HomeMy WebLinkAboutSP-22-013 - Supplemental - 0000 Stonehedge Drive
Memo
To: South Burlington Development Review Board
From: Christine Gingras, Public Works Project Manager
CC: Marla Keene, Development Review Planner
Date: March 8, 2022
Re: Stonehedge South Area Association Site Plan Application
Stonehedge South Area Association proposes to redevelop a 321 LF stormwater swale to connect
stormwater infrastructure in the neighborhood with a stormwater pond in Szymanski Park. When the
adjacent condominiums were originally constructed, a drainage swale was installed between the K and
L clusters. Since then, sediment deposition and growth of a thick root mat of giant reed have clogged
the historic channel. Flow out of the neighborhood is currently impeded, resulting in flooding and safety
(ice related) issues for residents in the L cluster. The City is proposing to restore positive drainage within
the swale by performing maintenance to clear out accumulated material. As vegetation has grown up
within this swale area, the City is proposing to rework the swale around mature trees. The proposed
work would allow the swale to drain 6.9 acres of impervious surface from a total 34.9 acre drainage
area located to the north of the proposed swale. Straddling two parcels, 78% of the project is on
Stonehedge South Area Association property. The other 22% of the project is on the Szymanski Park
parcel, owned by the City of South Burlington.
The proposed project would have no impact on current uses, buildings, or impervious areas.
Construction activities (project wide) will have the following impacts on class II wetlands: 8,115 SF of
permanent ("other," non-fill) impact to wetland, 4968 SF of temporary impact to wetland, 440 SF of
permanent impact to buffer (excavation/non-fill) and 1453 SF of temporary impact to buffer.
On the Stonehedge parcel, the proposed project will permanently impact 6,330 SF of existing class II
wetland and 343 SF of associated buffer. Construction will include excavation of the ditch in wetland, a
temporary construction stabilization pad in the buffer, and tracked equipment access from Stonehedge
Drive and turn-around space in the wetland and buffer. Required excavation and removal of
approximately 253 yards of fill on the Stonehedge parcel is estimated. This material will be hauled
offsite. Impacts to wetland and buffer are required in order to restore the historic flow pattern, allowing
stormwater from the culverts outleting on the south side of Stonehedge Drive to drain to the stormwater
treatment pond below.
Avoidance of wetland impact to construct the swale is not feasible, since the problem is localized to the
area between the culvert outlets and stormwater pond below. Alignment of the proposed swale was set
to limit impact on existing trees and plants to the greatest extent possible. As avoidance could not be
achieved for the project, the minimization criteria was utilized instead. The proposed swale is the
minimum size necessary to restore positive drainage, with an average cross-sectional depth of 1 foot.
This will enable positive drainage without having a major impact on the subsurface hydrology of the site.
The hydrology of the wetland is primarily associated with landscape-scale groundwater discharge from
the hill above.
Restoration of the wetland will be accomplished by the planting of a wetland seed mix over the disturbed
area, and the swale is expected to return to a functioning wetland as vegetation establishes. The State
of Vermont Department of Environmental Conservation and Army Core of Engineers have both issued
permits for this project.
We are submitting this project to the South Burlington DRB for review as a site plan application due to
the proposed class II wetland impacts and the amount of fill that will be removed and relocated on site.
Included with this application, please find final project plans, a copy of the ACOE wetland permit, VT
ANR wetland permit, 1983 Site and Utilities Plan for Stonehedge Condos Cluster L, 2018 Record
Drawings for the stormwater treatment pond in Szymanski Park, and Stonehedge abutters list. If you
have any questions, please contact me at (802) 658–7961 x6111 or cgingras@southburlingtonvt.gov.