The Operations Division of the Public Works and Community Development Department manages Water Quality, which includes the sanitary sewer collection system, two wastewater treatment plants, and the stormwater system.

The sanitary sewer system includes over 100 miles of sanitary sewer pipes, 22 sanitary sewer pump stations, and two wastewater treatment plants (WWTPs). The City provides sanitary sewer service for Coos Bay and also treats raw sewage from Charleston and Bunker Hill special sanitary districts.

Wastewater Treatment Plant 1

The City of Coos Bay constructed its first Wastewater Treatment Plant, now known as WWTP1, in 1950. The plant included a control building, grit channel, clarifier, and anaerobic digester. Along with the construction of the treatment plant, collection lines were installed and pump stations were constructed. The plant was built in response to the Federal Water Pollution Control Act of 1948, which made it unlawful to  discharge any pollutant into navigable waters without a permit. 

WWTP1 was upgraded in 1972-1975 to include an additional digester, chlorine building, aeration basins, grit collector, and a final clarifier. These upgrades were due to the Federal Water Pollution Control Act Amendments of 1972, popularly known as the Clean Water Act, which established national standards for sewage treatment and significantly increased federal funding to help communities meet the laws. The Clean Water Act established the National Pollutant Discharge Elimination System (NPDES) permit program, which controls water pollution by regulating point sources that discharge pollutants into waters of the United States and setting discharge limits to protect waterways and improve water quality.

Wastewater treatment plants typically require major updating every 15-20 years in order to stay in compliance with DEQ requirements. WWTP1 was upgraded again in 1990, including building a new primary treatment area and secondary clarifier, remodeling the maintenance building, and updates to the aeration basins, digesters, grit system, headworks system, chlorine contact basin conversion, outfall repair, and a large electrical upgrade to the plant. In the planning of this upgrade, consideration was given for future upgrades so there was space intentionally left open for future needs of the treatment system.

WWTP1 is undergoing an upgrade; construction began in 2023 and will take three years.

Wastewater Treatment Plant 2

WWTP2 is located in Empire off of Empire Blvd/Cape Arago Highway. The original WWTP2 was constructed in 1964 and upgraded in 1990. By 2012, the City determined that the existing plant did not have the capacity to handle increased flows and newer EPA/DEQ requirements and that a new wastewater treatment plant was needed. Construction on a new wastewater treatment plant, located across the street from the original one, broke ground in 2016. This treatment plant is a Sequencing Batch Reactor (SBR) plant was fully operational in 2020. Solids from WWTP2 are transferred to WWTP1 through the collection system. 

Post-Plant Treatment

The solids are treated at WWTP1 using anaerobic digesters to make the product safe for disposal. Once fully treated, the resulting sludge is sent to the four acre lagoon in Eastside where the material is separated, resulting in Class B Biosolids.

Biosolids contain organic matter and are nutrient-rich, so can be used as a soil amendment or fertilizer and a sustainable alternative to commonly used chemical fertilizers. Nutrients such as nitrogen, phosphorus, sulfur, zinc, calcium, magnesium, and iron are present in most biosolids. Biosolids are applied at agronomic rates that benefit soil quality and the growth of crops. Biosolids can also be used for enhancing vegetative growth on reclamation sites and the US Department of Agriculture Conservation Reserve Program lands at greater than agronomic rates. These sites are reviewed on a case-by-case basis and appropriate agronomic rates are determined. Properly applied, they improve soil structure and water-holding capacity, which improves growing conditions for crops, forests, landscaping, lawns, and vegetation on reclaimed lands.

Each summer, the City hauls these Class B Biosolids onto DEQ-approved land sites throughout the county. The City tests the biosolids and the land prior to application and utilizes DEQ/EPA directives and regulations for tracking application rates, with annual reports of testing and program processes submitted to DEQ and EPA.