HomeMy WebLinkAboutSP-24-08 - Supplemental - 0870 Williston Road (29)The Stormwater Section has reviewed the DoubleTree Hotel Addition site plan application prepared by
Krebs & Lansing Consulting Engineers. We would like to offer the following comments:
1. This project is located within the Centennial Brook watershed.
2. This project is one of three being completed on the same parcel. Across the three projects, 1.82
acres of new impervious are proposed, 5.59 acres of impervious are proposed to be
redeveloped, and there is 3.76 acres of existing impervious. The project site is designated as a 3-
acre site as well.
3. There are several existing ponds that currently treat impervious onsite. The existing stormwater
practices do not meet standards set by the 2017 VSMM.
4. The project proposes to expand existing impervious area onsite by greater than 5,000 sf and
disturb greater than 1 acre of land. It will therefore require a stormwater permit and
construction permit from the Vermont DEC Stormwater Division. The applicant should acquire
these permits before starting construction.
5. As the project proposes to expand existing impervious area by greater than 5,000 sf, as well as
containing greater than one-half acre of impervious area, the project is subject to the
requirements of section 13.05 of the LDRs.
6. The submitted HydroCAD does not include nodes to model the existing stormwater treatment
practices onsite. As such, it cannot be determined how the proposed conditions compare to
existing conditions onsite, particularly in the 1-yr and 25-yr storm events as described in section
13.05 of the LDRs.
7. In the submitted HydroCAD, the infiltration chambers are shown separate from the rest of the
conveyance system that drains to Gravel Wetland #1, however the plans show that the outlet
structure of the infiltration chambers connect to stormwater conveyance that discharges to
Gravel Wetland #1. Please revise.
8. The area highlighted below does not appear to be in the HydroCAD model. Based on the
configuration of the conveyance system, this will drain to Gravel Wetland #1. Please add a node
to include this area.
9. The area highlighted below is not accounted for in the HydroCAD model and does not flow to
the proposed treatment practices. Based on the existing conveyance system, this area flows to
the retention basin located on the adjacent UVM property. Does this treatment practice have
the capacity to treated new and redeveloped impervious area? Also, does this practice meet
standards set by the VSMM and described in the LDRs?
10. There are several trees proposed over stormwater pipes. These will present issues in the future
when the roots grow and will cause issues with future maintenance of these pipes. The southern
most of the highlighted trees is also proposed within 1 ft of a catch basin cover, which will cause
impacts. Please revise.
11. Is the below tree existing? Woody vegetation is not allowed within the footprint of a gravel
wetland.
Thank you for the opportunity to review.