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Offices in Illinois, Iowa, Minnesota, and Wisconsin 2901 International Lane, Suite 300, Madison, WI 53704-3133 (608) 242-7779 (800) 446-0679 FAX: (608) 242-5664 WEB ADDRESS: www.msa-ps.com 1 MEMO To: Water Resources Management Commission From: Ann Hirekatur, PH and Eric Thompson, P.E., CFM Subject: Stormwater Utility Feasibility Study Progress Report and Preliminary ERU Size Determination Date: March 12, 2010 Introduction In 2006 the City of Middleton conducted a very small scale evaluation of the feasibility of a stormwater utility. Because of the limited scope of the 2006 study it was necessary to operate within the limits of certain assumptions; one of those assumptions was that land use in the City of Middleton, specifically, the density of impervious area within typical land uses, was the same as published ‘text-book’ values. This memorandum represents a revision to the previous study following some additional parcel evaluations to obtain a more Middleton-specific estimate of impervious area density for the different land uses in the City. Stormwater Program Funding Under the current system of funding the City’s stormwater program through property taxes, residential homeowners pay for approximately 67 percent of the stormwater management costs while owners of nonresidential property pay for 33 percent of the program1. Under a stormwater utility, charges would shift to property owners that generate more stormwater runoff. Specifically, residential property owners would pay for only 30 percent of the stormwater management program, while non-residential and tax-exempt users will fund 57 and 13 percent, respectively2, as illustrated in figure 1. FIGURE 1: CITY OF MIDDLETON STORMWATER PROGRAM FUNDING ERU Determination 1 Property value figures are from the 2006 stormwater feasibility study conducted by MSA. 2 In the 2006 stormwater utility feasibility study, the estimated distribution of charge under a stormwater utility was non-residential = 55%, tax exempt = 14%, and residential = 31%. Non- Residential 57% Property Tax System (Property Value) Residential 30% Stormwater Utility (Impervious Area) Residential 67% Non- Residential 33% Tax Exempt 13% Non- Residential 57% ---PAGE BREAK--- Offices in Illinois, Iowa, Minnesota, and Wisconsin 2901 International Lane, Suite 300, Madison, WI 53704-3133 (608) 242-7779 (800) 446-0679 FAX: (608) 242-5664 WEB ADDRESS: www.msa-ps.com 2 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 Lake Delton West Allis Middleton Wauwatosa Sheboygan Appleton St. Francis Cudahy Oshkosh Eau Claire Butler Neenah Glendale Janesville Bellevue Grand Chute Sun Prairie Garner's Creek Fitchburg New Berlin Greenville Estimated City of Middleton ERU In Wisconsin, the most commonly used approach for determining stormwater utility charges is the equivalent residential unit (ERU) method. An ERU is the average amount of impervious area associated with single- family, duplex, and multifamily living units. Preliminary data used to determine the Middleton ERU size is summarized in Table 1. According to this preliminary data, the estimated Middleton ERU size is 2,106 square feet3. This is less than the average ERU size for Wisconsin municipalities, which is roughly 3,000 square feet, as illustrated in Figure 2. TABLE 1. RESIDENTIAL UNIT IMPERVIOUS AREA SUMMARY Type of Residential Unit Average Impervious Area Per Unit (sq. ft.) Approximate Number of Units Citywide Single-Family 3,144 3,589 Duplexes 1,985 518 Multi-Family 1,259 4,329 Weighted Average = 2,106 Total Living Units = 8,436 FIGURE 2. WISCONSIN STORMWATER UTILITY ERU SIZE COMPARISON A randomly selected sample of 157 of the city’s 3,589 single-family parcels were analyzed to determine the average amount of impervious surface for single-family homes in the City of Middleton. This average was found to be 3,144 square feet; the distribution of sample data is shown on Figure 3. 3 The estimated ERU size was 2,121 in the 2006 stormwater utility study. ---PAGE BREAK--- Offices in Illinois, Iowa, Minnesota, and Wisconsin 2901 International Lane, Suite 300, Madison, WI 53704-3133 (608) 242-7779 (800) 446-0679 FAX: (608) 242-5664 WEB ADDRESS: www.msa-ps.com 3 FIGURE 3. SINGLE FAMILY RESIDENTIAL PARCEL IMPERVIOUS AREA DISTRIBUTION 0 5 10 15 20 25 [PHONE REDACTED]-1249 1250-1499 1500-1749 1750-1999 2000-2249 2250-2499 2500-2749 2750-2999 3000-3249 3250-3499 3500-3749 3750-3999 4000-4249 4250-4499 4500-4749 4750-4999 5000-5249 5250-5499 5500-5749 5750-5999 6000-6249 6250-6499 6500-6749 6750-7000 Parcel Impervious Area (sq. ft.) Number of Parcels (n=157) Each of the 436 parcels identified as duplex or multifamily (multi-family parcel dwelling units ranged from 3 to 260 units per parcel) were evaluated also. The entire set of data related to residential land use was evaluated to determine the ERU size as shown in Table 2. Since the residential parcel analysis shows that the average impervious area of multi-family living units to be substantially less than the