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HomeMy Public PortalAboutStormwater Drainage Analysis 5-15-14_201407211128491786 STORMWA TER DRAINA GE ANAL YSIS FOR PROPOSED pnwmacv Parcels 1230 4 0, 1230 5 1 & 1230 6A 0 653 & 655 Mount Auburn Street and 268 Arlington Street Town of Watertown,Massachusetts Middlesex County Prepared by: BOHLER ENGINEERING 352 Turnpike Road Southborough,MA 01772 Tel: (508)480-9900 Fax: (508)480-9080 �l01° G is M 42644 4 BEPC#W061049 APPENDICES A. LOCATION MAP B. EXISTING AND PROPOSED DRAINAGE TRIBUTARY MAPS C. STORMWATER ATTENUATION CALCULATIONS D. NRCS SOIL MAP & GROUNDWATER DEPTH MAP FROM GEOTECHNICAL INVESTIGATIONS E. LONG TERM OPERATION AND MAINTENANCE PLAN I. INTRODUCTION The following summary provides an analysis of the stormwater drainage conditions that will result from the development of a CVS Pharmacy. The site is located along the southern side of Mount Auburn Street (a.k.a. Route 16) at the corner of Arlington Street and is comprised of four parcels of land identified by the Watertown Assessor's Office as parcels 1230 4 0, 1230 6A 0, 1230 2 14 and 1230 5 1 which contain a total of approximately 67,186 square feet of land(or f 1.54 acres). This summary includes a limited analysis of the existing and proposed drainage characteristics of the site including building, parking and landscaped areas and provides an analysis of the proposed stormwater management which will help serve to reduce the quantity and rate of runoff leaving the site as well as comply with the Town of Watertown's Requirements for Stormwater Drainage to the maximum extent practicable. II.DRAINAGE—EXISTING SITE CONDITIONS The site currently consists of a gas service station,a mixed use building and an Elks Lodge building with associated parking that is entirely impervious.Under existing conditions,the site is broken into four watersheds that flow to their respective design points as further described below. Drainage Area E-1 is broken down to subwatersheds E-1A and E-1B. Drainage Area E-lA consists of±26,819 sf of impervious area. Stormwater from Drainage Area E-IA sheet flows uncontrolled to the existing catch basins before being conveyed through a series of manholes and pipe connections that eventually connect to the Wells Avenue drainage system. (Design Point 1-DPE1). Drainage Area E-1B consists of±10,350 sf of roofed area. Stormwater from Drainage Area E-1B is collected internally within the building before discharging via a roof leader along the south side of the building, which eventually connects to the Wells Avenue drainage system. (Design Point 1-DPE1). Drainage Area E-2 consists of±5,758 sf of impervious areas associated with the gas service station. Stormwater from Drainage Area E-2 sheet flows uncontrolled and untreated to Mount Auburn Street drainage system. (Design Point 2-DPE2). Drainage Area E-3 consists of f 17,143 sf of impervious areas associated with the gas service station and the former Elks Lodge building and parking. Stormwater from Drainage Area E-3 sheet flows uncontrolled and untreated to Arlington Street drainage system. (Design Point 3-DPE3). Drainage Area E-4 consists of ±2,858 sf of impervious areas associated with the southern parking area. Stormwater from Drainage Area E-4 sheet flows uncontrolled and untreated to the abutting property to the southeast. (Design Point 4-DPE4). This drainage areas above are shown on the "Existing Drainage Tributary Map" included within the Appendix B of this report. Based on our review of the Natural Resources Conservation Service (MRCS) WSS online soil databases, the underground soils at the subject site are classified as "Urban Land" and "Udorthents, sandy". Given this, we have assumed Hydrologic Group A soils at this site. As such, our drainage design utilizes an exfiltration rate of 2.41 in/hr which correlates to A soils and is indicated within the Rawls Table of the Massachusetts DEP Stormwater Management Handbook. III.DRAINAGE-PROPOSED SITE CONDITIONS The post-development conditions include the demolition of the existing gas service station facility and related amenities on parcel 1230 5 1, demolition of the existing Elks Lodge building and related amenities on parcel 1230 6A 0 as demolition of the existing building on parcel 1230 4 0. Once complete a new CVS Pharmacy will be constructed as illustrated on the Site Development Plans prepared by Bohler Engineering. Under proposed conditions the site is broken into four watersheds, which flow to their respective design points as further described below. Drainage Area P-1 is further broken down to subwatersheds P-IA,P-1B and P-1C. Drainage Area P-lA consists of ±20,305 sf of impervious areas and f2,425 sf of landscape areas totaling ±22,730 sf. Similar to the existing condition, stormwater from Drainage Area P-lA flows to the existing catch basins that will be retrofitted with inlet filters to promote water quality before eventually discharging to the Wells Avenue Drainage system. (Design Point 1- DPP I), however runoff rates and volumes for all storm events have been reduced in the post-redevelopment condition due to the added landscape areas within the rear parking lot. Drainage Area P-113 consists of±13,000 sf of roofed area. Stormwater from Drainage Area P-113 is collected internally within the building before being conveyed to an underground infiltration system. Drainage Area P-1 C consists of f4,190 sf of impervious areas and±950 sf of landscape areas totaling f5,140 sf. Stormwater from Drainage Area P-IC flows to a new stormwater quality inlet before being conveyed to an underground infiltration system with an isolator row. Stormwater quality will be improved due to the implementation of the stormwater quality inlet, underground infiltration basin isolator row and an Operation and Maintenance Plan. The infiltration isolator row is a row of underground chambers that is wrapped in fabric and captures sediment before it spreads through the underground system. Sediment is removed via vac truck on scheduled intervals. Drainage Areas P-1B and P-1C are both conveyed to an underground infiltration system which will infiltrate the runoff and improve groundwater recharge for storms up to and including the 100 year storm event. An overflow pipe has been proposed for higher storms to allow stormwater to discharge to the existing Wells Avenue drainage system (Design Point 1- DPP1). Again, this is similar to the existing condition, however runoff rates and volumes entering the Wells Avenue drainage system for all storm events have been reduced due to the implementation of the underground infiltration system. Drainage Area P-2 consists of ±270 sf of impervious area and ±67 sf of landscape areas totaling ±337 sf. Stormwater from Drainage Area P-2 sheet flows into the Mount Auburn Drainage system (Design Point 2- DPP2) as it does under existing condition, however runoff rates and volumes for all storm events have been reduced by limiting the contributing area. Drainage