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227 S St Storm hydro calcs and docs 8-13-2018The Engineer Group, LLC 20 Bofat Hill Road Chesterfield, MA 01012 Date:9/8/2015 RUNOFF CALCULATIONS AND SUPPORTING DOCUMENTS Prepared for BLACK SHEEP DEVELOPMENT, LLC Project 227 SOUTH STREET, NORTHAMPTON, MA INDEX: 1-8 RATIONAL METHOD RUNOFF CALCULATIONS 10yr Storm 9-11 RUNOFF COEFFICIENT and IDF CURVE DATA USED 12-23 SOILS MAP DATA 8/13/2018 Calculation of Overland Sheet Flow Travel Time Pre Construction T01 Using HEC-22 Iterative Process Flow unimproved grass – light underbrush Inputs Calculations Manning Roughness Overland Flow Time 0.4 9.3 min 40 ft Estimated Ti=9.6 min Rational Meth 8.42 <=Try This value 10 yr, I =5.50 in/hr 0.0125 Calculation of Overland Sheet Flow Travel Time Flow Asphalt pavement Inputs Calculations Manning Roughness Overland Flow Time 0.011 1.7 min Use 3 min since chart begins at 5 min, interpolate 60 ft Estimated Ti=5 min Rational Meth 2.35 <=Try This value 6.00 in 0.005 Calculation of Shallow Concentrated Flow Travel Time Equations for NCRS Method for Shallow Concentrated Flow Using the NCRS Method - U.S. units Inputs Calculations 148 ft For unpaved surface: 0.011 1.73 ft/sec 1.4 min where: L = length of the flow path, ft For paved surface:V = shallow concentrated flow velocity, ft/sec S = surface slope, ft/ft 2.1786754 ft/sec 1.1 min Calculation of Channnel Flow Travel Time Using the Manning Equation - U.S. units For a Trapezoidal Channel Cross-section Inputs Calculations 0.1 ft 0.0 V = Q/A 0.33 ft 0.8 ft R = A/P 0.055 0.05 ft 0.01 cfs 0.011 Where:Q = channel flow rate, cfs 0.324 ft/sec V = average velocity of flow, ft/sec 0.0003 ft/ft 3.9 min P = wetted perimeter of channel, ft 75 ft S = channel bottom slope, ft/ft n = Manning roughness coefficient for channel L = Length of Flow Path, ft Coefficient, n = Travel, t1 = Length of Flow Path, L = Ground Slope, S = Coefficient, n = Travel, t1 = Length of Flow Path, L = 10 yr, I = Ground Slope, S = t1c = L/(60V) for unpaved surface: V = 16.1345S0.5 Length of Flow Path, L = for paved surface: V = 20.3282S0.5 Ground Slope, S =Flow Velocity, V = Travel time, t2 =t2 = shallow concentrated flow runoff travel time, min Flow Velocity, V = Travel time, t2 = Bottom width, b = Cross-Sect. Area, A =ft2 Depth of flow, y = Wetted Perimeter, P = Side Slope, z = Hydraulic Radius, R = ( H:V = z:1 )t1d = L/(60V) Discharge, Q = Manning roughness, n = Ave. Velocity, V = Channel bottom slope, S =A = channel cross-sectional area, ft2 Channel travel time, tchannel = Length of Flow Path, L = c 1 of 23 Calculation of Channnel Flow Travel Time Using the Manning Equation - U.S. units For a Triangilar Channel Cross-section Inputs Calculations 2 ft 1.64 0.33 ft 8.3 ft 18 0.20 ft 4.65 cfs 0.011 2.838 ft/sec 0.0038 ft/ft 0.6 min 100 ft Calculation of Time of Concentration Inputs ( values from above)Calculations 9.3 min 13.4 min 3 min 1.1 min min Combined C for Rational Method Area SF C SfxC Roof 2875.4 0.9 2587.86 Pavement 12279.9 0.9 11051.91 Lawn (A hydrologic Group)2253.7 0.1 225.37 Woodland (Primarily Steep)5651 0.25 1412.75 Totals 23060 15277.89 Weighted C 0.663 Ca =1 4.3 in/hr Q=1.51 CF/S t3 = travel time for channel flow, min Bottom width, b = Cross-Sect. Area, A =ft2 Depth of flow, d = Wetted Perimeter, P = Side Slope, z = Hydraulic Radius, R = ( Horiz:Vert = z:1 ) Discharge, Q = Manning roughness, n = Ave. Velocity, V = Channel bottom slope, S = Channel travel time, tchannel = Length of Flow Path, L = ( tc = t1 + t2 + t3 ) t1 = tc = t1b = t1b = t1c = I 10 = d Z 1 b c 2 of 23 Calculation of Overland Sheet Flow Travel Time Pre Construction T02 Using HEC-22 Iterative Process Flow unimproved grass – light underbrush Inputs Calculations Manning Roughness Overland Flow Time 0.4 10.7 min 46 ft Estimated Ti=10.6 min Rational Meth 8.98 <=Try This value 10 yr, I =4.70 in/hr 0.0125 Calculation of Overland Sheet Flow Travel Time Flow Asphalt pavement Inputs Calculations Manning Roughness Overland Flow Time 0.011 1.6 min Use 3 min since chart begins at 5 min, interpolate 52 ft Estimated Ti=5 min Rational Meth 2.20 <=Try This value 6.10 in 0.005 Calculation of Shallow Concentrated Flow Travel Time Equations for NCRS Method for Shallow Concentrated Flow Using the NCRS Method - U.S. units Inputs Calculations 104 ft For unpaved surface: 0.016 2.06 ft/sec 0.8 min where: L = length of the flow path, ft For paved surface:V = shallow concentrated flow velocity, ft/sec S = surface slope, ft/ft 2.60 ft/sec 0.7 min Calculation of Channnel Flow Travel Time Using the Manning Equation - U.S. units For a Trapezoidal Channel Cross-section Inputs Calculations 0.1 ft 0.0 V = Q/A 0.33 ft 0.8 ft R = A/P 0.055 0.05 ft 0.01 cfs 0.011 Where:Q = channel flow rate, cfs 0.324 ft/sec V = average velocity of flow, ft/sec 0.0003 ft/ft 3.9 min P = wetted perimeter of channel, ft 75 ft S = channel bottom slope, ft/ft n = Manning roughness coefficient for channel L = Length of Flow Path, ft Coefficient, n = Travel, t1 = Length of Flow Path, L = Ground Slope, S = Coefficient, n = Travel, t1 = Length of Flow Path, L = 10 yr, I = Ground Slope, S = t1c = L/(60V) for unpaved surface: V = 16.1345S0.5 Length of Flow Path, L = for paved surface: V = 20.3282S0.5 Ground Slope, S =Flow Velocity, V = Travel time, t2 =t2 = shallow concentrated flow runoff travel time, min Flow Velocity, V = Travel time, t2 = Bottom width, b = Cross-Sect. Area, A =ft2 Depth of flow, y = Wetted Perimeter, P = Side Slope, z = Hydraulic Radius, R = ( H:V = z:1 )t1d = L/(60V) Discharge, Q = Manning roughness, n = Ave. Velocity, V = Channel bottom slope, S =A = channel cross-sectional area, ft2 Channel travel time, tchannel = Length of Flow Path, L = c 3 of 23 Calculation of Channnel Flow Travel Time Using the Manning Equation - U.S. units For a Triangilar Channel Cross-section Inputs Calculations 2 ft 1.64 0.33 ft 8.3 ft 18 0.20 ft 4.65 cfs 0.011 2.838 ft/sec 0.0038 ft/ft 0.6 min 100 ft Calculation of Time of Concentration Inputs ( values from above)Calculations 10.7 min 15 min 3 min 0.7 min 0.6 min Combined C for Rational Method Area SF C HSG SfxC Roof 2875.4 0.9 NA 2587.86 Pavement 12279.9 0.9 NA 11051.91 Lawn (A hydrologic Group)2253.7 0.1 A 225.37 Woodland (Primarily Steep)5651 0.25 B 1412.75 Totals 23060 15277.89 Weighted C 0.663 Ca =1 4.1 in/hr Q=1.44 CF/S USE THIS ROUTE t3 = travel time for channel flow, min Bottom width, b = Cross-Sect. Area, A =ft2 Depth of flow, d = Wetted Perimeter, P = Side Slope, z = Hydraulic Radius, R = ( Horiz:Vert = z:1 ) Discharge, Q = Manning roughness, n = Ave. Velocity, V = Channel bottom slope, S = Channel travel time, tchannel = Length of Flow Path, L = ( tc = t1 + t2 + t3 ) t1 = tc = t1b = t1b = t1c = I 10 = d Z 1 b c 4 of 23 Calculation of Overland Sheet Flow Travel Time Post Construction T1 Using HEC-22 Iterative Process Flow Grass Dense Inputs Calculations Manning Roughness Overland Flow Time 0.24 13.3 min 100 ft Estimated Ti=13 min