Agenda - 01-04-1988 - Laserfiche WebLink

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From this analysis, it appears that the proposed hydraulic and pollutant 057 loading rate may be too high for the proposed absorption field area, given the concern for long-term protection of the quality of surface water and groundwater supplies. This concern is heightened by the fact that soils are only marginally suitable for wastewater disposal and the proposed nitrification field is located near a natural drainage channel. 3. The proposal to reserve a backup soil absorption area equal in size to the initially installed absorption field provides only an "after-the fact" approach to correcting future wastewater disposal problems. Under that approach, if a failure of the primary system occurred it would continue while the replacement system was being installed in the backup field. A greater degree of reliability and operational flexibility should be incorporated into this community system since a failure of the system would create a greater problem than failure of a single septic tank. To provide added assurance that the system will have a long, useful life, the primary soil absorption area should be periodically rested. This will allow the absorption field to gradually drain, thereby exposing the infiltrative surfaces to the air allowing bacteria to restore the field's infiltration capability. Periodic resting requires that a second absorption field exist to allow continued disposal while the first is in the recuperative phase. The systems can be alternated on a yearly basis (Reference 41) . This approach is required in Fairfax County, Virginia and other areas. OWASA recommends that at a minimum a dual, alternating absorption field system be required to be installed and utilized for this project. Additionally, the need for reserving an undisturbed backup area should be considered in the event either of the dual absorption areas fails. The combination of a lower hydraulic loading rate and redundant absorption facilities, together with a good maintenance and operation program should provide substantially greater reliability of the community waste disposal system functioning adequately and properly. As recommended in the literature, this conservative approach is justified "because (1) it is more difficult to achieve even distribution of effluent in large systems, thus making localized overloading more likely, (2) groundwater mounding may be a problem with these large systems, and (3) surface failures of these systems may present larger environmental and health consequences because of their size." (Reference 44) 4. Adequate measures must be taken to prevent the accidental discharge of wastewater from the proposed facilities into surface and ground waters. It is recommended that: a. A reserve storage tank be constructed to store the volume of wastewater which would be generated during a 24-hour peak day period. That would provide backup storage in the event a pump station failure occurred; b. The pump station must be capable of handling peak hour flows with the largest pump out of service; and c. Emergency standby power and alarm systems be installed at the pump station. -3-