By B. R. Bradley, PE and S. Braband
Like many mobile home parks, the Paradise Cove Trailer Park began as a getaway RV park located in a picturesque location by the sea. As it’s popularity grew, the park grew into a large mobile home park, outgrowing its wastewater infrastructure. With only septic tanks and seepage pits, the Owner resorted to frequent pumping, shifting sewage from one cluster of pits to another. Finally the Owner bought a pumper truck to handle the cost of transferring water out of failed seepage pits clusters on a daily basis. At that point, the Regional Water Quality Control Board stepped in with Waste Discharge Requirements and a schedule for repairs. The Owner agreed to upgrade collection, treatment, and disposal to substantially improve the system’s performance and reliability. The resulting system will collect wastewater from the 257 mobile homes using a cluster approach. The park flow of 40,000 gpd with peaks of 60,000 gpd will be collected by gravity sewers draining to septic tanks with effluent screens. Multiple tanks will drain to lift stations to pump the water in small-diameter pressure sewers to a centrally-located treatment facility site in a discrete area of the park. Wastewater treated in twenty AX100 textile filters will achieve an advanced secondary level. Disinfection using a redundant UV-ozonation system will match municipal requirements for disinfection. From a dosing tank, the disinfected effluent is redistributed throughout a 20-acre area and dispersed in subsurface drip fields and seepage pit clusters. Key issues associated with the project were the task of navigating through multiple agencies to obtain a permit; identifying a suitable and reliable disinfection system; specifying automatic controls for a system with a large number of distributed components. One of the Owner’s goals was to obtain incidental irrigation from the highly treated effluent, but regulations were seemingly conflicting or absent. This project is one case where a permit for a repair allowed multiple objectives to be met: (1) progress in onsite system technology, (2) incidental irrigation benefits in a water-poor state, and (3) preservation of public health. Incidental irrigation benefits were the vulnerable to prohibition, depending on interpretation where regulations are unclear. Standards for subsurface water recycling are needed to accommodate the agencies’ concerns while maintaining the affordability of the system.