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HomeMy WebLinkAboutStormwater Report - 980 OSGOOD STREET 4/24/1996 DRAINAGE ANAL YSIS REPORT PREPARED FOR: .JOHN FERREIRA FEBR U , 1996 ROSERT C. QAL.EY CM. w .31 REVlS'E APR/L 24, /99� Y MERRIMACK ENGINEERING SERVICES, Inc. 66 Park Street Andover, Massachusetts 01810 planners • engineers • surveyors DRAINAGE ANALYSIS FOR THE DESIGN OF THE ON-SITE SUBSURFACE STORMWATER RETENTION AND DETENTION FACILITY AND DETERMINATION OF HYDRAULIC CAPACITY OF THE STATE DRAINAGE SYSTEM NARRATIVE The project site is located at 980 Osgood Street(Route 125) in North Andover, Massachusetts, north of Sutton Street, and east of Old Clark Road. A portion of the existing site is proposed to be further developed. A building addition of 2560 square feet and paved driveway and parking area will be constructed adjacent to the existing North Andover Texaco gasoline and automotive service station, which has been in continuous operation for more than 10 years. PRE-DEVELOPMENT CONDITIONS The area to be developed has been previously altered over these years from its natural state to provide space for storage of vehicles and other related uses consistent with automotive repair and service facilities. Most of the vegetated cover has been stripped. Weeds and scrub growth are prevalent. From the USDA Soils Map, the site is underlain with Paxton Soil which is Hydrologic Soil Group "C", with Seasonal High Water Table at greater than 6 feet depth, and a permeability of soil at less than 0.2"/hour. A test pit was done at the site to confirm this description. The topography of the site and its watershed extends from Old Clark Street toward Route 125, Osgood Street. Refer to the Site Plan for grading. For the drainage analysis, the following criteria is obtained by measurement and calculation. The watershed area is 0.42 acres, that being the limit of work in the area to be within the proposed construction activities. Then, the weighted curve number, using the TR-55 method for drainage analysis, is determined for the pre-development conditions. The wooded areas (CN- 73), grass areas-vegetated (CN= 79), and gravel or disturbed areas (CN= 91) are combined by percentage of total area, to determine "Wt CN": WtCN= 19% @73 +43% @79 + 38% @91 = 82 The Time of Concentration is estimated at 5 minutes. Using the "Hydro CAD" Program for the analysis, the subcatchment hydrographs for the 2 year, 10 year and 100 year storms, where i =3.1, 4.5, and 6.5 inches respectively, per 24 hours, using a Type III statistical storm, are computed and graphically shown herewith. See hydrographs for Subcatchments 1, 2 and 3. POST-DEVELOPMENT CONDITIONS The post development analysis is done by using the same methodology. The curve number is primarily affected due to the addition of impervious surfaces, being the roof and pavement areas as proposed. There will also be a resulting increase in the runoff velocity as well as volume and peak rate of flow due to the development. The WtCN is determined, where the impervious area(CN= 98) will be 66% and