A. Definition: Special management areas shall generally refer to floodplain, floodway, wetlands, and buffers as defined and regulated herein as well as within the DuPage County Countywide Stormwater and Floodplain Ordinance.
B. Requirements For Regulatory Floodplain And Regulatory Floodway Determination:
1. Refer to the DuPage County Countywide Stormwater and Floodplain Ordinance section 15-80.
2. Any developer proposing development shall identify the boundaries and elevation of the regulatory floodplain and the boundaries of the regulatory floodway.
3. The regulatory floodplain shall be determined by the highest base flood elevation for a development site at the time of application, or for purposes of establishing the low opening on new construction of buildings, as determined by the hierarchy established in the DuPage County Countywide Stormwater and Floodplain Ordinance section 15-80.
4. If a floodway is not designated on the maps on file in the Office of the City Clerk, then the regulatory floodway shall be deemed to be the regulatory floodplain.
C. Requirements For Development Within the Regulatory Floodplain:
1. DuPage County Requirements: Refer to the DuPage County Countywide Stormwater and Floodplain Ordinance section 15-81 as well as the following requirements.
2. Floodway Conveyance: Development shall preserve effective floodway conveyance such that there will be no increases in flood elevations, flows, or floodway velocity, unless any such increases are contained in a public flood easement and a watershed benefit is provided.
3. Elevation: All usable space in new buildings, added to existing buildings, or in existing buildings in the floodplain undergoing substantial improvement shall be elevated to at least one foot (1') above the base flood elevation.
4. Compensatory Storage:
a. Compensatory storage shall be operational prior to placement of fill, structures, or other materials in the regulatory floodplain.
b. Any removal, replacement, or modification of stormwater facilities that has an existing hydraulic impact shall provide a watershed benefit and shall require compensatory storage to mitigate for any potential increases in flow or flood elevations. All structures and their associated low entry elevations within the created backwater of the existing stormwater facility shall be identified.
5. Building Protection Standards:
a. Existing structures shall not be enlarged, replaced, or structurally altered unless the changes meet the requirements for development. If the changes constitute substantial improvement to a building in the floodplain, then the entire building shall meet the requirements for development.
b. Existing structures may be floodproofed. Floodproofing devices shall meet the requirements for development in the floodplain and be operational without human intervention. If electricity is required, then there must be a backup power source that will activate without human intervention. The floodproofing shall be certified by a professional engineer.
c. New structures other than buildings shall either be elevated to at least one foot (1') above the base flood elevation or designed for protection against physical flood damages. Floodproofing devices shall be operational without human intervention. If electricity is required for protection against flood damage, then there must be a backup power source that will activate without human intervention. The floodproofing shall be certified by a professional engineer.
d. When a structure is elevated by some means other than filling in the regulatory floodplain:
(1) The usable space of any building and all electrical, heating, ventilating, plumbing, and air conditioning equipment shall be located at least one foot (1') above the highest base flood elevation; and
(2) All materials and structures less than one foot (1') above the base flood elevation shall be resistant to flood damage.
6. Additional Requirements For Manufactured Homes:
a. Adequate access and drainage shall be provided;
b. If pilings are used for elevation, applicable design and construction standards for pilings shall be met.
7. Documents: A copy of an application for a CLOMR, CLOMA, LOMA, or LOMR including all the required information, calculations, and documents shall be submitted to the department concurrent with the application to FEMA or OWR or its designee.
8. Filling And Excavating: No filling, grading, dredging, or excavating shall take place until a CLOMR is issued by FEMA.
9. Fill: Any fill required to elevate a building must extend at least ten feet (10') beyond the foundation before the grade slopes below the highest base flood elevation.
10. Release Rate: The release rate from new or modified storm sewer outfalls shall meet the requirements of subsection 10.105D of this article, or demonstrate compliance with this section.
