NC0020842_INSTREAM ASSESSMENT_19970507

NPDES DOCUMENT SCAMMINC COVER SKEET
NPDES Permit:
NC0020842
Snow Hill WWTP
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Speculative Limits
Correspondence
Instream Assessment (67B)
Environmental Assessment (EA)
Permit
History
Document Date:
May 7, 1997
This document is printed oa reuse paper - ig:zore a ay
coatexat on the re,%mwme side

DIVISION OF WATER QUALITY
May 7, 1997
MEMORANDUM
To: Robert Tankard
Roger Thorpe
From:
Thru: Donald L. of .t' N
Ruth Swanec
Carla Sanderson;
i
Subject: Response to Ins earn Assessment Request
Snow Hill WWTP (EMC WQ # 97-02)
NPDES Permit No. NCO020842
Greene County
Summary and Recommendation
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The Instream Assessment Unit (IAU) has reviewed the request for an instream assessment for the
Snow Hill WWTP. The Town is requesting a Special Order of Consent (SOC) during improvements and
possible expansion of the wastewater treatment plant. The existing design flow is 0.250 MGD.
Currently, the facility is discharging treated wastewater at approximately 0.290 MGD. It should be noted
that the monthly average discharge of 0.290 MGD was calculated using the last five months of facility data.
The flow meter for the effluent was incorrectly calibrated prior to that time, therefore the flow numbers
were suspect and not used to calculate an average.
The total requested SOC flow is 25,000 GPD, which includes 24,000 GPD of domestic waste and
1,000 GPD of industrial waste. The current average flow plus this additionally requested flow adds up to a
total requested SOC flow of 0.315 MGD. This total SOC flow request exceeds the currently permitted
design flow of 0.250 MGD by approximately 0.065 MGD. Due to problems with calibration of the flow
meter at the facility, no limit on flow is requested for this SOC, rather a flow monitoring requirment is
recommended. In addition, an SOC limit of a BOD5 = 45 mgA monthly average and 70 mg/1 weekly
average is requested. It should be noted that allowing this SOC is a significant step towards the expansion
of this facility.
It is recommended that if the SOC limits are given for the Snow Hill WWTP, that extensive instream
monitoring be a condition of the Order. Instream monitoring recommendations should be as follows:
Parameters: Temperature, Dissolved Oxygen, Conductivity
Frequency: 3/week in April through October, 1/week in November through March
Locations: 1) Highway 13 / 258
2) Highway 123
3) SR 1004
Dissolved Oxygen levels that go below 3 mg/1 should be closely monitored because anoxic
conditions instream may be detrimentatto aquatic life.

Snow Hill WWTP SOC NC0020842
Analysis and Discussion
Contentnea Creek is slow moving and characterized by low stream flows representing a swamp like
system. A review of current Level B model results, a QUAL2E performed in 1987, and current reaeration
field data collected by EPA, shows that Contentnea Creek cannot be evaluated with a steady state one
dimensional model. With the very low slopes, predicted velocities, and reaeration rates, the model output
generally determines a lower instream dissolved oxygen level than that which the instream data indicates.
The swampy system of Contentnea Creek cannot be accurately replicated using the traditional DO modeling
tools used by IAU, and more sophisticated modeling approaches will need to be researched.
Due to the inability to model the impact of this requested SOC, the IAU would request that a strict
schedule for achieving compliance with the permit limits be included. It was also noted in the SOC request
that the Town of Snow Hill plans to submit a 201 Facilities Plan in the near future with a focus upon
expansion of the current plant. To that end, we would offer this update to the DRAFT Neuse River
Nutrient Sensitive Waters Management Strategy.
Currently the Division of Water Quality (DWQ) is revising the draft nutrient sensitive waters (NSW)
strategy for the Neuse River based upon comments received during the public comment period. Based on
these comments, we are reviewing the possibility of including mass based nitrogen limits in the NPDES
( permits instead of the concentration limits currently proposed in the previous draft. Note, this updates the
' Speculative Limits for this proposed expansion as outlined in a letter to the Town of Snow Hill dated July
17, 1996. Annual nitrogen loading limits based on an effluent total nitrogen concentration of 3 - 4 mg/l and
1995 permitted flow may be included in the final strategy. For example, a 0.250 MGD facility would
receive annual TN loading limits based on the following equation:
TN loading limit (lb/yr) _ (0.250 MGD) * (3.5 mg/I TN) * (8.34) * (365) = 2,664 lb/yr
This annual load limit would be assigned in lieu of the monthly average TN limit of 6 mg/1 proposed in
the current draft rules. Since these lower concentrations will be used to assign limits in terms of annual
load and not monthly concentration limits, we do not expect that major differences in facility design would
result from changing the current draft rules to annual loading requirements. The General Assembly is also
examining the possibility of requiring dischargers in nutrient sensitive waters to install best available
nitrogen removal technology.
If you have any questions, please call me at 733-5083, extension 510.
cc: Bob Sledge
Central Files

