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Amwouswecull <br /> • / s <br /> LimnoSystems <br /> Kenneth H. Reckhow, Ph.D. y' ��� . <br /> g„..V <br /> • MEMORANDUM <br /> • <br /> .To: Barrie Wallace <br /> From: K. H. Reckhow 15116� <br /> Re: Orange County Water Supply Study <br /> Date: March 14, 1988 <br /> At your request, I have reviewed the recent report by Hazen <br /> and Sawyer entitled "Orange County Water Supply Study Phase I" <br /> and examined options for future water supply for 'Orange County. <br /> Several points arose during this examination that are important <br /> in Orange County' decision yet were not discussed in the Hazen <br /> and Sawyer (H&S) study. These are: <br /> 1. The population served by the Hillsborough water supply system <br /> is 8, 300, and the served population is expected to increase to <br /> over 10, 000 by 1990 (H&S, pg. 3-10 ). This projected increase is <br /> important because North Carolina drinking water standards do not <br /> require trihalomethane .(THM) monitoring unless the population <br /> served is greater than 10, 000. Thus, within the next few years, • <br /> Hillsborough will be required to monitor for THMs and meet the <br /> State standard. <br /> 2. Chlorination of water supplies produces THMs, some of which <br /> are carcinogenic, from naturally-occurring organic matter (e. g. , <br /> plants and algae ). Water from reservoirs in relatively pristine <br /> ' watersheds may violate the State drinking water standard, given <br /> the naturally high nutrient levels in piedmont reservoirs. This <br /> is particularly true if chlorination occurs at the raw water <br /> intake, which is the current practice in Hillsborough <br /> (Hillsborough water supply operator - pers. comm. ). <br /> 3. The US EPA establishes drinking water standards later adopted <br /> by the states. EPA is currently considering .making the THM <br /> standard more stringent, possibly dropping it from 0. i00mg/1 to <br /> 0. 050mg/1 or even to 0. 020mg/i. This is .likely to result in <br /> changes in water treatment plant operation for many facilities. <br /> • <br /> • <br /> • <br /> • <br /> • <br /> • <br />