Rational Meth 10.17 <=Try This value 10 yr, I =4.10 in/hr 0.0125 Calculation of Overland Sheet Flow Travel Time Flow Asphalt pavement Inputs Calculations Manning Roughness Overland Flow Time 0.011 0.0 min Use 3 min since chart begins at 5 min, interpolate 0 ft Estimated Ti=5 min Rational Meth 0.00 <=Try This value 6.00 in 0.005 Calculation of Shallow Concentrated Flow Travel Time Equations for NCRS Method for Shallow Concentrated Flow Using the NCRS Method - U.S. units Inputs Calculations 21 ft For unpaved surface: 0.013 1.80 ft/sec 0.19 min where: L = length of the flow path, ft For paved surface:V = shallow concentrated flow velocity, ft/sec S = surface slope, ft/ft 2.2727619 ft/sec 0.2 min Calculation of Shallow Concentrated Flow Travel Time Using the NCRS Method - U.S. units Inputs Calculations 117 ft For unpaved surface: 0.011 1.69 ft/sec 1.2 min For paved surface: 2.1320396 ft/sec 0.9 min Calculation of Channnel Flow Travel Time Using the Manning Equation - U.S. units Coefficient, n = Travel, t1 = Length of Flow Path, L = Ground Slope, S = Coefficient, n = Travel, t1 = Length of Flow Path, L = 10 yr, I = Ground Slope, S = t1c = L/(60V) for unpaved surface: V = 16.1345S0.5 Length of Flow Path, L = for paved surface: V = 20.3282S0.5 Ground Slope, S =Flow Velocity, V = Travel time, t2 =t2 = shallow concentrated flow runoff travel time, min Flow Velocity, V = Travel time, t2 = Length of Flow Path, L = Ground Slope, S =Flow Velocity, V = Travel time, t2 = Flow Velocity, V = Travel time, t2 = c 5 of 23 For a Trapezoidal Channel Cross-section Inputs Calculations 0.1 ft 0.0 V = Q/A 0.33 ft 0.8 ft R = A/P 0.055 0.05 ft 0.01 cfs 0.011 Where:Q = channel flow rate, cfs 0.324 ft/sec V = average velocity of flow, ft/sec 0.0003 ft/ft 3.9 min P = wetted perimeter of channel, ft 75 ft S = channel bottom slope, ft/ft n = Manning roughness coefficient for channel L = Length of Flow Path, ft Calculation of Channnel Flow Travel Time Using the Manning Equation - U.S. units For a Triangilar Channel Cross-section Inputs Calculations 2 ft 1.64 0.33 ft 8.3 ft 18 0.20 ft 4.65 cfs 0.011 2.838 ft/sec 0.0038 ft/ft 0.6 min 100 ft Calculation of Time of Concentration Inputs ( values from above)Calculations 13.3 min 14.39 min 0.19 min 0.9 min min Combined C for Rational Method Area SF C SfxC Roof 2875.4 0.9 2587.86 Pavement 12279.9 0.9 11051.91 Lawn (A hydrologic Group)2253.7 0.1 225.37 Woodland (Primarily Steep)5651 0.25 1412.75 Totals 23060 15277.89 Weighted C 0.663 Ca =1 4.05 in/hr Q=1.42 CF/S Bottom width, b = Cross-Sect. Area, A =ft2 Depth of flow, y = Wetted Perimeter, P = Side Slope, z = Hydraulic Radius, R = ( H:V = z:1 )t1d = L/(60V) Discharge, Q = Manning roughness, n = Ave. Velocity, V = Channel bottom slope, S =A = channel cross-sectional area, ft2 Channel travel time, tchannel = Length of Flow Path, L = t3 = travel time for channel flow, min Bottom width, b = Cross-Sect. Area, A =ft2 Depth of flow, d = Wetted Perimeter, P = Side Slope, z = Hydraulic Radius, R = ( Horiz:Vert = z:1 ) Discharge, Q = Manning roughness, n = Ave. Velocity, V = Channel bottom slope, S = Channel travel time, tchannel = Length of Flow Path, L = ( tc = t1 + t2 + t3 ) t1 = tc = t1b = t1b = t1c = I 10 = d Z 1 b c 6 of 23 Calculation of Overland Sheet Flow Travel Time Post Construction T2 Using HEC-22 Iterative Process Flow Grass Dense Inputs Calculations Manning Roughness Overland Flow Time 0.24 13.3 min 100 ft Estimated Ti=13 min Rational Meth 10.17 <=Try This value 10 