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Home My WebLink About2016-06-29 Sargent & Lundy Stormwater Calculations ISSUE SUMMARY Form SOP-0402-07, Revision 11 DESIGN CONTROL SUMMARY CLIENT: Xcel Energy UNIT NO.: 1 PAGE NO.: 1 PROJECT NAME: Baytown Substation PROJECT NO.: 13040-089 S&L NUCLEAR QA PROGRAM CALC.NO..: BYT-C-1 APPLICABLE 0 YES 0 NO TITLE: Stormwater Drainage Calculations EQUIPMENT NO.: N/A IDENTIFICATION OF PAGES ADDED/REVISED/SUPERSEDEDNOIDED&REVIEW METHOD Pages(including issue summary):12 Attachment pages:20 INPUTS/ASSUMPTIONS Total pages(including issue summary):32 :4 VERIFIED ❑ UNVERIFIED REVIEW METHOD: Detailed REV.: 0 STATUS: 0 APPROVED 0 SUPERSEDED BY CALCULATION NO. ❑VOID DATE FOR REV.: PREPARER: Mohammad Karim DATE: 06/29/2016 REVIEWER: Mark Bernardi Reis DATE: 06/29/2016 APPROVER: DATE: IDENTIFICATION OF PAGES ADDED/REVISED/SUPERSEDEDNOIDED&REVIEW METHOD INPUTS/ASSUMPTIONS ❑ VERIFIED ❑ UNVERIFIED REVIEW METHOD: REV.: STATUS: 0 APPROVED ❑SUPERSEDED BY CALCULATION NO. ❑VOID DATE FOR REV.: PREPARER: DATE: REVIEWER: DATE: APPROVER: DATE: IDENTIFICATION OF PAGES ADDED/REVISED/SUPERSEDEDNOIDED&REVIEW METHOD INPUTS/ASSUMPTIONS ❑ VERIFIED ❑ UNVERIFIED REVIEW METHOD: REV.: STATUS: ❑APPROVED ❑SUPERSEDED BY CALCULATION NO. ❑VOID DATE FOR REV.: PREPARER: DATE: REVIEWER: DATE: APPROVER: DATE: NOTE: PRINT AND SIGN IN THE SIGNATURE AREAS Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 2 of 12 TABLE OF CONTENTS SECTION PAGE 1.0 PURPOSE AND SCOPE 4 2.0 DESIGN INPUT 4 3.0 ASSUMPTIONS 5 4.0 ACCEPTANCE CRITERIA 5 5.0 METHODOLOGY 5 6.0 CALCULATIONS 7 7.0 RESULTS AND CONCLUSIONS 11 8.0 REFERENCES: 12 Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 3 of 12 ATTACHMENTS PAGES 1 EXISTING &PROPOSED SITE LAYOUT 2 2 SITE DRAINAGE 1 3 POND OUTLET STRUCTURE DETAIL 1 4 PONDPACK PRE-DEVELOPED PLAN AND OUTPUT 5 5 PONDPACK POST-DEVELOPED PLAN AND OUTPUT 7 6 MIDS OUTPUT 1 7 PONDPACK PRE/POST PEAK FLOWS 3 Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 4 of 12 1.0 PURPOSE AND SCOPE The Baytown substation located in Washington County, Minnesota is being expanded to accommodate new equipment.The purpose of this calculation is to design the stormwater system that is required by the Middle St. Croix Watershed Management Organization(MSCWMO). This calculation sizes the stormwater system consisting of a swale, sediment forebay, bioretention basin and stormwater detention pond needed to accommodate runoff from the newly developed area in accordance with the Middle St. Croix Watershed Management Plan(Reference 8.1)and the Minnesota Stormwater Manual (Reference 8.3). This calculation includes the parameters used to design the new stormwater system. 2.0 DESIGN INPUT 2.1 The existing substation and proposed expansion are illustrated in Attachment 1. 2.2 Areas • Total disturbed area=0.71 acres • Impervious area(pre-construction)=0.45 acres • Impervious area(post-construction)=0.73 acres • Net increase of impervious area=0.28 acres • Drainage area to the sediment forebay=0.58 acres 2.3 Manning's n-values for materials are listed in Table 2.1 below: Table 2.1: Material Manning's n-values (Reference 8.4) Concrete: 0.013 Aggregate 0.011 Grass 0.15 2.4 Rainfall information is obtained from the Middle St. Croix Watershed Management Plan (Reference 8.1). The 2-yr, 10-yr, and 100-yr,24-hour storm were considered. 2.5 Washington County, MN has a Type II Rainfall Distribution(Reference 8.3). 2.6 Curve numbers for the NRCS Peak Discharge Method(Reference 8.4)are provided below: Gravel: 91 Pond/Impervious: 98 Grassland—Good: 80 Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 5 of 12 3.0 ASSUMPTIONS 3.1 The minimum Time of Concentration(Tc)for any area is 5 min. 3.2 The Soil type in the proposed development is prominently silts and clayey fine sands (CL). The Hydrologic Soil Group(HSG)classification for the area will be taken as soil Type D. 3.3 Mannings roughness coefficient for seeded channels is 0.03. 