DuPage County Stormwater Ordinance Update- Wetlands and Buffers PRESENTED BY: MARY BETH FALSEY WETLAND SPECIALIST Wetlands Section 15-18.A.1.a: If a Stormwater Administrator has the expertise, he/she can determine that a site does not contain wetland OR that a development will not impact the wetland or buffer *Remember: You can always contact DuPage County Wetland Specialists for guidance Development over 100 feet away from any potential wetlands Topographic maps and other documents should be used to confirm no impact over 200 away 1
Is there a mapped wetland on or near the property? Is there a mapped wetland on or near the property? Aerial photos can help, but a site inspection may be necessary Are hydric soils mapped in this area? 2
Updated hydric soils map not yet available Soil maps from DuPage County GIS website show NRCS soil map units but not if they are hydric Aerial photos- go back in time to get a more overall view http://gis.dupageco.org/dupagemaps/viewer.aspx Look for any recent activities that may change character of the wetland or buffer such as mowing, clearing Buffer impacts that may have occurred since 1992 County wetland maps are not 100% accurate- use only as a tool along with other resources County will be updating the wetland map (still won t be 100%) Hydric soils layer can be used to assist permitting staff Not currently on GIS website but should also be forthcoming Development may proceed without County review only if there are clearly no wetlands Proceed at your own risk! Administrator must document how the decision was made Questionable? Require a wetland determination http://www.dupageco.org/edp/stormwater_management/regulatory_services/1420/ or consult DuPage County Wetland Specialists Wetland delineation and report are required unless the wetland is over 100 feet from development s limit of disturbance Do any GC s apply? Letter of Permission For vegetation management in wetlands or buffers Different than LOP for minor developments Remember: Wetland determinations and wetland boundaries that have been delineated and verified are valid for 2 years 3
Submittals Section 15-48: Wetland and Buffer Impact Submittals List of submittal requirements for wetland and buffer can be found in the Ordinance Checklist Flowchart Wetlands and Buffers Section 15-59.E.5: Sediment and Erosion Control Old Ordinance- double row of silt fence New Ordinance- more options Dual silt fence with one row orange construction fence Dual silt fence, one of which is high visibility material Trench silt fence one foot outside wetland boundary to avoid impact Alternative practices can be proposed Wattles, compost socks, or other practices Additional measures as required Erosion control blanket should be 100% biodegradable Article XI: Wetlands IS THE WETLAND CRITICAL? MDNR (updated form): score 5 or higher New form- same information FQI and mean C- Value: FQI >20 or C- Value >3.5 IDNR/USFWS known Threatened or Endangered species Noted as critical on the DuPage County wetland map MDNR FWS 4
Article XI: Wetlands Section 15-86.C.1: No alternatives analysis or mitigation is required for developments with an aggregate 0.10 acre or less direct impact to wetlands Developments shall meet all of the conditions listed in 15-86.C.1 1. The wetland is regulatory 2. The wetland(s) to be impacted is not over 0.1 acre in size 3. The wetland(s) to be impacted are not USACE jurisdictional 4. The wetland(s) to be impacted are located entirely within the development s platted lot(s) 5. There will be no indirect impacts to remaining wetland area(s) 6. The wetland(s) to be impacted are not part of a wetland mitigation development 7. Is in line with the basic development purpose The applicant must evaluate for changes in hydraulics and hydrology due to development Existing wetlands within 100 feet of the limit of disturbance that have in whole or part topography that is sensitive to change in runoff volume Greater than 20% of the wetland s tributary watershed will be developed Exceptions: Wetland at or below OHWM of a waterway on which the hydraulics will not be changed Streambank stabilization developments Evaluation of Indirect Impacts 15-87.E- Applicant shall develop a sub-watershed model using a model sensitive to land cover changes as they affect surface runoff for rainfall events of 0.5, 1.5, and 3.0 for the 24 hour rainfall event. The distinction between directly connected impervious areas and unconnected impervious areas is in accordance with TR-55 methodology. The following should be modeled simultaneously Unconnected impervious areas may be part of the composite curve number (along with pervious areas). Directly connected impervious areas must be modeled separately. Directly connected impervious areas draining through BMPs which promote infiltration may also be a part of the composite curve number analysis. Evaluate and document all land types and % of tributary area in your SCS curve number and provide an exhibit. Evaluation of Indirect Impacts- Continued The model area shall be the existing and proposed area draining to the wetlands. The applicant need not model either groundwater to the wetland, or flooding of the wetland from adjacent streams unless the development proposes to change the stream hydraulics The existing conditions model shall reflect the current land cover, soils, wetland storage and discharge characteristics in the sub watershed prior to development. The proposed conditions model shall be the existing conditions model with land cover and soil changes reflecting the proposed development. 5
