SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Figures 1. 2-3 , 1. 2-5, and 1.2-7 show PCE concentrations of 5 µg/L or greater in the middle and lower horizons at wells LM55 and LM56 with values of 12 . 1 and 11. 6 µg/L, respectively. Both of these wells are located approximately 1, 000 feet from the depot boundary. • Please identify the off-site well located 1, 600 feet from the depot boundary that is discussed in this section. 11. Section 1. 2 . 6. 3 , Page 1-12 The column header for the organics list shows seven compounds, but only six compounds are listed. What is the missing organic compound? 12 . Section 1 . 3 . 1, Page 1-18 Operating 8 , 000 hours would allow a maximum of 8 .7 percent downtime for maintenance, repairs, and any weather-related delays. Typical engineering assumptions should call for a minimum of 10 percent downtime. 13 . Section 1. 3 . 1, Page 1-18 Using the values obtained from Table 1. 2-1, the maximum levels of TCE and PCE are 560 and 411 µg/L, respectively. When summed, these values total to 971 µg/L, which is almost double the maximum contaminated groundwater value of "about 500 µg/L" given in the text. Please show the calculation for deriving the expected maximum concentration of contaminated groundwater and explain what would happen if a higher concentration actually required treatment. 14 . Section 2 . 2 . 2 , Pages 2-1 through 2-4 This section, entitled "Contaminants of Concern, " erroneously deselects 1, 1-dichloroethene, and carbon tetrachloride from consideration in the FS. The chemicals of concern have already been established in the RI and have been detected at levels above MCLS. As already stated, the FS needs to address the organic chemicals of concern from Section 6 of the RI. 15. Section 2 . 2 . 2 . 4 , Page 2-3 Carbon tetrachloride has been detected on site at a level above the MCL (refer to RI Table 4 . 0-1) . Therefore, the text in this section which states that carbon tetrachloride 5