environmental assessment us border patrol, tucson sector

3-1012345678910111213141516171819202122232425262728293031323334353637383940414243444546473.4.1.4 GroundwaterThe major aquifers in the San Bernardino Valley Basin in the vicinity of the alternative FOBsites consist of recent stream alluvium and volcanic rock, and flow direction is generally fromthe north to the south. Artesian wells and springs support wetlands in this basin near the borderwith Mexico in the San Bernardino NWR. Recharge in the San Bernardino Valley Basin isrelatively high due to greater rainfall amounts in the bordering mountains and recharge of theaquifers by mountain-front runoff. The natural recharge estimate for this basin is estimated at9,000 acre-feet per year (2.9 billion gallons per year) (AZDWR 2009). Depth to water variesfrom 612 feet below the surface in the north central portion of the basin to 30 feet below thesurface along the border with Mexico (AZDWR 2009). As of 2005, there were 164 registeredwells in the basin with a pumping capacity of less than or equal to 35 gallons per minute, and 12wells in the basin with a pumping capacity of more than 35 gallons per minute (AZDWR 2009).3.4.1.5 FloodplainsThe Preferred Alternative, Alternative 2, and Alternative 3 sites are not located within a FederalEmergency Management Agency (FEMA) Flood Hazard Zone. The Alternative 4 site is situatedwithin a FEMA Flood Hazard Zone. However, the current property owner has constructed anearthen berm approximately 10 feet high around the property, and no residences or storagestructures were flooded during the last high water event (personal communication with propertyowner, Mr. Tom Peterson).3.4.2 Environmental Consequences3.4.2.1 No Action AlternativeUnder the No Action Alternative, the conditions at the alternative sites would not change. Notemporary or permanent impacts relative to surface water, stormwater runoff, hydrology orhydraulics, wetlands or waters of the United States, groundwater hydrology, or floodplainswould occur. Indirect impacts from illegal activity would continue. More agents would berequired to patrol the remote eastern zones of the USBP Douglas Station’s AOR to account forthe necessary drive time to their patrol areas. Indirect impacts from CBV activities andsubsequent USBP interdiction activities would be greater under the No Action Alternative thanany of the other alternatives.3.4.2.2 Preferred AlternativeThe Preferred Alternative would not affect the hydrology or hydraulics of any surface waterbody. Likewise, construction of the proposed FOB would not affect any wetlands or waters ofthe United States, as these resources do not occur at the Preferred Alternative site. The PreferredAlternative site is not located within a FEMA Flood Hazard Zone. Thus, no major impacts onhydrology or hydraulics, wetlands or waters of the United States, or floodplains would occur.Implementation of the Preferred Alternative would permanently impact up to 10 acres of soil,which would be cleared of vegetation and would be susceptible to erosion during constructionactivities. The proposed FOB would be expected to slightly increase the amount of impervioussurfaces in the vicinity of the site. A stormwater retention basin would be included in theproposed FOB layout (see Figure 2-2) to collect rainwater and other sources of runoff into acentralized area. This water would be allowed to evaporate or percolate down to thegroundwater table. Since the construction area would be greater than 1 acre, a NPDESStormwater Discharge permit would be required prior to construction. This permit would requireDouglas FOB EADraftAugust 2011