NC0025381_Performance Sumary_20080317

NPR l'�+,�;� h�Ito: rvcn2s3s 1
INDEPENDENT PERFORMANCE EVALUATION
(AS REQUIRED BY ITEM VI.5 OF SPECIAL ORDER BY
CONSENT APPLICATION)
for
TOWN OF LAKE LURE
WASTEWATER TREATMENT PLANT
RUTHERFORD COUNTY, NORTH CAROLINA
RANDALL D. HINTZ, P.E.
McGill
ASSOCIATE S
Engineering • Planning • Finance
Post Office Box 2259
As ' , h Carolina 28802
APRIL 2007

TABLE OF CONTENT
SECTION I Introduction 3
SECTION II Existing Systems & Performance
Existing System 4
Current NPDES Permit Requirements 4
Monthly Summary of Effluent
Discharge Characteristics 5
Annual Summary of Effluent
Discharge Characteristics 6
Recent History of Notices of Violation 6
SECTION III System Evaluation
Infiltration and Inflow 7
Summary Unit Process Evaluation 9
SECTION IV Conclusions and Recommendations
Priority 1 Activities 14
Priority 2 Activities 15
Priority 3 Activities 16
Compliance Certification 16
SECTION V Project Implementation Schedule 18
SECTION VI Appendix 19
Current NPDES Permit
Wastewater Treatment Plant Discharge
Monitoring Reports (2002 — 2006)
Summary of Weekly and Monthly Flow Characteristics
2

SECTION I INTRODUCTION
The Town of Lake Lure has commissioned McGill Associates to conduct an
evaluation of the Town's existing wastewater treatment plant. This evaluation has been
triggered by a number of recent permit noncompliance issues at the facility that appeared
to be linked to excessive levels of solids within the plant which have led to poor
performance of the facility. Therefore, it is expected that potential future permit
noncompliance may also be expected until improvements at the facility that will reduce
the volume of solids within the treatment basins can be completed.
The Town of Lake Lure is currently rehabilitating its existing wastewater
treatment plant. The focus of this rehabilitation is to improve the facility's ability to
remove sludge from the process more efficiently. A detailed description of the specific
improvements associated with this project is contained in Section IV of this evaluation.
In addition, the Town of Lake Lure is concurrently conducting an infiltration and
inflow on the collection system draining to the wastewater treatment plant. The goal of
this study is to locate sources and quantify the volume of extraneous water reaching the
plant. This investigation includes closed circuit televising of all accessible line segments,
smoke testing of all manholes, and the implementation of specific rehabilitation projects
developed based on the findings of this study. The reduction of extraneous water within
the collection system will provide additional capacity within the system for future
wastewater demands from the community while allowing the town to operate the plant
within its permitted parameters.
Concurrent with these efforts, this evaluation will identify ongoing efforts by the
Town of Lake Lure to improve the performance of its wastewater collection and
treatment systems, as well as recommend several additional measures to restore and
improve the operation of the wastewater treatment plant. These recommendations are
targeted at improving the permit compliance of the plant only and are not intended to be a
comprehensive list of recommendations for the facility. However, throughout the course
of the proposed SOC, it is expected that effluent quality at the facility may remain similar
to its current performance levels or perhaps even decrease slightly as the necessary
modifications to the plant are being implemented.
3

SECTION II EXISTING SYSTEM & PERFORMANCE
EXISTING SYSTEM
The Town of Lake Lure owns and operates a wastewater treatment plant which
has permitted capacity.of 0.995 million gallons per day (MGD). The facility consists of
an influent pump station, bar screen, flash mixer, flocculation basin, sedimentation basin,
secondary clarifier, and chlorine contact chamber. The discharge for this facility under
NPDES permit number NCO025381 is into the Broad River, Class B-Trout waters in the
Broad River basin.
A traveling bridge filter is a component of the process that is no longer in
operation at the facility. The operator of the facility indicated that backfill against the
unit caused the tank to warp, rendering the unit inoperable shortly after its installation.
Based on DMR information provided by the operator from January 2002 through
December 2006, plant effluent flows are averaging 0.768 MGD for the period (77.2% of
permitted levels). Effluent biochemical oxygen demand for the period is averaging 5.51
mg/L (18.4% of permitted levels), effluent total suspended solids for the period are
averaging 22.38 mg/L (74.6% of permitted levels), ammonia is averaging 2.03 mg/L
(47.2% of permitted levels), while fecal coliform levels are averaging 22.95 (11.5% of
permitted levels) and residual chlorine levels are averaging 7.5 µg/L (26.8% of permitted
limits).
CURRENT NPDES PERMIT REQUIREMENTS Permit Number NC0025381
Flow: 0.995 MGD (Monthly Avg.)
BOD5: 30.0 mg/L (Monthly Avg.), 45.0 mg/L (Weekly Avg.)
Total Suspended Solids: 30.0 mg/L (Monthly Avg.), 45.0 mg/L (Weekly Avg.)
NH3 as N (4/1— 10/3 1) 4.3 mg/L (Monthly Avg.), 12.9 mg/L (Weekly Avg.)
pH 6.0 to 9.0 s.u.
Fecal Coliform: 200/100 ml (Monthly Avg.), 400/100 ml (Weekly Avg.)
Total Residual Chlorine 28 µg/L (Daily Max.)
4