4.0 ACCEPTANCE CRITERIA The stormwater system must be constructed in accordance with the Middle St. Croix Watershed Management Plan(Reference 8.1)and the Minnesota Stormwater Manual (Reference 8.3).According to the Middle St. Croix Watershed Management Plan, the stormwater system must retain at least 0.55 inches of runoff from the newly developed impervious area, remove 75 percent of the annual total phosphorus load and remove 50 percent of the total suspended solids.The stormwater pond and bioretention basin must also drain down within 48 hours. The newly developed peak rate shall also not exceed the pre- developed peak rate of runoff for the 2-yr, 10-yr, and 100-yr—24 hour storm events. The stormwater system must be designed to meet the following criteria: Permanent storage(sediment forebay)= 1,800 ft3 x 0.58 acres= 1,052 ft3 The sediment forebay must provide the minimum permanent storage as required by the Minnesota Stormwater Manual. The bioretention basin will provide the minimum retention requirement of 0.55"of runoff from the proposed impervious area. Retention from newly developed area(bio-retention basin)= (0.55"/(12"/ft)X(0.28 acres x 43,560 ft3)= 559 ft3 The Minnesota Stormwater Manual requires the storage volume of a pond to include permanent storage of 1,800 cubic feet per acre that drains to the pond. 5.0 METHODOLOGY 5.1 Substation Grading Design The proposed expanded substation will be crowned with a high point extending along the center of the substation as shown in Attachment 1. Slopes convey runoff from the southern half of the substation pad to the new stormwater swale. 5.2 Swale Design The stormwater swale that drains site runoff to the stormwater pond is designed using Mannings equation(Reference 8.4): Q=VxA Q = Discharge(cfs) V=Average velocity(ft/s) Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 6 of 12 A= Flow area(ft2) The average velocity, V, can be calculated as: V=(1.49/n)xr2r3xs'12 n= Mannings roughness coefficient r= Hydraulic radius(ft) s=Slope(ft/ft) The calculated capacity of the stormwater swale is compared to the volume of runoff draining into the swale to determine if the stormwater swale's capacity is sufficient. 5.3 Sediment Forebay and Bioretention Basin Prior to entering the stormwater pond, site runoff will drain to a sediment forebay and bioretention basin as shown on Attachment 1. The sediment forebay and bioretention basin will improve water quality by allowing sediment to accumulate prior to entering the stormwater pond thus reducing the pollutant load concentrations. The addition of these basins will only affect the time of concentration and not impact the overall design of the stormwater system. The storage volume provided within the sediment forebay and the bioretention system will increase the time of concentration and lead to lower peak inflow to the stormwater pond. 5.4 Stormwater Pond Design The stormwater pond is designed to accommodate storage for the volume of stormwater runoff produced from a 100 year—24 hour storm event. Pondpack v8.0(Reference 8.5) is used for the pond routing and peak flow rate calculations. The software utilizes the NRCS Graphical Peak Discharge Method to generate hydrographs. Runoff is calculated using the NRCS Runoff Curve Number Method. To determine peak runoff flow rates, pond storage, and an adequate outlet structure PondPack requires the following user defined inputs: • The NRCS Rainfall Distribution Type • Frequency Precipitation Data P • Drainage Areas • Curve Numbers • Time of Concentration • Pipe Data(size, slope, manning's n-value) A stormwater swale located south of the site collects runoff from the newly developed area and drains it to the sediment forebay. The sediment forebay discharges to the bioretention area. Flow into the bioretention area is bypassed into the stormwater pond if ponding exceeds 3"depth in the bioretention area. The developed release rate is controlled by an outlet structure designed to maintain release rates and drain the pond within 48 hours for the 2, 10, and 100-year,24-hour rainfall event. An outlet structure is constructed within the northern berm of the stormwater pond and discharges downstream to an existing catch basin. Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 7 of 12 5.4 Outlet Structure Design An outlet structure is constructed consisting of the following; • 48-inch diameter manhole structure in the perimeter berm • 3-inch diameter holes placed at different elevations • 12"corrugated metal pipe 5.5 Minimal Impact Design Standards(MIDS) A Minimal Impact Design Standards calculator provided by the Minnesota Pollution Control Agency is used to determine the pollutant reduction capability of the proposed stormwater pond.The MIDS calculator is an excel spreadsheet that calculates pollutant loads using the runoff reduction method based on input parameters by the users (Reference 8.6).The MIDS spreadsheet is be used to verify the minimum total annual phosphorus load requirement is satisfied. 6.0 CALCULATIONS 6.1 Time of Concentration(Tc) Rainfall intensity is based on the time of concentration. The travel time is estimated using the TR-55 Method(Equation 6.1, and Equation 6.2 Reference 8.4). Equation 6.1 equates the travel time for sheet flow, which is assumed to be the first 300 feet of travel distance. Equation 6.2 equates the travel time for shallow concentrated flow,which is for the remaining distance. T = 0.007(nL)08 [Eqn 6.1] 2)°.5 S°.4 • Ti=Travel Time(hr) • n= Manning's Roughness Coefficient • L= Flow Length (ft) • P2=2-year,24-hour rainfall(in) • s=Slope of Hydraulic Grade Line(land slope,ft/ft) T = [Eqn 6.2] 3600 x V • Ti=Travel Time(hr) • L= Flow Length(ft) • V=Average Velocity(ft/s) Time of Concentration for pre-and post-developed conditions are given in Table 6.1 below. The drainage path of each sub-area is shown in Attachment 2. Distances and slopes of each path are entered and calculated using the above equations in PondPack (Reference 8.5)as shown in Attachment 4. Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 8 of 12 Table 6.1 Time of Concentration Summary Area Name Tc(min) Description Pre-development 3.58- Runoff from existing substation pad use 5 and surrounding grass area Post-development 4.98- Runoff from newly developed substation pad use5 Since the time of concentration is less than 5 minutes for the pre-and post-developed condtions, 5 minutes is used. 6.2 Stormwater Swale The capacity of the stormwater swale is determined using Mannings equation described in Section 5.5. The stormwater swale is triangular, 1 foot deep, 3:1 side slopes, 200 feet in length at 0.5%. The average velocity in the stormwater swale is: V=(1.49/n)xr213xs112=(1.49/0.03)x0.47213x0.0051/2=2.1 ft/s n = Mannings roughness coefficient=0.03(Assumption 3.3) r= Hydraulic radius(ft)=a/p=0.47 a=Area(ft2)=3 ft2 p=wetted perimeter(ft)=6.32 ft s= Slope(ft/ft)=0.005 ft/ft Q=VxA Stormswale capacity=Q =2.1 ft/s x 3 ft2=6.3 cfs According to the PondPack simulation,the peak discharge resulting from 100-yr, 24-hour storm draining into the stormwater swale is 1.9 cfs.The stormwater swale is therefore capable of handling the peak discharge of a 100-yr, 24-hour storm. 6.3 Stormwater Pond Design The stormwater pond dimensions and details are provided in Attachment 3 and are also shown in Table 6.2. Calculated time of concentration values from PondPack are shown in Table 6.1. The Curve Numbers as described in Section 2.0 are applied for each area. Hydrologic models for the pre/post-develop conditions are created in PondPack from the user defined input. Inflow/oufflow hydrographs are generated and peak runoff rates are determined. With the given inputs for the pond elevation storage and outlet structure design, a Pond Pack storm routing model is created and the pond capacity for the design rainfall events is analyzed. The pond elevation/storage is provided in Table 6.2. For Pondpack output see Table 6.3 and Attachments 4 and 5. Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 9 of 12 Table 6.2 Stormwater Pond Dimensions Elevation (ft) Area(acre) Comments 935.50 0.036 Bottom of pond 936.00 0.043 937.00 0.058 938.00 0.098 939.00 0.150 Top of pond Table 6.3 Post/Pre Developed Rates Design Storm Max Water Pre Post Pond Storage(Ac- (24 Hour Storm Elevation (ft) Development Development ft) Event) Peak Flow Peak Flow (cfs) (cfs) 2 year 936.72 1.11 0.35 0.055 10 year 937.36 2.27 0.66 0.094 100 year 938.24 5.20 2.95 0.172 6.4 Sediment Forebay and Bioretention Basin The sediment forebay will provide the minimum permanent storage of at least 1,800 cubic feet per acre that drains to the pond.According to Table 6.4 below, the sediment forebay will provide