Agenda - 03-26-2009 - 4a2 - Laserfiche WebLink

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4a-14 transportfactars. The transport factors describe the attrition of nutrients as they travel dawn through a subwatershed~ if the looal expork was reduced by 8°l0, the delivered [aad would also be reduced by 8°l0, The local e~part and delivered [aad would not be the same "mass," but they vuill be the same "percent mass." Cara the ~VV~ provide some o[arificatian? 4. The cost estimates far additional regulatory transactions on the part of [oval governments for new development Mpg. 3} and for riparian buffer protection are significantly under estimated. host estimates assume negligible costs foradditianal regulatory transactions on the part of local governments for new development {pg~ 5~ and for riparian buffer protection, partly because local governments already have programs that deal with new development stormwater controls ar~d stream buffer protection to same degree. However, the Jordan Rules for new development storrnwater treatment and riparian buffer protection are sufficiently different in many ways, and much more strict in other ways, to require extra time and effoltfrom local jurisdictions for increased inspection and enforcement costs din orderta ensure compliance, which is the responsibility of local governments}, increased plan review casts experience has shown that mare complex engineering calculations require significantly more plan review}, and increased public education and outreach. 5. host calculations for new developments use a weighted average for the entire Jordan vuatershed, ratherthan different calculations forthe different subwatersheds {pg. 37}, This greatly underestimates costs for those in the Upper New Hope Arm subwatershed and overestimates costs for others. ~. In the section concerning nevu development, the calculation methodology assumes no regulatory costs to developers in ~g09 or ~~~ ~ for Bonne reason they are merged with riparian buffer protection ~ but not all riparian impacts happen in the course of development} Mpg. 4g}. However, prudent jurisdictions are likely to attempt to modify their development ordinances to approximate the expected tarmwater program rules in order to minimise the amount of retrofitting they have to da to very new developments. imi[arly, it assumes there will be no maintenance costs far BI~Ps in 200 and ~~~ ~ as well Mpg. 46~. ~'. In the section concerning new development, casts are likely underestimated for chapel Hill as propartionatelymore of its development will be moderate-to-higher density residential and mixed development, incurring much greater treatment req~irernents average Th[ load X5.0 Iblaclyr}than for residential average TIV load 4,04 Ib~aclyr} Mpg. 40}, A likely unintended side effect of the nutrient management strategy encourages sprawling residential development over compact farms that set aside open space because the nutrient treatment requirement is sa much greater for compact development. 8. host calculation methods far new development also used an allowable nitrogen value of ~.~ Iblaclyr, higher than the ~.~ Ib~aclyrthat Upper New Hope Arm ~UNHA} developers will be allowed Mpg. 40}. Using the designated UNHA target, developers will have to treat up to S5°I~ of nitrogen coming off their sitar. vvith an average ~~IP efficiency for nitrogen of 30°l0, and the prablerns of using BNiPs in series ~lov~rer B~[Ps in series only remove a pOrt~an of what IS left}, developers would have t0 Install a m~nlmum of three Bi~1Ps to get down to the 4.0 Ib~aclyr threshold far buying nitrogen credits and would have to use five MPs per care to get below the u[tirrrata ~.~ Iblaclyr goal. Even residential, with 11~ acre lots, would require two ~NiP per acre, calculations only use a single BIk~P cost- effectivenessvalue, which you can only assume if you use only one ~CIICP. BlU[Ps in series will have progressively poorer cost-effectiveness. Treatment efficiencies for BI~IPs are Page ~ of 9