Stormwater Report Notice of Intent (NOI)

Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA MassDOT Project No. 604597

February 2018

Prepared for: MassDOT—Highway Division 10 Park Plaza Boston, MA 02116

Prepared by: Michael J. Rieger, PE TranSystems 101 Arch Street, Suite 301 Boston, MA 02110

TABLE OF CONTENTS

GENERAL PROJECT DESCRIPTION ...... 2 RECEIVING WATER BODY ...... 3 EXISTING CONDITIONS...... 3 PROPOSED IMPROVEMENTS ...... 4 COMPLIANCE WITH THE TEN STORMWATER MANAGEMENT STANDARDS ...... 6 Standard 1- No New Untreated Discharges ...... 6 Standard 2- Peak Rate Attenuation ...... 6 Standard 3- Groundwater Recharge ...... 8 Standard 4- TSS Removal and Long-Term Pollution Prevention Plan ...... 9 Standard 5- Higher Potential Pollutant Loads ...... 11 Standard 6- Critical Areas ...... 11 Standard 7- Redevelopment ...... 11 Standard 8- Construction Period Pollution Prevention and Erosion Control Plan ...... 11 Standard 9- Operation and Maintenance Plan ...... 11 Standard 10- Illicit Discharge Prevention ...... 12

Attachment A- Checklist for Stormwater Report ...... A-1 - A-8 Attachment B- NRCS Soil Survey...... B-1 - B-4 Attachment C- Existing and Proposed Catchment Maps ...... C-1 - C-2 Attachment D- Splash Pad Sizing Calculations ...... D-1 Attachment E- BMP Calculations ...... E-1 - E-3 Attachment F- Peak Rate Attenuation Modeling Output ...... F-1 - F-99 Attachment G- Test Pit Logs ...... G-1 - G-8 Attachment H- Long Term Pollution Prevention Plan (LTPPP) ...... H-1 - H-4 Attachment I- Operation and Maintenance Plan (O&M Plan) ...... I-1 - I-2

GENERAL PROJECT DESCRIPTION The Massachusetts Department of Transportation – Highway Division (MassDOT) is proposing improvements to the intersection of Route 9 (Bridge Street) and Damon Road in the city of Northampton (Project). The Project evolved from a regional transportation study that evaluated the potential need for an additional bridge over the Connecticut River. The study determined that no additional bridge is required, but instead recommended improved traffic operations at Interchange 19 of I-91. The Project is located just west of the Calvin Coolidge Memorial Bridge spanning the Connecticut River. It includes the intersection of Bridge Street and Damon Road/I-91 northbound (NB) off-ramp, and the intersection of Bridge Street and the I-91 southbound (SB) on-ramp. Figure 1 shows the project locus map. Figure 1 Locus Map

PROJECT LOCATION

The designed improvements include reconstruction of the intersection of Route 9 with the NB off- ramp and Damon Road as a two-lane roundabout with a 10-foot wide shared-use path. The SB on- ramp will be widened to two lanes prior to the merge with I-91. Both the NB off-ramp and the SB on-ramp will be lengthened to accommodate longer deceleration and acceleration lanes. The proposed stormwater management design includes two Best Management Practices (BMPs), which

2 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

are both infiltration basins. These infiltration basins will be located between the NB off-ramp and I- 91 and the SB on-ramp and I-91, respectively. Access for maintenance will be from Route 9. The proposed stormwater BMPs are described in more detail in the Proposed Improvements section of this report. Descriptions of how the Project complies with the Massachusetts Stormwater Standards are included in the section titled, Compliance with the Ten Stormwater Management Standards. Attachment A includes a stamped and signed Massachusetts Department of Environmental Protection Checklist for Stormwater Report. RECEIVING WATER BODY The Connecticut River flows from north to south, east of the Project site, and is listed in the Massachusetts Year 2012 Integrated List of Waters as impaired for Escherichia coli and PCB in Fish Tissue. No Total Maximum Daily Loads (TMDLs) have been reported to the United States Environmental Protection Agency (US EPA) by the Massachusetts Department of Environmental Protection (MassDEP) for the Connecticut River watershed. Stormwater from the project site enters the river via closed drainage systems. EXISTING CONDITIONS I-91 is the primary north-south thoroughfare through western New England beginning in New Haven, Connecticut at I-95 and terminating at the Canadian border in Derby Line, Vermont. The divided, limited-access highway generally follows the Connecticut River and has two lanes in each direction. Route 9, which runs in the east-west direction through Northampton, is a two-lane roadway that widens to four lanes plus turning lanes through the signalized intersection with I-91. Route 9 is a primary access route to the main campus of the University of Massachusetts at Amherst. The Calvin Coolidge Bridge carries Route 9 over the Connecticut River into Hadley, MA. The Norwottuck Rail Trail also crosses the Connecticut River just north of the project site. Damon Road runs parallel to I-91, on the north side of Route 9, between I-91 and the Connecticut River.

Commercial properties occupy the west side of Damon Road near its intersection with Route 9. The Elwell Recreation Area of the Connecticut River Greenway State Park lies on the east side of Damon Road, along the western bank of the Connecticut River. A residential neighborhood of single family houses populates the area west and northwest of the project site. Agricultural land occupies both sides of I-91 on the south side of Exit 19. The project site within the limit of proposed work is currently 45% impervious.

I-91 crosses over Route 9 with a high point in the profile just north of the project site. Route 9 generally rises to the east towards the Calvin Coolidge Bridge. On the west side of I-91, the neighborhood north of the project site gradually rises higher than Route 9. On the east side of I-91, the commercial properties and parkland gradually drop lower than Route 9. South of Route 9, the topography drops about ten feet at roughly a 15 percent grade on both sides of I-91, before reaching relatively flat agricultural land. One catch basin on the I-91 off-ramp and the infield area between the I-91 off-ramp and I-91discharge runoff into the woods west of the I-91 off ramp (an 18” culvert crosses under the off-ramp). All other runoff from the site is collected by an existing closed drainage network that discharges to the Connecticut River, through either a 24-inch outfall 25 feet south of the Calvin Coolidge Bridge, a 30-inch outfall 80 feet south of the Calvin Coolidge Bridge, or an 18-inch outfall 45 feet south of the bridge for the Norwottuck Rail Trail.

3 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

Attachment B includes a Hydrologic Soil Group (HSG) Web Soil Survey from the National Resource Conservation Service (NRCS) that summarizes the area coverage for each soil type. Although a portion of the site has no HSG available, the HSG can be assumed to match the surrounding soil types, which is Hydrologic Soil Group B. Therefore, all soils within the limit of work of the Project are classified as Hydrologic Soil Group B for the purposes of this stormwater report. Attachment C shows an existing catchment map, with labels for total area, weighted average curve number (CN) and time of concentration. The CN values used for existing conditions are taken from Exhibit 8-18 from the 2006 MassDOT design guide. The value used for woods along I-91 is 55 (Good condition). The value used for grass throughout the site is 61 (Good condition). The value used for impervious area is 98. All catchment areas have times of concentration less than the minimum five minutes.

Runoff from most of Route 9 and both barrels of I-91 north of Route 9 is designated as Catchment A and discharges to the 24-inch outfall. The infield area between I-91 and the NB off-ramp is Catchment B. The lower ends of the NB off-ramp and SB on-ramp, plus both barrels of I-91 south of Route 9, form Catchment C. Runoff from the middle section of the NB off-ramp is designated as Catchment D. The north end of the NB off-ramp and the eastbound side of Route 9 to the Calvin Coolidge Bridge is Catchment E. Catchment G includes both barrels of I-91, south of the ramp gores. These catchments combine and discharge to the 30-inch outfall.

Catchment H represents Damon Road runoff that discharges to the 18-inch outfall south of the Rail Trail.

Catchment K is the wooded area adjacent to NB off-ramp. Catchment F is the wooded area adjacent to SB on-ramp and also includes runoff from one catch basin on the SB-on ramp and the infield area between I-91 and the SB on-ramp (which also receives flow from one catch basin located on I-91 SB). PROPOSED IMPROVEMENTS The Project proposes the following improvements over existing conditions:

 Deep sump catch basins  Forebays with Infiltration basins (Infiltration Basin B and Infiltration Basin J)

All runoff is captured by deep sump catch basins, which improve upon existing conditions by removing more suspended solids and debris than existing standard catch basins.

The proposed closed drainage system is designed to adhere to the MassDOT design guide including criteria for spread (ponding) at inlets, pipe sizing, and hydraulic grade line calculations. Calculations for the closed drainage system will be included with the 100% design submittal.

Infiltration Basin B, proposed in the infield area between I-91 and the I-91 NB off-ramp, includes a forebay for pretreatment removal of debris. From the wetland forebay, runoff spills over a stone weir to a flat depression that is loamed and seeded to allow for infiltration. The basin holds and infiltrates the required water quality and recharge volumes. An outlet control structure with a 12 inch orifice and grate is proposed to mitigate peak flow rates during the 2 and 10 year storm events. The volume of storage below the orifice is the calculated recharge volume, and will drawdown

4 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

within 72 hours. The outlet control structure allows the basin to have a minimum of one foot of freeboard during the 100 year storm event.

Infiltration Basin J, proposed in the infield area between I-91 and the I-91 SB on-ramp, includes a forebay for pretreatment removal of debris. From the wetland forebay, runoff spills over a stone weir to a flat depression that is loamed and seeded to allow for infiltration. The basin holds and infiltrates the required water quality and recharge volumes. In addition the basin holds the 2 year storm. An overflow stone weir is proposed to mitigate the 10 and 100 year storm events. The volume of storage below the weir elevation is the calculated recharge volume, and will drawdown within 72 hours.

Attachment C shows a proposed catchment map, with labels for total area, weighted average curve number and time of concentration. The method for estimating runoff rates within the proposed catchments uses the same parameters as those used for existing conditions, with the exception that for the proposed conditions, the existing woods along I-91 are proposed to be cleared and grubbed. The existing 2:1 (H:V) side slopes will be loamed and seeded to allow for permanent erosion control and slope stabilization. These slopes are categorized as Grass with a CN value of 61. The proposed outside edges of the re-aligned 91 NB off-ramp and SB on-ramp will be Mechanically Stabilized Earth (MSE) which yields a 1:1 slope. The slope will grow brush over time. The CN value used is 48, which is categorized as brush-weed-grass mixture with brush the major element (good cover). These walls are proposed to allow for flood storage at the bottom of the slope. The bottom of the slopes are categorized as Woods – grass combination with good cover, which has a CN value of 58.

Runoff from most of Route 9 and both barrels of I-91 north of Route 9 continues to discharge to the 24-inch outfall as Catchment A, while Catchment J represents the north end of the SB on-ramp that discharges to the proposed Infiltration Basin J. The infield area between I-91 and the SB on-ramp that is not occupied by the infiltration basin remains designated as a part of Catchment F. Likewise, the Damon Road runoff remains designated as Catchment H. The proposed condition reduces the sizes of Catchment A, Catchment F, and Catchment H, as compared to their existing condition counterparts.

Catchment F and Catchment K discharge adjacent to SB on-ramp and NB off-ramp, respectively. The respective areas each decrease in size from existing conditions, and the peak flow rates are mitigated by replacing the existing woods with MSE walls which will fill out with brush once permanent erosion stabilization is established.

All remaining catchment areas still discharge to the 30-inch outfall. Although the combined area of the remaining proposed catchment areas is larger than existing conditions, extended detention storage is included within the Infiltration Basin B area to mitigate peak flow rates. The majority of the proposed roundabout and both sides of Route 9 east of the roundabout are added to Catchment B, which discharges to the infiltration basin. Catchment B includes the area previously designated as existing Catchment E, therefore the proposed condition has no proposed Catchment E. The middle section of the NB off-ramp remains designated as Catchment D, and is slightly smaller than the existing Catchment D. The proposed Catchment C and Catchment G are moderately expanded in size, due to the roadway geometry that is required for the designed traffic and safety improvements.

5 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

COMPLIANCE WITH THE TEN STORMWATER MANAGEMENT STANDARDS The following low impact design (LID) measures are employed for this Project.  No disturbance to any wetland resource areas  Two infiltration basins with sediment forebays  Minimizing disturbance to existing trees and shrubs

The proposed stormwater management design complies with the ten Massachusetts Stormwater Standards.

Standard 1- No New Untreated Discharges This standard requires that the design provide water quality treatment to all proposed stormwater discharges, which improves the water quality of downstream receiving water bodies. The proposed stormwater management design meets the requirements of Standard 1.

All stormwater runoff directed to existing outfalls is treated prior to passage offsite. The different levels of treatment are described in more detail in the description of compliance with Standard 4. The Project does not add any untreated discharges, because no new outfalls are proposed by this project. One outfall entering Catchment F from I-91 is being re-directed in order for Infiltration Basin J to be constructed. See Attachment D for splash pad calculations.

Standard 2- Peak Rate Attenuation This standard requires that the design minimize the downstream impacts of peak flow rates during storm events by detaining stormwater onsite.

The project reduces post construction peak runoff rates to below preconstruction peak runoff rates during the 2-year, 10-year, and 100-year storm events for project discharge points.

The peak rate of runoff is a measure of how rapidly stormwater flows from a catchment area during specific storm events. Peak rates of runoff are reduced by detaining runoff during storm events and releasing the stormwater gradually as the storms subside. Massachusetts Stormwater Management Standard Number 2 requires that the post-construction discharge from a project match the discharge prior to construction, during the 2-year 24-hour and 10-year 24-hour Type III storm events. Standard 2 also requires that the project identify whether or not peak discharges from the 100-year 24-hour Type III storm increase off-site flooding. If increased flooding is found, then the project must attenuate peak flow from the 100-year storm event.

Bentley PondPack V8i pond routing software was employed using the Unit Hydrograph method to route runoff hydrographs through flood storage facilities and to their outlets, compute the peak discharges through outlets, and determine the maximum high water elevation during storm events. This method calculates runoff rate using time of concentration, curve number, catchment acreage, and 24-hr precipitation for the selected return period and rainfall distribution. Rainfall data for the storm events were estimated from the Massachusetts Rainfall Data Maps derived from Technical Paper 40 (1961) and included as Appendix F-1 in the March 2002 Hydrology Handbook for

6 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

Conservation Commissioners. The analysis uses 3.0 inches for the 2-year Type III 24-hour storm event, 4.5 inches for the 10-year, and 6.4 inches for the 100-year Type III 24-hour storm event.

Curve numbers represent the relative permeability of local soil types, with 98 equal to the most impermeable pavement surfaces. Permeable areas are assigned curve numbers according to the hydrologic code of the soil type (A, B, C, or D) and whether it supports enough tree growth to qualify as woods or is covered with grass. As stated previously, all CN values are associated with hydrologic code B for this project.

Times of concentration demonstrate the longest time that it takes runoff to drain from any point in a catchment area to the lowest point. Depending on the characteristics of the flow path, the time of concentration calculation will include some combination of sheet flow, shallow concentrated flow, flow in a pipe, or channel flow. Sheet flow lengths are limited to a maximum 50 feet. Flow in a pipe is conservatively estimated based on the length traveled times an assumed minimum velocity of 3 feet per second, since the project site is very flat. Other characteristics that define the time of concentration, such as slope, length, and Manning’s n are selected based on the actual conditions estimated along the flow path identified. Manning’s n values are selected in accordance with “Table 3-1 Roughness Coefficients (Manning’s n) For Sheet Flow” in 210-VI-TR-55, Second Ed., June 1986, with runoff over pavement, grass, and woods assigned a Manning’s roughness coefficient of 0.01, 0.15, and 0.40, respectively. The minimum time of concentration is five minutes, or 0.083 hours. All existing and proposed catchment areas within the project are found to have times of concentration less than the minimum five minutes.

The project has a variety of design points within the project boundaries, however the five primary discharge points are the following:

 DP – A, a 24” outfall to the Connecticut River  DP – H, an 18” outfall to the Connecticut River  30” outfall to the Connecticut River  DP – F, west side adjacent to Interstate 91 SB on-ramp  DP – K, east side adjacent to Interstate 91 NB off-ramp

As shown in Table 1, the hydrologic model compares post construction runoff rates to preconstruction runoff rates for three different storm events at ten design points. Although flows increase at design points B, C, and G due to the required widening and lengthening of the I-91 on and off ramps, the design points discharging adjacent to the project and the Connecticut River are mitigated by the proposed infiltration basins and reduction in area. To accommodate the added flow generated from catchments B, C and G during a 10 Year storm, an existing 24” pipe will be upsized to a 30” pipe to handle the added flow.