wooded area (CN= 73) will be 15% and vegetated areas lawn, landscaped, etc. (CN= 79) will be 18% of the 0.42 acre watershed. The weighted curve number, WtCN is computed: WtCN= 66% @98 + 18% @79 + 16% @73 = 91 The time of concentration is estimated at 5 minutes, along the hydraulic length of the watershed. The subcatchment hydrographs for the 2 year, 10 year and 100 year storms are computer-generated. The difference, or increase, in the peak rate of runoff from pre to post development conditions shall be mitigated on-site by the use of a subsurface retention/detention drainage facility. This facility will be sized to detain the peak rate of runoff for each storm event, as analyzed, such that the rate is reduced to less than predevelopment flows. The facility will be constructed using 36-8' x 4.T precast concrete leaching pits or dry wells, each shall withstand H-20 wheel loading where installation in paved area is necessary and whereby proposed. Refer to site plan and details. r In order to achieve this reduction in the peak rate of runoff, as outlined in the following chart, the subsurface facility will have a 6" outlet pipe which will be connected into the existing on-site drainage system, which has been rerouted to eliminate any stormwater discharge toward and into the Town of North Andover Watershed Protection District surrounding Lake Cochichewick. This rerouting of water from the Watershed District, as directed by the Town of North Andover Planning Board and Department of Public Works, would pose an increase in runoff into the State drainage system within the State Highway Layout of Route 125. However, the proposed subsurface facility will detain the initial intense rainfall from the new project site so as to allow this runoff from the adjacent areas, due to rerouting, to occur without any significant impact upon the hydraulic capacity of the state drainage system. A separate area wide analysis of the state drainage system, using the "Rational Method" for drainage analysis with a 10 year storm event, has been done, as requested by the District 4 Engineering Department, and is included with this report, which will be submitted to the Massachusetts Highway Department for approval and permits. The sizing of the on-site subsurface drainage facility is based on several criteria, including soil permeability, volume/storage capacity, outflow rate control, relative to stormwater inflow rates and volumes, as well as allowable vertical depth of stored water within the facility, as necessary to achieve the desired mitigation rate. The outlet flow control pipe will be 6" ductile iron. This facility will require 36 pits. Refer to the site plan for configuration, elevations, and dimensions, etc. This is the apparent optimum design for mitigation of peak flow as well as providing significant storm water detention to allow the peak flow of the rerouted stormwater to flow into and through the state drainage system virtually unaffected by the runoff from this new site development. SUMMARY CHART OF PEAK FLOW, Qp PRE-D POST-D