2060.01 drn index - town of chesterfield, nh€¦ · spofford lake to the north, residential...

Index Narrative with Summary Tables

Chesterfield GIS Locus

Web Soil Survey

Aerial Photograph

Drainage Analysis / Stormwater Management Report:

Section 1.1 Existing Conditions – 10 Year Storm Full Summary

Section 1.2 Existing Conditions – 50 Year Storm Summary

Section 2.1 Proposed Conditions – 10 Year Storm Full Summary

Section 2.2 Proposed Conditions – 50 Year Storm Summary

Supplemental Data:

Section 3.1 Test Pit Data & Soil Testing Report

Section 3.2 Inspection & Maintenance Manual

Section 3.3 Drainage Area Plans

STORMWATER MANAGEMENT REPORT TAX MAP PARCELS 5K-B-8 & 5N-B-9-1

ROUTE 9A & CANAL STREET CHESTERFIELD, NEW HAMPSHIRE

Prepared for: Pine Grove Springs Country Club

January 8, 2020

I) INTRODUCTION

The following are stormwater drainage calculations for the proposed subdivision of Tax Map Parcels 5K-B-8 & 5N-B-9-1 in Chesterfield, NH. The Pine Grove Springs golf course is located on both subject parcels. The applicant is proposing a 4 residential lot subdivision of lot 5K-B-8 and a single residential subdivision of lot 5N-B-9-1 away from the existing golf course. Parcel 5K-B-8 consists of 8.744 acres and parcel 5N-B-9-1 consists of 83.01 acres. The subject parcels are bordered by Spofford Lake to the north, residential properties to the east and west, and an industrial site to the south. The project is located at the intersection of Route 9A and Butler Road. The site is serviced by overhead utilities. This report is submitted on behalf of Pine Grove Springs Country Club, Inc. relative to its proposed subdivision of five (5) lots, as described above, which is currently being used as a golf course. Pine Grove plans to sell the new lots and has no plans to develop them. The plan shows an average single family home, garage and driveway being constructed on each new lot. To prepare this report, Fieldstone has assumed the levels of disturbance shown on the plan to prepare this report. Any lot alteration within 250 feet of Spofford Lake will require a State Shoreland Permit. The purpose of this report is to analyze the qualitative and quantitative impacts of the proposed development expansion. The objective of the proposed stormwater management system for this project is to mitigate any increases resulting from the proposed development and to meet the drainage guidelines set forth in the Town of Chesterfield Regulations.

II) SITE DESCRIPTION (EXISTING)

The subject properties are currently improved lots containing a golf course and driving range. Lot 5K-B-8 is composed of mostly maintained lawn with some small areas of woods and landscaped trees. There are approximately 2 acres of wet field/lawn area over Parcel 5K-B-8 and the vegetation on-site currently acts like a vegetated filter strip treating stormwater runoff that eventually drains to Spofford Lake. The southern property, 5N-B-9-1 contains a majority of the golf course as well as larger wooded areas. Both lots slope north to Spofford Lake and the stormwater from lot 5N-B-9-1 passes through a culvert under Route 9A and across 5N-B-8 before reaching the lake. The NRCS soil

Pine Grove Springs Country Club – Subdivision, Tax Map Parcels 5K-B-8 & 5N-B-9-1 Route 9A & 292 Route 9A - Stormwater Management Report Page 2

survey maps indicated that there are numerous soils present on the subject parcel. The lot consists of Naumburg loamy fine sand, Cardigan-Kearsarge Complex of various slopes, Cardigan-Kearsarge-Rock outcrop complex, and Dutchess silt loam of various slopes.

III) METHODOLOGY

The quantity of runoff and the conveyance of that flow through the site are determined using the software package HydroCAD r 10.0 by HydroCAD Software Solutions, LLC. HydroCAD is a computer aided design program for modeling storm water hydrology based on the Soil Conservation Service (SCS) TR-20 method combined with standard hydraulics calculations used to model detention basins and culverts. Stormwater management systems and erosion control are designed in accordance with the methodology for the "Best Management Practices" (BMP’s), as outlined in the New Hampshire Storm Water Manual, Volume 2.

IV) DRAINAGE DESIGN

Town of Chesterfield Land Development Regulations: Preliminary Surface Water Drainage Management Plan (SWDMP) requires estimates for both the 10 year/24 hour storm and the 50 year/24 hour storm to be calculated in accordance with the Soil Conservation Service’s handbook: “Urban Hydrology for Small Watersheds, Technical Release No. 55,” as amended. These design storms have therefore been analyzed to compare the pre and post-development peak flow rates for the site (see attached comparison tables in accordance with TR-55’s methodology). Pre-Development Drainage Conditions: The properties are divided into two watersheds that drain the subject area. The stormwater runoff for Subcatchment 1S drains the entirety of parcel 5K-B-8. The stormwater flows from south to north, across the maintained lawn area until it ultimately discharges into Spofford Lake (OP1). The watershed to the south (Subcatchment 2S) conveys stormwater north under route 9A through a culvert (1P) and across lot 5K-B-8 to Spofford Lake.

Post-Development Drainage Conditions: As can be seen on the Post-Development Drainage Plan, Subcatchments 102S and 103S will include many of the proposed houses, driveways, and associated site improvements on lots 5K-B-8-1, 5K-B-8-2, 5K-B-8-3, and 5K-B-8-4. Stormwater will be conveyed through conveyance swales to one of the proposed rain gardens (P2 & P3) where the water will be treated and detained then released over level spreaders to Spofford Lake. Subcatchment 101S captures the remaining runoff from the watershed area and drains to Spofford Lake. The proposed improvements in subcatchment 201S include a single house and driveway. The stormwater flows from this subcatchment flow under Route 9A via a 12” culvert (P1) then under a proposed driveway via an 18” culvert (P4) and drains north to Spofford Lake.

