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HomeMy WebLinkAbout24IWC11-375 Maple Ave-Engineering Review comments 1 1-2-2025 John U. Faulise, Jr., L.S. David C. McKay, P.E. Gerald J. Stefon, L.S. (1952-2021) Jacob S. Faulise, E.I.T. Boundaries LLC 179 Pachaug River Drive P.O. Box 184 Griswold, CT 06351 T 860.376.2006 | F 860.376.5899 www.boundariesllc.net January 2, 2025 Ms. Stacy Radford Zoning & Wetland Officer Department of Land Use & Development Town of Montville 310 Norwich-New London Turnpike Uncasville, CT 06382 Re: 24IWC11 – 349 Maple Ave. LLC 375 Maple Ave. and Route 163 Montville, CT Site Improvement Plan and Stormwater Management Report Review Dear Ms. Radford, Per your request Boundaries, LLC. has completed a review of the site improvement plans and stormwater management report for the proposed trailer storage facility located at 375 Maple Avenue and Route 163 (Map 031 Lot 015-000 and Map 031 Lot 019-000) prepared by CLA Engineers, Inc. This review is intended to evaluate compliance of the plan with the requirements of the Town of Montville Inland Wetlands and Watercourses Regulations. The following documents were received as part of the application package: · Inland Wetlands Application and Abutters Lists. · Project Narrative Letter. · Stormwater Management Plan. · Wetland Delineation Report. · Site Improvement Plan, 375 Maple Avenue/Route 163, Town of Montville, Connecticut 06382, Prepared for 349 Maple Ave. LLC, 410 Maple Avenue, Montville, Connecticut 06382, December 16, 2024. The following comments or questions are based on the above documents: General · Please submit the CT DEEP Statewide Inland Wetlands & Watercourses Activity Reporting Form. Page 2 Stormwater Modeling · The stormwater model does not appear to account for the HSG D soils indicated on the soils map. Please update accordingly. · Please evaluate if Fair Condition Open Space is the correct CN value to use under existing conditions. The majority of the property appears to be densely vegetated and may qualify as having “good” ground coverage. · The CN value used in Watershed 2b may be adjusted per page 58 of the Stormwater Quality Manual to account for the Qualifying Pervious Area downgradient of the access driveway. This may reduce the peak runoff rates in this area. Please update accordingly. · Please confirm that the storm distribution curve used for the stormwater modeling is the NOAA Type D storm event. The storm distribution curve is available under the Chapter 5 section of the following website: https://dep.nj.gov/stormwater/bmp-manual/ · Peak runoff attenuation may be waived when the stormwater discharge is directly to a fourth order river and the development area is less than 5% of the watershed upstream of the development site per page 58 of the Stormwater Quality Manual. Please demonstrate that Oxoboxo Brook is a fourth order stream so the peak runoff attenuation requirement may be waived as requested. · As noted in the Stormwater Management Plan, the proposed bottoms of the Stormwater Basins do not meet the recommended minimum separation to seasonal high groundwater. This will likely lead to the basins not providing the storage volume anticipated during periods of seasonal high groundwater resulting in higher-than-expected peak runoff rates. Please evaluate the peak runoff rates assuming the basin does not drain between storm events and certify that the peak runoff rates will not negatively impact downstream properties or wetland resources and that the stormwater standards are met to the maximum extent achievable. · Please evaluate the 100-year discharge velocities to ensure that the appropriately sized riprap is specified, especially for the 30-inch drainage discharge. 30-inch Drain Relocation · Please provide the inlet invert elevation for the proposed catch basin. · Please ensure that the proposed reduction in slope to the drain do not reduce its capacity from existing conditions and that the Public Works Department finds the flat section of pipe acceptable from a maintenance perspective. · Please provide details for the proposed spread apron including riprap sizing and overall dimensions of apron. · Please incorporate deep sumps and hoods on the proposed drainage structures to provide some treatment of stormwater prior to discharge. Site Plans · Please update the Proposed Development notes on Sheet 4 to include the proposed area of disturbance, correct reference to flood hazard areas on the property, and correct reference to disturbance of inland wetlands on the property. · Please review the proposed grading of the Qualifying Pervious Area to ensure that no fill is placed within the 100-year flood plain or compensatory storage is provided elsewhere. Page 3 · Please evaluate the velocity and freeboard in the perimeter swales to confirm that the correct erosion control blanket is specified. Please specify an erosion control blanket and add the detail referenced in the Grassed Swale Detail. · Please update the Stormwater Manhole Detail to be 5 feet in diameter as called for on the site plans. · Please update the Trench Detail: Drainage Culvert to match the Town of Montville Road Standards. Water Quality Basins · Please review proposed grading of the sediment forebays and gabion spillways. The stone fill of the gabion will provide limited filtration of the incoming stormwater. The sediment forebay will be more effective if the stored volume is provided below the bottom of the stone gabion in a permanent wet pool. · The proposed gabions match the top of basin elevation. Please lower the top of the gabions to provide 1-foot of freeboard from the top of basin. · Please specify the intended stone for the gabion baskets. · Overflow spillways are recommended to have a minimum width of 8 feet per page 485 of the Stormwater Quality Manual. The proposed stormwater basin outlets are called out as 4 feet wide. Please provide justification for not conforming to the Stormwater Quality Manual recommendations. Erosion and Sedimentation Control · Please incorporate a double row of sediment barrier where construction activity is located within 50-feet of the limit of inland wetlands per Section 5(b)(2)(A)(ii) of the DEEP Construction General Permit. · Please evaluate if the proposed silt fence should be replaced with a check dam immediately downgradient of the proposed sediment trap discharges. · Please update the elevations called for on the temporary sediment trap sediment marker stakes on Sheet 6. · Please coordinate the areas called for in the Sediment Trap Sizing Table and the Legend on Sheet 6. Please do not hesitate to contact me with any questions. Sincerely, David C. McKay, P.E.