approximately 2,964 ft3 of storage which exceeds the 1,052 ft3 of storage required as calculated in section 4. Table 6.4 Sediment Forebay Dimensions Elevation(ft) Area(fe) Volume(ft') 935.00 484 0 936.00 784 628 937.00 1,156 964 938.00 1,372 1,372 =2,964 The bio-retention basin is designed in accordance with the Minnesota Stormwater Manual(Reference 8.3)which requires a maximum drawdown time of 48 hours. The bioretention media composition consists of Mix D which has a hydraulic conductivity of 1 to 4 inches per hour.To be conservative, 1 inch is used to determine the drawdown time in the bioretention basin. The depth of the bioretention basin is 21 inches. Drawdown time=21"/(1"/hr)=21 hours The drawdown time is less than the maximum allowable drawdown time as required by the Minnesota Stormwater Manual. • The surface area of the bioretention basin is determined using the following equation obtained from the Minnesota Stormwater Manual(Reference 8.4): As =V,N/Do AS = Surface area(ft2) VW =Water treatment volume of the area contributing runoff(ft3)= 559 ft3(Section 4.0) Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 10 of 12 Do = Storage depth of ponded water(ft)=3" (Attachment 1) AS = 559 ft3/(3"/12') =2,236 ft2 As shown on Attachment 1, page 2,the bioretention basin will have a depth of 21" (18" Media Mix D depth +3" ponding depth)with a surface area of 2,236 square feet. Therefore it meets the minimum requirement of 559 cubic feet of retention from the newly developed impervious area as required by the Middle St. Croix Watershed Management Plan(Reference 8.1). 6.5 Minimal Impact Design Standards(MIDS) The MIDS spreadsheet calculates the pollutant load reductions for phosphorus and total suspended solids using user input land use areas, routing information and design parameters. The following equation is used by the MIDS spreadsheet to calculate the phosphorus and total suspended solids reduction(Reference 8.3): PRtot =(RVR x PRRet)+((100—RVR)x PRover) • PRtot =Annual total pollutant removal rate RVR=Annual volume retained PRRet =Annual pollutant removal rate applied to annual water volume retained PRover =Annual removal rate applied to the annual water volume routed downstream The following removal rates were calculated by the MIDS spreadsheet and can also be found in Attachment 6: • Percent annual total phosphorus removed =75% • Percent annual total suspended solids removed =93.91% 6.6 Outlet Structure The outlet structure is a 48-inch diameter manhole with 3-inch diameter holes places at different elevation levels in a weir wall to release a storm event with an outflow rate at or below pre-developed rates. PondPack utilizes the Orifice Equation(Reference 8.5)for flow entering through the 3-inch diameter openings to calculate the incoming flow rate (Q). Q=CdA(2gh)o.e h= height of water above opening A=area of opening g=gravitational constant=32.2 ft/s2 Cd =discharge coefficient=0.6 Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 11 of 12 Table 6.5 Outlet Structure Design Invert Elevation Feature Type No. of Features Size 939.00 Top of Outlet Manhole 1 48" Diameter 938.15 Weir 1 936.75 Opening 1 3" Diameter 936.25 Opening 1 3" Diameter 935.50 Opening 1 3" Diameter 935.50 Outlet Pipe 1 12" Diameter 7.0 RESULTS AND CONCLUSIONS 7.1 Stormwater Swale The stormwale swale has a capacity to handle 6.3 cfs of runoff which is more than the required 1.9 cfs of discharge into the stormwater swale. 7.2 Sediment Forebay and Bioretention Basin The sediment forebay provides a storage capacity of 2,964 ft3 which is greater than the minimum permanent storage of 1,052 ft3 of storage required. The bioretention basin meets the minimum requirement of 0.55"of retention of the newly developed impervious area and also has a drawdown time of 21 hours which is less than the maximum allowable drawdown time of 48 hours. 7.3 Stormwater Pond The post-development peak flow rate from the pond is going to detain and drain runoff within 48 hours.Attachments 4 and 5 provide the discharge hydrograph that shows the pond release rate approaches zero in approximately 30 hrs. The stormwater pond is designed to restrict post-development discharge rates to less than or equal to the pre-development discharge rates(Attachment 7). The outlet structure is designed to accommodate storm events up to 100 year—24 hour storms. 