Area P-3 is further broken down to subwatersheds P-3A,P-313 and P-3C as further described below. Drainage Area P-3A consists of±15,192 sf of impervious areas and±813 sf of landscape areas totaling±16,005 sf. Stormwater from Drainage Area P-3A flows to a new stormwater quality inlet that connects to the Arlington Street Drainage system. (Design Point 3- DPP3). Note that runoff rates and volumes for all storm events have been reduced when compared to the existing condition. In addition, stormwater quality will be improved due to the implementation of the stormwater quality inlet and an Operation and Maintenance Plan. Drainage Area P-313 consists of a f2,907 sf of landscape area. Stormwater from this area infiltrates through a shallow depression which holds all storm events up to and including the 100 year storm before overflowing into the Arlington Street Drainage System(Design Point 3-DPP3). Drainage Area P-313 consists of a f1,657 sf of landscape area. Similar to Drainage Area P-313, stormwater from this area infiltrates through a shallow depression which holds all storm events up to and including the 100 year storm before overflowing into the Arlington Street Drainage System(Design Point 3- DPP3). Drainage Area P-4 consists of±620 sf of impervious areas and ±448 sf of landscape areas totaling f1,068 sf. Stormwater from Drainage Area P-4 is conveyed towards the southwest abutter, as it does under existing conditions,however runoff rates and volumes for all storm events have been reduced by limiting the contributing area and landscaped areas. Please refer to the "Proposed Drainage Tributary Map" included within the Appendix B of this report for a graphical representation of the proposed drainage areas. IV.DRAINAGE ANALYSIS METHODOLGY The methodology utilized to design the subject stormwater management system to demonstrate compliance with the Town of Watertown is based on the SCS TR 55 Urban Hydrology for small watersheds method. In addition, times of concentration were generated from the SCS TR 55 Urban Hydrology for small watersheds method. Runoff coefficients for the existing and proposed development conditions were developed using widely accepted runoff coefficients. Compliance with the Town of Watertown Requirements for Stormwater Drainage are the primary goals of the drainage system design. The rainfall rates used were based on the SCS TR 55 Urban Hydrology rates. V.DRAINAGE ANALYSIS RESULTS The tables below demonstrates that the post-development runoff rates and volumes to each design point associated with all storm events including the 2-year, 10-year, 25-year and 100-year storms will be decreased as a result of the proposed stormwater management system. This is the result of the decrease in impervious areas, the implementation of the proposed stormwater management system, including an underground infiltration basin which collects clean roof runoff, stormwater quality devices as well as the depressed landscape areas being utilized to further promote groundwater recharge and improve water quality. Table I - Stormwater Runoff Rates Summary to Design Point 1 (Wells Avenue Drainage System) Storm Frequency Existing Flow Proposed g' 2 year 2.57 2.37 -0.20 8% 10 year 3.75 3.69 -0.06 1.6% 25 year 4.43 4.37 -0.06 1.3% 100 year 5.44 5.43 -0.01 <1% Table 2 - Stormwater Runoff Volumes Summary to Design Point 1 (Wells Avenue Drainage System) Storm Frequency Existing Proposed VolumeVolume(ac-ft) 2 year 0.204 0.141 -0.063 31% 10 year 0.303 0.240 -0.063 21% 25 year 0.360 0.284 -0.076 21% 100 year 0.445 0.372 -0.073 16% Table 3- Stormwater Runoff Rates Summary to Design Point 2 (Mount Auburn Street Drainage System) Storm Frequency Existing Flow Proposed Flow Change 0/1) 1 2 year 0.40 0.02 -0.38 95% 10 year 0.58 0.03 -0.55 95% 25 year 0.69 0.03 -0.66 95% 100 year 0.84 0.04 -0.80 95% Table 4- Stormwater Runoff Volumes Summary to Design Point 2 (Mount Auburn Street Drainage System) 'ProposedStorm Frequency Existing , 2 year 0.032 0.001 -0.031 97% 10 year 0.047 0.002 -0.045 96% 1 25 year 0.056 0.002 -0.054 96% l 100 year 0.069 0.003 -0.066 96% Table 5- Stormwater Runoff Rates Summary to Design Point 3 (Arlington Street Drainage System) Storm Frequency Existing Flow Proposed Flow Change 2 year 1.18 1.04 -0.14 12% 10 year 1.73 1.56 -0.17 10% 25 year 2.04 1.86 -0.18 9% 100 year 2.51 2.30 -0.21 8% Table 6- Stormwater Runoff Volumes Summary to Design Point 3 (Arlington Street Drainage System) VolumeStorm Frequency Existing Proposed Change % Volume(11C-ft) 2 year 0.094 0.078 -0.016 17% 10 year 0.140 0.120 -0.020 14% 25 year 0.166 0.154 -0.012 7% 100 year 0.205 0.194 -0.011 5% Table 7- Stormwater Runoff Rates Summary to Design Point 4(Southeast Abutter) Storm Frequency Existing Flow Proposed FlowChange 2 year 0.20 0.02 -0.18 90% 10 year 0.29 0.05 -0.24 83% 25 year 0.34 0.07 -0.27 79% 100 year 0.42 0.10 -0.32 76% Table 8-Stormwater Runoff Volumes Summary to Design Point 4 (Southeast abutter) VolumeI Storm Frequency Existing Proposed Change % 2 year 0.016 0.002 -0.014 88% 10 year 0.023 0.004 -0.019 83% 25 year 0.028 0.005 -0.023 82% 100 year 0.034 0.007 -0.024 70% VI. CONCLUSIONS In conclusion, the proposed stormwater management system illustrated on the enclosed drawings results in a decrease in post-development peak stormwater runoff rates and volumes and an increase in the amount of annual groundwater recharge associated with the proposed redevelopment condition. In addition,the stormwater quality measures proposed will be improved when compared to the existing condition due to the implementation of the stormwater management system. As a result, the project complies with the Town of Watertown's Requirements for Stormwater Drainage and represents a significant improvement when compared to the existing condition. Appendix A s y: gig, F � � ► NO Awe r y 4rr Appendix B P %1 a s °. �i�' it � o •�' I! I *. E-4 IMPERVIOU5 =2,858 SF a &d - TC=6 MIN CN=96 •/�-� I I- C/i • _� it . • �— II 72•� �-� I _ • �• 'r -- ::";-irlt:f......:a µ'Ittu- -1•t"'rdr{': :..� - i! �f r• /• .•� r rO� to aw ---------------- 1 �y r-eii:ia it :.'r;�W. Y�:_•- �. _ ... I -. � r .. r _ —__ E-lBFj = f `\ TG•6 MLY � • 1 � WLL is J' E-2 v i I I yer •,i-^'• fA1PfryNDV6A.76e SF' _ Y i I • • •. r , It i r A rJv Tc-0 WQ , r J I I ;o 5:i �'.,1 - = CHUB ' r r G I I p:' jr JAn A o;;Y .. Q it II® ]EXISTING DRAINAGE n TRIBUTARY MAP JLAP PREPARED BY ==__=_M0U�TT AUBUA STREET (W WIDE) (61 B O H L E R (AKA MASSACHHUOSETTS UTE STATE HIGHWAY ,0. 16) ft (ASPHALT PAVEMENT( bQd E N G I N E E R I N G zp „` \\ NOT TO SCALE s s z N2� ,g) 0 P-4 f IMPERV = 0 SF P�RVIOUS=448 P�11� TOTAL=1,0665E �` MIN t IMPERVIOUS=20,305 SF TC CN=73 PERVIOU5 SF J TOTAL= SF TC=6 22 MIN MIN - CN-92 � J 1 P-3P + _ • yyy PER 02,907 ' TC6 MI= MIN. -n CN=39 '''•� v- f e � ,�.R_9 a �MPF,F'�!^rit-75•C'r'�- — -- ,s�xu I G iA1•16.iA5 SF �v e -.sh M•k 1[j C f 11i —�.au.r,YailllJly ur�.1..T�.—�orrt►�/A> 1 e �` ll . I ' P-3C- _ 1 1 PERVIOUS=1,657 TC=6MIN a 1� ,. — .