Conservation Commission Meeting Agenda/Materials 109R and 131 Clark Lane Exhibit List (linked)

To: Maureen Fitzgerald, Waterford Conservation Commissioners
From: Sigrun N. Gadwa, Principal, Carya Ecological Services, LLC
Date: February 22, 2023
RE: Waterford Cons. Comm. App # C 22-14, Clark Lane Proposed
Residential Project; additional document for the hearing record
Concerns about the application; their adverse effects on Wetlands;
changes offered by the applicant, or requested of the applicant, to
address the problems.
1. Ditch along western property line will divert ground water to large
detention basin, which will adversely affect hydrology in upland
review area and in the wetlands.
e Flow from this ditch has been redirected to the forest to the
east. Runoff from more rooftops also redirected. The old Clark
Lane pipe will continue to flow easterly. Concern addressed.
2. Excavation of ditch, and the cut along western property line will
damage trees of Clark Lane Neighbors if root loss is over about
40%. Similarly, filling on east side of project will kill or cause
dieback to trees on east side of project, at base of fill slope.
Wetlands will be adversely impacted by loss of the trees’ nutrient
uptake and wildlife support services. The proposed arborvitae
hedge will have little benefit to wetland; it needs
supplementation.
e Compensatory tree planting is being requested as mitigation.
Additional detail can be provided,
3. Concern was that too much water will enter the large detention
basin, coming from runoff from Clark Lane, new roofs and
impervious roadways surfaces, & the new ditch reverting existing
Rie groundwater. The concern was erosion along flow patch during
| —_ C-22-14
| 3 2023 109R & 131 CLARK LANE
| Fierwning e roscessaiceae PUBLIC HEARING 01-26-23
Town of Waterford, CT EXHIBIT #66

periods of high soil saturation, occurring when runoff during very
large storms under saturated conditions would reach the steeper
more erosible slopes. In major storm the protracted flow of a very
large volume would cause shallow swales and gully formation
which would release sediment to the wetlands and carry
pollutants.
e Applicant has proposed to significantly reduce the discharge
volume that could potentially erode the flow path, and to
repair guilies in early stages. If carried out this will be an
effective strategy. A reporting form and a regular schedule for
inspection of the flow path are needed. Criteria need to be
developed in consultation with staff: following what sizes of
storms will inspections take place?.
¢ Concern addressed Note: the details of the configuration and
location of the level spreader of the pipe carrying Clark Lane
runoff also need to be worked out in consultation with staff.
Currently muitiple tree trunks are spreading the runoff but
these lie within the development footprint.
. Bioretentian basin design problems.
They have been corrected with addition of a saturated
denitrifaction component. Concern addressed. Fine particles, with
the highest proportion of toxicants are treated by the bioretention
basin.
. Some fine sediments will not settle out and will be resuspended
due to the detention basin’s rapid drainage time during the larger
storm events. However, In small to moderate events, most small
particles are filtered by the bioretention basin and by buffer soils
along the flow patch when not saturated When water depth is

shallow to start fine particles will be filtered in with, flowing
through a correctly constructed vegetated wetland wth
micropool, mounds, etc.
6. We were concerned that mosquitos will breed in large retention
basin.
e Changes will allow development of a constructed wetland that
support predators controlling mosquitos .
7. It is expensive to change out media of basin. Proposed water
quality monitoring will help ensure this is done in a timely fashion.
Concern addressed.
Note that we had suggested that raingardens would reduce the
crowding, provide green spaces, providing aesthetic function.
Moreover, they will help reduce the size, cost, and frequency of
maintenance of the bioretention basin since they would handle
some of the water. We still think they would improve the project.
8. E. box, spotted, & wood turtles are noted to be possible in the site
by experts SLR, Carya, Theroux. Sigrun Gadwa of Carya has e
observed or received recent reports of these turtles in similar
coastal habitats. The spotted and wood turtles have a key role in
the aquatic food web. E box turtle dispersed wetland wildflower
seeds.
e We request not using heavy machinery that could run over
turtles, unless area has been cleared by a search beforehand.
when grading and using brush hogging and hand-held saws.