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119 <br /> DISTRICT MAXIMUM DENSITY <br /> U-ENO-PW Maximum density is as permitted in the underlying zoning district. <br /> L-ENO-PW <br /> HAW-PW BMPs are required in some cases where density exceeds 1 dwelling unit per <br /> JORDAN-PW acre. Refer to Article 6.23.6c1. <br /> 6.23.6 STORMWATER INFILTRATION AND DETENTION <br /> As a watershed becomes more developed, the amount of impervious surface increases, causing <br /> a decrease in the rate at which stormwater runoff which can be absorbed into the soil. This <br /> results in more stormwater flowing directly into streams and other water bodies. Because this <br /> direct runoff has not been filtered through the soil, pollutants from the air and land surface enter <br /> streams and increase the potential for pollution of drinking water supplies. <br /> The effects of stormwater pollution on drinking water supplies can be minimized by one of two <br /> general approaches. First, the amount of stormwater runoff which reaches drinking water <br /> supplies can be controlled by assuring that there is adequate ground area into which water can <br /> be absorbed. This type of non-structural control is achieved through limitations on impervious <br /> surface. A second approach is to collect stormwater run-off in engineered ponds so that <br /> pollutants may settle. The water is then slowly released and contains fewer impurities when it <br /> reaches the water supply reservoir. The watershed protection standards adopted by Orange <br /> County utilize a combination of these two approaches. <br /> a) Non-Structural Stormwater Control <br /> The first inch of stormwater run-off shall be controlled to the extent possible through on- <br /> site infiltration and through the use of methods which rely on natural soil properties for <br /> absorption and treatment. <br /> In order to promote infiltration of stormwater runoff into the soil and minimize direct and <br /> immediate runoff into streams and water supply impoundments, the maximum percentage <br /> of the total lot area which may be covered with an impervious surface shall be specified. <br /> This limit is referred to as the "impervious surface ratio". <br /> Impervious surface calculations for an individual development shall be cumulative for <br /> original construction and any subsequent additions. One-half of the width of any of any <br /> existing or proposed road adjacent to an individual lot shall be included as impervious <br /> surface for that lot, except in the case where an existing road was contained within a <br /> dedicated public right-of-way on January 1, 1994. Infiltration techniques not only <br /> remove both suspended and dissolved pollutants, but they require less maintenance, <br /> reduce flooding,promote groundwater recharge and help maintain stream flow during dry <br /> periods. <br /> Where on-site infiltration methods are utilized, areas for such purposes shall be <br /> designated on the plat and shall remain undisturbed both during and after construction. <br /> 3 <br />