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5. ALTERNATIVP.S 5.4 ALTERNATIVES CONSIDERED BUT REJECTED AS _ INFEASIBLE An off-site alternative in the Laguna Formation of the foothills was considered for inclusion in this EIR in order to eliminate the significant and unavoidable impact to farmland by finding a site located outside of the Central Valley that would not include prime farm land, farm land of statewide importance, and Williamson Act Contract land. This off-site alternative was rejected because of the lack of an adequate aggregate resource to meet the sponsor's basic objectives. Many resource sectors in the Laguna Formation of the foothills were not controlled by an aggregate company or encroached upon by competing land use as of 19881 (CGS, 1988). However, since 1988 many of these sectors have been developed as a result of growth in the Bay area,thus making any underlying resource unavailable for mining and/or extraction. Some new developments in the area include New Jerusalem and the Diablo Valley(Don Depraw,CGS). The Laguna Formation is one of several alluvial rock units found directly west of the Sierra Foothills. Sediments of the Laguna Formation are derived from weathering and erosion of resistant bedrock units in the Foothills. The Laguna Formation is an unsuitable material for PCC- grade aggregate due to several constraints,described below. First, since the Laguna Formation is Pliocene in age,it is significantly older than most material in the area which meets aggregate _ standards. Due to its age, significant weathering rinds,or fine-grained brittle outer casings, are present on gravel clasts. During mining, the brittle casing commonly becomes dislodged from the gravel, adding unwanted fine-grained material to the aggregate mixture. The formation itself is not easily crushable,but largely cemented,making extraction and processing difficult. Second, since the Laguna Formation is derived from the Sierra Nevada, volcanic clasts present in its matrix cause mining and processing difficulties. Third,due to significant clay content in the Laguna Formation,it costs more to process. Deflocculants,or chemicals used to remove clay and make a material more fluid,have to be used just to remove the clay. Many cycles of processing are often needed. There is no known instance of in which the Laguna Formation is used as an — aggregate material in the Sacramento/San Joaquin County area. The Laguna Formation is used primarily as a gravel subbase material (building foundations,etc.),but even then presents processing difficulties due to its clay content. No reports or studies have been published on the Laguna Formation(Don Depraw,CGS). 1 CGS Special Report 160,Mineral Land Classification:Portland Cement Concrete Aggregate in the Stockton-Lodi P-C Region(San Joaquin County,California)is the most recent report which assesses the resource sectors in the proposed project area. It was published in 1988. _ RMC Pacific Venmhs Qnany Musing and Re Ih fton Project 5-20 ESA/203015 Administrative Draft Em March 2004