On-Site Sewage Disposal Source Control Strategies

Failing on-site sewage disposal systems can add nutrients, toxic chemicals and disease-causing bacteria and viruses to fresh and salt water. To prevent failure, on-site sewage disposal systems must be properly maintained. Proper maintenance includes repairing failing systems, regular periodic pumping and inspection of the septic tank, checking liquid levels in the drain fields, adjusting and replacing mechanical systems, controlling waste loading to the system, and protecting the drainfield or absorption area.

Commercial systems are of special concern because of their potential for allowing toxic materials to enter the system. In addition, many businesses change or expand operations without considering the design of their septic systems. The resulting waste loading may exceed the capacity of the system.

Unsuitable soil types and special hydrologic conditions limit the effectiveness of on-site sewage disposal systems in many parts of the Chehalis River Basin. More than 81% of the basin is classified as having severe to very severe limitations on septic tank operations.

Many households in the Chehalis River Basin currently use on-site sewage disposal systems. High concentrations of these are in semi-urbanized areas near the larger basin communities; Aberdeen, Hoquiam, Centralia, and Chehalis. Failing systems are distributed throughout the entire Chehalis River Basin.

Areas with severe water quality problems resulting from failing on-site sewage disposal systems include:

• A. - Ford's and Waunch Prairies - Centralia area (Morris, 1988)
• B. - Jackson Highway/Wallace Road/Logan Hill - Chehalis area (Morris, 1988)
• C. - Grand Mound-Rochester area (TCPWD, 1987)
• D. - Central Park - between Montesano and Aberdeen (GHRPC, 1991)
• E. - Black Lake and Scott Lake areas (Beck, 1975)
• F. - Bucoda and Tenino communities (Beck, 1975)

Public education on proper operation and maintenance of septic systems is especially important in urbanizing areas, because many people moving into these areas are unfamiliar with on-site sewage disposal. Public education efforts are also needed to reach many homeowners who have older systems.

On-Site Sewage Disposal Goals

Significantly reduce or eliminate adverse impacts of nonpoint source pollution from on-site sewage disposal in the Chehalis River Basin.

Improve the design, operation and maintenance of on-site sewage disposal systems in the basin.

Promote adequate plan review, inspections, enforcement of existing on-site sewage disposal regulations, and development of new regulations where needed.

On-Site Sewage Disposal Recommendations

Issue: - Failing on-site sewage disposal systems must be identified and repaired or eliminated.

• 1. - County and state health departments should inspect all commercial on-site sewage systems periodically to ensure that design standards are not exceeded and toxic materials are not discharged. City utilities should report known failing on-site systems within their service area to the county health districts.
  
• 2. - A renewable permit program for all commercial, residential and non-standard septic systems should be explored as a funding source for increased efforts at conducting inventories and inspections. Health districts should develop programs to require inspection of all on-site sewage disposal systems on a maximum five-year permit basis.
  
• 3. - The formation of utility local improvement districts (ULIDs) and development of new technologies and alternative methods of treatment should be encouraged in areas that have a high number of failing systems.
  

Issue: - Public education about on-site sewage disposal systems is crucial. Contamination from failing systems is often a hidden source of water pollution since septic drainfields lie underground. Systems can fail for years with no obvious signs of failure.

• 4. - Current public education efforts dealing with the proper maintenance and operation of on-site sewage systems should be continued and expanded. All buyers of homes with on-site sewage disposal systems should be provided with information about the design and capacity of their systems and proper maintenance techniques including waste water reduction, handling of hazardous products, and appropriate scheduling of inspections and pumpouts.
  
• 5. - Educational materials specifically designed for commercial on-site sewage systems should be developed and distributed.
  
• 6. - Areas where densities approach one acre per dwelling, that have a high number of failing systems, and are not served by sewers should be targeted for increased public education efforts to improve operation and maintenance of on-site systems.
  

Issue: - Areas with high densities of failed on-site sewage disposal systems need to identified and the problems addressed before ground water aquifers and surface waterbodies are severely impaired. New on-site sewage disposal systems should be designed, installed and maintained under strict guidelines to protect surface and ground water quality from contamination.

• 7. - County health districts should continue to identify areas that have high failure rates. Identified areas should be surveyed and monitored, and solutions developed to resolve the problems (in a manner similar to that of the Ford's and Waunch Prairie project in and near Centralia).
  
• 8. - Homes with on-site sewage disposal systems in areas where sanitary sewer service is available should be strongly encouraged to connect to the sewer. Failing septic systems in these areas should not be replaced; properties should connect to the sanitary sewer system.
  
• 9. - County health districts should require that all failing systems receive the best practicable repair. Repairs in areas of marginally permeable or impermeable soils should include low-flow plumbing fixtures. Water conservation training and education should be encouraged.
  
• 10. - When septic tanks or other on-site treatment facilities are installed, the local health district should make an inspection similar to a building inspection.