The City of Corvallis retained Kennedy/Jenks Consultants to complete a Total Maximum Daily Load (TMDL) Alternatives Evaluation for the Corvallis Wastewater Reclamation Plant (WWRP) discharge to the Willamette River. The purpose of the project is to evaluate long-term compliance with current National Pollutant Discharge Elimination System (NPDES) Permit limits, assess the economic impacts of current and potential future regulations, and evaluate alternatives to direct Willamette River discharge. The evaluation consists of two Technical Memoranda (TM):
The Willamette River TMDL Project is currently on hold due to the Environmental Protection Agency's disapproval of a key component of Oregon's water quality standard for temperature. See the links below for more information.
In some of the older sections of Corvallis, sanitary wastewater and storm water are collected in the same pipe. During wet weather, these combined flows can exceed pipeline and wastewater treatment plant capacity. This results in the overflow of a mixture of untreated wastewater and storm water (called "combined sewer overflows" or "CSOs") into the Willamette River. The City undertook a program to change this practice in order to respond to water quality issues and federal/state requirements that Corvallis remediate CSOs by December 31, 2001.
Helping to prevent sewer overflows and backups is easy
Fats, oils, and grease can damage your home and the environment. Most of us know grease as the byproduct of cooking. Grease is found in such things as meat fats, cooking oil, shortening, sauces and dairy products. When these are washed down your sink, grease sticks to the insides of sewer pipes (both on your property and in the streets). Over time, it can build up and block the entire pipe. The results can be:
Most of the time, the City's sewer pipes have adequate capacity to carry wastewater to the treatment plant. But during heavy, extended raining periods when the ground water is high, the capacity of some sections of the sewer system is exceeded. Ground water or surface water will enter older sewer pipes through cracks and, added to the wastewater flow, will exceed the space available in the pipe. When these conditions occur the water has to go somewhere. If it can't flow down the main pipe, it will back up into the service line and, possibly, all the way into the basement.
The wastewater collection system in Corvallis gathers sanitary sewage from sinks, tubs, toilets, and other household and commercial drains, and transfers it to the wastewater plant for treatment. There are over 200 miles of pipe ranging in size from 4 to 72 inches in diameter that make up the collection system, along with 3,900 manholes which provide access to the system.
The City of Corvallis operates one wastewater treatment plant, maintains over 200 miles of wastewater collection pipes, and treats over 4 billion gallons of wastewater a year. The sanitary sewer system is a gravity system, which uses eight pump stations to move the wastewater from lower elevation portions of the system to the treatment plant located at NE 2nd Street. The treated wastewater goes through a rigorous series of tests to assure water quality is not compromised as it is discharged back to the Willamette River.
