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Mr. Gabriel Karam, P.E. <br />Page 3 of 5 <br />B. Complete closure activities in accordance with the <br />closure plan within 180 days following the <br />beginning of closure activities. The Director of <br />an approved state may grant extensions of the <br />closure period if the "operator demonstrates that <br />closure will, by necessity, take longer than 180 <br />days and he has taken and will continue to take <br />all steps to prevent threats to human health and <br />the environment from the [landfill] [40 CFR <br />258.60 (g) ] . <br />In order to comply with the Federal regulations the San <br />Joaquin County Public Works Department (SJCPWD) must <br />complete closure activities on the Corral Hollow <br />Landfill no later than seven months after the final <br />receipt of waste as opposed to the 15 month closure <br />schedule specified in the closure plan. The closure <br />schedule and any associated cost changes should be <br />revised at this time. If, in the SJCPWD's opinion the <br />closure of the Corral Hollow Landfill will, by <br />necessity, take longer than 180 days to close the <br />closure plan must contain: <br />A. The proposed closure schedule (which Board staff <br />acknowledge has been submitted); <br />B. Reasons why the closure schedule will exceed 180 <br />days (e.g, unacceptable construction conditions <br />due to the onset of the winter rainy season, <br />etc.); and <br />C. State that the SJCPWD will continue to take all <br />steps to prevent threats to human health and the <br />environment during the extended closure period. <br />Note that approval of the closure and postclosure <br />maintenance plan will be considered granting an <br />extension to the time -frame for closure. <br />2. The surface runoff coefficient (C) used in the drainage <br />calculations of 0.3 is too low. While the vegetative <br />layer has characteristics similar to a turfed meadow <br />and has some water bearing capacity, the primary <br />purpose of the final cover is to minimize infiltration <br />into the landfill by promoting runoff. In addition, <br />most off the C values reported in the literature are <br />for storms with a five or ten year return period. <br />Usually, C values are increased for storms with lesser <br />recurrences (e.g., a 25 percent increase in the runoff <br />coefficient for the 100 -year storm) to account for <br />antecedent precipitation conditions. In the opinion of <br />