SITE PLAN REVIEW APPLICATION AND STORMWATER REPORT SUBMITTED TO TOWN OF HINGHAM PLANNING BOARD

Proposed Residential Redevelopment

40 Harbor View Drive Hingham, Massachusetts

APPLICANT:

Adam Fleury

APF Development Group, LLC.

213 Wompatuck Road

Hingham, MA 02043

SUBMITTED TO:

Town of Hingham

Planning Board

210 Central Street

Hingham, MA 02043

PREPARED BY:

Cavanaro Consulting, Inc.

687 Main Street

Norwell, MA 02061

Table of Contents

Title Section Site Plan Review Narrative and Compliance with I Stormwater Management Standards Construction Period and Long Term Pollution Prevention II and Erosion and Sedimentation Control Illicit Discharge Statement Figures III Figure 1 – MassGIS Oliver Map Figure 2 – FIRM Flood Map Figure 3 – Hingham GIS Drainage Calculations and Supplemental Drainage Information IV Locus Deed V Easement Statement Filing Fee and Peer Review Deposit Site Plan VI

SECTION I

SITE PLAN REVIEW NARRATIVE AND COMPLIANCE WITH

STORMWATER MANAGEMENT STANDARDS

SITE PLAN REVIEW NARRATIVE

The locus property is located at 40 Harbor View Drive and it is approximately 20,899 square feet. The site is not located within any Flood Plain nor are there any wetlands within 100’ of the property. The lot has been developed as a single family residential property with an attached garage and paved driveways serving the dwelling and garage. The dwelling is connected to public water and sewerage. The yards consist primarily of lawn with some areas of landscape. A wooded area borders the side and rear yards. The topography of the lot slopes in a westerly direction toward the two rear property boundaries. NRCS Soil Survey describes the underlying soils as C soils. The project originally consisted of razing the existing dwelling and attached garage and replacing it with a new larger dwelling with attached garage. During the construction of the dwelling additional walls and landscaping were constructed in the rear yard. This additional disturbance of slopes greater than than 10% triggered a Site Plan review per Section IV-B.6.b of the Town of Hingham Zoning Bylaw. Two new subsurface infiltration systems are proposed to be installed in the rear yard to control stormwater runoff. A silt fence will remain installed and maintained during construction.

Compliance with Stormwater Management Standards: The proposed project complies with the Stormwater Management Standards to the maximum extent practicable as follows:

Standard 1: No New Stormwater Conveyances of Untreated Stormwater or Erosion Offsite There will be no new stormwater conveyances of untreated stormwater since a reduction in pavement is being proposed . Post construction potential for erosion will be reduced by reducing peak rate of runoff during the 2 year and 10 year design storm events.

Standard 2: Peak Rate Attenuation Peak rate of runoff will be reduced during the 2 year and 10 year design storm events and will be matched during the 100 year storm event.

Standard 3: Recharge and Discharge Volume Recharge is required follows: Existing Impervious Area = 2,769 ft2 Proposed Impervious Area =4,688 ft2 Increase impervious = 1,919 s.f. (0.25”/12x1,919 SF) = 40 CF The storage capacity of the subsurface infiltration systems is 304 + 237 = 541 CF below the elevation of the outlets. Therefore, the recharge requirement is met.

Standard 4: Water Quality As shown on the accompanying table 80% of the Total Suspended Solids (TSS) has been removed through the use of an aggressive driveway sweeping program and an infiltration trench. See attached worksheet. Existing Pavement Area = 1,157 ft2 Proposed paved area = 1,470 ft2 Total Increase in Impervious Area = 313 ft2 Non-Critical area requires 0.5 inches over new pavement: (0.5”/12”per ft)(313 ft2) = 13 ft3 A Stone infiltration trench will line a portion of the proposed paved driveway: 30’ = 30 ft X 1.0’ width x 1.5’ depth X 40% voids = 18 ft3

13 ft3 required < 18 ft3 proposed, therefore ok.

Standard 5: Land Uses with Higher Pollutant Loads (LUHPPLs) The use of the site as a residential lot does not constitute a higher potential pollutant load use. Thus, Standard 5 does not pertain to this project.

Standard 6: Critical Areas The locus site is not located within a critical area as can be seen on the attached MassGIS Oliver map.

Standard 7: Redevelopment This project is considered redevelopment.

Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control The Operation and Maintenance Plan included with this submittal will ensure proper maintenance of the proposed pollution, erosion and sedimentation measures proposed during construction.

Standard 9: Long Term Operation and Maintenance Plan The Long Term Operation and Maintenance Plan is included within the Operation and Maintenance Plan enclosed in this submittal to ensure the proposed drainage improvements are maintained as intended.

Standard 10: Prohibition of Illicit Discharges Routine visual inspections are scheduled as part of the Operations and Maintenance Plan to prevent illicit discharges into the stormwater system. Furthermore, an Illicit Compliance Statement is included in this submittal.

Improvement Over Existing Conditions The proposed residential redevelopment project is an improvement over existing conditions because it reduces peak rate of runoff during the most frequent 2 year and 10 year design storm events.