7 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

Table 1 Post-construction Runoff Rates Reduced to Below Pre-construction Rates 2-Year (CFS) 10-Year (CFS) 100-Year (CFS) Design Point PRE POST PRE POST PRE POST DP-A (24” Outfall) 6.66 5.01 11.59 8.84 17.85 13.75 DP-B 0.43 0.23 1.61 2.42 3.51 4.67 DP-C 3.68 3.70 6.71 7.00 10.65 11.32 DP-D 0.44 0.34 0.66 0.52 0.94 0.74 DP-E 1.79 0.00 2.73 0.00 3.91 0.00 DP-F (West of SB off-ramp) 0.77 0.67 3.58 2.52 8.23 5.49 DP-G 7.68 9.03 14.26 16.47 22.84 26.12 DP-H (18” Outfall) 1.81 1.47 2.85 2.38 4.15 3.51 DP-K (East of NB on-ramp) 0.19 0.18 1.68 1.39 4.63 3.68 30” Outfall 13.67 12.79 25.51 24.24 31.33 31.33

Attachment C shows the existing and proposed catchment maps. These maps are intended to show how the existing areas within a catchment change based on the proposed project (I.E. EX-A in existing is PR-A in proposed). These catchments are also shown in Attachment F, which shows the modeling analysis for existing and proposed conditions during each storm event.

The outlet from Infiltration Basin B discharges to a closed drainage network that is well above the elevation of the river, so it is modeled as a free outfall tailwater condition. The infiltration basin holds the 100-year storm event with 15 inches of freeboard. Storms larger than the 100-year storm event overflow into the grate of the outlet control structure. Infiltration basin J holds the 100-year storm event with 13 inches of freeboard. Storms larger than the 100-year storm event overflow over the stone weir and water flows to the area adjacent to SB on-ramp via an existing 18” culvert.

Standard 3- Groundwater Recharge This standard requires that the design encourage stormwater to infiltrate the ground to recharge groundwater. The proposed stormwater management design meets the requirements of Standard 3 to the maximum extent practicable.

The recharge volume required to fully meet Standard 3 is equivalent to the recharge volume currently provided by existing soils that are covered by proposed impervious surfaces, minus the recharge volume that will be provided by removing existing paved surfaces. Attachment E includes the Water Quality and Recharge Summary, which provides a detailed calculation of the Required Recharge Volume. Since all soils within the project limit are classified as HSG B, the Required Recharge Volume is equivalent to the added 41,632 square feet of impervious area, multiplied by 0.35 inches, based on Table 2.3.2. Recharge Target Depth by Hydrologic Soil Group from Volume 3: Documenting Compliance with the Massachusetts Stormwater Management Standards of the Massachusetts Stormwater Handbook. The resulting Required Recharge Volume is 1,214 cubic feet. The proposed design exceeds the minimum Required Recharge Volume by providing 11,853 cubic feet of infiltration volume between each of the proposed infiltration basins. Test pits were conducted in the vicinity of the proposed infiltration basins. Test Pits 1-4 (TP-1, TP-2, TP-3, TP-4)

8 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

are included in Attachment G. Infiltration Basin J has a proposed bottom elevation of 123. Based on TP-1 and TP-2 the existing soil layer at elevation 123 is loamy sand. The saturated hydraulic conductivity for loamy sand from the Rawls Table is 2.41 inches per hour. The resulting drawdown calculation for the basin is 22 hours, which is less than the required 72 hour minimum. Infiltration Basin B has a proposed bottom elevation of 130. Based on TP-3 and TP-4 the existing soil layer at elevation 130 is sandy loam. The saturated hydraulic conductivity for sandy loam from the Rawls Table is 1.02 inches per hour. The resulting drawdown calculation for the basin is 57 hours, which is less than the required 72 hour minimum. It should be noted that there is a layer of loam (based on TP-4) that is 4.8 feet deep (elevation 130.0 and 129.2) that will need to be excavated. Prior to filling with 8 inches of loam borrow, the native sandy loam is required to be tilled to a depth of 18 inches.

Capture area adjustment calculations are not provided to quantify the adjusted minimum storage volume because meeting that design goal for a project of this size and linear character is not practicable.

Standard 4- TSS Removal and Long-Term Pollution Prevention Plan This standard requires that the stormwater design include features to remove sediment from the first flush of runoff, as well as a long-term pollution prevention plan that identifies feasible ways to minimize erosion and the release of sediment over the full operational life of the design. The proposed stormwater management design meets the requirements of Standard 4 to the maximum extent practicable.

A long-term pollution prevention plan is included as Attachment H.

Percent impervious is increased from 45% to 50% for the project. The proposed design includes deep sump catch basins, and two infiltration basins each with a sediment forebay. Deep sump catch basins (DSCB) provide 25% Total Suspended Solids (TSS) removal, and the infiltration basins (IB) with forebays each provide 80% TSS removal. As shown in Table 2 below, the proposed design includes two potential treatment trains. Type A provides 85% TSS removal and Type B provides 25% TSS removal.

Table 2- Percent TSS Removal Treatment Train Type A Treatment Train Type B DSCB 25% 0.75 DSCB 25% 0.75 IB 80% 0.15

Removal 85% 25% Contributing Impervious 2.08 ac. 7.25 ac.

The contributing impervious area of 2.08 acres shown for Treatment Train Type A is the sum of 1.70 acres entering into Infiltration Basin B and 0.38 acres entering into Infiltration Basin J. The contributing impervious area of 7.25 acres includes all catchment areas that will flow into deep sump catch basins and directly into the existing drainage system that will not enter a proposed BMP. The estimated TSS% removal provided by the treatment trains is shown in the following calculation.

9 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

Estimated TSS% Removal = (2.08 ac.* 85% + 7.25 ac.* 25% + 0.79 ac. * 0%) / (10.12 ac.) = 35.4%

The Design TSS% (Minimum) is based on the new (increased) impervious area for the project site. This area is calculated by the area of redevelopment impervious (total proposed impervious area) on site (10.12 acres) and subtracting the existing total impervious area on the site (9.16 acres), yielding 0.96 acres of new impervious.

Design TSS% (Minimum) = (Area of New Impervious) x (80%) / ((Area of New Impervious) + Area of Redevelopment Impervious))

Design TSS% (Minimum) = (0.96 ac. * 80%) / (0.96 ac. + 10.12 ac.) = 6.9%

The estimated TSS% removal of 35.4% is greater than the minimum requirement of 6.9%.

The proposed Infiltration Basin J and Infiltration Basin B are designed to treat the required water quality volume (WQV), as shown in the BMP Calculations Water Quality and Recharge Summary included in Attachment E. The required WQV for each forebay is equivalent to one-tenth inch of rainfall over the contributing impervious drainage area. The required WQV for Infiltration Basin J is equivalent to one inch of rainfall over the contributing impervious drainage area since the layer of infiltration happens in loamy sand having a saturated hydraulic conductivity of 2.41 inches per hour, which is considered a rapid infiltration rate (over 2.40 inches per hour). The required WQV for Infiltration Basin B is equivalent to one-half inch of rainfall over the contributing impervious drainage area since the layer of infiltration happens in sandy loam having a saturated hydraulic conductivity of 1.02 inches per hour, which is not a rapid infiltration rate. Table 3 presents the contributing impervious areas for each treatment Best Management Practice (BMP), calculates the required WQV for each, and includes the water quality volume provided by each BMP. The water quality volume provided is equivalent to the volume of stormwater that is held below the lowest invert out of the basins. The provided WQV exceeds the required WQV in each case.

Table 3- Required Water Quality Volumes Contributing Sensitivity Impervious Required Provided Depth Area WQV WQV Treatment BMP (in.) (sf) (cf) (cf) Forebay for Infiltration Basin B 0.1 73,887 616 875 Infiltration Basin B 0.5 73,887 3,079 7,246 Forebay for Infiltration Basin J 0.1 16,720 140 270 Infiltration Basin J 1.0 16,720 1,394 4,607

10 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

Standard 5- Higher Potential Pollutant Loads This standard requires that the design remove more sediment from land uses with higher potential for pollutant loads such as high traffic parking lots. The proposed stormwater management design meets the requirements of Standard 5.

The drainage system collects stormwater only from land used for vehicle and pedestrian traffic, which does not constitute a land use with higher potential pollutant loads.

Standard 6- Critical Areas This standard requires that the design provide additional protection to sensitive areas such as public water supplies. The proposed stormwater management design meets the requirements of Standard 6.

None of the Project’s outfalls discharge to a Zone II, Interim Wellhead Protection Area, Outstanding Resource Water, shellfish growing area, bathing beach, or cold-water fishery.

Standard 7- Redevelopment This standard is included by MA DEP to allow projects within already developed areas more flexibility to improve upon existing conditions and meet some standards only to the maximum extent practicable (MEP).

Because this Project corrects substandard intersections, it qualifies as a redevelopment project and meets Standards 2, 3, and 4 to the maximum extent practicable.

Standard 8- Construction Period Pollution Prevention and Erosion Control Plan This standard requires that the design control the movement of sediment during construction. The proposed stormwater management design meets the requirements of Standard 8.

The implementation of erosion and sediment controls during construction is considered a standard practice for MassDOT roadway projects. Prior to land disturbance, the contractor will prepare and submit a complete Stormwater Pollution Prevention Plan (SWPPP) for meeting the standards and requirements of the NPDES Construction General Permit.

Standard 9- Operation and Maintenance Plan This standard requires that the design encourage proper long-term operation and maintenance of the proposed drainage system. The proposed stormwater management design meets the requirements of Standard 9.

An Operation and Maintenance Plan is included as Attachment I.

11 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

Standard 10- Illicit Discharge Prevention This standard requires that the design prevent illegal connections of non-stormwater pollutant sources to the drainage system. The proposed stormwater management design meets the requirements of Standard 10.

No illicit connections are known at the project site. If any such connections are discovered during construction, the contractor will notify the applicant, who will implement appropriate enforcement actions. An Illicit Discharge Compliance Statement will be submitted prior to the discharge of any stormwater to post-construction BMPs.

12 Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

ATTACHMENT A- MassDEP Checklist for Stormwater Report

Pages A-1 - A-8

Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program

Checklist for Stormwater Report

A. Introduction Important: When A Stormwater Report must be submitted with the Notice of Intent permit application to document filling out forms compliance with the Stormwater Management Standards. The following checklist is NOT a substitute for on the computer, use only the tab the Stormwater Report (which should provide more substantive and detailed information) but is offered key to move your here as a tool to help the applicant organize their Stormwater Management documentation for their cursor - do not Report and for the reviewer to assess this information in a consistent format. As noted in the Checklist, use the return the Stormwater Report must contain the engineering computations and supporting information set forth in key. Volume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared and certified by a Registered Professional Engineer (RPE) licensed in the Commonwealth.

The Stormwater Report must include:  The Stormwater Checklist completed and stamped by a Registered Professional Engineer (see page 2) that certifies that the Stormwater Report contains all required submittals.1 This Checklist is to be used as the cover for the completed Stormwater Report.  Applicant/Project Name  Project Address  Name of Firm and Registered Professional Engineer that prepared the Report  Long-Term Pollution Prevention Plan required by Standards 4-6  Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan required 2 by Standard 8  Operation and Maintenance Plan required by Standard 9

In addition to all plans and supporting information, the Stormwater Report must include a brief narrative describing stormwater management practices, including environmentally sensitive site design and LID

techniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans are required to show existing and proposed conditions, identify all wetland resource areas, NRCS soil types,

critical areas, Land Uses with Higher Potential Pollutant Loads (LUHPPL), and any areas on the site where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for both existing and proposed conditions at a scale that enables verification of supporting calculations.

As noted in the Checklist, the Stormwater Management Report shall document compliance with each of the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the Massachusetts Stormwater Handbook.

To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report Checklist by checking the box to indicate that the specified information has been included in the Stormwater Report. If any of the information specified in the checklist has not been submitted, the applicant must provide an explanation. The completed Stormwater Report Checklist and Certification must be submitted with the Stormwater Report.

1 The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included in the Stormwater Report, the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to

the post-construction best management practices.

2 For some complex projects, it may not be possible to include the Construction Period Erosion and Sedimentation Control Plan in the Stormwater Report. In that event, the issuing authority has the discretion to issue an Order of Conditions that approves the project and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan before commencing any land disturbance activity on the site.

604597 Northamption sw checklist • 04/01/08 Stormwater Report Checklist • Page 1 of 8

A - 1

A - 2

Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program

Checklist for Stormwater Report

Checklist (continued) LID Measures: Stormwater Standards require LID measures to be considered. Document what environmentally sensitive design and LID Techniques were considered during the planning and design of the project:

No disturbance to any Wetland Resource Areas

Site Design Practices (e.g. clustered development, reduced frontage setbacks)

Reduced Impervious Area (Redevelopment Only)

Minimizing disturbance to existing trees and shrubs

LID Site Design Credit Requested:

Credit 1

Credit 2

Credit 3

Use of “country drainage” versus curb and gutter conveyance and pipe

Bioretention Cells (includes Rain Gardens)

Constructed Stormwater Wetlands (includes Gravel Wetlands designs)

Treebox Filter

Water Quality Swale

Grass Channel

Green Roof Two (2) Sediment Forebays with two (2) Infiltration Basins Other (describe):

Standard 1: No New Untreated Discharges

No new untreated discharges Outlets have been designed so there is no erosion or scour to wetlands and waters of the Commonwealth

Supporting calculations specified in Volume 3 of the Massachusetts Stormwater Handbook included.

604597 Northamption sw checklist • 04/01/08 Stormwater Report Checklist • Page 3 of 8

A - 3

Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program

Checklist for Stormwater Report

Checklist (continued)

Standard 2: Peak Rate Attenuation Standard 2 waiver requested because the project is located in land subject to coastal storm flowage and stormwater discharge is to a wetland subject to coastal flooding. Evaluation provided to determine whether off-site flooding increases during the 100-year 24-hour storm.

Calculations provided to show that post-development peak discharge rates do not exceed pre- development rates for the 2-year and 10-year 24-hour storms. If evaluation shows that off-site flooding increases during the 100-year 24-hour storm, calculations are also provided to show that post-development peak discharge rates do not exceed pre-development rates for the 100-year 24- hour storm.

Standard 3: Recharge

Soil Analysis provided.

Required Recharge Volume calculation provided.

Required Recharge volume reduced through use of the LID site Design Credits.

Sizing the infiltration, BMPs is based on the following method: Check the method used.

Static Simple Dynamic Dynamic Field1

Runoff from all impervious areas at the site discharging to the infiltration BMP.

Runoff from all impervious areas at the site is not discharging to the infiltration BMP and calculations are provided showing that the drainage area contributing runoff to the infiltration BMPs is sufficient to generate the required recharge volume.

Recharge BMPs have been sized to infiltrate the Required Recharge Volume. Recharge BMPs have been sized to infiltrate the Required Recharge Volume only to the maximum extent practicable for the following reason:

Site is comprised solely of C and D soils and/or bedrock at the land surface

M.G.L. c. 21E sites pursuant to 310 CMR 40.0000

Solid Waste Landfill pursuant to 310 CMR 19.000 Project is otherwise subject to Stormwater Management Standards only to the maximum extent practicable.

Calculations showing that the infiltration BMPs will drain in 72 hours are provided.

Property includes a M.G.L. c. 21E site or a solid waste landfill and a mounding analysis is included.

1 80% TSS removal is required prior to discharge to infiltration BMP if Dynamic Field method is used.

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Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program

Checklist for Stormwater Report

Checklist (continued)

Standard 3: Recharge (continued)

The infiltration BMP is used to attenuate peak flows during storms greater than or equal to the 10- year 24-hour storm and separation to seasonal high groundwater is less than 4 feet and a mounding analysis is provided. Documentation is provided showing that infiltration BMPs do not adversely impact nearby wetland resource areas.

Standard 4: Water Quality

The Long-Term Pollution Prevention Plan typically includes the following:  Good housekeeping practices;

 Provisions for storing materials and waste products inside or under cover; Vehicle washing controls;   Requirements for routine inspections and maintenance of stormwater BMPs;  Spill prevention and response plans;  Provisions for maintenance of lawns, gardens, and other landscaped areas;  Requirements for storage and use of fertilizers, herbicides, and pesticides;  Pet waste management provisions;  Provisions for operation and management of septic systems;  Provisions for solid waste management;  Snow disposal and plowing plans relative to Wetland Resource Areas;  Winter Road Salt and/or Sand Use and Storage restrictions;  Street sweeping schedules;  Provisions for prevention of illicit discharges to the stormwater management system;  Documentation that Stormwater BMPs are designed to provide for shutdown and containment in the event of a spill or discharges to or near critical areas or from LUHPPL;  Training for staff or personnel involved with implementing Long-Term Pollution Prevention Plan;  List of Emergency contacts for implementing Long-Term Pollution Prevention Plan. A Long-Term Pollution Prevention Plan is attached to Stormwater Report and is included as an attachment to the Wetlands Notice of Intent. Treatment BMPs subject to the 44% TSS removal pretreatment requirement and the one inch rule for calculating the water quality volume are included, and discharge:

is within the Zone II or Interim Wellhead Protection Area

is near or to other critical areas

is within soils with a rapid infiltration rate (greater than 2.4 inches per hour)

involves runoff from land uses with higher potential pollutant loads.