__- �•I / CN=39 e 1 e .,,y... , i / I II I IMP@RypUy...fac SF � i PETmous.aeo sr /� CM•W / I I I• • - !„tee —— � � i IMPERVIOU�70 SF PROPOSED DRAINAGE 3e"��• PERVIOUS=67 SF TOTAL=3376F n TRIBUTARY MAP TC=6 MIN, ' CN=66 PREPARED BY IIL R....�. "T114 °�AuBu N STREET' � B O H L E R ad Mhn �� ~� - ® ® (A K A MASSACHRUSSE ES STATE HIGHWAY ENGINE E B I N G If '- (ASPHALT PAVEM16)ENT) If tr NOT TO SCALE Appendix C P-9 A ,E-1 A,-_ 4 HPE DPP1 To Wells Ave On-site to Wells Avenue o Drainage System Well Ave Drainage System Wells Ave Drainage Loading System P-1 B UG system To Wells St Drainage Roof to Wells Avenue System Drainage System FDPE-] DPP- E-� Mount Auburn stem Drainage Mount Auburn Drainage To Mount Auburn St To Mount Auburn Street y System Drainage System /P-36 �� Drainage System Landscaped area 1 - Dope- _DPP- B_3 Inf.Pond 1 o-- p_3C Arlington St Drainage Arlington St Drainage To Arlington St System System Landscaped area 2 Inf.Pond 2 Drainage System P-3A } DP�4; To Arlington St �_4 DPP d Drainage System To Southeast Abutter Southeast Abutter Southeast Abutter C P-4 j To Southeast Abutter Subcat Reach Aon Link Routing Diagram for Watertown KBS 4-24-14 Prepared by Bohler Engineering, Printed 6/27/2014 HydroCAD®10.00 s/n 08311 0 2013 HydroCAD Software Solutions LLC Watertown KBS 4-24-14 Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Page 2 Area Listing (all nodes) Area CN Description (acres) (subcatchment-numbers) 0.213 39 >75% Grass cover, Good, HSG A (P-1A, P-1C, P-2, P-3A, P-31B, P-3C, P-4) 2.027 98 Paved parking & roofs (E-1A, E-1B, E-2, E-3, E-4, P-1A, P-1C, P-2, P-4) 0.647 98 Paved parking, HSG A (P-1 B, P-3A) Watertown KBS 4-24-14 Type /// 24-hr 2YR Rainfall=3.10" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Pace 3 Summary for Subcatchment E-1A: On-site to Wells Avenue Drainage System Runoff = 1.85 cfs @ 12.08 hrs, Volume= 0.147 af, Depth= 2.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 26,819 98 Paved parkinq & roofs 26,819 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-1 B: Roof to Wells Avenue Drainage System Runoff = 0.71 cfs @ 12.08 hrs, Volume= 0.057 af, Depth= 2.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 10,350 98 Paved parkinq & roofs 10,350 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-2: To Mount Auburn Street Drainage System Runoff = 0.40 cfs @ 12.08 hrs, Volume= 0.032 af, Depth= 2.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 5.758 98 Paved parkinq & roofs 5,758 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Watertown KBS 4-24-14 Type 11124-hr 2YR Rainfall=3.10" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD0 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment E-3: To Arlington St Drainage System Runoff = 1.18 cfs @ 12.08 hrs, Volume= 0.094 af, Depth= 2.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 17,143 98 Paved parkins) & roofs 17,143 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-4: To Southeast Abutter Runoff = 0.20 cfs @ 12.08 hrs, Volume= 0.016 af, Depth= 2.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 2,858 98 Paved parking & roofs 2,858 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-1A: To Wells Ave Runoff = 1.35 cfs @ 12.09 hrs, Volume= 0.098 af, Depth= 2.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 20,305 98 Paved parking & roofs 2,425 39 >75% Grass cover, Good. HSG A 22,730 92 Weighted Average 2,425 10.67% Pervious Area 20,305 89.33% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Watertown KBS 4-24-14 Type 111 24-hr 2YR Rainfall=3.10" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paoe 5 Summary for Subcatchment P-1 B: To Wells St Drainage System Runoff = 0.90 cfs @ 12.08 hrs, Volume= 0.071 af, Depth= 2.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 13,000 98 Paved parking, HSG A 13,000 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment PAC: Loading Runoff = 0.25 cfs @ 12.09 hrs, Volume= 0.018 af, Depth= 1.83" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 4,190 98 Paved parking & roofs 950 39 >75% Grass cover, Good, HSG A 5,140 87 Weighted Average 950 18.48% Pervious Area 4,190 81.52% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-2: To Mount Auburn St Drainage System Runoff = 0.02 cfs @ 12.09 hrs, Volume= 0.001 af, Depth= 1.75" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 270 98 Paved parking & roofs 67 39 >75% Grass cover, Good, HSG A 337 86 Weighted Average 67 19.88% Pervious Area 270 80.12% Impervious Area Watertown KBS 4-24-14 Type ///24-hr 2YR Rainfall=3.10" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Page 6 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-3A: To Arlington St Drainage System Runoff = 1.04 cfs @ 12.08 hrs, Volume= 0.078 af, Depth= 2.55" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 813 39 >75% Grass cover, Good, HSG A 15,192 98 Paved parking, HSG A 16,005 95 Weighted Average 813 5.08% Pervious Area 15,192 94.92% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (fUsec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-313: Landscaped area 1 Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 2,907 39 >75% Grass cover, Good. HSG A 2,907 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, direct Summary for Subcatchment P-3C: Landscaped area 2 Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 1.657 39 >75% Grass cover. Good. HSG A 1,657 100.00% Pervious Area Watertown KBS 4-24-14 Type /// 24-hr 2YR Rainfall=3.10" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Paae 7 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, direct Summary for Subcatchment P-4: To Southeast Abutter Runoff = 0.02 cfs @ 12.10 hrs, Volume= 0.002 af, Depth= 0.92" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 2YR Rainfall=3.10" Area (sf) CN Description 620 98 Paved parking & roofs 448 39 >75% Grass cover, Good. HSG A 1,068 73 Weighted Average 448 41.95% Pervious Area 620 58.05% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Reach DPE-2: Mount Auburn Drainage System Inflow Area = 0.132 ac,100.00% Impervious, Inflow Depth = 2.87" for 2YR event Inflow = 0.40 cfs @ 12.08 hrs, Volume= 0.032 of Outflow = 0.40 cfs @ 12.08 hrs, Volume= 0.032 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPE-3: Arlington St Drainage System Inflow Area = 0.394 ac,100.00% Impervious, Inflow Depth = 2.87" for 2YR event Inflow = 1.18 cfs @ 12.08 hrs, Volume= 0.094 of Outflow = 1.18 cfs @ 12.08 hrs, Volume= 0.094 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPE-4: Southeast Abutter Inflow Area = 0.066 ac,100.00% Impervious, Inflow Depth = 2.87" for 2YR event Inflow = 0.20 cfs @ 12.08 hrs, Volume= 0.016 of Outflow = 0.20 cfs @ 12.08 hrs, Volume= 0.016 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Watertown KBS 4-24-14 Type ///24-hr 2YR Rainfall=3.10" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCADO 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paoe 8 Summary for Reach DPE1: Wells Ave Drainage System Inflow Area = 0.853 ac,100.00% Impervious, Inflow Depth = 2.87" for 2YR event Inflow = 