SUBCAT# SUBCAT# AREA=0.42 AC AREA= 0.42 AC POST-D STORM CN= 82 CN= 91 "POND" # EVENT TC= 5 MIN TC = 5 MIN OUTFLOW 100 yr #1 #11 #1 @1 =65 Qp=220 0p=257 Op = 0.93 10 yr #2 #12 #2 1 =4.5 Qp= 1.32 cfs Qp# 1.69 cfs Op = 0.69 2 yr #3 #13 #3 @ 1 =3.1 Qp=0.73 cfs Qp = 1.07 cfs Qp = 0.48 From the chart above and the hydrography, it is shown the subsurface drainage facility will provide ample and sufficient storage volume for each of the storm events and will provide a delay in the occurrence of the peak outflow rate from this facility into the state drainage system. r PRE- DEVELOPMENT Data for JOHN FERREIRA-DRAINAGE REVISIONS TYPE III 24-HOUR RAINFALL= 3.1 IN Prepared by Merrimack Engineering Services , Inc. 27 Mar 96 HydroCAD 4 51 000899 (c) 1986-1996 Applied Microcomputer Systems SUBCATCHMENT 1 PEAK= .73 CFS @ 12.05 HRS, VOLUME= .05 AF PERCENT CN SCS TR-20 METHOD 19.00 73 WOODS TYPE III 24-HOUR 38.00 91 GRAVEL/DISTURBED AREAS RAINFALL= 3. 1 IN 43.00 79 LAWNS SPAN= 10-20 HRS, dt=.05 HRS 100.00 82 TOTAL AREA = .42 AC Method Comment Tc (min) DIRECT ENTRY 5.0 SUBCATCHMENT 1 RUNOFF .70 .65 AREA= .42 AC 60 Tc= 5 MIN CN= 82 .55 r, .50 SCS TR-20 METHOD LO .45 TYPE III 24-HOUR u .40 RAINFALL= 3, 1 IN .35 3 30 PEAK= .73 CFS E' 12.05 HRS of 25 UOLUME= .05 AF L- .20 . 15 . 10 .05 0.0 C!D — N M V' Ln tD r OD rn 0 TIME (hours) r Data for JOHN FERREIRA-DRAINAGE REVISIONS TYPE III 24-HOUR RAINFALL= 4.5 IN Prepared by Merrimack Engineering Services, Inc. 27 Mar 96 HvdroCAD 4.51 000899 (c) 1986-1996 Applied Microcomputer Systems SUBCATCHMENT 1 PEAK= 1.32 CFS @ 12.05 HRS, VOLUME= .08 AF PERCENT CN SCS TR-20 METHOD 19.00 73 WOODS TYPE III 24-HOUR 38.00 91 GRAVEL/DISTURBED AREAS RAINFALL= 4.5 IN 43.00 79 LAWNS SPAN= 10-20 HRS, dt=.05 HRS 100.00 82 TOTAL AREA = .42 AC Method Comment T (min) DIRECT ENTRY 5.0 SUBCATCHMENT t RUNOFF 1 .3 1 .2 AREA= .42 AC I • I Tc= 5 MIN 1 .0 CN= 82 r, •9 SCS TR-20 METHOD 8 TYPE III 24-HOUR u RAINFALL= 4,5 IN \.r 6 PEAK= 1 ,32 CFS o .5 e 12.05 HRS LL-1 •4 UOLUME= .08 AF 3 .2 . I TIME (hours) Data for JOHN FERREIRA-DRAINAGE REVISIONS Page 1 TYPE III 24-HOUR RAINFALL= 4.5 IN Prepared by Merrimack Engineering Services, Inc. 27 Mar 96 HvdroCAD 4.51 000899—IQ)--13-86-1996 AQQlied Microcomputer Systems SUBCATCHMENT 2 SUBCAT #2 POST-DEVELOPMENT (EXIST) PEAK= 2.48 CFS @ 12.02 HRS, VOLUME= .17 AF PERCENT CN SCS TR-20 METHOD 20.00 73 WOODED & VEGETATED TYPE III 24-HOUR 80.00 98 PAVED- IMPERVIOUS RAINFALL= 4.5 IN 100.00 93 TOTAL AREA = .64 AC SPAN= 10-20 HRS, dt=.l HRS Method ' Comm nt Tc (min) DIRECT ENTRY OVERLAND- SHEET FLOW 5.0 SUBCATCHMENT 2 RUNOFF SUBCAT #2 POST—DEVELOPMENT (EXIST) 2,4 2.2 AREA= ,64 AC Tc= 5 MIN 2.0 CN= 93 1 ,8 j 1 ,6 SCS TR-20 METHOD c+ TYPE III 24-HOUR u 1 '4 RAINFALL= 4,5 IN 1 .2 0 1 0 PEAK= 2.48 CFS C' 12.02 HRS ,8 VOLUME= . 