MONTHLY SUMMARY OF EFFLUENT DISCHARGE CHARACTERISTICS
MONTH
FLOW
(mg,L)
BOD
(m,g/L)
TSS
(mg/L)
NH3 as N
(mg/L)
FECAL
COLIFORM
RES. CL2
OWL)
1/2002
0.575
5.8
26
3
0
2/2002
0.490
6.0
24
3
0
3 2002
0.479
3.5
27
3.3
4
0
4/2002
0.503
7.2 1
46
3.7
2
0

ANNUAL SUMMARY OF EFFLUENT DISCHARGE CHARACTERISTICS
YEAR
FLOW
(m /L)
BOD
m /L
2002
0.657
5.07
2003
0.758
6.46
2004
0.749
4.35
2005
0.822
4.05
2006
0.853
7.62
Average
0.768
5.51
RECENT HISTORY OF NOTICES OF VIOLATION
The following is a list of violations compiled based on information provided by
the Town of Lake Lure and the North Carolina Division of Water Quality for the period
from 2002 to 2006.
DWQ Case No.
Violation
Date
LV-2002-0434
Total Suspended Solids (weekly & monthly)
04/2002
LV-2002-0438
Total Suspended Solids (weekly & monthly)
05/2002
LV-2002-0681
Total Suspended Solids (weekly)
09/2002
LV-2003-0612
Fecal Coliform (weekly)
06/21/2003
LV-2003-0778
Fecal Coliform (weekly)
09/06/2003
LV-2004-0204
Fecal Coliform (weekly)
10/04/2003
LV-2004-0323
Fecal Coliform (weekly)
05/2004
LV-2004-0437
Fecal Coliform (weekly)
06/26/2004
LV-2007-0032
NH3-N (monthly), TSS (weekly & monthly)
07/2006
LV-2007-0033
Fecal Coliform (weekly), NH3-N (monthly), TSS (weekly
& monthly)
08/2006
LV-2007-0034
Fecal Coliform (weekly), TSS (weekly & monthly)
09/2006
LV-2007-0035
Flow (monthly), TSS (weekly & monthly)
10/2006
LV-2007-0036
Flow (monthly), TSS (weekly & monthly)
11/2006
rol

SECTION III SYSTEM EVALUATION
INFILTRATION AND INFLOW
Background
The original developers of Lake Lure in the mid 1920's had the foresight to
recognize the need to manage sanitary sewer from their proposed development. With the
lake as an enticement for development in the area, maintaining the purity of the lake was,
and remains, a major concern. To address the need for sanitary sewer service, the
developers of Lake Lure elected to install a sanitary sewer collection system on the
bottom of the lake in conjunction with the construction of the dam.
The original system consisted of approximately 14.0 miles (112 inch -miles) of
cast iron sewer line ranging in size from 8-inch to 20-inch and 54 cast -in -place manholes.
The system is composed of a main sewer line, ranging in size from 10-inch diameter cast
iron pipe (CIP) at the upper end of the lake to 20-inch diameter CIP at the dam. From the
main sewer line there are two major laterals, the 12-inch diameter CIP Buffalo Creek line
and the 12-inch diameter CIP Tryon Bay lateral. In order to provide sewer service to the
various areas along the lake, laterals were installed from the main to the edge of the lake.
The majority of these are 8-inch diameter CIP lines and end at manholes located at the
edge of the lake. Sewer connections from private sewer lines. were made above this
point. The original sewer system was designed and installed following the natural
drainage ways prior to filling the lake. This system remains is operation today. The
exposed portion of the system has received repairs and rehabilitation over the years, but
has not been significantly extended beyond the scope developed in 1926.
When first constructed, the new sewer system collected wastewater from those
homes connected to the system and conveyed wastewater to the Broad River at the
downstream side of the dam. No treatment of the wastewater was required when the
system was first placed into service. Wastewater treatment simply consisted of dilution
of the wastewater in the Broad River with treatment occurring due to the biological
7