2.57 cfs @ 12.08 hrs, Volume= 0.204 of Outflow = 2.57 cfs @ 12.08 hrs, Volume= 0.204 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-2: Mount Auburn Drainage System Inflow Area = 0.008 ac, 80.12% Impervious, Inflow Depth = 1.75" for 2YR event Inflow = 0.02 cfs @ 12.09 hrs, Volume= 0.001 of Outflow = 0.02 cfs @ 12.09 hrs, Volume= 0.001 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-3: Arlington St Drainage System Inflow Area = 0.367 ac, 94.92% Impervious, Inflow Depth = 2.55" for 2YR event Inflow = 1.04 cfs @ 12.08 hrs, Volume= 0.078 of Outflow = 1.04 cfs @ 12.08 hrs, Volume= 0.078 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-4: Southeast Abutter Inflow Area = 0.025 ac, 58.05% Impervious, Inflow Depth = 0.92" for 2YR event Inflow = 0.02 cfs @ 12.10 hrs, Volume= 0.002 of Outflow = 0.02 cfs @ 12.10 hrs, Volume= 0.002 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP1: Well Ave Drainage System Inflow Area = 0.938 ac, 91.74% Impervious, Inflow Depth = 1.67" for 2YR event Inflow = 2.08 cfs @ 12.12 hrs, Volume= 0.131 of Outflow = 2.08 cfs @ 12.12 hrs, Volume= 0.131 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Pond P131: Inf. Pond 1 Inflow Area = 0.067 ac, 0.00% Impervious, Inflow Depth = 0.00" for 2YR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Watertown KBS 4-24-14 Type/1/ 24-hr 2YR Rainfall=3.10" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Page 9 Peak Elev= 36.50' @ 0.00 hrs Surf.Area= 344 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) Volume Invert Avail.Storage Storaqe Description #1 36.50' 306 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 36.50 344 0 0 37.00 879 306 306 Device Routinq Invert Outlet Devices #1 Discarded 36.50' 2.410 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.00 cfs @ 0.00 hrs HW=36.50' (Free Discharge) L1=Exfiltration (Passes 0.00 cfs of 0.02 cfs potential flow) Summary for Pond PD2: Inf. Pond 2 Inflow Area = 0.038 ac, 0.00% Impervious, Inflow Depth = 0.00" for 2YR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Peak Elev= 37.50' @ 0.00 hrs Surf.Area= 169 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) Volume Invert Avail.Storage Storaqe Description #1 37.50' 147 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 37.50 169 0 0 38.00 418 147 147 Device Routing Invert Outlet Devices #1 Discarded 37.50' 2.410 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.00 cfs @ 0.00 hrs HW=37.50' (Free Discharge) L1=Exfiltration (Passes 0.00 cfs of 0.01 cfs potential flow) Watertown KBS 4-24-14 Type 111 24-hr 2YR Rainfall=3.10" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 @ 2013 HvdroCAD Software Solutions LLC Pape 10 Summary for Pond UG: UG system Inflow Area = 0.416 ac, 94.76% Impervious, Inflow Depth = 2.57" for 2YR event Inflow = 1.15 cfs @ 12.08 hrs, Volume= 0.089 of Outflow = 0.92 cfs @ 12.14 hrs, Volume= 0.089 af, Atten= 20%, Lag= 3.6 min Discarded = 0.03 cfs @ 9.29 hrs, Volume= 0.057 of Primary = 0.89 cfs @ 12.14 hrs, Volume= 0.033 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Peak Elev= 36.35' @ 12.14 hrs Surf.Area= 627 sf Storage= 1,000 cf Flood Elev= 38.10' Surf.Area= 627 sf Storage= 1,348 cf Plug-Flow detention time= 133.1 min calculated for 0.089 of(100% of inflow) Center-of-Mass det. time= 133.1 min ( 902.8 - 769.8 ) Volume Invert Avail.StoraQe Storage Description #1 34.00' 613 cf 11.00'W x 57.00'L x 3.50'H Prismatoid 2,195 cf Overall - 735 cf Embedded = 1,459 cf x 42.0% Voids #2 34.50' 735 cf StormTech SC-740 x 16 Inside#1 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.561 with 0.44' OverlaD 1,348 cf Total Available Storage Device Routinq Invert Outlet Devices #1 Discarded 34.00' 2.410 in/hr Exfiltration over Surface area #2 Primary 35.80' 12.0" Round Culvert L= 6.0' CMP, projecting, no headwall, Ke= 0.900 Inlet/Outlet Invert= 35.80' / 35.60' S= 0.03337' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf Discarded OutFlow Max=0.03 cfs @ 9.29 hrs HW=34.04' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.88 cfs, @ 12.14 hrs HW=36.35' (Free Discharge) L2=Culvert (Inlet Controls 0.88 cfs @ 1.99 fps) Watertown KBS 4-24-14 Type 111 24-hr 10YR Rainfall=4.50" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Paae 11 Summary for Subcatchment E-1A: On-site to Wells Avenue Drainage System Runoff = 2.71 cfs @ 12.08 hrs, Volume= 0.219 af, Depth= 4.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 26,819 98 Paved parking & roofs 26,819 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-1 B: Roof to Wells Avenue Drainage System Runoff = 1.04 cfs @ 12.08 hrs, Volume= 0.084 af, Depth= 4.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 10,350 98 Paved parkinq & roofs 10,350 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-2: To Mount Auburn Street Drainage System Runoff = 0.58 cfs @ 12.08 hrs, Volume= 0.047 af, Depth= 4.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 5,758 98 Paved parking & roofs 5,758 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Watertown KBS 4-24-14 Type 111 24-hr 10YR Rainfall=4.50" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paoe 12 Summary for Subcatchment E-3: To Arlington St Drainage System Runoff = 1.73 cfs @ 12.08 hrs, Volume= 0.140 af, Depth= 4.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 17.143 98 Paved parkinq & roofs 17,143 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-4: To Southeast Abutter Runoff = 0.29 cfs @ 12.08 hrs, Volume= 0.023 af, Depth= 4.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 2,858 98 Paved parkinq & roofs 2,858 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-1A: To Wells Ave Runoff = 2.11 cfs @ 12.08 hrs, Volume= 0.157 af, Depth= 3.60" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 20,305 98 Paved parking & roofs 2,425 39 >75% Grass cover. Good. HSG A 22,730 92 Weighted Average 2,425 10.67% Pervious Area 20,305 89.33% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Watertown KBS 4-24-14 Type 11124-hr 10YR Rainfall=4.50" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paqe 13 Summary for Subcatchment P-1 B: To Wells St Drainage System Runoff = 1.31 cfs @ 12.08 hrs, Volume= 0.106 af, Depth= 4.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 13,000 98 Paved parking, HSG A 13,000 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment PAC: Loading Runoff = 0.42 cfs @ 12.09 hrs, Volume= 0.030 af, Depth= 3.10" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 4,190 98 Paved parking & roofs 950 39 >75% Grass cover. Good, HSG A 5,140 87 Weighted Average 950 18.48% Pervious Area 4,190 81.52% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-2: To Mount Auburn St Drainage System Runoff = 0.03 cfs @ 12.09 hrs, Volume= 0.002 af, Depth= 3.