kane county stormwater technical guidance manual - Kane County, IL

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§ T403 Floodplain Management The applicant must identify floodplain limits using the best available information, or the applicant, Director, or Administrator may choose to develop a project-specific floodplain delineation. The best available information may include reports and studies published by the U.S. Army Corps of Engineers (COE), the U.S. Department of Agriculture – Natural Resources Conservation Service (NRCS), the U.S. Geological Survey (USGS), the Illinois State Water Survey (ISWS), the Illinois Department of Transportation, Illinois Department of Natural Resources- Office of Water Resources (IDNR-OWR) or the Northeastern Illinois Planning Commission (NIPC). The Administrator will need to approve the use of any floodplain study not previously designated as a regulatory study prior to the use of the BFEs, flood profiles or delineations. Applicants should check for the best available information with ISWS Floodplain Repository for BFE data associated with “A Zone” delineations on FEMA maps. Project specific floodplain delineation requires detailed and sophisticated studies. Determining the relationship between the project site and the floodplain is the responsibility of the applicant. Table 403 of the Ordinance contains a summary of the requirements for developments in the floodplain. The left column of the Table refers to the type of floodplain on-site. References in the Table to “all” refer to projects of the type noted or with the designation of floodplain noted, and they must meet the applicable requirements of the referenced section. The difference between the floodplain and the regulatory floodplain is the jurisdiction of IDNR-OWR. The floodplain is a more general area with elevations at or below the base flood elevation that does not necessarily have one square mile of drainage area. A site without any type of stream or creek flowing through or near it could have floodplain on site if there is a depressional area that contains runoff at or below the base flood elevation determined from a hydrologic model of the tributary watershed area. § T404 Floodplain, Regulatory Floodplain, Base Flood Elevation (BFE) and Regulatory Floodway Locations Developers must identify all floodplains (regulatory and non-regulatory) on the property proposed for development. Developers also must identify Regulatory Floodway affected by the development. Developers should check with the community official or Administrator to determine if any LOMRs have been published for the development area. Kane County also maintains a listing of applicable regulatory maps within the County or its website. If Regulatory Floodway is shown on a Flood Boundary and Floodway Map (FBFM) or Flood Insurance Rate Map (FIRM) for the project area, it shall also be clearly depicted on site topographic plans. Kane County Technical Guidance Manual 61
For projects where no Regulatory Floodplain is shown on the FEMA FIRM, the applicant is responsible for determining the project site BFE. If there is 640 acres (one square mile) or more of upstream tributary drainage area at the outlet point of the site this analysis must be accepted for permitting by IDNR-OWR. The BFE can be determined using a hydrologic and hydraulic (H&H) analysis if the upstream tributary drainage area. Any project-specific floodplain analysis for areas greater than 640 acres may also identify a floodway consistent with IDNR-OWR requirements. For project sites with less than 640 acres of upstream tributary drainage area and no riverine Regulatory Floodplain, the Administrator or Director may require a project-specific floodplain analysis. If the Hydrologic Atlas, published by the United States Geologic Survey (USGS), shows a historic flood area (colored in blue) on the project site, an alternative to a project-specific floodplain analysis may be interpolating the elevation of the inundation area to determine the BFE. For these sites, 3 feet shall be added to the BFE to determine the Flood Protection Elevation (FPE). It should be noted that BFEs which appear on FEMA FIRMs are rounded to the nearest whole foot. It is necessary to consult the FIS flood profiles, which can be read to the nearest 0.1 foot. The flood profile, used in conjunction with site-specific topography, is the definitive floodplain for permitting purposes, but the FEMA mapping is considered definitive for flood insurance and floodway boundaries. If there are inconsistencies, map revisions will be required. The location of the Regulatory Floodway shall be delineated from the IDNR- OWR designated Regulatory Floodway maps. To locate the floodway boundary, the Regulatory floodway limits should be scaled from the Regulatory Floodway map and transferred to the project site plan using reference marks common to both maps. Typical reference marks are: street intersections, corporate limits, and section lines. It is important that the accurate floodway width be maintained during the data transfer process from the regulatory floodway maps to the applicant’s site plan. As with the regulatory floodplain maps, an accurate delineation of the floodway boundary is important to determine the applicable floodway requirements of the Ordinance. The applicant should then check the floodway location in relation to the stream and the site topography. If it appears that the floodway location is unreasonable, the applicant may wish to pursue a Letter of Map Revision (LOMR) based on improved site topography. The LOMR request is made to FEMA through the IDNR-OWR or its designee and the Director. An applicant may apply to the Administrator for conditional approval of a site plan with respect to the floodway boundaries prior to finalizing project design. This will provide 1) the Administrator an opportunity to verify the accuracy of the applicant’s floodway boundary delineation on the site plan, and 2) the Kane County Technical Guidance Manual 62