average impervious area associated with single-family living units, it is recommended that the City consider charging each multi-family unit a fraction of an ERU. Based on the relative average impervious areas of the three residential property types summarized in Table 1, it was assumed for the purpose of this study that the City will charge 1 ERU for each duplex and single-family living unit, and 0.6 ERUs for each multi-family residential (MFR) living unit. Under this scenario, the total number of residential ERUs Citywide is 6,704, as summarized in Table 2. TABLE 2. RESIDENTIAL ERU SUMMARY Type of Residential Unit Approximate Number of Units Citywide ERUs Per Living Unit Approximate Number of ERUs Citywide Single-Family 3,589 1 3,589 Duplexes 518 1 518 Multi-Family 4,329 0.6 2,597 8,436 6,704 ---PAGE BREAK--- Offices in Illinois, Iowa, Minnesota, and Wisconsin 2901 International Lane, Suite 300, Madison, WI 53704-3133 (608) 242-7779 (800) 446-0679 FAX: (608) 242-5664 WEB ADDRESS: www.msa-ps.com 4 Non-Residential ERU Count The total number of non-residential ERUs in the City was determined by estimating the total non-residential impervious area, and dividing this amount by the estimated ERU size. For the 2006 study, this step was completed using textbook values of average impervious area for typical land uses. For this study these numbers were determined by the following: 1) Assigning a land use classification to all non-residential parcels based on land use (or zoning) information provided by the City. These land uses were then divided into subsets containing land uses with similar impervious area density. 2) Recent aerial photos were evaluated using GIS software, and impervious surfaces were measured on approximately 25% of the non-residential parcels. 3) The average density of impervious areas was determined for each land use and subset. 4) The previous assumptions (2006 study) of 15% impervious for the airport and 0% impervious for vacant parcels was maintained. Using the process described above, it was estimated that there are a total 619.6 acres of taxable, non- residential impervious area and 139.2 acres of tax-exempt non-residential area in the City. Applying an ERU size of 2,106 square feet results in 12,815 and 2,879 non-residential taxable and tax-exempt ERUs, respectively. The total number of ERUs Citywide was estimated to be 22,398 by adding the total number of residential and non-residential ERUs, as summarized in Table 44. TABLE 4: IMPERVIOUS AREA BY PARCEL TYPE SUMMARY Parcel Type Impervious Surface (Acres) # ERUs Single Family Residential 259.0 3,589 Duplex Residential 23.6 518 Multi-Family Residential 125.1 2597 Non-Residential, Taxable 619.6 12,815 Non-Residential, Tax Exempt 139.2 2,879 Total 1134.1 22,398 Estimation of Charges The charge per billing unit in a stormwater utility is determined by dividing the total stormwater program budget by the total number of ERUs in the community. Among Wisconsin municipalities with stormwater utilities, the charge per ERU ranges from $12 to over $100, with the average being approximately $54 annually (see Figure Table 5 presents a range of possible charges and the projected annual revenue for the City of Middleton. 4 The estimated number of ERUs Citywide in the 2006 stormwater utility feasibility study was 23,913. This estimate was developed assuming a flat percent imperviousness by zoning classification for all non-residential parcels. Specifically, the following impervious percentages were assumed for the 2006 study: commercial, 85%; manufacturing, 72%; developed tax-exempt parcels, 60%; airport parcels and Orchid Heights Park, 15%. ---PAGE BREAK--- Offices in Illinois, Iowa, Minnesota, and Wisconsin 2901 International Lane, Suite 300, Madison, WI 53704-3133 (608) 242-7779 (800) 446-0679 FAX: (608) 242-5664 WEB ADDRESS: www.msa-ps.com 5 FIGURE 4: WISCONSIN STORMWATER UTILITY RATES TABLE 5: ESTIMATED REVENUE FOR RANGE OF ERU CHARGE RATES “Typical 10” and “Top 13” Customer Bill Estimates. It is often useful, when considering a stormwater utility, to prepare some sample ‘utility bills’ to determine the impact that creation of a stormwater utility may have on future utility customers. The follow section summarized presents sample bills6 for a selection of non-residential property owners estimated by the City to represent the ‘average’ and largest customers that would exist in a stormwater utilty. The results of this evaluation are summarized in ??Table and are illustrated in the figures attached to the end of this report6. 5 Projected annual revenue rounded to the nearest thousand dollars. 