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 270 98 Paved parking & roofs 67 39 >75% Grass cover, Good. HSG A 337 86 Weighted Average 67 19.88% Pervious Area 270 80.12% Impervious Area Watertown KBS 4-24-14 Type ///24-hr 10YR Rainfall=4.50" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 14 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-3A: To Arlington St Drainage System Runoff = 1.56 cfs @ 12.08 hrs, Volume= 0.120 af, Depth= 3.92" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Descriotion 813 39 >75% Grass cover, Good, HSG A 15.192 98 Paved parkinq, HSG A 16,005 95 Weighted Average 813 5.08% Pervious Area 15,192 94.92% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-313: Landscaped area 1 Runoff = 0.00 cfs @ 14.70 hrs, Volume= 0.001 af, Depth= 0.11" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 2,907 39 >75% Grass cover. Good, HSG A 2,907 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fUft) (ft/sec) (cfs) 6.0 Direct Entry, direct Summary for Subcatchment P-3C: Landscaped area 2 Runoff = 0.00 cfs @ 14.70 hrs, Volume= 0.000 af, Depth= 0.11" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Description 1,657 39 >75% Grass cover, Good. HSG A 1,657 100.00% Pervious Area Watertown KBS 4-24-14 Type 111 24-hr 10YR Rainfall=4.50" Prepared by Bohler Engineering Printed 6/27/2014 HydroCADI� 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Page 15, Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, direct Summary for Subcatchment P-4: To Southeast Abutter Runoff = 0.05 cfs @ 12.09 hrs, Volume= 0.004 af, Depth= 1.90" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 10YR Rainfall=4.50" Area (sf) CN Descriotion 620 98 Paved parking & roofs 448 39 >75% Grass cover. Good, HSG A 1,068 73 Weighted Average 448 41.95% Pervious Area 620 58.05% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Reach DPE-2: Mount Auburn Drainage System Inflow Area = 0.132 ac,100.00% Impervious, Inflow Depth = 4.26" for 10YR event Inflow = 0.58 cfs @ 12.08 hrs, Volume= 0.047 of Outflow = 0.58 cfs @ 12.08 hrs, Volume= 0.047 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPE-3: Arlington St Drainage System Inflow Area = 0.394 ac,100.00% Impervious, Inflow Depth = 4.26" for 10YR event Inflow = 1.73 cfs @ 12.08 hrs, Volume= 0.140 of Outflow = 1.73 cfs @ 12.08 hrs, Volume= 0.140 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPE-4: Southeast Abutter Inflow Area = 0.066 ac,100.00% Impervious, Inflow Depth = 4.26" for 10YR event Inflow = 0.29 cfs @ 12.08 hrs, Volume= 0.023 of Outflow = 0.29 cfs @ 12.08 hrs, Volume= 0.023 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Watertown KBS 4-24-14 Type 111 24-hr 10YR Rainfall=4.50" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Page 16 Summary for Reach DPE1: Wells Ave Drainage System Inflow Area = 0.853 ac,100.00% Impervious, Inflow Depth = 4.26" for 10YR event Inflow = 3.75 cfs @ 12.08 hrs, Volume= 0.303 of Outflow = 3.75 cfs @ 12.08 hrs, Volume= 0.303 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-2: Mount Auburn Drainage System Inflow Area = 0.008 ac, 80.12% Impervious, Inflow Depth = 3.00" for 10YR event Inflow = 0.03 cfs @ 12.09 hrs, Volume= 0.002 of Outflow = 0.03 cfs @ 12.09 hrs, Volume= 0.002 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-3: Arlington St Drainage System Inflow Area = 0.367 ac, 94.92% Impervious, Inflow Depth = 3.92" for 10YR event Inflow = 1.56 cfs @ 12.08 hrs, Volume= 0.120 of Outflow = 1.56 cfs @ 12.08 hrs, Volume= 0.120 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-4: Southeast Abutter Inflow Area = 0.025 ac, 58.05% Impervious, Inflow Depth = 1.90" for 10YR event Inflow = 0.05 cfs @ 12.09 hrs, Volume= 0.004 of Outflow = 0.05 cfs @ 12.09 hrs, Volume= 0.004 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP1: Well Ave Drainage System Inflow Area = 0.938 ac, 91.74% Impervious, Inflow Depth = 2.91" for 10YR event Inflow = 3.64 cfs @ 12.10 hrs, Volume= 0.227 of Outflow = 3.64 cfs @ 12.10 hrs, Volume= 0.227 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Pond PD1: Inf. Pond 1 Inflow Area = 0.067 ac, 0.00% Impervious, Inflow Depth = 0.11" for 10YR event Inflow = 0.00 cfs @ 14.70 hrs, Volume= 0.001 of Outflow = 0.00 cfs @ 14.75 hrs, Volume= 0.001 af, Atten= 0%, Lag= 2.7 min Discarded = 0.00 cfs @ 14.75 hrs, Volume= 0.001 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Watertown KBS 4-24-14 Type 111 24-hr 10YR Rainfall=4.50" Prepared by Bohler Engineering Printed 6/27/2014 HydroCADO 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Paae 17 Peak Elev= 36.50' @ 14.75 hrs Surf.Area= 344 sf Storage= 0 cf Plug-Flow detention time= 1.5 min calculated for 0.001 of(100% of inflow) Center-of-Mass det. time= 1.5 min ( 1,055.3 - 1,053.8 ) Volume Invert Avail.Storage Storaqe Description #1 36.50' 306 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 36.50 344 0 0 37.00 879 306 306 Device Routinq Invert Outlet Devices #1 Discarded 36.50' 2.410 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.02 cfs @ 14.75 hrs HW=36.50' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.02 cfs) Summary for Pond PD2: Inf. Pond 2 Inflow Area = 0.038 ac, 0.00% Impervious, Inflow Depth = 0.11" for 10YR event Inflow = 0.00 cfs @ 14.70 hrs, Volume= 0.000 of Outflow = 0.00 cfs @ 14.75 hrs, Volume= 0.000 af, Atten= 0%, Lag= 2.7 min Discarded = 0.00 cfs @ 14.75 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Peak Elev= 37.50' @ 14.75 hrs Surf.Area= 169 sf Storage= 0 cf Plug-Flow detention time= 1.5 min calculated for 0.000 of (100% of inflow) Center-of-Mass det. time= 1.5 min ( 1,055.3 - 1,053.8 ) Volume Invert Avail.Storaae Storaqe Description #1 37.50' 147 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation SurF.Area Inc.Store Cum.Store (feet) (sa-ft) (cubic-feet) (cubic-feet)- 37.50 169 0 0 38.00 418 147 147 Device Routinq Invert Outlet Devices #1 Discarded 37.50' 2.410 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.01 cfs @ 14.75 hrs HW=37.50' (Free Discharge) t1=Exfiltration (Exfiltration Controls 0.01 cfs) Watertown KBS 4-24-14 Type ///24-hr 10YR Rainfall=4.50" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 18 Summary for Pond UG: UG system Inflow Area = 0.416 ac, 94.76% Impervious, Inflow Depth = 3.93" for 10YR event Inflow = 1.74 cfs @ 12.08 hrs, Volume= 0.137 of Outflow = 1.62 cfs @ 12.11 hrs, Volume= 0.136 af, Atten= 7%, Lag= 1.8 min Discarded = 0.03 cfs @ 8.14 hrs, Volume= 0.066 of Primary = 1.59 cfs @ 12.11 hrs, Volume= 0.071 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Peak Elev= 36.59' @ 12.11 hrs Surf.Area= 627 sf Storage= 1,091 cf Flood Elev= 38.10' Surf.Area= 627 sf Storage= 1,348 cf Plug-Flow detention time= 109.8 min calculated for 0.136 of(100% of inflow) Center-of-Mass det. time= 109.5 min ( 871.6- 762.2 ) Volume Invert Avail.Storage Storaqe Descriotion #1 34.00' 613 cf 11.00'W x 57.00'L x 3.50'H Prismatoid 2,195 cf Overall - 735 cf Embedded = 1,459 cf x 42.0% Voids #2 34.50' 735 cf StormTech SC-740 x 16 Inside#1 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.121 =45.9 cf Overall Size= 51.0"W x 30.0"H x 7.561 with 0.44' Overlao 1,348 cf Total Available Storage Device Routina Invert Outlet Devices #1 Discarded 34.00' 2.410 in/hr Exfiltration over Surface area #2 Primary 35.80' 12.0" Round Culvert L= 6.0' CMP, projecting, no headwall, Ke= 0.900 Inlet/Outlet Invert= 35.80' /35.60' S= 0.0333 T Cc= 0.900 n= 0.013, Flow Area= 0.79 sf Discarded OutFlow Max=0.03 cfs @ 8.14 hrs HW=34.04' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=1.58 cfs @ 12.11 hrs HW=36.59' (Free Discharge) L2=Culvert (Inlet Controls 1.58 cfs @ 2.39 fps) Watertown KBS 4-24-14 Type/1/24-hr 25YR Rainfall=5.30" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD@ 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Pape 19 Summary for Subcatchment E-1A: On-site to Wells Avenue Drainage System Runoff = 3.19 cfs @ 12.08 hrs, Volume= 0.260 af, Depth= 5.