The Basin 3 Sewer Rehabilitation Project will replace old, failing sewer system infrastructure that has deteriorated beyond the point of repair in the northern section of the downtown area. These improvements will eliminate current inflow and infiltration issues, increase the wastewater management system capacity allowing for additional service connections on the existing system, and reduce the city’s operating costs and energy consumption by reducing the amount of unnecessary inflow and infiltration that is treated at the wastewater treatment plant.
What is inflow and infiltration?
Inflow is stormwater that enters into sanitary sewer systems at points of direct connection to the systems. Various sources contribute to the inflow, including footing/foundation drains, roof drains or leaders, downspouts, window wells drains, outdoor basement stairwells, driveway drains, and groundwater/basement sump pumps. These sources are typically improperly or illegally connected to sanitary sewer systems, via either direct connections or discharge into sinks or tubs that are directly connected to the sewer system. An improper connection lets water from sources other than sanitary fixtures and drains to enter the sanitary sewer system. That water should be entering the stormwater sewer system or allowed to soak into the ground without entering the sanitary sewer system.
Infiltration is groundwater that enters sanitary sewer systems through cracks and/or leaks in the sanitary sewer pipes. Cracks or leaks in sanitary sewer pipes or manholes may be caused by age related deterioration, loose joints, poor design, installation or maintenance errors, damage or root infiltration. Groundwater can enter these cracks or leaks wherever sanitary sewer systems lie beneath water tables or the soil above the sewer systems becomes saturated. Often sewer pipes are installed beneath creeks or streams because they are the lowest point in the area and it is more expensive to install the pipe systems beneath a roadway. These sewer pipes are especially susceptible to infiltration when they crack or break and have been known to drain entire streams into sanitary sewer systems.
Inflow and infiltration reduce the ability of sanitary sewer systems and treatment facilities to transport and treat domestic and industrial wastewater. The excess clear water uses sanitary sewer capacity needed for wastewater. The result is sewer backups and increased costs for needlessly putting clear water through the wastewater treatment process. Additionally, wastewater treatment processes are disrupted and poorly treated wastewater is discharged out into the environment.
The illustration and video below demonstrate the varying sources of inflow and infiltration, and explain their impacts on the sanitary sewer sytem. The repairs made during construction will eliminate the current inflow and infiltration issues in the Basin 3 project area.
Thanks to strong support from our State Legislative Delegation, the City of Shelton is pleased to announce that the Basin 3 Sewer Rehabilitation Project is fully funded through a combination of competitive grants and direct state appropriations. The City of Shelton is part of Washington’s 35th Legislative District, which is represented by Senator Tim Sheldon, and State Representatives Drew MacEwen and Dan Griffey.
- Total estimated construction cost: $5,982,441.66
- Total funding received: $6,339,000.00
- Funding breakdown:
- Direct state appropriations = $4,365,000.0
- Department of Ecology Centennial Clean Water Grant = $1,974,000.00
scope of work
- All 290 service connections in the project area will receive new side laterals from the sewer main to within 2 feet of the house/building at no cost.
- Installation of 15,780 lineal feet of new 4” PVC side laterals.
- Installation of 6,990 lineal feet of new 8” PVC sewer main.
- Relining of 3,260 lineal feet of existing 8” sewer mains.
- Relining of 2,570 lineal feet of existing 15” sewer mains.
- Installation of 59 new manholes.
- Over 2 miles of new pavement overlay will be completed on roadways affected during construction operations.
- Restoration of all landscaping, lawns, and other surfaces disturbed during construction.
- Design completion date: December 2017
- Construction start date: April 2018
- Estimated completion date: June 2019
- Normal working hours: 7:00 AM to 5:30 PM, Monday through Thursday.
- Residents and businesses in the project area will be notified in advance of any sewer repairs that will directly affect their residence or place of business. Notifications will be in person or via door hanger.
- Important construction updates will be posted periodically throughout the duration of the project.
- Contractors will work to ensure disruptions are minimized during construction operations and will restore all worksites to their original condition.
- Noise and vibrations levels will be closely monitored throughout the project and will be minimize to the extent possible.
- The rehabilitation work requires that construction of a temporary by-pass pumping system that will consist of temporary pumps and piping either above the ground or buried. The temporary system will continuously pump the wastewater from the sewer and all individual service connections around the work area so that interruptions in sewer service are kept to a minimum during the rehabilitation work.
- Some sewage odor may be noticed temporarily during the construction operation.
- The protection of trees and shrubbery in the construction zone will be done in accordance with City of Shelton guidelines.
- Periodic roadway and lane closures are anticipated throughout the duration of the project. Signs will be on display designating the work area and rerouting traffic around the closure.
- Accommodations will be made for local traffic access throughout the duration of the project.
- There will be some temporary restrictions on parking throughout the project area to allow for sewer repair, manhole access, and location of construction equipment. These impacts on local parking will be minimized to the extent possible.
- Pedestrian access will be temporarily restricted in the construction zones as portions of the sidewalk immediately surrounding the excavation site will need to remain closed during sewer installation and/or repair.