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HomeMy WebLinkAboutPWGC Response Letter_2024-07 Page 1 July 22, 2024 Re: NY Groton I (South Main Street), LLC and NY Groton II (South Main Street), LLC Commercial Solar Projects Response to Tim Buhl’s Comments, 07-01-2024 Dear Mr. Buhl, P.W. Grosser Consulting (PWGC), as the project engineer and environmental consultant to NY Groton I (South Main Street), LLC and NY Groton II (South Main Street), LLC, is in receipt of the comments provided by Tim Buhl on July 1, 2024. This letter has been prepared to respond to such comments, and modified plans and documentation are enclosed and/or attached, as noted below. Tim Buhl Comments dated 07-01-2024 1. Comment: We now have 2’ contours for both sites, the problem is the existing contours are not labeled on the South site, and only limited existing data is labeled on the North site. As much as 10' cuts and fills are still shown, meaning significant earthwork will need to be done. Without the original topo labeled in all disturbed areas for each site, reviews and cut and fill estimates are very difficult. Ten-foot intervals would be helpful in this regard. More sections/profiles through the array areas should be also done, to confirm slopes and any revised grades and some of the more critical areas. There are several large gaps in stee per sections of the arrays, bedrock depth could also be a factor in array supports, especially in cut areas. PWGC Response: North Parcel: More existing contour labels have been added to the grading plan, along with more profiles (see sheets C-200, C-600 and C-601). A general cut/fill analysis has been provided on sheet C -001, as well as a detailed cut/fill analysis on sheet C-200. A note regarding the max cut and depth to bedrock has been provided on sheet C-200. South Parcel: More existing contour labels have been added to the grading plan, along with an additional profile (see sheets C-200 and C-600). A general cut/fill analysis has been provided on sheet C -001. A note regarding the max cut and depth to bedrock has been provided on sheet C-200. 2. Comment: Soil types and classifications should be done in the array disturbance areas separately, so that impacts are not skewed by the remaining undisturbed soils and lands in agriculture. PWGC Response: North Parcel: The USDA soil classifications have been shown on the existing conditions plan (sheet C-100). South Parcel: The USDA soil classifications have been shown on the existing conditions plan (sheet C-100). 3. Comment: Silt fences are shown outside the disturbed areas, when they should be shown inside, as the fences must be buried into the ground, & trees, brush removed to do so. Page 2 PWGC Response: North Parcel: Silt fences have been moved inside the area of disturbance, see sheet C-201. South Parcel: Silt fences have been moved inside the area of disturbance, see sheet C-201. 4. Comment: Stockpile areas are shown as small green dots on each site. Judging from the amount of cuts and fills being required and the amount of topsoil to be stored, the areas shown are grossly inadequate, as is the detail shown. It is not known if the cuts and fills will be balanced with no offsite disposal or importing required. PWGC Response: North Parcel: A cut/fill analysis has been shown on sheets C-001 and C-200. Proposed stockpile locations are shown on a conceptual level for reference as the contractor may or may not stockpile soils depending on means and methods of grading at the time of construction. South Parcel: A cut/fill analysis has been shown on sheet C-001. Proposed stockpile locations are shown on a conceptual level for reference as the contractor may or may not stockpile soils depending on means and methods of grading at the time of construction. 5. Comment: Scale bars should be shown on all site drawings for both sites to facilitate site reviews and grade slopes when zoomed in. PWGC Response: North Parcel: Scale bars have been provided on each sheet. South Parcel: Scale bars have been provided on each sheet. 6. Comment: The laydown/staging area on the north site is not shown part of the disturbed area – will the ground be temporarily modified for this use (topsoil stripped, gravel base installed)? It is included as a disturbance area on the south site and silt fence around the perimeter, but it is located on a 14% grade. Will the area be regraded? PWGC Response: North Parcel: The staging area has been moved to an area that will be graded and no site preparation for the laydown area is proposed. Refer to grading notes on sheet C-001 for topsoil stripping. South Parcel: The staging area will be located on existing grade, where the existing slope is roughly 6.6%. 7. Comment: The permanent gravel access roads at both sites will have uncontrolled peak runoff increases and the potential for long term water quality issues to nearby drainage ditches and streams during & after project construction. There are no runoff retention on treatment practices shown in these critical areas where the driveways are steep (25%- 35% on the north site and 15% - 55% on the south.) Page 3 PWGC Response: North Parcel: The access road is proposed as a permeable access road, and a drainage swale has been added to the Gravel Access Road Detail, see sheet C-601. The access road has also been regraded to be less than 15%. South Parcel: The access road is proposed as a permeable access road, and a drainage swale has been added to the Gravel Access Road Detail, see sheet C -601. A rain garden has also been added north of the stream to collect runoff from the access road. 8. Comment: An updated SWPPP document has been provided. Due to the changes from tracking arrays to fixed arrays, there will be changes in runoff amounts and concentrations, so an updated SWPPP was needed. Waterbars and rain gardens are now fully shown and appear to be adequate based on a 1” rainfall, which is less than a 5 - year interval storm. It is unclear as to where the discharges from the rain gardens will be directed, and what the impacts of lager storm events (5, 10 and 100-year events) will be. To be fair, I have not had sufficient time to fully evaluate the full SWPPP Hydro Cad model that was done, and we may run one of our own to verify events scenarios with the now fixed-panel arrays if the Town of Groton thinks it will be helpful. PWGC Response: North Parcel: PWGC has provided the HydroCAD model used for the site. The rain gardens have been sized to accommodate the Water Quality Volume and Runoff Reduction Volume. Based on the HydroCAD Model, the proposed development reduces peak flows for the 10 and 100-year storm events and does not increase the runoff volume, therefore the Overbank and Extreme Flood Control criteria are reduced from the pre - development conditions. South Parcel: PWGC has provided the HydroCAD model used for the site. The rain gardens have been sized to accommodate the Water Quality Volume and Runoff Reduction Volume. Based on the HydroCAD Model, the proposed development reduces peak flows for the 10 and 100-year storm events and does not increase the runoff volume, therefore the Overbank and Extreme Flood Control criteria are reduced from the pre - development conditions. Thank you. Sincerely, P.W. Grosser Consulting Michael Scanlon, P.E. Enc. (6) 1. NY Groton I (South Main Street), LLC Site Plan 2. NY Groton II (South Main Street), LLC Site Plan 5. NY Groton I (South Main Street), LLC Full Environmental Assessment Form Part 1 6. NY Groton II (South Main Street), LLC Full Environmental Assessment Form Part 1