In SFHA or floodplains (including AO zones, AH zones and unnumbered A zones) where no floodways have been identified and no BFEs have been established and which drains more than one square mile, no development shall be permitted unless the cumulative effect of the proposals, when combined with all other existing and anticipated uses and structures, shall not significantly impede or increase the flow and passage of the floodwaters and will not significantly increase the BFE. The development must meet all applicable requirements of this chapter and 17 Ill. Adm. Code Part 3700.The development shall also meet the requirements of Section 15.68.080 of this chapter.
A. Floodplain Development Permit. No person, firm, corporation or governmental body, not exempt by state law, shall commence any development in an SFHA or floodplain without first obtaining a floodplain development permit from the Director, as applicable. Application for a floodplain development permit shall be made on a form provided by the Director.
B. Duties 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 this type of activity. The Director shall not issue the floodplain development permit unless copies of all required local, state, and federal permits have been submitted to the Director by the applicant.
C. Preventing Increased Damages. No development in the SFHA, where a floodway has not been determined, shall create a damaging or potentially damaging increase in flood heights or velocity or threat to public health, safety, and welfare.
D. Standards within Riverine SFHAs. Within all riverine SFHA's where the floodway has not been determined, the following standards shall apply.
1. The developer shall have a registered professional engineer state in writing and show through supporting plans, calculation and data that the project meets the engineering requirements of the WMO and Section 15.68.
2. A floodplain development permit shall not be issued unless the applicant first obtains a permit from IDNR/OWR or written documentation that a permit is not required from IDNR/OWR.
3. Dam Safety Permits. Any person performing work involving the construction, modification or removal of a dam (as defined in Section 15.68.020 of this chapter) shall obtain an IDNR/OWR Dam Safety Permit or letter indicating a permit is not required prior to the start of construction of a dam. If the Director finds a dam that does not have an IDNR/OWR permit, the Director shall immediately notify the Dam Safety Section of IDNR/OWR. If the Director finds a dam which is believed to be in unsafe condition, the Director shall immediately notify the owner of the dam, IDNR/OWR, Dam Safety Section, and the Illinois Emergency Management Agency (IEMA).
4. Activities That Qualify for a Regional or Statewide Permit from IDNR/OWR. The following activities may be permitted without a registered professional engineer's review or calculations of a base flood elevation and regulatory floodway. Such activities shall meet the other requirements of this chapter:
a. Underground and overhead utilities that:
i. Do not result in any increase in existing ground elevations;
ii. Do not require the placement of above ground structures in the floodway;
iii. In the case of underground stream crossings, the top of the pipe or encasement is buried a minimum of three feet below the existing streambed;
iv. In the case of overhead utility lines, the lines shall be constructed above the estimated 100-year flood elevation or attached above the low chords of an existing bridge (with the permission of the bridge owner). No supporting towers shall be placed in the watercourse and shall be designed in such a fashion as not to catch debris.
v. Disturbance of streamside vegetation shall be kept to a minimum during construction to prevent erosion and sedimentation.
b. Storm and sanitary sewer outfalls that:
i. Do not extend riverward or lakeward of the existing adjacent natural bank slope;
ii. Do not result in an increase in ground elevation; and
iii. Are designed so as not to cause stream bank erosion at the outfall location.
c. Construction of shoreline and streambed protection:
i. When such construction does not exceed one thousand (1,000) feet in length;
ii. When materials used in such construction are not placed higher than the existing top of bank; and
iii. When materials used in such construction are placed so as not to reduce the cross- sectional area of the stream channel by more than ten (10) percent.
d. The construction of light poles, sign posts and similar structures.
e. The construction of sidewalks, driveways, athletic fields (excluding fences), patios and similar surfaces which are built at grade.
f. The construction of properly anchored, unwalled, open structures such as playground equipment, pavilions and carports built at or below existing grade that would not obstruct the flow of floodwaters.
g. The placement of properly anchored buildings not exceeding seventy (70) square feet in size, nor ten (10) feet in any one dimension (e.g., animal shelters and tool sheds).
h. The construction of additions to existing buildings which do not increase the first floor area by more than twenty (20) percent, which are located on the upstream or downstream side of the existing building, and which do not extend beyond the sides of the existing building that are parallel to the floodwaters.
i. Minor maintenance dredging of a stream channel where:
i. The affected length of stream is less than one thousand (1,000) feet;
ii The work is confined to reestablishing flows in natural stream channels; or
iii. The cross-sectional area of the dredged channel conforms to that of the natural channel upstream and downstream of that site.
5. The flood-carrying capacity within any altered or relocated watercourse shall be maintained.
E. Compensatory Storage. Whenever any portion of a floodplain, (including AO zones, AH zones and unnumbered A zones) where no floodways have been identified and no base flood or one hundred (100) year frequency flood elevations have been established and which drains more than one square mile, 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 base flood or one hundred (100) year frequency flood elevation. The excavation volume shall meet the requirements of § 602.7-9 of the WMO. (Prior code § 28.07)
(MC-4-2021, § 2, Amended 8/3/2021; MC-5-2018, Amended, 08/07/2018: MC-5-2014 § 22, 04/17/2014; MC-2-2008, Amended, 05/06/2008)