11. Hydrologic And Hydraulic Impacts: Hydrologic and hydraulic impacts of developments located in the regulatory floodway shall be evaluated using the applicable regulatory model and confirmed using watershed plan models, if available, or models meeting the plan standards for watershed planning or as directed by the City Engineer. The hydrologic and hydraulic impacts of development shall be evaluated using events representing the frequency range from fifty percent (50%) (2-year) to one percent (1%) (100-year) probability of being equaled or exceeded in a given year. The results of any such evaluation shall be submitted to the department.
12. Evaluation Of Impacts: Any proposed development in the regulatory floodway shall evaluate the hydrologic and hydraulic impacts for existing and future impacts of the proposed development on the waterway.
D. Requirements For Wetland Delineation:
1. Refer to the DuPage County Countywide Stormwater and Floodplain Ordinance section 15-85 as well as the following requirements.
2. Any developer proposing development in or near mapped wetland areas shall identify the boundaries, extent, hydrology, function and quality of all wetland areas on the subject property. The presence and extent of wetland areas on the subject property shall be determined as the result of an onsite wetland procedure and verified by an environmental scientist representing the community where the wetland is located. This procedure shall be conducted in accordance with the current Federal wetland determination methodology authorized under section 404 of the Clean Water Act.
3. Critical wetland status shall be assigned to those wetlands that have been determined to satisfy one or more of the criteria in the DuPage County Countywide Stormwater and Floodplain Ordinance or one the following:
a. The ratio of stormwater storage volume available at the base flood elevation to tributary basin runoff volume to the wetland is twenty five percent (25%) or greater, or alternatively using a method described in subsection 10.105D of this article, the loss of wetland storage causes adverse off site impacts that cannot be mitigated in accordance with subsection 10.105C of this article and subsection C of this section. If both methods are performed, the methods described in subsection 10.105D of this article shall prevail as the determining value; or
b. The existing release rate from the wetland is 0.1 cfs/acre or less and determined using the method described in subsection 10.105D3 of this article.
4. All other wetlands not meeting one or more critical wetland criteria shall be assigned a regulatory wetland status. The final determination of status shall be made by the City Engineer based upon a review of submitted information and when necessary, upon consultation with outside wetland authorities.
E. Requirements For Development Affecting The Function And Values Of Wetlands: Refer to the DuPage County Countywide Stormwater and Floodplain Ordinance section 15-86.
F. Direct And Indirect Impacts To Wetlands:
1. Refer to the DuPage County Countywide Stormwater and Floodplain Ordinance section 15-87 as well as the following requirements.
2. Development will be permitted only when the proposed direct environmental impacts to onsite wetlands, and indirect environmental impacts to offsite wetlands, can be sufficiently evaluated, minimized, and mitigated, as specified in this subsection F.
3. Mitigated wetlands shall be designed to duplicate or improve the hydrologic, biologic, and economic features of the original wetland. The City Engineer may require a greater compensation ratio where special wetland functions are threatened.
4. Creation of wetlands for the mitigation of development impacts within or affecting a critical or regulatory wetland may take place only within areas not currently comprised of wetlands.
5. Mitigation of impacts within or affecting critical and regulatory wetlands shall include design, construction, and continued maintenance of the mitigation measures.
6. The City Engineer, at his or her discretion, may allow an existing wetland contiguous to a proposed regulatory wetland mitigation site to be enhanced in exchange for a partial reduction in the mitigation area required. In no case shall the area replacement be allowed to fall below a one to one (1:1) ratio.
7. Development in or affecting a wetland environment shall be initiated only after a mitigation plan has been approved and adequate securities are provided as specified in section 10.109 of this article.
8. The designs and analyses of all wetland mitigation measures shall meet the standards of the plan and shall comply with all applicable Federal, State, and local regulations regarding wetland impact and mitigation.
9. The City Engineer shall require that the developer or owner provide the City with periodic monitoring reports, at least annually, on the status of the constructed mitigation measures and progress towards meeting the approved performance standards, and further may require the developer or owner to undertake remedial action to bring the area into compliance with the mitigation plan.
