p a Map srxage w S Parest,,re ul, Water Surface Elevation It n= WQCV Plate/Riser Flow cis #1 Honz. #1 Hon¢. Wow Od9L'e Flow Flow cfa de n 92 Hartz. #2 Horiz. Wilk Qfir= Flaw Flow ofa tits o #1 Vert. Collection Capacity cfs #2 Vert col ion Capacity cfs Total Collection Capacity cis Tai,et volurws fM WQCV M. It Mop slaage Vol.r 4928.00 4928.50 0.00 0.00 0.00 0.00 0.00 0.00 coo 0.00 1000.02 0.02 0.00 0.00 0.00 0.00 0.98 4929.00 0.06 0.00 0.00 0.00 0.00 427 0.00 0.06 4929.50 0.11 0.00 0.00 0.00 0.W 8.16 _ 0.00 0.11 _ 4930.00 0.17 0.00 0.00 0.00 0.W 10.61 0.00 0.17 _ 4930.50 0.21 9.29 15.72 0.00 0.00 12.57 0.00 9.51 4930.98 0.24 25.50 22.01 0.00 0.00 1421 0.00 14.21 4931.48 0.25 47.32 27.06 0.00 MIX 15.73 0.00 15.73 4931.98 0,26 73.22 31,29 1 0.00 0.00 17,12 0.00 1712 #WA NN/A #N/A M4/A I#WA 0.00 #NIA l#WA MA #N/A #WA #N/A 0.00 #N/A MA III IrWA NNIA #WA 0.00 #N/A #WA #N/A #N/A #WA MA 0.00 #NIA #WA MA #WA XWA #WA 0.00 #NIA MA I#WA #WA #NIA #WA 0.00 #N/A #WA #WA #WA VWA #WA ow #N/A #NIA #WA #NIA #NIA #N/A ow #N/A #N!A #NIA #NIA JIWA #N/A ow #N/A #WA #WA #NIA #N/A #NIA ow #NIA #N/A #N/A /A #NiA #N/A 0.W #NIA #N/A *N/A 41 OWA III O.W #NIA #WA _ #WA #N/A 1#WA #N/A #WA_ #WA 0.00 #NIA OVA #WA #NIA _ 0.00 #N/A #WA #N!A a" #NIA #N/A 0.00 #NIA #NIA #N/A fill #N/A #WA 0.00 #NIA _ MINA #NIA ONIA #NIA It 0.00 #NIA It #N/A #WA #WA #N/A 0.00 #NIA #WA #NIA MA #WA MA 0.00 #NIA #N/A #N/A IYWA #NIA #WA 0.00 #NIA ill #NIA A ili #NIA 0.00 #NIA MA irWA MA NWA #NIA 0.00 #NIA #WA #WA W" #WA #N/A 0.00 #N/A #N!A #NIA #UA #WA #NIA 0.00 #N/A #WA #N/A #WA *WA 111 0.00 ski IIWA III #NIA III #NIA 0.00 #N/A #N/A IIN/A #N/A #N/A #NIA 0.00 111 #WA I11WA #N/A #WA 111 0.00 #NIA MA #WA #WA #WA #N/A 0.00 #NIA _ #WA #NIA #NIA SWA #N/A 0.00 #NIA - #WA OWA #N/A #WA #N/A 0.00 011/A /#WA #WA #WA itNlA 0.00 I#WA MA #WA *NA #NIA #WA #WA 0.00 #IIIA #WA #WA #N/A #N/A #N/A 0.00 #IIIA #WA #NIA I NNIA I SNIA #N!A #WA 15001770 UDFCD Outet StructureAs, Outlet 9/3012016. 9.22 AM STAGE -DISCHARGE SIZING OF THE SPILLWAY Project: Maverik Basin ID: Detention Pond Design Information (input: Bottom Length of Weir Angle of Side Slope Weir Elev. for Weir Crest Coef. for Rectangular Weir Coef. for Trapezoidal Weir Calculation of Spillway Capacity (output): L =M268 feet Angle =degrees EL. Crest =feet Cw = C, = Water Surface Elevation ft Rect. Weir Flowrale cfs (output) Triangle Weir Flowrate cfs (output) Total Spillway Release cfs (output) Total Pond Release cfs W t) 4928.00 0.00 0.00 0.00 0.00 4928.50 0.00 0.00 0.00 0.00 4929.00 0.00 0.00 0.00 0.00 4929.50 0.00 0.00 0.00 0.00 4930.00 0.00 0.00 0.00 0.00 4930.50 0.00 0.00 0.00 0.00 4930.98 0.00 0.00 0.00 0.00 4931.48 28.43 1.89 30.32 30.32 4931.98 80.40 10.72 91.12 91.12 #N/A #N/A #N/A MA #N/A #N/A #N/A #N/A MIA #N/A #N/A #WA #N/A #N/A #N/A #N/A #WA #N/A #N/A #N/A #N/A #WA #N/A #N/A MIA #N/A #WA #N/A #N/A #N/A #N/A #WA #N/A #4/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #WA #N/A #N/A #N/A #NIA #WA #N/A #N/A #N/A #NIA #WA #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A MIA #N/A #NIA #N/A #N/A *NIA #N/A #N/A #NIA #N/A #N/A #N/A #N/A #N/A #N/A MIA #N/A #N/A MIA #N/A #N/A #N/A #N/A #WA #WA #WA #N/A MIA #N/A #N/A #N/A #N/A #NIA #N/A #N/A #N/A #N/A #NIA #N/A #N/A #N/A #N/A #NIA #N/A #N/A #N/A #NIA #N/A #N/A #N/A #NIA #N/A #N/A #N/A #N/A #N/A #N/A #NIA #N/A MA #N/A MIA #N/A #N/A #N/A #N/A #N/A #N/A #N/A MIA #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #WA #N/A #N/A MIA #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 15001770 UDFCD Outlet Structure.)ds, Spillway 4/21/2016, 12:35 PM Stormwater Detention and Infiltration Design Data Sheet Stormwater Facility Name: Maverik Detention Pond Facility Location & Jurisdiction: Fort Collins, CO User Input: Watershed Characteristics Watershed Slope = 0.020 ft/ft Watershed Length = 500 ft Watershed Area = 4.35 acres Watershed Imperviousness = 81.1% percent Percentage Hydrologic Soil Group A = percent Percentage Hydrologic Soil Group B = 100.0% percent Percentage Hydrologic Soil Groups C/D =1 percent Location for 1-hr Rainfall Depths (use dropdown) User Input W WQCV Treatment Method = extended Detenhoo After completing and printing this worksheet to a pdf, go to: ' httos://maoerture.dieitaldataservic.,. 