Pine Grove Springs Country Club – Subdivision, Tax Map Parcels 5K-B-8 & 5N-B-9-1 Route 9A & 292 Route 9A - Stormwater Management Report Page 3 V) SUMMARY

The intent of the stormwater management system for this project is to address the qualitative and quantitative aspects of the stormwater runoff so that there are no downstream adverse impacts created by the project. To mitigate the resulting increases in runoff rates due to the development of residential buildings and associated site improvements this project proposes the construction of conveyance swales and rain gardens with level spreaders as depicted on this plan.

The net result is that the new development will have no increase in the peak rates of stormwater runoff leaving the site. The proposed drainage system will treat and mitigate increases in runoff rates for the 10 and 50-year storm events as illustrated in Table 1.1 below.

The development of the subject property will likely lead to improved buffering to the Lake too as lawn areas will most likely be minimized for maintenance purposes which will ultimately provide for increased buffering and filtering of stormwater before draining into the Lake.

This design addresses the qualitative and quantitative aspects of the stormwater runoff and therefore this development will have no adverse impacts to the Lake.

The following tables are a summary of the attached calculations and show a comparison of the peak flow rates at the observation points for the site. The values presented are based on pre- and post-development conditions.

Table 1.1: Peak Flow Rates (CFS)/Volume (AF) to Wetlands- OP1 – with Post-Development Infiltration

STORM FREQUENCY PRE-DEV. RUNOFF (CFS)

POST-DEV. RUNOFF (CFS)

CHANGE (CFS)

10-YEAR 13.35 12.01 -1.34

50-YEAR 26.85 24.02 -2.71

Soil Map—Cheshire County, New Hampshire

Natural ResourcesConservation Service

Web Soil SurveyNational Cooperative Soil Survey

2/19/2019Page 1 of 4

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200709100 709200 709300 709400 709500 709600 709700 709800 709900 710000 710100 710200 710300 710400 710500

709200 709300 709400 709500 709600 709700 709800 709900 710000 710100 710200 710300 710400 710500 710600

42° 54' 41'' N72

° 2

6' 1

9'' W

42° 54' 41'' N

72° 2

5' 1

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42° 54' 9'' N

72° 2

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N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS840 300 600 1200 1800

Feet0 100 200 400 600

MetersMap Scale: 1:6,840 if printed on A landscape (11" x 8.5") sheet.

Soil Map may not be valid at this scale.

MAP LEGEND MAP INFORMATION

Area of Interest (AOI)Area of Interest (AOI)

SoilsSoil Map Unit Polygons

Soil Map Unit Lines

Soil Map Unit Points

Special Point FeaturesBlowout

Borrow Pit

Clay Spot

Closed Depression

Gravel Pit

Gravelly Spot

Landfill

Lava Flow

Marsh or swamp

Mine or Quarry

Miscellaneous Water

Perennial Water

Rock Outcrop

Saline Spot

Sandy Spot

Severely Eroded Spot

Sinkhole

Slide or Slip

Sodic Spot

Spoil Area

Stony Spot

Very Stony Spot

Wet Spot

Other

Special Line Features

Water FeaturesStreams and Canals

TransportationRails

Interstate Highways

US Routes

Major Roads

Local Roads

BackgroundAerial Photography

The soil surveys that comprise your AOI were mapped at 1:20,000.

Warning: Soil Map may not be valid at this scale.

Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale.

Please rely on the bar scale on each map sheet for map measurements.

Source of Map: Natural Resources Conservation ServiceWeb Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857)

Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required.

This product is generated from the USDA-NRCS certified data as of the version date(s) listed below.

Soil Survey Area: Cheshire County, New HampshireSurvey Area Data: Version 21, Sep 7, 2018

Soil map units are labeled (as space allows) for map scales 1:50,000 or larger.

Date(s) aerial images were photographed: Apr 9, 2011—May 12, 2011

The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident.




