Agenda - 06-01-2010 - 7a - Laserfiche WebLink

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Falls Lake Draft Rules Comments 8 Page 5 There seems to be considerable uncertainty concerning the accuracy and reliability of the modeling which was completed in support of the rules development process, as supported by the concept of the need for a "re- examination" of the nutrient management strategy, which otherwise would not be needed. Such a re- evaluation is likely to be a good idea, as the true impact of Stage I of the draft rules is not known. It is hoped that any future "re- examination" of the nutrient management strategy includes outside experts and that it results in a more - accurate representation of the Falls Lake watershed. Thus, it seems logical to include a provision for examining the impact of the rules after they have been in place for some time, given the length of time that the draft rules are likely to impact the subwatershed, as well as the likely cost and the numerous uncertainties associated with the implementation of the rules. Ongoing evaluation and modeling of the lake appear to be worthy efforts, given what is involved in this effort and what is at stake. 6. It is extremely difficult to comment on the proposed existing development rules without knowing the details of the accounting tool which remains unavailable as of this writing. As a result, it is difficult to estimate the cost associated with implementing the existing development portions of the draft rules, but these costs are expected to be very significant. In an effort to quantify nutrient loading rates from existing development in advance of the availability of the future accounting tool, our staff has estimated impervious surface and land cover data from available high - resolution aerial photography. Nutrient loading rates were then calculated using the current methodologies which are in place for both the existing Neuse and Tar - Pamlico rules. Using the Neuse methodology, estimated nitrogen loading from developed lands within Orange County was only 1.46 pounds per acre per year (Ibs /ac /yr). Using the Tar - Pamlico methodology, estimated nitrogen loading was calculated to be only 1.30 Ibs /ac /yr and phosphorus loading was calculated to be 0.30 Ibs /ac /yr. These numbers clearly demonstrate that the existing watershed protection measures previously implemented by Orange County have significantly limited nutrient loading from developed lands within the county. In addition, these calculations also make evident that developed land within Orange County is already well below the baseline target for nitrogen included in Stage 1 of the draft rules (2.89 Ibs /ac /yr). The numbers calculated using the Neuse and Tar - Pamlico methodologies described above also further support point #1 in this document, the concept of using loading targets rather than a "one -size fits all" approach to achieve the proposed nutrient reductions. Otherwise, in order to meet the proposed reductions of 40% for nitrogen and 77% for phosphorus, Orange County would have to reduce loading rates from developed lands to 0.78 Ibs /ac /yr for nitrogen