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HomeMy WebLinkAbout2012-08-03 Revised Stormwater Narrative McDonald's USA, LLC MCDONALD'S Oak Park Heights, Minnesota STORMWATER NARRATIVE 20 May 2009 Revised 3 August 2012 • • • • L A N D F O R M From Sue to Finish • • RECEIVED AUG 15 2012 EXISTING SITE CONDTIONS The site comprises 1.18 acres located at 14545 60 Street North in Oak Park Heights, Minnesota. The site is currently a McDonald's Restaurant with associated parking. The topography of the site is primarily flat impervious surface with approximately 13% existing pervious area. Contour elevations range from 925 along the south end of the property to 905 along 60 Street North. There is a steep slope at the along the south end of that site that drains onto McDonald's property and a retaining wall along the southwest edge of the site. Currently there is one restaurant building on site with associated parking for customers and a storage garage located along the west property line of the site. PROPOSED SITE The proposed development consists of the demolition of the existing restaurant, storage garage, site features, and parking lot to accommodate the redevelopment of a new McDonald's Restaurant and associated parking. The proposed improvements will increase the site's pervious area to approximately 23.8 %. JURISDICTIONAL BODIES AND REQUIREMENTS The City of Oak Park Heights and Middle St. Croix Watershed Management Organization (MSCWMO) have review jurisdiction over storm water runoff from the proposed redevelopment at this site. MSCWMO requires infiltration of 1/2 inch of run -off over the impervious area plus 1/4 inch of runoff for area with compacted soils for redevelopment sites and also requires that the proposed runoff rates for the 2 -year, 10 -year, and 100 -year critical storm frequency events not exceed existing runoff rates. The infiltration BMP shall also be capable of infiltrating the required volume within 48 hours for subsurface BMPs. EXISTING SITE DRAINAGE PATTERNS Currently there is no storm sewer on site and the site sheet drains from south to north and drains out into 60 Street North were it is collected by the 60 Street storm sewer system. Analysis of the site was performed with HydroCAD® models to calculate the existing runoff (see attachments). PROPOSED ON -SITE STORM WATER MANAGEMENT The design goal of the proposed drainage plan is to replicate the existing drainage patterns as closely as possible while capturing runoff and routing it through a storm sewer system, provide infiltration for 1/2 inch of rainfall over the impervious surfaces plus 1/4 inch of rainfall over the compacted pervious area of the redevelopment and provide rate control to limit the rate of runoff to the current conditions. MCD09065 — McDonald's L A N D F OR M 8/3/12 Stormwater Narrative 2 To meet the 1/2 inch plus 1/4 inch infiltration requirement we propose to construct a 1,756 C.F. infiltration facility located within the site. The infiltration facility is designed using 15" perforated HDPE pipes incased within a 6 foot wide by 2 foot deep trench with 1 inch washed rock wrapped in a filter fabric. Infiltration Volume Calculations Proposed impervious surface = 39,005 s.f. Required Infiltration