SECTION II

CONSTRUCTION PERIOD AND LONG TERM POLLUTION PREVENTION AND EROSION AND SEDIMENTATION CONTROL

ILLICIT DISCHARGE STATEMENT

Stormwater Operation and Maintenance Plan and Illicit Discharge Statement

Proposed Residential Redevelopment

40 Harbor View Drive – Hingham, MA 02043 Stormwater Management System’s Owner: APF Developement

System Owner’s Address: 213 Wompatuck Road, Hingham, MA 02043 Party responsible for Operations and Maintenance: Owners of 40 Harbor View Drive

It is most important for a drainage system to be maintained in order for it to work properly. The following is an Operation and Maintenance plan to upkeep the existing non-structural and structural best performance practices as outlined in the Massachusetts Department of Environmental Protection’s Stormwater Management Policy. Operation and Maintenance Plan and Construction Sequencing during Construction: 1) Sediment and Erosion Control Prior to any construction or disturbance, all proposed erosion and sediment control shall be installed. A silt fence shall be installed along the side and rear property boundaries as shown in the Site Plan submitted to the Planning Board. Sedimentation control maintenance:

Silt fences shall be inspected at least once a week and after each rainfall event. Make any required repairs immediately. Repair scoured areas on the back side of fence at this time to prevent future problems.

Should the fabric of the silt fence collapse, tear, decompose or otherwise become

ineffective, replace it within 24 hours of discovery.

Remove silt deposits once they reach 20-30 percent of the height of the silt fence to provide adequate storage volume for the next rain event and to reduce pressure on the silt fence. Care should be taken to avoid undermining the fence during cleanout process.

Silt fences are to be removed upon stabilization of the contributing drainage area.

Accumulated sediment may be spread to form a surface for turf or other vegetation establishment, or disposed of elsewhere. The area should be reshaped to permit natural drainage.

2) Infiltration System All infiltration areas shall be excavated and installed after the construction of the foundation systems. No heavy equipment shall traverse the proposed infiltration areas after installation. Per MA DEP Stormwater Guidelines the following work shall be done to stabilize the site prior to installing the subsurface structures:

- Do not allow runoff from any disturbed areas on the site to flow to the subsurface structures. - Rope off the area where the subsurface structures are to be placed. - Accomplish any required excavation with equipment placed just outside the area. If the size of the area intended for exfiltration is too large to accommodate this approach, use trucks with low-pressure tires to minimize compaction. Do not allow any other vehicles within the area to be excavated. - Keep the area above and immediately surrounding the subsurface system roped off to all construction vehicles until the final top surface is installed. - At no time shall the area for the infiltration system be used as a temporary sediment basin. Stockpiles shall be placed away from the subsurface infiltration system and sedimentation fences shall be placed around the perimeter of the infiltration area to prevent the accumulation of sediment within the native soils. 3) Upon completion of construction and permanent stabilization of all disturbed areas the erosion and sediment control may be removed. Operation and Maintenance Plan After Construction: Subsurface Infiltration System: Inspect inspection port at least quarterly and after every major storm event during the first year. Inspections after every major storm event shall take notice of any water standing after 72 hours after the storm ended. After the first year, inspections must be done at least twice yearly. Remove any debris or sediment within reach that may be clogging the system. Roof Drain cleaning: All roof drains shall be cleaned and inspected in late winter or early spring after the snow melts. Inspections should include the gutters, downspouts and all accessible piping. Snow Management

Any snow and ice buildup on the proposed roof drains will be removed in a timely fashion. Estimated Operation and Maintenance Budget: Maintenance cost will be approximately $200.00 per year.

Illicit Discharges: At no time will the owner or any other individual utilize the stormwater management system for any purpose other than its intended use. The stormwater management system as shown on the attached site plan at no time shall receive discharges other than stormwater, this includes “wastewater discharges and discharges of stormwater contaminated by contact with process wastes, raw materials, raw materials, toxic pollutants, hazardous substances, oil or grease.” __________________________ __________________________ Property Owner (Signature) Property Owner (Print)

SECTION III

FIGURES

National Flood Hazard Layer FIRMette

0 500 1,000 1,500 2,000250Feet

Ü

SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT

SPECIAL FLOODHAZARD AREAS

Without Base Flood Elevation (BFE)Zone A, V, A99

With BFE or DepthZone AE, AO, AH, VE, AR

Regulatory Floodway

0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mileZone X

Future Conditions 1% AnnualChance Flood HazardZone X

Area with Reduced Flood Risk due toLevee. See Notes.Zone X

Area with Flood Risk due to LeveeZone D

NO SCREENArea of Minimal Flood HazardZone X

Area of Undetermined Flood HazardZone D

Channel, Culvert, or Storm Sewer

Levee, Dike, or Floodwall

Cross Sections with 1% Annual Chance17.5 Water Surface Elevation

Coastal Transect

Coastal Transect BaselineProfile BaselineHydrographic Feature

Base Flood Elevation Line (BFE)

Effective LOMRs

Limit of StudyJurisdiction Boundary

Digital Data Available

No Digital Data Available

Unmapped

This map complies with FEMA's standards for the use ofdigital flood maps if it is not void as described below.The basemap shown complies with FEMA's basemapaccuracy standards

The flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 4/7/2021 at 12:32 PM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time.

