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HomeMy WebLinkAbout26IWC4 - Butlertown Rd - Narrative March 9, 2026 Douglas K. Brush, Chair Inland Wetlands Commission Town of Montville 310 Norwich-New London Turnpike Uncasville, CT 06382 Re: Town of Montville Butlertown Road Improvement Project Oakdale, CT 06370 CLA-7928 Dear Ms. Radford On behalf of the Town of Montville Department of Public Works, CLA Engineers has prepared this Inlands Wetlands Application for the Butlertown Road Improvement Project. The project involves rehabilitation of a portion of Butlertown Road from the Waterford town line in a northerly direction approximately 2,000 feet. This section of Butlertown Road lies within residential (R-60), light industrial (LI), and industrial (I District) zoning districts and consists of single-family homes, industrial buildings, parking and staging areas. The roadway is in poor structural condition and very narrow in sections. Flat grades cause poor drainage and localized ponding. The project will utilize full-depth reclamation of the existing asphalt roadway with localized widening to achieve a standard 22-feet cross section. The longitudinal profile will be improved and cross slopes formalized and driveway aprons will be restored and shoulders re-graded to promote positive drainage from the roadway. At the northern limits of the project, a small portion of the improvements (2,100 s.f.) lie within the 50-foot upland review area of an inland wetland. This wetland has been delineated by CLA Engineers, and a functional evaluation of the wetland and assessment of potential impacts has been performed and is included with this submission. Stormwater Management The portion of Butlertown Road to be reconstructed has no drainage system. At the northern limit of the project, an unnamed watercourse crosses beneath the road, via a 42 reinforced concrete pipe, and eventually drains to Latimer Brook. The stream is located at a low point in the road profile and receives roadway run-off from the south and approximately 100-feet to the north. Run-off CLA Engineers, Inc. Civil Structural Survey 317 MAIN STREET NORWICH, CT 06360 (860) 886-1966 (860) 886-9165 FAX from the roadway drains to the low point, leaves the roadway, flows down the embankment and enters to the watercourse on both sides of the road. Over time, this will lead to erosion of the embankment and undermine the guardrail posts that currently protect traffic from the steep slope. The project proposes no change to the drainage regime but seeks to add stormwater capacity and quality by the following methods. First, the project proposes installing a bituminous berm that will contain and channel the run-off to the low point where two catch basins will be installed to collect the run-off and prevent the flow of stormwater over the embankment. The downstream catch basin will comprise a Contech Cascade Separator (hydrodynamic separator) to trap sediment and hydrocarbons that ordinarily would have entered the watercourse. Peak flow rates from design storm events of various frequencies were determined by the Rational Method and the Soil Conservation Service (see below and appended analysis). Peak Flow Rates from Design Storm Events (CFS) Analysis Method WQF Event (1.3”) 1-Year Event (2.89”) 2-Year Event (3.45”) 10-Year Event (5.12”) 25-Year Event (6.16”) 100-Year Event (7.76”) Rational Method 1.1 1.1 1.3 2.0 2.4 3.0 SCS Method 0.4 0.9 1.0 1.6 1.9 2.4 Connecticut DEEP water quality standards require capture and treatment of runoff from frequent, small storm events; typically the 90th percentile storm or 1.3” of rain. The volume is referred to as the Water Quality Volume (WQV) and the equivalent flow rate is referred to as the Water Quality Flow (WQF). The WQF associated with the area of roadway contributing to the hydrodynamic separator is shown in bold in above table. The treatment rate for the Cascade model (CS-4) proposed for the project is 1.2 CFS with a peak conveyance rate of 2.5 CFS. This demonstrates that treatment standards will be exceeded (up to the 2-year storm event) and that the hydraulic capacity of the separator can convey flow associated with the 25-year storm event. Secondly, where shoulder grading allows, vegetated swales (3 feet wide by 1 foot deep) will be installed to receive run-off from the roadway. The intent of the swales is to capture and infiltrate run-off from smaller storm events, that ordinarily, would run-off onto adjacent property or been conveyed towards the watercourse. In general, construction stormwater and erosion and sedimentation measures throughout the work area will be managed by implementing erosion control devices including inlet sedimentation controls at new catch basin locations and silt fence and haybales provided and maintained downgradient of disturbed soils to delineate the limits of construction and protect the surrounding area from sedimentation. Provisions for seeding and site stabilization after construction are also included in the plans. In summary, the project will require work to be performed within the upland review area of the wetland. This work will be occurring above and upslope of the regulated watercourse. The project is expected to be implemented during the summer of 2026 and would take approximately 4-6 weeks to complete. This project will require the use of traditional construction machinery including an excavator, a full depth pavement reclamation machine, road paver, rollers and haulage trucks. Within the 50-foot upland review area, the existing bituminous asphalt will be reclaimed as the base material for new asphalt pavement, adding approximately 180 square feet of new pavement. This, along with other work in the upland review area, will account for approximately 2,100 square feet of disturbance. No direct impact to the wetland or the watercourse is proposed. Please feel free to call me at our office or email me at dhayward@claengineers.com with any questions or comments. Very truly yours, CLA Engineers, Inc. Darren Hayward, P.E.