Isolated Waters of Lake County ("IWLC")

Overviewcompliance regulation icon

Appendix A of the Lake County Watershed Development Ordinance (WDO) defines Isolated Waters of Lake County (IWLC) as “All waters such as lakes, ponds, streams, farmed wetlands, and wetlands that are not under U.S. Army Corps of Engineers’ (Corps) jurisdiction. The limits of the Isolated Waters of Lake County extend to the ordinary high water mark or the delineated wetland boundary.”

Article 10 of the WDO includes provisions for the protection of IWLC. For developments that will impact IWLC, the applicant must obtain written approval from the SMC or an Isolated Wetland Certified Community (IWCC) prior to issuance of a Lake County Watershed Development Permit (WDP).  

The Corps regulates impacts to Waters of the U.S (WOTUS), which generally include navigable waters and their tributaries, adjacent wetlands, and other waters included under the current federal definition in 33 CFR Part 328.3.(a). For developments that will impact WOTUS, the applicant must obtain a separate Section 404 authorization from the Corps in addition to a WDP from the SMC or a certified community.

 To determine whether wetlands and waters on a development site are IWLC or WOTUS, the WDO requires the applicant obtain a written Jurisdictional Determination (JD) from the Corps or a Corps-approved agency, such as the SMC (or Lake County PBD in unincorporated areas). A preliminary jurisdictional determination (PJD) can be obtained from the SMC within 30 days (field conditions permitting) for a nominal review fee by submitting a Jurisdictional Determination Request Form (PDF).  Either a JD from the Corps or a PJD from SMC satisfies the WDO requirement for a written jurisdictional determination.

IWLC Impact Categories and Submittapermit stampl Requirements

Developments with any proposed impacts to IWLC are categorized according to the acreage and quality of proposed wetlands/waters impacts. Submittal requirements are proportionate with the impact category.

  • Category-I: Impacts less than or equal to 1 acre to non-High Quality Aquatic Resources (HQAR) IWLC. Standard submittal requirements apply, as outlined in WDO Section 1005.01.A-K. Note: SMC’s General Permit #2 described below may apply for some developments with proposed minor impacts to IWLC.
  • Category-II: Impacts greater than 1 acre and less than 2 acres to non-HQAR IWLCs. Standard submittal requirements above, plus requires a narrative that shows avoidance, minimization, or mitigation of impacts.
  • Category-III: Impacts greater than 2 acres or impacts any acreage of HQAR (unless qualifies for SMC GP-2). Standard submittal requirements above, plus applicant must show, in sequence, avoidance and then minimization before compensatory mitigation is considered. All Category-III developments require a 15-day Technical Notification to regulatory agencies including the Corps, U.S. Environmental Protection Agency, U.S. Fish & Wildlife Service and Illinois Department of Natural Resources, requesting comments on the proposed development. The applicant must satisfactorily address any comments received prior to issuance of the Category-III impacts approval.    
  • Category-IV: IWLC impacts for wetland restoration, creation and enhancement of wetlands, provided there are net gains in aquatic resource function. Category IV activities include shoreline and streambank erosion restoration described in WDO Section 704.04. Standard submittal requirements above, plus a narrative on the benefits to the aquatic environment of the proposed development.
  • SMC’s General Permit #2: Developments under SMC’s permitting authority with proposed minor impacts to less than 0.1 acre of non-HQAR IWLC or 1,000 square feet (0.023 ac) of HQAR IWLC may qualify for this general permit. A 1-page notification form and limited supporting information are required for this streamlined permit. See Section III. in SMC General Permit 2 for specific notification requirements.

IWLC Mitigation Requirementscattail circle-kindpng-pantanal wtl plants cattail clip art

WDO Section 1007.01 requires compensatory mitigation for impacts of 0.1 acre or greater to IWLC, including those that are HQAR. For single lot, single-family residences (provided the activity is a single and complete project), mitigation is required for wetland impacts greater than 0.25 acre of non-HQAR IWLC or 0.1 acre of HQAR IWLC .

IWLC impacts must be mitigated at a minimum ratio of 1.5:1 (one and one-half acres mitigation for each acre of non-HQAR IWLC impacted), 3:1 for HQAR, and 6:1 for forested HQAR. For impacts to open waters (i.e., water bodies more than 3 feet deep) that are not HQAR under Categories I, II, and III, a minimum 1:1 mitigation ratio is required. Mitigation is not required for Category-IV impacts.
All mitigation must take place within Lake County, IL, to maintain no-net-loss of wetlands in the county.
Mitigation may be achieved in several ways: 
(1) creating new wetlands, restoring historic wetlands or enhancing degraded wetlands (or farmed wetlands) on the development site or on an off-site property within the same watershed as the wetland impacts; 

(2) purchasing “credits” (i.e., acres of wetlands) from a Corps-approved or SMC-approved mitigation bank within the same watershed as the wetland impacts (or out-of-watershed bank at double the mitigation acreage required); or 

(3) using the SMC Wetland Restoration Fund (WRF), which provides for fee-in-lieu of mitigation. The WRF option can only be considered when no mitigation bank credits are available in the same watershed as the IWLC impacts.

The IWLC Review Process – Who Approves IWLC Impacts?

Isolated wetland certified communities (IWCC) are authorized to review and approve IWLC impacts under Categories I-IV above. See Certified Communities Webpage for the current list of IWCC. The IWCC are required to have a Lake County Certified Wetland Specialist (CWS) on staff, or retain a CWS consultant to perform the IWLC impact reviews on behalf of the community. See Contact List for Communities for the current list of CWS.

SMC’s wetland specialists review IWLC impacts for all communities that are not isolated wetland certified, as well as public road developments (excluding State and Federal road projects) and Lake County Forest Preserve developments. Contact Juli Crane at [email protected]