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Memo ConCom Comments response 9-26-19T REYNOLDS ENGINEERING | CIVIL ENGINEERS | PLANNING, DESIGN, AND PERMITTING SERVICES 152 MAPLEWOOD TERRACE, FLORENCE, MA 01062 | PHONE: 413-387-8078 | FAX: 413-727-3477 terry@treynoldsengineering.com | www.treynoldsengineering.com To: Northampton, Conservation Commission. From: Terrence Reynolds P.E. Subject: 25 Maple Avenue Date: 9/26/2019 T Reynolds Engineering (TRE) received the following comments on 9/5/19 regarding the Notice of Intent submittal for 25 Maple Avenue. All comments are followed by responses in bold; 1. The flared end outlet structure, including riprap, is proposed to be installed within 1 foot of bank resource. There is sufficient room on the site to pull this outlet away from the resource and create an artificial wetland in lieu of riprap, which would improve existing conditions. This could be eligible for TSS removal or other credit as a BMP. The subsurface system outfall is too low to allow it to be above the bank. The outfall has been designed with a flared end section and energy dissipater extending to the tow of slope to prevent any scouring of the slope. 2. Columbia Gas had sought an AUL on this property due to past industrial uses, is an AUL in-place? Subsurface contamination could potentially affect the proposed subsurface stormwater system. The applicant is in discussion with Columbia gas regarding an AUL for the property. Test pits have been dug in the area of the sub-surface system. The design depth of the system is well above the bottom of the test pit. No contaminination was encountered in the test pit. 3. Please note DEP's comment that the system will be subject to UIC requirements. Noted 4. The application indicates that site conditions will be "improved through site grading to improve infiltration and the restoration of degraded areas with the addition of top soil and appropriate surface plantings' but no details on this work are included in the application. Please provide a detailed grading and planting plan. Not enough information has been provided to be able to confirm an improvement over existing conditions. The Planting plan has been revised to show additional detail of degraded area improvements. 5. All non-native fill will need to be removed from the area of the subsurface system. No fill is anticipated to be encounterred in the area of the sub-surface system based on test pit observations. 6. Have plantings required pursuant to the significant tree ordinance been included in plans? Yes 7. Please provide an assessment of compliance with Section 337-10(e)(2)(h) of the Northampton Wetlands Ordinance. The plans have been designed to be in compliance with the Northampton Wetlands Ordinance. T REYNOLDS ENGINEERING | CIVIL ENGINEERS | PLANNING, DESIGN, AND PERMITTING SERVICES 152 MAPLEWOOD TERRACET, WHATELY, MA 01373 |PHONE:413-387-8078 | FAX:413-772-3477 terry@treynoldsengineering.com |www.treynoldsengineering.com DEP Comments; [1] The commission first needs to review the Riverfront area on site as well as the submitted plans to understand what is the degraded area that existed in 1996 and exists now, per the definition of degraded per 310 CMR 10.58 (5). Noted. The Commission Agent has reviewed the sight and numerous test pits have been performed to confirm the degraded nature of the site. [2] An improvement over existing conditions is always required for work submitted under 310 CMR 10.58(5). Acceptable improvements include, but are not limited to: 1) Significant net reduction of impervious surfaces; Degraded areas have been reduced 2) Planting of indigenous plant species; Indigenous plants have been proposed throughout the site. 3) Providing stormwater management demonstrably in excess of what is required per 310 CMR 10.05(6)(k) through (q); All stormwater management standards have been met or exceeded. 4) Removal and proper disposal of noxious but otherwise legally located materials. discarded constructiion materials will be removed from the site. [3] Table 1.0 states that all proposed disturbance will be closer than the existing degraded area but on page 5 of 6 it states that no work is closer than the existing degraded area. This should be clarified. If any work is closer than the existing degraded area, then either 1 to 1 restoration and/or 2 to 1 mitigation is required. This was a typo and has been corrected to state no work closer the existing degraded areas. [4] One cannot use streamstats to overcome the perennial presumption of a stream. Please review 310 CMR 10.58(2)(a)1.d. Noted. [5] Please note that the Stormwater Management Standards only apply to the maximum extent practicable. Noted. [6] Underground stormwater chambers are subject to UIC program requirements. https://www.mass.gov/underground-injection-control-uic Noted.