capacity of the river to handle the waste. Without the need for treatment, little emphasis
was placed on reducing the quantity of infiltration of lake water into the sewer system. In
fact, it was believed that increased infiltration of lake water would simply increase the
dilution of the wastewater discharged to the river and therefore, minimize the negative
impact on water quality.
With the passage of the Clean Water Act by the United States Congress in the
early 1960's and increased public concern of damage to the waterways of America due to
the discharge of untreated sewage, the Town of Lake Lure was mandated to construct a
wastewater treatment plant. Plant construction was completed in 1969. Based upon
discussions with the contractor who built the original wastewater treatment plant, flow to
the facility actually exceeded the design capacity from the original start-up of the facility.
Since that time, there have been various upgrades to the plant to allow the facility to
attempt to meet effluent discharge limits as stipulated in the town's NPDES Discharge
Permit.
Evaluation
For many years, infiltration and inflow (I/I) into the sanitary sewer collection
system has played a significant role in reducing the efficiency of the Town of Lake
Lure's wastewater treatment plant and collection system. While average daily flows to
the plant currently average approximately 0.853 MGD (in 2006), the anticipated flow
from the customers connected to this system is only approximately 200,000-250,000
GPD. Therefore, I/I are major contributors to the flows experienced by the town's
wastewater treatment plant. For this reason, the Town of Lake Lure's collection system
experiences only minor variations as a result peak daily or seasonal flows, even though
the town's population varies considerably from the summer to winter seasons.
The Town of Lake Lure has recently undertaken a program of closed circuit
television inspection of its collection system and is currently smoke testing the manholes
within its collection system with a goal of identifying significant sources of I/I within the
system. The town has also recently completed a series of manhole inspections and
repairs to reduce extraneous water within the collection system.

SUMMARY UNIT PROCESS EVALUATION
The purpose of this section is to review each process unit within the treatment
facility, evaluate its effectiveness and identify any problems.
Influent Pump Station
The gravity sewer system carries wastewater to an influent pump station located
at the base of the dam approximately 1600 feet from the wastewater treatment plant site.
Flow is pumped through a triplex suction lift pump station to the 1 S-inch gravity sewer
system which flow to the wastewater treatment plant bar screen. This pump station has
three pumps each rated at 459 GPM and was constructed in 1999 to replace the previous
pump station constructed as part of the original facility. This station appears to be
operating properly and working well.
Manual and Mechanical Bar Screens
Flow from the influent pump station flows by gravity to the bar screen assembly.
It consists of both a mechanical screen and a downstream manual screen in series within
the same channel. For the purpose of maintenance and repair, the Envirex climbing
screen can be rotated out of the channel which allows the manual screen to remain in
service. The manual screen has bars with approximately 1-inch clear openings between
bars. The mechanical screen was installed as part of a series of improvements to the
plant in 1992. The equipment has some rust on the metal enclosure, and has been known
to have some mechanical difficulties through the years, but is functioning, according to
the operator.
This wastewater treatment plant utilizes a physical/chemical process to treat the
wastewater entering the facility rather than a biological process. Therefore, wastewater
entering the facility is chlorinated in a small basin just upstream of the screens.
10

Alum Feed System
The alum feed system consists of a 5,000 gallon poly bulk chemical storage tank
and an adjacent chemical transfer pump located within an enclosed structure that was
constructed in the location of the former sludge drying beds. A sump pump within this
enclosure is designed to collect moisture from the building and pump it into the
sedimentation basin. However, spilled alum from the chemical feed system has entered
the sump pump resulting in the failure of this pump. Therefore, the floor of this area
collects standing water periodically. The chemical transfer pump also shows signs of
significant wear, however it is functional.
The 50% liquid alum solution is pumped by the transfer pump from the bulk tank
into a 150 gallon poly day tank within the control building. According to the operator,
alum has crystallized within the feed lines running from the day tank to the flash mixer.
Therefore, the operator has employed a garden hose and a small ball valve which
regulates and delivers the alum solution directly to the flocculation basin.
Flash Mixer
Flow from the bar screen enters the flash mixer. The flash mixer at this facility is
designed to mix the alum received from the chemical feed system with the screened
wastewater entering the mixer. This unit appears to have not functioned.for some time.
The equipment is rusted and the concrete walls of the basin are caked with debris. The
flow currently passes through this basin without treatment.
Flocculation Basin
The flow within the facility next passes through the flocculation basin. The
flocculation basin is designed to received flow from the flash mixer and allow contact
time between the wastewater and the alum solution mixed within flash mixer. Like the
flash mixer, the flocculation equipment appears to have not functioned for some time.
The equipment and associated walkway over the basin are rusted and the basin contains
both floating and settled solids. The garden hose from the chemical feed system,
11