7.4 Minimal Impact Design Standards According to MIDS spreadsheet(Attachment 6),the minimum pollutant load reductions have been satisfied. 75%of the annual phosphorus is removed and 93.91% of the total suspended solids are removed. 7.5 Conclusion The stormwater pond follows the discharge requirements of 48 hours. The developed runoff from the proposed substation pad is detained and released at acceptable rates through the proposed outlet structure. The stormwater swale, sediment forebay and bioretention basin meet the requirements as defined by the Middle St. Croix Watershed Management Plan and the Minnesota Stormwater Manual.All drainage features in the proposed laydown area meet the criteria specified in this calculation. The stormwater pond has the pollutant reduction capabilities needed to effectively remove the annual phosphorus load in accordance with the MIDS calculator. The proposed stormwater system satisfies all design criteria and therefore is acceptable. Xcel Energy—Baytown Calc No. BYT-C-1 Stormwater Drainage Calculation Rev. 0 Project No: 13040-089 Page 12 of 12 8.0 REFERENCES: 8.1 Middle St. Croix Watershed Management Organization—2015—2025 Watershed Management Plan 8.2 Minnesota Stormwater Manual. Minnesota Pollution Protection Agency. Version 2. January 2008. 8.3 Technical Paper No. 55, "Urban Hydrology for Small Watersheds" by U.S. Department of Agriculture, Washington, D.C. 1999. 8.4 Computer Programs: The following computer programs were used as a technical aide in the preparation of this calculation: 8.4.1 PondPack v8.0, Haestad Methods, Inc. 2002. S&L Software No. 03.7.712-8.0. The computer software listed above, accessed on the S&L LAN, has been validated per S&L Software Verification and Validation procedures for the program functions used in the calculation. 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D - Win t85a � g zi 'gilt• • 4 z co eg a: 3 1 _ 1 HI ! / H 31 1 �' i II O N N Ql t _.Y H1f1SM2,7 N - ..uawx a) 'I ? ) {il I Eda� oa I it a 'o. t r s g F or a) a t.,', igR lr. 1 °sr luu iii '.feta.11.1W i " i .�'.�s!� � H I a / 1 o ''. • ♦ 1 4� s H .O o 1144. 1 I ii F ' t fi yy I - --��Y. g3�fi i Z ( flj a|| V41 . | •!| 3§ 5 | 1Qi ii / 1 -i /(7)00 _ ` MIDI $ a ® i §|o§. 4 , §'§\P t | . | 7 | ~\ q ° >-Q ( P | | § 1 | | . § Di ` � ` . �) . | ' O| =M. / § , 2 § L | ttAtlirli‘al J411;:: N v C. ` C | i ., c��k� § . § �. k ( , CtIcL1 II 6P 12 14 ail . / r, 1 V) E k k go ) R 7! z | §l: § —_l _ , J± 41.! k,|:/! , 2 i ■ h . | | % 1 § / : § . . . — e § ik> - - - ! k 4. || | | ; § \ a , & 4 Attachment 4 Scenario Calculation Summary Scenario Summary ID 1 Label Pre-Development Notes Active Topology Pre-Development Active Topology Hydrology Pre-Development Hydrology Rainfall Runoff 85% Physical Pre-Development Physical Initial Condition Pre-Development Initial Condition Boundary Condition Pre-Development Boundary Condition Infiltration and Inflow Pre-Development Infiltration and Inflow Output Pre-Development Output User Data Extensions Pre-Development User Data Extensions PondPack Engine Calculation Options Base Calculation Options Output Summary Output Increment 0.050 hours Duration 48.000 hours Rainfall Summary Return Event Tag 2 Rainfall Type Time-Depth Curve Total Depth 2.8 in Storm Event 2 Year-24 Hour Executive Summary(Nodes) Label Scenario Return Truncation Hydrograph Time to Peak Flow Maximum Maximum Event Volume Peak (ft3/s) Water Pond (years) (ac-ft) (hours) Surface Storage Elevation (ac-ft) (ft) Pre- 0-1 Developme 2 None 0.062 11.950 1.11 (N/A) (N/A) nt Pre- Pre Developme 2 None 0.062 11.950 1.11 (N/A) (N/A) nt Executive Summary(Links) Label Type Location Hydrograph Peak Time Peak Flow End Point Node Flow Volume (hours) (ft3/s) Direction (ac-ft) Messages Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Attachment 4 Scenario Calculation Summary Scenario Summary ID 1 Label Pre-Development Notes Active Topology Pre-Development Active Topology Hydrology Pre-Development Hydrology Rainfall Runoff 85% Physical Pre-Development Physical Initial Condition Pre-Development Initial Condition