(A) 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 or impair the natural hydrologic and hydraulic functions of the floodway or channel, or impair existing water quality or aquatic habitat. Construction impacts shall be minimized by appropriate mitigation methods as called for in this chapter.
(B) Within all riverine SFHAs 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, calculations and data that the project meets the engineering requirements of § 156.42(C)(1) through (C)(9) of this chapter for the entire floodplain as calculated under the provisions of § 156.05(D) of this chapter.
(a) As an alternative, the developer should have an engineering study performed to determine a floodway and submit that engineering study to IDNR/OWR for acceptance as a designated floodway.
(2) A 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) No permit from IDNR/OWR shall be required if IDNR/OWR has delegated permit responsibility to the village per 17 Ill. Admin. Code part 3708 for designated floodways.
(4) Permits for Dams
(a) Any work involving the construction, modification or removal of a dam, as defined in § 156.02, per 17 Ill. Admin. Code part 3702 (Rules for Construction of Dams), shall obtain an IDNR/OWR permit prior to the start of construction of a dam.
(b) If the Building Inspector finds a dam that does not have an IDNR/OWR permit, the Building Inspector shall immediately notify the IDNR/OWR Bartlett office.
(c) If the Building Inspector finds a dam which is believed to be in unsafe condition, the Building Inspector shall immediately notify the owner of the dam, the IDNR/OWR Bartlett office and the Illinois Emergency Management Agency (IEMA).
(C) The following activities may be permitted without a registered professional engineer’s review or calculation of a base flood elevation and designated floodway. The activities shall still meet the other requirements of this chapter:
(1) (a) Underground and overhead utilities that:
1. Do not result in any increase in existing ground elevations;
2. Do not require the placement of above ground structures in the floodway; or
3. 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.
(b) Overhead utility lines shall be constructed above the estimated 100-year frequency flood elevation or attached above the low chord of an existing bridge (with the permission of the bridge owner). No supporting towers shall be placed in the watercourse and shall be designed so as to not catch debris.
(c) Disturbance of streamside vegetation shall be kept to minimum during construction to prevent erosion and sedimentation.
(d) A utility crossing carrying material which may cause water pollution as defined by the Environmental Protection Act, ILCS Ch. 415, Act 5 (1992 State Bar Edition), shall be provided with shut-off valves on each side of the body of water to be crossed.
(g) All State Commerce Commission, National Electric Safety Codes and federal requirements for clearance must be met.
(2) Storm and sanitary sewer relief outfalls that:
(a) Do not extend riverward or lakeward of the existing adjacent natural bank slope;
(b) Do not result in an increase in ground elevation; and
(c) Are designed so as not to cause stream erosion at the outfall location.
(3) (a) Construction of shoreline and streambank protection that:
1. Does not exceed 1,000 feet in length;
2. Materials are not placed higher than the existing top of bank; and
3. Materials are placed so as not to reduce the cross-sectional area of the stream channel by more than 10%.
(b) Stabilization utilizing native vegetation and gradual side slopes are the preferred mitigation methods for existing erosion problems. Where high channel velocities, sharp bends or wave action necessitate the use of alternative stabilization measures, soil bioengineering techniques, natural rock or rip-rap are preferred materials. Artificial materials such as concrete, construction rubble and gabions should be avoided unless there are no practicable alternatives.
(4) Temporary stream crossings in which:
(a) The approach roads will be one-half foot or less above natural grade;
(b) The crossings will allow stream flow to pass without backing up the water above the stream bank vegetation line or above any drainage tile or outfall invert;
(c) The top of the roadway fill in the channel will be at least two feet below the top of the lowest bank. Any fill in the channel shall be non-erosive material, such as rip-rap or gravel;
(d) All disturbed stream banks will be seeded or otherwise stabilized as soon as possible upon installation and again upon removal of construction; and
(e) The access road and temporary crossings will be removed within one year after authorization.
(5) The construction of light poles, sign posts and similar structures;
(6) The construction of sidewalks, driveways, athletic fields (excluding fences), patios and similar surfaces which are built at grade;
(7) 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 flood waters;
(8) The placement of properly anchored buildings not exceeding 70 square feet in size, nor ten feet in any one dimension (e.g., animal shelters and tool sheds);
(9) The construction of additions to existing Building Inspector which are located on the upstream or downstream side of the existing building, and which do extend beyond the sides of the existing building that are parallel to the flow of flood waters; and
(10) Minor maintenance dredging of a stream channel where:
(a) The affected length of stream is less than 1,000 feet;
(b) The work is confined to reestablishing flows in natural stream channels; or
(c) The cross-sectional area of the dredged channel conforms to that of the natural channel upstream and downstream of the site.
(D) The flood carrying capacity within any altered or relocated watercourse shall be maintained.
(E) 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 base flood or 100-year frequency flood elevation shall be compensated for and balanced by a hydraulically equivalent volume of excavation taken from below the base flood or 100-year frequency flood elevation.
(2) The excavation volume shall be at least equal to one and one-half times the volume of storage lost due to the fill or structure.
(3) In the case of streams and watercourses, the excavation shall be made opposite or adjacent to the areas so filled or occupied.
(4) All floodplain storage lost below the existing ten-year flood elevation shall be replaced below the proposed ten-year flood elevation. All floodplain storage lost above the existing ten-year flood elevation shall be replaced above the proposed ten-year flood elevation. All excavations shall be constructed to drain freely and openly to the watercourse.
(Ord. 05-09, passed 5-24-2005)