§ 9.5.0. CALCULATION OF THE DRAINAGE CHARGE

9.5.1 Sections 15-2-5 and 15-2-7 of the Austin City Code define how impervious cover and the monthly drainage charge shall be calculated.

9.5.2 Base Rate - The annual base rate shall be in the fee schedule approved by City Council for each fiscal year. The monthly base rate is determined by dividing the annual base rate by 12.

9.5.3 Adjustment Factor - The adjustment factor formula shall be in the fee schedule approved by City Council for each fiscal year.

9.5.4 Total Area of a benefitted property - The total area of a property shall be initially determined by the City's Geographic Information System (GIS) which uses parcel data from Travis Central Appraisal District (TCAD), Williamson County Appraisal District (WCAD), and Hays County Appraisal District (HCAD). The total area of a property may be corrected by the following sources:

A.

A survey that is signed and sealed by a State of Texas Professional Land Surveyor,

B.

The dimensions on an approved site development plan,

C.

The dimensions on an approved subdivision plat,

D.

The dimensions shown on an as-built plan, or

E.

The dimensions obtained from tax records of the County Appraisal District in which the property is located.

If numbers from different sources are inconsistent, City staff may use the latest and most accurate source to make the determination.

9.5.5 Impervious Area - Impervious area (also called impervious cover) is defined by City Code Sections 15-2-1 (B) (4), 15-2-5, 25-8-63, and Environmental Criteria Manual Section 1.8.1.

A.

Measurement - Impervious area shall be measured by the City's Geographic Information System (GIS) when calculated from the City's latest planimetric maps. Measurement of impervious area for the purpose of calculating the drainage fee shall conform to the methods and standards specified in the City's Environmental Criteria Manual, the City's Drainage Criteria Manual, and the City's Land Development Code as it is interpreted by the City's Watershed Protection and Development Services Department (or successor department) staff.

B.

Additional Detail

a.

Structures - The impervious area for structures shall be determined by whichever of the following is larger - the roof area, the foundation area, or exterior wall area. Consequently, horizontal projections of the overhang of a house (eaves for example) are considered impervious area.

b.

Sidewalks/Trails - Sidewalks and trails that are accessible by the general public and are located on public property or on public easements shall not be counted as impervious cover.

c.

Roads/Driveways/Parking Areas - Partially paved vehicular areas constructed with pervious areas (e.g. concrete strips with a pervious median) may have the pervious area removed from the impervious cover quantity if there is clear evidence of focused use on the paved areas. Unpaved vehicular areas compacted by vehicle use may have the uncompacted, pervious areas removed from the impervious cover quantity only if there is clear evidence of focused use on the wheel track area. In cases where ungrouted stones/bricks/pavers are placed adjacent to each other (gaps<1"), the requirements below for permeable pavers and porous pavement must be met to receive a reduction in impervious cover. For vehicular areas with both impervious and pervious features, City staff may assign the entire area as 50% impervious or specifically delineate the impervious areas.

d.

Pedestrian Patios/Walkways - For all pedestrian patio or walkway uses where there are bricks, stones, or other impervious features spread over an area, when the pervious space between the impervious features is greater than 50%, the entire area may be considered pervious. When the pervious space between the impervious features is less than 50%, the entire area may be considered as 50% impervious. In cases where ungrouted stones/bricks/pavers are placed adjacent to each other (gaps < 1"), the requirements below for permeable pavers and porous pavement must be met to receive a reduction in impervious cover.

e.

Permeable Pavers and Porous Pavement - In order to exclude permeable pavers or porous pavement from impervious cover, the customer will need to provide plans, specifications, details, or other information that clearly demonstrates the installation met City of Austin permeability requirements at the time of construction. If sufficient proof is provided, the area may be considered fully pervious for pedestrian applications and 50% pervious for vehicular applications.

f.

Easements: For purposes of calculation of the drainage charge, no adjustments to the impervious cover shall be made due to any easement on the property or adjacent to the property, regardless of the nature of the easement. The City shall neither add the adjacent easement to the property area nor remove any existing easement on the property from calculation of impervious cover for the purpose of determining the drainage charge.

C.

Corrections - The impervious area of a property may be corrected by the following sources, any of which may be collected and submitted by the utility customer at his/her initiative:

a.

Latest available aerial photographs or planimetric data.

b.

An up-to-date survey that is signed and sealed by a State of Texas Professional Land Surveyor.

c.

A site plan or similar development documents that accurately reflect the development currently on the property.

d.

Measurements and observations from a field check by City staff.

e.

Photographs that show conditions different from those on which the original calculations were based (e.g., uncovered wood decks, wheelchair ramps, removed structures, misinterpreted features).

f.

More detailed information provided by requestor after review and approval by staff.

D.