Boundary Condition Pre-Development Boundary Condition Infiltration and Inflow Pre-Development Infiltration and Inflow Output Pre-Development Output User Data Extensions Pre-Development User Data Extensions PondPack Engine Calculation Options Base Calculation Options Output Summary Output Increment 0.050 hours Duration 48.000 hours Rainfall Summary Return Event Tag 10 Rainfall Type Time-Depth Curve Total Depth 4.2 in Storm Event 10 Year-24 Hour Executive Summary(Nodes) Label Scenario Return Truncation Hydrograph Time to Peak Flow Maximum Maximum Event Volume Peak (ft3/s) Water Pond (years) (ac-ft) (hours) Surface Storage Elevation (ac-ft) • (ft) Pre- 0-1 Developme 10 None 0.126 11.900 2.27 (N/A) (N/A) nt Pre- Pre- Developme 10 None 0.126 11.900 2.27 (N/A) (N/A) nt Executive Summary(Links) Label Type Location Hydrograph Peak Time Peak Flow End Point Node Flow Volume (hours) (ft3/s) Direction (ac-ft) Messages Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W - Watertown,CT 06795 USA +1-203-755-1666 Attachment 4 Scenario Calculation Summary Scenario Summary ID 1 Label Pre-Development Notes Active Topology Pre-Development Active Topology Hydrology Pre-Development Hydrology Rainfall Runoff 85% Physical Pre-Development Physical Initial Condition Pre-Development Initial Condition Boundary Condition Pre-Development Boundary Condition Infiltration and Inflow Pre-Development Infiltration and Inflow Output Pre-Development Output User Data Extensions Pre-Development User Data Extensions PondPack Engine Calculation Options Base Calculation Options Output Summary Output Increment 0.050 hours Duration 48.000 hours Rainfall Summary Return Event Tag 100 Rainfall Type Time-Depth Curve Total Depth 7.3 in Storm Event 100 Year-24 Hour Executive Summary(Nodes) Label Scenario Return Truncation Hydrograph Time to Peak Flow Maximum Maximum Event Volume Peak (ft3/s) Water Pond (years) (ac-ft) (hours) Surface Storage Elevation (ac-ft) (ft) Pre- 0-1 Developme 100 None 0.288 11.900 5.20 (N/A) (N/A) nt Pre- Pre Developme 100 None 0.288 11.900 5.20 (N/A) (N/A) nt Executive Summary(Links) Label Type Location Hydrograph Peak Time Peak Flow End Point Node Flow Volume (hours) (ft3/s) Direction (ac-ft) Messages Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Attachment 4 Subsection: Time of Concentration Calculations Return Event: 100 years Label: Pre Storm Event: 100 Year- 24 Hour Time of Concentration Results Segment#1: TR-55 Sheet Flow Hydraulic Length 50.00 ft Manning's n 0.011 Slope 0.010 ft/ft 2 Year 24 Hour Depth 2.8 in Average Velocity 0.85 ft/s Segment Time of 0.016 hours Concentration Segment#2: TR-55 Shallow Concentrated Flow Hydraulic Length 320.00 ft Is Paved? False Slope 0.015 ft/ft Average Velocity 1.98 ft/s Segment Time of Concentration 0.045 hours Time of Concentration(Composite) Time of Concentration 0.083 hours (Composite) Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Attachment 4 Subsection: Time of Concentration Calculations Return Event: 100 years Label: Pre Storm Event: 100 Year- 24 Hour ==== SCS Channel Flow R=Qa/Wp Tc= V=(1.49*(R**(2/3))*(Sf**-0.5))/n (Lf/V)/3600 R= Hydraulic radius Aq= Flow area,square feet Wp=Wetted perimeter,feet Where: V=Velocity,ft/sec Sf= Slope,ft/ft n= Manning's n Tc=Time of concentration,hours Lf= Flow length,feet ==== SCS TR-55 Shallow Concentration Flow Unpaved surface: V= 16.1345*(Sf**0.5) Tc= Paved Surface: V= 20.3282*(Sf**0.5) (Lf/V)/3600 V=Velocity,ft/sec Where: Sf=Slope,ft/ft Tc=Time of concentration,hours Lf= Flow length,feet • Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Attachment 5 Scenario Calculation Summary Scenario Summary ID 23 Label Post-Development Notes Active Topology Post-Development Active Topology Hydrology Post-Development Hydrology Rainfall Runoff 85% Physical Post-Development Physical Initial Condition Post-Development Initial Condition Boundary Condition Post-Development Boundary Condition Infiltration and Inflow Post-Development Infiltration and Inflow Output Post-Development Output User Data Extensions Post-Development User Data Extensions PondPack Engine Calculation Options Base Calculation Options Output Summary Output Increment 0.050 hours Duration 48.000 hours Rainfall Summary Return Event