TRANSMITTAL LETTER FOR BOARD MEETING OF FEBRUARY 4, 2010
COMMITTEE ON STORMWATER MANAGEMENT
Mr. Richard Lanyon, Executive Director
Title
Request for approval to conduct an Economic Impact Study for the Cook County Watershed Management Ordinance
Body
Dear Sir:
Pursuant to the authority for regional stormwater management granted to the District by the Illinois General Assembly under Public Act 93-1049, the District initiated development of the Cook County Watershed Management Ordinance (WMO) in 2007. The draft WMO was released for public review in Fall 2009 and numerous Study Sessions were conducted within the watersheds of Cook County to allow for public comment. The municipal conferences, in conjunction with elected officials of various municipalities, requested the WMO undergo an Economic Impact Study (EIS) prior to its consideration for adoption by the Board of Commissioners. The Engineering Department’s recommendation for the scope of the EIS is provided below. The recommended scope incorporates suggestions made by the municipal conferences at a meeting attended by Commissioners Shore and Majewski on January 6, 2010.
The EIS will include the following components:
Comparison of detention storage for 5 developments
To compare the amount of detention required under the currently effective Sewer Permit Ordinance (SPO) versus the draft WMO, permits representative of the following land uses and parcel sizes will be analyzed: (1) single family residential, 10-15 acres; (2) multi-family residential, 10-15 acres; (3) commercial, 5-30 acres; and (4) industrial, 10-30 acres. A fifth scenario will involve analysis of a “suburban downtown” development sized between 3-5 acres. Analysis will include determination of the required detention volume for each scenario based on the following: (1) current SPO detention methodology, (2) incorporation of Bulletin 70 rainfall data into current methodology and (3) requirements of the draft WMO. Costs for the detention facilities will be developed based on current unit prices for similar facilities. The site plans previously permitted under the SPO will be altered to graphically demonstrate the impacts of the other scenarios. The required detention volume will also be calculated for each site if it were to be built in DuPage, Lake, and Will Counties utilizing the stormwater management ordinances currently effective in those counties.
Comparison of Detailed Watershed Plan (DWP) inundation maps to floodplain maps developed by the Soil Conservation Service (SCS) in the 1970s
Several areas in Cook County where SCS generated floodplain maps in the 1970s will be randomly selected to compare to DWP inundation maps. Exhibits will be prepared to show the extent of changes in the floodplain area as land use and impervious cover have changed over time.
Detailed detention analysis of a small watershed
A small watershed will be analyzed to compare the effects of the detention requirements of the SPO and the draft WMO. A model including detention basins previously permitted under the SPO for a small watershed representative of Cook County will be developed. The detention basins will then be reconfigured to incorporate Bulletin 70 rainfall data. The final scenario will involve reconfiguring the detention basins to meet draft WMO requirements. Downstream damages will be calculated and summarized for all three scenarios.
The advisory committees established for the WMO will be reconvened to review the selected sites, methodology, and the draft study prior to finalization. The first step of the EIS will be to identify the specific sites representative of the above criteria to be examined. The sites selected will be presented to the Board of Commissioners for their approval subsequent to receiving input from the WMO advisory committees and prior to any analysis.
It is anticipated the study will take 6-8 months to complete. A request for authority to retain a consultant to perform the EIS will be forthcoming.
It is therefore requested that the Executive Director recommend to the Board of Commissioners that it approve this request to conduct an EIS for the WMO.
Requested, Joseph P. Sobanski, Director of Engineering, WSS:JPM
Recommended, Richard Lanyon, Executive Director
Respectfully Submitted, Debra Shore, Chairman Committee on Stormwater Management
Disposition of this agenda item will be documented in the official Regular Board Meeting Minutes of the Board of Commissioners for February 4, 2010