Drainage Discount - City code 15-2-7 part C allows the Watershed Protection Department (WPD) to set up a discount for those who have stormwater control measures (SCM) on their property that exceed the legal requirements for development.

a.

Applicability/Eligibility.

1.

Applicants must be a current drainage utility customer or a tenant of the benefitted property.

i.

A tenant, who is not a current drainage utility customer, may apply for the SCM discount on behalf of the drainage utility customer for the benefitted property. However, WPD cannot disclose the account information concerning the benefitted property to the tenant. The discount will be applied to the drainage utility customer for the benefitted property.

2.

If any permit or approval for SCM is required by governmental code, the applicant must show evidence of approval.

3.

Other governmental agreements, such as Planned Unit Developments (PUD) or Variances, are considered legal requirements for development and thus SCMs developed as part of these agreements are not considered eligible for a discount.

4.

The SCM must exceed the legal requirements for development of the benefitted property. For SCMs developed to meet legal requirements, but also exceed requirements, the amount of volume that exceeds the legal requirements must be clearly documented and calculations provided showing the excess. For SCMs that required a Professional Engineer (PE) seal to construct, a PE seal with supporting calculations are also required to demonstrate the excess amount.

b.

Types of Controls.

1.

SCMs must be present in Drainage Criteria Manual or Environmental Criteria Manual in order to be eligible for discount.

c.

Calculation.

1.

If the SCM is installed at a property that is associated with only one DUF account, the discount will be applied to the account holder for the benefitted property.

2.

If multiple DUF accounts are associated with a property (as in a duplex), the discount will be applied to the customer(s) that own, operate and maintain the SCM. If multiple DUF accounts are associated with the SCM, the City shall determine an equitable allocation of the discount.

3.

The amount of the discount will be limited to the impervious surface area that is mitigated by the SCM.

4.

Amount of discount cannot result in a negative DUF charge.

d.

Inspection and Maintenance.

1.

Customers receiving discount must service and maintain SCM in order to retain discount.

2.

To maintain the discount, customer shall allow WPD to perform on-site inspection, if requested, to verify SCM is well-maintained and functioning as designed.

3.

Information found to be inaccurate may result in loss of discount or back debit.

e.

Timeline.

1.

Discount is valid for two years starting on date of approval. To renew discount, customer must complete renewal process.

2.

If SCM (e.g., rain barrel) is moved to a different benefitted property, customer must reapply for discount.

9.5.6 Calculating Properties on a Composite Basis - Under Section 15-2-5(C), the percentage impervious cover may be calculated on a composite basis under certain circumstances, as prescribed in this Section.

A.

A "condominium regime" as defined by City and State Codes.

B.

The properties are subject to a unified development agreement or City site plan that specifies the properties will be reviewed as one site.

C.

The customer provides documentation acceptable to the Director indicating that the properties were legally developed together.

D.

If a building spans one or more parcel boundaries, initial billing assignments may assume these parcels were legally developed together.

1.

Same Owner- In addition to combining the charge, the bill will also be combined.

2.

Different Owners (e.g. townhomes) - The calculation of the charge may be combined. The charge should be assessed to the home owners association (HOA) if the HOA has an account; otherwise the charge may be divided equally among the owners.

E.

Examples:

1.

Adjacent Parcels, Same Owner - Unless legally developed together or as noted below, if two or more parcels are adjacent and have the same owner, the charge is calculated and assessed separately for each parcel.

a)

Even though separate charges may be assessed for multiple parcels of the same owner, that same owner may have those separate parcel charges placed on a single bill.

2.

Adjacent Parcels, Multiple Owners, One Address - When there are multiple parcels with multiple owners, but all at one address, the charge is calculated and assessed separately for each parcel. City will attempt to place additional address points, if appropriate.

3.

Multiple Parcels, legally developed together, different owners, and one existing Drainage Utility Fee (DUF) account - WPD will maintain one account unless requested by all the owners to change.

4.

Duplexes, Triplexes, and Fourplexes - If there are 2-lot duplexes or other multi-lot examples up to fourplexes, they shall be combined together into one parcel for calculating the charge.

5.

Non-adjacent Parcels - These shall not be combined for the purpose of calculating the drainage charge unless the parcels were legally developed together as one site and subsequently separated by public right-of-way. Subdivision of undeveloped parcels retained by the same owner does not constitute development together as one site.

6.

Parcels within a Parcel - Parcels that are wholly enveloped by another parcel may be calculated on a composite basis.

7.

Private Drives/Streets-These are not exempt like public ROW and will receive a drainage charge. If the private drives are separate parcels, they will not be combined with other parcels, unless those parcels all have the same owner and were legally developed together.

Source: Rule No. 161-15.22, 4-27-16 ; Rule No. 161-17.02 , 3-2-17; Rule No. 161-18.15 , 9-6-2018.