Wastewater System
The City of Centralia sewer system has a gravity flow system which transmits raw wastewater to two different two-cell lagoons. The main purpose of this department is to maintain a smooth flow of wastewater through mains, prohibit blockages which affect the customer service, and to meet the DNR rules and guidelines for effluent treatment. This system also has the ability to pump treated wastewater to farmer’s ponds for irrigation on agricultural croplands.
Collection System:
The City of Centralia's sanitary sewer system consists of 37.5 miles of lateral, collector, and interceptor sewer mains and approximately 650 manholes.
Treatment System:
- Northeast Wastewater Treatment Facility: This facility is a two-cell lagoon with aeration equipment, spray irrigation pumps and a 40-acre overland flow field in size. Design population capacity of 6,600.
- Northwest Wastewater Treatment Facility: This facility is a two cell lagoon with spray irrigation 40-acres in size. Design population capacity of 1,460.
- Irrigation ponds: The City has ability to pump to three farmers’ storage cells. The sizes of these ponds are 21.9, 4.99, and 5.32 acres. These ponds serve 11 City-owned and farmer-maintained center-pivots that irrigate over 1,000 acres of agricultural land.
This system allows the City to eliminate the need to discharge to local creeks in times of high rainfall and infiltration. The overland flow fields will be eliminated as they will no longer meet DNR standards under the new permit. Therefore the City will have to identify new land resources and install application equipment to make up for 200 million gallons of treated effluent that were run through the overland flow fields in peak years. This part of the improvement plan and will be funded by the bonds sold under the authority available from the April 2018 bond election.
The City purchased an in-line sewer camera in July 2007 that will help identify any sewer main line problems. In the last decade, the City has achieved a considerable reduction of inflow and infiltration that would use up treatment plant capacity. Improvement to the City’s waste-collection system requires continual monitoring and inspection in order to limit infiltration and inflow issues. The City is also initiating line replacement (especially in clay tile areas) which will reduce infiltration and yield additional capacity. Large diameter interceptor sewers are now positioned to allow growth in almost any direction. Further development south of Gano Chance Drive and west of the COLT Railroad may require the addition of a new lift station.
Future Plans:
Plans have also been made for an extensive overhaul and expansion of the sanitary sewer wastewater treatment system, including new effluent disposal arrangements to conform to the latest state requirements. The system will be able to treat 200 million gallons per year.
