2014-069 - Final Environmental Impact Report No. 2014-01

Home Browse Search

HARBOR BLVD. MIXED USE TRANSIT CORRIDOR PLAN FINAL FIR CITY OF SANTA ANA 5. Environmental Analysis HYDROLOGY AND WATER QUALITY Adherence to the BMPs in the WQMP would reduce, prevent, minimize, and /or treat pollutants and prevent degradation of downstream receiving waters. BMPs identified in the WQMP would reduce or avoid contamination of stormwater with sediment and would also reduce or avoid contamination with other pollutants such as pathogens, heavy metals, nutrients, organic compounds, and sediment toxicity. Therefore, water quality and waste discharge impacts from operation activities associated with individual development projects that would be accommodated by the Harbor Corridor Plan would not occur. Impact 5.7 -6: Development of projects pursuant to the Harbor Corridor Plan would place people and structures in a 100 -year flood zone. [Thresholds HYD -7 and HYD -8] Impact Analysis: Buildout of the proposed Harbor Corridor Plan would increase numbers of residents, residential units, commercial square footage, and employees in the project area. Much of the northern half of the project area is a 100 -year flood zone, as shown in Figure 5.7 -4, Flood Zones. Areas along the west side of Harbor Boulevard from 1st Street north to 5th Street are in Zone A, as are areas along both sides of Harbor Boulevard from 5th Street north to Westminster Avenue. However, multiple flood control improvements have been completed, are under construction, or are planned, as part of the Santa Ana River Mainstem Project ( SARMP) described above in the Seismically Induced Dam Inundation discussion of Section 5.7 -1, Envimnmental Setting. The flood insurance rate maps (PTRMs) for the project area were issued in 2009. The SARMP is scheduled for completion in 2018; some elements of which, including Seven Oaks Dam, have already been completed. At completion of the SARMP, 100 year flood zones for flooding from the Santa Ana River are expected to be substantially smaller than they are at present. For example, channel improvements are underway on a segment of the East Garden Grove- Wintersburg Channel between Warner Avenue and Bolsa Bay, downstream from the project area in the City of Huntington Beach, and an area of unincorporated Orange County (OC Public Works 2013). At completion of improvements under construction and planned along the Santa Ana River and the East Garden Grove - Wintersburg Channel, it is expected that flood hazards in the project area would be reduced compared to flood zones designated in the 2009 FIRMS. Prior to completion of the SARMP improvements, impacts would be significant. Hydrology studies for individual development projects that would be accommodated by the Harbor Corridor Plan would be required; the studies would have to include estimates of 100 -year flood depth on each respective site from FEMA. Geotechnical investigations for each such project would also be required to provide recommendations for grading to raise building pads above 100 -year flood elevations, as required. Alternatively, individual development projects could request a Letter of Map Correction from FEMA if the respective project applicants provide substantial evidence that the lowest adjacent grade elevation is already above the 100 -year flood elevation at that site. Page 5.7 -26 PlaceWorkr