r
DIVISION OF ENVIRONMENTAL MANAGEMENT
WATER QUALITY SECTION
April 1, 1997
M E M O R A N D U M
TO: Ruth Swanek
Instream Assessment Unit
THROUGH: Roger Thorpe vV
Washington Regional Office
FROM: Robert Tankard j:tw
Washington Regional Office
SUBJECT: Special Order By Consent
EMC WQ NO. 97-02
Town of Snow Hill WWTP
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Please find enclosed is a request for an instream assessment for huctd h
the Town of Snow Hill's WWTP. Snow Hill is requesting the SOC�
because they have not met limits in 1996 and want to avoid a civil
penalty for future permit violations. In the SOC request, they
state they are planning on a 201 Facilities Plan for expansion.
The Town has requested an additional 25,000 gallons of flow, 24,000
domestic and 1,000 industrial.
Please perform an instream assessment for the flow requested with
BOD and flow limits being modified from the permit. The WWTP
consists of a bar screen, contact chamber, reaeration chamber,
clarifier, chlorine contact chamber, aerobic sludge digester and
sludge drying beds.
If you should have any questions concerning this, please call.
attachments: Instream Assessment Request Form
Compliance Evaluation Analysis Report
CC: WaRO
Operations Branch
Central Files

Request Form for In -stream Assessment for 67(b) Analysis
NAME OF FACILITY _,,, j oc o O t t L, k)aff PERNUT I" N C. 0 O 2 oS 4 Z
COUNTY &t Enit REGION WA t.0 PERMITTED DESIGN FLOW
RECEIVING STREAM C.,j T6,yTnl t ig CRN�,r; SU13BASLN
REGIONAL CONTACT
BACKGROUND DATA:
A. Why is SOC needed? (Facility is out of compliance with which effluent limits?) tCZow a Z0])
If out of compliance with Flow limit, is it due to inflow/infiltration?
If I/I is a problem, then how much of the additional flow requested is the I/I?
B. SOC Request:
1. Monthly Average Wasteflow in the last year Q. 2S 3 j MGD o- Z85,-j iav` cS/09
(Pre-SOC Flow) f�L' 91/01
Time period Averaged y (0 O Z through 9 ? 01
2. Current SOC Flow request Flow: 0.01.S V MGD
(Flow added on during the Order)
3. Total plant flow (Post-SOC Flow) Flow: D- 2 % 0/ MGD
(total of 1. and 2. above)
okAt? d "( QogRq-
TANkme,I
O-31`I7�
4. Is this an accurate flow balance for plant? Why/why not? NO,
N6T C,*�,4R/1 TCaf fAAR d2.T�r PatoA, rt qto/Oq.
Are there any facilities that have recently gone off line?
NOTE: The SOC may not include an addition ofwasteflow; therefore B. above may not apply
and the region should fill out all other parts of this form. In cases where the SOC involves
violations of oxygen consuming or toxic limits, an evaluation may be necessary to predict the
water quality standard violations instream.
C. Please attach DMR summary for past year for all permitted parameters. If possible,
include reports from previous years if facility has been under SOC for more than a
year.