The Required Water Quality Volume is reduced through use of the LID site Design Credits. Calculations documenting that the treatment train meets the 80% TSS removal requirement and, if applicable, the 44% TSS removal pretreatment requirement, are provided.

604597 Northamption sw checklist • 04/01/08 Stormwater Report Checklist • Page 5 of 8

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Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program

Checklist for Stormwater Report

Checklist (continued)

Standard 4: Water Quality (continued)

The BMP is sized (and calculations provided) based on:

The ½” or 1” Water Quality Volume or The equivalent flow rate associated with the Water Quality Volume and documentation is provided showing that the BMP treats the required water quality volume.

The applicant proposes to use proprietary BMPs, and documentation supporting use of proprietary BMP and proposed TSS removal rate is provided. This documentation may be in the form of the propriety BMP checklist found in Volume 2, Chapter 4 of the Massachusetts Stormwater Handbook and submitting copies of the TARP Report, STEP Report, and/or other third party studies verifying performance of the proprietary BMPs. A TMDL exists that indicates a need to reduce pollutants other than TSS and documentation showing

that the BMPs selected are consistent with the TMDL is provided.

Standard 5: Land Uses With Higher Potential Pollutant Loads (LUHPPLs) The NPDES Multi-Sector General Permit covers the land use and the Stormwater Pollution

Prevention Plan (SWPPP) has been included with the Stormwater Report. The NPDES Multi-Sector General Permit covers the land use and the SWPPP will be submitted prior

to the discharge of stormwater to the post-construction stormwater BMPs. The NPDES Multi-Sector General Permit does not cover the land use.

LUHPPLs are located at the site and industry specific source control and pollution prevention measures have been proposed to reduce or eliminate the exposure of LUHPPLs to rain, snow, snow melt and runoff, and been included in the long term Pollution Prevention Plan.

All exposure has been eliminated.

All exposure has not been eliminated and all BMPs selected are on MassDEP LUHPPL list.

The LUHPPL has the potential to generate runoff with moderate to higher concentrations of oil and grease (e.g. all parking lots with >1000 vehicle trips per day) and the treatment train includes an oil grit separator, a filtering bioretention area, a sand filter or equivalent.

Standard 6: Critical Areas The discharge is near or to a critical area and the treatment train includes only BMPs that MassDEP

has approved for stormwater discharges to or near that particular class of critical area. Critical areas and BMPs are identified in the Stormwater Report.

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Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program

Checklist for Stormwater Report

Checklist (continued) Standard 7: Redevelopments and Other Projects Subject to the Standards only to the maximum

extent practicable The project is subject to the Stormwater Management Standards only to the maximum Extent

Practicable as a: Limited Project Small Residential Projects: 5-9 single family houses or 5-9 units in a multi-family development

provided there is no discharge that may potentially affect a critical area. Small Residential Projects: 2-4 single family houses or 2-4 units in a multi-family development

with a discharge to a critical area Marina and/or boatyard provided the hull painting, service and maintenance areas are protected

from exposure to rain, snow, snow melt and runoff Bike Path and/or Foot Path

Redevelopment Project

Redevelopment portion of mix of new and redevelopment. Certain standards are not fully met (Standard No. 1, 8, 9, and 10 must always be fully met) and an

explanation of why these standards are not met is contained in the Stormwater Report.

The project involves redevelopment and a description of all measures that have been taken to improve existing conditions is provided in the Stormwater Report. The redevelopment checklist found in Volume 2 Chapter 3 of the Massachusetts Stormwater Handbook may be used to document that

the proposed stormwater management system (a) complies with Standards 2, 3 and the pretreatment and structural BMP requirements of Standards 4-6 to the maximum extent practicable and (b)

improves existing conditions.

Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control

A Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan must include the following information:

 Narrative;  Construction Period Operation and Maintenance Plan;  Names of Persons or Entity Responsible for Plan Compliance;  Construction Period Pollution Prevention Measures;  Erosion and Sedimentation Control Plan Drawings;  Detail drawings and specifications for erosion control BMPs, including sizing calculations;  Vegetation Planning;  Site Development Plan;  Construction Sequencing Plan;  Sequencing of Erosion and Sedimentation Controls;  Operation and Maintenance of Erosion and Sedimentation Controls;  Inspection Schedule;  Maintenance Schedule;  Inspection and Maintenance Log Form. A Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan containing

the information set forth above has been included in the Stormwater Report.

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Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program

Checklist for Stormwater Report

Checklist (continued) Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control

(continued) The project is highly complex and information is included in the Stormwater Report that explains why it is not possible to submit the Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan with the application. A Construction Period Pollution Prevention and Erosion and Sedimentation Control has not been included in the Stormwater Report but will be submitted before land disturbance begins.

The project is not covered by a NPDES Construction General Permit. The project is covered by a NPDES Construction General Permit and a copy of the SWPPP is in the

Stormwater Report. The project is covered by a NPDES Construction General Permit but no SWPPP been submitted.

The SWPPP will be submitted BEFORE land disturbance begins.

Standard 9: Operation and Maintenance Plan The Post Construction Operation and Maintenance Plan is included in the Stormwater Report and

includes the following information: Name of the stormwater management system owners;

Party responsible for operation and maintenance;

Schedule for implementation of routine and non-routine maintenance tasks;

Plan showing the location of all stormwater BMPs maintenance access areas;

Description and delineation of public safety features;

Estimated operation and maintenance budget; and

Operation and Maintenance Log Form. The responsible party is not the owner of the parcel where the BMP is located and the Stormwater

Report includes the following submissions: A copy of the legal instrument (deed, homeowner’s association, utility trust or other legal entity) that establishes the terms of and legal responsibility for the operation and maintenance of the project site stormwater BMPs; A plan and easement deed that allows site access for the legal entity to operate and maintain

BMP functions.

Standard 10: Prohibition of Illicit Discharges

The Long-Term Pollution Prevention Plan includes measures to prevent illicit discharges;

An Illicit Discharge Compliance Statement is attached; NO Illicit Discharge Compliance Statement is attached but will be submitted prior to the discharge of

any stormwater to post-construction BMPs.

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ATTACHMENT B- NRCS Soil Survey

Pages B-1 - B-4

Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

42° 19' 43'' N 42° 20' 13'' N

4689300 4689200 4689100 4689900 4689800 4689700 4689600 4689500 4689400

72° 36' 43'' W 43'' 36' 72° 72° 36' 43'' W 43'' 36' 72° 696700 4/27/2015 Page 1 of 4 696700 696600 696600 696500 696500 696400 696400 696300 696300 696200 696200 696100 696100 696000 696000 Feet Web Soil Survey 695900 National Cooperative Soil Survey 695900 (I-91 Northampton Hydrologic Soil Group) Hydrologic (I-91 Northampton 695800 695800 Hydrologic Soil Group—Hampshire County, Massachusetts, Central Part Massachusetts, County, Soil Group—Hampshire Hydrologic Meters 695700 695700 695600 695600 695500 695500 Map Scale: 1:6,480 if printed on A landscape (11" x 8.5") sheet.Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS84 0 0 201800 1200 600 300 0 01020300 200 100 50 0 695400 695400

N

Natural Resources Conservation Service

72° 37' 45'' W 45'' 37' 72° 72° 37' 45'' W 45'' 37' 72°

4689100 4689000 4689300 4689200 4689400 4689600 4689500 4689800 4689700 4689900 695300 42° 19' 43'' N 42° 20' 13'' N B - 1 4/27/2015 Page 2 of 4 MAP INFORMATION The soil surveys that comprise your AOI were mapped at 1:15,800. not be valid at this scale. Warning: Soil Map may beyond the scale of mapping can cause Enlargement of maps misunderstanding of the detail of mapping and accuracy of soil line do not show the small areas of contrasting placement. The maps shown at a more detailed scale. soils that could have been scale on each map sheet for map Please rely on the bar measurements. Resources Conservation Service Natural Source of Map: http://websoilsurvey.nrcs.usda.gov Web Soil Survey URL: Mercator (EPSG:3857) Web Coordinate System: the Web Mercator Maps from the Web Soil Survey are based on but distorts projection, which preserves direction and shape area, such as the distance and area. A projection that preserves 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. Central Hampshire County, Massachusetts, Soil Survey Area: Part Version 9, Sep 19, 2014 Survey Area Data: Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Mar 28, 2011—Apr 18, Date(s) aerial images were photographed: 2011 the soil lines were The orthophoto or other base map on which the background compiled and digitized probably differs from some minor shifting imagery displayed on these maps. As a result, of map unit boundaries may be evident. Web Soil Survey National Cooperative Soil Survey (I-91 Northampton Hydrologic Soil Group) Hydrologic (I-91 Northampton Local Roads Aerial Photography C C/D D Not rated or not available Streams and Canals Rails Interstate Highways US Routes Major Roads Background Water Features Transportation Hydrologic Soil Group—Hampshire County, Massachusetts, Central Part Massachusetts, County, Soil Group—Hampshire Hydrologic MAP LEGEND Area of Interest (AOI) A A/D B B/D C C/D D Not rated or not available A A/D B B/D C C/D D Not rated or not available A A/D B B/D Soil Rating Polygons Soil Rating Lines Soil Rating Points Area of Interest (AOI) Area of Interest Soils Natural Resources Conservation Service

B - 2 Hydrologic Soil Group—Hampshire County, Massachusetts, Central Part I-91 Northampton Hydrologic Soil Group

Hydrologic Soil Group

Hydrologic Soil Group— Summary by Map Unit — Hampshire County, Massachusetts, Central Part (MA609)

Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 1 Water 34.6 16.2% 8A Limerick silt loam, 0 to 3 B/D 1.8 0.8% percent slopes 30A Raynham silt loam, 0 to 3 C/D 0.0 0.0% percent slopes 96A Hadley silt loam, 0 to 3 B 44.2 20.7% percent slopes 98A Winooski silt loam, 0 to 3 B 43.7 20.4% percent slopes 225A Belgrade silt loam, 0 to 3 C 29.1 13.6% percent slopes 741A Amostown-Windsor silty 50.2 23.5% substratum-Urban land complex, 0 to 3 percent slopes 744A Hadley-Winooski-Urban B 10.0 4.7% land complex, 0 to 3 percent slopes Totals for Area of Interest 213.5 100.0%

Natural Resources Web Soil Survey 4/27/2015 Conservation Service National Cooperative Soil Survey Page 3 of 4

B - 3 Hydrologic Soil Group—Hampshire County, Massachusetts, Central Part I-91 Northampton Hydrologic Soil Group

Description

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 soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows:

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. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options

Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher

Natural Resources Web Soil Survey 4/27/2015 Conservation Service National Cooperative Soil Survey Page 4 of 4

B - 4

ATTACHMENT C- Existing and Proposed Catchment Maps

Pages C-1 - C-2

Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

NORTHAMPTON LEGEND I-91 INTERCHANGE 19

N 24" OUTFALL 9:10 AM

SHEET TOTAL STATE FED. AID PROJ. NO. 30" OUTFALL EX-A EX-B NO. SHEETS MA - 1 1972 DP-RIVER EX-C EX-D

PROJECT FILE NO. 604597 27-Oct-2017 EX-E EX-F EXISTING CATCHMENT MAP

EX-G EX-H Plotted on DP-A CONNECTICUT RIVER EX-K WOODS GRASS

18" OUTFALL DP-A DISCHARGE POINT FOR EX-A

EXISTING DRAINAGE DP-H

EXISTING CATCHMENTS 604597_HD(EXISTING CATCHMENTS).DWG AREA (SF) NAME DP CURVE Tc (MIN) IMPERVIOUS GRASS WOODS TOTAL NUMBER DP-E EX-A A 113,768 33,902 13,512 161,182 87 5.0 EX-B 3,940 48,910 9,354 DP-D B 62,204 62 5.0 EX-C C 63,951 37,201 0 101,152 84 5.0 EX-D D 7,609 0 0 7,609 98 5.0 DAMON RD NB OFF RAMP EX-E E 30,813 910 0 31,723 97 5.0 EX-F F 14,448 34,483 109,887 158,818 60 5.0 EX-G G 133,678 87,395 0 221,073 83 5.0 DP-B EX-H H 30,976 3,398 0 34,374 94 5.0 DP-K 6,365 DP-C EX-K K 0 108,236 114,601 55 5.0

NORWOTTUCK RAIL TRAIL

CROSS PATH RD DP-G

I-91 SB ON RAMP

DP-F 18" CMP CULVERT

OLD FERRY RD ROUTE 9 ROUTE

0 100 200 300 400

SCALE: 1" = 100'

C - 1 NORTHAMPTON LEGEND I-91 INTERCHANGE 19 N CONNECTICUT RIVER 9:06 AM

SHEET TOTAL 24" OUTFALL STATE FED. AID PROJ. NO. NO. SHEETS 30" OUTFALL PR-A PR-B MA - 2 1972 DP-RIVER PR-C PR-D PROJECT FILE NO. 604597 27-Oct-2017 PROPOSED CATCHMENT MAP PR-F PR-G Plotted on DP-A PR-H PR-J

PR-K BRUSH

GRASS WOODS XC11 RET DMH GRASS - WOODS DP-A DISCHARGE POINT FOR PR-A DP-H PROPOSED DRAINAGE

18" OUTFALL EXISTING DRAINAGE 604597_HD(PROPOSED CATCHMENTS).DWG D PROPOSED CATCHMENTS C01 RET DMH AREA (SF) NAME DP CURVE Tc (MIN)

IMPERVIOUS GRASS WOODS GRASS-WOODSBRUSH TOTAL NUMBER

D D D PR-A A 84,893 38,361 2,908 0 0 126,162 86 5.0 DP-D 73,887 32,888 106,775

D Pond B 0 0 0 87 5.0 D PR-B

D D

D C02 RET DMH Pond B B 0 35,471 0 0 0 35,471 61 5.0 DAMON RD D PR-C C 62,438 49,310 0 0 0 111,748 82 5.0

D PR-D D 5,956 0 0 0 0 5,956 98 5.0

D C03 DMH

D PR-F F 13,969 27,100 0 31,205 24,916 97,190 62 5.0

D D D DP-B NB OFF RAMP D PR-G G 154,965 93,199 0 0 0 248,164 84 5.0 DP-K REPLACE EXIST 24" RCP WITH 30" RCP PR-H H 25,013 4,685 0 0 0 29,698 92 5.0 POND-B DP-C 16,720 4,224 20,944 D PR-J Pond J 0 0 0 91 5.0

D Pond J F 0 21,547 0 0 0 21,547 61 5.0 G01 REMODEL DMH 2,974 54,713 28,655 86,342 56 5.0 D PR-K K 0 0

CROSS PATH RD

D NORWOTTUCK RAIL TRAIL DP-G D

D

D

D POND-J

SB ON RAMP

D

D

D D DP-F D

D 18" CMP CULVERT D

OLD FERRY RD ROUTE 9 ROUTE

0 100 200 300 400

SCALE: 1" = 100'

C - 2

ATTACHMENT D- Splash Pad Sizing Calculations

Page D1

Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

604597 - Improvements on I-91 Interchange 19 at Route 9 and Damon Road Splash Pad Sizing Calculations 2/27/2018 Northampton, MA By: MJR NOI Submittal Checked by: RWH

Splash Pad Sizing:

Objective: To determine the size of the rip rap apron at then end of a flared end section to prevent scour or erosion. Riprap Size: D50 (in.) Apron Length: L (ft.) Apron Depth: H (ft.) Arpon Width: W (ft.)

Known Information: Pipe Diameter: D (ft.) Design Discharge: Q (cfs) 2.65 Specific Weight of Rock Actual Tailwater Depth: TWa (ft.) 62.43 lb/ft^3 Unit Weight of Water Acceleration due to gravity, 32.2: g (ft/s^2)

Table 10.1. Example Riprap Classes and Apron Dimensions Class D50 Apron Length (ft.) Apron Weight (lb) (in.) Depth (in.) 1 5 4D 3.5D50 12 2 6 4D 3.3D50 21 3 10 5D 2.4D50 96 M2.02.3 Stone fo Pipe Ends 4 14 6D 2.2D50 263 5 20 7D 2.0D50 766 6 22 8D 2.0D50 1019 D - 1 Methodology: U.S. Federal Highway Administration, 2006, Hydraulic Design of Energy Dissipators for Culverts and Channels, Hydraulic Engineering Center Circular No. 14 Tailwater Check: Tailwater Depth should be limited to between 0.4D and 1.0D. If Tailwater is unknown, use 0.4D. Therefore, if TWa < 0.4D; use TWu = 0.4D if TWa > D; TWu = D

*Tailwater Depth to be used for Equation purposes, TWu Calculations: Use Equation (10.4) to determine rip rap size from Chapter 10 in HEC 14.