6 The imperious areas and parcel boundaries shown in these figures and summarized in Table 3, were based on the best data available to MSA at this time. We are also aware of some data inconsistencies that we were unable to address due to project scope and budget limitations. For example, the Elm Lawn Elementary School site includes some parcels classified as single- family residential that according to staff, are part of the school site. For the purposes of this study, these parcels were treated as non-residential in the Citywide ERU count, but as non-residential in the “top 7” sites evaluation. Additionally, the school district transportation site appears to be under construction in the most recent available aerial photos (2008 NAIP). Annual Charge per ERU Projected Annual Revenue5 $20 $ 448,000 $35 $ 784,000 $50 $1,120,000 $65 $ 1,456,000 $80 $ 1,792,000 $0 $20 $40 $60 $80 $100 $120 Lake Delton Watertown Grantsburg River Falls Barron Chetek New Richmond Janesville Madison Chippewa Falls Sheboygan Glendale Wauwatosa Howard Madison Baraboo Eau Claire Weston Washburn Bellevue Cudahy Grand Chute St. Francis Oshkosh Poynette Fitchburg Green Bay Neenah Monroe Racine West Allis Greenville New Berlin Sussex Sun Prairie Monona Butler Superior Waupon Milwaukee Brown Deer Harrison Little Chute Garner's Creek Appleton Shoerwood Hills Annual Charge Per ERU State Average $54/year ---PAGE BREAK--- Site Name: Middleton Community Bank Site Area: 1.0 Acres Impervious Area: 0.89 Acres Estimated ERUs: 18.4 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area 0 50 25 Feet Typical 10 Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: Middleton Glen Site Area: 4.9 Acres Impervious Area: 2.21 Acres Estimated ERUs: 45.8 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area 0 100 50 Feet Typical 10 Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: Kelley Williamson Site Area: 1.9 Acres Impervious Area: 1.3 Acres Estimated ERUs: 26.9 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area 0 50 25 Feet Typical 10 Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: X-S Night Club Site Area: 1.9 Acres Impervious Area: 1.48 Acres Estimated ERUs: 30.7 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area 0 75 37.5 Feet Typical 10 Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints The Dane County building footprint shapefile was utilized in place of operator digitizing from the 2005 Orthophoto for all impervious building areas. The building footprint shapefile was created from photo diapositives digitally scanned at 15 microns and photogrammetrically processed to produce the final imagery and products. ---PAGE BREAK--- Site Name: Keva Sports Center Site Area: 4.9 Acres Impervious Area: 2.63 Acres Estimated ERUs: 54.4 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area 0 100 50 Feet Typical 10 Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints The Dane County building footprint shapefile was utilized in place of operator digitizing from the 2005 Orthophoto for all impervious building areas. The building footprint shapefile was created from photo diapositives digitally scanned at 15 microns and photogrammetrically processed to produce the final imagery and products. ---PAGE BREAK--- Site Name: Fairfield Inn Site Area: 2.6 Acres Impervious Area: 1.47 Acres Estimated ERUs: 30.4 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area 0 75 37.5 Feet Typical 10 Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: Denny's Site Area: 1.2 Acres Impervious Area: 0.92 Acres Estimated ERUs: 19.0 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area 0 50 25 Feet Typical 10 Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: St. Bernard's Church Site Area: 4.9 Acres Impervious Area: 3.52 Acres Estimated ERUs: 72.8 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area 0 100 50 Feet Typical 10 Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: Middleton Ford Site Area: 8.6 Acres Impervious Area: 6.94 Acres Estimated ERUs: 143.6 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area 0 150 75 Feet Typical 10 Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: Soft Switch Technology Site Area: 5.3 Acres Impervious Area: 3.82 Acres Estimated ERUs: 78.9 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area 0 100 50 Feet Typical 10 Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: ETC Site Area: 42.9 Acres Impervious Area: 15.65 Acres Estimated ERUs: 323.8 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 250 125 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: Ray-O-Vac Site Area: 15.6 Acres Impervious Area: 8.53 Acres Estimated ERUs: 176.5 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 150 75 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints The Dane County building footprint shapefile was utilized in place of operator digitizing from the 2005 Orthophoto for all impervious building areas. The building footprint shapefile was created from photo diapositives digitally scanned at 15 microns and photogrammetrically processed to produce the final imagery and products. ---PAGE BREAK--- Site Name: Pleasant Company Site Area: 54.8 Acres Impervious Area: 24.94 Acres Estimated ERUs: 515.9 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 300 150 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints The Dane County building footprint shapefile was utilized in place of operator digitizing from the 2005 Orthophoto for all impervious