SITE INFORMATION AND CORRESPONDENCE

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Bert E. Van Voris ' 7 - • 25 February 2005 Supervising Engineer Runoff Management The addendum states ditch bottom and tailwater sumps will be sealed using compaction or a liner material such as bentonite. The land application areas will be inspected daily to ensure adequate pumping and minimize standing water. Bands of soil tillage or aeration, organic matter addition and incorporation, or sulfuric acid application treatments will be added upslope from the collection devices to minimize runoff. The addendum indicates the clay content of the soil is high and permeability is low, making leakage unlikely under most conditions. Soil infiltration and permeability will be improved by use of short irrigation sets, addition of organic materials, use of sulfuric acid, and mechanical treatments such as tillage or a lawn/turf aerator to cut plugs in the surface of the fields. Comment: The RWD should have provided an implementation schedule for lining ditch bottom and tailwater sumps. The WDRs should specify one. Soil Monitoring The addendum questions the relevance of soil data collected from 1999 to 2000, which characterizes the level of salinity in disposal area soils as much lower than current levels,because these data were collected in different locations than later samples and were analyzed by different laboratories. The addendum indicates that there is not a significant increase in root zone soil salinity between 2002 and 2004. Musco reiterates that the background soil monitoring location has received neither solids nor wastewater since the beginning of Musco's operations in 1985, is unaffected by all of Musco's past and current discharges, and adequately represents an area that has soils similar to those in Musco's land application area. A 3.5-acre pasture north of`Park West' also has received no solids or wastewater and continues to serve as a buffer between `Park West' and the background soil monitoring location. The addendum states that maps prepared by Dellavalle Laboratories and submitted by Musco showing `Park West' as including the background soil monitoring location are inaccurate, and the addendum includes a revised map that depicts `Park West', the 3.5-acre buffer pasture, and the background soil monitoring location as distinct and separate. The addendum states that the constituent distributions in the soil profile from the background location are dissimilar to those in Park West, indicating the background location has not received waste applications similar to that of Park West. The addendum states that the background soil monitoring location is on a small knoll, such that accidental runoff from land application areas is precluded. The addendum further indicates that the soil samples collected by Regional Board staff from Mr. Harpainter's property,which show very low concentrations of nitrate and salinity compared to Musco's background location and application areas, are not appropriate as background, as this area may have never been used for irrigated agriculture and historical uses are unknown. Comment: The soil data presented in the addendum is difficult to evaluate. Data on soil quality is not provided for all soil sample locations depicted. Figure 3 needs to be corrected (e.g., there are two locations depicted for Sample 7 collected in 2004, and 2001 soil sample locations are not shown). Soil sampling data collected in 1999 to 2001 prior to and at the onset of discharge to application fields is relevant for evaluating the extent to which Mn3C07S discharge has