Design Criteria Apron Dimensions LOCATION OUTFALL Pipe Dia. Design Discharge Tailwater Invert Actual TW Depth TW Depth Riprap Size Riprap Size Rip Rap Length Depth Width D Q Elev. Elev. TWa TWu D50 D50 Table Class L D W (ft.) (cfs) (ft) (ft) (ft) (ft) (in.) (in.) (ft.) (in.) (ft.)

Example: HEC 14 5.00 85.00 943.23 941.23 0.00 2.0 5.2 6.0 2 20 20 28

Northampton F05 12 FES 1.00 1.17 122.40 122.00 0.00 0.4 0.7 5.0 1 4 18 6 Northampton J51 12 FES 1.00 2.49 129.40 129.00 0.00 0.4 2.0 5.0 1 4 18 6

Note: Apron will consist of M2. 02.4 Modified Rockfill

ATTACHMENT E- BMP Calculations

Volume Input Criteria - Infiltration Basin J ...... E-1 Volume Input Criteria - Infiltration Basin B ...... E-2 Water Quality and Recharge Summary ...... E-3

Pages E-1 - E-3

Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

604597: I-91 Interchange 19 BMP Calculations 2/27/2018 Northampton, MA Volume Input Criteria By: MJR NOI Submission Infiltration Basin J Checked by: DPL Infiltration Basin J

Forebay: Water Delta Volume Elevation Area Volume Void Cumulative Quality Elev. w/Ratio (FT) (SF) (CF) Ratio Volume (CF) Volume (FT) (CF) (CF) 128.00 183 0 100% 0 0 1.00 270 129.00 356 270 100% 270 270 270 1.00 471 130.00 586 471 100% 471 740.5

Infiltration Basin J: High Water Delta Net Volume Cumulative Elevation Area Marsh Volume Quality Elev. Area Void Ratio w/Ratio Volume (FT) (SF) Area (CF) Volume (FT) (SF) (CF) (CF) (SF) (CF) 123.00 1035 0 1035 0 100% 0 0 1.00 1254 124.00 1472 0 1472 1254 100% 1254 1254 1.00 1721 125.00 1970 0 1970 1721 100% 1721 2975 0.75 2177 125.75 2383 0 2383 1632 100% 1632 4607 4607 0.25 2453 126.00 2522 0 2522 613 100% 613 5220 1.00 2643 127.00 3130 0 2763 2643 100% 2643 7863

E - 1 604597: I-91 Interchange 19 BMP Calculations 2/27/2018 Northampton, MA Volume Input Criteria By: MJR NOI Submittal Infiltration Basin B Checked by: DPL Infiltration Basin B

Forebay: Water Delta Volume Elevation Area Volume Void Cumulative Quality Elev. w/Ratio (FT) (SF) (CF) Ratio Volume (CF) Volume (FT) (CF) (CF) 130.00 196 0 100% 0 0 1.00 307 131.00 418 307 100% 307 307 1.00 568 132.00 717 568 100% 568 875 875 1.00 885 133.00 1053 885 100% 885 1760 1.00 1221 134.00 1388 1221 100% 1221 2980 1.00 1576 135.00 1764 1576 100% 1576 4556 1.00 1972 136.00 2180 1972 100% 1972 6528

Infiltration Basin: Water Delta Volume Elevation Area Volume Void Cumulative Quality Elev. w/Ratio (FT) (SF) (CF) Ratio Volume (CF) Volume (FT) (CF) (CF) 130.00 1495 0 100% 0 0 1.00 1894 131.00 2292 1894 100% 1894 1894 1.00 2729 132.00 3166 2729 100% 2729 4623 0.75 3498 132.75 3829 2623 100% 2623 7246 7246 0.25 3937 133.00 4045 984 100% 984 8230 1.00 4482 134.00 4918 4482 100% 4482 12711 1.00 5371 135.00 5823 5371 100% 5371 18082 1.00 6292 136.00 6761 6292 100% 6292 24374

E - 2 604597: I-91 Interchange 19 BMP Calculations 2/27/2018 Northampton, MA Water Quality and Recharge Summary By: MJR NOI Submittal Checked by: DPL Infiltration Basin J

Forebay Total Contributing Impervious Area: 16,720 SF Forebay Volume Required: (0.1 inch x Area) 140 CF Forebay Volume Provided: 270 CF

Infiltration Basin: Total Contributing Impervious Area: 16,720 SF Required Water Qualtiy Volume: (1 inch x Area) 1,394 CF Required Recharge Volume (0.35 inches x Impervious Area) 488 CF Provided Water Quality / Recharge Volume: 4,607 CF

Required 72 Hour Drawdown: Rv: 4,607 CF K (Saturated Hydraulic Conductivity, Rawls Table for Loamy Sand): 2.41 IN/HR Bottom Area of Basin (elevation 123): 1,035 SF Drawdown Time: 22 HR

Infiltration Basin B

Forebay Total Contributing Impervious Area: 73,887 SF Forebay Volume Required: (0.1 inch x Area) 616 CF Forebay Volume Provided: 875 CF

Infiltration Basin: Total Contributing Impervious Area: 73,887 SF Required Water Qualtiy Volume: (1/2 inch x Impervious Area) 3,079 CF Required Recharge Volume (0.35 inches x Impervious Area) 2,155 CF Provided Water Quality / Recharge Volume: 7,246 CF

Required 72 Hour Drawdown: Rv: 7,246 CF K (Saturated Hydraulic Conductivity, Rawls Table for Sandy Loam): 1.02 IN/HR Bottom Area of Basin (elevation 130): 1,495 SF Drawdown Time: 57 HR

Recharge Volume for Entire Site:

Total Existing Impervious Area: 399,183 SF Total Proposed Impervious Area: 440,815 SF Net Total Additional Impervious Area: 41,632 SF Required Recharge Volume (0.35 inches x Additional Impervious Area) 1,214 CF Provided Water Quality / Recharge Volume: 11,853 CF

E - 3

ATTACHMENT F- Peak Rate Attenuation Modeling Output

Existing Model Output ...... F-1 - F-45 Proposed Model Output ...... F-46 - F-99

(The model outputs included in this report are the summaries only. Hydrograph Tables and associated graphs for existing and proposed are 596 and 1,686 pages, respectively. These full outputs are available if requested.)

Pages F-1 - F-99

Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

604597 - Existing Drainage Model Project Summary 604597 Title Northampton Engineer Michael Rieger, PE Company TranSystems Date 10/25/2017

Notes F - 1

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E E X X - - P P IP I E P - 5 E D 2

- E F -2

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Type III 24-hr Northampton

Time-Depth Curve, 100 years 5

Time-Depth Curve, 10 years 8

Time-Depth Curve, 2 years 11

EX-A

Time of Concentration Calculations, 2 years 14

EX-B

Time of Concentration Calculations, 2 years 16

EX-C

Time of Concentration Calculations, 2 years 18 F - 3 EX-D

Time of Concentration Calculations, 2 years 20

EX-E

Time of Concentration Calculations, 2 years 22

EX-F

Time of Concentration Calculations, 2 years 24

EX-G

Time of Concentration Calculations, 2 years 26

EX-H

Time of Concentration Calculations, 2 years 28

EX-K

Time of Concentration Calculations, 2 years 30

EX-A

Runoff CN-Area, 2 years 32

EX-B

Runoff CN-Area, 2 years 33

EX-C

Runoff CN-Area, 2 years 34

EX-D

Runoff CN-Area, 2 years 35

EX-E

Runoff CN-Area, 2 years 36

EX-F

Runoff CN-Area, 2 years 37

EX-G

Runoff CN-Area, 2 years 38

EX-H

Runoff CN-Area, 2 years 39

EX-K Runoff CN-Area, 2 years 40 Master Network Summary 2

Type III 24-hr Northampton

Time-Depth Curve, 100 years 5

Time-Depth Curve, 10 years 8

Time-Depth Curve, 2 years 11

EX-A

Time of Concentration Calculations, 2 years 14

EX-B

Time of Concentration Calculations, 2 years 16

EX-C

Time of Concentration Calculations, 2 years 18

EX-D

Time of Concentration Calculations, 2 years 20

EX-E

Time of Concentration Calculations, 2 years 22

EX-F

Time of Concentration Calculations, 2 years 24

EX-G

Time of Concentration Calculations, 2 years 26

EX-H

Time of Concentration Calculations, 2 years 28

EX-K

Time of Concentration Calculations, 2 years 30 EX-A Table of Contents Runoff CN-Area, 2 years 32

EX-B

Runoff CN-Area, 2 years 33

EX-C

Runoff CN-Area, 2 years 34

EX-D

Runoff CN-Area, 2 years 35

EX-E

Runoff CN-Area, 2 years 36

EX-F

Runoff CN-Area, 2 years 37 F - 4 EX-G

Runoff CN-Area, 2 years 38

EX-H

Runoff CN-Area, 2 years 39

EX-K Runoff CN-Area, 2 years 40 604597 - Existing Drainage Model Subsection: Master Network Summary

Catchments Summary Label Scenario Return Hydrograph Volume Time to Peak Peak Flow Event (ft³) (min) (ft³/s) (years) EX-A 2-Year 2 23,339 726.50 6.66 EX-A 10-Year 10 41,592 726.00 11.59 EX-A 100-Year 100 65,781 726.00 17.85 EX-B 2-Year 2 2,061 727.50 0.43 EX-B 10-Year 10 5,902 727.00 1.61 EX-B 100-Year 100 12,264 726.50 3.51 EX-C 2-Year 2 12,770 726.50 3.68 EX-C 10-Year 10 23,723 726.00 6.71 EX-C 100-Year 100 38,511 726.00 10.65 EX-D 2-Year 2 1,754 726.00 0.44 EX-D 10-Year 10 2,702 726.00 0.66 F - 5 EX-D 100-Year 100 3,905 726.00 0.94 EX-F 2-Year 2 4,404 728.00 0.77 EX-F 10-Year 10 13,478 727.00 3.58 EX-F 100-Year 100 28,924 726.50 8.23 EX-E 2-Year 2 7,023 726.00 1.79 EX-E 10-Year 10 10,962 726.00 2.73 EX-E 100-Year 100 15,966 726.00 3.91 EX-H 2-Year 2 6,727 726.00 1.81 EX-H 10-Year 10 10,922 726.00 2.85 EX-H 100-Year 100 16,297 726.00 4.15 EX-G 2-Year 2 26,624 726.50 7.68 EX-G 10-Year 10 50,171 726.50 14.26 EX-G 100-Year 100 82,177 726.00 22.84 EX-K 2-Year 2 1,856 740.00 0.19 EX-K 10-Year 10 7,079 727.50 1.68 EX-K 100-Year 100 16,720 727.00 4.63

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Node Summary Label Scenario Return Hydrograph Volume Time to Peak Peak Flow Event (ft³) (min) (ft³/s) (years) DP-F 2-Year 2 4,404 728.00 0.77 DP-F 10-Year 10 13,478 727.00 3.58 DP-F 100-Year 100 28,924 726.50 8.23 DP-H 2-Year 2 6,727 726.00 1.81 DP-H 10-Year 10 10,922 726.00 2.85 DP-H 100-Year 100 16,297 726.00 4.15 DP-D 2-Year 2 1,754 726.00 0.44 DP-D 10-Year 10 2,702 726.00 0.66 DP-D 100-Year 100 3,905 726.00 0.94 DP-C 2-Year 2 12,770 726.50 3.68 DP-C 10-Year 10 23,723 726.00 6.71 F - 6 DP-C 100-Year 100 38,511 726.00 10.65 DP-CG1 2-Year 2 39,369 727.00 11.30 DP-CG1 10-Year 10 73,858 726.50 20.87 DP-CG1 100-Year 100 121,221 726.50 26.62 DP-G 2-Year 2 26,624 726.50 7.68 DP-G 10-Year 10 50,171 726.50 14.26 DP-G 100-Year 100 82,177 726.00 22.84 DP-CG2 2-Year 2 39,347 727.50 11.26 DP-CG2 10-Year 10 73,826 727.00 20.83 DP-CG2 100-Year 100 121,178 726.50 26.60 DP-B 2-Year 2 2,061 727.50 0.43 DP-B 10-Year 10 5,902 727.00 1.61 DP-B 100-Year 100 12,264 726.50 3.51 DP-E 2-Year 2 7,023 726.00 1.79 DP-E 10-Year 10 10,962 726.00 2.73 DP-E 100-Year 100 15,966 726.00 3.91 DP-BCDEG 2-Year 2 50,154 727.50 13.78

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Node Summary Label Scenario Return Hydrograph Volume Time to Peak Peak Flow Event (ft³) (min) (ft³/s) (years) DP-BCDEG 10-Year 10 93,347 727.50 25.66 DP-BCDEG 100-Year 100 154,049 726.50 34.54 12+85 MH 2-Year 2 50,118 728.00 13.71 12+85 MH 10-Year 10 93,296 728.00 25.57 12+85 MH 100-Year 100 154,971 721.50 31.33 DP-A 2-Year 2 23,339 726.50 6.66 DP-A 10-Year 10 41,592 726.00 11.59 DP-A 100-Year 100 65,781 726.00 17.85 30" Outfall 2-Year 2 50,087 728.50 13.67 30" Outfall 10-Year 10 93,251 728.00 25.51 30" Outfall 100-Year 100 154,911 738.00 31.33 F - 7 DP-River 2-Year 2 73,426 727.50 20.01 DP-River 10-Year 10 134,843 727.00 36.70 DP-River 100-Year 100 220,692 726.00 49.18 DP-K 2-Year 2 1,856 740.00 0.19 DP-K 10-Year 10 7,079 727.50 1.68 DP-K 100-Year 100 16,720 727.00 4.63

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 4 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time-Depth Curve Return Event: 100 years Label: Type III 24-hr Northampton Storm Event: 100-year, 24-hr rainfall

Time-Depth Curve: 100-year, 24-hr rainfall 100-year, 24-hr Label rainfall Start Time 0.00 min Increment 6.00 min End Time 1,440.00 min Return Event 100 years

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in)

F - 8 0.00 0.0 0.0 0.0 0.0 0.0 30.00 0.0 0.0 0.0 0.1 0.1 60.00 0.1 0.1 0.1 0.1 0.1 90.00 0.1 0.1 0.1 0.1 0.1 120.00 0.1 0.1 0.1 0.1 0.2 150.00 0.2 0.2 0.2 0.2 0.2 180.00 0.2 0.2 0.2 0.2 0.2 210.00 0.2 0.2 0.3 0.3 0.3 240.00 0.3 0.3 0.3 0.3 0.3 270.00 0.3 0.3 0.3 0.3 0.4 300.00 0.4 0.4 0.4 0.4 0.4 330.00 0.4 0.4 0.4 0.4 0.5 360.00 0.5 0.5 0.5 0.5 0.5 390.00 0.5 0.5 0.5 0.6 0.6 420.00 0.6 0.6 0.6 0.6 0.6 450.00 0.7 0.7 0.7 0.7 0.7 480.00 0.7 0.7 0.8 0.8 0.8 510.00 0.8 0.8 0.9 0.9 0.9 Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 5 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time-Depth Curve Return Event: 100 years Label: Type III 24-hr Northampton Storm Event: 100-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 540.00 0.9 1.0 1.0 1.0 1.0 570.00 1.1 1.1 1.1 1.1 1.2 600.00 1.2 1.2 1.3 1.3 1.3 630.00 1.4 1.4 1.5 1.5 1.6 660.00 1.6 1.6 1.7 1.8 1.8 690.00 1.9 2.0 2.2 2.4 2.7 720.00 3.2 3.7 4.0 4.2 4.4 750.00 4.5 4.6 4.6 4.7 4.8 780.00 4.8 4.8 4.9 4.9 5.0

F - 9 810.00 5.0 5.1 5.1 5.1 5.2 840.00 5.2 5.2 5.3 5.3 5.3 870.00 5.3 5.4 5.4 5.4 5.4 900.00 5.5 5.5 5.5 5.5 5.6 930.00 5.6 5.6 5.6 5.6 5.7 960.00 5.7 5.7 5.7 5.7 5.7 990.00 5.7 5.8 5.8 5.8 5.8 1,020.00 5.8 5.8 5.8 5.9 5.9 1,050.00 5.9 5.9 5.9 5.9 5.9 1,080.00 5.9 5.9 6.0 6.0 6.0 1,110.00 6.0 6.0 6.0 6.0 6.0 1,140.00 6.0 6.0 6.1 6.1 6.1 1,170.00 6.1 6.1 6.1 6.1 6.1 1,200.00 6.1 6.1 6.1 6.1 6.2 1,230.00 6.2 6.2 6.2 6.2 6.2 1,260.00 6.2 6.2 6.2 6.2 6.2 1,290.00 6.2 6.2 6.3 6.3 6.3

