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BLACK & VEATCH SPECIAL PROJECTS CORP. <br /> TELEPHONE MEMORANDUM <br /> EBMUD BVSPC Project 40429.700 <br /> Stockton Service Center . BVSPC File D.2 <br /> Decay Coefficients for BTEX September 16, 1996 <br /> 12:35 PDST <br /> To: Ashok Katyal <br /> Company: Draper Aden Environmental Modeling <br /> Phone No. : (540) 961-3236 <br /> Recorded by: Tim Cook <br /> Assume oxygen limited degradation. Degradation term is related to the <br /> 1/2 life of the individual chemical constituents. The half life range <br /> is given in hours. This term must be divided by 24 and put in the <br /> denominator of the following equation to yield a decay coefficient (K) <br /> whose units are 1/days. <br /> K = .693 <br /> half life/24) a <br /> Half Life Ranges for BTEX <br /> Benzene: 240-17,280 hours } <br /> Toluene: 168-672 hours <br /> Ethylbenzene: 144-5,472 hours <br /> Xylenes: 336-8,640 hours <br /> Use the upper range value to calculate K as this is the most <br /> conservative value and will result in the smallest value of K. <br /> A simple check on the 1st order decay coefficient: <br /> 0.001/day is a reasonable value <br /> 0.0001/day is considered a very conservative and can be used when no <br /> site specific data is available. No regulator has ever objected- to <br /> 0.0001/day when no site specific data is available (very conservative <br /> assumption)'. <br /> cc: Girma Mergia, Philadephia BVSPC <br />