(A) Storm water runoff detention shall be required on low-density single- or two-family residential subdivisions of four or more lots and all medium- and high-density multi-family residential, commercial and industrial development in the city.
(2013 Code, § 28-135)
(B) Design of storm water detention in the city and as regulated in § 8.4 of the Iowa Statewide Urban Design Standards Manual shall be based on the following detention requirements:
(1) Runoff shall be detained from a 100-year storm event with the property in a developed state; and
(2) The release rate from detention shall be based on a rate not to exceed a five-year storm event on the property undeveloped.
(2013 Code, § 28-136)
(C) On any development of one acre or more, storm water detention shall be planned and installed as part of the required Pollution Prevention Plan and as an erosion control device. At no time shall occupancy be granted prior to completion of the detention facility.
(2013 Code, § 28-137)
(D) Any redevelopment of a lot to repair, replace or add-on to the existing improvements, that generate runoff greater that that discharged prior to redevelopment shall require detention. Said detention facilities shall, at a minimum, provide for the increased volume of runoff generated by the redevelopment (preferably for runoff from the whole development), unless the original detention facility was designed for the proposed new redevelopment.
(2013 Code, § 28-138A)
(E) If a developer can demonstrate that detention facilities are unfeasible to construct, the city may grant exception to the detention requirement and said developer shall pay a fee in lieu of constructing storm water detention facilities. The fee shall be based on the type of development/zoning, the runoff coefficient set by the city and a fee of $15,000 per acre prorated by the runoff coefficient. The fee is calculated as follows: category runoff coefficient:
(1) Low-density and single- and two-family residential: $0.40, $6,000 per acre or fraction thereof to be developed;
(2) Medium-high-density and multi-family residential: $0.80, $12,000 per acre or fraction thereof to be developed;
(3) Commercial: $0.90, $13,500 per acre or fraction thereof to be developed; and
(4) Industrial: $0.80, $12,000 per acre or fraction thereof to be developed.
(2013 Code, § 28-138B)
(F) All new medium- and high-density residential, commercial or industrial development shall be required to have storm water detention, unless a building permit was issued prior to this chapter’s passage and publication. Low-density single- and two-family residential subdivisions of four lots or more shall also have detention requirements unless a preliminary plat was approved by the City Council prior to passage and publication of this chapter.
(2013 Code, § 28-139)
(Ord. 14746, passed 9-13-2004; Ord. 14918, passed 4-22-2013)