yr, I =4.10 in/hr 0.0125 Calculation of Overland Sheet Flow Travel Time Flow Asphalt pavement Inputs Calculations Manning Roughness Overland Flow Time 0.011 0.0 min Use 3 min since chart begins at 5 min, interpolate 0 ft Estimated Ti=5 min Rational Meth 0.00 <=Try This value 6.00 in 0.005 Calculation of Shallow Concentrated Flow Travel Time Equations for NCRS Method for Shallow Concentrated Flow Using the NCRS Method - U.S. units Inputs Calculations 105 ft For unpaved surface: 0.011 1.69 ft/sec 1.03 min where: L = length of the flow path, ft For paved surface:V = shallow concentrated flow velocity, ft/sec S = surface slope, ft/ft 2.1320396 ft/sec 0.82 min Calculation of Shallow Concentrated Flow Travel Time Using the NCRS Method - U.S. units Inputs Calculations 117 ft For unpaved surface: 0.013 1.83 ft/sec 1.1 min For paved surface: 2.3017154 ft/sec 0.8 min Calculation of Channnel Flow Travel Time Using the Manning Equation - U.S. units Coefficient, n = Travel, t1 = Length of Flow Path, L = Ground Slope, S = Coefficient, n = Travel, t1 = Length of Flow Path, L = 10 yr, I = Ground Slope, S = t1c = L/(60V) for unpaved surface: V = 16.1345S0.5 Length of Flow Path, L = for paved surface: V = 20.3282S0.5 Ground Slope, S =Flow Velocity, V = Travel time, t2 =t2 = shallow concentrated flow runoff travel time, min Flow Velocity, V = Travel time, t2 = Length of Flow Path, L = Ground Slope, S =Flow Velocity, V = Travel time, t2 = Flow Velocity, V = Travel time, t2 = c 7 of 23 For a Trapezoidal Channel Cross-section Inputs Calculations 0.1 ft 0.0 V = Q/A 0.33 ft 0.8 ft R = A/P 0.055 0.05 ft 0.01 cfs 0.011 Where:Q = channel flow rate, cfs 0.324 ft/sec V = average velocity of flow, ft/sec 0.0003 ft/ft 3.9 min P = wetted perimeter of channel, ft 75 ft S = channel bottom slope, ft/ft n = Manning roughness coefficient for channel L = Length of Flow Path, ft Calculation of Channnel Flow Travel Time Using the Manning Equation - U.S. units For a Triangilar Channel Cross-section Inputs Calculations 0.1 ft 1.01 0.33 ft 6.4 ft 18 0.16 ft 2.48 cfs 0.011 2.449 ft/sec 0.0038 ft/ft 0.7 min 100 ft Calculation of Time of Concentration Inputs ( values from above)Calculations 13.3 min 15.03 min 1.03 min 0.7 min min Combined C for Rational Method Area SF C HSG SfxC Roof 2875.4 0.9 NA 2587.86 Pavement 12279.9 0.9 NA 11051.91 Lawn (A hydrologic Group)2253.7 0.1 A 225.37 Woodland (Primarily Steep)5651 0.25 B 1412.75 Totals 23060 15277.89 Weighted C 0.663 Ca =1 4 in/hr Q=1.40 CF/S USE THIS ROUTE Bottom width, b = Cross-Sect. Area, A =ft2 Depth of flow, y = Wetted Perimeter, P = Side Slope, z = Hydraulic Radius, R = ( H:V = z:1 )t1d = L/(60V) Discharge, Q = Manning roughness, n = Ave. Velocity, V = Channel bottom slope, S =A = channel cross-sectional area, ft2 Channel travel time, tchannel = Length of Flow Path, L = t3 = travel time for channel flow, min Bottom width, b = Cross-Sect. Area, A =ft2 Depth of flow, d = Wetted Perimeter, P = Side Slope, z = Hydraulic Radius, R = ( Horiz:Vert = z:1 ) Discharge, Q = Manning roughness, n = Ave. Velocity, V = Channel bottom slope, S = Channel travel time, tchannel = Length of Flow Path, L = ( tc = t1 + t2 + t3 ) t1 = tc = t1b = t1b = t1c = I 10 = d Z 1 b c 8 of 23 2006 EDITION 8-30 Drainage and Erosion Control January 2006 Exhibit 8-15 Intensity – Duration – Frequency Curve for Springfield, MA Source: TR55 - Urban Hydrology for Small Wetlands, NRCS 9 of 23 2006 EDITION 8-24 Drainage and Erosion Control January 2006 Exhibit 