2/19/2019Page 2 of 4

Map Unit Legend

Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI

24B Agawam fine sandy loam, 3 to 8 percent slopes

4.7 2.0%

107 Rippowam-Saco complex 4.3 1.9%

214 Naumburg loamy fine sand 5.7 2.5%

330C Bernardston silt loam, 8 to 15 percent slopes

0.1 0.1%

330D Bernardston silt loam, 15 to 25 percent slopes

2.9 1.3%

334B Pittstown silt loam, 3 to 8 percent slopes

3.3 1.4%

336B Pittstown silt loam, 3 to 8 percent slopes, very stony

6.3 2.8%

341B Stissing silt loam, 0 to 5 percent slopes, very stony

11.6 5.1%

360B Cardigan-Kearsarge complex, 3 to 8 percent slopes

5.9 2.6%

360D Cardigan-Kearsarge complex, 15 to 25 percent slopes

15.0 6.6%

361C Cardigan-Kearsarge-Rock outcrop complex, 8 to 15 percent slopes

43.9 19.2%

361D Cardigan-Kearsarge-Rock outcrop complex, 15 to 25 percent slopes

25.9 11.3%

366C Dutchess silt loam, 8 to 15 percent slopes

25.0 11.0%

366D Dutchess silt loam, 15 to 25 percent slopes

16.7 7.3%

367C Dutchess silt loam, 8 to 15 percent slopes, very stony

13.6 5.9%

367D Dutchess silt loam, 15 to 25 percent slopes, very stony

8.2 3.6%

367E Dutchess silt loam, 25 to 50 percent slopes, very stony

8.4 3.7%

414 Moosilauke fine sandy loam 3.5 1.6%

510C Hoosic gravelly fine sandy loam, 8 to 15 percent slopes

0.0 0.0%

510E Hoosic gravelly fine sandy loam, 15 to 50 percent slopes

2.9 1.3%

513B Ninigret fine sandy loam, 3 to 8 percent slopes

0.3 0.1%

613B Croghan loamy fine sand, 0 to 5 percent slopes

1.6 0.7%




2/19/2019Page 3 of 4

Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI

W Water 18.5 8.1%

Totals for Area of Interest 228.4 100.0%




2/19/2019Page 4 of 4

Section 1.1

Existing Conditions 10 Year Storm Full Summary

1S

NORTH OF 9A

2S

SOUTH OF 9A

TT1

TRAVEL TIME

1P

12" CMP

OP1

SPOFFORD LAKE

Routing Diagram for 2060.01_PRE_DEVELOPMENTPrepared by Microsoft, Printed 1/9/2020

HydroCAD® 10.00-20 s/n 06037 © 2017 HydroCAD Software Solutions LLC

Subcat Reach Pond Link

2060.01_PRE_DEVELOPMENT Printed 1/9/2020Prepared by Microsoft

Page 2HydroCAD® 10.00-20 s/n 06037 © 2017 HydroCAD Software Solutions LLC

Area Listing (all nodes)

Area(acres)

CN Description(subcatchment-numbers)

4.007 39 >75% Grass cover, Good, HSG A (1S)4.558 61 >75% Grass cover, Good, HSG B (1S, 2S)6.352 74 >75% Grass cover, Good, HSG C (1S, 2S)0.222 96 Gravel surface, HSG A (1S)0.076 96 Gravel surface, HSG C (1S)0.021 98 Paved parking, HSG A (1S)0.387 98 Paved parking, HSG B (1S, 2S)0.154 98 Paved parking, HSG C (1S, 2S)0.331 98 Roofs, HSG A (1S)0.974 30 Woods, Good, HSG A (1S)0.755 55 Woods, Good, HSG B (1S, 2S)3.967 70 Woods, Good, HSG C (1S, 2S)

21.805 63 TOTAL AREA

2060.01_PRE_DEVELOPMENT Printed 1/9/2020Prepared by Microsoft


Soil Listing (all nodes)

Area(acres)

SoilGroup

SubcatchmentNumbers

5.555 HSG A 1S5.701 HSG B 1S, 2S

10.549 HSG C 1S, 2S0.000 HSG D0.000 Other

21.805 TOTAL AREA

Type III 24-hr 10-Year Rainfall=4.20"2060.01_PRE_DEVELOPMENT Printed 1/9/2020Prepared by Microsoft


Time span=5.00-20.00 hrs, dt=0.02 hrs, 751 points x 3Runoff by SCS TR-20 method, UH=SCS, Weighted-CN

Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method

Runoff Area=583,259 sf 5.20% Impervious Runoff Depth>0.71"Subcatchment 1S: NORTH OF 9A Flow Length=801' Tc=19.1 min CN=59 Runoff=6.88 cfs 0.797 af

Runoff Area=366,549 sf 2.35% Impervious Runoff Depth>1.20"Subcatchment 2S: SOUTH OF 9A Flow Length=1,484' Tc=29.4 min CN=68 Runoff=7.06 cfs 0.842 af

Avg. Flow Depth=0.44' Max Vel=5.05 fps Inflow=7.06 cfs 0.842 afReach TT1: TRAVEL TIMEn=0.030 L=550.0' S=0.0545 '/' Capacity=175.54 cfs Outflow=7.03 cfs 0.840 af

Peak Elev=748.60' Storage=279 cf Inflow=7.06 cfs 0.842 afPond 1P: 12" CMP Outflow=7.06 cfs 0.842 af

Inflow=13.35 cfs 1.637 afLink OP1: SPOFFORD LAKE Primary=13.35 cfs 1.637 af

Total Runoff Area = 21.805 ac Runoff Volume = 1.640 af Average Runoff Depth = 0.90"95.90% Pervious = 20.910 ac 4.10% Impervious = 0.894 ac



Summary for Subcatchment 1S: NORTH OF 9A

Runoff = 6.88 cfs @ 12.32 hrs, Volume= 0.797 af, Depth> 0.71"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-20.00 hrs, dt= 0.02 hrsType III 24-hr 10-Year Rainfall=4.20"

Area (sf) CN Description14,434 98 Roofs, HSG A

919 98 Paved parking, HSG A10,398 98 Paved parking, HSG B

4,583 98 Paved parking, HSG C9,667 96 Gravel surface, HSG A3,298 96 Gravel surface, HSG C

174,525 39 >75% Grass cover, Good, HSG A116,580 61 >75% Grass cover, Good, HSG B175,548 74 >75% Grass cover, Good, HSG C

42,414 30 Woods, Good, HSG A1,306 55 Woods, Good, HSG B

29,587 70 Woods, Good, HSG C583,259 59 Weighted Average552,925 94.80% Pervious Area

30,334 5.20% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)11.2 100 0.0400 0.15 Sheet Flow, A=>B

Grass: Dense n= 0.240 P2= 3.00"7.8 651 0.0400 1.40 Shallow Concentrated Flow, B=>C

Short Grass Pasture Kv= 7.0 fps0.1 50 0.0500 7.94 26.47 Parabolic Channel, C=>D

W=5.00' D=1.00' Area=3.3 sf Perim=5.5' n= 0.03019.1 801 Total

Summary for Subcatchment 2S: SOUTH OF 9A



Area (sf) CN Description6,480 98 Paved parking, HSG B2,146 98 Paved parking, HSG C