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 6 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time-Depth Curve Return Event: 100 years Label: Type III 24-hr Northampton Storm Event: 100-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 1,320.00 6.3 6.3 6.3 6.3 6.3 1,350.00 6.3 6.3 6.3 6.3 6.3 1,380.00 6.3 6.3 6.4 6.4 6.4 1,410.00 6.4 6.4 6.4 6.4 6.4 1,440.00 6.4 (N/A) (N/A) (N/A) (N/A) F - 10

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Time-Depth Curve: 10-year, 24-hr rainfall 10-year, 24-hr Label rainfall Start Time 0.00 min Increment 6.00 min End Time 1,440.00 min Return Event 10 years

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in)

F - 11 0.00 0.0 0.0 0.0 0.0 0.0 30.00 0.0 0.0 0.0 0.0 0.0 60.00 0.0 0.0 0.1 0.1 0.1 90.00 0.1 0.1 0.1 0.1 0.1 120.00 0.1 0.1 0.1 0.1 0.1 150.00 0.1 0.1 0.1 0.1 0.1 180.00 0.1 0.1 0.1 0.2 0.2 210.00 0.2 0.2 0.2 0.2 0.2 240.00 0.2 0.2 0.2 0.2 0.2 270.00 0.2 0.2 0.2 0.2 0.2 300.00 0.3 0.3 0.3 0.3 0.3 330.00 0.3 0.3 0.3 0.3 0.3 360.00 0.3 0.3 0.3 0.3 0.4 390.00 0.4 0.4 0.4 0.4 0.4 420.00 0.4 0.4 0.4 0.4 0.4 450.00 0.5 0.5 0.5 0.5 0.5 480.00 0.5 0.5 0.5 0.6 0.6 510.00 0.6 0.6 0.6 0.6 0.6 Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 8 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time-Depth Curve Return Event: 10 years Label: Type III 24-hr Northampton Storm Event: 10-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 540.00 0.7 0.7 0.7 0.7 0.7 570.00 0.7 0.8 0.8 0.8 0.8 600.00 0.9 0.9 0.9 0.9 0.9 630.00 1.0 1.0 1.0 1.1 1.1 660.00 1.1 1.2 1.2 1.2 1.3 690.00 1.3 1.4 1.5 1.7 1.9 720.00 2.2 2.6 2.8 3.0 3.1 750.00 3.2 3.2 3.3 3.3 3.3 780.00 3.4 3.4 3.4 3.5 3.5 F - 12 810.00 3.5 3.6 3.6 3.6 3.6 840.00 3.6 3.7 3.7 3.7 3.7 870.00 3.8 3.8 3.8 3.8 3.8 900.00 3.8 3.9 3.9 3.9 3.9 930.00 3.9 3.9 3.9 4.0 4.0 960.00 4.0 4.0 4.0 4.0 4.0 990.00 4.0 4.1 4.1 4.1 4.1 1,020.00 4.1 4.1 4.1 4.1 4.1 1,050.00 4.1 4.1 4.2 4.2 4.2 1,080.00 4.2 4.2 4.2 4.2 4.2 1,110.00 4.2 4.2 4.2 4.2 4.2 1,140.00 4.2 4.3 4.3 4.3 4.3 1,170.00 4.3 4.3 4.3 4.3 4.3 1,200.00 4.3 4.3 4.3 4.3 4.3 1,230.00 4.3 4.3 4.3 4.4 4.4 1,260.00 4.4 4.4 4.4 4.4 4.4 1,290.00 4.4 4.4 4.4 4.4 4.4

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CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 1,320.00 4.4 4.4 4.4 4.4 4.4 1,350.00 4.4 4.4 4.4 4.5 4.5 1,380.00 4.5 4.5 4.5 4.5 4.5 1,410.00 4.5 4.5 4.5 4.5 4.5 1,440.00 4.5 (N/A) (N/A) (N/A) (N/A) F - 13

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Time-Depth Curve: 2-year, 24-hr rainfall 2-year, 24-hr Label rainfall Start Time 0.00 min Increment 6.00 min End Time 1,440.00 min Return Event 2 years

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in)

F - 14 0.00 0.0 0.0 0.0 0.0 0.0 30.00 0.0 0.0 0.0 0.0 0.0 60.00 0.0 0.0 0.0 0.0 0.0 90.00 0.0 0.0 0.1 0.1 0.1 120.00 0.1 0.1 0.1 0.1 0.1 150.00 0.1 0.1 0.1 0.1 0.1 180.00 0.1 0.1 0.1 0.1 0.1 210.00 0.1 0.1 0.1 0.1 0.1 240.00 0.1 0.1 0.1 0.1 0.1 270.00 0.1 0.2 0.2 0.2 0.2 300.00 0.2 0.2 0.2 0.2 0.2 330.00 0.2 0.2 0.2 0.2 0.2 360.00 0.2 0.2 0.2 0.2 0.2 390.00 0.2 0.2 0.3 0.3 0.3 420.00 0.3 0.3 0.3 0.3 0.3 450.00 0.3 0.3 0.3 0.3 0.3 480.00 0.3 0.3 0.4 0.4 0.4 510.00 0.4 0.4 0.4 0.4 0.4 Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 11 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time-Depth Curve Return Event: 2 years Label: Type III 24-hr Northampton Storm Event: 2-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 540.00 0.4 0.4 0.5 0.5 0.5 570.00 0.5 0.5 0.5 0.5 0.6 600.00 0.6 0.6 0.6 0.6 0.6 630.00 0.6 0.7 0.7 0.7 0.7 660.00 0.7 0.8 0.8 0.8 0.9 690.00 0.9 0.9 1.0 1.1 1.2 720.00 1.5 1.8 1.9 2.0 2.1 750.00 2.1 2.1 2.2 2.2 2.2 780.00 2.2 2.3 2.3 2.3 2.3 F - 15 810.00 2.4 2.4 2.4 2.4 2.4 840.00 2.4 2.4 2.5 2.5 2.5 870.00 2.5 2.5 2.5 2.5 2.6 900.00 2.6 2.6 2.6 2.6 2.6 930.00 2.6 2.6 2.6 2.6 2.7 960.00 2.7 2.7 2.7 2.7 2.7 990.00 2.7 2.7 2.7 2.7 2.7 1,020.00 2.7 2.7 2.7 2.7 2.8 1,050.00 2.8 2.8 2.8 2.8 2.8 1,080.00 2.8 2.8 2.8 2.8 2.8 1,110.00 2.8 2.8 2.8 2.8 2.8 1,140.00 2.8 2.8 2.8 2.8 2.8 1,170.00 2.9 2.9 2.9 2.9 2.9 1,200.00 2.9 2.9 2.9 2.9 2.9 1,230.00 2.9 2.9 2.9 2.9 2.9 1,260.00 2.9 2.9 2.9 2.9 2.9 1,290.00 2.9 2.9 2.9 2.9 2.9

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 12 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time-Depth Curve Return Event: 2 years Label: Type III 24-hr Northampton Storm Event: 2-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 1,320.00 2.9 2.9 2.9 3.0 3.0 1,350.00 3.0 3.0 3.0 3.0 3.0 1,380.00 3.0 3.0 3.0 3.0 3.0 1,410.00 3.0 3.0 3.0 3.0 3.0 1,440.00 3.0 (N/A) (N/A) (N/A) (N/A) F - 16

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 13 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-A Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 17

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 14 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-A Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 18

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 15 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-B Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 19

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 16 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-B Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 20

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 17 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-C Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 21

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 18 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-C Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 22

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 19 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-D Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 23

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==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 24

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 21 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-E Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 25

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 22 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-E Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 26

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 23 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-F Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 27

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 24 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-F Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 28

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 25 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-G Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 29

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 26 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-G Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 30

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 27 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-H Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 31

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 28 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-H Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 32

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 29 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-K Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 33

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 30 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: EX-K Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 34

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 31 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: EX-A Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 113,768 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 33,902 0.0 0.0 61.000 cover > 75% - Soil B Woods - good - Soil B 55.000 13,512 0.0 0.0 55.000 COMPOSITE AREA & WEIGHTED CN ---> (N/A) 161,182 (N/A) (N/A) 86.613 F - 35

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 32 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: EX-B Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 3,940 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 48,910 0.0 0.0 61.000 cover > 75% - Soil B Woods - good - Soil B 55.000 9,354 0.0 0.0 55.000 COMPOSITE AREA & WEIGHTED CN ---> (N/A) 62,204 (N/A) (N/A) 62.441 F - 36

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 33 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: EX-C Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 63,951 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 37,201 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 101,152 (N/A) (N/A) 84.392 F - 37

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 34 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: EX-D Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 7,609 0.0 0.0 98.000 driveways, Streets and roads - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 7,609 (N/A) (N/A) 98.000 F - 38

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 35 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: EX-E Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 30,813 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 910 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 31,723 (N/A) (N/A) 96.939 F - 39

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 36 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: EX-F Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 14,448 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 34,483 0.0 0.0 61.000 cover > 75% - Soil B Woods - good - Soil B 55.000 109,887 0.0 0.0 55.000 COMPOSITE AREA & WEIGHTED CN ---> (N/A) 158,818 (N/A) (N/A) 60.215 F - 40

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 37 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: EX-G Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 133,678 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 87,395 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 221,073 (N/A) (N/A) 83.373 F - 41

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 38 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: EX-H Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 30,976 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 3,398 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 34,374 (N/A) (N/A) 94.342 F - 42

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 39 of 42 +1-203-755-1666 604597 - Existing Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: EX-K Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Open space (Lawns,parks etc.) - Good condition; grass 61.000 6,365 0.0 0.0 61.000 cover > 75% - Soil B Woods - good - Soil B 55.000 108,236 0.0 0.0 55.000 COMPOSITE AREA & WEIGHTED CN ---> (N/A) 114,601 (N/A) (N/A) 55.333 F - 43

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 40 of 42 +1-203-755-1666 604597 - Existing Drainage Model Index E

EX-A (Runoff CN-Area, 2 years)...32 EX-A (Time of Concentration Calculations, 2 years)...14, 15 EX-B (Runoff CN-Area, 2 years)...33 EX-B (Time of Concentration Calculations, 2 years)...16, 17 EX-C (Runoff CN-Area, 2 years)...34 EX-C (Time of Concentration Calculations, 2 years)...18, 19 EX-D (Runoff CN-Area, 2 years)...35 EX-D (Time of Concentration Calculations, 2 years)...20, 21 F - 44 EX-E (Runoff CN-Area, 2 years)...36 EX-E (Time of Concentration Calculations, 2 years)...22, 23 EX-F (Runoff CN-Area, 2 years)...37

EX-F (Time of Concentration Calculations, 2 years)...24, 25

EX-G (Runoff CN-Area, 2 years)...38 EX-G (Time of Concentration Calculations, 2 years)...26, 27 EX-H (Runoff CN-Area, 2 years)...39 EX-H (Time of Concentration Calculations, 2 years)...28, 29 EX-K (Runoff CN-Area, 2 years)...40 EX-K (Time of Concentration Calculations, 2 years)...30, 31 M Bentley PondPack V8i NorthamptonMaster NetworkExisting.ppc Summary...2, 3, 4 Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 41 of 42 +1-203-755-1666 T Type III 24-hr Northampton (Time-Depth Curve, 10 years)...8, 9, 10 Type III 24-hr Northampton (Time-Depth Curve, 100 years)...5, 6, 7 Type III 24-hr Northampton (Time-Depth Curve, 2 years)...11, 12, 13 E

EX-A (Runoff CN-Area, 2 years)...32 EX-A (Time of Concentration Calculations, 2 years)...14, 15 EX-B (Runoff CN-Area, 2 years)...33 EX-B (Time of Concentration Calculations, 2 years)...16, 17 EX-C (Runoff CN-Area, 2 years)...34 EX-C (Time of Concentration Calculations, 2 years)...18, 19 EX-D (Runoff CN-Area, 2 years)...35 EX-D (Time of Concentration Calculations, 2 years)...20, 21 EX-E (Runoff CN-Area, 2 years)...36 EX-E (Time of Concentration Calculations, 2 years)...22, 23 EX-F (Runoff CN-Area, 2 years)...37

EX-F (Time of Concentration Calculations, 2 years)...24, 25

EX-G (Runoff CN-Area, 2 years)...38 EX-G (Time of Concentration Calculations, 2 years)...26, 27 EX-H (Runoff CN-Area, 2 years)...39 EX-H (Time of Concentration Calculations, 2 years)...28, 29 EX-K (Runoff CN-Area, 2 years)...40 EX-K (Time of Concentration Calculations, 2 years)...30, 31 604597 - Existing Drainage Model M

Master Network Summary...2, 3, 4

T Type III 24-hr Northampton (Time-Depth Curve, 10 years)...8, 9, 10 Type III 24-hr Northampton (Time-Depth Curve, 100 years)...5, 6, 7 Type III 24-hr Northampton (Time-Depth Curve, 2 years)...11, 12, 13 F - 45

Bentley PondPack V8i Northampton Existing.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 42 of 42 +1-203-755-1666 604597 - Proposed Drainage Model Project Summary 604597 Title Northampton Engineer Michael Rieger, PE Company TranSystems Date 10/25/2017

Notes F - 46

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 1 of 50 +1-203-755-1666 Scenario: 2-Year

E X - P IP E -D 4 2

2 G -C E IP -P R P F -47

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 1 of 1 +1-203-755-1666 Table of Contents Master Network Summary 2

Type III 24-hr Northampton

Time-Depth Curve, 100 years 7

Time-Depth Curve, 10 years 10

Time-Depth Curve, 2 years 13

PR-A

Time of Concentration Calculations, 2 years 16

PR-B

Time of Concentration Calculations, 2 years 18

PR-C

Time of Concentration Calculations, 2 years 20 F - 48 PR-D

Time of Concentration Calculations, 2 years 22

PR-F

Time of Concentration Calculations, 2 years 24

PR-G

Time of Concentration Calculations, 2 years 26

PR-H

Time of Concentration Calculations, 2 years 28

PR-J

Time of Concentration Calculations, 2 years 30

PR-K

Time of Concentration Calculations, 2 years 32

PR-Pond B

Time of Concentration Calculations, 2 years 34

PR-Pond J

Time of Concentration Calculations, 2 years 36

PR-A

Runoff CN-Area, 2 years 38

PR-B

Runoff CN-Area, 2 years 39

PR-C

Runoff CN-Area, 2 years 40

PR-D

Runoff CN-Area, 2 years 41

PR-F

Runoff CN-Area, 2 years 42

PR-G

Runoff CN-Area, 2 years 43

PR-H

Runoff CN-Area, 2 years 44

PR-J

Runoff CN-Area, 2 years 45

PR-K

Runoff CN-Area, 2 years 46

PR-Pond B

Runoff CN-Area, 2 years 47

PR-Pond J Runoff CN-Area, 2 years 48 Master Network Summary 2

Type III 24-hr Northampton

Time-Depth Curve, 100 years 7

Time-Depth Curve, 10 years 10

Time-Depth Curve, 2 years 13

PR-A

Time of Concentration Calculations, 2 years 16

PR-B

Time of Concentration Calculations, 2 years 18

PR-C

Time of Concentration Calculations, 2 years 20

PR-D

Time of Concentration Calculations, 2 years 22

PR-F

Time of Concentration Calculations, 2 years 24

PR-G

Time of Concentration Calculations, 2 years 26

PR-H

Time of Concentration Calculations, 2 years 28

PR-J

Time of Concentration Calculations, 2 years 30

PR-K

Time of Concentration Calculations, 2 years 32 PR-Pond B Table of Contents Time of Concentration Calculations, 2 years 34

PR-Pond J

Time of Concentration Calculations, 2 years 36

PR-A

Runoff CN-Area, 2 years 38

PR-B

Runoff CN-Area, 2 years 39

PR-C

Runoff CN-Area, 2 years 40

PR-D

Runoff CN-Area, 2 years 41 F - 49 PR-F

Runoff CN-Area, 2 years 42

PR-G

Runoff CN-Area, 2 years 43

PR-H

Runoff CN-Area, 2 years 44

PR-J

Runoff CN-Area, 2 years 45

PR-K

Runoff CN-Area, 2 years 46

PR-Pond B

Runoff CN-Area, 2 years 47

PR-Pond J Runoff CN-Area, 2 years 48 Master Network Summary 2

Type III 24-hr Northampton

Time-Depth Curve, 100 years 7

Time-Depth Curve, 10 years 10

Time-Depth Curve, 2 years 13

PR-A

Time of Concentration Calculations, 2 years 16

PR-B

Time of Concentration Calculations, 2 years 18

PR-C

Time of Concentration Calculations, 2 years 20

PR-D

Time of Concentration Calculations, 2 years 22

PR-F

Time of Concentration Calculations, 2 years 24

PR-G

Time of Concentration Calculations, 2 years 26

PR-H

Time of Concentration Calculations, 2 years 28

PR-J

Time of Concentration Calculations, 2 years 30

PR-K

Time of Concentration Calculations, 2 years 32

PR-Pond B

Time of Concentration Calculations, 2 years 34

PR-Pond J

Time of Concentration Calculations, 2 years 36

PR-A

Runoff CN-Area, 2 years 38

PR-B

Runoff CN-Area, 2 years 39

PR-C

Runoff CN-Area, 2 years 40

PR-D

Runoff CN-Area, 2 years 41

PR-F

Runoff CN-Area, 2 years 42

PR-G

Runoff CN-Area, 2 years 43

PR-H

Runoff CN-Area, 2 years 44

PR-J

Runoff CN-Area, 2 years 45

PR-K

Runoff CN-Area, 2 years 46

PR-Pond B

Runoff CN-Area, 2 years 47 PR-Pond J Table of Contents Runoff CN-Area, 2 years 48 F - 50 604597 - Proposed Drainage Model Subsection: Master Network Summary

