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Stormwater Fee Calculation


The Districts Stormwater Fee will be based on Customer Classes, which describe the nature and use of properties. Individual properties can be calculated here.

Land Use Codes (“LUC”s) are assigned to a property by the both the County of Sacramento and the County of Sutter Assessor’s Offices and describe the current utilization of a parcel. There are 628 unique LUCs assigned to properties within the District’s boundary. These LUCs are grouped and assigned into the Customer Classes and the associated parcel counts are shown in the table below.

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Different properties will generate different amounts of stormwater runoff according to their land use. The calculation of estimated stormwater flows is proposed to be allocated according to the Net Impervious Area (NIA) of each parcel in the District’s boundary. The NIA is calculated by multiplying the gross parcel area by an Impervious Surface Coefficient (ISC). The ISC considers land use and density of use to estimate the relative impervious surfaces for each property. The ISC is a factor used to discount the gross parcel area down to the NIA. For example, a single-family residential parcel with a density of 4 dwelling units per acre is assigned an ISC of .46. This results in the parcel’s gross area being multiplied by .46 to arrive at the NIA, such that a ¼ acre parcel (10,890 SqFt) is multiplied by .46 (which approximates building, driveway, patio, and other hardscapes) to arrive at approximately 5,000 SqFt of NIA. The ISC factors were developed by the State of California Environmental Protection Agency, Office of Environmental Health Hazard Assessment1. The ISC factors used data from selected areas including Sacramento County which enhances the data’s applicability to RD1000. For Customer Classes without a directly matching ISC, the ISC was estimated using comparable data. The listing of Customer Classes and the associated ISCs are shown in the table below.

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Total Cost of Stormwater Services / Total NIA Served (Acres) = $ per NIA (Acre) for the Stormwater Service $3,300,00 / 10,038.73 NIA Acres Served = $328.7267 per NIA Acre for the Stormwater Service


Parcels are assigned to residential and non-residential Customer Classes. The residential land uses were assigned to the single-family or multi-family Customer Classes based on the respective county’s land use codes. For each of the Residential Customer Classes, the Gross Parcel Area is averaged for all parcels within the Customer Class, the appropriate ISC is applied and a rate per parcel, or unit is determined.

The following table provides the revised potential annual rates per Customer Class type.

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All acreage over 10 acres will be multiplied by the Agriculture ISC (0.04) to arrive at the Large SFR parcel’s excess NIA. This excess NIA will be charged according to the Non-Residential Property rate and the resulting amount will be added to the standard SFR rate. There are 24 Large SFR parcels. The excess acreage charge calculation is shown below.

Gross Acres – First 10 SFR Acres = Excess Acres x ISC (0.04) = Excess NIA * Rate per NIA Acre = Excess Acreage charge + SFR Base Rate = Total Charge for Large SFR Parcel

A sample calculation for a 20-acre Large SFR parcel is shown below.

20 Gross Acres – 10 Base SFR Acres = 10 Excess Acres * .04 (ISC) = 0.40 Excess NIA * $328.73 Rate per NIA = $131.49 Excess Acreage Charge + $29.77 SFR Base Rate = $161.26 Total Charge for Large SFR Parcel.

The average NIA (Acres) and average Stormwater Service costs per Customer Class are shown in the table below.

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