HomeMy WebLinkAboutIWA TOSW Rye St culvert removal rvu 12-3-2023M E M O R A N D U M
To: South Windsor Inland Wetland/Conservation Commission.
From: Jeffrey H. Folger – Environmental Planner
Date: December 14, 2023
Re: Appl#23-51W Review of the proposed Town of South Windsor Rye St culvert removal site plan, Plans dated 12-2023.
The project is to remove existing, twin, 48” culverts that were a part of the historic location of Rye St. Disturbance within the Upland Review Area (URA) is estimated at 35,000 sqft.
Total temporary, direct, impact is estimated at 1496 sqft of which, 150 linear feet of watercourse alteration is included. Streambed restoration associated with the removal of the
culverts, equals 375 linear feet.
Site: The site is located in the Dry Brook watershed, which drains to the Scantic River. The parcel contains the Rye St Sanitary Sewer pump station as well. The specific site is the
old road right-of-way that extends Rye St to Troy Rd.
The remnant roadway consists of an approximate 300’ long berm, oriented northwest to southeast, with two culverts at the location of the Dry Brook channel. The berm is located approximately
125 feet east of the current Rye St culvert. The concrete headwalls on the west side of the berm have collapsed into the stream channel and erosion of the earthen portion of the berm
is evident, causing sediment to enter the watercourse. Complete failure of the berm would result in damage to the current Rye St crossing. The project proposes to remove the culverts
and approximately 20 feet of the berm to provide a stable passage for the watercourse.
Regulated areas on the site consist of the watercourse channel, and very localized wetland soils adjacent to the channel. The watercourse channel at this point is approximately two
to three feet wide, with an average depth of 6 inches to a foot. The channel substrate consists of old rip-rap imbedded with fine sands.
The main functions of the watercourse would be conveyance, and groundwater surcharge, with limited wildlife habitat (herps, and invertebrates). The locations of the intersecting roads
limit the use by terrestrial wildlife. Finfish and shellfish habitat would be limited due to the size and location of the channel.
Impacts:
The soils present on the site are mapped Rippowam Fine Sandy Loam 0-3% slopes. This soil is poorly drained and common to flood plains. Erosion potential for activities on the site
is expected to be low. Stone coffer dams are proposed to sequester areas where work will be done within the channel. Perimeter reinforced silt fencing, and follow-up slope stabilization
will include rip-rap and grass seeding. Post construction, the stone coffer dams are proposed to be pushed into the hyper excavated channel areas where the natural migration of fines
will fill in the voids in the stone and eventually reach an equilibrium.
Stormwater:
There are presently two leak-offs where runoff enters the watercourse just east of the current Rye St culvert. The leak-offs run down eroded channels from the roadway to the watercourse.
The proposed plan seeks to pipe that runoff to rip-rap plunge pools prior to the watercourse to eliminate erosive cutting adjacent to the brook.
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