Tag 2 Rainfall Type Time-Depth Curve Total Depth 2.8 in Storm Event 2 Year-24 Hour Executive Summary(Nodes) Label Scenario Return Truncation Hydrograph Time to Peak Flow Maximum Maximum Event Volume Peak (ft3/s) Water Pond (years) (ac-ft) (hours) Surface Storage Elevation (ac-ft) (ft) Post- Grass Developme 2 None 0.027 11.950 0.48 (N/A) (N/A) nt Post- 0-1 Developme 2 None 0.125 12.200 0.35 (N/A) (N/A) nt Post- Pad Developme 2 None 0.066 11.900 1.19 (N/A) (N/A) nt Post- Pond(IN) Developme 2 None 0.125 11.900 2.19 (N/A) (N/A) nt Pond Poi (01.) Developme 2 None 0.125 12.200 0.35 936.72 0.055 nt Pond Pow Rainfall Developme 2 None 0.032 11.900 0.53 (N/A) (N/A) nt Executive Summary(Links) Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Attachment 5 Scenario Calculation Summary Scenario Summary ID 23 Label Post-Development Notes Active Topology Post-Development Active Topology Hydrology Post-Development Hydrology Rainfall Runoff 85% Physical Post-Development Physical Initial Condition Post-Development Initial Condition Boundary Condition Post-Development Boundary Condition Infiltration and Inflow Post-Development Infiltration and Inflow Output Post-Development Output User Data Extensions Post-Development User Data Extensions PondPack Engine Calculation Options Base Calculation Options Output Summary Output Increment 0.050 hours Duration 48.000 hours Rainfall Summary Return Event Tag 10 Rainfall Type Time-Depth Curve Total Depth 4.2 in Storm Event 10 Year-24 Hour Executive Summary(Nodes) Label Scenario Return Truncation Hydrograph Time to Peak Flow Maximum Maximum Event Volume Peak (ft3/s) Water Pond (years) (ac-ft) (hours) Surface Storage Elevation (ac-ft) (ft) Post- Grass Developme 10 None 0.053 11.900 0.96 (N/A) (N/A) nt Post- 0-1 Developme 10 None 0.215 12.150 0.66 (N/A) (N/A) nt Post- Pad Developme 10 None 0.112 11.900 1.99 (N/A) (N/A) nt Post- Pond(IN) Developme 10 None 0.215 11.900 3.76 (N/A) (N/A) nt Post- Pond (On) Developme 10 None 0.215 12.150 0.66 937.36 0.094 nt Pond Pow Rainfall Developme 10 None 0.050 11.900 0.80 (N/A) (N/A) nt Executive Summary(Links) Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Attachment 5 Scenario Calculation Summary Scenario Summary ID 23 Label Post-Development Notes Active Topology Post-Development Active Topology Hydrology Post-Development Hydrology Rainfall Runoff 85% Physical Post-Development Physical Initial Condition Post-Development Initial Condition Boundary Condition Post-Development Boundary Condition Infiltration and Inflow Post-Development Infiltration and Inflow Output Post-Development Output User Data Extensions Post-Development User Data Extensions PondPack Engine Calculation Options Base Calculation Options Output Summary Output Increment 0.050 hours Duration 48.000 hours Rainfall Summary Return Event Tag 100 Rainfall Type Time-Depth Curve Total Depth 7.3 in Storm Event 100 Year-24 Hour Executive Summary(Nodes) Label Scenario Return Truncation Hydrograph Time to Peak Flow Maximum Maximum Event Volume Peak (ft3/s) Water Pond (years) (ac-ft) (hours) Surface Storage Elevation (ac-ft) (ft) Post- Grass Developme 100 None 0.120 11.900 2.16 (N/A) (N/A) nt Post- 0-1 Developme 100 None 0.426 12.050 2.95 (N/A) (N/A) nt Post- Pad Developme 100 None 0.218 11.900 3.74 (N/A) (N/A) nt Post- Pond(IN) Developme 100 None 0.426 11.900 7.31 (N/A) (N/A) nt Pond Pow (OUT) Developme 100 None 0.426 12.050 2.95 938.24 0.172 nt Pond Post- Rainfall Developme 100 None 0.088 11.900 1.41 (N/A) (N/A) nt Executive Summary(Links) Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.561 6/27/2016 27 Siemon Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 —_ i Attachment 5 Subsection: Time of Concentration Calculations Return Event: 100 years Label: Grass Storm Event: 100 Year- 24 Hour Time of Concentration Results Segment#1: TR-55 Shallow Concentrated Flow Hydraulic Length 410.00 ft Is Paved? False Slope 0.015 ft/ft Average Velocity 1.98 ft/s Segment Time of 0.058 hours Concentration Time of Concentration(Composite) Time of Concentration 0.083 hours (Composite) Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Attachment 5 Subsection: Time of Concentration Calculations Return Event: 100 years Label: Grass Storm Event: 100 