17 AF 6 .4 2 00 rn m TIME (hours) r Data for JOHN FERREIRA-DRAINAGE REVISIONS TYPE III 24-HOUR RAINFALL= 6.5 IN Prepared by Merrimack Engineering Services, Inc. 27 Mar 96 HydroCAD 4.51 000899 (c) 1986-1996 Applied Microcomputer Systems SUBCATCHMENT 1 PEAK= 2.20 CFS @ 12.05 HRS, VOLUME= .14 AF PERCENT CN SCS TR-20 METHOD 19.00 73 WOODS TYPE III 24-HOUR 38.00 91 GRAVEL/DISTURBED AREAS RAINFALL= 6.5 IN 43.00 79 LAWNS SPAN= 10-20 HRS, dt=.05 HRS 100.00 82 TOTAL AREA = .42 AC Method Comment Tc (min) DIRECT ENTRY 5.0 SUBCATCHMENT 1 RUNOFF 2.2 2.0 AREA= .42 AC Tc= 5 MIN $ CN= 82 1 6 SCS TR-20 METHOD 1 .4 TYPE III 24-HOUR U 1 .2 RAINFALL= 6,5 IN 3 1 ,0 PEAK= 2.20 CFS p e C 12.05 HRS J UOLUME= . 14 AF .4 2 TIME (hours) ya, ` lip iii ,�►`�' yF \ I 917 Pre �A'�- D eve- IO P 5,bcatckme nd w •c�� u i�rE.°yc'..vr N! H I 1 Pw / �O • 11•`�J47 -� 1 �/ \� �I)11— •J) G -v march 5, r91 � POST DEVELOPMENT r Data for JOHN FERREIRA-DRAINAGE REVISIONS TYPE III 24-HOUR RAINFALL= 3.1 IN Prepared by Merrimack Engineering Services, Inc. 27 Mar 96 HydroCAD 4 51 000899 (c) 1986-1996 ARolied Microcomputer Systems SUBCATCHMEPIT 1 2 YEAR STORM PEAK= 1.07 CFS @ 12.05 HRS, VOLUME= .07 AF PERCENT CN SCS TR-20 METHOD 66.00 98 PAVEMENT TYPE III 24-HOUR 18.00 79 LAWNS RAINFALL= 3.1 IN 16.00 73 WOODS SPAN= 10-20 HRS, dt=.05 HRS 100.00 91 TOTAL AREA = .42 AC Method Comment Tc (min) DIRECT ENTRY 5.0 SUBCATCHMENT 1 RUNOFF 2 YEAR STORM 1 .0 AREA= .42 AC 9 Tc= 5 MIN CN= 91 .8 SCS TR-20 METHOD 0 .7 TYPE III 24-HOUR u 6 RAINFALL= 3. 1 IN .5 PEAK= 1 .07 CFS e 12.05 HRS � 4 VOLUME= .07 AF LL .3 .2 . 1 0.em t N ;t m m TIME (hours) Data for JOHN FERREIRA-DRAINAGE REVISIONS TYPE III 24-HOUR RAINFALL= 3.1 IN Prepared by Merrimack Engineering Services, Inc. 27 Mar 96 HvdroGAD 4 51 000899 (c) 1986-1996 Applied Microcomputer Systems POND 1 2 YEAR STORM Qin = 1.07 CFS @ 12.05 HRS, VOLUME= .07 AF Qout= .48 CFS @ 12.22 HRS, VOLUME= .07 AF, ATTEN= 55%, LAG= 10.3 MIN ELEVATION AREA INC.STOR CUM.STOR STOR-IND METHOD (FT) (SF) (CF) (CF) PEAK STORAGE = 829 CF 140.9 1500 0 0 PEAK ELEVATION= 141.5 FT 141.4 1500 750 750 FLOOD ELEVATION= 145.2 FT 142.0 1500 900 1650 -START ELEVATION= 140.9 FT 143.7 1550 2592 4242 SPAN= 10-20 HRS, dt=.05 HRS 145.2 50 1200 5442 Tdet= 44.6 MIN ( .07 AF) # ROUTE INVERT OUTLET DEVICES 1 P 140.9' 6" CULVERT n=.013 L=15' S=.02'/ ' Ke=.6 Cc=.9 Cd=.56 POND 1 INFLOW & OUTFLOW 2 YEAR STORM - 1 .0 STOR-IND METHOD g PEAK STOR= 829 CF PEAK ELEU= 141 .5 FT .8 r. 7 Qin= 1 .07 CFS Qout= .48 CFS U .6 LAG= 10.3 MIN U .5 O .4 ! �ti J ! � LL .3 r .2 i . 1 N v in 'n r m rn m TIME (hours) Data for JOHN FERREIRA-DRAINAGE REVISIONS TYPE III 24-HOUR RAINFALL= 4.5 IN Prepared by Merrimack Engineering Services, Inc. 27 Mar 96 HydroCAD 4.51 000899 (c) 1986-1996 AQplied MicrocomQ_uter Systems SUBCATCHMENT 1 10 YEAR STORM PEAK= 1.69 CFS @ 12.05 HRS, VOLUME= .11 AF PERCENT CN SCS TR-20 METHOD 66.00 98 PAVEMENT TYPE III 24-HOUR 18.00 79 LAWNS RAINFALL= 4.5 IN 16.00 73 WOODS SPAN= 10-20 HRS, dt=.05 HRS 100.00 91 TOTAL AREA = .42 AC Method . Comment Tc (min) DIRECT ENTRY 5.0 SUBCATCHMENT I RUNOFF 10 YEAR STORM 1 .6 AREA= .42 AC 1 .5 Tc= 5 MIN 1 ,4 CN= 91 1 .3 _ 1 .2 SCS TR-2e METHOD 1 ' 1 TYPE III 24-HOUR 1 '0 RAINFALL= 4.5 IN U 9 v 8 PEAK= 1 .69 CFS p e 12,05 HRS i .5 VOLUME= . 