4Rvh/?viewer=cswdif create a new stormwater facility, and attach the pdf of this worksheet to that record. ' Routed H dro raoh Results Design Storm Return Period = One -Hour Rainfall Depth = Calculated Runoff Volume = OPTIONAL Override Runoff Volume = Inflow Hydrograph Volume = ' Time to Drain 1711 of Inflow Volume - Time to Drain 99%of Inflow Volume - Maximum Ponding Depth = Maximum Ponded Area = Maximum Volume Stored = rr� rr r r. •r � � rr WQCV 2 Year 5 Year 10 Year 50 Year 100 Year 0.53 0.98 1.36 1.71 2.31 3.67 0.122 0.280 0.411 0.535 0. 781 1.275 0.121 0.279 0.410 0.535 0.781 1.275 30.7 37.8 35.8 34.1 31.2 26.7 33.6 42.2 40.9 1 40.0 1 38.4 1 35.8 1.28 2.07 2.27 2.44 2.79 3.68 0.15 0.17 0.17 0.18 0.18 0.21 0A10 0.233 0.265 0.296 0.358 0.531 in acre-ft acre-ft acre-ft hours hours ft acres acre-ft 15001770-SDI_Design_Data_v1.07.xlsm, Design Data 1/20/2017, 4:10 PM I IFStormwater Detention and Infiltration Design Data Sheet �— 35 100VR OUT ' 30 25 20 3 ' o LL 1s 10 ' s ' 0 0.1 4 3.5 ' 3 ' C 2.5 W 0 % 2 z Z 6 ' 1.5 I 1 0.5 ' 0 0.1 1 15001770-SDI_Design_Data_v1.07.xism, Design Data TIME [hr] 10 1 10 100 DRAIN TIME [hr] 1/20/2017, 4:10 PM Streets, Inlets, & Storm Drains Chapter 7 Denver No. 16 Combination Inlet Interception Capacity based on depth of ponding (depth measured outside local depression) 5 • a • Pending Depttn = 4 a Pmmng Deptr . 6 y :. 0. 15Q,; ' to Pmding Depth • 9' Pmd,ng Dear . 12. ■ , Pmd,ng Depth. 18' ya -0150,exI + - J c ' c 3 ♦ ■ 0 Eyb - 0.15Qs 139 i Via 0.12Q;s ° s' 2 v ■ 1 • 1 30 sump Inlet cap•elly' (efs) This value assumes inlet clogging per Section 3.2.9. Figure 7-8. Denver no. 16 interception capacity in sump 10D 2 too 3.2.7 Other Inlets in a Sump (Not Modeled in the UDFCD-CSU Study) The hydraulic capacity of grate, curb -opening, and slotted inlets operating as weirs is expressed as: Q, = C. L d l ` Equation 7-37 Where: (3x�xl.5js= yly� • Q, = inlet capacity (cfs) C = weir discharge coefficient Ruuv�e Lw = weir length (ft) d = flow depth (ft). Values for C. and L. are presented in Table 7-8 for various inlet types. Note that the expressions given for curb -opening inlets without depression should be used for depressed curb -opening inlets if L > 12 feet. 7-24 Urban Drainage and Flood Control District January 2016 Urban Storm Drainage Criteria Manual Volume I ' Chapter 7 Streets. Inlets. & Storm Drains The hydraulic capacity of grate, club -opening, and slotted inlets operating as orifices is expressed as ' Q, = C.A. (2gd )° S Equation 7-38 Where: % 1 / OS - r Q, = inlet capacity (cfs) CO = orifice discharge coefficient A.= orifice area (ft) f(voe ! \ \CDs L d = characteristic depth (ft) as defined in Table 7-8 g = 32.2 ftvsec'. Values for C and A„ are presented in Table 7-8 for different types of inlets. Combination inlets are commonly used in sumps. The hydraulic capacity of combination inlets in sumps depends on the type of flog and the relati\e lengths of the curb opening and grate For %\eir flo%\, the capaciq of a combination inlet (grate length equal to the curb opening length) is equal to the capacity of the grate portion only. This is because the curb opening does not add any effecti%e length to the -weir. If the curb opening is longer than the grate, the capacity of the additional curb length should be added to the grate capacity. For orifice floc, the capacity of the curb opening should be added to the capacity of the eratc. January 2016 Urban Drainage and Flood