Year- 24 Hour ==== SCS TR-55 Shallow Concentration Flow Unpaved surface: V= 16.1345*(Sf**0.5) Tc= Paved Surface: V=20.3282*(Sf**0.5) (Lf/V)/3600 V=Velocity,ft/sec Where: Sf= Slope,ft/ft Tc=Time of concentration,hours Lf= Flow length,feet Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Attachment 5 Subsection: Time of Concentration Calculations Return Event: 100 years Label: Pad Storm Event: 100 Year- 24 Hour Time of Concentration Results Segment#1: TR-55 Sheet Flow Hydraulic Length 90.00 ft Manning's n 0.011 Slope 0.010 ft/ft 2 Year 24 Hour Depth 2.8 in Average Velocity 0.95 ft/s Segment Time of 0.026 hours Concentration Time of Concentration(Composite) Time of Concentration 0.083 hours (Composite) Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Attachment 5 Subsection: Time of Concentration Calculations Return Event: 100 years Label: Pad Storm Event: 100 Year- 24 Hour ==== SCS Channel Flow R=Qa/Wp Tc= V=(1.49*(R**(2/3))*(Sf**-0.5))/n (Lf/V)/3600 R= Hydraulic radius Aq= Flow area,square feet Wp=Wetted perimeter,feet Where: V=Velocity,ft/sec Sf=Slope,ft/ft n= Manning's n Tc=Time of concentration,hours Lf= Flow length,feet Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i Baytown Storm Water Pond Design.ppc Center [08.11.01.56] 6/27/2016 27 Siemon Company Drive Suite 200 W - - Watertown,CT 06795 USA +1-203-755-1666 Attachment 6 Minnesota MIDS Calculator--Version 2:June 2014 Notes: 1)Make sure macros are enabled.If not,Click Microsoft Office Button in upper left hand corner. Click"Excel Options".Click"Trost Center,click"Trust Center Settings"and then click"Macro Settings". Set Macro Settings to "Enable All Macros"and restart Excel. 2)Enter Site Information in blue cells below 3)Go to MIDS BMP Calculator tab and follow instruction on top of that page Project Name: Baytown User Name/Company Name: S&L Date: oen4/2o1e Project Description: substation Pad Expansion Legend r input cells Calculation cells Constant values V>uue obtained from another sheet Site Information Retention Requirment(inches):MEM This value has been changed from the recommended value of 1.1 ins Site's Zip code: Annual Rainfall(inches): 't"' ' Phosphorus EMC(mg/L):MIME TSS EMC(mgfL): Fraction of annual rainfall events that produce runoff: Total Watershed Area Totals Land Cover(acres) A soils B Soils C Soils D Soils (acres) Forest/Open Space(acres)--undisturbed,protected forest/open space or reforested land 0.00 Managed Turf(acres)--disturbed,graded for yards or other turf to be mowed/managed 0.23 Impervious Cover(acres) Total: 0.51 Watershed Area Routed to BMPs(Summary of"MIDS BMP Calculator"Tab Totals Land Cover(acres) A soils B Soils C Soils D Soils (acres) Forest/Open Space(acres)--undisturbed,protected forest/open space or reforested land _ 0.00 Managed Turf(acres)--disturbed,graded for yards or other turf to be mowed/managed 0.23 0.23 Impervious Cover(acres) 0.28 Total: 0.51 Summary Information Total impervious cover(acres) 0.28 Total watershed area(acres) 0.51 Site runoff coefficient,Rv 0.63 %Impervious 55% Development volume retention requirement(cubic feet) 559 Volume removed by BMPs(cubic feet) 93 Note: Additional volume removal needed to meet requirement(cubic feet) 466 Green cells will fill in when MImp BMP Calculator tab is Percent volume removed 16.64% complete Post-developoment annual volume(acre-ft) 0.78 Grey Cells are calculated Annual volume removed by BMP5(acre-ft) 0.06 abSite Information entered Percent annual volume removed 7.60% Post-development annual Particulate P load(Ib/yr) 0.35 Annual Particulate load removed by BMPs(Ib/yr) 0.32 Post-development annual Dissolved P load(Ib/yr) 0.29 Annual Dissolved P load removed by BMP5(Ib/yr) 0.16 Percent annual TP removed 75.00% Post-development annual TSS load(Ib/yr) 115 Annual TSS load removed by BMPs(lb/yr) 108 Percent annual TSS removed 93.91 I 3 _ a — O f Y ._4.... g C� n 3 E i Q t o ro 0 I 3 e. / § aididillin g 0 0 o a o 0 0 4 E S I m a C E n I'w v N- m Cr CE ID, " W N f ° n y E � E F H U cr C6 Q . ,___,_ , §uc _...... , , ..I ( ! ! z I i ----_.__W,.._- ----- .., 1 1 . 1 : . i 1 , 8 I 8 K o 0 0 0 (Sell)MClA I I I Y I rml ( a Q E I _ 0 0 o C i ( E E I E o l^ o i 0 CCS .--- -_ 8 ! � I Q -- j 1 1 I I _ . .___ .gig 8