Evaluation of Indirect Impacts- Continued The applicant shall model rainfall events of 0.5, 1.5, and 3.0 inches for 24 hour events under existing and proposed conditions and calculate the total volume of runoff to and including the area of the wetland. For purposes of this comparison, it shall be assumed that the entire volume is present in the wetland at the beginning of routing, and the depth and duration of flooding shall be compared between existing and proposed conditions. If the 3.0 inch rainfall volume does not cause a closed or restricted depression to completely fill, then the applicant shall also model an event of greater rainfall depth such that the volume of runoff produced will be greater than the spillover elevation of the depression. The maximum rainfall event that must be considered is 7.58 inches. For those elevations of a closed depression without a positive outlet, only the change in elevation limitation applies. Indirect Impact Determination Increase or decrease in maximum depth of more than 3 inches Increase to the maximum duration greater than 48 hours above existing high water (for 0.5, 1.5, and 3.0 inches for 24- hour events) 15-87.D Additional analysis for wetlands with a plant community type that may be sensitive to small changes in depth and duration of inundation (e.g. sedge meadow, vernal pool) is required. 15-87.E.3: Additional analysis including stage-storage discharge relationship (hydroperiod) under existing and proposed conditions to document there will be no detrimental changes to plant community or wetland system This must be completed even if a portion of a wetland contains this type of community The project must be designed in order to document there are no indirect impacts to this type of plant community Indirect impacts require Alternatives Analysis and Mitigation before the impact is permitted 6
15-88 Wetland Mitigation Requirements Mitigation required for wetland impacts as follows: 1.5:1 ratio for Regulatory Wetlands 3:1 ratio for Critical Wetlands 1:1 ratio for Natural Area Restoration Projects Mitigation credit can be given as follows: Enhancement of an existing wetland = 0.5: 1 credit Enhancement, restoration, creation of buffer= 0.25 : 1 credit NOTE: Mitigation shall not fall below a 1:1 ratio *As always, consider USACE requirements as they may differ from County Once performance standards have been met, applicants must obtain written regulatory sign-off for all mitigation efforts prior to release of mitigation performance securities. 15-88 Wetland Mitigation Requirements 15-88.L - Similar language to indirect impacts section We will accept other modeling techniques where appropriate If the proposed wetland mitigation intersects the seasonal high or apparent water table, evaluate the groundwater flow and elevation When adjacent to a stream, evaluate the effect of overbank flooding on the wetland mitigation Article XII: Buffers Wetland buffers 50 foot buffer for Regulatory Wetlands 100 foot buffer for Critical Wetlands Riparian buffers Apply to areas around Waters of DuPage Extend from ordinary high water mark (OHWM) All impacts to buffers require replacement of function 15-92.B: Determining Riparian Buffer for Waters of DuPage There is a regulatory floodplain study Buffer width equals limits of floodplain or 15 feet, whichever is greater There is no regulatory floodplain study Buffer width is based on drainage area Drainage area over 100 Acres: Conduct a BFE study to determine 100 year flood; Buffer width equals limits of floodplain Drainage area less than 100 Acres: Buffer width equals 15 feet from Ordinary High Water Mark 7
Ordinary High Water Mark (OHWM) Use of the OHWM applies in certain circumstances and may depend on the choices of the applicant. If riparian buffers are calculated from the OHWM, the line must be delineated by an Environmental Specialist and verified by the Stormwater Administrator. Corps has guidance available Article XII: Buffers Buffers are still regulated based on functions- replace function of existing buffer Buffer does not include impervious, non-vegetated areas, permanent structures, and buildings as these features do not provide buffer functions Existing landscaped areas and lawn have limited function and may be replaced in kind Naturalized stormwater management systems may be placed within outer 50% of the buffer provided that functions are replaced Performance Standards for Wetland, Buffer, and PCBMP plantings Performance standards can be found in an appendix to the Ordinance. They can be modified and tailored to site conditions or project goals as appropriate Monitoring reports are due January 31 st following each full growing season If the property is sold, the Ordinance now requires that all plans and permit documents be transferred to the new owner 15-54.D: Natural Area Restoration, Wetland and Buffer Mitigation Area Security A separate Natural Areas security is held for native plantings (wetland, buffers, PCBMPs) until performance standards are met Typically for 1 year, 3 years, or 5 years- depending on the site May be longer (or shorter) than proposed Responsibility of communities to hold this amount until signoff is granted (by the County for partial waiver) 8
15-54.D: Natural Area Restoration, Wetland and Buffer Mitigation Area Security Cost estimates typically at the end of the submittal Tab 8 Applicants may combine natural areas cost estimates with overall development cost or it may be stand alone Certification letter DEC annual inspection summaries will inform community of the status each year As-Built procedure for developments with wetland, buffer, or PCBMP plantings -Unincorporated DuPage Co. Packaging receipts should be submitted with as- built record drawings Site check to verify plantings and S/E control Note to title Note to title Section 15-47.B Acknowledging presence of onsite wetlands, buffers, floodplains, and PCBMPs with drainage areas of over 1 acre Required at time of as-built submittal Submit to the community for review and approval Partial waiver communities: forward a copy to DuPage County Article XIV Prohibited Acts/ Enforcement/ Penalties Temporary impacts may be restored to previous conditions without certification Fill removal amount and method, restoration of vegetation, performance standards, schedule of work, etc. Restoration Program- to resolve minor violations to wetland and buffer If impacts are permanent or violation is not minor (as determined by Director)- Stormwater Certification required Partial waiver communities- must be reviewed by the County 9
Article XIV Prohibited Acts/ Enforcement/ Penalties Questions? Communities- check with your legal counsel 15-104. Notice of Violation- specifications and timelines for compliance have changed 14 days to correct violation or apply for Certification Extra time may be granted but cannot be more than 45 days 15-103. Code Enforcement Adjudication Programunincorporated areas 10