NC0089702_NC0089702_Fact Sheet BINDER v2 Update Change Pages 30Aug2019_20190820_20190820

DocuSign Envelope ID: FECFC62E-CD7A-4DB5-A60B-582EAB145896
89702 Terwilliger Pappas Multi -Family Partners LLC —
Solis Brightleaf Apartments — Brownfields, Durham
Groundwater Remediation (GW-REM)
Joe's Rationale to Approve — Permittee's MOD Request
1) To relax Weekly sqmpling to Monthly (five parameters)
2) To increase flow from 1,500 gpd to 6,500 gpd [0.0015 to 0.0065 MGD]
1) RE: Relaxing Monitoring Frequency — Permit Table A. (L) includes a footnote (see
Footnote 3) allowing the Permittee to request relaxing limits and/or monitoring frequency
"...after securing a minimum of 12 samples (collected no more frequently than Monthly)
" Five (5) parameters monitored Weekly were inappropriately (?) ascribed by
Footnote 3 to pH, TSS, PCE, TCE, Total Chloride.
Since startup (-9 months), all five Weekly parameters have been analyzed 21 times and
remained undetected [below PQL] as of July2019 (see attached database). Considering
that these 21 samples well exceed the recommended 12 samples requested of monthly
parameters (despite data over one year), it is my judgement that current data suffice to
relax Weekly monitoring to Monthly, consistent with other Monthly analytes.
2) RE: Flow Increase — Flow monitoring data (Dec2018-Aug2019) show discharge
averaging 1,580 gpd (min. 42 gpd / max. 5,987 gpd, n = 50) under a flow limit of 1,500
gpd (NOV for flow issued by RRO). Clearly a permit flow increase is warranted. Flow
depends on groundwater infiltration to a given excavation likely influenced by local
rainfall.
Significantly, this permit is proposed to cover permanent dewatering of subsurface
parking after construction. Although the discharge is permitted under zero -flow
conditions, all parameters treated thru activated carbon remain within permit limits or
undetected. I therefore foresee no concerns with increasing flow.
CONCLUSION: I find the applicant's request reasonable to relax Weekly sampling to
Monthly and to increase flow to 6,500 gpd, as provided by the active.
Remaining, Question: Discharge concentrations for Chloride appear low (ave. = 63 mg/L; min =
34.1; max. = 85.7 mg/L). John raised concern about when they collect sample for Chloride. Do
data truly represent the discharge?

DocuSign Envelope ID: FECFC62E-CD7A-4DB5-A60B-582EAB145896
DENR / DWR / NPDES
FACT SHEET ADDENDUM - UPDATE
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:
20Aug2019
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 has been approved [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 future permanent
dewatering propose to discharge to a City of Durham's stormsewer (excavation currently in
progress). This effluent discharges under zero -flow receiving -stream conditions (7Q 10/30Q2 =
0.0 cfs). The Division hereby grants this update to permit limits and monitoring frequency as
allowed by footnotes in the active [see section A. (1.)].
The Permittee has requested an increase in permitted flow from 0.0015 MGD to 0.0065 MGD
based on recent data. They also request to relax Weekly monitored parameters to Monthly,
based on none detected above respective test -method practical quantitation levels (PQLs).
Although footnote #3 specifies sampling "no more frequent than Monthly," Weekly data well
exceed samples collected monthly for a year, thus are hereby judged sufficient to grant the
Permittee's request.
Permanent Dewater Facilities - The Division understands that future permanent dewatering
and treatment facilities will be designed to accommodate this increase in flow.
Joe R. Corporon, P.G., NPDES Unit. 20Aug2019
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