described above, runs over the ground to this concrete basin with a slow stream of alum
solution entering process at this point. Other then this chemical addition, no other
treatment takes place in this basin.
Sedimentation Basin
The next step in the treatment process within this facility is the sedimentation
basin. Wastewater which is mixed with the alum solution enters this concrete basin. The
basin is approximately 90 feet long and 46 feet wide at the surface. It has a water depth
of approximately 9.8 feet, sloping sides and a flat bottom with approximate 67 foot by 23
foot dimensions creating a liquid volume of approximately 200,000 gallons. This basin
contains two platforms and walkways used to access adjustable decanter piping. This
basin also contains a series of perforated ductile iron pipe sludge underdrains designed to
remove the sludge from this basin and drain it to the sludge pump station adjacent to the
basin. However, these underdrain pipes operate with only limited success in removing
the sludge from this basin. Therefore, significant amounts of sludge have accumulated
within this basin, with both settled and floating solids within this basin.
Secondary Clarifier
Flow exiting the sedimentation basin enters the secondary clarifier which is
constructed of concrete and has a diameter of approximately 27 feet and a sidewater
depth of approximately 9.5 feet. This equipment and the associated walkway are also
very rusted and the equipment not functioning. Sludge piping within the basin is design
to drain sludge from the clarifier to the sludge pump station. However, without an
operable clarifier mechanism, little sludge is removed from this basin. Therefore, this
basin also contains a significant quantity of sludge, both floating and settled. This basin
also contains tube settlers designed to improve the efficiency of solids settlement within
the basin. However, a large volume of solids has settled within and on top of the tube
settlers significantly reducing their effectiveness.
12

Sludge Pump Station
The sludge pump station is designed .to draw sludge from the bottom of the
existing sedimentation basin and the secondary clarifier and pump it to the digester. The
station consists of a simplex suction lift pump system. Sludge from the sedimentation
basin and secondary clarifier flows by gravity into a wet well as valves within these
basins are opened. According to the operator, the existing pump station is capable of
filling digester only approximately 50 percent. Therefore, the operator has a portable
pump sitting beside the sludge pump station and utilizes this equipment as necessary to
fill the digester.
Digester
The digester receives sludge from the sludge pump station. The digester is a 26-
foot diameter, 32-foot tall bolted steel open -top tank with a capacity of approximately
120,000 gallons. This tank was.installed in 1992 in conjunction with other improvements
at the facility and has provided good service. It currently is in good condition with some
surface rust on the steel components.
Chlorine Contact Basin
Effluent from the secondary clarifier flows into a chlorine contact basin that is
approximately 15 feet long, 8 feet wide and has water depth of approximately 6.5 feet.
Since chlorine is added to the wastewater stream as it enters the facility, the chlorine
contact basin does not currently serve its intended purpose. Instead, the basin currently
contains a dechlorination system consisting of a tablet fed system installed at the effluent
of the basin. This basin also contains an unusually large volume of sludge. A
refrigerated sampler is located immediately adjacent to the basin and samples the
wastewater as it exits the basin. Flow from the chlorine contact basin in discharged into
the Broad River.
13

Traveling Bridge Filter
The traveling bridge filter is a component of the process .that is no longer in
operation at the facility. The operator of the facility indicated that backfill against the
unit caused the steel tank to warp, rendering the unit inoperable shortly after its
installation.
14

SECTION IV CONCLUSIONS AND RECOMMENDATIONS
Based on our observations of the Town of Lake Lure's wastewater treatment
plant, a review of the system, an evaluation of the wastewater treatment plant compliance
and process control data, and conversations with the staff of the Town of Lake Lure, we
draw the following conclusions and make the following observations and
recommendations:
Priority 1 Activities
The primary focus of short term actions must be to reduce the volume of sludge
within all basins of the Town of Lake Lure's wastewater treatment plant. Once the
efforts to remove the sludge are complete, the focus must then shift to providing
equipment within the facility that is designed to efficiently remove sludge from the
facility and maintain more desirable sludge levels.
The rehabilitation of the existing wastewater treatment plant that is ongoing is
designed to replace the equipment within several of the basins that is currently not
functioning well or not operating at all. The scope of this project includes the installation
of new sludge removal equipment within the sedimentation basin, new equipment within
the existing clarifier, and a new sludge pump station. In addition, this project will
provide new flow -paced alum feed equipment and a new refrigerated composite sampler.
In conjunction with the rehabilitation work currently under contract, the Town of
Lake Lure has committed to the rehabilitation of the existing flash mixer utilizing its own
forces. In addition, it is recommended that upon completion of the currently contracted
improvements, the operator of the facility consider jar testing to determine the most
effective chemical additive and an appropriate feed rate to maximize the settling
efficiency of the wastewater within the plant.
In addition to the rehabilitation work currently underway at the wastewater
treatment plant, the Town of Lake Lure is also in the midst of a study evaluating
infiltration and inflow (1/I) within its collection system. The goal of this study is to
15