This map image is void if the one or more of the following mapelements do not appear: basemap imagery, flood zone labels,legend, scale bar, map creation date, community identifiers,FIRM panel number, and FIRM effective date. Map images forunmapped and unmodernized areas cannot be used forregulatory purposes.

Legend

OTHER AREAS OFFLOOD HAZARD

OTHER AREAS

GENERALSTRUCTURES

OTHERFEATURES

MAP PANELS

8

B20.2

The pin displayed on the map is an approximatepoint selected by the user and does not representan authoritative property location.

1:6,000

70°55'2"W 42°15'5"N

70°54'24"W 42°14'39"N

Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020

USGSFax: 781.659.8186

687 MAIN STREET

Phone: 781.659.8187

P.O. BOX 5175

Cavanaro Consulting

Norwell, Massachusetts 02061

PREPARED FOR:

APF DEVELOPMENT GROUP LLC

40 HARBOR VIEW DRIVE

HINGHAM, MA 02043

LOCUS

SECTION IV

DRAINAGE CALCULATIONS & SUPPLEMENTAL DRAINAGE INFORMATION

1.0 METHODOLOGY The adequacy of the proposed drainage structures and their ability to function properly were analyzed to minimize detrimental effects due to stormwater conditions. The impacts of storm water are mitigated through several mechanisms such as infiltration, transportation and evaporation. The remaining runoff was quantified through developed and accepted methods.

2.0 OVERVIEW Cavanaro Consulting, Inc. (CC) has analyzed the existing conditions at the site utilizing the HydroCad Storm water modeling program. Storm rainfall, run-off curve numbers, and other site characteristics are input into the program. The results of calculations are output into tables and graphs for each area and control structure.

3.0 DESIGN STORMS CC has computed stormwater run-off calculations for the proposed site, for a 2, 10 and 100 year, 24-hour event. The intensity of these rain events is 3.2”, 4.65” and 6.8” respectively.

4.0 DRAINAGE ANALYSIS The following is the summary of the HydroCAD analysis: To Rear Property Boundaries Storm Existing Post-development

Conditions Conditions 2–Year-24Hour (3.2”) 0.61 cfs 0.044 af 0.55 cfs 0.040 af 10–Year-24Hour (4.65”) 1.26 cfs 0.087 af 1.11 cfs 0.084 af 100–Year-24Hour (6.8”) 2.32 cfs 0.159 af 2.32 cfs 0.158 af

SUPPLEMENTAL INFORMATION

E1

Exist. Cond. 2019

P1

Proposed Remainder

P2

Roof / Driveway

P4

Portion Roof

1R

Rear Yard

2R

Rear Yard

1P

17 x 18 No. 1

2P

17 x 18 No. 2

Routing Diagram for 40 Harbor View 2021Prepared by Cavanaro Consulting, Printed 4/1/2021

HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Subcat Reach Pond Link

Type III 24-hr 2 Year Event Rainfall=3.20"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 2HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Time span=0.00-30.00 hrs, dt=0.01 hrs, 3001 pointsRunoff by SCS TR-20 method, UH=SCS, Weighted-CN

Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method

Runoff Area=20,899 sf 13.25% Impervious Runoff Depth=1.09"Subcatchment E1: Exist. Cond. 2019 Tc=5.0 min CN=75 Runoff=0.61 cfs 0.044 af

Runoff Area=17,747 sf 8.65% Impervious Runoff Depth=1.15"Subcatchment P1: Proposed Remainder Tc=5.0 min CN=76 Runoff=0.55 cfs 0.039 af

Runoff Area=1,744 sf 100.00% Impervious Runoff Depth=2.97"Subcatchment P2: Roof / Driveway Tc=5.0 min CN=98 Runoff=0.13 cfs 0.010 af

Runoff Area=1,408 sf 100.00% Impervious Runoff Depth=2.97"Subcatchment P4: Portion Roof Tc=5.0 min CN=98 Runoff=0.10 cfs 0.008 af

Inflow=0.61 cfs 0.044 afReach 1R: Rear Yard Outflow=0.61 cfs 0.044 af

Inflow=0.55 cfs 0.040 afReach 2R: Rear Yard Outflow=0.55 cfs 0.040 af

Peak Elev=82.73' Storage=272 cf Inflow=0.13 cfs 0.010 afPond 1P: 17 x 18 No. 1 Discarded=0.00 cfs 0.005 af Primary=0.00 cfs 0.001 af Outflow=0.01 cfs 0.005 af

Peak Elev=89.52' Storage=222 cf Inflow=0.10 cfs 0.008 afPond 2P: 17 x 18 No. 2 Discarded=0.00 cfs 0.005 af Primary=0.00 cfs 0.000 af Outflow=0.00 cfs 0.005 af

Total Runoff Area = 0.960 ac Runoff Volume = 0.101 af Average Runoff Depth = 1.26"82.16% Pervious = 0.788 ac 17.84% Impervious = 0.171 ac

Type III 24-hr 2 Year Event Rainfall=3.20"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 3HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Summary for Subcatchment E1: Exist. Cond. 2019

