HomeMy WebLinkAboutA025 - Council Action Form dated September 12, 2006 ITEM #:
54f
DATE: 09/12/06
COUNCIL ACTION FORM
SUBJECT: WAIVER OF STORM WATER MANAGEMENT DESIGN STANDARDS
FOR WAL-MART'S SUBDIVISION, FIRST ADDITION
BACKGROUND:
On August 22, 2006, the City Council approved the Developer's Agreement for
Wal-Mart's Subdivision, First Addition. The approved Agreement includes the following
provision for storm water management in the proposed subdivision:
"Due to the fact that the City does not want Wal-Mart to excavate a
storm water detention basin in the floodway because of the effect
such basin could have on the drinking water aquifer in that area, the
City has considered the terms of Ordinances 23.103 and 23.407 and
finds the conditions therein satisfied for execution of a waiver of the
existing storm water detention requirements. In executing such
waiver, the City Council will require, as an additional condition, that
Wal-Mart retain and treat up to the initial 1.5 inches of each storm
event from the Site in a manner satisfactory to the City Engineer.
Upon installation of that method of treatment approved by the City
Engineer prior to construction, Wal-Mart shall, on a yearly basis,
certify to the City Engineer that the method of treatment, over the
course of the preceding year, has remained operational and has
operated within the design specifications to treat up to the initial 1.5
inches of each storm event from the Site."
Waiver of Subdivision Requirements. Section 23.103(l) of the Municipal Code
allows the City Council to waive requirements for proposed subdivisions.
Section 23.103 (1). "Where, in the case of a particular subdivision, it can
be shown that strict compliance with the requirements of the Regulations
would result in extraordinary hardship to the Applicant or would prove
inconsistent with the purpose of the Regulations because of unusual
topography or other conditions, the City Council may modify or waive the
requirements of the Regulations so that substantial justice may be done
and the public interest secured provided, however, that such modification
or waiver shall not have the effect of nullifying the intent and purpose of
the Regulations. In no case shall any modification or waiver be more than
necessary to eliminate the hardship or conform to the purpose of the
Regulations. In so granting a modification or waiver, the City Council may
impose such additional conditions as are necessary to secure
substantially the objectives of the requirements so modified or waived."
Storm Water Management Design Standards. Section 23.407(2) of the Municipal
Code requires the following:
Section 23.407(2). "Storm Water Management Design Standards: Storm
water management design shall include grading, facilities for
improvements or some combination thereof, which results in no increase
in the rate of runoff when compared to the undeveloped condition of the
area to be subdivided. The rainfall frequencies that shall be incorporated
in the design of the storm water management system shall include the five
year, ten year, 50 year, and 100 year design storm events. In the case of
major subdivisions, the calculations and design of the storm water
management system shall be prepared by an engineer licensed to
practice in Iowa."
Conditions for Granting of the Waiver. Staff does not support any excavation for a
storm water detention basin to serve the development, which is the normal technique to
meet our storm water management requirements. The City Council, through approval
of the Developer's Agreement for Wal-Mart's Subdivision, First Addition, has agreed to
accept the installation of an improved on-site storm water filtration system, which will be
owned, operated, and maintained by Wal-Mart and provide water quality treatment for
the majority of rainfall events.
This filtration device will not accomplish the "quantity" objectives of Section 23.407 of
the Municipal Code. However, in executing such waiver, the City Council requires in the
Developer's Agreement that a condition is placed upon Wal-Mart to retain and treat up
to the initial 1.5 inches of each storm event from the site in a manner satisfactory to the
City Engineer. It should be remembered that the Municipal Code does not currently
require developers to treat storm water for water "quality" purposes.
Upon installation of that method of treatment approved by the City Engineer prior to
construction, Wal-Mart shall, on a yearly basis, certify to the City Engineer that the
method of treatment, over the course of the preceding year, has remained operational
and has operated within the design specifications to treat up to the initial 1.5 inches of
each storm event from the site.
This tradeoff will allow large flood events to by-pass the filtration system allowing
surface water from upstream to flow through the site. Staff believes that this is a
preferred approach to storing water on-site during floods, which could cause flood water
to back-up upstream, potentially resulting in increased damage to surrounding
properties.
2
ALTERNATIVES:
1. The City Council can approve the waiver of storm water management design
standards for Wal-Mart's Subdivision, First Addition.
2. The City Council can deny the request for a waiver of storm water management
design standards for Wal-Mart's Subdivision, First Addition. (Note that denial of
the request for a waiver would require that the Developer's Agreement for this
subdivision be amended.)
3. The City Council can refer this request back to staff and/or the applicant for
additional information.
MANAGER'S RECOMMENDED ACTION:
Approval of the waiver is consistent with the approved Developer's Agreement for this
subdivision. It should be noted that the granting of this waiver is applicable only to
Wal-Mart as the owner and occupant of the land, as per the Developer's Agreement.
Upon recording of the Final Plat for Wal-Mart's Subdivision, First Addition, the
conditions for approval of the subdivision will be tied to the land. Therefore, it is the
recommendation of the City Manager that the City Council adopt Alternative No. 1,
thereby approving the waiver of storm water management design standards for
Wal-Mart's Subdivision, First Addition.
3