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 26,819 98 Paved parkinq & roofs 26,819 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-1 B: Roof to Wells Avenue Drainage System Runoff = 1.23 cfs @ 12.08 hrs, Volume= 0.100 af, Depth= 5.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 10,350 98 Paved parkinq & roofs 10,350 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-2: To Mount Auburn Street Drainage System Runoff = 0.69 cfs @ 12.08 hrs, Volume= 0.056 af, Depth= 5.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 5,758 98 Paved parkinq & roofs 5,758 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Watertown KBS 4-24-14 Type 111 24-hr 25YR Rainfall=5.30" Prepared by Bohler Engineering Printed 6/27/2014 HydroCADO 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Pave 20 Summary for Subcatchment E-3: To Arlington St Drainage System Runoff = 2.04 cfs @ 12.08 hrs, Volume= 0.166 af, Depth= 5.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 17,143 98 Paved parking & roofs 17,143 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-4: To Southeast Abutter Runoff = 0.34 cfs @ 12.08 hrs, Volume= 0.028 af, Depth= 5.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 2.858 98 Paved parking & roofs 2,858 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-1A: To Wells Ave Runoff = 2.53 cfs @ 12.08 hrs, Volume= 0.191 af, Depth= 4.38" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 20,305 98 Paved parking & roofs 2,425 39 >75% Grass cover. Good, HSG A 22,730 92 Weighted Average 2,425 10.67% Pervious Area 20,305 89.33% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Watertown KBS 4-24-14 Type /// 24-hr 25YR Rainfall=5.30" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Pane 21 Summary for Subcatchment P-1 B: To Wells St Drainage System Runoff = 1.55 cfs @ 12.08 hrs, Volume= 0.126 af, Depth= 5.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 13,000 98 Paved parkinq, HSG A 13,000 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment PAC: Loading Runoff = 0.52 cfs @ 12.09 hrs, Volume= 0.038 af, Depth= 3.85" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 4,190 98 Paved parking & roofs 950 39 >75% Grass cover, Good, HSG A 5,140 87 Weighted Average 950 18.48% Pervious Area 4,190 81.52% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-2: To Mount Auburn St Drainage System Runoff = 0.03 cfs @ 12.09 hrs, Volume= 0.002 af, Depth= 3.75" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 270 98 Paved parking & roofs 67 39 >75% Grass cover, Good. HSG A 337 86 Weighted Average 67 19.88% Pervious Area 270 80.12% Impervious Area Watertown KBS 4-24-14 Type 111 24-hr 25YR Rainfall=5.30" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 22 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-3A: To Arlington St Drainage System Runoff = 1.86 cfs @ 12.08 hrs, Volume= 0.144 af, Depth= 4.72" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 813 39 >75% Grass cover, Good, HSG A 15.192 98 Paved parking, HSG A 16,005 95 Weighted Average 813 5.08% Pervious Area 15,192 94.92% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-313: Landscaped area 1 Runoff = 0.00 cfs @ 12.43 hrs, Volume= 0.001 af, Depth= 0.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 2,907 39 >75% Grass cover. Good, HSG A 2,907 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (_feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, direct Summary for Subcatchment P-3C: Landscaped area 2 Runoff = 0.00 cfs @ 12.43 hrs, Volume= 0.001 af, Depth= 0.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 1,657 39 >75% Grass cover. Good, HSG A 1,657 100.00% Pervious Area Watertown KBS 4-24-14 Type ///24-hr 25YR Rainfall=5.30" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paoe 23 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, direct Summary for Subcatchment P-4: To Southeast Abutter Runoff = 0.07 cfs @ 12.09 hrs, Volume= 0.005 af, Depth= 2.52" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 25YR Rainfall=5.30" Area (sf) CN Description 620 98 Paved parking & roofs 448 39 >75% Grass cover. Good. HSG A 1,068 73 Weighted Average 448 41.95% Pervious Area 620 58.05% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Reach DPE-2: Mount Auburn Drainage System Inflow Area = 0.132 ac,100.00% Impervious, Inflow Depth = 5.06" for 25YR event Inflow = 0.69 cfs @ 12.08 hrs, Volume= 0.056 of Outflow = 0.69 cfs @ 12.08 hrs, Volume= 0.056 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPE-3: Arlington St Drainage System Inflow Area = 0.394 ac,100.00% Impervious, Inflow Depth = 5.06" for 25YR event Inflow = 2.04 cfs @ 12.08 hrs, Volume= 0.166 of Outflow = 2.04 cfs @ 12.08 hrs, Volume= 0.166 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPE-4: Southeast Abutter Inflow Area = 0.066 ac,100.00% Impervious, Inflow Depth = 5.06" for 25YR event Inflow = 0.34 cfs @ 12.08 hrs, Volume= 0.028 of Outflow = 0.34 cfs @ 12.08 hrs, Volume= 0.028 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Watertown KBS 4-24-14 Type 111 24-hr 25YR Rainfall=5.30" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Paae 24 Summary for Reach DPE1: Wells Ave Drainage System Inflow Area = 0.853 ac,100.00% Impervious, Inflow Depth = 5.06" for 25YR event Inflow = 4.43 cfs @ 12.08 hrs, Volume= 0.360 of Outflow = 4.43 cfs @ 12.08 hrs, Volume= 0.360 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-2: Mount Auburn Drainage System Inflow Area = 0.008 ac, 80.12% Impervious, Inflow Depth = 3.75" for 25YR event Inflow = 0.03 cfs @ 12.09 hrs, Volume= 0.002 of Outflow = 0.03 cfs @ 12.09 hrs, Volume= 0.002 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-3: Arlington St Drainage System Inflow Area = 0.367 ac, 94.92% Impervious, Inflow Depth = 4.72" for 25YR event Inflow = 1.86 cfs @ 12.08 hrs, Volume= 0.144 of Outflow = 1.86 cfs @ 12.08 hrs, Volume= 0.144 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-4: Southeast Abutter Inflow Area = 0.025 ac, 58.05% Impervious, Inflow Depth = 2.52" for 25YR event Inflow = 0.07 cfs @ 12.09 hrs, Volume= 0.005 of Outflow = 0.07 cfs @ 12.09 hrs, Volume= 0.005 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP1: Well Ave Drainage System Inflow Area = 0.938 ac, 91.74% Impervious, Inflow Depth = 3.64" for 25YR event Inflow = 4.37 cfs @ 12.10 hrs, Volume= 0.284 of Outflow = 4.37 cfs @ 12.10 hrs, Volume= 0.284 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Pond