Programs to Meet EPA's Nine Minimum Controls

CSO Control Program--
  CSO Reduction over Time
  Project Phasing
  Project Status
  EPA's Nine Minimum Controls
  Ongoing Program Elements

Nine Minimum Controls

King County Compliance Controls

Proper operation and
regular maintenance
programs for the sewer
system and CSOs

King County regularly maintains CSO outfalls, regulator stations, and pump stations through the asset management programs managed by West Point Treatment Plant, South Treatment Plant, and collection system maintenance divisions. Proper facility operation is managed by West Point staff using SCADA. Collection system staff inspect sewers on a specified schedule and perform corrective actions when deficiencies are found. Maintenance schedules and records of visits are available for inspection upon request.

Maximize use of collection system for storage

SCADA manages regulator stations to maximize flows in interceptors and to store excess flows in large trunk sewers. The RWSP emphasizes storage projects for CSO Control.

Review and modification of pretreatment requirements to ensure that CSO impacts are minimized

King County's Industrial Waste Program issues permits that set limits on the chemical contents of industrial discharges. The program also includes monitoring and permit enforcement, education, and technical assistance to businesses on appropriate waste pretreatment and disposal techniques. King County also helps fund the Local Hazardous Waste Management Program. Current water quality assessment and sediment management plan data indicate that there is no need for CSO-specific pretreatment program modifications.

Maximization of flow to secondary treatment plant for treatment

SCADA is used to maximize flow to the West Point Treatment Plant by operation of regulator and pump stations. All analysis for CSO control project alternatives include varying levels of storage and transfer to the secondary and CSO treatment plants.

Elimination of CSOs during dry weather

King County CSOs do not occur as a result of inadequate dry-weather flow capacity. King County provides capacity to transfer 2.25 times average wet-weather flow to secondary treatment, as negotiated with Ecology. The only overflows seen in the combined system during dry weather result from power outages, mechanical failures, or human error. These events are rare and are immediately reported to Ecology. A list of dry weather overflows that occurred during the 2006-07 season can be found in Table 5 (refer to section 2 of Annual Report, .PDF file, 1.1MB).

Overflows occurring during precipitation (CSOs) can also be exacerbated by power outages, mechanical failures, or human error. Such overflows in 2006-07 are listed in Table 7 (refer to section 2 of Annual Report, .PDF file, 1.1MB).

Maintenance and operation programs, as described for the first control, focus on preventing dry-weather overflows and exacerbated CSOs. The conveyance system is monitored through SCADA and direct observation; corrective action is taken immediately if a problem occurs. Equipment problems are immediately reviewed, and repair or replacement activity is undertaken in a timely manner.

Control of solid and floatable materials in CSOs

City of Seattle catch basin maintenance limits introduction of floatable materials to sewers. The County also developed an information campaign with brochures and TV spots to educate the public that trash should not be flushed to the sewers. Information is available on the CSO control website under “Resources and Links” at http://dnr.metrokc.gov/WTD/cso/library.htm

The majority of floatables in the King County system are captured in the large volume of wastewater transferred to the treatment plant before overflows occur. Overflow weirs in the system also hold back solids and floatables in the conveyance system prior to overflow. Observations of quantity of floatables are noted in logs at each facility and are available for inspection on request. These observations have not shown that additional measures to control floatables and solids are needed at this time. Any additional floatables control found to be needed will be addressed in the CSO control projects implemented under the County’s long-term control plan.

Pollution prevention programs to reduce contaminants in CSOs

King County has implemented both the Industrial Waste Program and has been a major participant in the Local Hazardous Waste Management Program to reduce discharge of chemicals and other substances that adversely impact the environment and the wastewater treatment process. Educational materials on controlling trash disposal in the sewer are a part of the larger public information program.

Public notification program to ensure that public receives adequate notice of CSO events and impacts

King County operates a CSO Notification and Posting Program as a joint project with the City of Seattle and Public Health–Seattle & King County. This program includes posting signs at publicly accessible CSO locations and an information phone line, Web site, brochure, and other public outreach activities. A Public Notification Feasibility Study, required in the most recent modification of the West Point NPDES permit, was submitted July 1, 2007. The study identified the potential to provide realtime notification of overflows on a Web site. This site is being piloted, while the County continues to seek public opinion on the usefulness of the Web site approach and format. The study reviewed and recommitted to continuing the other public notification program elements described above.

Monitoring to effectively characterize CSO impacts and the efficacy of CSO controls

Beginning in 1986, King County's sampling program was designed to characterize each CSO and identify any high priority sites for early control. That sampling included collecting overflow quality data for five CSO sites per year, and sediment sampling representative of more industrial sites. Sampling was expanded to meet Sediment Management Standards' needs in the 1990s. This characterization was completed.

King County’s extensive monitoring for its 1999 CSO Water Quality Assessment found that the majority of risks to people, wildlife, and aquatic life would not be reduced by removal of CSOs because most risk-related chemicals come from sources other than CSOs. Overflow volume and frequency monitoring will continue after completion of projects to verify achievement of control goals. King County may undertake additional sampling on completion of specific CSO control projects where it is deemed useful to verify project effectiveness. Such monitoring plans will be developed during project implementation as needed.

The Supervisory Control and Data Acquisition (SCADA) system controls the West Point Treatment Plant collection system.