8-8 Recommended Runoff Coefficients (C) for Rational Method (By Overall Character of Area) Description of Area Runoff Coefficients Business Downtown Neighborhood 0.70 to 0.95 0.50 to 0.70 Residential Single-Family Multi-Family, Detached Multi-Family, Attached 0.30 to 0.50 0.40 to 0.60 0.60 to 0.75 Residential (Suburban) 0.25 to 0.40 Apartment 0.50 to 0.70 Industrial Light Heavy 0.50 to 0.80 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 Source: Design Manual for Storm Drainage, ASCE 1960 Exhibit 8-9 Recommended Runoff Coefficients (C) For Rational Method (For Surface Type) Character of Surface Runoff Coefficients Pavement Asphaltic and Concrete Brick 0.70 to 0.95 0.70 to 0.85 Roofs 0.75 to 0.95 Lawns, Sandy Soil Flat, 2 Percent Average, 2 to 7 Percent Steep, 7 Percent 0.05 to 0.10 0. 10 to 0.15 0.15 to 0.20 Lawns, Heavy Soil Flat, 2 Percent Average, 2 to 7 Percent Steep, 7 Percent 0.13 to 0.17 0.18 to 0.22 0.25 to 0.35 Source: Design Manual for Storm Drainage, ASCE 1960 10 of 23 2006 EDITION January 2006 Drainage and Erosion Control 8-25 Exhibit 8-10 Recommended Ca Values (Rational Method) (For Greater Than 10-year Design Runoff) Recurrence Interval (Years) Ca 2 to 10 1.0 25 1.1 50 1.2 100 1.25 Note: The product of C x Ca should not exceed 1. Source: WPCF Manual of Practice No. 9, Design and Construction of Sanitary and Storm Sewers. Rainfall Intensity (I; in inches/hour) Rainfall intensity in the Rational Method is a function of: 1) selection of design flood frequency (see Exhibit 8-2) and 2) time of concentration (Tc), or the time required for the runoff to travel from the hydraulically most distant part of the watershed to the design site. It is usually computed by determining the water travel time through the watershed. The hydraulically most distant location will not necessarily be the linearly most distant site. To determine i, follow this procedure: „ To calculate Tc, use Exhibit 8-11. For pavements Tc is normally assumed to be 5 minutes for the first inlet only. Tc is based on the slope of the water course and the type of surface cover. The designer should check several overland watercourses or flow routes to determine Tc. See the example for a Tc calculation. For an alternate method for computing Tc, the designer should refer to the procedure in FHWA-NHI-01-021 Urban Drainage Design Manual (HEC-22). „ Exhibits 8-12 to 8-16 provide intensity-duration-frequency (I-D-F) curves for Boston, Barnstable, Worcester, Springfield, and Pittsfield. The designer should select the station closest to the design site. „ Enter the selected I-D-F curve with the calculated Tc and turn at the selected design flood frequency. Read i from the vertical axis. 11 of 23 Soil Map—Hampshire County, Massachusetts, Central Part (227 South Street, Northampton, MA) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 1 of 34686860468687046868804686890468690046869104686920468693046869404686950468696046869704686980468699046870004687010468687046868804686890468690046869104686920468693046869404686950468696046869704686980468699046870004687010694630694640694650694660694670694680694690694700694710694720694730694740 694630 694640 694650 694660 694670 694680 694690 694700 694710 694720 694730 694740 42° 18' 39'' N 72° 38' 18'' W42° 18' 39'' N72° 38' 13'' W42° 18' 34'' N 72° 38' 18'' W42° 18' 34'' N 72° 38' 13'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS84 0 35 70 140 210 Feet 0 10 20 40 60 Meters Map Scale: 1:768 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. 