No agencies have evaluated or conducted cumulative impacts on groundwater in Fall City.
Concern for cumulative impacts
These projects propose placing 8 homeowner managed large onsite septic systems in a type 1 and 2 CARA (critical aquifer recharge area - meaning there vulnerable soils near a drinking water supply) for 150 homes in a ¼ mile area, within wellhead protection areas.
Experts are concerned that the overall hydraulic loading of area soils due to the increased density of the areas are adjacent to community wells. Surpassing the hydraulic loading capacity of the soils can lead to large scale soil clogging, inadequate effluent treatment, and drainage problems. How much is too much? We have no idea. The loading scenarios and analysis have not been completed by any agency and cumulative impacts are unknown.
Fall City has a vulnerable water supply with outdated wellhead protections, an unconfined aquifer punctured by old wells and riddled with type 1 soils (gravel), unlined wells that sit within a shallow aquitard, and no modern monitoring or alarms for contamination events.
These LOSS designs, and the applicant, are problematic in operation and have a precedent of failing to meet treatment requirements or follow best practices (exceeding the number of bedrooms) for engineering and successful homeowner operation.
The scale, homeowner management and siting of the LOSSs has no referenceable precedent, locally or nationally, and the environmental impacts and risks to groundwater are unknown. The community has concerns about HOA managed systems, the ongoing support required from a public utility and the ability of the State DOH to continue to manage these systems.
All agencies involved have stated concern and cite a lack of data or precedent to allow them to address cumulative impacts. Our water district commissioners are requesting both the county and state to help them determine the risks to groundwater. WSDOH is requiring each plat to conduct some hydrogeological studies, but they are not requiring a comprehensive analysis.
King County is the lead agency and has declined to conduct a cumulative impacts SEPA review for unknown reasons.
Can the applications be complete if King County DNRP has not reviewed the cumulative impacts for ground water quality or quantity, as required by the King County Comprehensive Plan at F-237:
Under King County Code chapter 9.14, the Department of Natural Resources and Parks is to act as lead agency in coordinating the activities of Department of Permitting and Environmental Review and Public Health – Seattle & King County in order to ensure that groundwater quality and quantity are protected, and facilitate implementation of the plans that have been developed to protect groundwater in five groundwater management areas within King County.
The 8 projects with 150 homes are within a 1/4 mile area and located within a wellhead protection area and critical aquifer recharge area.
The shared community drain fields have a poor track record for meeting required treatment levels and having chronic malfunctions. But more importantly, the additional injection of waste water into vulnerable soils could affect the way water moves underground or hydraulically overload the system, leading to failure events. Fall City already exceeds recommendations for septic systems.
Within 2500 feet of the primary wells, the proposed LOSSs place increasing amounts of pressure on the aquifer and soils.
The recommended number of septics by King County for a CARA is 1 per acre. Fall City averages 4 per acre closest to the wells. The addition of the Taylor plats increases the total loading of soils within the area significantly.