How the WQPC is calculated
The Water Quality Protection Charge (WQPC) is determined by two factors:
- What type of property you own
- How much impervious surface area is on your property
Rate for Levy Year 2024
1 ERU = 2,406 square feet = $136.50
for July 1, 2024 through June 30, 2025
The WQPC is determined with this formula
Water Quality Protection Charge for a property = (Total square feet of impervious area / ERU) * Rate
| Tier | Square feet of impervious surface | Charge amount per tax year |
|---|---|---|
| Tier 1 | <=1,000 | $45.05 |
| Tier 2 | >1,000 and <=1,410 | $68.25 |
| Tier 3 | >1,410 and <=3,412 | $136.50 |
| Tier 4 | >3,412 and <=3,810 | $204.50 |
| Tier 5 | >3,810 and <=5,815 | $273.00 |
| Tier 6 | >5,815 and <=6,215 | $341.25 |
| Tier 7 | >6,215 | $409.50 |
| Tier | Square feet of impervious surface | Charge amount per tax year |
|---|---|---|
| Tier 1 | <=6,910 | No more than $204.75 |
| Tier 2 | >6,910 and <=54,455 | No more than $1,228.50 |
| Tier 3 | >54,455 | No more than $3,139.50 |
Most property types are subject to the WQPC
The WQPC applies to these property types:
- Single family homes, including detached houses and townhomes
- Multifamily residences, including condos
- Nonresidential properties, including businesses, office buildings and religious institutions
- Agricultural properties
- Properties owned by 501(c)(3) organizations
Applicable state law only exempts property that is owned by a local government, a volunteer fire department, or by the state government (see Section 4-202-1 (e) (2) of the Environment Article of the Maryland Code). All other properties, whether residential or nonresidential, are subject to the Charge under Section 19-35 of the County Code.
The calculation uses the total impervious surface on your property
Impervious surface data was gathered from imagery through geographic information systems (GIS) available from Montgomery County and the Maryland-National Capital Park and Planning Commission.
These surfaces are included in the WQPC
- Building area
- Patio area
- Attached or detached garage building area
- Walkways
- Driveways
- Basketball/tennis courts
- Private parking lots
- Other paved areas, such as concrete or asphalt
These surfaces are not included in the WQPC
- Gardens, grass, and wooded areas
- Front porches
- Pools
- Public sidewalks
- Wooden decks
- Agricultural business buildings such as barns or silos
- Agricultural driveways or walkways
Agricultural properties: additional surfaces not included in the WQPC
- Patio of the residence
- Detached garage of the residence
- Driveway of the residence
- Basketball/tennis courts
- Other paved areas, such as concrete or asphalt
For determining impervious surfaces, we follow the definitions in the Stormwater Design Manual published by the Maryland Department of the Environment.
Driveways
Permeable pavement and risers are included as part of impervious surfaces because they were developed land. However, property owners can use these stormwater treatment devices to apply for credit (or reduction) off the WQPC.
Brick surfaces, and gravel surfaces used by vehicles or heavy machinery, are also impervious. The Stormwater Design Manual relies on studies showing that gravel and dirt areas used for vehicle access or parking have diminished moisture holding capacity and display drainage characteristics similar to asphalt or concrete. Compaction of the gravel, and the soil underneath it, significantly reduces its permeability compared to natural permeable surfaces. Therefore, even though the gravel would seem to be pervious, it actually becomes impervious.
See Stormwater Design Manual Appendix D.4 for more on driveway and roadway imperviousness.
Pools
Only the paved areas around the pool, such as the patio, are included in the WQPC. The area of a pool containing water is not included in the WQPC calculations.