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could occur up to 8.3 feet outboard of the outer building pad slope by the year 2045, leaving at least approximately 1.2 feet of free -board above the flood level . The Drainage Plan and mitigation measures described in the Phase I and I PDP EIR are designed to handle increases in runoff on -site. During a 15-year storm event, the internal project drainage system would be adequate to handle flows within the site. The project has also allowed for an alternative drainage system to be used in the event of pump failure. The Alameda County Public Works Agency intends, by agreement with the City and Citation Homes, to accept operation and maintenance of the Roberts Landing Pump Station and Stormwater Quality Control Pond. In addition, GDP EIR Mitigation Measures 3.2.1, 3.2.3, 3.2.4 and 3.2.5 include measures to reduce impermeable surfaces, by using natural surfaces for paths and permeable pavements for driveways, and to reduce flood potential by minimum floor elevation requirements. These measures have been incorporated into the PDP designs for Phases 2A, 213, and 3. The incorporation of all of these drainage control facilities and measures and the design building pad elevation would reduce any impacts associated with increased flood potential on- or off -site to below a level of significance. A.2 POTENTIAL IMPACT: Water quality in the adjacent wetlands may be negatively affected by the movement of unknown toxic contaminants in runoff from the project area. FINDING: Changes or alterations have been required in, or incorporated into, the project that avoid or substantially lessen the potential significant environmental affect on water quality from potential toxic contaminants. STATEMENT OF FACTS: Potential contaminant sources in urban stormwater runoff from Phases 2A, 2B and 3 would be routed to on -site detention ponds (in Phase 1 B) designed for a 40-hour drawdown period. The temporary stormwater pond runoff would be directed toward the southeast portion of the site to a pump station, which would pump the water into San Lorenzo Creek. The proposed PDP would be graded so that all drainage in Phases 2A, 2B and 3, as well as in Phases I and 1B, would be collected into a gravity -driven storm drain system and directed toward the appropriate detention basin and then towards the pump station. Therefore, potential effects on the adjacent wetlands from contaminated runoff would be minimal. Mitigation Measures A.4 through A.8 in the Phase 1 A and 1 B SEIR include monitoring and maintenance requirements for water quality in the detention pond. These measures specifically include monthly monitoring of water quality in the detention ponds, the use of best management practices to achieve NPDES permit standards, sediment removal activities and the use of vegetation to "naturally" remove dissolved contaminants. Although some hazardous material contaminants may remain on the site at low concentrations after remediation is complete, the probability that these contaminants would move into the adjacent wetlands and San Francisco Bay is small. The contaminants on the site are bound up in the soil particles and are not readily soluble 3