SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Mr. Allen Fetters - 2 - 14 December 2006 • nitrate) greater than the water quality objective of 45 mg/I. The highest concentration is consistently found in MW-103, which is downgradient of the eastern tank farm, also known as the Liquid Batch Plant. The second highest concentration is found in MW-101, on the upgradient boundary of the site. Pesticides and herbicides have not been found in any of the monitoring wells. Ripon Farm Service performed additional characterization presented in the Limited Subsurface Investigation Report. This work included water and sediment samples from the upper and lower surface water sumps, and three shallow grab groundwater borings, two of which contained water. The surface water sumps receive site surface runoff and are located adjacent to the Liquid Batch Plant. Grab groundwater samples from boring B-102, adjacent to the sumps, contained concentrations of nitrate, sulfate, calcium, and potassium that were nearly identical to those found in water obtained from, the upper sump, while ammonium in B-102 was about 75% of the concentration found in the upper sump. The concentration of constituents in water obtained from the lower sump were notably less than those found in the upper sump. Grab groundwater samples from boring B-101, on the upgradient property boundary, about 80 feet west of MW-101, showed concentrations of nitrate, chloride, sulfate and calcium similar to those found in groundwater samples from upgradient monitoring well MW-101 . Ammonium and potassium concentrations were an order of magnitude less in B-101 than in MW-101. The monitoring well results and grab groundwater samples suggest the following: • The sump, its collection area, or the batch plant appears to be allowing site runoff to enter groundwater. There may be other discontinuities in the site containment and collection system that have not yet been identified. • A contribution of nitrogen in shallow groundwater could be coming from off-site. Aerial photos taken in 1991 show a pond upgradient (south) of the site that was associated with a truck wash facility, and north of the site, Jimco truck stop operates two large stormwater ponds. Both of these ponds could be or could have been contributors to nitrogen in groundwater. Monitoring Well Work Plan In the Work Plan for Monitoring Well Installation (Work Plan) Ripon Farm Service proposes to install four shallow off-site monitoring wells to be screened in the interval from 30 to 40 feet below ground surface (bgs) and two deep monitoring wells, to be screened in a 20-foot interval roughly between 165 feet and 195 feet bgs. This is the interval where the City of Ripon's municipal supply well No. 12 is screened. A shallow and a deep monitoring well are proposed southeast of the Ripon Farm Service facility, near the former truck wash pond, a shallow well is proposed northeast of the facility, near Jimco's stormwater ponds, a shallow and a deep well are proposed northwest of the facility, which is north of the City of Ripon's supply well No. 12, and a shallow well is proposed west of well No. 12.