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22 <br /> Mffl�ft michael m. hughes, p.e. <br /> Civil Engineer <br /> July 31, 2015 <br /> Michael D. Harvey AICP, CFO, CZO <br /> Current Planning Supervisor—Planner III <br /> Orange County Planning Department <br /> Re: Harts Mill Water System Design <br /> Dear Mr. Harvey: <br /> There has been some deliberation about the extent of fire protection for the Harts Mill Village afforded by <br /> the Orange Alamance Water System (OAWS) and the sizing of the water mains within the village. The <br /> purpose of this letter is to describe some of the constraints when considering pipe sizing for Harts Mill. <br /> The principal purpose of the proposed water supply connection to the OAWS system for Harts Mill <br /> Village is the provision of domestic potable water for the residences. OAWS provides potable water to <br /> approximately 3,450 rural customers in the area around the Harts Mill Village. <br /> OAWS provides water via a network of underground pipes. The primary network water mains that would <br /> supply Harts Mill consist of a 12"pipe along US 70 from the water tower to intersection of Frazier Road, <br /> and a 6"waterline up Frazier Road which extends beyond the Harts Mill Village to serve customers north <br /> of Lebanon Road. The system pressures are maintained by the elevated water tower at theOAWS office <br /> at 5900 US-70, Mebane,NC. <br /> The principal mission of OAWS is the provision of high-quality potable water,the physical and chemical <br /> characteristics of which are regulated by the USEPA. As a result the OAWS water network has not been <br /> designed and constructed for fire protection. <br /> Unlike municipal systems which serve high-density land-use with residential and commercial water taps <br /> on the water mains every hundred feet or so, OAWS serves a low density rural community with water tap <br /> connections that may be many hundreds, or thousands, of feet apart. The water quality throughout the <br /> pipe network is regulated by the USEPA, and is directly proportional to the age of the water which, in <br /> turn, is a function of the amount of water withdrawn from the pipes by its customers. The less water that <br /> is withdrawn from the mains causes an increase of the age of the water(in the mains) as it travels from the <br /> supply(water tower)to the customer. Unlike wine,the quality of the water in the mains degrades with <br /> age as disinfectants lose their effectiveness and the natural chemical constituents in potable water have an <br /> increased opportunity for transformation. <br /> All water systems in the United States including OAWS are monitored by the USEPA and seek to achieve <br /> regulatory requirements for water quality by minimizing the age of the water in the mains. In rural <br /> systems like OAWS this results in smaller mains because demand for water(i.e.the withdrawal of water <br /> from the mains) is much, much lower than that of its municipal counterparts. <br /> 8112 Orange Grove Road Chapel Hill,NC 27516 (919)270-6462 <br />