WPRF Rate Information

The calculations for the Watershed Protection and Restoration Fee (WPRF), also known as the stormwater fee, vary by property type. Depending on the property type, the fee will either be calculated using the amount of impervious surface on the property or will be a flat rate.

Equivalent Residential Unit (ERU) Base Rate:

An Equivalent Residential Unit (ERU) is the base unit for calculating the annual charge for residential and non-residential properties. The Department of Public Works utilized Geographic Information Systems (GIS) technology along with parcel data collected from the Consolidated Property File and County Zoning Maps to estimate the imperviousness of residential properties in the various zoning districts. This information was then used to determine a baseline ERU of impervious surface of 2,940 square feet, which represents the median amount of impervious surface for properties in residential zones R1, R2, and R5. The base rate is currently $98.40 per ERU of impervious surface. 

Impervious Surface:

An impervious surface is defined as a surface that does not allow stormwater to infiltrate. This includes but is not limited to rooftops, sidewalks, roads, driveways, pavement, compacted gravel, and swimming pools. For billing codes that incorporate a property’s impervious surface amount in the WPRF calculations, you can view the impervious surface used for a specific property in the Watershed Protection & Restoration Fee Viewer.

Billing Code:

To determine which property type you are being billed as, use the Watershed Protection & Restoration Fee Viewer or check the code listed for this line item on your real property tax bill. The code will start with “WPRF” and will be followed by a two-digit number. See below for information on how the fee is calculated for each code type.

Exemptions:

The WPRF applies to all properties that contain impervious surfaces, whether or not there are any structures on the property. The only exceptions to this rule are real property owned by the State, a unit of State government, a county, a municipality, or a veterans’ organization that is exempt from taxation under 501(c)(4) or (19) of the Internal Revenue Code, or a regularly organized volunteer fire department that is used for public purposes.

Contact Us:

For questions regarding your property’s WPRF, contact us at 410-222-7536 or wprf@aacounty.org. 

wprf charge codes and fee calculations:

Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Residential Property

Zoned RA, RLD

$196.80

(2 x Base Rate)

STORMWATER/WPRF-TIER1

(WPRF01)

WPRF01 is used for a residential property in residential zoning district RA or RLD that is improved with a detached single-family dwelling. The WPRF is determined by a property’s estimated amount of impervious surface area. Residential properties are divided into separate billing tiers and represent zoning districts with an estimated impervious area that is less than, equal to or greater than the base ERU of 2,940 square feet.
Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Residential Property

R1, R2, R5

$98.40

(Base Rate)

STORMWATER/WPRF-TIER2

(WPRF02)

WPRF02 is used for a residential property in residential zoning district R1, R2, or R5 that is improved with a detached single-family dwelling. The WPRF is determined by a property’s estimated amount of impervious surface area. Residential properties are divided into separate billing tiers and represent zoning districts with an estimated impervious area that is less than, equal to or greater than the base ERU of 2,940 square feet.
Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Residential Property

R10, R15, R22

$39.36

(0.4 X Base Rate)

STORMWATER/WPRF-TIER3

(WPRF03)

WPRF03 is used for a residential property in residential zoning district R10, R15, or R22 that is improved with an attached dwelling or a detached single-family dwelling or a residential property in residential zoning district RA, RLD, R1, R2 or R5 that is improved with an attached dwelling. The WPRF is determined by a property’s estimated amount of impervious surface area. Residential properties are divided into separate billing tiers and represent zoning districts with an estimated impervious area that is less than, equal to or greater than the base ERU of 2,940 square feet.
Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Farm Property

$39.36

(0.4 X Base Rate)

STORMWATER/WPRF-FARM

(WPRF04)

Farms are entitled to a reduced rate for their WPRF. For the purposes of the WPRF, a farm is defined as a property, or contiguous properties under the same ownership, with or without buildings, that is used for cultivating and managing the soil for composting, growing, harvesting, and selling of crops or the products of forestry, horticulture or hydroponics; processing agricultural products, regardless of whether there is a change in natural state of the product; breeding, raising, or managing livestock, including horses, cattle, poultry, fish, game, bees, or fur-bearing animals; dairying; or equestrian activities and events not conducted under a license issued by the State Racing Commission.
Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Mobile Home Park

# of spaces x 0.4 x Base Rate

STORMWATER/WPRF-MOBILE HM PK 

(WPRF05)

Mobile home parks are billed based on the number of spaces rather than the specific amount of impervious area on the site. Each mobile home park space is billed the same rate as a Tier 3 Residential Property.
  • Property/BillingFee Calculation

    Tax Bill Appearance

    (Code)

    		Code Description

    Non-Residential Religious Organization

    $1 Flat Rate

    STORMWATER/WPRF-RELIG ORG

    (WPRF07)

    Properties that are owned by a religious group or organization are entitled to a reduced rate for their WPRF if they meet certain criteria. These criteria are:

    • The organization is certified under § 501(c)(3) or (d) of the Internal Revenue Code
    • The property is exempt from real property tax under the Tax-Property Article of the State Code
Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Private Academic School

$196.80

(2 x Base Rate)

 

STORMWATER/WPRF-PVT SCHOOL

(WPRF08)

The WPRF legislation establishes a reduced rate for properties that are owned by private academic schools. For the purposes of the WPRF, private academic schools are defined as private institutions that offer an academic course of instruction and that are operated by a religious organization or under a certificate of approval by the State Department of Education.
Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Private Road

not HOA-owned

$98.40

(Base Rate)

STORMWATER/WPRF-PVT ROAD 

(WPRF09)

This billing code is used for private roads that have separate tax account numbers and are not owned by a Homeowners Association. If the private road is owned by a Homeowners Association, the tax account will be billed using code WPRF16.

Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Airport Private

$196.80

(2 x Base Rate)

 

STORMWATER/WPRF-PVT AIRPORT

(WPRF10)

The WPRF legislation establishes a reduced rate for properties that are operated as private airfields or airports.
Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Standard Marina

(<7.5 impervious acres)

(ERU x Base Rate)

STORMWATER/WPRF-MARINA STD 

(WPRF11)

The WPRF is determined by a property’s estimated amount of impervious surface area. 

Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Large Marina (7.5+ impervious acres)

ERU x Base Rate

+ any acres +7.5 = .25 x Base Rate

STORMWATER/WPRF-MARINA LG 

(WPRF12)

The WPRF legislation establishes a reduced rate for any impervious area within a marina beyond the first 7.5 acres of impervious if the marina is in good standing with the Maryland Department of Natural Resources Clean Marina Initiative.
Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Non-Residential Charitable

 

$1 flat for 501 (c) (3) or (d) org.

 

STORMWATER/WPRF-CHAR ORG NON RES 

(WPRF14)

Properties that are owned by a nonprofit organization are entitled to a reduced rate for their WPRF if they meet certain criteria. These criteria are:

 

  • The organization is certified under § 501(c)(3) or (d) of the Internal Revenue Code
  • The property is exempt from real property tax under the Tax-Property Article of the State Code

 

Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

NPDES Permit Holder

ERU x Base Rate x 0.3

STORMWATER/WPRF-NPDES PERMIT 

(WPRF15)

The WPRF legislation establishes a reduced rate for nonresidential properties that are subject to a National Pollutant Discharge Elimination System (NPDES) Permit including stormwater management controls. Typically properties covered under either “GENERAL PERMIT FOR DISCHARGES FROM STORMWATER ASSOCIATED WITH INDUSTRIAL ACTIVITIES -DISCHARGE PERMIT NO. 12-SW” or “GENERAL PERMIT FOR DISCHARGES FROM MARINAS INCLUDING BOAT YARDS AND YACHT BASINS - DISCHARGE PERMIT NO. 10-MA” would meet these criteria.
Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Homeowners Association

ERU x Base Rate

not to exceed # of properties x $39.36

 

STORMWATER/WPRF-HOA 

(WPRF16)

The WPRF legislation establishes a cap on the total WPRF amount across all tax accounts owned by the same HOA. If the total WPRF for all tax accounts owned by an HOA exceeds this cap, the HOA is billed the cap amount. If the total does not exceed this cap, the HOA is billed the amount calculated using the above formula. If an HOA has an approved WPRF credit, the credit will be applied to the fee amount after the cap has been applied.

WPRF Cap = # of property tax accounts for homes and unimproved lots within the boundaries of the HOA x Base Rate x 0.4.

Note that unimproved lots are considered to be lots with their own separate tax account number on which a residential dwelling is allowed to be built, regardless of whether it has been built yet or not, and that the number of property tax accounts used in this equation does not include property tax accounts owned by the HOA.

For purposes of the WPRF, an HOA is defined as an incorporated or unincorporated homeowners association, civic or community association, council of condominium unit owners, or similar entity.

Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Multifamily Dwelling

ERU x Base Rate x 0.4

STORMWATER/WPRF-MULTIFAMILY 

(WPRF17)

For purposes of the WPRF, a multifamily residential property is defined as real property located in any zoning district that is improved by a structure that is not a duplex, semi- detached, or townhouse structure and that contains three or more units located back to back, adjacent to each other, or one on top of the other.

For a multifamily dwelling that is a condominium, see WPRF19.

Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Residential Condo Garden / High Rise

ERU x Base Rate x 0.4 / # of units

 

STORMWATER/WPRF-RES CONDO 

(WPRF19)

This code is used to calculate the WPRF for multifamily residential properties that are classified as condominiums. As the condominium dwelling units located on a property have individual owners, each of the dwelling unit tax accounts is billed separately. For this reason, the WPRF for each of these units is calculated using the property’s total impervious area divided by the number of units.

Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Residential Property in non-residential zone

ERU x Base Rate

(capped at Base Rate)

STORMWATER/WPRF-NRZN 

(WPRF20)

This code is used to calculate the WPRF for residential properties that are located in a non-residential zone (Commercial, Industrial, Maritime, Mixed Use, Odenton Growth Management Area, Open Space, Town Center, or Small Business Zoning District). The Stormwater Fee Viewer can be used to look up your property’s zoning district.

Properties coded as WPRF20 have their WPRF capped at the Base Rate, which is the WPRF flat-rate charge for a Tier 2 Residential Property (WPRF02). 

To qualify for this code, the property must be improved solely by an attached dwelling or a detached single family dwelling, including accessory structures, and be used solely as the primary residence of the property owner. If the property does not meet these qualifications, the property will be billed as WPRF21.

Property/BillingFee Calculation

Tax Bill Appearance

(Code)

Code Description

Residential Condo Garden / High Rise

ERU x Base Rate

STORMWATER/WPRF-NON RES 

(WPRF 21)

This code is used for non-residential properties that do not fit into any of the more specific categories above. It consists of real property located in non-residential zoning districts, including residential properties that do not meet the WPRF20 qualifications, and real property located in residential zoning districts with a use other than a dwelling.  

For tax accounts coded as WPRF21, their WPRF is capped at 25% of the account’s State and County real property tax assessment prior to any tax credits, deferrals, or exemptions.