Runoff = 0.61 cfs @ 12.08 hrs, Volume= 0.044 af, Depth= 1.09"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 2 Year Event Rainfall=3.20"

Area (sf) CN Description

1,157 98 Paved parking, HSG C1,075 98 Roofs, HSG C

* 537 98 other impervious8,839 74 >75% Grass cover, Good, HSG C9,291 70 Woods, Good, HSG C

20,899 75 Weighted Average18,130 86.75% Pervious Area2,769 13.25% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Subcatchment P1: Proposed Remainder

Runoff = 0.55 cfs @ 12.08 hrs, Volume= 0.039 af, Depth= 1.15"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 2 Year Event Rainfall=3.20"

Area (sf) CN Description

603 98 Paved parking, HSG C* 130 98 Roofs, HSG C - Porch - Front* 803 98 other impervous

14,386 74 >75% Grass cover, Good, HSG C1,825 70 Woods, Good, HSG C

17,747 76 Weighted Average16,211 91.35% Pervious Area1,536 8.65% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Subcatchment P2: Roof / Driveway

Runoff = 0.13 cfs @ 12.07 hrs, Volume= 0.010 af, Depth= 2.97"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 2 Year Event Rainfall=3.20"

Type III 24-hr 2 Year Event Rainfall=3.20"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 4HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Area (sf) CN Description

* 877 98 Roof* 867 98 Driveway

1,744 98 Weighted Average1,744 100.00% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Subcatchment P4: Portion Roof

Runoff = 0.10 cfs @ 12.07 hrs, Volume= 0.008 af, Depth= 2.97"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 2 Year Event Rainfall=3.20"

Area (sf) CN Description

* 1,408 98 Roof

1,408 100.00% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Reach 1R: Rear Yard

Inflow Area = 0.480 ac, 13.25% Impervious, Inflow Depth = 1.09" for 2 Year Event eventInflow = 0.61 cfs @ 12.08 hrs, Volume= 0.044 afOutflow = 0.61 cfs @ 12.08 hrs, Volume= 0.044 af, Atten= 0%, Lag= 0.0 min

Routing by Stor-Ind+Trans method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs

Summary for Reach 2R: Rear Yard

Inflow Area = 0.480 ac, 22.43% Impervious, Inflow Depth = 0.99" for 2 Year Event eventInflow = 0.55 cfs @ 12.08 hrs, Volume= 0.040 afOutflow = 0.55 cfs @ 12.08 hrs, Volume= 0.040 af, Atten= 0%, Lag= 0.0 min

Routing by Stor-Ind+Trans method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs

Summary for Pond 1P: 17 x 18 No. 1

Inflow Area = 0.040 ac,100.00% Impervious, Inflow Depth = 2.97" for 2 Year Event eventInflow = 0.13 cfs @ 12.07 hrs, Volume= 0.010 afOutflow = 0.01 cfs @ 14.43 hrs, Volume= 0.005 af, Atten= 96%, Lag= 141.5 minDiscarded = 0.00 cfs @ 14.43 hrs, Volume= 0.005 afPrimary = 0.00 cfs @ 14.43 hrs, Volume= 0.001 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs

Type III 24-hr 2 Year Event Rainfall=3.20"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 5HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Peak Elev= 82.73' @ 14.43 hrs Surf.Area= 306 sf Storage= 272 cf

Plug-Flow detention time= 413.1 min calculated for 0.005 af (55% of inflow)Center-of-Mass det. time= 297.2 min ( 1,052.7 - 755.5 )

Volume Invert Avail.Storage Storage Description

#1 81.20' 189 cf Custom Stage Data (Irregular) Listed below (Recalc)612 cf Overall - 140 cf Embedded = 472 cf x 40.0% Voids

#2 81.70' 140 cf Cultec C-100 x 10 Inside #1Effective Size= 32.1"W x 12.0"H => 1.86 sf x 7.50'L = 14.0 cfOverall Size= 36.0"W x 12.5"H x 8.00'L with 0.50' Overlap

329 cf Total Available Storage

Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area(feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft)

81.20 306 70.0 0 0 30683.20 306 70.0 612 612 446

Device Routing Invert Outlet Devices

#1 Primary 82.70' 4.0" Vert. Orifice/Grate C= 0.600 #2 Discarded 81.20' 0.270 in/hr Exfiltration over Wetted area

Discarded OutFlow Max=0.00 cfs @ 14.43 hrs HW=82.73' (Free Discharge)2=Exfiltration (Exfiltration Controls 0.00 cfs)

Primary OutFlow Max=0.00 cfs @ 14.43 hrs HW=82.73' (Free Discharge)1=Orifice/Grate (Orifice Controls 0.00 cfs @ 0.63 fps)

Summary for Pond 2P: 17 x 18 No. 2

Inflow Area = 0.032 ac,100.00% Impervious, Inflow Depth = 2.97" for 2 Year Event eventInflow = 0.10 cfs @ 12.07 hrs, Volume= 0.008 afOutflow = 0.00 cfs @ 16.57 hrs, Volume= 0.005 af, Atten= 98%, Lag= 269.8 minDiscarded = 0.00 cfs @ 16.57 hrs, Volume= 0.005 afPrimary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsPeak Elev= 89.52' @ 16.57 hrs Surf.Area= 306 sf Storage= 222 cf