Catchments Summary Label Scenario Return Hydrograph Volume Time to Peak Peak Flow Event (ft³) (min) (ft³/s) (years) PR-A 2-Year 2 17,463 726.50 5.01 PR-A 10-Year 10 31,550 726.00 8.84 PR-A 100-Year 100 50,329 726.00 13.75 PR-B 2-Year 2 15,461 726.50 4.42 PR-B 10-Year 10 27,553 726.00 7.68 PR-B 100-Year 100 43,576 726.00 11.83 PR-C 2-Year 2 12,829 726.50 3.70 PR-C 10-Year 10 24,527 726.50 7.00 PR-C 100-Year 100 40,539 726.00 11.32 PR-D 2-Year 2 1,373 726.00 0.34

F - 51 PR-D 10-Year 10 2,115 726.00 0.52 PR-D 100-Year 100 3,056 726.00 0.74 PR-F 2-Year 2 3,220 727.50 0.67 PR-F 10-Year 10 9,222 727.00 2.52 PR-F 100-Year 100 19,163 726.50 5.49 PR-H 2-Year 2 5,344 726.00 1.47 PR-H 10-Year 10 8,908 726.00 2.38 PR-H 100-Year 100 13,511 726.00 3.51 PR-G 2-Year 2 31,328 726.50 9.03 PR-G 10-Year 10 58,200 726.00 16.47 PR-G 100-Year 100 94,483 726.00 26.12 PR-J 2-Year 2 3,612 726.00 1.01 PR-J 10-Year 10 6,101 726.00 1.65 PR-J 100-Year 100 9,330 726.00 2.45 PR-Pond J 2-Year 2 654 728.00 0.13 PR-Pond J 10-Year 10 1,935 727.00 0.52 PR-Pond J 100-Year 100 4,085 726.50 1.17 PR-Pond B 2-Year 2 1,077 728.00 0.21

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 2 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Master Network Summary

Catchments Summary Label Scenario Return Hydrograph Volume Time to Peak Peak Flow Event (ft³) (min) (ft³/s) (years) PR-Pond B 10-Year 10 3,186 727.00 0.86 PR-Pond B 100-Year 100 6,725 726.50 1.92 PR-K 2-Year 2 1,578 739.50 0.18 PR-K 10-Year 10 5,713 727.50 1.39 PR-K 100-Year 100 13,208 727.00 3.68

Node Summary Label Scenario Return Hydrograph Volume Time to Peak Peak Flow Event (ft³) (min) (ft³/s) (years) F - 52 DP-F 2-Year 2 3,220 727.50 0.67 DP-F 10-Year 10 9,222 727.00 2.52 DP-F 100-Year 100 22,764 726.50 5.49 DP-H 2-Year 2 5,344 726.00 1.47 DP-H 10-Year 10 8,908 726.00 2.38 DP-H 100-Year 100 13,511 726.00 3.51 DP-D 2-Year 2 1,373 726.00 0.34 DP-D 10-Year 10 2,115 726.00 0.52 DP-D 100-Year 100 3,056 726.00 0.74 DP-C 2-Year 2 12,829 726.50 3.70 DP-C 10-Year 10 24,527 726.50 7.00 DP-C 100-Year 100 40,539 726.00 11.32 DP-CG1 2-Year 2 44,128 727.00 12.66 DP-CG1 10-Year 10 82,685 726.50 23.38 DP-CG1 100-Year 100 135,294 723.00 43.37 DP-G 2-Year 2 31,328 726.50 9.03 DP-G 10-Year 10 58,200 726.00 16.47

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 3 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Master Network Summary

Node Summary Label Scenario Return Hydrograph Volume Time to Peak Peak Flow Event (ft³) (min) (ft³/s) (years) DP-G 100-Year 100 94,483 726.00 26.12 DP-CG2 2-Year 2 44,102 727.50 12.61 DP-CG2 10-Year 10 82,648 727.00 23.33 DP-CG2 100-Year 100 136,216 720.00 29.63 DP-B 2-Year 2 3,408 852.00 0.23 DP-B 10-Year 10 16,734 747.00 2.42 DP-B 100-Year 100 35,460 743.00 4.67 DP-BCDEG 2-Year 2 48,855 728.00 12.89 DP-BCDEG 10-Year 10 101,454 728.00 24.43 DP-BCDEG 100-Year 100 175,563 740.00 34.34

F - 53 12+85 MH 2-Year 2 48,821 728.50 12.83 12+85 MH 10-Year 10 101,402 728.50 24.32 12+85 MH 100-Year 100 176,477 721.50 31.33 DP-A 2-Year 2 17,463 726.50 5.01 DP-A 10-Year 10 31,550 726.00 8.84 DP-A 100-Year 100 50,329 726.00 13.75 30" Outfall 2-Year 2 48,791 729.00 12.79 30" Outfall 10-Year 10 101,356 729.00 24.24 30" Outfall 100-Year 100 176,414 738.50 31.33 DP-River 2-Year 2 66,254 727.50 17.48 DP-River 10-Year 10 132,906 727.50 32.44 DP-River 100-Year 100 226,743 726.00 45.08 DP-K 2-Year 2 1,578 739.50 0.18 DP-K 10-Year 10 5,713 727.50 1.39 DP-K 100-Year 100 13,208 727.00 3.68

Pond Summary

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 4 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Master Network Summary

Pond Summary Label Scenario Return Hydrograph Time to Peak Peak Flow Maximum Water Maximum Pond Event Volume (min) (ft³/s) Surface Elevation Storage (years) (ft³) (ft) (ft³) Infiltration Basin 2-Year 2 15,157 727.00 3.98 (N/A) (N/A) B (IN) Infiltration Basin 2-Year 2 3,408 852.00 0.23 133.01 8,258 B (OUT) Infiltration Basin 10-Year 10 29,283 726.50 6.86 (N/A) (N/A) B (IN) Infiltration Basin 10-Year 10 16,734 747.00 2.42 133.71 11,368 B (OUT) Infiltration Basin 100-Year 100 48,788 726.50 11.53 (N/A) (N/A) B (IN) Infiltration Basin 100-Year 100 35,460 743.00 4.67 134.75 16,703

F - 54 B (OUT) Forebay B (IN) 2-Year 2 15,461 726.50 4.42 (N/A) (N/A) Forebay B (OUT) 2-Year 2 14,080 727.00 3.78 133.02 1,759 Forebay B (IN) 10-Year 10 27,553 726.00 7.68 (N/A) (N/A) Forebay B (OUT) 10-Year 10 26,097 726.50 6.01 133.71 2,608 Forebay B (IN) 100-Year 100 43,576 726.00 11.83 (N/A) (N/A) Forebay B (OUT) 100-Year 100 42,062 726.50 9.61 134.76 4,146 Forebay J (IN) 2-Year 2 3,612 726.00 1.01 (N/A) (N/A) Forebay J (OUT) 2-Year 2 3,612 726.50 1.00 128.11 29 Forebay J (IN) 10-Year 10 6,101 726.00 1.65 (N/A) (N/A) Forebay J (OUT) 10-Year 10 6,100 726.50 1.64 128.18 48 Forebay J (IN) 100-Year 100 9,330 726.00 2.45 (N/A) (N/A) Forebay J (OUT) 100-Year 100 9,329 726.50 2.44 128.27 71 Infiltration Basin 2-Year 2 4,266 727.00 1.12 (N/A) (N/A) J (IN) Infiltration Basin 2-Year 2 0 0.00 0.00 124.39 1,911 J (OUT)

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 5 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Master Network Summary

Pond Summary Label Scenario Return Hydrograph Time to Peak Peak Flow Maximum Water Maximum Pond Event Volume (min) (ft³/s) Surface Elevation Storage (years) (ft³) (ft) (ft³) Infiltration Basin 10-Year 10 8,036 726.50 2.16 (N/A) (N/A) J (IN) Infiltration Basin 10-Year 10 0 0.00 0.00 125.58 4,198 J (OUT) Infiltration Basin 100-Year 100 13,414 726.50 3.61 (N/A) (N/A) J (IN) Infiltration Basin 100-Year 100 3,602 736.00 1.66 125.89 4,952 J (OUT) F - 55

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 6 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time-Depth Curve Return Event: 100 years Label: Type III 24-hr Northampton Storm Event: 100-year, 24-hr rainfall

Time-Depth Curve: 100-year, 24-hr rainfall 100-year, 24-hr Label rainfall Start Time 0.00 min Increment 6.00 min End Time 1,440.00 min Return Event 100 years

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in)

F - 56 0.00 0.0 0.0 0.0 0.0 0.0 30.00 0.0 0.0 0.0 0.1 0.1 60.00 0.1 0.1 0.1 0.1 0.1 90.00 0.1 0.1 0.1 0.1 0.1 120.00 0.1 0.1 0.1 0.1 0.2 150.00 0.2 0.2 0.2 0.2 0.2 180.00 0.2 0.2 0.2 0.2 0.2 210.00 0.2 0.2 0.3 0.3 0.3 240.00 0.3 0.3 0.3 0.3 0.3 270.00 0.3 0.3 0.3 0.3 0.4 300.00 0.4 0.4 0.4 0.4 0.4 330.00 0.4 0.4 0.4 0.4 0.5 360.00 0.5 0.5 0.5 0.5 0.5 390.00 0.5 0.5 0.5 0.6 0.6 420.00 0.6 0.6 0.6 0.6 0.6 450.00 0.7 0.7 0.7 0.7 0.7 480.00 0.7 0.7 0.8 0.8 0.8 510.00 0.8 0.8 0.9 0.9 0.9 Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 7 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time-Depth Curve Return Event: 100 years Label: Type III 24-hr Northampton Storm Event: 100-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 540.00 0.9 1.0 1.0 1.0 1.0 570.00 1.1 1.1 1.1 1.1 1.2 600.00 1.2 1.2 1.3 1.3 1.3 630.00 1.4 1.4 1.5 1.5 1.6 660.00 1.6 1.6 1.7 1.8 1.8 690.00 1.9 2.0 2.2 2.4 2.7 720.00 3.2 3.7 4.0 4.2 4.4 750.00 4.5 4.6 4.6 4.7 4.8 780.00 4.8 4.8 4.9 4.9 5.0 F - 57 810.00 5.0 5.1 5.1 5.1 5.2 840.00 5.2 5.2 5.3 5.3 5.3 870.00 5.3 5.4 5.4 5.4 5.4 900.00 5.5 5.5 5.5 5.5 5.6 930.00 5.6 5.6 5.6 5.6 5.7 960.00 5.7 5.7 5.7 5.7 5.7 990.00 5.7 5.8 5.8 5.8 5.8 1,020.00 5.8 5.8 5.8 5.9 5.9 1,050.00 5.9 5.9 5.9 5.9 5.9 1,080.00 5.9 5.9 6.0 6.0 6.0 1,110.00 6.0 6.0 6.0 6.0 6.0 1,140.00 6.0 6.0 6.1 6.1 6.1 1,170.00 6.1 6.1 6.1 6.1 6.1 1,200.00 6.1 6.1 6.1 6.1 6.2 1,230.00 6.2 6.2 6.2 6.2 6.2 1,260.00 6.2 6.2 6.2 6.2 6.2 1,290.00 6.2 6.2 6.3 6.3 6.3

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 8 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time-Depth Curve Return Event: 100 years Label: Type III 24-hr Northampton Storm Event: 100-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 1,320.00 6.3 6.3 6.3 6.3 6.3 1,350.00 6.3 6.3 6.3 6.3 6.3 1,380.00 6.3 6.3 6.4 6.4 6.4 1,410.00 6.4 6.4 6.4 6.4 6.4 1,440.00 6.4 (N/A) (N/A) (N/A) (N/A) F - 58

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 9 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time-Depth Curve Return Event: 10 years Label: Type III 24-hr Northampton Storm Event: 10-year, 24-hr rainfall

Time-Depth Curve: 10-year, 24-hr rainfall 10-year, 24-hr Label rainfall Start Time 0.00 min Increment 6.00 min End Time 1,440.00 min Return Event 10 years

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in)

F - 59 0.00 0.0 0.0 0.0 0.0 0.0 30.00 0.0 0.0 0.0 0.0 0.0 60.00 0.0 0.0 0.1 0.1 0.1 90.00 0.1 0.1 0.1 0.1 0.1 120.00 0.1 0.1 0.1 0.1 0.1 150.00 0.1 0.1 0.1 0.1 0.1 180.00 0.1 0.1 0.1 0.2 0.2 210.00 0.2 0.2 0.2 0.2 0.2 240.00 0.2 0.2 0.2 0.2 0.2 270.00 0.2 0.2 0.2 0.2 0.2 300.00 0.3 0.3 0.3 0.3 0.3 330.00 0.3 0.3 0.3 0.3 0.3 360.00 0.3 0.3 0.3 0.3 0.4 390.00 0.4 0.4 0.4 0.4 0.4 420.00 0.4 0.4 0.4 0.4 0.4 450.00 0.5 0.5 0.5 0.5 0.5 480.00 0.5 0.5 0.5 0.6 0.6 510.00 0.6 0.6 0.6 0.6 0.6 Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 10 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time-Depth Curve Return Event: 10 years Label: Type III 24-hr Northampton Storm Event: 10-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 540.00 0.7 0.7 0.7 0.7 0.7 570.00 0.7 0.8 0.8 0.8 0.8 600.00 0.9 0.9 0.9 0.9 0.9 630.00 1.0 1.0 1.0 1.1 1.1 660.00 1.1 1.2 1.2 1.2 1.3 690.00 1.3 1.4 1.5 1.7 1.9 720.00 2.2 2.6 2.8 3.0 3.1 750.00 3.2 3.2 3.3 3.3 3.3 780.00 3.4 3.4 3.4 3.5 3.5 F - 60 810.00 3.5 3.6 3.6 3.6 3.6 840.00 3.6 3.7 3.7 3.7 3.7 870.00 3.8 3.8 3.8 3.8 3.8 900.00 3.8 3.9 3.9 3.9 3.9 930.00 3.9 3.9 3.9 4.0 4.0 960.00 4.0 4.0 4.0 4.0 4.0 990.00 4.0 4.1 4.1 4.1 4.1 1,020.00 4.1 4.1 4.1 4.1 4.1 1,050.00 4.1 4.1 4.2 4.2 4.2 1,080.00 4.2 4.2 4.2 4.2 4.2 1,110.00 4.2 4.2 4.2 4.2 4.2 1,140.00 4.2 4.3 4.3 4.3 4.3 1,170.00 4.3 4.3 4.3 4.3 4.3 1,200.00 4.3 4.3 4.3 4.3 4.3 1,230.00 4.3 4.3 4.3 4.4 4.4 1,260.00 4.4 4.4 4.4 4.4 4.4 1,290.00 4.4 4.4 4.4 4.4 4.4

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 11 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time-Depth Curve Return Event: 10 years Label: Type III 24-hr Northampton Storm Event: 10-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 1,320.00 4.4 4.4 4.4 4.4 4.4 1,350.00 4.4 4.4 4.4 4.5 4.5 1,380.00 4.5 4.5 4.5 4.5 4.5 1,410.00 4.5 4.5 4.5 4.5 4.5 1,440.00 4.5 (N/A) (N/A) (N/A) (N/A) F - 61

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 12 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time-Depth Curve Return Event: 2 years Label: Type III 24-hr Northampton Storm Event: 2-year, 24-hr rainfall

Time-Depth Curve: 2-year, 24-hr rainfall 2-year, 24-hr Label rainfall Start Time 0.00 min Increment 6.00 min End Time 1,440.00 min Return Event 2 years

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in)

