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Kennedy/Jenks Consultants presence of groundwater within the wells, Musco collects and analyzes samples on a quarterly basis. The analytical results are submitted to the RWQCB. Elevated concentrations of nitrate have been detected regularly in samples from several of these monitoring wells. 1.2 Approach and Objectives To further evaluate potential sources of elevated concentrations of nitrate nitrogen in several of its 32 onsite groundwater monitoring wells, Musco proposes a two-phased approach. This Preliminary Work Plan addresses the first of these proposed phases. It is anticipated that information obtained during the activities proposed in this Work Plan will be used to inform activities to be proposed in a second Work Plan. In accordance with Provision 1.b., the second Work Plan will be submitted to the RWQCB no later than 30 July 2010. One of the wells with elevated concentrations of nitrate, Well MW-1, has historically been considered an upgradient monitoring well located on the southern roperty line an parWad - from the nearest land application area by a dirt access road (figure ver time, elevated 7 t' t" of nitrate have been detected in groundwater s s collected from this well (Figure 3). tis not clear whether the source of the elevated nitrate concentrations in u er is located onsite or upgradient and offsite. During a recent inspection of Well MW-1, it was noted that the concrete surface monument is no longer in contact with the ground surface. It is not known whether this has compromised the surface seal; if it has, then the vertical conduit along the outside of the well itself may be responsible for the elevated concentrations of nitrate in groundwater at this location. The objective of this Preliminary Work Plan is to describe the proposed installation of additional groundwater monitoring wells and exploratory soil borings in the vicinity of existing Well MW-1. In effort to install monitoring wells screened in the same water-bearing unit as Well MW-1, it may be necessary to advance several soil borings. It is anticipated that a maximum of four soil borings will be advanced, with a maximum of two monitoring wells installed. Data collected from the proposed monitoring wells will be used to evaluate a) whether elevated concentrations of nitrate are present in groundwater entering the Site from the southwest and b) whether some characteristic of the existing Well MW-1 has resulted in elevated concentrations of nitrate. Page 2 Preliminary Work Plan for Evaluation of Nitrogen in Groundwater Musco Family Olive Company, Tracy, California g:Ya gagletlminyobbM2014.00 m¢moMeWg+epoMNiRagen wk phlhrtMc