81,956 61 >75% Grass cover, Good, HSG B101,153 74 >75% Grass cover, Good, HSG C

31,602 55 Woods, Good, HSG B143,212 70 Woods, Good, HSG C366,549 68 Weighted Average357,923 97.65% Pervious Area





Woods: Dense underbrush n= 0.800 P2= 3.00"8.6 1,200 0.1100 2.32 Shallow Concentrated Flow, B=>C


W=5.00' D=1.00' Area=3.3 sf Perim=5.5'n= 0.040 Winding stream, pools & shoals

29.4 1,484 Total

Summary for Reach TT1: TRAVEL TIME

Inflow Area = 8.415 ac, 2.35% Impervious, Inflow Depth > 1.20" for 10-Year eventInflow = 7.06 cfs @ 12.45 hrs, Volume= 0.842 afOutflow = 7.03 cfs @ 12.47 hrs, Volume= 0.840 af, Atten= 0%, Lag= 1.2 min

Routing by Dyn-Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.02 hrs / 3Max. Velocity= 5.05 fps, Min. Travel Time= 1.8 minAvg. Velocity = 2.60 fps, Avg. Travel Time= 3.5 min

Peak Storage= 765 cf @ 12.47 hrsAverage Depth at Peak Storage= 0.44'Bank-Full Depth= 2.00' Flow Area= 13.3 sf, Capacity= 175.54 cfs

10.00' x 2.00' deep Parabolic Channel, n= 0.030 Earth, grassed & windingLength= 550.0' Slope= 0.0545 '/'Inlet Invert= 746.00', Outlet Invert= 716.00'

Summary for Pond 1P: 12" CMP

Inflow Area = 8.415 ac, 2.35% Impervious, Inflow Depth > 1.20" for 10-Year eventInflow = 7.06 cfs @ 12.45 hrs, Volume= 0.842 afOutflow = 7.06 cfs @ 12.45 hrs, Volume= 0.842 af, Atten= 0%, Lag= 0.3 minPrimary = 7.06 cfs @ 12.45 hrs, Volume= 0.842 af

Routing by Dyn-Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.02 hrs / 3Peak Elev= 748.60' @ 12.45 hrs Surf.Area= 426 sf Storage= 279 cfFlood Elev= 748.50' Surf.Area= 300 sf Storage= 244 cf

Plug-Flow detention time= 0.6 min calculated for 0.841 af (100% of inflow)Center-of-Mass det. time= 0.5 min ( 837.2 - 836.8 )



Volume Invert Avail.Storage Storage Description#1 745.00' 557 cf Custom Stage Data (Prismatic) Listed below (Recalc)

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

745.00 10 0 0746.00 16 13 13748.00 112 128 141748.50 300 103 244749.00 950 313 557

Device Routing Invert Outlet Devices#1 Primary 745.42' 12.0" Round Culvert

L= 38.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 745.42' / 745.00' S= 0.0111 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 0.79 sf

#2 Primary 748.50' 40.0' long x 24.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63

Primary OutFlow Max=7.05 cfs @ 12.45 hrs HW=748.60' TW=746.44' (Dynamic Tailwater)1=Culvert (Outlet Controls 3.80 cfs @ 4.84 fps)2=Broad-Crested Rectangular Weir (Weir Controls 3.25 cfs @ 0.84 fps)

Summary for Link OP1: SPOFFORD LAKE

Inflow Area = 21.805 ac, 4.10% Impervious, Inflow Depth > 0.90" for 10-Year eventInflow = 13.35 cfs @ 12.40 hrs, Volume= 1.637 afPrimary = 13.35 cfs @ 12.40 hrs, Volume= 1.637 af, Atten= 0%, Lag= 0.0 min

Primary outflow = Inflow, Time Span= 5.00-20.00 hrs, dt= 0.02 hrs

Section 1.2

Existing Conditions 50 Year Storm Summary



Summary for Subcatchment 1S: NORTH OF 9A




919 98 Paved parking, HSG A10,398 98 Paved parking, HSG B

4,583 98 Paved parking, HSG C9,667 96 Gravel surface, HSG A3,298 96 Gravel surface, HSG C

174,525 39 >75% Grass cover, Good, HSG A116,580 61 >75% Grass cover, Good, HSG B175,548 74 >75% Grass cover, Good, HSG C

42,414 30 Woods, Good, HSG A1,306 55 Woods, Good, HSG B

29,587 70 Woods, Good, HSG C583,259 59 Weighted Average552,925 94.80% Pervious Area



Grass: Dense n= 0.240 P2= 3.00"7.8 651 0.0400 1.40 Shallow Concentrated Flow, B=>C






Area (sf) CN Description6,480 98 Paved parking, HSG B2,146 98 Paved parking, HSG C

81,956 61 >75% Grass cover, Good, HSG B101,153 74 >75% Grass cover, Good, HSG C

31,602 55 Woods, Good, HSG B143,212 70 Woods, Good, HSG C366,549 68 Weighted Average357,923 97.65% Pervious Area







W=5.00' D=1.00' Area=3.3 sf Perim=5.5'n= 0.040 Winding stream, pools & shoals

29.4 1,484 Total




Peak Storage= 1,160 cf @ 12.45 hrsAverage Depth at Peak Storage= 0.58'Bank-Full Depth= 2.00' Flow Area= 13.3 sf, Capacity= 175.54 cfs

10.00' x 2.00' deep Parabolic Channel, n= 0.030 Earth, grassed & windingLength= 550.0' Slope= 0.0545 '/'Inlet Invert= 746.00', Outlet Invert= 716.00'

