SITE INFORMATION AND CORRESPONDENCE

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Bert E. Van Voris - 14 - 17 September 2004 Supervising Engineer Comment: The elevated levels of total nitrogen and nitrate in Park West soils indicate the historic discharge of olive leaves to this field has overloaded the soil with nitrogen to a level that exceeds agronomic demand by several orders of magnitude and, as a consequence, constitutes a threat to groundwater quality. While Musco has been monitoring soils for several years, it has not to my knowledge provided data on the quality of Park West soils affected by the historic leaf discharge until it submitted the RWD. Regarding the suitability of the selected background soil for representing soils unaffected by the discharge of waste, I have requested Mr. Ben Hall several times to confirm that no waste had been discharged in this area. He has repeatedly stated that waste was never discharged to this area. The RWD's Figure 10 depicts the background location as outside Park West, yet the 2002 and 2003 soil monitoring reports by Dellavalle Laboratories— reports certified by Mr. Hall as accurate—describe how the locations of all soil samples were determined via GPS within an accuracy of+/- 300 feet and depict in Figure 1, Sample Site Locations,the background sample as being within the northern portion of Park West. The elevated concentrations of waste constituents (including nitrate) in the background location, which are comparable to that exhibited in soils within Park West proper, is inconsistent with the low concentrations of waste constituents in soil collected in 1999 from South Ridge from an area described as "never been irrigated." This soil was characterized as having nitrate-nitrogen (ppm) of 9 at surface, 1 at 36" bgs, and 7 at 60"bgs. On 24 June 2003, Regional Board staff obtained additional evidence that questions the appropriateness of the background soil sampling location as representing soil unaffected by the discharge of waste. Staff collected soil from a fallow area within the property adjoining Musco owned by Mr. Paul Harpainter. The nitrate-nitrogen concentration in soil from this area was nondetect from 0-6"bgs and 6.5 mg/L from 18-24"bgs. Staff also collected soil from the area north of South Ridge that had received olive leaves in 2002. The nitrate-nitrogen concentration in soil from this area was 9.9 mg/L from 0-6"bgs and 43 mg/L from 18-24"bgs. This data reveals the high potential for discharged olive leaves to overload soil with nitrate. Instead of trying to explain the high nitrate concentrations in soil from the background sampling location as due to unspecified past agricultural practices and dismissing the elevated nitrate concentrations in Park West soils as insignificant with respect to current discharge practices,the RWD should (a) evaluate the appropriateness of the background soil location as truly representing soil unaffected by all of Musco's past and current discharges and (b)present and evaluate the results of deep soil borings advanced in Park West(e.g., to at least 30 feet bgs) to ascertain the extent to which nitrate and other waste constituents attenuate with depth. To assemble this information, it will be necessary to collect soil from offsite areas for analysis for, at a minimum, the constituents identified in the MRP. The RWD notes that most of the applied salts are retained in the upper soil profile and references the soil sampling data to suggest"some of the inorganic constituents present in the applied process wastewater have accumulated to a limited extent in some areas of the shallow profile (emphasis added)." 16 The RWD explains the increase in soil sodium evident in only one soil profile as possibly"attributable to past agricultural practices."17 The RWD attributes the difficultly of establishing crop cover to irrigation