F - 62 0.00 0.0 0.0 0.0 0.0 0.0 30.00 0.0 0.0 0.0 0.0 0.0 60.00 0.0 0.0 0.0 0.0 0.0 90.00 0.0 0.0 0.1 0.1 0.1 120.00 0.1 0.1 0.1 0.1 0.1 150.00 0.1 0.1 0.1 0.1 0.1 180.00 0.1 0.1 0.1 0.1 0.1 210.00 0.1 0.1 0.1 0.1 0.1 240.00 0.1 0.1 0.1 0.1 0.1 270.00 0.1 0.2 0.2 0.2 0.2 300.00 0.2 0.2 0.2 0.2 0.2 330.00 0.2 0.2 0.2 0.2 0.2 360.00 0.2 0.2 0.2 0.2 0.2 390.00 0.2 0.2 0.3 0.3 0.3 420.00 0.3 0.3 0.3 0.3 0.3 450.00 0.3 0.3 0.3 0.3 0.3 480.00 0.3 0.3 0.4 0.4 0.4 510.00 0.4 0.4 0.4 0.4 0.4 Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 13 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time-Depth Curve Return Event: 2 years Label: Type III 24-hr Northampton Storm Event: 2-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 540.00 0.4 0.4 0.5 0.5 0.5 570.00 0.5 0.5 0.5 0.5 0.6 600.00 0.6 0.6 0.6 0.6 0.6 630.00 0.6 0.7 0.7 0.7 0.7 660.00 0.7 0.8 0.8 0.8 0.9 690.00 0.9 0.9 1.0 1.1 1.2 720.00 1.5 1.8 1.9 2.0 2.1 750.00 2.1 2.1 2.2 2.2 2.2 780.00 2.2 2.3 2.3 2.3 2.3 F - 63 810.00 2.4 2.4 2.4 2.4 2.4 840.00 2.4 2.4 2.5 2.5 2.5 870.00 2.5 2.5 2.5 2.5 2.6 900.00 2.6 2.6 2.6 2.6 2.6 930.00 2.6 2.6 2.6 2.6 2.7 960.00 2.7 2.7 2.7 2.7 2.7 990.00 2.7 2.7 2.7 2.7 2.7 1,020.00 2.7 2.7 2.7 2.7 2.8 1,050.00 2.8 2.8 2.8 2.8 2.8 1,080.00 2.8 2.8 2.8 2.8 2.8 1,110.00 2.8 2.8 2.8 2.8 2.8 1,140.00 2.8 2.8 2.8 2.8 2.8 1,170.00 2.9 2.9 2.9 2.9 2.9 1,200.00 2.9 2.9 2.9 2.9 2.9 1,230.00 2.9 2.9 2.9 2.9 2.9 1,260.00 2.9 2.9 2.9 2.9 2.9 1,290.00 2.9 2.9 2.9 2.9 2.9

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 14 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time-Depth Curve Return Event: 2 years Label: Type III 24-hr Northampton Storm Event: 2-year, 24-hr rainfall

CUMULATIVE RAINFALL (in) Output Time Increment = 6.00 min Time on left represents time for first value in each row. Time Depth Depth Depth Depth Depth (min) (in) (in) (in) (in) (in) 1,320.00 2.9 2.9 2.9 3.0 3.0 1,350.00 3.0 3.0 3.0 3.0 3.0 1,380.00 3.0 3.0 3.0 3.0 3.0 1,410.00 3.0 3.0 3.0 3.0 3.0 1,440.00 3.0 (N/A) (N/A) (N/A) (N/A) F - 64

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 15 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-A Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 65

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 16 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-A Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 66

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 17 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-B Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 67

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 18 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-B Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 68

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 19 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-C Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 69

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 20 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-C Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 70

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 21 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-D Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 71

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 22 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-D Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 72

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 23 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-F Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 73

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 24 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-F Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 74

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 25 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-G Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 75

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 26 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-G Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 76

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 27 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-H Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 77

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 28 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-H Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 78

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 29 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-J Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 79

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 30 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-J Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 80

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 31 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-K Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 81

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 32 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-K Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 82

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 33 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-Pond B Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 83

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 34 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-Pond B Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 84

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 35 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-Pond J Storm Event: 2-year, 24-hr rainfall

Time of Concentration Results Segment #1: User Defined Tc Time of Concentration 5.00 min

Time of Concentration (Composite) Time of Concentration 5.00 min (Composite) F - 85

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 36 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Time of Concentration Calculations Return Event: 2 years Label: PR-Pond J Storm Event: 2-year, 24-hr rainfall

==== User Defined Tc = Value entered by user Where: Tc= Time of concentration, hours F - 86

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 37 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-A Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 84,893 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 38,361 0.0 0.0 61.000 cover > 75% - Soil B Woods - good - Soil B 55.000 2,908 0.0 0.0 55.000 COMPOSITE AREA & WEIGHTED CN ---> (N/A) 126,162 (N/A) (N/A) 85.759 F - 87

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 38 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-B Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 73,887 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 32,888 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 106,775 (N/A) (N/A) 86.604 F - 88

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 39 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-C Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 62,438 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 49,310 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 111,748 (N/A) (N/A) 81.673 F - 89

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 40 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-D Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 5,956 0.0 0.0 98.000 driveways, Streets and roads - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 5,956 (N/A) (N/A) 98.000 F - 90

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 41 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-F Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 13,969 0.0 0.0 98.000 driveways, Streets and roads - Soil B Brush - brush, weed, grass mix - good - Soil B 48.000 24,916 0.0 0.0 48.000 Pasture, grassland, or range - good - Soil B 61.000 27,100 0.0 0.0 61.000 Woods - grass combination - good - Soil B 58.000 31,205 0.0 0.0 58.000 COMPOSITE AREA & WEIGHTED CN ---> (N/A) 97,190 (N/A) (N/A) 62.022 F - 91

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 42 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-G Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 154,965 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 93,199 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 248,164 (N/A) (N/A) 84.104 F - 92

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 43 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-H Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 25,013 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 4,685 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 29,698 (N/A) (N/A) 92.163 F - 93

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 44 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-J Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 16,720 0.0 0.0 98.000 driveways, Streets and roads - Soil B Open space (Lawns,parks etc.) - Good condition; grass 61.000 4,224 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 20,944 (N/A) (N/A) 90.538 F - 94

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 45 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-K Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Impervious Areas - Paved parking lots, roofs, 98.000 2,974 0.0 0.0 98.000 driveways, Streets and roads - Soil B Brush - brush, weed, grass mix - good - Soil B 48.000 28,655 0.0 0.0 48.000 Woods - grass combination - good - Soil B 58.000 54,713 0.0 0.0 58.000 COMPOSITE AREA & WEIGHTED CN ---> (N/A) 86,342 (N/A) (N/A) 56.059 F - 95

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 46 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-Pond B Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Open space (Lawns,parks etc.) - Good condition; grass 61.000 35,471 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 35,471 (N/A) (N/A) 61.000 F - 96

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 47 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Subsection: Runoff CN-Area Return Event: 2 years Label: PR-Pond J Storm Event: 2-year, 24-hr rainfall

Runoff Curve Number Data Soil/Surface Description CN Area C UC Adjusted CN (ft²) (%) (%) Open space (Lawns,parks etc.) - Good condition; grass 61.000 21,547 0.0 0.0 61.000 cover > 75% - Soil B COMPOSITE AREA & WEIGHTED CN ---> (N/A) 21,547 (N/A) (N/A) 61.000 F - 97

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 48 of 50 +1-203-755-1666 604597 - Proposed Drainage Model Index M

Master Network Summary...2, 3, 4, 5, 6

P

PR-A (Runoff CN-Area, 2 years)...38 PR-A (Time of Concentration Calculations, 2 years)...16, 17 PR-B (Runoff CN-Area, 2 years)...39 PR-B (Time of Concentration Calculations, 2 years)...18, 19 PR-C (Runoff CN-Area, 2 years)...40 PR-C (Time of Concentration Calculations, 2 years)...20, 21

F - 98 PR-D (Runoff CN-Area, 2 years)...41 PR-D (Time of Concentration Calculations, 2 years)...22, 23 PR-F (Runoff CN-Area, 2 years)...42 PR-F (Time of Concentration Calculations, 2 years)...24, 25 PR-G (Runoff CN-Area, 2 years)...43 PR-G (Time of Concentration Calculations, 2 years)...26, 27 PR-H (Runoff CN-Area, 2 years)...44 PR-H (Time of Concentration Calculations, 2 years)...28, 29 PR-J (Runoff CN-Area, 2 years)...45

PR-J (Time of Concentration Calculations, 2 years)...30, 31

PR-K (Runoff CN-Area, 2 years)...46 Bentley PondPack V8i NorthamptonPR-K (Time Proposed.ppc of Concentration Calculations, 2 years)...32, Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/201733 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 49 of 50 +1-203-755-1666 PR-Pond B (Runoff CN-Area, 2 years)...47 PR-Pond B (Time of Concentration Calculations, 2 years)...34, 35 PR-Pond J (Runoff CN-Area, 2 years)...48 PR-Pond J (Time of Concentration Calculations, 2 years)...36, 37 T Type III 24-hr Northampton (Time-Depth Curve, 10 years)...10, 11, 12 Type III 24-hr Northampton (Time-Depth Curve, 100 years)...7, 8, 9 Type III 24-hr Northampton (Time-Depth Curve, 2 years)...13, 14, 15 M

Master Network Summary...2, 3, 4, 5, 6

P

PR-A (Runoff CN-Area, 2 years)...38 PR-A (Time of Concentration Calculations, 2 years)...16, 17 PR-B (Runoff CN-Area, 2 years)...39 PR-B (Time of Concentration Calculations, 2 years)...18, 19 PR-C (Runoff CN-Area, 2 years)...40 PR-C (Time of Concentration Calculations, 2 years)...20, 21 PR-D (Runoff CN-Area, 2 years)...41 PR-D (Time of Concentration Calculations, 2 years)...22, 23 PR-F (Runoff CN-Area, 2 years)...42 PR-F (Time of Concentration Calculations, 2 years)...24, 25 PR-G (Runoff CN-Area, 2 years)...43 PR-G (Time of Concentration Calculations, 2 years)...26, 27 PR-H (Runoff CN-Area, 2 years)...44 PR-H (Time of Concentration Calculations, 2 years)...28, 29 PR-J (Runoff CN-Area, 2 years)...45 PR-J (Time of Concentration Calculations, 2 years)...30,604597 31 - Proposed Drainage Model PR-K (Runoff CN-Area, 2 years)...46 PR-K (Time of Concentration Calculations, 2 years)...32, 33 PR-Pond B (Runoff CN-Area, 2 years)...47 PR-Pond B (Time of Concentration Calculations, 2 years)...34, 35 PR-Pond J (Runoff CN-Area, 2 years)...48 PR-Pond J (Time of Concentration Calculations, 2 years)...36, 37 T Type III 24-hr Northampton (Time-Depth Curve, 10 years)...10, 11, 12 Type III 24-hr Northampton (Time-Depth Curve, 100 years)...7, 8, 9 Type III 24-hr Northampton (Time-Depth Curve, 2 years)...13, 14, 15 F - 99

Bentley PondPack V8i Northampton Proposed.ppc Bentley Systems, Inc. Haestad Methods Solution Center [08.11.01.56] 10/25/2017 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 50 of 50 +1-203-755-1666

ATTACHMENT G- Test Pit Logs

Pages G-1 - G-8

Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

TEST PIT LOG

PROJECT TEST PIT NO. TP-1 Interstate 91 and Route 9 SHEET 1 of 2 Intersection ReconstructionFILE NO. 92470.00 Northampton, Massachusetts CHKD BY Jorge Fuentes

EngineerPatrick Clarke Make Kobelco Ground El. ~135 ContractorNew England Boring Model SK55SRX Datum NAVD88 OperatorJohn Galvin Capacity ~5.7 Cubic Feet Time Start 12:45 WeatherSnow, 30°'s Reach ~12 feet Date 2/1/2017

Depth Strata Below Change & Subsurface Description Excavation Boulder USDA Grade Water Effort Qty/Class Textural (ft) Level Class TOPSOIL Dark brown, SILT, trace fine to medium Sand, moist (TOPSOIL). - 0.3' 1

2

3

4

G-1) Light brown, fine SAND, some Silt, dry (FILL). [Laboratory 5 Loamy FILL Analysis Performed: Grain Size Analysis (Sieve & Hydrometer) - E - Sand 6 Gravel = 0.0%, Sand = 73.2%, Silt & Clay = 26.8%].

7

8

9

10 10' Groundwater table not encountered. Test pit terminated at 11 approximately 10 feet below ground surface.

12

13

14

15 Notes: 1.) Test pit backfilled with excavated soils and compacted with excavator bucket WATER SYMBOLS at ground surface. Groundwater 2.) Ground surface elevation interpolated from provided plans and should be Estimated Seasonal High Groundwater considered approximate. BOULDER CLASS PROPORTIONS USED EXCAVATION EFFORT ~14' 12" - 24" A 0-10% Trace E = Easy N 24" - 36" B 10-20% Little M = Moderate ~4' >36" C 20-35% Some D = Difficult 35-50% And

G - 1 TEST PIT LOG

PROJECT TEST PIT NO. TP-1 Interstate 91 and Route 9 SHEET 2 of 2 Intersection ReconstructionFILE NO. 92470.00 Northampton, Massachusetts CHKD BY Jorge Fuentes

EngineerPatrick Clarke Make Kobelco Ground El. ~135 ContractorNew England Boring Model SK55SRX Datum NAVD88 OperatorJohn Galvin Capacity ~5.7 Cubic Feet Time Start 12:45 WeatherSnow, 30°'s Reach ~12 feet Date 2/1/2017

TOPSOIL

G-1

Notes: 1.) Photo of in-progress TP-1.

~14' N ~4'

G - 2 TEST PIT LOG

PROJECT TEST PIT NO. TP-2 Interstate 91 and Route 9 SHEET 1 of 2 Intersection ReconstructionFILE NO. 92470.00 Northampton, Massachusetts CHKD BY Jorge Fuentes

EngineerPatrick Clarke Make Kobelco Ground El. ~122 ContractorNew England Boring Model SK55SRX Datum NAVD88 OperatorJohn Galvin Capacity ~5.7 Cubic Feet Time Start 11:45 WeatherSnow, 30°'s Reach ~12 feet Date 2/1/2017

Depth Strata Below Change & Subsurface Description Excavation Boulder USDA Grade Water Effort Qty/Class Textural (ft) Level Class TOPSOIL Dark brown, SILT, trace fine to medium Sand, moist (TOPSOIL). E - 0.3' G-1) Brown, fine to coarse SAND, some fine to coarse Gravel, Gravelly, 1 M 1.5' little Silt, very few asphalt particles, very few roots, moist (FILL). Loamy Sand 2

3 G-2) Brown, fine to coarse SAND, some fine to coarse Gravel, trace Silt, very few cobbles, dry to wet (FILL). Perched water Gravelly 4 infiltrating corner of excavation at depth of approximately 5 feet Sand below ground surface. 5 - FILL 5.5' 6 E

G-3) Brown, SILT & CLAY, trace fine Sand, wet (FILL). 7 [Laboratory Analysis Performed: Grain Size Analysis (Sieve & Silt Loam Hydrometer) - Gravel = 0.0%, Sand = 2.1%, Silt & Clay = 97.9%]. 8 8.5' 9 Sandy G-4) Brown, fine SAND and Silt, dry (FILL). Loam 10 10' Groundwater table not encountered. Test pit terminated at 11 approximately 10 feet below ground surface.

12

13

14

15 Notes: 1.) Test pit backfilled with excavated soils and compacted with excavator bucket WATER SYMBOLS at ground surface. Groundwater 2.) Ground surface elevation interpolated from provided plans and should be Estimated Seasonal High Groundwater considered approximate. BOULDER CLASS PROPORTIONS USED EXCAVATION EFFORT ~13' 12" - 24" A 0-10% Trace E = Easy 24" - 36" B 10-20% Little M = Moderate ~3' N >36" C 20-35% Some D = Difficult 35-50% And

G - 3 TEST PIT LOG

PROJECT TEST PIT NO. TP-2 Interstate 91 and Route 9 SHEET 2 of 2 Intersection ReconstructionFILE NO. 92470.00 Northampton, Massachusetts CHKD BY Jorge Fuentes

EngineerPatrick Clarke Make Kobelco Ground El. ~122 ContractorNew England Boring Model SK55SRX Datum NAVD88 OperatorJohn Galvin Capacity ~5.7 Cubic Feet Time Start 11:45 WeatherSnow, 30°'s Reach ~12 feet Date 2/1/2017

TOPSOIL Very few cobbles

G-1

G-2

G-3

G-4

Perched water infiltration

Notes: 1.) Photo of completed TP-2.