PD1: Inf. Pond 1 Inflow Area = 0.067 ac, 0.00% Impervious, Inflow Depth = 0.26" for 25YR event Inflow = 0.00 cfs @ 12.43 hrs, Volume= 0.001 of Outflow = 0.00 cfs @ 12.45 hrs, Volume= 0.001 af, Atten= 1%, Lag= 1.6 min Discarded = 0.00 cfs @ 12.45 hrs, Volume= 0.001 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Watertown KBS 4-24-14 Type /// 24-hr 25YR Rainfall=5.30" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Paae 25 Peak Elev= 36.50' @ 12.45 hrs Surf.Area= 345 sf Storage= 0 cf Plug-Flow detention time= 1.5 min calculated for 0.001 of(100% of inflow) Center-of-Mass det. time= 1.5 min ( 992.9- 991.4 ) Volume Invert Avail.Storage Storage Description #1 36.50' 306 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 36.50 344 0 0 37.00 879 306 306 Device Routinq Invert Outlet Devices #1 Discarded 36.50' 2.410 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.02 cfs @ 12.45 hrs HW=36.50' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.02 cfs) Summary for Pond PD2: Inf. Pond 2 Inflow Area = 0.038 ac, 0.00% Impervious, Inflow Depth = 0.26" for 25YR event Inflow = 0.00 cfs @ 12.43 hrs, Volume= 0.001 of Outflow = 0.00 cfs @ 12.45 hrs, Volume= 0.001 af, Atten= 1%, Lag= 1.6 min Discarded = 0.00 cfs @ 12.45 hrs, Volume= 0.001 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Peak Elev= 37.50' @ 12.45 hrs Surf.Area= 170 sf Storage= 0 cf Plug-Flow detention time= 1.5 min calculated for 0.001 of(100% of inflow) Center-of-Mass det. time= 1.5 min ( 992.9 - 991.4 ) Volume Invert Avail.Storage Storaqe Description #1 37.50' 147 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 37.50 169 0 0 38.00 418 147 147 Device Routinq Invert Outlet Devices #1 Discarded 37.50' 2.410 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.01 cfs @ 12.45 hrs HW=37.50' (Free Discharge) t1=Exfiltration (Exfiltration Controls 0.01 cfs) Watertown KBS 4-24-14 Type /// 24-hr 25YR Rainfall=5.30" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Page 26 Summary for Pond UG: UG system Inflow Area = 0.416 ac, 94.76% Impervious, Inflow Depth = 4.72" for 25YR event Inflow = 2.07 cfs @ 12.08 hrs, Volume= 0.164 of Outflow = 1.94 cfs @ 12.11 hrs, Volume= 0.162 af, Atten= 6%, Lag= 1.8 min Discarded = 0.03 cfs @ 7.39 hrs, Volume= 0.068 of Primary = 1.90 cfs @ 12.11 hrs, Volume= 0.094 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Peak Elev= 36.70' @ 12.11 hrs Surf.Area= 627 sf Storage= 1,130 cf Flood Elev= 38.10' Surf.Area= 627 sf Storage= 1,348 cf Plug-Flow detention time= 98.9 min calculated for 0.162 of(99% of inflow) Center-of-Mass det. time= 90.6 min ( 849.7 - 759.1 ) Volume Invert Avail.Storage Storage Description #1 34.00' 613 cf 11.00'W x 57.00'L x 3.50'H Prismatoid 2,195 cf Overall - 735 cf Embedded = 1,459 cf x 42.0% Voids #2 34.50' 735 cf StormTech SC-740 x 16 Inside#1 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L =45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 1,348 cf Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 34.00' 2.410 in/hr Exfiltration over Surface area #2 Primary 35.80' 12.0" Round Culvert L= 6.0' CMP, projecting, no headwall, Ke= 0.900 Inlet/ Outlet Invert= 35.80' / 35.60' S= 0.0333 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf Discarded OutFlow Max=0.03 cfs @ 7.39 hrs HW=34.04' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=1.90 cfs @ 12.11 hrs HW=36.70' (Free Discharge) t-2=Culvert (Inlet Controls 1.90 cfs @ 2.55 fps) Watertown KBS 4-24-14 Type /// 24-hr 100YR Rainfall=6.50" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Pane 27 Summary for Subcatchment E-1A: On-site to Wells Avenue Drainage System Runoff = 3.92 cfs @ 12.08 hrs, Volume= 0.321 af, Depth= 6.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 26,819 98 Paved Darkinq & roofs 26,819 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-1 B: Roof to Wells Avenue Drainage System Runoff = 1.51 cfs @ 12.08 hrs, Volume= 0.124 af, Depth= 6.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 10,350 98 Paved garkinq & roofs 10,350 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-2: To Mount Auburn Street Drainage System Runoff = 0.84 cfs @ 12.08 hrs, Volume= 0.069 af, Depth= 6.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 5,758 98 Paved parkina & roofs 5,758 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Watertown KBS 4-24-14 Type ///24-hr 100YR Rainfall=6.50" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Pace 28 Summary for Subcatchment E-3: To Arlington St Drainage System Runoff = 2.51 cfs @ 12.08 hrs, Volume= 0.205 af, Depth= 6.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 17,143 98 Paved parking & roofs 17,143 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment E-4: To Southeast Abutter Runoff = 0.42 cfs @ 12.08 hrs, Volume= 0.034 af, Depth= 6.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 2,858 98 Paved parkina & roofs 2,858 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (fUft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-1A: To Wells Ave Runoff = 3.17 cfs @ 12.08 hrs, Volume= 0.242 af, Depth= 5.56" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 20,305 98 Paved parking & roofs 2,425 39 >75% Grass cover. Good. HSG A 22,730 92 Weighted Average 2,425 10.67% Pervious Area 20,305 89.33% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (fUsec) (cfs) 6.0 Direct Entry, Watertown KBS 4-24-14 Type ///24-hr 100YR Rainfall=6.50" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paoe 29 Summary for Subcatchment P-1 B: To Wells St Drainage System Runoff = 1.90 cfs @ 12.08 hrs, Volume= 0.156 af, Depth= 6.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 13,000 98 Paved narking. HSG A 13,000 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment PAC: Loading Runoff = 0.67 cfs @ 12.09 hrs, Volume= 0.049 af, Depth= 5.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 4,190 98 Paved parking & roofs 950 39 >75% Grass cover. Good. HSG A 5,140 87 Weighted Average 950 18.48% Pervious Area 4,190 81.52% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-2: To Mount Auburn St Drainage System Runoff = 0.04 cfs @ 12.09 hrs, Volume= 0.003 af, Depth= 4.89" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 270 98 Paved parking & roofs 67 39 >75% Grass cover. Good. HSG A 337 86 Weighted Average 67 19.88% Pervious Area 270 80.12% Impervious Area Watertown KBS 4-24-14 Type ///24-hr 100YR Rainfall=6.50" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paoe 30 Tc Length Slope Velocity Capacity Description (_min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-3A: To Arlington St Drainage System Runoff = 2.30 cfs @ 12.08 hrs, Volume= 0.181 af, Depth= 5.91" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 813 39 >75% Grass cover, Good, HSG A 15.192 98 Paved parking, HSG A 16,005 95 Weighted Average 813 5.08% Pervious Area 15,192 94.92% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment 13-313: Landscaped area 1 Runoff = 0.02 cfs @ 12.30 hrs, Volume= 0.003 af, Depth= 