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Title:	Integrated Feasibility Report and Environmental Impact Statement/Environmental Impact Report for Westminster, East Garden Grove, CA, Flood Risk Management Study
Authors:	Orange County (Calif.). Public Works United States. Army. Corps of Engineers. Chicago District
Keywords:	Floods Flood control Environmental protection Environmental management Orange County (Calif.)
Publisher:	United States. Army. Corps of Engineers. Chicago District.
Abstract:	This IFR includes an analysis of opportunities to address flood risk to the residents of the communities in the Westminster watershed. The report includes an analysis of three alternatives, including the No Action Alternative, to determine which plan or plans would merit further consideration for federal and local participation. The documentation also includes an analysis of the impacts of each alternative on existing resources within the watershed. The alternatives were developed to a level of detail sufficient to identify a National Economic Development (NED) Plan, as well as a Locally Preferred Plan (LPP). Additional detailed design, cost estimating, and impacts assessment may be completed, as required for the NED Plan and the LPP. Each of the alternatives, including the NED and the LPP were formulated to be complete, effective, efficient and acceptable. Further, both the NED and the LPP have a benefit to cost ratio (BCR) greater than 1.0 at the current federal discount rate (2.75%). The study and project area is located within the Westminster watershed in western Orange County, California, approximately 25 miles southeast of the City of Los Angeles. The watershed is approximately 87 square miles in area and is almost entirely urbanized. Cities in the watershed include Anaheim, Stanton, Cypress, Garden Grove, Westminster, Fountain Valley, Los Alamitos, Seal Beach, and Huntington Beach. Preliminary analysis shows that flooding overtops the existing drainage channel infrastructure in the study area between the 20% and 10% annual chance of exceedance storm events (5 and 10 year recurrence intervals, respectively), putting approximately 400,000 area residents and 44,000 structures at risk of inundation during a 0.2% ACE event. Study analyses were focused on modifications to the existing channels that include: C02 Bolsa Chica Channel; C04 Westminster Channel; C05 East Garden Grove-Wintersburg Channel; and the C06 Ocean View Channel. The Minimum Channel Modifications Plan is the NED Plan. It reduces flood risk primarily by lining the existing drainage channels with concrete, thus increasing conveyance efficiency. The Maximum Channel Modifications Plan has been identified as the LPP. It reduces flood risk primarily by altering the geometry of existing drainage channels to increase conveyance efficiency and storage capacity throughout the study area. The expanded channels in the Maximum Modifications Plan would primarily be concrete lined and rectangular in cross section. Both of these plans include additional downstream measures to address the impacts of increased flood flow conveyance resulting from the channel modifications. The downstream measures include increasing the span of Warner Avenue Bridge and removing the tide gates on C05. Compatible nonstructural measures were also included in the NED Plan to lessen the life safety risk associated with flooding in the project area. Each plan will require mitigation to address impacts to habitat. The NED Plan has an estimated first cost of $483,856,000 and includes mitigation to address the direct impact to 0.15 acre of estuarine wetland, indirect impact to 1.70 acre of eelgrass, and temporary direct impact to special status species’ foraging habitat. The LPP has an estimated first cost of $1,224,000,000 and includes mitigation for the direct impact to 0.15 acre of estuarine wetland, indirect impact to 1.70 acre of eelgrass, and temporary direct impact to special status species’ foraging habitat. The Final EIS is available for public review beginning April 24, 2020. The official closing date for the receipt of comments is May 26, 2020, 30 days from the date on which the notice of availability is made publically available by the U.S. Environmental Protection Agency. Comments may be mailed to the address listed below or hand delivered in person during business hours (Monday through Friday 8am to 5pm local time) to the address listed below. Comments may also be emailed to the email address listed below.
Description:	Integrated Feasibility Report and Environmental Impact Statement/Environmental Impact Report
Rights:	Approved for Public Release; Distribution is Unlimited
URI:	https://hdl.handle.net/11681/48072
Appears in Collections:	Environmental Documents