Summary for Pond 1P: 12" CMP








745.00 10 0 0746.00 16 13 13748.00 112 128 141748.50 300 103 244749.00 950 313 557




Primary OutFlow Max=12.78 cfs @ 12.43 hrs HW=748.69' TW=746.58' (Dynamic Tailwater)1=Culvert (Outlet Controls 3.76 cfs @ 4.79 fps)2=Broad-Crested Rectangular Weir (Weir Controls 9.02 cfs @ 1.17 fps)




Section 2.1

Proposed Conditions 10 Year Storm Full Summary

101S

DIRECT TO SPOFFORD LAKE

102S

TO RAIN GARDENS

103S

TO RAIN GARDENS

201S

SOUTH OF 9A

TT1

TRAVEL TIME

TT2

LEVEL SPREADERS

TT3

LEVEL SPREADERS

P1

12" CMP

P2

RAIN GARDENS (LOTS 3&4)

P3

RAIN GARDENS (LOTS 1&2)P4

18" CPP

OP1

SPOFFORD LAKE

Routing Diagram for 2060.01_POST_DEVELOPMENT_BPrepared by Microsoft, Printed 1/10/2020

HydroCAD® 10.00-20 s/n 06037 © 2017 HydroCAD Software Solutions LLC

Subcat Reach Pond Link

2060.01_POST_DEVELOPMENT_B Printed 1/10/2020Prepared by Microsoft


Area Listing (all nodes)

Area(acres)

CN Description(subcatchment-numbers)

3.796 39 >75% Grass cover, Good, HSG A (101S, 103S)4.211 61 >75% Grass cover, Good, HSG B (101S, 103S, 201S)6.098 74 >75% Grass cover, Good, HSG C (101S, 102S, 201S)0.222 96 Gravel surface, HSG A (101S)0.104 96 Gravel surface, HSG C (101S, 102S)0.071 98 Paved parking, HSG A (101S)0.735 98 Paved parking, HSG B (101S, 103S, 201S)0.273 98 Paved parking, HSG C (101S, 102S, 201S)0.492 98 Roofs, HSG A (101S, 103S, 201S)0.107 98 Roofs, HSG C (102S)0.974 30 Woods, Good, HSG A (101S)0.755 55 Woods, Good, HSG B (101S, 201S)3.967 70 Woods, Good, HSG C (101S, 102S, 201S)

21.805 64 TOTAL AREA

2060.01_POST_DEVELOPMENT_B Printed 1/10/2020Prepared by Microsoft


Soil Listing (all nodes)

Area(acres)

SoilGroup

SubcatchmentNumbers

5.555 HSG A 101S, 103S, 201S5.701 HSG B 101S, 103S, 201S

10.549 HSG C 101S, 102S, 201S0.000 HSG D0.000 Other

21.805 TOTAL AREA

Type III 24-hr 10-Year Rainfall=4.20"2060.01_POST_DEVELOPMENT_B Printed 1/10/2020Prepared by Microsoft


Time span=5.00-20.00 hrs, dt=0.02 hrs, 751 points x 3Runoff by SCS TR-20 method, UH=SCS, Weighted-CN

Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method

Runoff Area=419,367 sf 7.26% Impervious Runoff Depth>0.72"Subcatchment 101S: DIRECT TO Flow Length=680' Tc=15.2 min CN=59 Runoff=5.37 cfs 0.574 af

Runoff Area=67,220 sf 14.70% Impervious Runoff Depth>1.89"Subcatchment 102S: TO RAIN GARDENS Flow Length=250' Tc=12.6 min CN=78 Runoff=2.97 cfs 0.244 af

Runoff Area=96,672 sf 11.18% Impervious Runoff Depth>0.58"Subcatchment 103S: TO RAIN GARDENS Flow Length=245' Slope=0.1300 '/' Tc=7.9 min CN=56 Runoff=1.10 cfs 0.107 af

Runoff Area=366,549 sf 5.99% Impervious Runoff Depth>1.33"Subcatchment 201S: SOUTH OF 9A Flow Length=1,484' Tc=29.4 min CN=70 Runoff=7.89 cfs 0.930 af

Avg. Flow Depth=0.56' Max Vel=3.99 fps Inflow=7.88 cfs 0.928 afReach TT1: TRAVEL TIMEn=0.035 L=640.0' S=0.0344 '/' Capacity=119.45 cfs Outflow=7.82 cfs 0.924 af

Avg. Flow Depth=0.06' Max Vel=0.15 fps Inflow=1.46 cfs 0.114 afReach TT2: LEVEL SPREADERSn=0.240 L=510.0' S=0.0235 '/' Capacity=2.61 cfs Outflow=0.37 cfs 0.105 af

Avg. Flow Depth=0.05' Max Vel=0.09 fps Inflow=0.22 cfs 0.061 afReach TT3: LEVEL SPREADERSn=0.240 L=375.0' S=0.0107 '/' Capacity=1.32 cfs Outflow=0.13 cfs 0.053 af

Peak Elev=748.61' Storage=283 cf Inflow=7.89 cfs 0.930 afPond P1: 12" CMP Outflow=7.90 cfs 0.930 af

Peak Elev=732.06' Storage=4,670 cf Inflow=2.97 cfs 0.244 afPond P2: RAIN GARDENS (LOTS 3&4) Discarded=0.03 cfs 0.026 af Primary=1.46 cfs 0.114 af Outflow=1.49 cfs 0.140 af

Peak Elev=722.05' Storage=2,049 cf Inflow=1.10 cfs 0.107 afPond P3: RAIN GARDENS (LOTS 1&2) Outflow=0.22 cfs 0.061 af