10. To the extent practicable, development within fifty feet (50') of a wetland shall not, without mitigation:
a. Adversely change the quantity, quality, or temporal and areal distribution of flows entering any adjacent wetlands or waters; nor
b. Destroy or damage vegetation that stabilizes wetland fringe areas or provides overland flow filtration to wetlands; nor
c. Adversely affect any groundwater infiltration functions.
G. Wetland Banking:
1. Refer to the DuPage County Countywide Stormwater and Floodplain Ordinance section 15-89 as well as the following requirement.
2. If a wetland meets all the conditions for mitigation in a Wetland Banking Program and there is not a Wetland Banking Program in the watershed planning area, mitigation outside the watershed planning area is permitted provided the following conditions are met:
a. Mitigation is to be provided in the closest Wetland Banking Program with the greatest wetland deficit. If there are no watershed planning areas with a wetland deficit, then the mitigation shall take place in the closest Wetland Banking Program. The Wetland Banking Program shall be determined by measuring from the centroid of wetland disturbance to the closest appropriate watershed planning boundary.
b. The area of mitigation available within a Wetland Banking Program available in any Wetland Banking Program for mitigation from outside the watershed planning area shall not exceed fifteen percent (15%) of the original bank area.
H. Riparian Buffer Requirements:
1. Refer to the DuPage County Countywide Stormwater and Floodplain Ordinance section 15-92 as well as the following requirements:
2. Riparian buffers serve the following functions:
a. Prevents erosion and promotes bank stability of streams, lakes, ponds, or wetland shorelines.
b. Controls sediment from upland areas thus reducing the impact of urbanization on stream habitat and water quality by filtering and assimilating nutrients discharged from surrounding uplands.
c. Insulates and moderates daily and seasonal stream temperature fluctuations by maintaining cooler instream temperatures for areas with overhang vegetation.
d. Serves as important sites for denitrification, which reduces development of algal blooms and subsequent depressed levels of dissolved oxygen in stream.
e. Provides an effective mechanism for treatment of contaminated surface runoff.
f. Provides habitat corridors for both aquatic and terrestrial fauna and flora.
g. Provides recreational and aesthetics values for human use.
3. Any developer proposing development in a riparian buffer shall identify the boundaries by using the first of the following documents or procedures pertaining at the time of development:
a. Riparian buffers identified in watershed plans.
b. Riparian buffers identified in interim watershed plans.
c. Vegetative areas along waterways within the limits of the regulatory floodplain. If there is no floodplain designated, either by FEMA or OWR, then the riparian buffer shall extend a minimum of seventy five feet (75') from the ordinary high water level of the water body or delineated wetland, unless property boundaries limitations exist, or it can otherwise be demonstrated that a lesser width is sufficient; but in no case shall a buffer be less than fifteen feet (15') in width.
4. Tree cutting and vegetation removal shall be minimized within riparian buffers, and revegetation of disturbed areas shall take place as soon as possible.
5. Development in a riparian buffer shall be initiated only in accordance with the requirements of this subsection G and the standards of the plan and upon consultation with the technical guidance for the DuPage Countywide Stormwater and Floodplain Ordinance for the plan.
6. To the extent practicable, development in a riparian buffer shall not, without mitigation:
a. Adversely change the quantity, quality, or temporal and areal distribution of flows entering any adjacent critical wetlands or waters; nor
b. Destroy or damage vegetation that overhangs, stabilizes, provides overland flow filtration, or shades stream channels, wetlands, or impoundments that normally contain water; nor
c. Adversely affect any groundwater infiltration functions.
I. Development Affecting A Buffer:
1. Refer to the DuPage County Countywide Stormwater and Floodplain Ordinance section 15-94 as well as the following requirements:
2. The length of any mitigated channel shall be equal to or greater than the length of the disturbed channel.
3. Mitigation in riparian buffers shall be in accordance with the procedures specified in the plan.
4. Mitigation measures in riparian buffers shall include required provisions for long term maintenance. (Ord. O-19-023, 7-18-2019, eff. 7-18-2019)