12 of 23 MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout 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 Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:15,800. 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 Service Web 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: Hampshire County, Massachusetts, Central Part Survey Area Data: Version 12, Oct 6, 2017 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Sep 29, 2013—Oct 16, 2016 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. Soil Map—Hampshire County, Massachusetts, Central Part (227 South Street, Northampton, MA) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 2 of 313 of 23 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 225B Belgrade silt loam, 3 to 8 percent slopes 0.6 36.7% 254A Merrimac fine sandy loam, 0 to 3 percent slopes 0.7 42.0% 745C Hinckley-Merrimac-Urban land complex, 3 to 15 percent slopes 0.3 21.3% Totals for Area of Interest 1.6 100.0% Soil Map—Hampshire County, Massachusetts, Central Part 227 South Street, Northampton, MA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 3 of 3 14 of 23 Hydrologic Soil Group and Surface Runoff This table gives estimates of various soil water features. The estimates are used in land use planning that involves engineering considerations. Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The four hydrologic soil groups are: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Surface runoff refers to the loss of water from an area by flow over the land surface. Surface runoff classes are based on slope, climate, and vegetative cover. The concept indicates relative runoff for very specific conditions. It is assumed that the surface of the soil is bare and that the retention of surface water resulting from irregularities in the ground surface is minimal. The classes are negligible, very low, low, medium, high, and very high. Report—Hydrologic Soil Group and Surface Runoff Absence of an entry indicates that the data were not estimated. The dash indicates no documented presence. Hydrologic Soil Group and Surface Runoff–Hampshire County, Massachusetts, Central Part Map symbol and soil name Pct. of map unit Surface Runoff Hydrologic Soil Group 225B—Belgrade silt loam, 3 to 8 percent slopes Belgrade 85 Low C Hydrologic Soil Group and Surface Runoff---Hampshire County, Massachusetts, Central Part 227 South Street, Northampton, MA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 1 of 2 15 of 23 Hydrologic Soil Group and Surface Runoff–Hampshire County, Massachusetts, Central Part Map symbol and soil name Pct. of map unit Surface Runoff Hydrologic Soil Group 254A—Merrimac fine sandy loam, 0 to 3 percent slopes Merrimac 85 Very low A 745C—Hinckley-Merrimac-Urban land complex, 3 to 15 percent slopes Hinckley 30 Very low A Merrimac 25 Very low A Urban land 25 Very high D Data Source Information Soil Survey Area: Hampshire County, Massachusetts, Central Part Survey Area Data: Version 12, Oct 6, 2017 Hydrologic Soil Group and Surface Runoff---Hampshire County, Massachusetts, Central Part 227 South Street, Northampton, MA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 2 of 2 16 of 23 Saturated Hydraulic Conductivity (Ksat), Standard Classes—Hampshire County, Massachusetts, Central Part (227 South Street, Northampton, MA) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 1 of 