Control District 7-25 ' Urban Storm Drainage Criteria Manual Volume 1 Streets, Inlets, & Storm Drains Chapter 7 Table 7-8. Sump inlet discharge variables and coefficients (Modified From Akan and Houghtalen 2002) Inlet Type C„. L„.' Weir Equation Definitions of Terms Valid For Grate Inlet 3.00 L + 2 W d < 1.79(A�/L„) L = Length of grate (ft) W= Width of grate (ft) d = Depth of water over grate 00 Ao = Clear opening area'' (ft) Curb -opening 3.00 L d < h L = Length of curb opening (ft) Inlet h = Height of curb opening (ft) d = d; — (h/2) (ft) d; = Depth of water at curb opening (ft Depressed Curb 2.30 L + 1.8W d < (h + a) W= Lateral width of depression Opening Inlet' (ft) a = Depth of curb depression (ft) Slotted Inlets 2.48 L d < 0.2 ft L = Length of slot (ft) d = Depth at curb ft length The weir should be reduced where clogging is expected. '- Ratio of clear opening area to total area is 0.8 for P-1-7/8-4 and reticuline grates, 0.9 for P-1- 7/8 and 0.6 for P-1-1/8 grates. Curved vane and tilt bar grates are not recommended at sump locations unless in combination with curb openings. ' If L > 12 ft, use the expressions for curb -opening inlets without depression. C. Ao Orifice Equation Definition of Terms Valid for Grate Inlet 0.67 Clear d > 1.79(A, /L„) d = Depth of water over grate (ft) opening area' Curb -opening 0.67 (h)(L) d; > 1.4h d = d; — (h12) (ft) Inlet (depressed d; = Depth of water at curb orundepressed, opening (ft) horizontal orifice h = Height of curb opening (ft) throatb Slotted Inlet 0.80 (LAW) d> 0.40 ft L = Length of slot (ft) W= Width of slot (ft) d = Depth of water over slot (ft) The orifice area should be reduced where clogging is expected. ` The ratio of clear opening area to total area is 0.8 for P-1-7/84 and reticuline grates, 0.9 for P- 1-7/8 and 0.6 for P-1-1/8 grates. Curved vane and tilt bar grates are not recommended at sump locations unless in combination with curb openings. 6 See Figure 7-12 for other types of throats. 7-26 Urban Drainage and Flood Control District January 2016 Urban Storm Drainage Criteria Manual Volume I 1 Standard Operating Procedures (SOP) for ' Fuel Spill Containment System Background 1 A Fuel Spill Containment System (FSCS) is a system of drains with a holding tank to capture and detain fuel spills from underground fuel storage tanks and fuel pumps. An FSCS is sometimes a requirement of the jurisdiction for which fuel pumps and storage tanks are installed. ' An FSCS consists of trench drains with grates installed at the surface surrounding underground fuel storage tanks and fuel pumps. These trench drains are to collect any fuel spillage that may occur. The trench drains connect to a Fuel Spill Containment Vault designed to contain a minimum of 150 gallons of spilled fuel. The Vault is also designed to allow any normal drainage flows to flow through to the outfall ' of the system. Fuel detained within the Vault should be promptly removed through an access hatch installed at the top of the Vault. The Vault is typically connected to the upstream trench drains and downstream outfall with schedule 40 PVC pipe with a diameter of no less than six inches. ' The entire system is gravity fed and care should be taken to ensure positive drainage throughout the system to the ultimate outfall. ' Normal Function of Fuel Spill Containment System ' Whether there is a fuel spill or not, the trench drains will capture any upstream runoff that normally occurs. The valve just downstream of the Fuel Spill Containment Vault should be left open under normal conditions to allow runoff to pass through to the downstream storrnwater system. This runoff will flow ' through the system whether there is a fuel spill contained in the Vault or not, and be released at the outfall. ' Actions to be Taken After a Fuel Spill Incident In the event of a fuel