11 AF 4 .3 .2 "r in I r m M m TIME (hours) Data for JOHN FERREIRA-DRAINAGE REVISIONS TYPE III 24-HOUR RAINFALL= 4.5 IN Prepared by Merrimack Engineering Services, Inc. 27 Mar 96 HydroCAD 4.51 000899 (c) 1986-1996 Applied Microcomputer Systems POND 1 10 YEAR STORM Qin 1.69 CFS @ 12.05 HRS, VOLUME= .11 AF Qout= .69 CFS @ 12.25 HRS, VOLUME= .10 AF, ATTEN= 59%, LAG= 12.0 MIN ELEVATION AREA INC.STOR CUM.STOR STOR-IND METHOD (FT) (SF) (CF) (CF) PEAK STORAGE = 1305 CF 140.9 1500 0 0 PEAK ELEVATION= 141.8 FT 141.4 1500 750 750 FLOOD ELEVATION= 145.2 FT 142.0 1500 900 1650 START ELEVATION= 140.9 FT 143.7 1550 2592 4242 SPAN= 10-20 HRS, dt=.05 HRS 145.2 50 1200 5442 Tdet= 39.6 MIN ( . 1 AF) # ROUTE INVERT OUTLET DEVICES 1 P 140.9' 6" CULVERT n=.013 L=15' S=.02'/' Ke=.6 Cc=.9 Cd=.56 POND 1 INFLOW & OUTFLOW 10 YEAR STORM 1 .6 STOR-IND METHOD 1 .5 PEAK STOR= 1305 CF 1 .4 1 .3 PEAK ELEU= 141 .8 FT _ 1 .2 Gin= 1 ,69 CFS - 1 ' 1 Qout= .69 CFS I .g LAG= 12 MIN v 8 3 .7 0 .6 1 �� 5 1 4 .2 m 01 m TIME (hours) r Data for JOHN FERREIRA-DRAINAGE REVISIONS Page 1 TYPE III 24-HOUR RAINFALL= 4.5 IN Prepared by Merrimack Engineering Services, Inc. 27 Mar 96 HydroCAD 4.51 000899 (c) 1986-1996 Aoolied Microcom utp er Systems SUBCATCHMENT 2 SUBCAT #2 POST-DEVELOPMENT (EXIST) PEAK= 2.48 CFS @ 12.02 HRS, VOLUMc-= .17 AF PERCENT CN SCS TR-20 METHOD 20.00 73 WOODED & VEGETATED TYPE III 24-HOUR 80.00 98 PAVED- IMPERVIOUS RAINFALL= 4.5 IN 100.00 93 TOTAL AREA = .64 AC SPAN= 10-20 HRS, dt=. l HRS Method - Comment T (min) DIRECT ENTRY OVERLAND- SHEET FLOW 5.0 SUBCATCHMENT 2 RUNOFF SUBCAT #2 POST—DEUELOPMENT (EXIST) 2.4 2.2 - AREA= .64 AC Tc= 5 MIN 2.0 CN= 93 1 .8 j 16 SCS TR-20 METHOD TYPE III 24-HOUR U 1 .4 RAINFALL= 4.5 IN " 1 .2 PEAK= 2.48 CFS 0 1 '0 e 12.02 HRS � 8 UOLUME= . 17 AF 6 .4 2 i lint (hours) r Data for JOHN FERREIRA-DRAINAGE REVISIONS TYPE III 24-HOUR RAINFALL= 6.5 IN Prepared by Merrimack Engineering Services, Inc. 27 Mar 96 HvdroCAD 4.51 000899 (c) 1986-1996 ARDlied Microcomputer Systems SUBCATCHMENT 1 PEAK= 2.57 CFS @ 12.05 HRS, VOLUME= . 16 AF PERCENT CN SCS TR-20 METHOD 66.00 98 PAVEMENT TYPE III 24-HOUR 18.00 79 LAWNS RAINFALL= 6.5 IN 16.00 73 WOODS SPAN= 10-20 HRS, dt=.05 HRS 100.00 91 TOTAL AREA = .42 AC Method Comment T (min) DIRECT ENTRY 5.0 SUBCATCHMENT 1 RUNOFF 2.4 AREA= .42 AC 2.2 Tc= 5 MIN 2.0 CN= 91 1 .8 SCS TR-20 METHOD 1 .6 TYPE III 24-HOUR U 1 .4 RAINFALL= 6,5 IN 1 '2 PEAK= 2.57 CFS 0 1 .0 e 12.05 HRS —j ,g VOLUME= . 16 AF LL 6 .4 .2 TIME (hours) Data for JOHN FERREIRA-DRAINAGE REVISIONS TYPE III 24-HOUR RAINFALL= 6.5 IN Prepared by Merrimack Engineering Services, Inc. 27 Mar 96 HvdroCAD 4.51 000899 (c) 1986-1996 ARnlied Microcom I Pr Systpms POND 1 100 YEAR STORM Qin = 2.57 CFS @ 12.05 HRS, VOLUME= .16 AF Qout= .93 CFS @ 12.29 HRS, VOLUME= .16 AF, ATTEN= 64%, LAG= 14.4 MIN ELEVATION AREA INC.STOR CUM.STOR STOR-IND METHOD (FT) (SF) (CF) (CF) PEAK STORAGE = 2057 CF 140.9 1500 0 0 PEAK ELEVATION= 142.3 FT 141.4 1500 750 750 FLOOD ELEVATION= 145.2 FT 142.0 1500 900 1650 START ELEVATION= 140.9 FT 143.,7 1550 2592 4242 SPAN= 10-20 HRS, dt=.05 HRS 145.2 50 1200 5442 Tdet= 37.5 MIN ( .16 AF) _# ROUTE INVERT OUTLET DEVICES 1 P 140.9' 