Date: January 21, 2008
From: Sunrise Coalition
Submitted by: Doug Schworer
Subject: Bradley Green Public Hearing Agenda 3, January 23, 2008
We thank the staff for a very
useful meeting (January 3, 2008) to clarify the issues we have raised on
stormwater. The substance of that discussion addressed the nature of the
eastern portion of the property around the Potted Plant and extending downslope
towards I-40, where the drainage line had previously been determined to be
intermittent by Fred Royal, then subsequently reclassified as not intermittent.
We contribute the following comments on the Stormwater Management section of
Roger Stancil’s Memorandum (Agenda Item Public Hearing: Bradley Ridge
Application for Preliminary Plat Cluster Subdivision (File No. 9880-96-7441)
dated January 23, 2008 regarding this meeting as reported by staff:
- We wish to clarify that WE
OBSERVED ACTIVELY flowing water (NOT "STANDING WATER" AS
INDICATED IN THE STAFF MEMO) ALONG THE ENTIRE LENGTH OF THE SMALL STREAM
AND WETLANDS ON THE EASTERN PORTION OF THE PROPERTY DURING AND AFTER THE
RAIN EVENT ON DECEMBER 30, 2007. FLOWING WATER IS A STRONG
INDICATOR OF hydrologic CONNECTION TO THE PERENNIAL STREAM THAT FLOWS
UNDER I-40, rather than simply OF residual "wet areas" or
"standing water." The flowing water continues through the
northern boundary of the property and ENTERS AN area where a previous road
or farm pond existed, and in the constructed side slope to
I-40. This is a wet, boggy area with high groundwater
tables that is immediately adjacent to and drains into the perennial
stream. THE AREA CONTAINS EVIDENCE OF SURFACE FLOW, SPECIFICALLY
SMALL CHANNELS THAT CONNECT DIRECTLY WITH THE PERRENIAL STREAM.
While the secondary determination that this was not an intermittent stream
was based on UNSPECIFIED CRITERIA OF connectivity, OUR OBSERVATIONS
OF direct connection OF THE INTERMITTENT CHANNEL INTO the wet area
IMMEDIATELY adjacent to the perennial stream INDICATES THAT THE
CLASSIFICATION OF THE INTERMITTENT CHANNEL SHOULD BE
REVISITED. Specifically, a determination SHOULD BE MADE
of whether the channel, twice scored above the threshold for an
intermittent channel, is connected through a wetland to the perennial
stream. We note that the only parcels that may be in question until this
determination can be made are #11, 12, 13 and potentially 14.
- We noted that the current
drainage line serves as a stormwater control. If it is currently
“disconnected” from the perennial stream, then the current volume and peak
runoff is minimized. The method presented of computing pre-development
runoff conditions using the Rational Runoff approach assumes a connected
drainage line, which overestimates the runoff relative to the current
condition. This may require a re-evaluation of the amount of
post-development runoff production as required by LUMO.
- We asked for clarification of
the locations of the soil borings relative to the location of the proposed
stormwater facility (stormwater pond #1). These borings were arranged
following the road system of a previous (not the current) design. The
locations of the soil boring approximated by engineering staff and Warren
Mitchell on the current design map during the meeting. We understand that
these will be combined on the same map for more detailed evaluation, but
note that borings 6 and 7 are above the stormwater facility, while boring
5 is on the same elevation contour (although it is closer to the perennial
stream). The soil boring report specifically noted that seasonal
groundwater tables in the area may fluctuate significantly from the
conditions at the time of the borings, which appear to have been made
during the summer of 2004, which was likely at a time of lower groundwater
levels.
- We are concerned that
information on the environmental status of the land previously developed
and used by Habitat is not available. Specifically, a previous determination
of more extensive wetlands were used as an overlay for the planning
charette held at Carol Woods. We have asked for this material to be made
available, as well as any background investigations used for its
production. We understand these determinations may not be relevant as
Army Corps is the regulatory agency. However, the material used to
generate those maps is relevant. HHOC officials deny the existence of
these maps and preceding material, and they, the town and HHOC’s
architectural consultants who used this material to produce alternative
designs for the charette state that they did not keep any of the
information and have no knowledge of a study. However, in our discussion
at the meeting with town staff, Warren Mitchell stated that the consultant
that produced these maps was in the field with him and Army Corps staff
for the USACE site determination. We are concerned that potentially
important information is lost or is being withheld.
- Both HHOC consultants and town
staff indicated at the meeting that the source of any standing water and
the wetland (non-regulatory) at the origin of the drainage line were due
to drainage water from Potted Plant irrigation. We do not agree with
this, but if this is the case, nursery potting operations use substantial
amounts of fertilizer and pesticides. The area of the upper wetland and
any area receiving substantial drainage from the former nursery should be
tested for contamination before houses and recreational areas are
developed.
We understand
that the stormwater proposal is preliminary and that the nature of the BMPs has
yet to be determined (e.g. infiltration basin, bioretention pond, wet detention
pond) and its location has been drawn in as a placeholder. On the development
of the next phase of evaluation, we request that borings should be done in the
specific locations of the proposed stormwater controls and that the nature of
the connection of the drainage line and the pre and post-development runoff
estimates be considered. We suggest that action can be taken on parcels not
subject to these determinations, but that action on parcels 11, 12, 13, 14
should be postponed until these issues are resolved.