Volume = (0.5 "/12 ") x 39,005 s.f. = 1,626 c.f. Proposed compacted pervious surface = proposed pervious — existing pervious = 12,184 s.f. — 6,673 s.f. = 5,511 s.f. Required Infiltration Volume = (.25 "/12 ") x 5,511 s.f. = 115 c.f. Total Infiltration Volume Required = 1,626 c.f. + 115 c.f. = 1,741 c.f. Storage provided in 15" diameter pipe = 0.625 x n = 2.48 c.f./I.f. Storage provided in rock bed less pipe volume = (6 x 2) — 2.48 = 9.52 x 0.30 (30% voids) = 2.85 c.f./I.f. Total storage per linear foot of infiltration = 2.48 + 2.85 = 5.33 c.f. Total infiltration bed length = 431 I.f. Total available infiltration volume = 431 I.f. x 5.33 c.f./1.f. = 2,297 c.f. which exceeds the required 1,741 c.f. Prior to entering the infiltration facility, stormwater from the proposed site drains into sump catch basins for pre- treatment. The sump catch basins are designed to capture large particles prior to entering the infiltration system to help reduce maintenance on the facility. A 15" RCP pipe provides an outlet to a proposed catch basin located in 60 Street North. The outlet elevation is set at the top of the infiltration system's storage volume. Based on a geotechnical report prepared by Braun Intertec dated May 13, 2009. The on -site soils fall into the A and B hydrologic Soils Groups. With these types of soils estimated infiltration rates should range from 0.6 to 0.8 inches per hour (refer to geotechnical report for more information). The underground infiltration area will drain down in 40 hours with an infiltration rate of 0.6 inches per hour and will thus meet the 48 hour requirement. MCD09065 — McDonald's L A N D F O R M 8/3/12 Stormwater Narrative 3 Rate Control Rate control requirements are met by increasing the pervious surface on site from 13% to 23.8 %. Storm water runoff analysis for the entire site was performed with HydroCAD® models (see attachments). Table 1 compares the existing and proposed runoff rates for the MSCWMO's critical storms. Table 1: Runoff Rates _ �s rl - iiu wn�ui F �: °�a 4.05 3.48 10 -year (4.15 ") 6.54 5.99 100 -year (5.90 ") 9.62 9.12 CONCLUSION Through the use of an underground infiltration facility, the proposed plan meets the rate control and infiltration requirements of the City of Oak Park Heights, and MSCWMO. CONTACT INFORMATION This document was prepared by: Landform 105 South Fifth Avenue Suite 513 Minneapolis, MN 55401 Please direct any questions regarding the design infiltration storm sewer system to Eric Kellogg at ekellogg(landform.net or 612.638.0242. MCD09065 — McDonald's L A N D F OR M 8/3/12 Stormwater Narrative 4 1 S E 2S / , Existing Proposed , S ubca t � Reach on \ Link Drainage Diagram for MCD09065 Oak Park Heights Prepared by Landform, Printed 8/2/2012 --\-- HydroCAD® 9.10 s/n 01542 © 2009 HydroCAD Software Solutions LLC MCD09065 Oak Park Heights Type 1124 -hr 2 -yr Rainfall= 2. 