NC0089702_Fact Sheet_20181108

DENR / DWR / NPDES
FACT SHEET ADDENDUM
NPDES Permit NC0089702
Facility Information
Applicant/Facility Name
Terwilliger Pappas Multi -Family Partners -
Solis Brightleaf Apartments - Brownfields
Groundwater Remediation (GW-REM)
Applicant Address
510 Glenwood Avenue, Suite 317, Raleigh 27603
Facility Address
1001 West Main Street, Durham 27701
Permitted Flow (MGD)
0.00005
Type of Waste
Treated excavation groundwater and permanent facility dewatering
Facility Class
Physical/Chemical
County
Durham
Date:
08Nov2018
Permit Writer:
Joe R. Corporon, P.G.
Facility Status
New
Regional Office
RRO
Stream Characteristics
Receiving Stream
UT to Ellerbe Creek
Stream
Classification
WS-V; NSW
Stream Segment
27-5-(03)
Drainage basin
Neuse River Basin
Summer 7Q10 (cfs)
0.0
Subbasin
03-04-01
Winter 7Q10 (cfs)
0.0
Use Supporting
Yes
30Q2 (cfs)
0.0
303(d) Listed
NSW
Average Flow (cfs)
0.0
State Grid
D23NW
IWC (%)
100 %
[storm -sewer discharge]
USGS Topo Quad
Southwest Durham, NC
Project Summary - The Applicant proposes [via consultant Mid -Atlantic Engineering and
Environmental Solutions] to develop several contiguous real estate parcels into a 1.45-acre
apartment complex with subterranean parking. Excavation and permanent dewatering proposes to
discharge to a City od Durham stormsewer under zero -flow receiving -stream conditions
(7Q10/30Q2 = 0.0 cfs). The Division concurs that this discharge alternative is the most viable
based on feasibility and cost, as outlined in the Engineers Alternatives Analysis (EAA) included
with the application.
The Applicant installed a French -drain dewatering system to service the entire site. This gravity
drain is an unlined gravel trench to a depth of 2 feet, fitted at its bottom with a perforated 2-inch-
diameter PVC drainpipe [see application, Figure C5.10]. Because this trench and pipe are designed
open to the environment, it gathers groundwater, but to a depth of two -feet only.
Initial excavation discharges were temporarily allowed via a pump -and -haul permit through the
City of Durham. However, sampling and analysis of these discharges suggested the presents of
oxygen -consuming wastes not permittable to surface waters. These data prompted the installation
of the facilities permanent dewatering facilities and a test period to evaluate compliance of this
new system. This test period advanced through July, August, and September 2018.
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Permanent Dewater Facilities — Plans for the structure's subterranean parking required the
design and installation of a permanent dewater system. This system post-dates the draft permit and
has been included on the issuance Supplement to Permit Cover Sheet. At the Permittee's request,
flow from this system is increased from 0.0005 MGD to 0.0015 MGD.
Analytical results for three (3) sample events during this three-month test period included all
parameters of concern (POCs) supplemented by three (3) monthly Whole Effluent Toxicity (WET)
tests. WET tests indicate "pass," and analytical results suggest no POC above compliance levels;
These results serve to contribute data necessary to establish a minimum of 12 sample results
toward eligibility for permit modification [per section A. (1.), Footnote 3]. Per John Hennessy, the
Permittee is instructed to submit all eligible POCs collectively, so they may be considered at once
— not in multiple requests for modification.
The effluent database to date now includes preliminary sampling conducted during July, August,
and September (received 240ct2018), as approved by the DWR. These data support compliance
with permit limits for chlorinated hydrocarbons and metals over three (3) sample events [see
attached Tables 1,2, and 3 received DWR on 290U2018].
The final permit includes revisions to reflect the newly installed permanent treatment system (see
revised Supplement to Permit Cover sheet).
Summary of Changes to the Permit Draft
Arsenic limits revised to correct error for WS [150 ug/L / 340 ug/L => 10 ug/L / 10 ug/L]
2. Flow increased from 0.0005 to 0.0015 per the Permittee's request, consistent with system design.
Corrected Draft permit WET -Testing from TAA6C to TGE6C to reflect
freshwater, monitoring Monthly. this test can be modified to Quarterly upon
request after sufficient data indicating "Pass," per Aquatic TOX (Susan
Meadows, 06Nov2018).
4. Parameters of Concern qualifying under footnote 3 shall be submitted
collectively — not in batches, per John Hennessy.
Joe R. Corporon, L.G., NPDES Unit. 08Nov2018
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