04-20-99 CCM - Laserfiche WebLink

Home Browse Search

SENT BY:DPRA St -Paul, MN '4-12-99 ; 3:36AM 612 22f 9522 612 407 4191414 ...v n[Iq gURFACE COVERAGE 4u surfaces" (Town of Brunswick 1991). In this case, the very low impervious limit was feasible because the total area affected was fairly small, the use was largely residential, and the specific pollutant of concern was nitrogen emanating from septic systems, resulting in zoning that called for a minimum lot size of one unit per five acres. This "down -zoning" approach, which has also been used � the Buttermilk Bay area in Mas- sachusetts (Horsley and Witten 1991), is practicable for small areas with septic -related concerns, but if ap- plied over large areas, can lead in the long run to pro- motion of sprawl. Strict limits may be appropriate, yet in practice they can result in the peed for cam plicared exemption provisions, or even raise the specter of private prop- ercy rights takings (Land Use Law and Zoning Digest 1995; Ross 1995; settle Washburn, and Wolfe 1995). One method for "softening" the concept of limits is to allow for flexibility on the site level. In this scenario, an ordinance setting a limit (or goal) for a site's imper- vious coverage would require more stringent on -sire stormwarer treatment when the limit is exceeded. This type of approach will undoubtedly become more com- mon as the information base on removal efficiencies of various treatment measures expands. Another type of flexibility, comes from applying performance Stan- dards to specific elements of imperviousness within the landscape. In their discussion of next steps, the Olympia study (City Of Olympia 1995) cites the devel- opment of performance -based standards for side- walks, parking, and landscaping "to encourage innovation and provide flexibility in meeting impervi- ous surface reduction goals." One practical regulatory application of impervi- ous coverage is for smrmwater utility assessment, an "impact fee" that is growing in use in, urban areas of the country as a way of paying for the treatment and control of polluted runoff. Impervious surface has long been a key determinant iri mathematical models that.predict the volume of runoff from a given piece of land. Scormwater ucilicy assessments have taken the lead from these models in using imperviousness as a basis for a utility race structure chat fairly distributes the cost of treatment according to a property s contri- bution to runoff. Such systems are now in place in many areas, in- cluding Kansas City, Missouri; Kicsip County, Wash- ington; and throughout the state of Florida. This type of application requires a community -wide assessment of impervious coverage, and a wide range of tech- niques is being used. In Kansas City, race structures are based on digitized high -resolution orthorecrified aerial photos (Murphy 1995), while in Florida they are based on statistical surveys of area lots (Livingston 1995). The Kitsap County, Washington, Comprehen- sive surface and Stormwater• Management Program, esublished in 1994, creates a rare structure based on an "equivalent service unit" equal to the average esti- maced amount of impervious surface area on a single- family residential parcel (Kicsap County 1994). Such programs not only raise Funds far mitigation of adverse impacts, but also, by attaching a cost to im- perviousness, provide an economic incentive to reduce it. Apparently, this effect is beginning to be seen in Florida, where the cost savings associated with lower stcrmwater utility fees have provided the impetus for reduction of impervious cover during site redevelop- ment (Livingston 1995). Integrating Storm.Water Control into Community Planting The strategies described above demonstrate chat for the planner, imperviousness can provide a useful framework for addressing the impacts of urbanization on water resources. But the advantage of this approach goes beyond any specific application. We have found that working with a town on water resource protection often leads to related natural resource issues like open space preservation and forest management. Our re- cent experience with NEMO has taught us that fram- ing water issues largely in terms of imperviousness serves to expand the range of these connections. Once water pollution is linked to impervious cov- erage and its various components, is has a way of in- sinuacing itself into issues currently "on the table" in town. Road widths and curbing may be subjects of town debate about cost or neighborhood character. Parking and landscaping requirements for commercial zones may be undergoing reexamination for aesthetic reasons. The appropriateness of "big box" retailers may be a hot topic, with arguments centered around traffic congestion and the impact on local merchants. An open space plan may be in the formative stages, or the use of stream buffers being questioned. Citizens may be interested in naturalistic landscaping, water conservation, or volunteer monitoring of local water- ways. These typical local debates, drawn from towns working with the NEMO Project, now have elements of water quality and impervious surface reduction as part of the mix. And through these debates, the sub- jecc of water quality in the community is extended be- yond land -use -related staff and boards co include engineering and public works departments, land trusts and other nonprofits, and citizens. Cross connections of this type are an important key co ensuring the implementation of any planning initiative. For the professional planner, they create APA JOURNAL -SPRING 1996 255