75" Prepared by Landform Printed 8/2/2012 HydroCAD® 9.10 s/n 01542 © 2009 HydroCAD Software Solutions LLC Page 2 Time span =5.00 -20.00 hrs, dt =0.05 hrs, 301 points Runoff by SCS TR -20 method, UH =SCS Reach routing by Stor- Ind +Trans method - Pond routing by Stor -Ind method Subcatchment 1S: Existing Runoff Area = 51,189 sf 86.96% Impervious Runoff Depth >1.89" Tc =5.0 min CN =93 Runoff =4.05 cfs 0.185 af Subcatchment 2S: Proposed Runoff Area = 51,189 sf 76.20% Impervious Runoff Depth >1.56" Tc =5.0 min CN =89 Runoff =3.48 cfs 0.152 af Total Runoff Area = 2.350 ac Runoff Volume = 0.337 of Average Runoff Depth = 1.72" 18.42% Pervious = 0.433 ac 81.58% Impervious = 1.917 ac MCD09065 Oak Park Heights Type 1124 -hr 2 -yr Rainfall = 2. 75" Prepared by Landform Printed 8/2/2012 HydroCAD® 9.10 s/n 01542 © 2009 HydroCAD Software Solutions LLC Page 3 Summary for Subcatchment 1 S: Existing [49] Hint: Tc <2dt may require smaller dt Runoff = 4.05 cfs @ 11.95 hrs, Volume= 0.185 af, Depth> 1.89" Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs Type II 24 -hr 2 -yr Rainfall= 2.75" Area (sf) CN Description 6,673 61 >75% Grass cover, Good, HSG B 44,516 98 Paved parking & roofs 51,189 93 Weighted Average 6,673 13.04% Pervious Area 44,516 86.96% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 1S: Existing Hydrograph ❑ Runoff 4.05 ds 4 Type II 24-h r 2 -yr Rainfall= 2.75" Runoff Area= 51,189 sf 3 Runoff Volume =0.185 af Runoff Depth >1.89" LT_ 2- Tc =5.0 min CN =93 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) MCD09065 Oak Park Heights Type 1124 -hr 2 -yr Rainfall = 2.75" Prepared by Landform Printed 8/2/2012 HydroCAD® 9.10 s/n 01542 © 2009 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment 2S: Proposed [49] Hint: Tc <2dt may require smaller dt Runoff = 3.48 cfs @ 11.96 hrs, Volume= 0.152 af, Depth> 1.56" Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs Type II 24 -hr 2 -yr Rainfall=2.75" Area (sf) CN Description 12,184 61 >75% Grass cover, Good, HSG B 39,005 98 Paved parking & roofs 51,189 89 Weighted Average 12,184 23.80% Pervious Area 39,005 76.20% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 2S: Proposed Hydrograph / ❑ Runoff 3.48 cfs 0 Type II 24-hr 2 -yr 3— j R Runoff Area = 51,189 sf Runoff Volume =0.152 of 2- Runoff Depth >1.56" ° Tc =5.0 min LL AP CN =89 1 ii PI <� for /!!! /! -eirof ��� 4 � ��f�4 o < 1 9 . !!/ ® /!!!!!!!/!!!!!/S/ 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) MCD09065 Oak Park Heights Type 1124 -hr 10 -yr Rainfall= 4.15" Prepared by Landform Printed 8/2/2012 HydroCAD® 9.10 s/n 01542 © 2009 HydroCAD Software Solutions LLC Page 5 Time span =5.00 -20.00 hrs, dt =0.05 hrs, 301 points Runoff by SCS TR -20 method, UH =SCS Reach routing by Stor Ind +Trans method - Pond routing by Stor -Ind method Subcatchment 1S: Existing Runoff Area = 51,189 sf 86.96% Impervious Runoff Depth >3.16" Tc =5.0 min CN =93 Runoff =6.54 cfs 0.309 af Subcatchment 2S: Proposed Runoff Area = 51,189 sf 76.20% Impervious Runoff Depth >2.77" Tc =5.0 min CN =89 Runoff =5.99 cfs 0.272 af Total Runoff Area = 2.350 ac Runoff Volume = 0.581 of Average Runoff Depth = 2.97" 18.42% Pervious = 0.433 ac 81.58% Impervious = 1.917 ac MCD09065 Oak Park Heights Type 1124 -hr 10 -yr Rainfall = 4.15" Prepared by Landform Printed 8/2/2012 HydroCAD® 9.10 s/n 01542 © 2009 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 1S: Existing [49] Hint: Tc <2dt may require smaller dt Runoff = 6.54 cfs @ 11.95 hrs, Volume= 0.309 af, Depth> 3.16" Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs Type II 24 -hr 10 -yr Rainfall= 4.15" Area (sf) CN Description 