Alameda County denies Zone 7 appeal, approves 190-unit Arroyo Lago subdivision

Alameda County supervisors on Feb. 10 voted to deny an appeal from Zone 7 Water Agency and approved the Arroyo Lago subdivision, a 190-unit project on a 26.6-acre site in unincorporated Alameda County.

Planning staff recommended upholding the planning commission's approval and certifying the final environmental impact report (EIR). "Planning staff recommends that the board of supervisors deny the appeal, certify the EIR and approve the vesting tentative track map," county planning staff said during the hearing, summarizing its conclusion that the administrative record contains substantial evidence supporting the commission's decision.

Why it matters: Zone 7, the groundwater sustainability agency for the Livermore basin, argued the proposed on-site membrane bioreactor (MBR) wastewater treatment plant and nearby agricultural spray fields could threaten Lake I, Cope Lake and municipal supply wells, and pressed the county to require annexation to the City of Pleasanton so the development could tie into city sewer.

In a presentation, Colleen Weine of Zone 7 said the agency's concern is protecting the groundwater basin from contamination and long-term risks associated with wastewater effluent and PFAS. "Our concern is for protecting the groundwater basin, protecting the water resources, from contamination," she said, noting Zone 7 operates monitoring wells in the basin and manages Lake I and Cope Lake.

County staff and the project's technical team countered that the project's EIR and permit conditions address the concerns: the EIR includes hydrology and water-supply analyses, the applicant proposed design changes (including moving spray fields under condition 71) and MBR treatment is widely used with state oversight. The applicant's representative said the facility "is not gonna contaminate the water," adding state and regional regulators (State Water Board and the Regional Water Quality Control Board) would license and oversee operations.

The EIR concluded that most issues are mitigated to less-than-significant levels but identified unavoidable transportation and greenhouse-gas impacts tied to vehicle miles traveled. Staff noted the Housing Accountability Act (HAA) limits the number of hearings and the county is required to make findings consistent with the statute.

Vote and outcome: The board adopted staff's recommendation. A roll-call vote recorded four ayes and one abstention; the motion carried and the board certified the EIR, adopted findings of fact and the statement of overriding considerations, and approved the vesting tentative tract map (TR 8423).

What happens next: Staff said the project is expected to pursue annexation into the City of Pleasanton, which would connect the site to municipal services; the city has taken several steps and the applicant has indicated it prefers annexation. If annexation occurs, some mitigation and service issues would be handled by the city; if not, the privately operated MBR facility would proceed under state permitting and monitoring.

Reported voices: Planning staff (Alameda County), Zone 7 Water Agency, the applicant and environmental consultants.