0.60" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 2,907 39 >75% Grass cover, Good, HSG A 2,907 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, direct Summary for Subcatchment P-3C: Landscaped area 2 Runoff = 0.01 cfs @ 12.30 hrs, Volume= 0.002 af, Depth= 0.60" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 1,657 39 >75% Grass cover, Good, HSG A 1,657 100.00% Pervious Area Watertown KBS 4-24-14 Type 111 24-hr 100YR Rainfall=6.50" Prepared by Bohler Engineering Printed 6/27/2014 HydroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 31 Tc Length Slope Velocity Capacity Description (min) (feet) (fUft) (ft/sec) (cfs) 6.0 Direct Entry, direct Summary for Subcatchment P-4: To Southeast Abutter Runoff = 0.10 cfs @ 12.09 hrs, Volume= 0.007 af, Depth= 3.51" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Type III 24-hr 100YR Rainfall=6.50" Area (sf) CN Description 620 98 Paved parking & roofs 448 39 >75% Grass cover. Good. HSG A 1,068 73 Weighted Average 448 41.95% Pervious Area 620 58.05% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Reach DPE-2: Mount Auburn Drainage System Inflow Area = 0.132 ac,100.00% Impervious, Inflow Depth = 6.26" for 100YR event Inflow = 0.84 cfs @ 12.08 hrs, Volume= 0.069 of Outflow = 0.84 cfs @ 12.08 hrs, Volume= 0.069 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPE-3: Arlington St Drainage System Inflow Area = 0.394 ac,100.00% Impervious, Inflow Depth = 6.26" for 100YR event Inflow = 2.51 cfs @ 12.08 hrs, Volume= 0.205 of Outflow = 2.51 cfs @ 12.08 hrs, Volume= 0.205 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPE-4: Southeast Abutter Inflow Area = 0.066 ac,100.00% Impervious, Inflow Depth = 6.26" for 100YR event Inflow = 0.42 cfs @ 12.08 hrs, Volume= 0.034 of Outflow = 0.42 cfs @ 12.08 hrs, Volume= 0.034 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Watertown KBS 4-24-14 Type /// 24-hr 100YR Rainfall=6.50" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HydroCAD Saftware Solutions LLC Pace 32 Summary for Reach DPE1: Wells Ave Drainage System Inflow Area = 0.853 ac,100.00% Impervious, Inflow Depth = 6.26" for 100YR event Inflow = 5.44 cfs @ 12.08 hrs, Volume= 0.445 of Outflow = 5.44 cfs @ 12.08 hrs, Volume= 0.445 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-2: Mount Auburn Drainage System Inflow Area = 0.008 ac, 80.12% Impervious, Inflow Depth = 4.89" for 100YR event Inflow = 0.04 cfs @ 12.09 hrs, Volume= 0.003 of Outflow = 0.04 cfs @ 12.09 hrs, Volume= 0.003 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-3: Arlington St Drainage System Inflow Area = 0.367 ac, 94.92% Impervious, Inflow Depth = 5.91" for 100YR event Inflow = 2.30 cfs @ 12.08 hrs, Volume= 0.181 of Outflow = 2.30 cfs @ 12.08 hrs, Volume= 0.181 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP-4: Southeast Abutter Inflow Area = 0.025 ac, 58.05% Impervious, Inflow Depth = 3.51" for 100YR event Inflow = 0.10 cfs @ 12.09 hrs, Volume= 0.007 of Outflow = 0.10 cfs @ 12.09 hrs, Volume= 0.007 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Reach DPP1: Well Ave Drainage System Inflow Area = 0.938 ac, 91.74% Impervious, Inflow Depth = 4.76" for 100YR event Inflow = 5.43 cfs @ 12.10 hrs, Volume= 0.372 of Outflow = 5.43 cfs @ 12.10 hrs, Volume= 0.372 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Summary for Pond PD1: Inf. Pond 1 Inflow Area = 0.067 ac, 0.00% Impervious, Inflow Depth = 0.60" for 100YR event Inflow = 0.02 cfs @ 12.30 hrs, Volume= 0.003 of Outflow = 0.02 cfs @ 12.32 hrs, Volume= 0.003 af, Atten= 0%, Lag= 1.3 min Discarded = 0.02 cfs @ 12.32 hrs, Volume= 0.003 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Watertown KBS 4-24-14 Type 111 24-hr 100YR Rainfall=6.50" Prepared by Bohler Engineering Printed 6/27/2014 HydroCADO 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Pace 33 Peak Elev= 36.50' @ 12.32 hrs Surf.Area= 349 sf Storage= 2 cf Plug-Flow detention time= 1.5 min calculated for 0.003 of (100% of inflow) Center-of-Mass det. time= 1.5 min ( 944.9- 943.4 ) Volume Invert Avail.Storage Storage Description #1 36.50' 306 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 36.50 344 0 0 37.00 879 306 306 Device Routina Invert Outlet Devices #1 Discarded 36.50' 2.410 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.02 cfs @ 12.32 hrs HW=36.50' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.02 cfs) Summary for Pond PD2: Inf. Pond 2 Inflow Area = 0.038 ac, 0.00% Impervious, Inflow Depth = 0.60" for 100YR event Inflow = 0.01 cfs @ 12.30 hrs, Volume= 0.002 of Outflow = 0.01 cfs @ 12.40 hrs, Volume= 0.002 af, Atten= 8%, Lag= 6.1 min Discarded = 0.01 cfs @ 12.40 hrs, Volume= 0.002 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Peak Elev= 37.51' @ 12.40 hrs Surf.Area= 173 sf Storage= 1 cf Plug-Flow detention time= 1.5 min calculated for 0.002 of(100% of inflow) Center-of-Mass det. time= 1.5 min ( 945.0- 943.4 ) Volume Invert Avail.Storaoe Storaqe Description #1 37.50' 147 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sa-ft) (cubic-feet) (cubic-feet) 37.50 169 0 0 38.00 418 147 147 Device Routina Invert Outlet Devices #1 Discarded 37.50' 2.410 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.01 cfs @ 12.40 hrs HW=37.51' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.01 cfs) Watertown KBS 4-24-14 Type/1/24-hr 100YR Rainfall=6.50" Prepared by Bohler Engineering Printed 6/27/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 34 Summary for Pond UG: UG system Inflow Area = 0.416 ac, 94.76% Impervious, Inflow Depth = 5.90" for 100YR event Inflow = 2.57 cfs @ 12.08 hrs, Volume= 0.205 of Outflow = 2.38 cfs @ 12.12 hrs, Volume= 0.200 af, Atten= 7%, Lag= 2.0 min Discarded = 0.03 cfs @ 6.56 hrs, Volume= 0.070 of Primary = 2.35 cfs @ 12.12 hrs, Volume= 0.130 of Routing by Stor-Ind method, Time Span= 0.00-28.00 hrs, dt= 0.01 hrs Peak Elev= 36.92' @ 12.12 hrs Surf.Area= 627 sf Storage= 1,194 cf Flood Elev= 38.10' Surf.Area= 627 sf Storage= 1,348 cf Plug-Flow detention time= 85.4 min calculated for 0.200 of(98% of inflow) Center-of-Mass det. time= 71.7 min ( 827.2 - 755.5 ) Volume Invert Avail.Storage Storaqe Description #1 34.00' 613 cf 11.00'W x 57.00'L x 3.50'H Prismatoid 2,195 cf Overall - 735 cf Embedded = 1,459 cf x 42.0% Voids #2 34.50' 735 cf StormTech SC-740 x 16 Inside#1 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 1,348 cf Total Available Storage Device Routinq Invert Outlet Devices #1 Discarded 34.00' 2.410 in/hr Exfiltration over Surface area #2 Primary 35.80' 12.0" Round Culvert L= 6.0' CMP, projecting, no headwall, Ke= 0.900 Inlet/ Outlet Invert= 35.80' /35.60' S= 0.0333 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf Discarded OutFlow Max=0.03 cfs @ 6.56 hrs HW=34.04' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=2.34 cfs @ 12.12 hrs HW=36.92' (Free Discharge) L2=Culvert (Inlet Controls 2.34 cfs @ 2.98 fps) Appendix D a� li M r-I O - on LO fu N � _T �• J 3 0 n / F 0 1 � A14 r1 on ty ' ✓ a+CL 0 G i O n G ' cu 4-1 ! 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