Data and Billing Analysis

This section discusses the analysis of the current data and future data needs to support a stormwater enterprise fund in Bristol. As part of the 2012 Stormwater Utility District Feasibility Study, a Geographic Information System (GIS) database was prepared containing aerial images, a town-wide updated impervious cover layer, parcel layer and tax assessor data.  It was determined that that newer data were available.  The table below summarizes the 2012 and updated 2016 data collected, reviewed and analyzed.

Available Data Summary

Available Data Summary

Parcels, Database and Mapping Analysis

The analysis of parcel GIS data and Computer Assisted Mass Appraisal (CAMA) data were compared to aerial orthophotography with observed slight offsets in alignment, however, this approach was deemed reasonably sufficient to make per-parcel approximations of impervious area.  In addition, an approach to properly billing shared parcels for stormwater fees included a simple equal distribution of impervious area amongst the number of owners. Below is an example of a condo/townhome complex shared by 300 separate property owners.

Shared Parcel Example – condo/townhome complex.

Shared Parcel Example condo-townhome complex

Impervious Surfaces

The 2013 Statewide Impervious Surfaces GIS data layer contains buildings, sidewalks, roads, driveways, parking lots, etc.  Features that were captured and not captured during the data review and evaluation are listed in the table below. 

2013 Statewide Impervious Features and Surfaces

Statewide Impervious Features and Surfaces

Given all the ‘accuracy’ factors taken into consideration for the available data, the smallest potential billing unit of impervious area recommended for the stormwater fee would be approximately 1,000 sq ft. Refinement of the impervious area data would be needed to develop smaller billing units.  It was also noted that periodic updates to the Impervious Surfaces data layer and other data are generally required throughout the life of a stormwater enterprise fund to ensure the accuracy of fee assessments.

The total number of properties by type is shown in the figures below with the analysis of impervious area by property type. It is important to note that single-family residential properties account for the majority of properties, but not the majority of impervious area - an important consideration when considering whether to pay for stormwater management on the basis of taxes or a SMEF.

Property Type Distribution
IA Distribution

Billing Database Analysis

The Town’s data for billing systems was reviewed along with existing billing mechanisms to determine how a SMEF might be billed and the level of effort to develop a master account file (MAF). The Town bills for taxes and sewer once a year on the same bill and payment is due quarterly. The database, therefore, includes all properties that receive a tax bill, sewer bill or both. Since there are relatively few tax exempt properties (i.e., churches and nonprofit organizations) and 44 stormwater fee exempt properties (such as State-owned properties), the development of a MAF for billing stormwater on the basis of the current tax and sewer database would require very little effort to match the impervious area and billing units to each parcel. 


As an alternative to billing stormwater with taxes and sewer, the Town could develop a standalone bill. This approach would require significantly more effort to develop and manage, as well as higher delinquency rates since it would be more difficult to enforce. The Town does not bill for water services (provided by the Bristol County Water Authority), so this was not considered to be a viable option. The advantages and disadvantages of the primary billing options are summarized in the table below.

Primary Stormwater Billing Approaches

Priomary Stormwater Billing Approaches

Future Data Needs

Data that is accurate and representative of current conditions in Town is essential to the success of a Stormwater Enterprise Fund. The Town will need to continue to update the impervious cover information as land use changes, new properties are developed, or properties are redeveloped to support the rate structure and billing system. The most recent parcel GIS data layer will also be required to establish the initial rate structure. Periodic database maintenance will be necessary to ensure the continued accuracy of the data as changes occur. Future data needs to develop the MAF and support the stormwater fund are summarized in the table below.      

Future Data Needs for Stormwater Fund

Future Data Needs