identify and reduce I/I within the collection system. Given the magnitude of the I/I
component within the overall volume of flow reaching the wastewater treatment plant
and the fact that the plant is approaching its permitted capacity, it is critical that town
continue these efforts to reduce I/I within the collection system to the greatest degree
practical.
Priority 2 Activities
As indicated above, the rehabilitation of many components of the existing
wastewater plant is ongoing. However, due to budgetary constraints, the full scope of the
recommended improvements to the facility could not be realized within the current
contract. As a result, the Town of Lake Lure was forced to -prioritize those components
of the rehabilitation that had the greatest need. The balance of these improvements is
recommended to be accomplished in this and the following sections of priorities.
The existing mechanical bar screen has recently had some mechanical failures.
Given the condition of this equipment, it is recommended that it be replaced with a new
mechanical screen. It is recommended that a new spiral screen with an integral screw
compactor be installed within the existing basin. The equipment should include a
discharge chute that delivers the screenings to a dumpster adjacent to the existing basin.
Also, as described above, the existing flocculation basin equipment has ceased to
operate. Therefore, it is further recommended that the existing flocculation basin
equipment be removed and replaced with new equipment. In conjunction with this
equipment replacement, the basin should be thoroughly cleaned with all sediment and
other debris and deposits removed from the basin.
In conjunction with these improvements, it is recommended that a new
dechlorination system to be installed. The existing dechlorination system is not adequate
for a plant processing the flows experienced by this facility. This system should be
replaced with a gas sulfur dioxide system, similar, to the gas chlorination already in place
with the .exception that the dechlorination system could,' perhaps, utilize 150 pound
chemical cylinders rather than the one ton cylinder currently in use within the
16

chlorination system. It is further recommended that this new dechlorination system be
flow proportioned based on a signal from the effluent flow meter which is being installed
in conjunction with the current treatment plant improvements.
The final recommendation associated with phase of activities involves the
construction of a partial enclosure around the existing chemical storage area. Currently,
the existing area utilized to store the one ton chlorine cylinder is covered, but lacks walls
that could block harmful sunlight from reaching the steel chemical storage tank. It is
recommended that walls be constructed on two sides (south and west) of the tank to
shelter the tank from the harmful rays without fully enclosing the area and requiring
ventilation and monitoring equipment to be installed.
Priority 3 Activities
A major component of the originally proposed improvements at the wastewater
treatment plant was the construction of an additional secondary clarifier. However, due
to the budgetary limitations described above, it was not possible to have this component
included in the rehabilitation that is currently under construction. Through the bid
process associated with the current rehabilitation work and the negotiations with the low
bidder, it was learned that the proposed clarifier was a significant cost consideration in
this work. Therefore, while the construction of this proposed clarifier is critical to
improving the performance of the plant, the construction of the proposed clarifier has
been shifted to a Priority 3 Activity to allow time for the Town of Lake Lure to research,
apply and secure additional funding for this work. However, it is recommended that
concerted efforts be made to complete this application and acquisition process quickly so
that this much needed component of the treatment process can be constructed promptly.
COMPLIANCE CERTIFICATION
Based on a careful evaluation of the Town of Lake Lure's WWTP and the
operational activities of the town's staff, it is our conclusion that the facilities as they
exist today cannot be operated in a manner that will -result in consistent compliance with
Lake Lure's NPDES permit. Specifically, the existing mechanical equipment within the
17

plant is incapable of removing the excess volume of solids currently within the plant due
to the condition of this equipment. Significant improvements to the sludge removal
process within the plant have been designed, permitted and are currently under
construction. These improvements should effectively address the compliance issues at
the plant.

SECTION V PROJECT IMPLEMENTATION SCHEDULE
Following are the proposed completion dates for various critical project activities.
WWTP Improvements Substantially Complete:
Consider Chemical Feed System Changes at WWTP:
Submit Final Report to DWQ
February 29, 2008
May 31, 2008
July 31, 2008
19