(A) Determining the REF.
(1) The accumulated direct runoff (Q) used to determine the REFs shall be calculated based on an evaluation of the land use and application of a standardized soil type and rainfall event.
(2) The calculated direct runoff (Q) shall be based on the runoff equation in the Natural Resources Conservation Service (NRCS) National Engineering Handbook, Part 630 - Hydrology, Chapter 10 - Estimation of Direct Runoff from Storm Rainfall. The equation is as follows:
Q = (P - 0.2S)2
P + 0.8S
Where:
S = (1000/CN) - 10
P = 2.0 inches (Based on a 24-hour two-inch rainfall event)
CN = Runoff index (Based on the land use and the Natural Resources Conservation Services; NRCS Type B soils)
(3) (a) The runoff indices (CN) and REFs for the various land uses within the city shall be set forth in the table below:
Land Use | Runoff Index (CN) | REF |
Land Use | Runoff Index (CN) | REF |
Agricultural | Exempt | Exempt |
Airport Hangers | 85 | 2.72 |
Commercial | 92 | 4.23 |
Industrial | 88 | 3.30 |
Institutional | 88 | 3.30 |
Lakes/Streams/Wetlands | Exempt | Exempt |
Multi-Family | 85 | 2.70 |
Municipal | Exempt | Exempt |
Parks/Cemetery | Exempt | Exempt |
Public-Government | 92 | 4.23 |
Railroad | 88 | 3.30 |
Residential | 72 | 1.00 |
Road right-of-way | Exempt | Exempt |
(b) The REF for land uses not list above shall be determined by the city based on probable hydrologic response.
(B) Establishing unit rates. The City Commission shall from time to time, by resolution, establish the unit rate for each REF. The unit rate so established shall be on file with the City Administrator/Clerk and shall be used to compute the charges for a given parcel of land based on the following formula:
Storm Water Charges = (UR) x (REF) x (SA)
(C) Standardized charges. The following rules shall apply for the purpose of simplifying and equalizing charges: A standard surface area of 0.32 acres shall be used for residential parcels.
(D) Vacant parcels. Land use vacant parcels shall be charged one-half the amount of non-vacant parcels in that land use category.
(Ord. 115, passed 10-14-2014)