Skip to code content (skip section selection)
Development in and/or filling of the flood fringe is subject to the provisions of this section and will only be permitted if protection is provided against the base flood or one hundred (100) year frequency flood by proper elevation and if other applicable requirements of this chapter are met. No use will be permitted if it adversely affects the capacity of drainage facilities or systems. Developments located within the flood fringe shall meet the requirements of this section, along with the requirements of Section 15.68.080 of this chapter.
A. Watershed Management Permit Required. No person, firm, corporation or governmental body, other than exempt organizations, shall commence any development in the SFHA without first obtaining a Watershed Management Permit from the Director or the Metropolitan Water Reclamation District of Greater Chicago, as applicable.
B. Application and Site Plan. Application for a Watershed Management Permit shall be made on a form provided by the Director. The application shall meet the requirements of Article 3 of the WMO. For all proposed buildings, the elevation of the lowest floor (including basement) and lowest adjacent grade shall be shown on the submitted plans and the development will be subject to the requirements of Section 15.68.080 of this chapter. The drawing shall be sealed by a registered professional engineer.
C. Review of Application. Upon receipt of a Watershed Management Permit application, the Director shall compare the elevation of the site to the base flood or one hundred (100) year frequency flood elevation. If, upon review, the Director determines that the development is located on land that is higher than the base flood elevation of the current Flood Insurance Rate Map and that has not been filled since the date of the site's first Flood Insurance Rate Map identification, the property shall be considered outside of the SFHA and, therefore, not subject to the requirements of this chapter. The Director shall maintain documentation of the existing ground elevation at the development site and certification that this ground elevation existed prior to the date of the site's first Flood Insurance Rate Map identification.
D. Duties and Responsibilities of Director. The Director shall be responsible for obtaining from the applicant copies of all other local, state and federal permits, approvals or permit-not-required letters that may be required for the proposed activity. The Director shall not issue a permit unless copies of all other local, state and federal permits have been submitted by the applicant.
E. Preventing Increased Damages. No development in the flood fringe shall create a threat to public health and safety.
F. Use of Fill to Elevate Site.
1. Fill shall not be used to elevate a site unless the Average Lot Grade is equal to or greater than the Minimum Average Lot Grade.
2. If fill is being used to elevate the site above the base flood or one hundred (100) year frequency flood elevation, the applicant shall submit sufficient data and obtain a Letter of Map Revision from FEMA for the purpose of removing the site from the floodplain. Notwithstanding anything to the contrary in the Letter of Map Revision or in this chapter, no person who obtains a map revision removing a site from the floodplain shall be entitled to build the lowest floor of a residential building below the BFE, except as provided in Section 15.68.050(G) of this chapter.
(Prior code § 28.05)
G. Constructing Lowest Floor Below BFE. A person who has obtained a Letter of Map Revision that removes a site in the flood fringe from the floodplain due to the use of fill to elevate the site above the BFE, may apply for a permit from the Village to construct the lowest floor of a residential building below the BFE in the flood fringe. The Director shall not issue such a permit unless the applicant has complied with all of the criteria set forth in the following paragraphs of this subsection.
1. Compensatory storage shall be provided in compliance with the requirements of this chapter.
2. The elevation of the lowest opening in the basement wall (i.e. window wells, access ways) shall be at or above the FPE.
3. The lowest grade adjacent to the foundation shall be at or above the FPE, for a minimum distance of ten (10) feet beyond the outside face of the structure.
4. The grade around the perimeter of the structures, measured at a distance of twenty (20) feet from the structure, shall be above the BFE.
5. The ground around the building shall be compacted fill that meets all requirements of this subsection (G) and is at least five (5) feet thick under the basement floor slab. Nothing in this subsection (G) shall be interpreted to require the removal or replacement of fill that was placed as part of a LOMR-F permit, if such fill consists of material, including soil of similar classification and degree of permeability, that meets the requirements of this subsection (G).
6. The fill material shall be compacted to at least 95% of Standard Laboratory Maximum Dry Density (Standard Proctor), according to ASTM Standard D-698. Fill soils shall be fine-grained soils of low permeability, such as those classified as CH, CL, SC, or ML according to ASTM Standard D-2487, Classification of Soils for Engineering Purposes.
7. The fill material must be homogeneous i.e., all of one material, and isotropic, i.e., having the engineering properties must be the same in all directions.
8. All fill material and compaction shall be designed, certified and inspected by an Illinois Registered Professional Engineer or Registered Soils Engineer, as warranted by the site conditions.
9. The basement floor shall be at an elevation that is no more than five (5) feet below the BFE.
10. There shall be a granular drainage layer beneath the floor slab, and a minimum of ¼-horsepower sump pump with a backup power supply shall be provided to remove the seepage flow. The pump shall be rated at four (4) times the estimated seepage rate and shall discharge above the BFE and away from the building in order to prevent flooding of the basement or uplift of the floor under the effect of the seepage pressure.
11. The drainage system shall be equipped with a positive means of preventing backflow.
12. All foundation elements shall be designed to withstand hydrostatic pressure in accordance with accepted engineering practices.
H. Compensatory Storage.
1. Whenever any portion of a floodplain is authorized for use, the volume of space which will be occupied by the authorized fill or structure below the BFE shall be compensated for and balanced by a hydraulically equivalent volume of excavation taken from below the BFE, provided all of the conditions § 602.7-9 of the WMO and of the following paragraphs 2 and 3 of this subsection shall be met.
2. In no case shall the depth of excavation for any compensatory storage in the front and side yards of the lot exceed eighteen (18) inches, as measured from the previously existing natural grade. The rear yard may be permitted to have a greater depth of excavation, if necessary.
3. The use of mechanical means to drain the compensatory storage area will not be permitted.
(MC-5-2018, Amended, 08/07/2018: MC-5-2014 §20, 04/17/2014; MC-2-2008, Amended, 05/06/2008; MC-4-2006, Amended, 07/18/2006; MC-5-2001, Amended, 08/21/2001)