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CHAPTER 5 BILLING STRUCTURE AND DATA COLLECTION METHODS EXECUTIVE SUMMARY Hand in hand with the development of the rate structure is the compilation of data necessary to support the collection of the fees. The purpose of this chapter is to consider the various data required for different rate structures and methods that can be used to collect and maintain the data. The first section considers the types of data needed to support various fee structures. If the utility is based on a non-ad valorem assessment, then the data will relate to the parcel and owner of the property. If the utility is based on an existing utility bill such as electricity, water or sewer, then the data will relate to the existing utility customer (a tenant or owner). Furthermore, most utilities are based upon a residential billing unit that is the average impervious area (or a combination of impervious and pervious areas) of either single-family residences or of all residential types. Thus, impervious areas (and possibly pervious areas) are needed for residential and non-residential parcels. If the rate structure supports individual or tiered residential rates based upon area, then individual impervious area data are needed for all customers. Non-residential fees are usually based on the impervious area or combination of impervious and pervious areas of the customer's property. Credits and exemptions also require customer specific data usually related to onsite stormwater facilities and local drainage patterns. When compiling the data, rate structure issues such as the handling of semi-impervious areas (e.g., sand, gravel and open water), rights of ways, and vacant/undeveloped property need to be resolved. The second major section in this chapter discusses methods for collection of the appropriate data. Data collection can be the labor intensive and costly portion of the implementation process, so planning ahead for this effort is important. Data requirements, based on the discussion of rate structures, include impervious and pervious areas, number of dwelling units for residential parcels, onsite stormwater facilities, land uses, and general runoff patterns. Numerous existing sources of such data are available including the Property Appraiser's office, water management district, and previous stormwater studies and measurements. When these data are collected or impervious/ pervious areas measured, quality assurance measures should be followed to provide accurate and reproducible results. The measurements need to be accurate to the 10's or 100's of square feet, however. Impervious and pervious area data can be derived from manual measurements (about 0.5 hours per parcel) or digitally (a little less than 0.2 hours per parcel). Aerials can be obtained from the Property Appraiser's office, and digital aerials can be obtained from the water management district or scanned at a resolution of about 1,000 dots per inch. Field measurements should be provided for impervious and pervious areas that can not be determined from the aerials (e.g., covered by trees) and which are associated with the 100 to 150 customers with the largest fees. Dwelling unit information can be derived from Property Appraiser data, customer surveys, and other indirect sources (e.g., apartment guide, fire department, etc.). When impervious area data are collected for a sample of residential parcels, proper statistical sampling methods should be used. Once the billing database has been developed for the first stormwater utility bill, the database needs routine maintenance to keep the data accurate and representative of the customer's situation. The caretaker of the billing database can be the stormwater department or the building department. The building department processes building permits that contain information on changes of impervious area and dwelling units, both of which are needed for the billing database. Methods for estimating the costs associated with data collection are discussed. Experience has shown that data collection may cost about 1/8th to 1/6th of the annual revenue for the first year. For example, data collection will cost approximately $125,000 to $170,000 for a utility that will collect $1.0 million in the first year. Another method is to estimate the costs using unit costs and estimated labor hours. Suggested unit costs and a sample calculation form are offered as part of the chapter. Geographical information systems (GIS) can help the overall stormwater utility data collection process by allowing easier measurement of impervious and pervious areas and visually recording the data for future reference. A discussion of GIS tools and methods is offered in this chapter to support the stormwater utility fee data collection process.
5.1 Introduction 5.2 Types of Data Needed 5.3 Data Collection Methods 5.4 Database Maintenance 5.5 Costs of Data Collection 5.6 Geographical Information Systems 5.7 References Appendix A Appendix B
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