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KANE COUNTY STORMWATER TECHNICAL GU
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Kane County Technical Guidance Manu
Page 5 and 6:
ARTICLE 13 - FEE-IN-LIEU OF SITE RU
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No. Name LIST OF FIGURES Kane Count
Page 9 and 10:
Organization The Manual is comprise
Page 11 and 12:
ARTICLE 2 - REQUIREMENTS FOR STORMW
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applicant to provide retention volu
Page 15 and 16:
§ T201(e) Protection of Buildings
Page 17 and 18: § T201(f) Planning Principles Meet
Page 19 and 20: 1. Identify all points where runoff
Page 21 and 22: FIGURE 3 Detention Example (continu
Page 23 and 24: 3. Calculating overland flow paths
Page 25 and 26: soil tributary to the downstream sy
Page 27 and 28: purpose of the easement is for main
Page 29 and 30: In general: 1. Impervious surfaces
Page 31 and 32: FIGURE 5 Hydrologically Disturbed A
Page 33 and 34: TABLE 4 Huff Quartile Distributions
Page 35 and 36: FIGURE 6 Median Time Distribution o
Page 37 and 38: All runoff volumes shall be calcula
Page 39 and 40: The retention volume may be reduced
Page 41 and 42: FIGURE 9 Detention Configuration fo
Page 43 and 44: FIGURE 11 Detention Configuration f
Page 45 and 46: FIGURE 13 Separation for Subsurface
Page 47 and 48: § T203(i) Site Runoff Storage Faci
Page 49 and 50: etter information is submitted and
Page 51 and 52: Surface Erosion Factor Subsoil Eros
Page 53 and 54: TABLE 7 Seed Mixtures For Temporary
Page 55 and 56: § T300(d) Extended Construction Sh
Page 57 and 58: FIGURE 14A Sediment Control Practic
Page 59 and 60: Figure 15A Soil Stabilization Pract
Page 61 and 62: § T300(g) Limitation on Site Distu
Page 63 and 64: TABLE 8 Permanent Stabilization Pra
Page 65 and 66: must be cleaned before the end of e
Page 67: ARTICLE 4 - PROTECTION OF SPECIAL M
Page 71 and 72: Residential Buildings The Ordinance
Page 73 and 74: nonresidential), the flood insuranc
Page 75 and 76: FIGURE 18 Required Flood Protection
Page 77 and 78: § T409 Lowest Opening Proposed str
Page 79 and 80: crossing. The floodplain downstream
Page 81 and 82: any revised floodway or will agree,
Page 83 and 84: Illinois Department of Natural Reso
Page 85 and 86: applicant will have to manually adj
Page 87 and 88: exception of the appropriate use re
Page 89 and 90: For all on-site wetlands with buffe
Page 91 and 92: Site: Kane County Stormwater Exampl
Page 93 and 94: § T415 Mitigation to be Local All
Page 95 and 96: FIGURE 21 Linear and Water Body Buf
Page 97 and 98: TABLE 11 Linear Buffer Width Calcul
Page 99 and 100: FIGURE 22 Buffer Width Scenarios Ka
Page 101 and 102: FIGURE 23 Measurement Reference for
Page 103 and 104: ARTICLE 5 - STORMWATER MANAGEMENT P
Page 105 and 106: § T502(a) Required Submittals If t
Page 107 and 108: An example of a narrative descripti
Page 109 and 110: ) Buffer Requirements. The buffer r
Page 111 and 112: ARTICLE 6 - LONG-TERM MAINTENANCE T
Page 113 and 114: 90% of the slopes, as measured by a
Page 115 and 116: ARTICLE 7 - ENFORCEMENT AND PENALIT
Page 117 and 118: § T1500 General ARTICLE 15 - WETLA
Page 119 and 120:
TABLE 14 Mitigation Requirements Mi
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etween wetland mitigation facilitie
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Director will reduce the wetland pe
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FORMS The following sheets contain
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KANE COUNTY STORMWATER MANAGEMENT P
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Identifier 2A 2B 2C 2D 2E 2F 2G 2H
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Identifier 4A 4B 4C 4C-1 4C-2 4C-3
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Identifier 5D-3 5D-4 5D-5 5D-6 5D-7
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Identifier Kane County Stormwater M
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COMMUNITY CONTACT FOR STORMWATER MA
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CERTIFIED COMMUNITY FORM FOR EXEMPT
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INSPECTION CHECKLIST DURING CONSTRU
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DEVELOPER’S STATEMENT Right to Dr
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APPENDICES Kane County Technical Gu
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TABLE A2 Typical Roughness Coeffici
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TABLE A2 (continued) Typical Roughn
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kane county stormwater technical guidance manual - Kane County, IL

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