6" CULVERT n=.013 L=15' S=.02'/' Ke=.6 Cc=.9 Cd=.56 POND 1 INFLOW & OUTFLOW 100 YEAR STORM 2.4 STDR-IND METHOD 2.2 PEAK STDR= 2057 CF 2.0 PEAK ELEU= 142.3 FT Qln= 2.57 CFS (4- 1 .6 Qout= .93 CFS U 1 .4 LAG= 14,4 MIN 1 .2 O 1 .0 _j .8 / �\ 0 00 = N d m Ol m TIME (hours) DRAINAGE ANALYSIS NARRATIVE The purpose of this drainage analysis is to determine the amounts and affects of storm run-off to be added to the existing drainage system within Osgood Street (Route 125), in North Andover. The increase in run-off will occur in the upper reach of the drainage watershed due to a proposed redirecting of storm run-off from the existing developed portion of the project site. Currently, the run-off has been collected and piped across Route 125, to open lands which contribute to Lake Cochichewick, the water supply source for the Town of North Andover. As a Condition of Approval of the Site Plan, in which the landowner wishes to build on an addition, the Planning Board is requiring the land owner to redirect this run-off out of the Watershed Protection District due to the concern about a potential negative impact to the water supply source should a gasoline spill or other pollution hazard occur on the property. PROCEDURE FOR DETERMINATION OF PEAK FLOW CALCULATION: Using the Rational method for determining the peak rate of run-off to each catch basin, a 10 year storm design will be used in the calculation: Q = CiA(General Formula) C =Run-off Coefficient of Surface C = 0.2 vegetated, (pervious) C =0.9 paved, roof(impervious) i=Rainfall Intensity, varies as the time of concentrat.. a (refer to I-D-F - rainfall chart) A= area of watershed, in acres Each drainage area to an existing or proposed catch basin or other drainage structure or facility will be determined based upon existing plans and records; as well as field observation and determination. It should be noted that Subcat "A" is omitted as there is a depression at the low point which will collect and retain all of the run-off and provide infiltration. Any overflow will occur well after the peak intensity of the storm, so as not to impact the hydraulic capacity of the piping system during peak rates of run-off. r SUBCAT#1 TO DMH#1 C =20% @0.2+ 80% @0.9 =0.76 Tc = 5 minutes i = 5.3 in/hr A =27,700 sq. ft. = 0.64 ac Q=0.76x5.3 x0.64=2.58 cfs SUBCAT#2 TO DMH#3 C =20% @0.2+ 80% @0.9 =0.76 Tc = 5 minutes i = 5.3 in/hr A =20,000 sq. ft. =0.46 ac Q=0.76x5.3 x0.46 = 1.85 cfs CB #3 to infiltration basin, the calculations indicate and presume no run-off into state drainage system. As this subusrface detention system, as proposed, begins to overflow into the state drainage system, this would occur well beyond the peak period of run-off, thereby not contributing to the "peak" flow. SUBCAT #3 TO DETENTION POND AT CB #6 C = 10% @0.2+ 90% @0.9 =0.83 Tc = 5 minutes i = 5.3 in/hr A = 66,600 sq. ft. = 1.53 ac Q= 0.83 x 5.3 x 1.53 = 6.73 cfs into pond for estimate of pond outflow, use 1.0 cfs @ Tc= 5 min, to account for attenuation of outflow due to ponding. SUBCAT #4 TO CB #6 C = 10% @0.2+ 90% @0.9 =0.83 