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Neighbors press council on stormwater and landslide risk as engineers describe cistern and OWTS design
Summary
Residents at the public hearing argued the project could worsen landslide and drainage problems; the applicant's geotechnical and civil engineers described a detention/retention system and a subsurface drip OWTS they say will reduce off‑site peak flows and avoid injection into deep ground.
During a lengthy public hearing on the Crest Road project, multiple residents urged the council to delay approval until the stormwater and landslide questions were resolved. A neighbor who spoke at length asked who would decide the CEQA exemption and whether up to 16,000 cubic yards (as suggested in comments) of export and new impermeable surfaces could produce significant downstream impacts.
Project geotechnical consultant David Hamilton said the team recommended a surficial evapotranspiration/subsurface‑drip system rather than a traditional deep leach field because of hillside stability concerns. "4 to 1 means about 4 feet horizontal to every 1 foot down," Hamilton said when explaining the shallower slope needed for the OWTS dispersal area. Civil engineer Kevin Poffenberger told the council the team performed infiltration testing and soil analyses for county review and expects county approval at plan check.
Engineers also laid out a stormwater detention and reuse strategy. The project design includes two 40,000‑gallon cisterns (80,000 gallons total) to detain runoff and to supply irrigation reuse, which the team said should reduce peak off‑site flows. Council members probed whether tanks filled in large storms would be usable for irrigation in the wet season and whether multiple storm events could exceed detention capacity; engineers said modeling and county methods would guide operational details.
The applicant also offered to move a riprap discharge point further down the canyon if feasible to reduce the likelihood that local infiltration points would be overloaded. City staff noted that county approvals and plan‑check are required for engineering sign‑offs and that any on‑city use of exported material would require additional approvals.