~13'

~3' N

G - 4 TEST PIT LOG

PROJECT TEST PIT NO. TP-3 Interstate 91 and Route 9 SHEET 1 of 2 Intersection ReconstructionFILE NO. 92470.00 Northampton, Massachusetts CHKD BY Jorge Fuentes

EngineerPatrick Clarke Make Kobelco Ground El. ~127 ContractorNew England Boring Model SK55SRX Datum NAVD88 OperatorJohn Galvin Capacity ~5.7 Cubic Feet Time Start 10:30 WeatherSnow, 30°'s Reach ~12 feet Date 2/1/2017

Depth Strata Below Change & Subsurface Description Excavation Boulder USDA Grade Water Effort Qty/Class Textural (ft) Level Class TOPSOIL Dark brown, SILT, some fine to coarse Sand, trace fine Gravel, moist (TOPSOIL). - 0.3' 1

2

3

G-1) Brown, fine to coarse SAND, little fine to coarse Gravel, 4 Sand trace Silt, very few cobbles, dry (FILL). 5 FILL E - 6

7 7.3' G-2) Gray to dark gray, Clayey SILT, some fine to medium Sand, very few roots, Silt Loam 8 8' organic-like odor, dry (FILL). [Laboratory Analysis Performed: Grain Size Analysis

9 G-3) Brown, fine to coarse SAND, some fine to coarse Gravel, Gravelly trace Silt, dry (FILL). Sand 10 10' Groundwater table not encountered. Test pit terminated at 11 approximately 10 feet below ground surface.

12

13

14

15 Notes: 1.) Test pit backfilled with excavated soils and compacted with excavator bucket WATER SYMBOLS at ground surface. Groundwater 2.) Ground surface elevation interpolated from provided plans and should be Estimated Seasonal High Groundwater considered approximate. BOULDER CLASS PROPORTIONS USED EXCAVATION EFFORT ~17.5' 12" - 24" A 0-10% Trace E = Easy 24" - 36" B 10-20% Little M = Moderate ~2.5' N >36" C 20-35% Some D = Difficult 35-50% And

G - 5 TEST PIT LOG

PROJECT TEST PIT NO. TP-3 Interstate 91 and Route 9 SHEET 2 of 2 Intersection ReconstructionFILE NO. 92470.00 Northampton, Massachusetts CHKD BY Jorge Fuentes

EngineerPatrick Clarke Make Kobelco Ground El. ~127 ContractorNew England Boring Model SK55SRX Datum NAVD88 OperatorJohn Galvin Capacity ~5.7 Cubic Feet Time Start 10:30 WeatherSnow, 30°'s Reach ~12 feet Date 2/1/2017

TOPSOIL

G-1

G-2

G-3

Notes: 1.) Photo of completed TP-3.

~17.5'

~2.5' N

G - 6 TEST PIT LOG

PROJECT TEST PIT NO. TP-4 Interstate 91 and Route 9 SHEET 1 of 2 Intersection Reconstruction FILE NO. 92470.00 Northampton, Massachusetts CHKD BY Jorge Fuentes

EngineerPatrick Clarke Make Kobelco Ground El. ~134 ContractorNew England Boring Model SK55SRX Datum NAVD88 OperatorJohn Galvin Capacity ~5.7 Cubic Feet Time Start 9:30 WeatherSnow, 30°'s Reach ~12 feet Date 2/1/2017

Depth Strata Below Change & Subsurface Description Excavation Boulder USDA Grade Water Effort Qty/Class Textural (ft) Level Class TOPSOIL Dark brown, SILT, trace fine to medium Sand, moist (TOPSOIL). - 0.3' 1 G-1) Brown/gray, fine to coarse SAND and Clayey Silt, little fine E Loam 2 to coarse Gravel, very few cobbles, very few roots, moist (FILL). 2.5' 3 G-2) Reddish brown, fine to medium SAND, some Silt, trace fine Gravel, moist Sandy (FILL). [Laboratory Analysis Performed: Grain Size Analysis (Sieve & Hydrometer) D - Gravel = 2.9%, Sand = 73.1%, Silt & Clay = 24.0%]. Loam 4 4' G-1) Brown, fine to coarse SAND and Clayey Silt, little fine to coarse FILL M- Loam 5 4.8' Gravel, very few cobbles, very few roots, moist (FILL). G-2) Reddish brown, fine to medium SAND, some Silt, trace fine Sandy D to coarse Gravel, moist (FILL). Loam 6 5.8' G-3) Reddish brown, fine to coarse SAND, little fine to coarse Gravelly 7 7' Gravel, trace Silt, dry (FILL). Sand M Very G-4) Reddish brown, fine to coarse SAND and fine to coarse 8 Gravelly Gravel, trace Silt, dry (FILL). Sand 8.8' 9 Groundwater table not encountered. Test pit terminated at approximately 8.8 feet below ground surface. 10

11

12

13

14

15 Notes: 1.) Test pit backfilled with excavated soils and compacted with excavator bucket WATER SYMBOLS at ground surface. Groundwater 2.) Ground surface elevation interpolated from provided plans and should be Estimated Seasonal High Groundwater considered approximate. BOULDER CLASS PROPORTIONS USED EXCAVATION EFFORT ~13' 12" - 24" A 0-10% Trace E = Easy 24" - 36" B 10-20% Little M = Moderate ~4' N >36" C 20-35% Some D = Difficult 35-50% And

G - 7 TEST PIT LOG

PROJECT TEST PIT NO. TP-4 Interstate 91 and Route 9 SHEET 2 of 2 Intersection Reconstruction FILE NO. 92470.00 Northampton, Massachusetts CHKD BY Jorge Fuentes

EngineerPatrick Clarke Make Kobelco Ground El. ~134 ContractorNew England Boring Model SK55SRX Datum NAVD88 OperatorJohn Galvin Capacity ~5.7 Cubic Feet Time Start 9:30 WeatherSnow, 30°'s Reach ~12 feet Date 2/1/2017

TOPSOIL

G-1

G-2

G-1

G-2

G-3

G-4

Notes: 1.) Photo of completed TP-4.

~13'

~4' N

G - 8

ATTACHMENT H- Long Term Pollution Prevention Plan (LTPPP)

Pages H-1 - H-4

Stormwater Report Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

Long Term Pollution Prevention Plan (LTPPP)

Highway Plans The highway plans and details include erosion and sediment control measures that will be installed.

Materials Covered The following materials or substances are expected to be present onsite during construction.  Concrete/Additives/Wastes  Petroleum based products  Solid and construction wastes  Sanitary wastes

Materials Management Practices The following material management practices will be implemented onsite during construction to reduce the risk of spills or other accidental exposure of materials and substances to stormwater runoff. The contractor’s superintendent will be responsible for ensuring that these procedures are followed.

1. Good Housekeeping The following good housekeeping practices will be implemented onsite during construction. a. An effort will be made to store only enough products required to do the job. b. All materials onsite will be stored in a neat and orderly manner. If possible, materials will be stored under a roof or in a containment area. At a minimum, all containers will be covered with proper lids when not in use, and drip pans will be provided under all dispensers. c. Products will be kept in their original containers, with the original manufacturer’s label in legible condition. d. Substances will not be mixed with one another unless recommended by the manufacturer. e. Whenever possible, all products will be used before disposing the container. f. Manufacturer’s recommendations for proper use and disposal will be followed. g. The Contractor’s superintendent will be responsible for daily inspections to ensure proper use and disposal of materials.

2. Hazardous Substances The following practices will be implemented to reduce the risks associated with hazardous substances. Material Safety Data Sheets (MSDS’s) will be obtained for each product onsite that has hazardous properties, and used for the proper management of potential wastes that may result from these products. Each employee who must handle a hazardous substance will be instructed on the use of MSDS sheets and the specific information in the applicable MSDS for the product he/she is using, particularly regarding spill control techniques. a. Products will be kept in original containers with the original labels in legible condition.

H - 1 LTPPP Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

b. Original labels and MSDS’s will be procured and used for each product. c. If surplus product must be disposed, it will be disposed according to manufacturer’s and local/state/federal methods for proper disposal.

3. Hazardous Waste All hazardous waste must be properly identified and handled in accordance with all applicable hazardous waste standards, including the storage, transport and disposal of the hazardous wastes. There are significant penalties for the improper handling of hazardous wastes. It is important that the site superintendent seek appropriate assistance in making the determination of whether a substance or material is a hazardous waste.

4. Product Specific Practices The following product specific practices will be implemented on the job site. a. Petroleum Products—All onsite vehicles will be monitored for leaks and receive regular preventive maintenance to reduce the chance of leakage. Petroleum products will be stored in tightly sealed containers that are clearly labeled. b. Concrete Wastes—Concrete trucks will be allowed to wash out or discharge surplus concrete or drum wash water on the project site, but only in specifically designated diked and impervious washout areas, which are prepared to prevent contact between the concrete wash and stormwater. Waste generated from concrete wash water must not be allowed to flow into drainage ways, inlets, receiving waters or any location other than the designated concrete washout area. Waste concrete may be poured into forms to make riprap or other useful concrete products. Concrete washouts must be located at least 100 feet from drainage ways, inlets and surface waters. The hardened residue from the concrete washout areas will be disposed in the same manner as other non-hazardous construction waste.

5. Solid and Construction Wastes All waste materials will be collected and transported to an appropriate solid waste disposal area.

6. Sanitary Wastes A minimum of one portable sanitary unit will be provided for every ten (10) workers on the site. All sanitary waste materials will be collected from the portable units at least weekly by a licensed portable facility provider in complete compliance with local and state regulations. All sanitary waste units will be located in an area where the likelihood of the unit contributing to stormwater discharges is negligible. If necessary to prevent wastes from contributing to stormwater discharges, additional containment BMPs must be implemented, such as gravel bags or specially designated plastic skid containers around the base.

7. Contaminated Soils Any contaminated soils, either resulting from spills of hazardous substances or discovered during the course of construction, must be contained and cleaned up immediately in accordance with the procedures outlined in the Materials Management Plan and in accordance with applicable state and federal regulations. Contaminated soils not resulting from construction activities, which pre-existed

H - 2 LTPPP Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA construction activities and are discovered by virtue of construction activities, should be reported in the same manner as spills, but with sufficient information to specify that an existing condition discovery is being reported. If there is a release that occurs by virtue of the discovery of existing contamination and it otherwise meets the requirements for a reportable spill, then the release must be reported as a spill.

Spill Prevention Procedures The Contractor will train all personnel in the proper handling and cleanup of spilled hazardous substances or oil. In order to prevent or minimize the potential for a spill of hazardous substances or oil to come into contact with stormwater, the following steps will be implemented. 1. All hazardous substances, such as oil, pesticides, petroleum products, fertilizers, detergents, construction chemicals, will be stored in a secure location. 2. Only the minimum practical quantity of such materials will be kept at the project site. 3. The contractor must have a readily available spill prevention kit and materials on site at all times. The contractor’s onsite spill prevention storage location shall be stocked at all times with a suitable quantity of absorbent and containment materials to address multiple spills in a single day. At a minimum the spill prevention storage location shall include the following materials:  Absorbent pads  Absorbent boom  55-gallon drums with sealable lid  Speedy-dry  Goggles  Plastics or trash containers, etc. 4. Manufacturer’s recommended methods for spill cleanup will be clearly posted, and site personnel will be trained regarding these procedures and the location of the cleanup supplies. 5. It is the contractor’s responsibility to ensure that all hazardous waste discovered or generated at the project site is disposed properly by a licensed hazardous material disposal facility.

Spill Response Procedures In the event of a spill of hazardous substances or oil, the following procedures must be followed: 1. All measures must be taken to contain and abate the spill and to prevent the discharge of the hazardous substance or oil to stormwater, or off-site. The spill area must be kept well ventilated and personnel must wear appropriate protective clothing to prevent injury from contact with the hazardous substances. 2. For spills of less than five (5) gallons of material, proceed with source control and containment, clean-up with absorbent materials or other applicable means unless an imminent hazard or other circumstances dictate that the spill should be treated by a professional emergency response contractor. 3. For spills greater than five (5) gallons of material, immediately contact the MA DEP Hazardous Waste Incident Response Group, and an approved emergency response contractor. Provide information on the type of material spilled, the location of the spill, the quantity spilled, and the

H - 3 LTPPP Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

time of the spill to the emergency response contractor or coordinator, and proceed with prevention, containment and/or clean-up. 4. If there is a Reportable Quantity (RQ) release during the construction period, then the National Response Center will be notified immediately. Within 14 days a report will be submitted to the EPA regional office describing the release, the date and circumstances of the release and the steps taken to prevent another release. This Stormwater Pollution Prevention Plan must be updated to reflect any such steps or actions taken and measures to prevent the same from reoccurring. 5. The contractor’s superintendent will be the spill prevention and response coordinator. He will designate the individuals who will receive spill prevention and response training. These individuals will each become responsible for a particular phase of prevention and response. The names of these personnel will be posted in the material storage area and in the office trailer onsite.

Illicit Discharge Statement-Control of Non-Stormwater Discharges Certain types of discharges are allowable under the U.S. EPA Construction General Permit, and it is the intent of this LTPPP to allow such discharges. These types of discharges will be allowed under the conditions that no pollutants will be allowed to come in contact with that water prior to or after its discharge. The control measures that have been outlined previously in this LTPPP will be followed strictly to ensure that no contamination of these non-stormwater discharges takes place.

H - 4 LTPPP Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

ATTACHMENT I- Operation and Maintenance Plan (O&M Plan)

Pages I-1 - I-2

Stormwater Report I-91/Route 9 & Damon Road Interchange Improvements Northampton, MA

Stormwater Management Operation and Maintenance Plan (O&M Plan)

Description of the Stormwater Management System The stormwater management system for this project collects runoff from the roadways for treatment prior to discharge to water bodies. The system includes the following features: pavement edging, deep sump catch basins, pipes, drop inlets, manholes, paved waterway, flared end sections, and sediment forebays with associated infiltration basins.

During Construction The site contractor, who will be selected by the standard bidding process established by the Massachusetts Department of Transportation (MassDOT), will be responsible for all operation and maintenance (O&M) from the initial ground disturbance through final stabilization and project closeout. Those responsibilities will include: 1. Construct all erosion and sedimentation control measures in accordance with MassDEP Erosion and Sediment Control Guidelines for Urban and Suburban Areas dated May 2003 and the U.S. EPA Developing Your Stormwater Pollution Prevention Plan dated May 2007. 2. Install erosion and sediment control measures prior to any ground disturbance. Continuously maintain the erosion and sediment control measures so that they remain functional until final stabilization is established. 3. Install perimeter erosion and sediment controls, such as compost filter tubes, around all stockpiles. 4. Seed or mulch stockpiles and other disturbed or exposed areas for temporary stabilization, prior to exposure of fourteen days or more. 5. At any portion of the site where construction activities have permanently ceased, or where final grades are reached, implement stabilization practices within three days. 6. Conduct earthwork activity so that runoff is directed away from resources areas. 7. Relocate temporary drainage swales and sediment traps as construction progresses, so that they continue to provide their intended function throughout all phases of construction. 8. Inspect all erosion and sedimentation control measures at least every seven days, and after each rainfall event that exceeds a quarter inch. If the function of any feature is found to be compromised, take action within three days to clean, repair, or replace the compromised erosion and sedimentation control measure. Adhere to the Stormwater Pollution Prevention Plan (SWPPP). 9. Upon completion of all work, inspect all catch basins and remove all accumulated sediment and trash debris. 10. Meet or exceed MassDOT’s specifications. 11. As the project progresses and site drainage conditions change, relocate or augment the erosion and sediment control measures to meet or exceed the minimum measures shown on the highway plans and details.

I - 1 Operation and Maintenance Plan Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA

Post Construction MassDOT will be responsible for post-construction O&M activities, which will be undertaken at a statewide programmatic level under the State’s highway operation and maintenance program. In addition to MassDOT’s standard O&M activities, MassDOT will implement the following stormwater maintenance plan:

Inspections  Check deep sump catch basins, manholes, paved waterways, drop inlets, flared end sections, headwalls, sediment forebays, and overflow spillways for blockage, erosion, and structural deficiency.  Remove trash, debris, and decaying vegetation. Clear blockages.  Repair eroded channels or holes. Add protection, as necessary to prevent further erosion.  Conduct inspections according to the frequencies outlined below.

First Year Post-Construction  Conduct inspections at least once per season.  Re-vegetate poorly established areas as necessary.

After the First Year Post-Construction  Conduct inspections every six months.  Following two years of monitoring that produce no special cleaning or repair, reduce the inspection frequency to annual inspections.  Remove accumulated sediment that exceeds six inches at least annually from all catch basins, drop inlets, paved waterways, sediment forebays, infiltration basins and outlet control structures.  Clear sediment forebays, and infiltration basins of any vegetation or debris that compromises its functional storage volume.  Do not use heavy equipment within the infiltration basins. Heavy equipment must remain on the maintenance shelf.

I - 2 Operation and Maintenance Plan Improvements on I-91 Interchange 19 at Route 9 and Damon Road Northampton, MA