NC0043532_Report_20070319

NPDES DOCIMENT :MCANNINO COVER :SHEET
NPDES Permit:
NC0043532
West Stanly / Oakboro WWTP
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Correspondence
Owner Name Change
e ter/.
Instream Assessment (67b)
Speculative Limits
Environmental Assessment (EA)
Document Date:
March 19, 2007
This document is printed on reuse paper. - lamtore any
content on the resrerse side

444,
y/s/20/, �-- -
MAR 2 7 2007
Chambers Enginering, PA
PO Box 1726
Albemarle, NC 28002
f`r CIT1 Ji`
Town of Ookbcro
TECHNICAL MEMORANDUM
SUBJECT: West Stanly Sewer
Treatment Capacity & Allocations
DATE: March 19, 2007
PURPOSE
The purpose of this memorandum is to briefly summarize wastewater activities in the West
Stanly area in terms of wastewater treatment plant (WWTP) capacity at the Town of Oakboro's
WWTP, currently committed WWTP capacity for West Stanly communities and to briefly
summarize and outline proposed steps towards increasing available capacity, including both
short term improvements and more established, permanent, long term capital projects. This
writing does not deal with collection or transportation issues related to the conveyance of
wastewater from the Locust/ Stanfield area to conveyance systems in Oakboro. In summary this
memorandum will establish the following:
➢ Review of existing Oakboro WWTP treatment capacities
➢ Quantification of WWTP flow commitments
> Summary of Improvements to Increase System Capacity
Rt:vii:w OF EXISTING OAKBORO \VWTP CAPACITY
The Oakboro WWTP (NPDES Permit NC0043532) is situated off of Barbee's Grove Road near
the confluence of Big Bear Creek and Long Creek. Treatment is provided by means of aeration
basins followed by secondary clarifiers and chlorination. Dechlorination is provided prior to
final discharge. The WWTP currently discharges to the Rocky River by means of a pump and
Page 1 of 6
Phone [phone] Fax [phone] email: [e-mail]

Town of Ookboro
force main configuration. The WWTP also has a secondary discharge point to Big Bear Creek
which is utilized as needed.
The Oakboro WWTP is permitted at a 0.9 million gallons per day discharge. Actual plant
configuration however is constructed to handle approximately 1.2 million gallons per day
without any substantial modifications to the WWTP. Upgrades would be required however at
the McCoy's Creek pump station to achieve this level of capacity. The McCoy's Creek PS
delivers all wastewater flows from Oakboro and West Stanly to the WWTP. This pump station
is currently rated at 0.9 million gallons per day. Additionally, a request to increase the plant
discharge from 0.9 to 1.2 mgd would be required by NC DENR. This request would require the
preparation of an Engineering Alternatives Analysis (EAA) as part of the permitting process.
Current non -rain event daily treatment level at the Oakboro WWTP is approximately 300,000
gallons per day which includes all sewer flows from Oakboro, Locust and Stanfield. Rain event
days producing Inflow/ Infiltration raise the treatment volume to approximately 1 million gallons
per day. It has been noted by WWTP operators that the increased I/1 flows have not resulted in
overflows at the WWTP.
It is also of significance that Oakboro is experiencing rainfall -induced I/1 within its' wastewater
collection system and also is accepting some I/I from other users. The combined effect is that
the McCoy's Creek Pump Station does experience periodic overflows which are reportable under
NC DENR rules. Excessive I/I is a common occurrence in most older wastewater collection
systems with newer systems experiencing 1/I on a somewhat smaller scale.
It should also be recognized that Oakboro has taken proactive measures in regards to the
reduction of I/I. A comprehensive Sanitary Sewer Evaluation Study was completed in June,
2005 with several of the findings and noted deficiencies corrected. Oakboro has also recently
initiated a repair project that has identified several areas contributing to I/I. Repairs to these
areas are contemplated within the calendar year.
Page 2 of 6

Town of Oakboro
QUANTIFICATION OF WWTP•FLOw COMMITMENTS
Based on data provided by the Town of Oakboro the following represents current Oakboro
WWTP flow allocation:
Flow Component
Average Daily Treated
Amount, Gal.'s
310,000
Oakboro Reserve/ Local Commitments
200,000
Locust Initial Commitment
90,000
Locust Purchased Commitment
33,400
Locust Commitment to Purchase
116,600
Stanfield Initial Commitment
45,000
Stanfield Purchased Commitment
105,000
Total Commitments
900,000
The above commitments to Locust and Stanfield are based on an Interlocal Governmental
Agreement between Locust and Stanfield and The Town of Oakboro. This agreement, among
other items, quantified the amounts and charges associated with the allocation of WWTP
treatment capacity. Upon exhaustion of the allocations in the agreement it will be necessary to
re -address the allocation procedure and corresponding cost of WWTP capacity.
It should also be noted that the allocation of WWTP capacity has traditionally occurred via a
"Flow Acceptance Letter". This letter is required by NC DENR upon the processing of a
wastewater extension permit. The permitted extension of sewers cannot occur without this letter.
The flow amount prescribed by NC DENR, for single family residential, is 120 gallons per day
per bedroom. This is usually expressed by the number of lots in a development times three
bedrooms times 120 gallons per day. Actual dry weather flows from single family residential
can vary from 45 — 75 gallons per day per person which results in an inherent amount of excess
capacity generated for every Flow Acceptance Letter.
To relate this condition it would be beneficial to review the current issued Flow Acceptance
Letters by the Town of Oakboro to The City of Locust. The following table summarizes Flow
Letters for Locust as reported by the Town of Oakboro:
Page 3 of 6

