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I [J I u L G C u amount when compared with the amount of recharge occurring in adjacent irrigated areas. The project's impact on recharge of the local ground water conditions would be minor. This impact is deemed to be less -than -significant. Mitigation 4.5-4 No mitigation is required or recommended. Impact 4.5-5 Project operation may result in adverse impact to artificial water -carrying structures, in particular the Banta-Carbona Irrigation Canal. During construction, portions of the site will be stripped and cleared of vegetation in preparation for grading. These activities will expose loose soil to potential wind and water erosion. Transport of these materials could temporarily increase suspended sediment concentrations and release pollutants attached to sediment particles into local water ways. Wind blown garbage could be transported and deposited into local waterways. Mitigation 4.5-5 Erosion control measures shall be instituted to minimize soil loss and sedimentation during construction. Dust, airborne contaminants, and garbage which could potentially impact the water carrying structures will be controlled by frequent watering of unpaved roads and working surfaces, and regular and frequent pick up of trash. Implementation of these mitigations will reduce the potential impacts to water -carrying structures to a less -than -significant level. Impact 4.5-6 Accidental overflow of flood waters from Corral Hollow Creek into the reclaimed gravel pit could create a safety hazard, or cause substantial damage to the operations, or could result in the transport of contaminants from the project site to downstream areas or into ground water. Although unlikely to occur, runoff of contaminants from the project site into Corral Hollow Creek may adversely impact aquatic habitat and current populations of existing species, or may impair other downstream beneficial uses. The project lies adjacent to the Corral Hollow Creek which drains a large watershed to the west and has caused extensive flooding in past years, most notably in 1983 and 1986. The creek has broken into adjacent gravel pits and filled them with water. Should this happen with the pit in operation, hazardous waste and other materials could be floated or scattered all the way to the San Joaquin River levees. Approximately 1.5 miles east of the proposed transfer site, the Corral Hollow Creek channel terminates. Flood water thereafter sheet flows across farmland. This would greatly exacerbate cleanup should Corral Hollow Creek divert into the transfer station pit. If a large amount of water overflowed into the reclaimed pit, it would quickly begin eroding a gully in the pit wall. The head cut of the gully could propagate upstream toward the creek channel. In the extreme case, a newly incised gully could capture the entire flow of the creek and divert it into the pit. A 100 -year 24-hour flood volume could potentially fill the pit to overflowing, resulting in sheet flow of water easterly toward a number of small lateral irrigation canals. ER -93-1 -72- (9-27-93)