Tc = 5 minutes i = 5.3 in/hr A = 66,600 sq. ft. =0.15 ac Q=0.83 x5.3 x0.15 = 0.66 cfs SUBCAT #5 TO CB #8 C = 10% @0.2+ 90% @0.9 = 0.83 Tc = 5 minutes i = 5.3 in/hr A = 12,700 sq. ft. =0.29 ac Q = 0.83 x5.3 x0.29 = 1.27 cfs SUBCAT#6 TO CB #9 C = 10% @0.2 + 90% @0.9 = 0.83 Tc = 5 minutes i = 5.3 in/hr A = 10,900 sq. ft. =0.25 ac Q = 0.83 x5.3 x0.25 = 1.10 cfs SUBCAT#7 TO CB #10 C. = 50% @0.2 + 50% @0.9 = 0.55 Tc = 5 minutes i = 5.3 in/hr A = 16,500 sq. ft. = 0.38 ac Q = 0.55 x5.3 x0.38 = 1.11 cfs SUBCAT #8 TO CB #11 C = 10% @0.2 + 90% @0.9 = 0.83 Tc = 5 minutes i = 5.3 in/hr A = 9,000 sq. ft. =0.21 ac Q = 0.83 x5.3 x0.21 = 0.92 cfs SUBCAT #9 TO CB #12 C = 10% @0.2 + 90% @0.9 = 0.83 Tc = 5 minutes i = 5.3 in/hr A = 10,400 sq. ft. =0.24 ac Q =0.83 x5.3 x0.24 = 1.06 cfs DMH*#4 + CB #11 + CB #12 TO DMH#5 SUBCAT#10 TO DMH#7 TO DMH#4 (Beyond the Limit of the Project) C =20% @0.2 + 80% @0.9 = 0.76 Tc = 5 minutes i = 5.3 in/hr A = 35,200 sq. ft. =0.81 ac Q= 0.76x5.3 x0.81 =3.26 cfs T U-) t0 O) to u� �P N LL T N t0 N M > Q- U- O LL N N 00 d N r- (D N �t J M M (D M sY 00 J U- � a � � L M Lo r- aZ J lic";w 00 LL M M M M r to 00 N O O O M I-- to O > a. J LL W r (D (o r N T to N W o r O z Oo w 2 w O0 d N Z _ FL U5 fV (V N N N N in Lo Lo r r T T r r r r r Q w co d N Co Lo Lo co T N M N W o o r o 0 0 0 U O Q U- M M OM M M M M M M co M M co co M co N M M N N t` 1- w W to to to to N V) to to to to to to to to to to 4 to to 4 4 M M J Z Q O Q Q7 O 0) O) tp N W et d M N M M D (M O r OM r*-: M O O 000 O O a r r O O N O O O N N Q w W QZ d Q Ln to to to to to to to to to to (o to to to 0 O to 0 o O to to r r r T T W ~ U O (D (D (D O O (D to r 00 00 T r T (D O (D N T O r T N N N N r (D N N 00 T r r N O O 1� r d p P T r T M T r O O r T T UL a U U w w (D Ln Lo U # O � N r N 00 CD � mmgmmmmmmmmgggmg � � mmm � � � Uj O- ❑ U 0 U U U U U U U U ❑ ❑ ❑ 010101010 U U ❑ ❑ m w _ y �p _ Z r * V) (U4 R �f 00 M # O U �{• T Q 0 m � lip c� m m m �c m m c� m m^ lF T/� 1c. 1c. cncnUUcnU ❑ Ut� Ucn ❑ (n (nUU ❑ ❑ 10-22 Drainage and Erosion Control 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 100 r Fq 2.0 �S 1.5 ss a yFg9S FREQUENCY (YRS. ) L 1.0g9s .9 � •8 Q .7 un .6 L .5 U c .4 , I- Cn Z 2 L1J z 15 J J Q 1 LL Z .09 Q .08 Cr .07 06 .05 .04 03 .02 .01 5 6 7 8 9 10 15 20 30 40 50 60 2 3 4 5 6 8 10 12 18 24 (MINUTES) DU RATION (HOURS) Figure 10-4. Intensity — Duration — Frequency Curve for Boston, MA Drainage and Erosion Control 10.19 Table 10.6 RECOMMENDED RUNOFF COEFFICIENTS (C) FOR RATIONAL METHOD (By Overall Character of Area) Description of Area Runoff Coefficients Business Downtown 0.70 to 0.95 Neighborhood 0.50 to 0.70 Residential Single-Family 0.30 to 0.50 Multi-Family, Detached 0.40 to 0.60 Multi-Family, Attached 0.60 to 0.75 Residential (Suburban) 0.25 to 0.40 Apartment 0.50 to 0.70 Industrial Light 0.50 to 0.80 Heavy 0.60 to 0.90 Parks, Cemeteries 0.10 to 0.25 Playgrounds 0.20 to 0.35 Railroad Yard 0.20 to 0.35 Unimproved 0.10 to 0.30 Woodland 0.15 to 0.25 Cultivated 0.40 to 0.60 Swamp, Marsh 0.10 r dA .