Town of Oakboro
Name of Development
Stanly Community College - Commercial
Flow Allocation
Gal.'s
Predicted Flow Gal.'s
12,000
12,000
Meadow Creek (232 Lots)
83,800
52,375
Locust Valley (65 Lots)
23,400
14,625
Locust Town Center — Commercial
10,000
10,000
Quail Run (5 Lots)
1,800
1,125
Whitney (20 Lots)
7,800
4,500
Locust Town Center (248 Lots)
89,280
55,800
Redbridge Phase 1 (117 Lots)
42,120
26,325
Business Park (Pending) - Commercial
40,000
40,000
Total Commitments
310,200
217,750
Although the above predicts a reduction in actual flow it does not account for extraordinary uses
or I/I, both of which could affect the actual wastewater flow generated. Commercial Flows were
not reduced. In general, when planning for capital projects it would be preferred to utilize sound
and proven flow numbers such as the 120 gallons per day per bedroom. Other accepted
standards utilize a per capita basis for flow determination and do not segregate by class of user,
i.e. residential, commercial. For this approach a number of 95 gallons per day per capita for
wastewater flows only could be utilized.
It should be noted that there are other flow commitments to Locust which may not be included in
the above table. Generally these commitments were accounted for in the original 90,000 gallon
commitment specified in the Interlocal Agreement and were reported as such to NC DENR.
SUMMARY OF IMPROVEMENTS TO INCREASE SYSTEM CAPACITY
As alluded to previously system demand at the WWTP is comprised of actual received flows
including sanitary sewer and I/I. Dry weather flows typically are comprised of only sanitary
sewer flow while wet weather conditions produce elevated flows due to I/I.
Several positions may be taken to increase effective treatment volume within a sanitary sewer
system. System components can be enlarged, i.e. larger pipes, pumps, increase of the WWTP
size, water reduction campaigns can be initiated, alternative discharges can be developed and
non -sanitary flows (I/I) can be reduced. The normal approach is to select a method, or
Page 4 of 6

Town of Oakboro
combination of methods, that provides for the greatest benefit for the least amount of capital
expenditure. For instance, in some cases it might be more cost effective to provide for the
treatment (plant expansion) of I/I rather than to locate and remove the 1/I. Other factors are also
relevant including providing for system redundancy and backup systems.
In the case of Oakboro it appears that a combination of efforts would seem practical. I/I
removal, as documented in the 2005 Sanitary Sewer Evaluation Study, should continue. That
report identified several areas that could be repaired in an economical manner. The Oakboro
WWTP could also be easily upgraded from the current 0.9 million gallons per day capacity to 1.2
million gallons per day. A cursory review of the Oakboro WWTP plant site and operations
revealed that an expansion to 2.4 million gallons per day would also be feasible. It should be
understood that the NC DENR permitting associated with a WWTP expansion could be
somewhat lengthy. However, it appears that Oakboro should not encounter any substantial
obstacles should it proceed with a plant expansion.
With that the following table outlines a possible strategy to increase capacity within the Oakboro
wastewater system:
Project Description
Estimated Capital Cost
Inflow/ Infiltration Removal
$ 500,000
WWTP Upgrade 0.9 to 1.2 MGD
$ 1,200,000
WWTP Upgrade 1.2 to 2.4 MGD
$ 7,200,000
Total
$ 8,900,000
The I/I removal project would consist of the replacement of previously identified brick manholes
with precast concrete manholes, the replacement of clay service lines and the repair of sewer
mains identified in the 2005 sewer report.
The WWTP upgrade to 1.2 MGD would involve pumping capacity upgrades at the McCoy's
Creek Pump Station, the installation of a parallel force main to the WWTP from the pump station
and the permitting of the additional treatment capacity at the WWTP.
The 1.2 to 2.4 MGD upgrade would involve a physical expansion of the WWTP including the
construction of aeration basins, clarifiers, disinfection, filtration and upgrades to the McCoy's
Page 5 of 6

Town of Oakboro
Creek Pump Station and the WWTP discharge pump.station. For planning purposes it should be
taken that this expansion would cost $6 per gallon for all improvements.
Overall the Town of Oakboro is in an enviable position as a provider of wastewater treatment
services. Outside of I/ I concerns the wastewater collection system, transportation components
and treatment works are in very stable condition and appear to be well maintained. Moving
forward however the Town will need to develop and implement a system whereby needed capital
for system expansion/ capacity development is acquired. This system should provide for a stable
and secure revenue stream whereby planned improvements are adequately funded whether
through contributed capital or guaranteed user revenues. Contributed capital would normally be
collected through up -front capacity charges. This method should provide the most stable
revenue source as it would typically be collected in advance of the need for the capacity. Funds
should be deposited into a restricted asset account for the express use of wastewater system
capacity improvements. Standard local government accounting procedures should be followed
in this regard. User fees on the other hand would equate to a "pay-as-you-go" strategy and
would require the Town to utilize financing mechanisms to effect capacity upgrades. User fees
would then be relied on for debt service. It is seldom the case to have the luxury of 100%
contributed capital for public works projects as contemplated herein. However, proper planning
and scheduling of projects to match capacity demand should help to minimize the need for
outside financing.
In regards to capacity charges the Town should review the capacity fee structure as detailed in
the current Interlocal Governmental Agreement to reflect current capital needs and to reflect
current construction costs. Once established this fee should be reviewed annually and updated as
required. Additionally it would be advisable that all contributors to the Oakboro wastewater
system participate in a capacity charge system.
r w
17943
•S
s'�,yt��'•�;QlNf�;��', Al A
Page 6 of 6