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Emergency Remediation - 2480 Tracy Blvd., Tracy, CA. • Page 10 waste Endorsement issued by the California Contractors State License Board, to implement the approved emergency remediation plan. Dietz Irrigation mobilized to the site on April 8, 1996. Upon arrival on-site, Dietz Irrigation personnel took technical and operational control of the site, but close communication was maintained with the general construction contractor so that the soil and groundwater remediation work would delay the construction project for as little time as possible and so that, whenever the remediation program would permit, work on elements of the project that were on the critical path could be advanced. Change in Elevation of Foundation Slab After further evaluating the relationship between the as-designed elevation of the top of the proposed basement slab, the water-logged and very soft condition of the soil in the bottom of the basement excavation at the depth to which it had been opened at that time, and the need for continuous pumping of contaminated groundwater throughout the life of the new car-wash and lubrication-service facility if basement floor were to be constructed at the original design elevation, Dietz Irrigation's project manager and The San Joaquin Company's engineer-of-record for the remediation work recommended that the floor of the basement be raised. Although time constraints precluded an exhaustive cost-benefit analysis of this design revision, it was clear that, if the need to operate a dewatering pump to ensure a dry basement could be reduced or eliminated, such revision of the original design would greatly reduce the technical complexity of, and costs associated with, management of the problems caused by the contaminated groundwater. A meeting to consider a change in the elevation of the basement slab was held on site between the owner, the engineer in responsible charge of the remediation, the remediation contractor and the general construction contractor's superintendent. Based on the considerations outlined above, it was decided that the elevation of the basement slab should be raised by approximately two feet. Following the decision to raise the basement slab, the excavation plan was adjusted and the project architects were requested to make the necessary design changes so that the construction contractors could plan for the consequent revisions to their scope of work, including placement and compaction of an additional two feet of engineered fill over most of the previously-graded site, construction of a low retaining wall along the perimeter on the north, east and south sides of the property, and other, consequent ,modifications to the structure, drainage facilities and paving of the car-wash and lubrication-service facility. Excavation of Contaminated Soil Excavation of contaminated soil to permit placement of the basement slab and construction of the basement walls was started shortly after pumping of groundwater from the basement dewatering system was initiated. The methods used to pump, treat and