Peak Elev=740.11' Storage=338 cf Inflow=7.90 cfs 0.930 afPond P4: 18" CPP Outflow=7.88 cfs 0.928 af

Inflow=12.01 cfs 1.657 afLink OP1: SPOFFORD LAKE Primary=12.01 cfs 1.657 af

Total Runoff Area = 21.805 ac Runoff Volume = 1.855 af Average Runoff Depth = 1.02"92.30% Pervious = 20.126 ac 7.70% Impervious = 1.678 ac



Summary for Subcatchment 101S: DIRECT TO SPOFFORD LAKE




3,101 98 Paved parking, HSG A11,975 98 Paved parking, HSG B

952 98 Paved parking, HSG C9,667 96 Gravel surface, HSG A1,751 96 Gravel surface, HSG C

126,431 39 >75% Grass cover, Good, HSG A64,243 61 >75% Grass cover, Good, HSG B

114,295 74 >75% Grass cover, Good, HSG C42,414 30 Woods, Good, HSG A

1,306 55 Woods, Good, HSG B28,798 70 Woods, Good, HSG C

419,367 59 Weighted Average388,905 92.74% Pervious Area


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

6.8 80 0.0900 0.20 Sheet Flow, A=>BGrass: Dense n= 0.240 P2= 3.00"

8.3 550 0.0250 1.11 Shallow Concentrated Flow, B=>CShort Grass Pasture Kv= 7.0 fps

0.1 50 0.0500 7.94 26.47 Parabolic Channel, C=>DW=5.00' D=1.00' Area=3.3 sf Perim=5.5' n= 0.030

15.2 680 Total

Summary for Subcatchment 102S: TO RAIN GARDENS



Area (sf) CN Description4,660 98 Roofs, HSG C5,220 98 Paved parking, HSG C2,787 96 Gravel surface, HSG C

789 70 Woods, Good, HSG C53,764 74 >75% Grass cover, Good, HSG C67,220 78 Weighted Average57,340 85.30% Pervious Area




Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)11.2 100 0.0400 0.15 Sheet Flow,

Grass: Dense n= 0.240 P2= 3.00"1.3 100 0.0700 1.32 Shallow Concentrated Flow,

Woodland Kv= 5.0 fps0.1 50 0.0500 7.94 26.47 Parabolic Channel,





Area (sf) CN Description4,660 98 Roofs, HSG A6,150 98 Paved parking, HSG B

46,943 61 >75% Grass cover, Good, HSG B38,919 39 >75% Grass cover, Good, HSG A96,672 56 Weighted Average85,862 88.82% Pervious Area10,810 11.18% Impervious Area


7.0 100 0.1300 0.24 Sheet Flow, Grass: Dense n= 0.240 P2= 3.00"

0.8 120 0.1300 2.52 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps

0.1 25 0.1300 7.23 12.06 Parabolic Channel, W=5.00' D=0.50' Area=1.7 sf Perim=5.1'n= 0.035 High grass

7.9 245 Total






Area (sf) CN Description13,880 98 Paved parking, HSG B

5,741 98 Paved parking, HSG C72,226 61 >75% Grass cover, Good, HSG B97,558 74 >75% Grass cover, Good, HSG C31,602 55 Woods, Good, HSG B

143,212 70 Woods, Good, HSG C2,330 98 Roofs, HSG A






W=5.00' D=1.00' Area=3.3 sf Perim=5.5' n= 0.04029.4 1,484 Total





10.00' x 2.00' deep Parabolic Channel, n= 0.035 Earth, dense weedsLength= 640.0' Slope= 0.0344 '/'Inlet Invert= 738.00', Outlet Invert= 716.00'



Summary for Reach TT2: LEVEL SPREADERS




40.00' x 0.20' deep channel, n= 0.240 Sheet flow over Dense GrassSide Slope Z-value= 3.0 '/' Top Width= 41.20'Length= 510.0' Slope= 0.0235 '/'Inlet Invert= 730.00', Outlet Invert= 718.00'

‡




Peak Storage= 572 cf @ 15.01 hrsAverage Depth at Peak Storage= 0.05'Bank-Full Depth= 0.20' Flow Area= 6.1 sf, Capacity= 1.32 cfs

30.00' x 0.20' deep channel, n= 0.240Side Slope Z-value= 3.0 '/' Top Width= 31.20'Length= 375.0' Slope= 0.0107 '/'Inlet Invert= 722.00', Outlet Invert= 718.00'

‡



Summary for Pond P1: 12" CMP






745.00 10 0 0746.00 16 13 13748.00 112 128 141748.50 300 103 244749.00 950 313 557




Primary OutFlow Max=7.89 cfs @ 12.44 hrs HW=748.61' TW=740.10' (Dynamic Tailwater)1=Culvert (Barrel Controls 4.18 cfs @ 5.33 fps)2=Broad-Crested Rectangular Weir (Weir Controls 3.71 cfs @ 0.87 fps)

Summary for Pond P2: RAIN GARDENS (LOTS 3&4)

Inflow Area = 1.543 ac, 14.70% Impervious, Inflow Depth > 1.89" for 10-Year eventInflow = 2.97 cfs @ 12.18 hrs, Volume= 0.244 afOutflow = 1.49 cfs @ 12.46 hrs, Volume= 0.140 af, Atten= 50%, Lag= 17.1 minDiscarded = 0.03 cfs @ 12.46 hrs, Volume= 0.026 afPrimary = 1.46 cfs @ 12.46 hrs, Volume= 0.114 af

Routing by Dyn-Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.02 hrs / 3Peak Elev= 732.06' @ 12.46 hrs Surf.Area= 2,765 sf Storage= 4,670 cf




