Ashland Wastewater Treatment Plant Upgrade

City of Ashland, 

Ashland Wastewater Treatment Plant Upgrade

Project Highlights: 
  • Highest quality effluent of any wastewater facility in the Northwest.
  • Full year-round nitrification.
  • Phosphorus removal using membrane filtration to remove alum floc.
  • UV disinfection. Amended design concept, saving Ashland approximately $8 million.
The Ashland Wastewater Treatment Plant
The Ashland Wastewater Treatment Plant produces the highest quality effluent anywhere in the Northwest.

Carollo has provided predesign, final design, and construction management for the City of Ashland’s Wastewater Treatment Plant Upgrade Project. Ashland originally master planned the improvements as a threephase, seven-year project with a total cost of $27.1 million. The project addresses the immediate needs of the plant, regulatory compliance to meet total maximum daily loads (TMDL) limits, and community growth.

During predesign, Carollo was able to identify changes to the original project that reduced the construction cost by approximately $8 million. Realizing these savings involved changing the treatment process to an extended air process using an oxidation ditch. In addition to its lower cost, operations staff preferred the oxidation ditch concept because of its reduced operations and maintenance (O&M) requirements. Based on the outcome of this predesign effort, Carollo amended the City’s facility plan to include a two-phased approach which incorporated more cost-effective treatment technologies and accelerated the construction schedule. The Oregon Department of Environmental Quality reviewed and accepted this amendment.

Treatment plant improvements include rehabilitation of the existing headworks to improve screening and solids handling, odor control improvements, and electrical upgrades. Work also included rehabilitating the existing secondary clarifiers with new collector mechanisms, constructing an additional 80-foot-diameter clarifier, adding a new return sludge pump station with waste sludge pumping, and installing a new ultraviolet (UV) disinfection system to eliminate the use of chlorine gas.

Additional services include:

  • Design of a tertiary treatment plant for phosphorus removal. The plant will use immersed membranes for filtration of secondary effluent to remove alum-flocculated phosphorus. The tertiary plant will be on-line in the summer of 2002.
  • Design of a sludge stabilization and dewatering facility. Lime stabilized sludge will be treated to Class B standards and dewatered using centrifuges.
  • Public involvement assistance including meetings with the City Council and neighborhood groups, and interface with special interest groups.
  • Permitting assistance.
  • Full-time, onsite construction management and inspection.
  • Startup, testing, training, and O&M manual preparation.


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