Sewer Collection System Annual Performance Report
City of Eden, North Carolina
July 1, 2019 to June 30, 2020
|Facility/System Name:||City of Eden, Sewer Collection and Treatment System|
|Responsible Entity:||City of Eden, Terry Shelton, Interim City Manager|
|Person in Charge/ Contact:|
|Collection System and Pump Stations|
|Operator-in-Responsible Charge:||Mark T. Bullins: 336-397-4385|
|Mebane Bridge Wastewater Treatment Plant|
|Operator-in-Responsible Charge:||Melinda S. Ward: 336-627-1009|
|Sewer Collection System:||WQCS00018|
|Mebane Bridge Wastewater Treatment Plant:||NPDES Permit NC0025071|
|Land Application of Wastewater Residuals:|| NC Permit WQ0003035|
Description of Collection and Treatment Process:
The collection system consists of 161+ miles of gravity and 19.4 miles force main sewer pipelines. The pipelines are composed of a mixture of clay, PVC, RCP, steel and ductile iron pipe, ranging in size from 6 to 36 inches. Age of the sewer pipelines range from new to more than 60 years old. Collection is accomplished by gravity from homes and businesses until it is necessary to pump from low elevations in force main sewer lines that transport the sewage to the treatment plant. There are 20 pump stations in the collection system. These range in size from pumping a few thousand gallons per day to more than five million gallons a day (MGD). The City has one primary collection drainage area. All of the city sewer drains, collects, or is pumped to the Mebane Bridge Wastewater Treatment Plant (MBWWTP), which can treat 13.5 MGD.
The MBWWTP has treated on average about 3.970 MGD this past year. This is a decrease from last year, but mostly because of wet weather the previous year. Currently, the Mebane Bridge plant is operating at a little less than one third of its capacity. The plant has mechanical barscreens to remove larger inert material, a grit removal system following the bar screens, and a fine screen after the grit removal system to further remove any material that is missed by prior treatment systems. Extended aeration using activated sludge is the next process to reduce and remove biochemical oxygen demand and ammonia. The sludge is separated from treated water by circular clarifiers. Collected sludge or biosolids are wasted to the aerobic digester or returned to the aeration system. The biosolids from the digester are then dewatered and land applied on permitted sites. We recently installed a new CleanB treatment system for the solids that eliminates the digester but does the same treatment in minutes instead of days. Treated water to the effluent leaves the clarifiers and is disinfected with chlorine and then dechlorinated. The treated effluent is then returned to the Dan River meeting all State Permit Discharge requirements.
The City of Eden is presently under an administrative order on consent reissued by the Environmental Protection Agency to eliminate sanitary sewer overflows that continue to occur from its sewer collection system. We have until February 28, 2022 to complete all improvements.
The City has Collection & Distribution field personnel to respond to emergencies in order to maintain the sewer collection system. Their job is to repair broken lines, installation of new sewer line, mow and maintain sewer outfall lines, and respond to, rectify and mitigate sewer bypasses. Personnel are on call nights and weekends year round to respond to emergency problems in the collection system. The City’s 20 pump stations are monitored by (2) Collection & Distribution Operators 24 hours per day, 7 days per week, by remote telemetry (Mission Communications) and physically checked on normal workdays by Collection & Distribution personnel for proper operation. Maintenance crews along with C&D personnel perform scheduled preventative maintenance on each of these pump stations to protect the equipment and insure long life. An extensive warehouse of supplies and parts are maintained to address emergency breakdowns and failures in the pump stations and the sewer lines.
The following was accomplished during fiscal year 2019-2020:
- A total of 21 Inflow & Infiltration problems were responded to and repaired.
- A total of 135 laterals and 83 sewer mains were responded to and unstopped.
- A total of 17.17 miles (90,706.1 linear ft.) of sewer mains throughout the City of Eden were cleaned by sewer jet or rodder.
- A total of 5.25 miles (27,752.7 linear ft.) of sewer mains throughout the City of Eden were inspected by CCTV throughout the City of Eden.
Treatment Plant Operators are on duty 24 hours per day, 7 days per week, to ensure proper treatment of all incoming wastewater. They monitor plant equipment and do inspections during each shift to insure process control and the mechanical operation of the equipment. Maintenance personnel are available each day to service equipment and are on call nights and weekends for emergency repairs in case the treatment equipment suffers failure. A large parts inventory is maintained of the items that have historically been prone to failure.
Collection System Operations
There were 17 events in the past 12 months during which 40 incidents occurred where raw sewage overflowed or bypassed from the gravity collection system to surface waters. The overflows from these gravity flow pipelines in the collection system, most of which were immediately upstream of pump stations, totaled 628,500 gallons, with 627,500 gallons reaching surface waters. Twenty-seven of these overflows were caused by Inflow & infiltration directly from storm water runoff and the resulting flood waters flowing into the gravity sewer mains.
There were 17 overflows that did not involve pump stations. Of these, eight were caused directly or indirectly by I/I, one major overflow was caused by pipe failure in a sanitary sewer gravity main when a log jam carried by flood water took down 150 feet of an aerial line on the Smith River Railroad Trestle. Four subsequent overflows at this location were caused by pipe or equipment failure during a bypass pumping operation. The other four were overflows caused by blockages. One was from grease buildup, two were caused by root growth and another was from a buildup of disposable wipes. Gravity sewer line losses account for 414,200 gallons of the sewage lost in the last 12 months.
Of our 20 sewer pump stations; (6) pump stations had sanitary sewer overflows during the last 12 months in 12 events. These were as follows: three overflows occurred at Covenant Branch Pump Station releasing a total of 80,000 gallons, ten overflows occurred at Railroad Pump Station releasing a total of 56,280 gallons, two overflows occurred at Meadowgreens Pump Station releasing a total of 5,200 gallons, two overflows Junction Pump Station releasing 63,700 gallons, three overflows occurred at New Street Pump Station releasing a total of 7,520 gallons and one overflow occurred at Dan River Pump Station releasing 1,600 gallons of raw sewage. All except 400 gallons entered surface waters. Pump stations account for 214,300 gallons of the sewage lost. The cause for these overflows was inflow and infiltration of storm water and flood water
When overflows or bypasses occurred, the affected sites were evaluated, cordoned off from or otherwise isolated from the public and/or receiving streams and monitored for environmental impacts as conditions dictated.
*Numerous sources of inflow & infiltration continue to be identified and repaired.
Treatment Plants Operations
Compliance with North Carolina NPDES (National Pollution Discharge Elimination System) Permit is based on meeting discharge parameters set forth in the NPDES Permit. This information is reported monthly to the North Carolina Department of Environment and Natural Resources through self-monitoring reports. The following is a summary of our plant permit compliance for the last 12 months:
Mebane Bridge Plant
|December 2019||Compliant *|
*On December 9th and 10th, samples were collected and sent to the contract lab. An error occurred at the lab that caused the samples to not be analyzed. By the time the error was detected, the samples were no longer viable. It appeared as a violation to the State, but we did our part and could not control the lab, so it was deemed in compliance.
This report will be submitted to the State Division of Water Quality and be released to the local news media and posted on the City’s internet web site at www.edennc.us.
“I certify, under penalty of law, that this document and all attachments were prepared under my direction of supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fines and imprisonment for knowing violation.”