Plug-Flow detention time= 431.0 min calculated for 0.005 af (58% of inflow)Center-of-Mass det. time= 320.5 min ( 1,075.9 - 755.5 )

Volume Invert Avail.Storage Storage Description

#1 88.30' 189 cf Custom Stage Data (Irregular) Listed below (Recalc)612 cf Overall - 140 cf Embedded = 472 cf x 40.0% Voids

#2 88.80' 140 cf Cultec C-100 x 10 Inside #1Effective Size= 32.1"W x 12.0"H => 1.86 sf x 7.50'L = 14.0 cfOverall Size= 36.0"W x 12.5"H x 8.00'L with 0.50' Overlap

329 cf Total Available Storage

Type III 24-hr 2 Year Event Rainfall=3.20"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 6HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area(feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft)

88.30 306 70.0 0 0 30690.30 306 70.0 612 612 446

Device Routing Invert Outlet Devices

#1 Primary 89.70' 3.0" Vert. Orifice/Grate C= 0.600 #2 Discarded 88.30' 0.270 in/hr Exfiltration over Wetted area

Discarded OutFlow Max=0.00 cfs @ 16.57 hrs HW=89.52' (Free Discharge)2=Exfiltration (Exfiltration Controls 0.00 cfs)

Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=88.30' (Free Discharge)1=Orifice/Grate ( Controls 0.00 cfs)

Type III 24-hr 10 Year Event Rainfall=4.65"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 7HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Time span=0.00-30.00 hrs, dt=0.01 hrs, 3001 pointsRunoff by SCS TR-20 method, UH=SCS, Weighted-CN

Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method

Runoff Area=20,899 sf 13.25% Impervious Runoff Depth=2.17"Subcatchment E1: Exist. Cond. 2019 Tc=5.0 min CN=75 Runoff=1.26 cfs 0.087 af

Runoff Area=17,747 sf 8.65% Impervious Runoff Depth=2.25"Subcatchment P1: Proposed Remainder Tc=5.0 min CN=76 Runoff=1.11 cfs 0.076 af

Runoff Area=1,744 sf 100.00% Impervious Runoff Depth=4.41"Subcatchment P2: Roof / Driveway Tc=5.0 min CN=98 Runoff=0.19 cfs 0.015 af

Runoff Area=1,408 sf 100.00% Impervious Runoff Depth=4.41"Subcatchment P4: Portion Roof Tc=5.0 min CN=98 Runoff=0.15 cfs 0.012 af

Inflow=1.26 cfs 0.087 afReach 1R: Rear Yard Outflow=1.26 cfs 0.087 af

Inflow=1.11 cfs 0.084 afReach 2R: Rear Yard Outflow=1.11 cfs 0.084 af

Peak Elev=82.89' Storage=291 cf Inflow=0.19 cfs 0.015 afPond 1P: 17 x 18 No. 1 Discarded=0.00 cfs 0.005 af Primary=0.08 cfs 0.005 af Outflow=0.08 cfs 0.010 af

Peak Elev=89.82' Storage=270 cf Inflow=0.15 cfs 0.012 afPond 2P: 17 x 18 No. 2 Discarded=0.00 cfs 0.005 af Primary=0.03 cfs 0.002 af Outflow=0.03 cfs 0.008 af

Total Runoff Area = 0.960 ac Runoff Volume = 0.190 af Average Runoff Depth = 2.37"82.16% Pervious = 0.788 ac 17.84% Impervious = 0.171 ac

Type III 24-hr 10 Year Event Rainfall=4.65"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 8HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Summary for Subcatchment E1: Exist. Cond. 2019

Runoff = 1.26 cfs @ 12.08 hrs, Volume= 0.087 af, Depth= 2.17"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 10 Year Event Rainfall=4.65"

Area (sf) CN Description

1,157 98 Paved parking, HSG C1,075 98 Roofs, HSG C

* 537 98 other impervious8,839 74 >75% Grass cover, Good, HSG C9,291 70 Woods, Good, HSG C

20,899 75 Weighted Average18,130 86.75% Pervious Area2,769 13.25% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Subcatchment P1: Proposed Remainder

Runoff = 1.11 cfs @ 12.08 hrs, Volume= 0.076 af, Depth= 2.25"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 10 Year Event Rainfall=4.65"

Area (sf) CN Description

603 98 Paved parking, HSG C* 130 98 Roofs, HSG C - Porch - Front* 803 98 other impervous

14,386 74 >75% Grass cover, Good, HSG C1,825 70 Woods, Good, HSG C

17,747 76 Weighted Average16,211 91.35% Pervious Area1,536 8.65% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Subcatchment P2: Roof / Driveway

Runoff = 0.19 cfs @ 12.07 hrs, Volume= 0.015 af, Depth= 4.41"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 10 Year Event Rainfall=4.65"

Type III 24-hr 10 Year Event Rainfall=4.65"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 9HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Area (sf) CN Description

* 877 98 Roof* 867 98 Driveway

1,744 98 Weighted Average1,744 100.00% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Subcatchment P4: Portion Roof

