King County's Compliance with EPA's Nine Minimum Controls |
Nine Minimum Controls |
King County Compliance Controls |
1. Proper operation and regular maintenance programs for the sewer system and CSOs |
Proper facility operation is managed by West Point staff using SCADA Asset management programs implemented by the West Point Treatment Plant, South Treatment Plant, and collection system maintenance division maintain CSO outfalls, regulator stations, and pump stations. 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 on request. |
2. Maximize use of collection system for storage |
The Regional Wastewater Services Plan emphasizes storage projects for CSO control. SCADA manages regulator stations to maximize flows in interceptors and to store excess flows in large trunk sewers. |
3. Review and modification of pretreatment requirements to ensure that CSO impacts are minimized |
King Countys Industrial Waste Program issues approvals that set limits on the chemical contents of industrial discharges. The program includes monitoring and permit enforcement, education, and technical assistance to businesses on appropriate waste pretreatment and disposal techniques. WTD also administers and helps fund the Local Hazardous Waste Management Program. Current water quality assessment and sediment management plan data indicate that there is no need for a CSO-specific pretreatment program. |
4. Maximization of flow to secondary treatment plant for treatment |
SCADA is used to maximize flow to the West Point Treatment Plant via operation of regulator and pump stations. All analysis for CSO control project alternatives include storage and transfer to the secondary and CSO treatment plants. |
5. Elimination of CSOs during dry weather |
King County CSOs do not occur as a result of inadequate dry-weather flow capacity. The county provides enough capacity in the combined sewer system to transfer 2.25 times the average wet-weather flow to secondary treatment, as negotiated with Ecology. The only overflows seen in the combined system during dry weather result from problems such as power outages, mechanical failures, or human error. These events are rare and are immediately reported to Ecology. (Table 5 lists dry-weather overflows that occurred during the 2007–2008 season. Refer to 2007-2008 Annual Report.) Overflows occurring during precipitation (CSOs) can be exacerbated by power outages, mechanical failures, or human error. Such overflows in 2007-2008 are listed in Table 7. (Refer to 2007-2008 Annual Report.) Operation and maintenance 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. |
6. Control of solid and floatable materials in CSOs |
The City of Seattle's catch basin maintenance program limits the introduction of floatable materials to sewers. King County 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." 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 also hold back solids and floatables in the conveyance system prior to overflow. Observations of the quantity of floatables are noted in logs at each facility and are available for inspection on request. These observations have indicated that additional floatables and solids controls are not needed at this time. If additional floatables control is found to be needed in the future, the needs will be addressed in the CSO control projects implemented under the county's long-term control plan. |
7. Pollution prevention programs to reduce contaminants in CSOs |
King County has implemented the Industrial Waste Program and has been a major participant in the Local Hazardous Waste Management Program. Both programs serve to reduce discharge to sewers of chemicals and other substances that adversely impact the environment and the wastewater treatment process. Educational materials on controlling trash disposal to sewers are a part of the larger public information program. |
8. 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 the posting of signs at publicly accessible CSO locations, an information phone line, a Web site, a 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 to Ecology on July 1, 2007. The study reviewed and recommitted to continuing the public notification program elements described above. It also identified the potential to provide real-time notification of overflows. A Web site that provides this notification went live December 2007. The county is seeking public opinion on the usefulness of the Web site's approach and format as a part of its outreach programs. It is also investigating automated email as another notification method, but it is not ready for external use yet. |
9. Monitoring to effectively characterize CSO impacts and the efficacy of CSO controls |
In 1986, King County began a sampling program to characterize each CSO and identify high priority sites for early control. The program included collecting water quality data for five CSO sites per year and collecting sediment samples at each site. In the 1990s, sampling was expanded to assess compliance with state Sediment Management Standards. The county's extensive monitoring for its 1999 CSO Water Quality Assessment of the Duwamish River and Elliott Bay 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. Monitoring of CSO volume and frequency will continue after completion of CSO control 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. |
