ATTACHMENT 5
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.