Runoff = 0.15 cfs @ 12.07 hrs, Volume= 0.012 af, Depth= 4.41"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 10 Year Event Rainfall=4.65"

Area (sf) CN Description

* 1,408 98 Roof

1,408 100.00% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Reach 1R: Rear Yard

Inflow Area = 0.480 ac, 13.25% Impervious, Inflow Depth = 2.17" for 10 Year Event eventInflow = 1.26 cfs @ 12.08 hrs, Volume= 0.087 afOutflow = 1.26 cfs @ 12.08 hrs, Volume= 0.087 af, Atten= 0%, Lag= 0.0 min

Routing by Stor-Ind+Trans method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs

Summary for Reach 2R: Rear Yard

Inflow Area = 0.480 ac, 22.43% Impervious, Inflow Depth = 2.09" for 10 Year Event eventInflow = 1.11 cfs @ 12.08 hrs, Volume= 0.084 afOutflow = 1.11 cfs @ 12.08 hrs, Volume= 0.084 af, Atten= 0%, Lag= 0.0 min

Routing by Stor-Ind+Trans method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs

Summary for Pond 1P: 17 x 18 No. 1

Inflow Area = 0.040 ac,100.00% Impervious, Inflow Depth = 4.41" for 10 Year Event eventInflow = 0.19 cfs @ 12.07 hrs, Volume= 0.015 afOutflow = 0.08 cfs @ 12.24 hrs, Volume= 0.010 af, Atten= 58%, Lag= 10.4 minDiscarded = 0.00 cfs @ 12.24 hrs, Volume= 0.005 afPrimary = 0.08 cfs @ 12.24 hrs, Volume= 0.005 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs

Type III 24-hr 10 Year Event Rainfall=4.65"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 10HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Peak Elev= 82.89' @ 12.24 hrs Surf.Area= 306 sf Storage= 291 cf

Plug-Flow detention time= 272.2 min calculated for 0.010 af (68% of inflow)Center-of-Mass det. time= 173.7 min ( 922.0 - 748.3 )

Volume Invert Avail.Storage Storage Description

#1 81.20' 189 cf Custom Stage Data (Irregular) Listed below (Recalc)612 cf Overall - 140 cf Embedded = 472 cf x 40.0% Voids

#2 81.70' 140 cf Cultec C-100 x 10 Inside #1Effective Size= 32.1"W x 12.0"H => 1.86 sf x 7.50'L = 14.0 cfOverall Size= 36.0"W x 12.5"H x 8.00'L with 0.50' Overlap

329 cf Total Available Storage

Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area(feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft)

81.20 306 70.0 0 0 30683.20 306 70.0 612 612 446

Device Routing Invert Outlet Devices

#1 Primary 82.70' 4.0" Vert. Orifice/Grate C= 0.600 #2 Discarded 81.20' 0.270 in/hr Exfiltration over Wetted area

Discarded OutFlow Max=0.00 cfs @ 12.24 hrs HW=82.89' (Free Discharge)2=Exfiltration (Exfiltration Controls 0.00 cfs)

Primary OutFlow Max=0.08 cfs @ 12.24 hrs HW=82.89' (Free Discharge)1=Orifice/Grate (Orifice Controls 0.08 cfs @ 1.49 fps)

Summary for Pond 2P: 17 x 18 No. 2

Inflow Area = 0.032 ac,100.00% Impervious, Inflow Depth = 4.41" for 10 Year Event eventInflow = 0.15 cfs @ 12.07 hrs, Volume= 0.012 afOutflow = 0.03 cfs @ 12.48 hrs, Volume= 0.008 af, Atten= 79%, Lag= 24.4 minDiscarded = 0.00 cfs @ 12.48 hrs, Volume= 0.005 afPrimary = 0.03 cfs @ 12.48 hrs, Volume= 0.002 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsPeak Elev= 89.82' @ 12.48 hrs Surf.Area= 306 sf Storage= 270 cf

Plug-Flow detention time= 324.2 min calculated for 0.008 af (64% of inflow)Center-of-Mass det. time= 219.6 min ( 967.9 - 748.3 )

Volume Invert Avail.Storage Storage Description

#1 88.30' 189 cf Custom Stage Data (Irregular) Listed below (Recalc)612 cf Overall - 140 cf Embedded = 472 cf x 40.0% Voids

#2 88.80' 140 cf Cultec C-100 x 10 Inside #1Effective Size= 32.1"W x 12.0"H => 1.86 sf x 7.50'L = 14.0 cfOverall Size= 36.0"W x 12.5"H x 8.00'L with 0.50' Overlap

329 cf Total Available Storage

Type III 24-hr 10 Year Event Rainfall=4.65"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 11HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area(feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft)

88.30 306 70.0 0 0 30690.30 306 70.0 612 612 446

Device Routing Invert Outlet Devices

#1 Primary 89.70' 3.0" Vert. Orifice/Grate C= 0.600 #2 Discarded 88.30' 0.270 in/hr Exfiltration over Wetted area

Discarded OutFlow Max=0.00 cfs @ 12.48 hrs HW=89.82' (Free Discharge)2=Exfiltration (Exfiltration Controls 0.00 cfs)

