In SFHA or flood plains, where no floodways have been identified and no base flood or 100-year frequency flood elevations have been established by FEMA, and draining 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 nor significantly increase the base flood or 100-year frequency flood elevation.
A. Development Permit: No person not exempted by State law, shall commence any development in a SFHA or flood plain without first obtaining a development permit from the City Engineer. Application for a development permit shall be made on a form provided by the City. The application shall be accompanied by drawings of the site, drawn to scale showing property line dimensions; and existing grade elevations and all changes in grade resulting from excavation or filling, sealed by a licensed engineer, architect or surveyor; the location and dimensions of all buildings and additions to buildings; and the elevation at the lowest floor (including basement) of all proposed buildings subject to the requirements of Section 7-1-10 of this Chapter.
The application for a development permit shall also include the following information:
1. A detailed description of the proposed activity, its purpose and intended use;
2. Site location (including legal description) of the property, drawn to scale, on the regulatory floodway maps, indicating whether it is proposed to be in an incorporated or unincorporated area;
3. Anticipated dates of initiation and completion of activity;
4. Plans of the proposed activity shall be provided which include as a minimum:
a. A vicinity map showing the site of the activity, name of the waterway, boundary lines, names of roads in the vicinity of the site, graphic or numerical scale, and north arrow;
b. A plan view of the project and engineering study reach showing existing and proposed conditions including principal dimensions of the structure or work, elevations in mean sea level (1929 adjustment) datum of NGVD, adjacent property lines and ownership, drainage and flood control easements, distance between proposed activity and navigation channel (when the proposed construction is near a commercially navigable body of water), flood plain limit, location and orientation of cross sections, north arrow, and a graphical or numerical scale;
c. Cross section views of the project and engineering study reach showing existing and proposed conditions including principal dimensions of the work as shown in plan view, existing and proposed elevations, normal water elevation, 10-year frequency flood elevation, and graphical or numerical scales (horizontal and vertical); and
d. A soil erosion and sedimentation control plan for disturbed areas. This plan shall include a description of the sequence of grading activities and the temporary sediment and erosion control measures to be implemented to mitigate their effects. This plan shall also include a description of final stabilization and revegetation measures, and the identification of a responsible party to ensure post construction maintenance.
5. Engineering calculations and supporting data shall be submitted showing that the proposed work will meet the criteria of subsection A4b of this Section.
6. Any and all other local, State and Federal permits or approvals that may be required for this type of development.
B. Acceptable Elevation Data: Based on the best available existing data according to the Illinois State Water Survey's Flood Plain Information Repository, the City Engineer shall compare the elevation of the site to the base flood or 100-year frequency flood elevation. Should no elevation information exist for the site, the developer's engineer shall calculate the elevation according to subsection 7-1-6D of this Chapter. Any development located on land that can be shown to have been higher than the base flood elevation as of the site's first Flood Insurance Rate Map identification is not in the SFHA and, therefore, not subject to the requirements of this Chapter. The Building Official 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.
1. The City Engineer 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 City Engineer shall not issue the development permit unless all required local, State and Federal permits have been obtained.
2. 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 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.
3. Within all riverine SFHAs where the floodway has not been determined, the following standards shall apply:
a. 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 subsections 7-1-8-2L1a through (1) of this Chapter for the entire flood plain as calculated under the provisions of subsection 7-1-6D of this Chapter. As an alternative, the developer should have an engineering study performed to determine a floodway and submit that engineering study to DWR for acceptance as a regulatory floodway.
b. A development permit shall not be issued unless the applicant first obtains a permit from DWR or written documentation that a permit is not required from DWR.
c. No permit from DWR shall be required if the Division has delegated permit responsibility to the City per 92 Illinois Administrative Code, part 708 for regulatory floodways, per DWR's Statewide permit entitled "Construction in Flood Plains with No Designated Floodways in Northeastern Illinois".
d. Dam Safety Permits: Any work Involving the construction, modification or removal of a dam or an on-stream structure to impound water as defined in Section 7-1-3 of this Chapter shall obtain an Illinois Division of Water Resources dam safety permit or letter indicating a permit is not required prior to the start of construction of a dam.
If the City Engineer finds a dam that does not have a DWR permit, the City Engineer shall immediately notify the Dam Safety Section of the Division of Water Resources. If the City Engineer finds a dam which is believed to be In unsafe condition, the City Engineer shall immediately notify the owner of the dam and the Illinois Emergency Services and Disaster Agency (ESDA), and the DWR, Dam Safety Section in Springfield.
e. The following activities may be permitted without a registered professional engineer's review or calculation of a base flood elevation and regulatory floodway. Such activities shall still meet the other requirements of this Chapter.
(1) Underground and overhead utilities that:
(A) Do not result in any increase in existing ground elevations, or
(B) Do not require the placement of aboveground structures in the floodway, or
(C) In the case of underground stream crossings, the top of the pipe or encasement is buried a minimum of three feet (3') below the existing streambed, and
(D) In the case of overhead utilities, no supporting towers are placed in the watercourse and are designed in such a fashion as not to catch debris.
(2) Storm and sanitary sewer outfalls that:
(A) Do not extend riverward or lakeward of the existing adjacent natural bank slope, and
(B) Do not result in an increase in ground elevation, and
(C) Are designed so as not to cause stream bank erosion at the outfall location.
(3) Construction of shoreline and streambed protection that:
(A) Does not exceed one thousand feet (1,000') in length or two (2) cubic yards per lineal foot of streambed.
(B) Materials are not placed higher than the existing top of bank.
(C) Materials are placed so as not to reduce the cross-sectional area of the stream channel by more than ten percent (10%).
(D) Vegetative stabilization 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, natural rock or riprap 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 (0.5') or less above natural grade.
(B) The crossing will allow stream flow to pass without backing up the water more than one-tenth foot (0.1') during the 100-year flow, or above the stream bank vegetation line or above any drainage tile or outfall invert, whichever is more restrictive.
(C) The top of the roadway fill in the channel will be at least two feet (2') below the top of the lowest bank. Any fill in the channel shall be nonerosive material, such as riprap 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.
(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 seventy (70) square feet in size, nor ten feet (10') in any one dimension (e.g., animal shelters and tool sheds);
(9) The construction of additions to existing buildings which do not increase the first floor area by more than twenty percent (20%) 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 flow of flood waters;
(10) Minor maintenance dredging of a stream channel where;
(A) The affected length of stream is less than one thousand feet (1,000').
(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.
4. Compensatory Storage: Whenever any portion of a flood plain 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.
The excavation volume shall be at least equal to one and one-half (1.5) times the volume of storage lost due to the fill or structure. In the case of streams and watercourses, such excavation shall be made opposite or adjacent to the areas so filled or occupied. All flood plain storage lost below the existing 10-year flood elevation shall be replaced below the proposed 10-year flood elevation. All flood plain storage lost above the existing 10-year flood elevation shall be replaced above the proposed 10-year flood elevation. All such excavations shall be constructed to drain freely and openly to the watercourse. (Ord. 0-90-37, 8-20-1990)