Drainage improvements shall include all storm sewers, ponding areas, ditches, groundwater control systems, or other installations for the control of storm water or groundwater.
(A) Standards. Drainage improvements shall be made to serve current and projected land use. All improvements for carrying water shall provide protection based on a design frequency of at least five years, or higher if requested by the engineer or benefitted owners. Storage sites and ponding areas shall be designed to provide a frequency of protection designated by the engineer, but in no case shall the design allow damage to permanent structures at frequencies less than 50 years.
(B) Assessment formula. The assessments to be levied against properties within an area benefitted by subsurface improvements shall be distributed based on the following provisions:
(1) The "assessable unit" to be applied to drainage improvements shall be "area" expressed in terms of square feet times a land use multiplier.
(2) The "assessment rate" to be applied against all properties and each individual property shall be equal to the "assessable cost" of the project divided by the total number of assessable units benefitted by the improvement. Drainage districts shall be established by the engineer along the boundaries of the area which will ultimately be served by the system.
(3) The total number of assessment units shall be computed using the following table of land use multipliers:
Land Use Multiplier
Regulated Flood Plain 0
(No occupancy permitted)
Planned Open Space 0.75
(Parks, golf courses, cemeteries, etc.)
Single-Family Residential 1.00
Multiple-Dwelling Residential
and Institutional 1.250
Commercial and Industrial 1.500
(4) Storm sewer costs shall be distributed on the basis of land use at the time of the project. Provided, however that if the land is vacant and is located in an otherwise developed area of the city at the time of the project, the costs shall be distributed on the basis of the existing zoning district. Provided further, that if the land is being used as agricultural at the time of the project, or is vacant and is located in an otherwise undeveloped area of the city at the time of the project, the cost shall be distributed on the basis of the city's future land use designation. Thereafter if a change in zoning is requested which would place the property in a more intense land use category, an accompanying fee may be collected equal to the difference in land use factors and the fees used to offset the costs of upgrading drainage facilities to accommodate the increased runoff caused by higher type development. Requests for rebates due to rezoning resulting in a lower land use multiplier will not be allowed since the facilities previously assessed were designed based on the higher need. (Ord. 608, eff. 7-9-79)
(5) Where portions of a drainage system are designed for frequencies greater than the standard requires, the additional cost of such extra capacity shall be assessed to the area provided extra protection by the increased capacity.
(6) The total assessment for all drainage improvements shall not exceed $0.03 per square foot for residential property, based on 1975 costs. Other property shall have total assessment not greater than this limit times the appropriate multiplier. Total costs in excess of this limit shall be paid from general municipal funds. Credit shall be given for any drainage assessment of record. The upper limit may be modified using the Engineering-News-Record (ENR) index, assuming a July, 1975, ENR index of 2248.
(Ord. 540, eff. 10-14-75)