D. Briefly explain measures taken during the Order which will enable the facility to be in
compliance with permit limits at the end of the Order. J t A-4,j
CURRENT SOC REQUEST:
-'-A. Is -request for domestic or industrial waste? If a combination, please specify
percentages. 140 o o e M r3Ti c / o oo
B. If industrial flow, then what type of industry? Please attach pertinent data.
C. The region proposes the following SOC limits (all limits NOT listed here will remain
as in the current permit):
Conventional Parameters
jLo"J
.3oi
other parameters
D. What is the basis for these limits? ; /M2 S
Toxics�Toxiciry
� °J/- wK+-r:

' OPERATIONS BRANCH - WO
Fax:[phone]
Mar
20 '97
13:44
P._02_/05
COMPLIUICE
EVALTJATION
ANALYSIS
REPORT
PAGE 1
PERMIT--NCO020842 PIPE--001
REPORT PERIOD:
9602-9701
LOC---E
FACILITY --SNOW
NSLL, TOWN OF
- WWTF
DESIGN FLOW--
.2500
CLA$9--2
LOCATION --SNOW HILL
REGION/CODUPY--07
GREENE
50050
00310
00530
00610
21616
50060
OCO10
00400
MONTH
Q/MGD
EOD
RES/TSS NH3 +NH4-
FEC COLI
CHLORINE
TEMP
PH
LIMIT F
.2500 F
30.00 F
30.0
NOL
F 200.0
NOL
No
9.0 6.0
96/02
.2462
16.75
15.6
2.26
.0
.283
12.50
7.6-7.1
96/03
.2355
17.25
16e1
8.68
1.8
2875.000
12.5D
7.4-7.2
96/04
.2252
29.75
18.0
10.37
.0
2725.000
15.25
7.4-7.1
96/05
.2=68
26.20
12.6
7.75
3.1
2700.000
19.90
7.4-7.2
96/06
_2094
31.00F
10.8
9.17
7.2
2537.50D
22.37
7.4-7.3
96/07
.2296
41.40F
8.8
6.66
170.9
2550.000
24.30
7.4-7.2
96/08
-2256
30-25F
19.5
7.77
39.4
2637.500
25.62
7.5-7.1
96/09
2i73F
14.72
12.1
5.26
6.5
2712,500
25.00
7.3-6.2
516/10
2618E
13.10
5.6
4.78
71J.IF2830.000
22.30
7.4-7.0
9-4/ol . o.'a-8Ily
96/11
2741E
13.00
6.2
4.64
5.3
2687.500
188.00
7.1-7.0
96/13
3186�
25-90
13-7
6-89
4.2
2931.500
16.37
8.1-7.8
97/01
.3159E
15.32
11.1
4.65
.0
2700-000
14.70
7.9-7.0
AvaRACE
.2531
22.90
12.5
6.57
79.0
2507.731
19-06
bAZIMQN_
.4020
65.00
45.0
13.87
91000.0
3500.000
25.00
8.100
MINIi•IUN.
.1556
4.60 LESSTHAN
2.03
LESST.LMN
.250
il.00
6.200
UNIT
MGD
MG/L
MG/L
MGiL
a/10OML
UG/L
DEG.0
SU

OPE_RATIONS BRANCH - WO Fax:[phone] Mar 20 '97 13:44 P.03/05
COMPLIANCE EVALUATION ANALYSIS REPORT PAGEv J2
PERMIT--N00020842 PIPE--001 REPORT PERIOD; 9602-5701 LOC --- E
FACILITY --SNOW HILL, TOWN OF - W✓7TP DESI(SN FLOW-- .2500 CLASS-2
LOCATION --SNOW HILL REGION/COLRSTY--07 GREENE
00600 00665
MONTH TOTAL N PHOS-TCT
N0L NOL
96/02
96/03 17.450 2.0700
96/04
96/05
96/06 24.070 2.4300
96/07
96/08
96/09 16.890 _.5800
96/10
96/11
96/12 20.350 .0000
97/01
F+VZPBGL
19,690
1.5200
MAXIMM
24.070
2.4300
MINIMUM
16.890
1.5600
LRdIT
bSG/L
MG/L