Volume Invert Avail.Storage Storage Description#1 730.00' 7,375 cf Custom Stage Data (Prismatic) Listed below (Recalc)


730.00 1,750 0 0732.00 2,750 4,500 4,500733.00 3,000 2,875 7,375

Device Routing Invert Outlet Devices#1 Primary 732.00' 40.0' long x 4.0' breadth Broad-Crested Rectangular Weir

Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.38 2.54 2.69 2.68 2.67 2.67 2.65 2.66 2.66 2.68 2.72 2.73 2.76 2.79 2.88 3.07 3.32

#2 Discarded 730.00' 0.500 in/hr Exfiltration over Surface area

Discarded OutFlow Max=0.03 cfs @ 12.46 hrs HW=732.06' (Free Discharge)2=Exfiltration (Exfiltration Controls 0.03 cfs)

Primary OutFlow Max=1.45 cfs @ 12.46 hrs HW=732.06' TW=730.01' (Dynamic Tailwater)1=Broad-Crested Rectangular Weir (Weir Controls 1.45 cfs @ 0.59 fps)







720.00 730 0 0722.00 1,255 1,985 1,985723.00 1,500 1,378 3,363






Summary for Pond P4: 18" CPP


Routing by Dyn-Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.02 hrs / 3Peak Elev= 740.11' @ 12.46 hrs Surf.Area= 263 sf Storage= 338 cfFlood Elev= 743.00' Surf.Area= 750 sf Storage= 1,685 cf




736.00 10 0 0738.00 25 35 35740.00 250 275 310742.00 500 750 1,060744.00 1,000 1,500 2,560


L= 30.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 738.50' / 738.00' S= 0.0167 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.77 sf


Primary OutFlow Max=7.88 cfs @ 12.46 hrs HW=740.11' TW=738.56' (Dynamic Tailwater)1=Culvert (Inlet Controls 7.88 cfs @ 4.46 fps)2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)






Summary for Subcatchment 101S: DIRECT TO SPOFFORD LAKE




3,101 98 Paved parking, HSG A11,975 98 Paved parking, HSG B

952 98 Paved parking, HSG C9,667 96 Gravel surface, HSG A1,751 96 Gravel surface, HSG C

126,431 39 >75% Grass cover, Good, HSG A64,243 61 >75% Grass cover, Good, HSG B

114,295 74 >75% Grass cover, Good, HSG C42,414 30 Woods, Good, HSG A

1,306 55 Woods, Good, HSG B28,798 70 Woods, Good, HSG C




6.8 80 0.0900 0.20 Sheet Flow, A=>BGrass: Dense n= 0.240 P2= 3.00"

8.3 550 0.0250 1.11 Shallow Concentrated Flow, B=>CShort Grass Pasture Kv= 7.0 fps

0.1 50 0.0500 7.94 26.47 Parabolic Channel, C=>DW=5.00' D=1.00' Area=3.3 sf Perim=5.5' n= 0.030

15.2 680 Total




Area (sf) CN Description4,660 98 Roofs, HSG C5,220 98 Paved parking, HSG C2,787 96 Gravel surface, HSG C

789 70 Woods, Good, HSG C53,764 74 >75% Grass cover, Good, HSG C67,220 78 Weighted Average57,340 85.30% Pervious Area




Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)11.2 100 0.0400 0.15 Sheet Flow,

Grass: Dense n= 0.240 P2= 3.00"1.3 100 0.0700 1.32 Shallow Concentrated Flow,

Woodland Kv= 5.0 fps0.1 50 0.0500 7.94 26.47 Parabolic Channel,





Area (sf) CN Description4,660 98 Roofs, HSG A6,150 98 Paved parking, HSG B

46,943 61 >75% Grass cover, Good, HSG B38,919 39 >75% Grass cover, Good, HSG A96,672 56 Weighted Average85,862 88.82% Pervious Area10,810 11.18% Impervious Area


7.0 100 0.1300 0.24 Sheet Flow, Grass: Dense n= 0.240 P2= 3.00"

0.8 120 0.1300 2.52 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps

0.1 25 0.1300 7.23 12.06 Parabolic Channel, W=5.00' D=0.50' Area=1.7 sf Perim=5.1'n= 0.035 High grass

7.9 245 Total






Area (sf) CN Description13,880 98 Paved parking, HSG B

5,741 98 Paved parking, HSG C72,226 61 >75% Grass cover, Good, HSG B97,558 74 >75% Grass cover, Good, HSG C31,602 55 Woods, Good, HSG B

143,212 70 Woods, Good, HSG C2,330 98 Roofs, HSG A






W=5.00' D=1.00' Area=3.3 sf Perim=5.5' n= 0.04029.4 1,484 Total





10.00' x 2.00' deep Parabolic Channel, n= 0.035 Earth, dense weedsLength= 640.0' Slope= 0.0344 '/'Inlet Invert= 738.00', Outlet Invert= 716.00'







40.00' x 0.20' deep channel, n= 0.240 Sheet flow over Dense GrassSide Slope Z-value= 3.0 '/' Top Width= 41.20'Length= 510.0' Slope= 0.0235 '/'Inlet Invert= 730.00', Outlet Invert= 718.00'

‡





30.00' x 0.20' deep channel, n= 0.240Side Slope Z-value= 3.0 '/' Top Width= 31.20'Length= 375.0' Slope= 0.0107 '/'Inlet Invert= 722.00', Outlet Invert= 718.00'

‡



Summary for Pond P1: 12" CMP






745.00 10 0 0746.00 16 13 13748.00 112 128 141748.50 300 103 244749.00 950 313 557