44686860468687046868804686890468690046869104686920468693046869404686950468696046869704686980468699046870004687010468687046868804686890468690046869104686920468693046869404686950468696046869704686980468699046870004687010694630694640694650694660694670694680694690694700694710694720694730694740 694630 694640 694650 694660 694670 694680 694690 694700 694710 694720 694730 694740 42° 18' 39'' N 72° 38' 18'' W42° 18' 39'' N72° 38' 13'' W42° 18' 34'' N 72° 38' 18'' W42° 18' 34'' N 72° 38' 13'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS84 0 35 70 140 210 Feet 0 10 20 40 60 Meters Map Scale: 1:768 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. 17 of 23 MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons Very Low (0.0 - 0.01) Low (0.01 - 0.1) Moderately Low (0.1 - 1) Moderately High (1 - 10) High (10 - 100) Very High (100 - 705) Not rated or not available Soil Rating Lines Very Low (0.0 - 0.01) Low (0.01 - 0.1) Moderately Low (0.1 - 1) Moderately High (1 - 10) High (10 - 100) Very High (100 - 705) Not rated or not available Soil Rating Points Very Low (0.0 - 0.01) Low (0.01 - 0.1) Moderately Low (0.1 - 1) Moderately High (1 - 10) High (10 - 100) Very High (100 - 705) Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:15,800. 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 Service Web 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: Hampshire County, Massachusetts, Central Part Survey Area Data: Version 12, Oct 6, 2017 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Sep 29, 2013—Oct 16, 2016 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. Saturated Hydraulic Conductivity (Ksat), Standard Classes—Hampshire County, Massachusetts, Central Part (227 South Street, Northampton, MA) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 2 of 418 of 23 Saturated Hydraulic Conductivity (Ksat), Standard Classes Map unit symbol Map unit name Rating (micrometers per second) Acres in AOI Percent of AOI 225B Belgrade silt loam, 3 to 8 percent slopes 9.1700 0.6 36.7% 254A Merrimac fine sandy loam, 0 to 3 percent slopes 100.0000 0.7 42.0% 745C Hinckley-Merrimac- Urban land complex, 3 to 15 percent slopes 100.0000 0.3 21.3% Totals for Area of Interest 1.6 100.0% Description Saturated hydraulic conductivity (Ksat) refers to the ease with which pores in a saturated soil transmit water. The estimates are expressed in terms of micrometers per second. They are based on soil characteristics observed in the field, particularly structure, porosity, and texture. Saturated hydraulic conductivity is considered in the design of soil drainage systems and septic tank absorption fields. For each soil layer, this attribute is actually recorded as three separate values in the database. A low value and a high value indicate the range of this attribute for the soil component. A "representative" value indicates the expected value of this attribute for the component. For this soil property, only the representative value is used. The numeric Ksat values have been grouped according to standard Ksat class limits. The classes are: Very low: 0.00 to 0.01 Low: 0.01 to 0.1 Moderately low: 0.1 to 1.0 Moderately high: 1 to 10 High: 10 to 100 Very high: 100 to 705 Rating Options Units of Measure: micrometers per second Aggregation Method: Dominant Component Saturated Hydraulic Conductivity (Ksat), Standard Classes—Hampshire County, Massachusetts, Central Part 227 South Street, Northampton, MA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 3 of 4 19 of 23 Component Percent Cutoff: None Specified Tie-break Rule: Fastest Interpret Nulls as Zero: No Layer Options (Horizon Aggregation Method): Depth Range (Weighted Average) Top Depth: 20 Bottom Depth: 40 Units of Measure: Inches Saturated Hydraulic Conductivity (Ksat), Standard Classes—Hampshire County, Massachusetts, Central Part 227 South Street, Northampton, MA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 4 of 4 20 of 23 K Factor, Rock Free—Hampshire County, Massachusetts, Central Part (227 South Street, Northampton, MA) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 1 of 34686860468687046868804686890468690046869104686920468693046869404686950468696046869704686980468699046870004687010468687046868804686890468690046869104686920468693046869404686950468696046869704686980468699046870004687010694630694640694650694660694670694680694690694700694710694720694730694740 694630 694640 694650 694660 694670 694680 694690 694700 694710 694720 694730 694740 42° 18' 39'' N 72° 38' 18'' W42° 18' 39'' N72° 38' 13'' W42° 18' 34'' N 72° 38' 18'' W42° 18' 34'' N 72° 38' 13'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS84 0 35 70 140 210 Feet 0 10 20 40 60 Meters Map Scale: 1:768 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. 21 of 23 MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons .02 .05 .10 .15 .17 .20 .24 .28 .32 .37 .43 .49 .55 .64 Not rated or not available Soil Rating Lines .02 .05 .10 .15 .17 .20 .24 .28 .32 .37 .43 .49 .55 .64 Not rated or not available Soil Rating Points .02 .05 .10 .15 .17 .20 .24 .28 .32 .37 .43 .49 .55 .64 Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:15,800. 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 Service Web 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: Hampshire County, Massachusetts, Central Part Survey Area Data: Version 12, Oct 6, 2017 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Sep 29, 2013—Oct 16, 2016 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. K Factor, Rock Free—Hampshire County, Massachusetts, Central Part (227 South Street, Northampton, MA) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 2 of 322 of 23 K Factor, Rock Free Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 225B Belgrade silt loam, 3 to 8 percent slopes .43 0.6 36.7% 254A Merrimac fine sandy loam, 0 to 3 percent slopes .28 0.7 42.0% 745C Hinckley-Merrimac- Urban land complex, 3 to 15 percent slopes 0.3 21.3% Totals for Area of Interest 1.6 100.0% Description Erosion factor K indicates the susceptibility of a soil to sheet and rill erosion by water. Factor K is one of six factors used in the Universal Soil Loss Equation (USLE) and the Revised Universal Soil Loss Equation (RUSLE) to predict the average annual rate of soil loss by sheet and rill erosion in tons per acre per year. The estimates are based primarily on percentage of silt, sand, and organic matter and on soil structure and saturated hydraulic conductivity (Ksat). Values of K range from 0.02 to 0.69. Other factors being equal, the higher the value, the more susceptible the soil is to sheet and rill erosion by water. "Erosion factor Kf (rock free)" indicates the erodibility of the fine-earth fraction, or the material less than 2 millimeters in size. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Layer Options (Horizon Aggregation Method): Surface Layer (Not applicable) K Factor, Rock Free—Hampshire County, Massachusetts, Central Part 227 South Street, Northampton, MA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2018 Page 3 of 3 23 of 23