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23 <br /> Moft michael m. hughes, p.e. <br /> Civil Engineer <br /> Municipal systems with greater water demands intrinsically have larger diameter mains and the larger <br /> diameter pipes also provide adequate supply for fire hydrants;whereas the smaller diameter water mains <br /> in the rural systems (by design for water quality purposes) are at a disadvantage where fire protection via <br /> hydrants is concerned. <br /> In the case of Harts Mill since the water main in Frazier Road is 6"and pressure is regulated by the <br /> elevated storage tank on US70, all designed for water quality,there is no benefit to upsizing the water <br /> system within the Village to 8"pipes for the provision of adequate fire flow at the hydrants. The <br /> constraint is the network providing the water to the village. The fire flow capacity at the hydrants in the <br /> village will be the same with either 6"pipes or 8"pipes as the backbone for the residents. <br /> To the contrary, if 8"water line were installed in the village the residents of Harts Mill would experience <br /> a degradation of water quality until the community is fully built out because they will not withdraw <br /> enough water from the system to keep the age of the water in the pipes to a minimum. <br /> For these reasons, inasmuch as OAWS has indicated that they do not have plans to upgrade the water <br /> mains in US-70 or Frazier Road,the most appropriate pipe size for the backbone of the water system in <br /> Harts Mill Village is 6". The permit drawings we submitted show that those pipe sizes drop to 4"when <br /> the aggregate number of residence withdrawing water diminishes further into the project; again for water <br /> quality purposes. <br /> The volunteer fire department has indicated that the 6"mains with hydrants will be acceptable to them, <br /> knowing the amount of water that they would expect from the hydrants is limited. They have indicated <br /> that their primary supply of firefighting water will be the onsite pond which is how they operate in this <br /> fire district. <br /> The fire hydrants that the volunteer fire department requested are only there as a backup to the pond, and <br /> they indicated that they have the means and methods to utilize those hydrants, even with their limited <br /> capacity, as needed. <br /> We hope that this clarifies the considerations in the design of the water system for Harts Mill, please feel <br /> free to call or e-mail if additional information or clarification is required. <br /> Very truly yours, <br /> Michael M. Hughes, PE <br /> 8112 Orange Grove Road Chapel Hill,NC 27516 (919)270-6462 <br />