Primary OutFlow Max=13.84 cfs @ 12.43 hrs HW=748.70' TW=741.78' (Dynamic Tailwater)1=Culvert (Barrel Controls 4.26 cfs @ 5.42 fps)2=Broad-Crested Rectangular Weir (Weir Controls 9.58 cfs @ 1.20 fps)


Inflow Area = 1.543 ac, 14.70% Impervious, Inflow Depth > 3.01" for 50-Year eventInflow = 4.71 cfs @ 12.17 hrs, Volume= 0.387 afOutflow = 4.59 cfs @ 12.21 hrs, Volume= 0.283 af, Atten= 3%, Lag= 2.2 minDiscarded = 0.03 cfs @ 12.21 hrs, Volume= 0.028 afPrimary = 4.56 cfs @ 12.21 hrs, Volume= 0.255 af







730.00 1,750 0 0732.00 2,750 4,500 4,500733.00 3,000 2,875 7,375



#2 Discarded 730.00' 0.500 in/hr Exfiltration over Surface area

Discarded OutFlow Max=0.03 cfs @ 12.21 hrs HW=732.13' (Free Discharge)2=Exfiltration (Exfiltration Controls 0.03 cfs)








720.00 730 0 0722.00 1,255 1,985 1,985723.00 1,500 1,378 3,363












736.00 10 0 0738.00 25 35 35740.00 250 275 310742.00 500 750 1,060744.00 1,000 1,500 2,560








Section 3.1

Test Pit Data & Soil Testing Analysis

Section 3.2

Inspection & Maintenance Manual

Pine Grove Springs Country Club, INC. – Subdivision 292 NH Route 9A, P.O. Box 56 ‐ Spofford, New Hampshire

Storm Water Management System Inspection and Maintenance Manual

2060.01_Maint Manual.doc Page 1

Introduction

The operation and maintenance of a storm water management system and its individual components is as

critical to system performance as the design. Without proper maintenance, best management practices (BMPs)

are likely to become functionally impaired or to fail, providing reduced or no treatment of storm water. Proper

operation and maintenance will ensure that the storm water system and individual BMPs will remain effective at

removing pollutants as designed and meeting New Hampshire’s water quality objectives. Proper maintenance

will:

Maintain the volume of storm water treated over the long term;

Sustain the pollutant removal efficiency of the BMP;

Reduce the risk of re‐suspending sediment and other pollutants captured by the BMP;

Prevent structural deterioration of the BMP and minimize the need for expensive repairs;

Decrease the potential for failure of the BMP.

Responsible Maintenance Party:

Applicant: Pine Grove Springs Country Club, INC.

292 Route 9A, P.O. Box 56

Spofford, NH 03462

Report Information:

Pine Grove Springs Country Club will be the entity responsible for implementing the required reporting,

inspection, and maintenance activities identified in the I & M manual.

Inspection and maintenance reports shall be completed after each inspection. Copies of the report

forms to be completed by the inspector are attached at the end of this manual, including:

o Inspection checklist to be used during each inspection;

o Inspection and maintenance logs to document each inspection and maintenance activity;

A plan showing the locations of all the storm water practices described in the I&M manual is attached at

the end of this manual.

Pine Grove Springs Country Club, INC. – Subdivision 292 Route 9A, P.O. Box 56 – Spofford, NH 03462 January 8, 2020 Storm Water Management System: Inspection and Maintenance Manual


Maintenance Recommendations for Best Management Practices:

The following recommendations are to be used as a guide for the inspection and maintenance of the

permanent erosion and sediment control measures.

We recommend that inspections be performed every couple of weeks and after larger storm events within the

first year following construction to ensure that the site remains stabilized (site and slopes).

Stone Berm Level Spreaders

Inspected annually for sediment accumulation, debris, and signs of erosion within the approach channel,

spreader channel or down slope of the spreader.

Remove debris upon inspection and mow annually to control woody vegetation within the spreader.

Remove sediment when accumulation exceeds 25% of spreader channel depth.

Repair any erosion and re‐grade or replace stone berm material as warranted by inspection

Reconstruct the spreader if down‐slope channelization indicates that the spreader is not level or that

discharge has become concentrated and corrections cannot be made through minor re‐grading.

Bioretention System (Rain Garden)

Systems should be inspected at least twice annually, and following any rainfall event exceeding 2.5

inches in a 24 hour period, with maintenance or rehabilitation conducted as warranted by such

inspection.

Pretreatment measures should be inspected at least twice annually, and cleaned of accumulated

sediment as warranted by inspection, but no less than once annually.

Trash and debris should be removed at each inspection.

At least once annually, system should be inspected for drawdown time. If bio retention system does not

drain within 72 hours following a rainfall event, then a qualified professional should assess the condition

of the facility to determine measures required to restore filtration function or infiltration function (as

applicable), including but not limited to removal of accumulated sediments or reconstruction of the

filter media.

Vegetation should be inspected at least annually, and maintained in healthy condition, including

pruning, removal and replacement of dead or diseased vegetation, and removal of invasive species.

Inspection Checklist /Maintenance Logs

The inspection checklist and maintenance logs following this report shall be used as a guide for the

inspection reporting for this project.



Inspection Checklist

Stone Berm Level Spreaders

Bioretention System (Rain Gardens)

Headwall Inlets and Outlets



Inspection and Maintenance Log

BMP Inspection

Date

Inspected

By

Maintenance

Required?

Maintenance Performed

1 Yes

No

2 Yes

No

3 Yes

No

4 Yes

No

5 Yes

No

6 Yes

No

7 Yes

No

8 Yes

No

9 Yes

No

Section 3.3

Drainage Area Plans

2060.01 drn index - town of chesterfield, nh€¦ · spofford lake to the north, residential...

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