SITE INFORMATION AND CORRESPONDENCE

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Bert E. Van Voris • - 2 - • 28 April 2004 Supervising Engineer maximum saturated hydraulic conductivity as 1x10-6 cm/s. By 30 August 2002 letter to Thomas Pinkos from Paula Hansen and Robert Chrobak of Kennedy-Jenks Consultants (and certified by Chrobak, RCE No. 47145), Musco proposed to install a 2-foot-thick liner constructed using native clay soils to achieve a permeability of equal to or less than 10-6 cm/s. The letter enclosed a detailed description of the liner's proposed construction and quality assurance/quality control procedures attributed to Kleinfelder (Kleinfelder Enclosure). The enclosure states the hydraulic conductivities of the remolded samples of on-site surficial soils were 7.33x10-7 and 1.21x10"s cm/s. While Kleinfelder reportedly prepared the enclosure, neither it nor the letter identified the professional(s)responsible for the work. Hail explains in his 19 April 2004 letter that the Kleinfelder enclosure was not a work plan, but "guidance that Kleinfelder had been requested to provide concerning how to proceed with clay liner construction and verification testing if the concept had been approved by Regional Board staff." Hall claims that Regional Board staff"declined to grant Musco additional time to allow construction of a clay liner" and "rejected Musco's proposal verbally, stating such a liner would not meet Title 27 standards." The Regional Board staff referenced in Hall's letter dispute this allegation. Further, his statement incorrectly implies that staff has the authority to extend deadlines established by the Regional Board. Hall states, "Musco instructed the contractor team to complete the dam as designed and to scarify and recompact the native clay soil over as much of the reservoir surface as possible." On 20 April, I telephoned Hall to discuss this matter and asked whether Musco could provide certification by a registered professional that the reservoir bottom was constructed as he described. He stated that such certification is not available. On 16 January 2003,the California Department of Water Resources, Division of Safety of Dams, issued its certificate approving the dam and the reservoir began impounding wastewater. The dam consists of compacted earth and rests on a foundation that partially extends beneath the groundwater table. A 20-foot-wide, 4-foot-deep cutoff trench directly below the centerline of the dam fonns a barrier between the bottom of the foundation and deeper fine-grained soil (silt or clay) to reduce seepage flows and control seepage forces. The dam contains a horizontal blanket drain and pipe drain to control seepage comprised of groundwater, wastewater, or a combination of both. The blanket drain has a minimum width of 40 feet at the center and 20 feet at the edges. The blanket drain consists of a bottom 1-foot-thick layer of asphalt sand, a middle 1-foot thick layer of Caltrans Type H permeable drain rock, and a top 1-foot-thick layer of asphalt sand. Seepage collects in a 4-inch-diameter perforated pipe along the edge of the blanket drain, drains to a 2-foot-diameter riser pipe connected to a 4-inch-diameter pipe, and ultimately discharges to a surface water drainage course near the toe of the dam. According to the reservoir rating curve, the water surface elevation is 350 feet and the water surface area is 15.9 acres at the normal operating capacity. On 5 March 2003, water was observed surfacing at the toe of the dam where blanket drain emerges, according to Musco's March 2003 self-monitoring report (SMR) dated 1 May 2003, which Hall and Dennis Leikam certified. This water was sampled twice on 5 March and on 26 March and 23 April 2003. Samples of impounded wastewater were also collected, as were samples of water emerging from a spring upstream of the reservoir. The results of all this sampling were presented in the April 2003 SMR dated 30 May 2003, again certified by Hall and Leikam. The March 2003 SMR indicated that the water emerging from the dam's blanket drain contains calcium, magnesium, potassium, phosphorus,boron, and nitrate in concentrations similar to MW-3 and concluded that, "Preliminary results indicate that the water rising to the surface at the toe of the dam has a unique chemical signature that is similar to groundwater monitored in the nearby MW-3 monitoring well and dissimilar to the water in the reservoir." Neither person is qualified to interpret groundwater data. Evaluation of groundwater chemistry requires, in part,