��° I I I ( I Q CHART 35 o • 0� AL Ul to I r I n \ tp` 9 I h II'�++ Op k Oj Z I \ 00 ° \ o W V\\ 0'6 0 1 00 05 c5_ 00 OOtr q h NA 1 ` 0 0� It,W m v I 1 .00 C3 p ? . _ � h \ Q v I 1 0 N d 11 1 N it, 1.—. • ! I I O 1 O ° Qb • A O 1 0 ..1....-_--..L.. - tO I i I I I I 'O 000 OO 000 0 ` 08000 00 00000 Tall 9/0 jr U 5d-4 - A - 41100733 PIPE FLOW CHART 12-INCH DIAMETER i O CHART 36 t N s 1 I J o o p b V Y j V i I a 6 p 1 — lo, W ' Ovi ►� ' u W 1 p00 4 0°'� 1 ' ti l I ! I .' P w 0° j I ° ° Op o ` ! I v o � o°o 1' 0° °� O' °° 00 W O ►. p01Ob " b 0° OC N a ! ¢ NNI AN I i j I I iZ i V\ 'W V O I ; C Oa 1 N C 0 ' o i ! ♦ C p �ftu 14 © O I I I i I l V o'bgrp♦p O y 0 0 0 00 0 P � O�O00 O � O 00 00 U O O S/0' u Sd! - ^ - . .1100731 9/0'.ru o x 12, O a b L bl0 zu < Y PIPE FLOW CHART 15-INCH DIAMETER I80 10,000 . CHART 1 168 8,000 EXAMPLE (() (2) (3) 156 6,0100 0.42 inches (3.5 reel) 6. 5,000 0.120 cts 6• 144 5• 4,000 " 4 mw 6. 5. 132 0 test 3,000 (1) 2.5 8.8 5. 4. 120 4• 108 (2) 2.1 7.4 2,000 (3) 2.2 7.7 4, 3. D�SIg�Q '0 in feet 3. Ce 96 1,000 / 3. I0 Ye,42 800 84 E?U[ S' - i— T /'V 500 j/ 2' SOCCHARG. 72 400 / e 2. Coetlo�Tryr✓ W �� U 300 = 1.5 1.5 ({fie 0:(J{6 Z 60 v 200 / 1.5 04W>= _ J?fA0 f- v_ a w 48 /w 100 / 1QF.AD: 1-?-0 > / a 80 / _ 1.Z0 J v /2 60 a L0 I.0 W U. 0 50 HW SCALE ENTRANCE ° Lo 40 D / TYPE taJ w 9 1, 36 30 (1) Square edge with 4111! 9 9 33 headwall ° a a 20 121 Groove end wifh W 30 headwall = .8 8 (3) / Groove end 8 27 pro)eeting 10 24 ® .7 7 7— 6 To use scale (2) or (3) project 2 I 5 / horizontally to scale (1),then 4 use straight inclined line through 0 and 0 scales.or reverse as 6 .6 3 illustrated. .8 18 2 �. 15 I.0 5 .5 12 HEADWATER DEPTH FOR HEADWATER SCALES 2a3 CONCRETE PIPE CULVERTS BUREAU OF PUBLIC ROAOS JAN. 1963 REVISED MAY 1964 WITH INLET CONTROL 181 U-1- * UNITED STATES COMMC DEPARTMENT OF THE INTERIOR ,, ,4 °T GEOLOGICAL SURVEY D` �1°��' 300 32��E 125 ,�2,7 Ml.TO .MASS.97 329 S' —330 42'45' 4QH �z rr _ w °Hill - n Tree _ . Airw 1734000m N ;{�f �1, - `° \� Chadw ck� ' W ide \ m Pon ' /. Athletic Field r ��-s�'•- � ,t7>,�>'!J�� \. -�`•� •` III � a �/J; \-.�i 1, � 4733 \\ N ter Ij 4732 o;. gµ 'F;'i �. �� 88x 1 �,, _-}/-- _ I� SAO E 151 6 F f _ 178 1 v 1� 'Ll l��'1 F _ _ �, 150 RE CEO -� _ �\�1 �.� _ Hoveys \\I l/AIR POR �� L' ✓ —� _ �r — Pond 5 FqH t,4 ��•• \� - } •1\ i- J —rc't�iZ.E1(�QS / ( � �1 prep p 8 o ono `� 133 ST. 4131 \ � ,.\\ R -_ :\ a rY q q POND 7 a 1 ^O 125 �to 133 �t 1 �`�j 154 p° \sr: _ ��;. �\.• � ,�, � �� /J� j/�`\yI \ .�� � Hit,\� &� RU ell�Hill,�• m•• 166 Sch 4;30 ..� 1� 1.�., .=o i , —'`�`\ .195 X25 .�" • 7 — ~� _ �, �•- 0ln- 150 cl Qo 291, u�ELL �o 72�G: v1 l 4. °p0 L r • ���� 'mod- ° f;UZ � °•i Y�2WW l yaVUN f ?� '' Q <,�� <v Cv a C o n o IW I Fo i IAJ ` I � F_p I �v�'�-:� _ =�ttpp -� � � pew t.� •, t ,� c !7 �0Q \1 � 1- � �4 � - CS '� !}.�,J V 4! L m� 7 •� �K�� � J l 1� , a? \ �V \'� � � h\ ��' VZ;aT\ F s •� ��; . O0. I r 7 �tT ���- ac I I $QV S r na I o '' °�' �•��3b y�� nos � \ � "� i� ' ,2' + �, �:� �, � €' I i. lb v - m w �� n►7 a , • � oe'�� o4oc .°z r „=�°ice°- �Z � �0�, 1cl fto J 'O OL wry � tam' V \ 1V Jrj '°pc t7..\ h J I � 3