building areas. The building footprint shapefile was created from photo diapositives digitally scanned at 15 microns and photogrammetrically processed to produce the final imagery and products. ---PAGE BREAK--- Site Name: Gilson Medical Site Area: 14.2 Acres Impervious Area: 9.67 Acres Estimated ERUs: 200.1 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 200 100 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: Springs Industries Site Area: 27.9 Acres Impervious Area: 17.15 Acres Estimated ERUs: 354.7 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 250 125 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints The Dane County building footprint shapefile was utilized in place of operator digitizing from the 2005 Orthophoto for all impervious building areas. The building footprint shapefile was created from photo diapositives digitally scanned at 15 microns and photogrammetrically processed to produce the final imagery and products. ---PAGE BREAK--- Site Name: Greenway Station Site Area: 40.8 Acres Impervious Area: 29.70 Acres Estimated ERUs: 614.4 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 250 125 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: School District - Administrative Center Site Area: 4.1 Acres Impervious Area: 1.22 Acres Estimated ERUs: 25.2 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 75 37.5 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints The Dane County building footprint shapefile was utilized in place of operator digitizing from the 2005 Orthophoto for all impervious building areas. The building footprint shapefile was created from photo diapositives digitally scanned at 15 microns and photogrammetrically processed to produce the final imagery and products. ---PAGE BREAK--- Site Name: School District - E.G. Kromrey Middle School Site Area: 48.8 Acres Impervious Area: 15.33 Acres Estimated ERUs: 317.2 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints 0 250 125 Feet MSA attempted to divide contiguous parcels associated with Middleton High School, Middle School, and Alternative School into three individual sites, based on each parcel's mailing address in the City assesor database. However, due to expected shared-use by each school it is possible that the ulitimate division of impervious area may be different than this interpretation. ---PAGE BREAK--- Site Name: School District - Elm Lawn Elementary School Site Site Area: 11.8 Acres Impervious Area: 4.48 Acres Estimated ERUs: 92.7 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 150 75 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints The Elm Lawn School site includes some parcels classified as single-family residential. According to City staff, these residential parcels are part of this site. For the purpose of this study, these parcels were treated as non-residential for in the “top 7” sites evaluation, and included as part of the total amount impervious area of this site. ---PAGE BREAK--- Site Name: School District - Middleton Alternative High School Site Area: 19.6 Acres Impervious Area: 1.89 Acres Estimated ERUs: 39.0 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 200 100 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints MSA attempted to divide contiguous parcels associated with Middleton High School, Middle School, and Alternative School into three individual sites, based on each parcel's mailing address in the City assesor database. However, due to expected shared-use by each school it is possible that the ulitimate division of impervious area may be different than this interpretation. ---PAGE BREAK--- Impervious extends outside of parcel per City staff. Site Name: School District - Middleton High School Site Area: 10.0 Acres Impervious Area: 8.01 Acres Estimated ERUs: 165.7 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 100 50 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints MSA attempted to divide contiguous parcels associated with Middleton High School, Middle School, and Alternative School into three individual sites, based on each parcel's mailing address in the City assesor database. However, due to expected shared-use by each school it is possible that the ulitimate division of impervious area may be different than this interpretation. ---PAGE BREAK--- Site Name: School District - Northside Elementary School Site Area: 12.4 Acres Impervious Area: 4.02 Acres Estimated ERUs: 83.2 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 150 75 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints ---PAGE BREAK--- Site Name: School District - Sauk Trail Elementary School Site Area: 10.8 Acres Impervious Area: 2.62 Acres Estimated ERUs: 54.2 Middleton, WI Stormwater Utility Feasibility Study Legend Parcel Boundary Impervious Area Top Customer Bill Estimates 0 150 75 Feet Sources - 2009 Dane County Parcels - 2005 Dane County Orthophoto - 2008 NAIP Orthophoto - Dane County Building Footprints Impervious areas located outside of the site boundaries provided by City staff were not included.