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~ ~ ~ MONITORING __LVERIFICATION ~ IDENTIFIED IMPACT RELATED MITIGATION MEASURE Implementation Monitoring and , Timing Signature ~ Date of dry weather capacity. The estimated Maximum intensity alternative-related ADDWF increment of 630,885 gpd {0.631 mgd) is less than the City's purchase option of 1.915 mgd. In recent years, wastewater flow into the SBSA collection system from Redwood City has occasionally exceeded the current peak wet weather flow capacty right (exclusive of Redwood Shores) of 25.9 mgd. Since 1994- 95, the City has exceeded its allocated capaary nine times during the winter. Since the SBSA treatment capacity allocation to Redwood City is already being exceeded during wet weather, the current allocation from the SBSA is inadequate to serve the projected Maximum Intensity alternative ADDWF increment in addition to existing SBSA commitments. Because the SBSA treatment capacity allocation to Radwood City is already being exceeded, the Precise Pian Maximum intensity alternative-related and cumulative impacts on wet weather flaw treatment capacity are considered to represent a potentially significant pr®ject and cumulative impact. Impact 10-2: Precise Plan-Related and Cumulative Impacts on Wastewater Treatment and Transmission Capacity- Moderate Intensity Alternative. Preliminary estimates indicate that the Moderate intensity Precise Plan alkernatve could generate a total of approximately 507,475 gallons of average daily drv weather Flow (ADDWF) per transmission capacity improvement options listed below, tl~e procedural details of which shall be included in either a project memorandum or development agreement for each project, at the discretion of the City Engineer. In order to mitigate the limited transmission capacity during wet weather from the Precise Plan area fo the SBSA treatment plant, implementation of one of the following options would be necessary: (1) Upgrade the influent sifting station at the treatment plant, upgrade the treatment plant itself as necessary, inshail a new gravity sewer line from the SBSA pump station at Maple Street, and upgrade the pump station at Maple Street; or {2) Replace 21,000 feet of 6-inch, 3,600 feet of 8-inch, and 2,000 feet of 10-inch pipes within the Precise Plan areal, and 24,500 feet of 6-inch pipes outside the Pian area, to reduce the wet weather flows. By replacing existing wastewater collection pipes, and thus reducing infiltration and inflow, the increase in ADDWF from Precise Plan-related growth would be mitigated, and the wet weather flew would not increase from Plan-facilifated development. An additional benefit would be the replacement of all substandard 6- inch pipes with City standard 8-inch pipes. Implementation of this measure would reduce Precise Plan Maximum Intensity alternative and cumulative impacts on wastewater treatment and transmission capacity to aless-than-significant level. Mitigation 10-2. If the Precise Plan Moderate Intensity alternative is adopted, prior to City approval of any individual development proposal in tha Precise Plan area, if determined necessary by the City Engineer, the City shall purchase from the SBSA the added treatment capacity necessary to accommodate the projected net increase in wastewater generated by City; fair-share reimbursement from future individual project applicants. City I Condition of occupancy permit issuance ~~ Page ZO U:fMy Documentsi.Dawrfovm Precise PIanICC staff reporfs!CC 3. f 2.doci3. f 2.07 ExhrbitstA'tachment A mif.monitoring checklist fi55.docW D