Primary OutFlow Max=0.03 cfs @ 12.48 hrs HW=89.82' (Free Discharge)1=Orifice/Grate (Orifice Controls 0.03 cfs @ 1.19 fps)

Type III 24-hr 100 Year Event Rainfall=6.80"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 12HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Time span=0.00-30.00 hrs, dt=0.01 hrs, 3001 pointsRunoff by SCS TR-20 method, UH=SCS, Weighted-CN

Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method

Runoff Area=20,899 sf 13.25% Impervious Runoff Depth=3.97"Subcatchment E1: Exist. Cond. 2019 Tc=5.0 min CN=75 Runoff=2.32 cfs 0.159 af

Runoff Area=17,747 sf 8.65% Impervious Runoff Depth=4.08"Subcatchment P1: Proposed Remainder Tc=5.0 min CN=76 Runoff=2.02 cfs 0.139 af

Runoff Area=1,744 sf 100.00% Impervious Runoff Depth=6.56"Subcatchment P2: Roof / Driveway Tc=5.0 min CN=98 Runoff=0.28 cfs 0.022 af

Runoff Area=1,408 sf 100.00% Impervious Runoff Depth=6.56"Subcatchment P4: Portion Roof Tc=5.0 min CN=98 Runoff=0.22 cfs 0.018 af

Inflow=2.32 cfs 0.159 afReach 1R: Rear Yard Outflow=2.32 cfs 0.159 af

Inflow=2.32 cfs 0.158 afReach 2R: Rear Yard Outflow=2.32 cfs 0.158 af

Peak Elev=83.16' Storage=323 cf Inflow=0.28 cfs 0.022 afPond 1P: 17 x 18 No. 1 Discarded=0.00 cfs 0.006 af Primary=0.23 cfs 0.011 af Outflow=0.23 cfs 0.017 af

Peak Elev=90.14' Storage=309 cf Inflow=0.22 cfs 0.018 afPond 2P: 17 x 18 No. 2 Discarded=0.00 cfs 0.005 af Primary=0.13 cfs 0.008 af Outflow=0.13 cfs 0.013 af

Total Runoff Area = 0.960 ac Runoff Volume = 0.337 af Average Runoff Depth = 4.21"82.16% Pervious = 0.788 ac 17.84% Impervious = 0.171 ac

Type III 24-hr 100 Year Event Rainfall=6.80"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 13HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Summary for Subcatchment E1: Exist. Cond. 2019

Runoff = 2.32 cfs @ 12.07 hrs, Volume= 0.159 af, Depth= 3.97"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 100 Year Event Rainfall=6.80"

Area (sf) CN Description

1,157 98 Paved parking, HSG C1,075 98 Roofs, HSG C

* 537 98 other impervious8,839 74 >75% Grass cover, Good, HSG C9,291 70 Woods, Good, HSG C

20,899 75 Weighted Average18,130 86.75% Pervious Area2,769 13.25% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Subcatchment P1: Proposed Remainder

Runoff = 2.02 cfs @ 12.07 hrs, Volume= 0.139 af, Depth= 4.08"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 100 Year Event Rainfall=6.80"

Area (sf) CN Description

603 98 Paved parking, HSG C* 130 98 Roofs, HSG C - Porch - Front* 803 98 other impervous

14,386 74 >75% Grass cover, Good, HSG C1,825 70 Woods, Good, HSG C

17,747 76 Weighted Average16,211 91.35% Pervious Area1,536 8.65% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Subcatchment P2: Roof / Driveway

Runoff = 0.28 cfs @ 12.07 hrs, Volume= 0.022 af, Depth= 6.56"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 100 Year Event Rainfall=6.80"

Type III 24-hr 100 Year Event Rainfall=6.80"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 14HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Area (sf) CN Description

* 877 98 Roof* 867 98 Driveway

1,744 98 Weighted Average1,744 100.00% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Subcatchment P4: Portion Roof

Runoff = 0.22 cfs @ 12.07 hrs, Volume= 0.018 af, Depth= 6.56"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsType III 24-hr 100 Year Event Rainfall=6.80"

Area (sf) CN Description

* 1,408 98 Roof

1,408 100.00% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

5.0 Direct Entry, direct

Summary for Reach 1R: Rear Yard

Inflow Area = 0.480 ac, 13.25% Impervious, Inflow Depth = 3.97" for 100 Year Event eventInflow = 2.32 cfs @ 12.07 hrs, Volume= 0.159 afOutflow = 2.32 cfs @ 12.07 hrs, Volume= 0.159 af, Atten= 0%, Lag= 0.0 min

Routing by Stor-Ind+Trans method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs

Summary for Reach 2R: Rear Yard

Inflow Area = 0.480 ac, 22.43% Impervious, Inflow Depth = 3.94" for 100 Year Event eventInflow = 2.32 cfs @ 12.08 hrs, Volume= 0.158 afOutflow = 2.32 cfs @ 12.08 hrs, Volume= 0.158 af, Atten= 0%, Lag= 0.0 min

Routing by Stor-Ind+Trans method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs

Summary for Pond 1P: 17 x 18 No. 1

Inflow Area = 0.040 ac,100.00% Impervious, Inflow Depth = 6.56" for 100 Year Event eventInflow = 0.28 cfs @ 12.07 hrs, Volume= 0.022 afOutflow = 0.23 cfs @ 12.12 hrs, Volume= 0.017 af, Atten= 17%, Lag= 3.0 minDiscarded = 0.00 cfs @ 12.12 hrs, Volume= 0.006 afPrimary = 0.23 cfs @ 12.12 hrs, Volume= 0.011 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs

Type III 24-hr 100 Year Event Rainfall=6.80"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 15HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Peak Elev= 83.16' @ 12.12 hrs Surf.Area= 306 sf Storage= 323 cf

Plug-Flow detention time= 201.1 min calculated for 0.017 af (78% of inflow)Center-of-Mass det. time= 118.3 min ( 860.7 - 742.4 )

Volume Invert Avail.Storage Storage Description

#1 81.20' 189 cf Custom Stage Data (Irregular) Listed below (Recalc)612 cf Overall - 140 cf Embedded = 472 cf x 40.0% Voids

#2 81.70' 140 cf Cultec C-100 x 10 Inside #1Effective Size= 32.1"W x 12.0"H => 1.86 sf x 7.50'L = 14.0 cfOverall Size= 36.0"W x 12.5"H x 8.00'L with 0.50' Overlap

329 cf Total Available Storage

Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area(feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft)

81.20 306 70.0 0 0 30683.20 306 70.0 612 612 446

Device Routing Invert Outlet Devices

#1 Primary 82.70' 4.0" Vert. Orifice/Grate C= 0.600 #2 Discarded 81.20' 0.270 in/hr Exfiltration over Wetted area

Discarded OutFlow Max=0.00 cfs @ 12.12 hrs HW=83.16' (Free Discharge)2=Exfiltration (Exfiltration Controls 0.00 cfs)

Primary OutFlow Max=0.23 cfs @ 12.12 hrs HW=83.16' (Free Discharge)1=Orifice/Grate (Orifice Controls 0.23 cfs @ 2.60 fps)

Summary for Pond 2P: 17 x 18 No. 2

Inflow Area = 0.032 ac,100.00% Impervious, Inflow Depth = 6.56" for 100 Year Event eventInflow = 0.22 cfs @ 12.07 hrs, Volume= 0.018 afOutflow = 0.13 cfs @ 12.16 hrs, Volume= 0.013 af, Atten= 40%, Lag= 5.6 minDiscarded = 0.00 cfs @ 12.16 hrs, Volume= 0.005 afPrimary = 0.13 cfs @ 12.16 hrs, Volume= 0.008 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrsPeak Elev= 90.14' @ 12.16 hrs Surf.Area= 306 sf Storage= 309 cf

Plug-Flow detention time= 228.0 min calculated for 0.013 af (74% of inflow)Center-of-Mass det. time= 139.0 min ( 881.4 - 742.4 )

Volume Invert Avail.Storage Storage Description

#1 88.30' 189 cf Custom Stage Data (Irregular) Listed below (Recalc)612 cf Overall - 140 cf Embedded = 472 cf x 40.0% Voids

#2 88.80' 140 cf Cultec C-100 x 10 Inside #1Effective Size= 32.1"W x 12.0"H => 1.86 sf x 7.50'L = 14.0 cfOverall Size= 36.0"W x 12.5"H x 8.00'L with 0.50' Overlap

329 cf Total Available Storage

Type III 24-hr 100 Year Event Rainfall=6.80"40 Harbor View 2021 Printed 4/1/2021Prepared by Cavanaro Consulting

Page 16HydroCAD® 10.00-24 s/n 01769 © 2018 HydroCAD Software Solutions LLC

Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area(feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft)

88.30 306 70.0 0 0 30690.30 306 70.0 612 612 446

Device Routing Invert Outlet Devices

#1 Primary 89.70' 3.0" Vert. Orifice/Grate C= 0.600 #2 Discarded 88.30' 0.270 in/hr Exfiltration over Wetted area

Discarded OutFlow Max=0.00 cfs @ 12.16 hrs HW=90.14' (Free Discharge)2=Exfiltration (Exfiltration Controls 0.00 cfs)

Primary OutFlow Max=0.13 cfs @ 12.16 hrs HW=90.14' (Free Discharge)1=Orifice/Grate (Orifice Controls 0.13 cfs @ 2.68 fps)

ESUB

Fax: 781.659.8186

687 MAIN STREET

Phone: 781.659.8187

P.O. BOX 5175

Cavanaro Consulting

Norwell, Massachusetts 02061

PREPARED FOR:

APF DEVELOPMENT GROUP LLC

40 HARBOR VIEW DRIVE

HINGHAM, MA 02043

PSUBFax: 781.659.8186

687 MAIN STREET

Phone: 781.659.8187

P.O. BOX 5175

Cavanaro Consulting

Norwell, Massachusetts 02061

PREPARED FOR:

APF DEVELOPMENT GROUP LLC

40 HARBOR VIEW DRIVE

HINGHAM, MA 02043

SECTION V

LOCUS DEED EASEMENT STATEMENT

Easement Statement There are no known recorded existing or proposed stormwater easements in the area of proposed work.

SECTION VI

SITE PLAN See Attached