Draft EA - San Diego International Airport

SAN DIEGO INTERNATIONAL AIRPORT – PROPOSED RUNWAY 9 DISPLACED THRESHOLD
present. Under the Proposed Action, no coordination on jurisdictional wetland issues with the CCC would be
required.
4.8 Floodplains
Executive Order No. 11988 was enacted in order to avoid, to the extent possible, the long and short-term
adverse impacts associated with the occupancy and modification of floodplains and to avoid direct and
indirect support of floodplain development wherever there is a practical alternative. The order was issued in
furtherance of NEPA, the National Flood Insurance Act of 1968, and the Flood Disaster Act of 1973.
Floodplains are defined as lowland and flat areas adjoining waters that are subject to a one percent or greater
chance of flooding in any given year, i.e., a 100-year flood event.
4.8.1 METHODOLOGY
Potential floodplain impacts were evaluated by comparing the location of Proposed Action elements with
floodplain mapping prepared by the FEMA. The proposed project or an alternative would cause a significant
floodplain impact if it would impose a flood hazard on other properties, or place development wholly or
partially within a FEMA-mapped 100-year floodplain such that substantial flood hazards would result. Impact
significance also is assessed with regard to Executive Order 11988 (42 FR 26951 (1977)), “Floodplain
Management.” Under this Executive Order, federal agencies must take action to avoid development in the
100-year floodplain unless it is the only practicable alternative; to reduce hazard and risk associated with
floods; to minimize the impact of floods on human safety, health, and welfare; and to restore and preserve the
natural and beneficial value of the base floodplain.
4.8.2 NO ACTION ALTERNATIVE
The No Action alternative does not include any development on or adjacent to the 100-year floodplain;
therefore, this alternative would have no impacts to a 100-year floodplain and there would be no increased
potential for floodplain impacts.
4.8.3 PROPOSED ACTION
As indicated in Section 3.5.4 in Chapter 3, Affected Environment, virtually all of SDIA is mapped as Zone X,
"areas determined to be outside the 500-year floodplain." The portion of the MALSR system that extends into
the Navy Boat Channel is located within the 100-year floodplain. However, the MALSR lights located in the
Navy Boat Channel are located on light stations. The MALSR lights that need to be relocated as part of the
Environmental Consequences
[4-22]
Draft EA