6,673 61 >75% Grass cover, Good, HSG B 44,516 98 Paved parking & roofs 51,189 93 Weighted Average 6,673 13.04% Pervious Area 44,516 86.96% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 1S: Existing Hydrograph z 7 = 0 Runoff 6 cfs Type II 24 -hr 10 -yr I 6= Rainfall= 4.15" 5- Runoff Area = 51,189 sf Runoff Volume =0.309 af 4= Runoff Depth >3.16" LL = Tc =5.0 min 3- CN =93 2 1 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) MCD09065 Oak Park Heights Type 1124 -hr 10 -yr Rainfall =4.15" Prepared by Landform Printed 8/2/2012 HydroCAD® 9.10 s/n 01542 © 2009 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 2S: Proposed [49] Hint: Tc <2dt may require smaller dt Runoff = 5.99 cfs @ 11.95 hrs, Volume= 0.272 af, Depth> 2.77" Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs Type II 24 -hr 10 -yr Rainfall= 4.15" Area (sf) CN Description 12,184 61 >75% Grass cover, Good, HSG B 39,005 98 Paved parking & roofs 51,189 89 Weighted Average 12,184 23.80% Pervious Area 39,005 76.20% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 2S: Proposed Hydrograph [7 Runoff 5.99 cfs 6 Type II 24 -hr 10 -yr Rainfall= 4.15" 5- Runoff Area = 51,189 sf 4- Runoff Volume =0.272 of Runoff Depth >2.77" LL Tc =5.0 min 3_ = CN =89 2- O 1 # 0 o - /taree lfee,/��.1Zirdre... 499:#//. /. r .. mil.� Zet / 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) MCD09065 Oak Park Heights Type 1124 -hr 100 -yr Rainfall= 5.90" Prepared by Landform Printed 8/2/2012 HydroCAD® 9.10 s/n 01542 © 2009 HydroCAD Software Solutions LLC Page 8 Time span =5.00 - 20.00 hrs, dt =0.05 hrs, 301 points Runoff by SCS TR -20 method, UH =SCS Reach routing by Stor- Ind +Trans method - Pond routing by Stor -Ind method Subcatchment 1S: Existing Runoff Area = 51,189 sf 86.96% Impervious Runoff Depth >4.75" Tc =5.0 min CN =93 Runoff =9.62 cfs 0.466 af Subcatchment 2S: Proposed Runoff Area = 51,189 sf 76.20% Impervious Runoff Depth >4.35" Tc =5.0 min CN =89 Runoff =9.12 cfs 0.426 af Total Runoff Area = 2.350 ac Runoff Volume = 0.892 af Average Runoff Depth = 4.55" 18.42% Pervious = 0.433 ac 81.58% Impervious = 1.917 ac MCD09065 Oak Park Heights Type 1124 -hr 100 -yr Rainfall = 5.90" Prepared by Landform Printed 8/2/2012 HydroCAD® 9.10 s/n 01542 © 2009 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 1S: Existing [49] Hint: Tc <2dt may require smaller dt Runoff = 9.62 cfs @ 11.95 hrs, Volume= 0.466 af, Depth> 4.75" Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs Type II 24 -hr 100 -yr Rainfall = 5.90" Area (sf) CN Description 6,673 61 >75% Grass cover, Good, HSG B 44,516 98 Paved parking & roofs 51,189 93 Weighted Average 6,673 13.04% Pervious Area 44,516 86.96% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 1S: Existing Hydrograph ❑ Runoff 10 r 21 1 Type II 24-h r 100 -yr 9 1 Rainfall- 5.90" 8 Runoff Area = 51,189 sf Runoff Volume =0.466 af 6 Runoff Depth >4.75" LL 5 Tc =5.0 min 4 $ CN =93 3 2 1 4 0 _ 5 6 7 8 9 • 10 • 11 12 13 14 15 16 17 18 19 20 Time (hours) MCD09065 Oak Park Heights Type 1124 -hr 100 -yr Rainfall = 5.90" Prepared by Landform Printed 8/2/2012 HydroCAD® 9.10 s/n 01542 © 2009 HydroCAD Software Solutions LLC Page 10 Summary for Subcatchment 2S: Proposed [49] Hint: Tc <2dt may require smaller dt Runoff = 9.12 cfs @ 11.95 hrs, Volume= 0.426 af, Depth> 4.35" Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs Type II 24 -hr 100 -yr Rainfall = 5.90" Area (sf) CN Description 12,184 61 >75% Grass cover, Good, HSG B 39,005 98 Paved parking & roofs 51,189 89 Weighted Average 12,184 23.80% Pervious Area 39,005 76.20% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 2S: Proposed Hydrograph 10_ ❑ Runoff 1 9.12 cfs 9 = Type II 24-h r 100 -yr 6 Rainfall_5.90" Runoff Area= 51,189 sf 6- Runoff Volume =0.426 of R Depth >4.35" ° 5 Tc -5.0 min LL 4_ CN =89 3_ 2= le~ 5 6 7 S 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) • • • • LANDF ORM STORM SEWER DESIGN CALCULATIONS From Site to Finish • • • • DATE 08/02/12 FILE Storm Sewer Design Calcs - MCD12147.sis PROJECT NAME McDonald's STORM FREQUENCY I 10 I years PROJECT BUMMER MCD12147 CALCULATIONS BY CNC PROJECT LOCATION Oak Park Heights, MN IN STATE ZONE I 1 I PROJECT ENGINEER C. Call • Segment A - Tab. Areas C- Coal. Tc - Time of Uric. I - Intensity Q - Rate Pipe Upstream Structure Downstream Structure From To CB Pipe CB Pipe CB Pipe Total CB Total CB Pipe Len. Dia. Grade mart Man's. Vel. Cap. Excess Ac. Ac. Indiv. Avg. Min. Min. Min. InAir In/Hr CFS CFS Ft In. % n Ft/S CFS Cap. Structure Top Rim Invert Build She Casting Structure Top Rim Inlet Match Drop (F1) Build Comments CB 107 STMH 106 0.30 030 0.74 0.74 5.0 0.0 5.0 7.10 7.10 1.6 1.6 8 12 1.00 HDPE 0.010 5.9 4.6 3.1 CB 107 906.73 903.73 3.00 27* STMH 106_ 907.10 903.65 Drop 2.65 3.45 STMH 106 CB 105 0.00 0.30 0.00 0.74 0.0 NA 5.0 0.00 7.10 0.0 1.6 161 15 0.00 HOPE 0.010 00 0.0 NA STMH 106 907.10 901.00 6.10 48" CB 105 905.88 901.00 Invert 4.88 CB 105 CB 102 0.17 0.47 0.86 0.79 5.0 NA 5.0 7.10 7.10 1.1 2.6 63 15 0.00 HDPE 0.010 0.0 0.0 NA CB 105 , 905.88 901.00 4.88 45 C8102 906.50 901.00 Drop (1.25) 5.50 RD B CO 2 0.06 0.06 0.95 0.95 5.0 0.1 5.1 7.10 7.10 0.4 0.4 27 8 1.00 PVC 0.010 4.5 1.6 1.2 RD B 908.50 904.02 4.48 CO 2 907.75 903.76 Invert 4.00 CO2 NYLOPLAST 0.00 0.06 0.00 0.95 0.0 0.1 5.2 0.00 7.10 0.0 0.4 20 8 1.00 PVC 0.010 4.5 1.6 1.2 CO 2 907.75 903.76 4.00 NYLOPLAS" 907.10 903.55 Invert 3.55 I RDA NYLOPLAST 0.06 0.06 0.95 0.95 5.0 0.1 , 5.1 7.10 7.10 0.4 0.4 16 , 8 1.00 PVC 0.010 4.5 1.6 1.2 RDA 908.50 903.71 4.79 NYLOPLAS1 907.10 903.55 Invert 3.55 NYLOPLAST CO 1 0.05 0.16 0.25 0.75 5.0 0.1 5.3 7.10 7.10 0.1 0.9 31 8 1.00 PVC 0.010 4.5 1.6 0.7 VYLOPtAS" 907.10 903.55 3.55 CO 1 907.80 903.25 Invert 4,55 CO 1 CB 104 0.00 0.16 0.00 0.75 0.0 0.1 5.4 0.00 7.10 0.0 0.9 37 8 1.00 PVC 0.010 4.5 1.6 0.7 CO 1 907.80 903.25 4.55 CB 104 906.73 90288 Drop 1.88 3.85 CB 104 CB 103 0.35 0.51 0.70 0.71 5.0 NA 5.4 7.10 7.10 1.8 2.6 156 15 0.00 HOPE 0.010 0.0 0.0 NA CB 104 906.73 901.00 5.73 46• 08 103 906.10 901.00 Invert 5.10 CB 103 CB 102 0.18 0.89 0.80 074 5.0 NA 5.4 7.10 7.10 1.0 3.6 72 15 0.00 HDPE 0.010, 0.0 0.0 NA CB 103 906.10 901.00 5.10 411* CB 102 906.50 901.00 Drop (1.25) 5.50 CB 102 CB 101 0.06 1.22 0.58 0.75 5.0 0.1 5.5 7.10 6.95 0.3 6.4 35 15 1.00 RCP 0.013 5.3 6.5 0.1 CB 102 906.50 902.25 4.25 60' CB 101 905.20 901.90 Wed 3.30 ..� <„ ,�.�.. x. , McDONALD'S t ' - : H- T RESTAURANT ' eo,.- aA"., OAK PARK HEIGHTS, MN , o,. o b o,. 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