spill, the following shall be the basic course of action: • Shut down equipment • Evacuate the area ' • Block access to the area • Close valve just downstream of Fuel Spill Containment Vault ' • Contact designated emergency personnel • Determine the source of the spill • Stop the spill at the source ' March 2017 1 of 3 • Apply absorbent to soak up spilled fuel ' • Use neutralizing agents to reduce the chance of fuel ignition • Sweep up absorbent and neutralizing agents and dispose of properly • Safely remove and properly dispose of spilled fuel detained within the Fuel Spill Containment ' Vault to prevent discharge to either storm or sanitary sewer • Use absorbent pads to soak up any remaining fuel and chemicals • Dispose of used absorbent pads in designated barrels • Completely clean containment system and collect the wash water and dispose properly • Check the outfall for spill that may have escaped the Fuel Spill Containment Vault and clean up area if necessary • Once the fuel spill is cleaned up completely open the valve just downstream of Fuel Spill ' Containment Vault to allow runoff to flow through normally The action procedure presented above is meant to be a guideline for what to do to clean up a fuel spill that has been contained within a FSCS. It is the responsibility of the owner/operator to have a detailed hazardous material spill procedure and all materials and equipment on hand to implement it. Other ' procedures and actions may be required by local, state, and federal regulations such as reporting and investigating the incident. All required procedures should be followed in an incident where fuel is spilled. 1 1 1 March 2017 2of3 Routine Inspection and Maintenance Table Required Maintenance Objective Frequency of Action Action Inspect the trench drain through the grates and from each end. Look for obstructions, vegetation, debris, litter, sediment, etc. inside the trench drain. Vegetation or algae Routine —Including just before annual storm seasons (that is, April Trench Drain growing in the trench drain indicate the and May), end of storm season presence of standing water. Water backing Inspection up out of the trench drain entrance indicates after leaves have fallen, and a blockage. During a rainstorm, a blockage following significant rainfall will be indicated by slow water flow or by events. water backing up at the trench drain entrance. Clear as much of the trench drain as possible from each end with a long -handled tool such Routine —Including just before Trench Drain annual storm seasons (that is, April Sediment, as a hoe. Raise the grates to clean and May), end of storm season inaccessible portions of the trench drain. Debris and after leaves have fallen, and Scrape with hoe or similar tool to ensure that Litter removal water flows freely along the concrete flow following significant rainfall line of the trench drain. events. Inspect vault to insure that the vault Routine —Annual inspection of Fuel Spill continues to function as initially intended. hydraulic and structural facilities. Containment Examine the outlet for clogging, excessive Also check for obvious problems Vault sedimentation levels, oily sheen, and damage during routine maintenance visits, Inspection to any structural element. especially for plugging of outlets. Fuel Spill Routine —Annually including just Containment Vacuum and remove accumulated sediment before annual storm seasons (that Vault Sediment, and liquids from the bottom of the vault is, April and May), end of storm Oily Sheen, through the access hatch on the top of the season after leaves have fallen, _ Debris, and vault. Ensure outlet is clear of debris. and following significant rainfall Litter removal events and when oily sheen is seen during any routing inspection. 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