environmental impact study

PROJECT SITE:

ARBOR TRAILSVILLAGE OF LISLE, DUPAGE COUNTY, ILLINOIS

PREPARED FOR:

K. HOVNANIAN HOMES1806 S. HIGHLAND AVENUE

LOMBARD, IL 60148

PREPARED BY:

V3 COMPANIES OF ILLINOIS, LTD.7325 JANES AVENUE

WOODRIDGE, ILLINOIS 60517

JANUARY 18, 2012

ENVIRONMENTAL IMPACTSTUDY

Arbor Trails

VILLAGE OF LISLE, DUPAGE COUNTY, ILLINOIS

V3 Companies of Illinois, Ltd. Environmental Impact StudyJanuary 2012 Table of Contents

Environmental Impact StudyTable of Contents

January 18, 2012

§ Project Overview Narrative§ NRCS Land Use Opinion Application§ Soil Boring Report§ Exhibit 1 – Project Location Map§ Exhibit 2 – National Wetlands Inventory Map§ Exhibit 3 – DuPage County Wetland Inventory Map§ Exhibit 4 – USGS Hydrologic Atlas Map§ Exhibit 5A – DuPage RFM Panel 17043C0805H§ Exhibit 5B – FEMA FIRM Panel 17043C0163A§ Exhibit 6 – NRCS Soil Survey Map§ Exhibit 7 – Wetland Delineation

Arbor Trails

VILLAGE OF LISLE, DuPAGE COUNTY, ILLINOIS

Arbor Trails Subdivision V3 Companies, Ltd.Village of Lisle, IL Environmental Impact Study

Project Overview

January 18, 2012

The proposed Arbor Trails residential subdivision will provide residential single family housingand increased recreational opportunities in the Village of Lisle and the overall central DuPageCounty housing market.

The purpose of this project is to construct a residential subdivision on 60 acres of property, inLisle, DuPage County, Illinois, which is within the central DuPage County residential housingmarket.

The subdivision will consist of 97 single family lots 52’x120’ in dimension and 66 single familylots 75’x130’ in dimension. The required public roadways, infrastructure and stormwatermanagement will be provided within the development. In addition, a small open space park willbe constructed next to a natural area which includes a preserved 5.58 acre wetland and will bededicated to the Lisle Park District. The parcel is located south of Maple Avenue, north ofGreen Trails Subdivision, east of Benedictine Parkway and west of Benedictine University.

The existing site is comprised mainly of undeveloped agricultural fields. The soil types for thesite are Milford, Del Rey, Peotone, Mundelein, Zurich and Muskego/Houghton. This propertysits at the high point of both the East Branch DuPage River and West Branch DuPage Riverwatersheds. Approximately 42.5 acres of the property drains north to the Steeple Run Tributaryto the West Branch DuPage River. The remaining 17.5 acres of the property drains south to theSt. Procopius Creek tributary to the East Branch DuPage River. The existing site currentlycontains no buildings or stormwater detention facilities. Detention is proposed in accordancewith the requirements of the DuPage County Ordinance, by providing restricted outlets to publicstorm sewer systems at a ratio of 0.10 cfs/acre of disturbed area.

The regulatory flood maps for the subject property show Zone A floodplain mapped for both theSteeple Run Tributary and the St. Procopius Creek. The floodplain associated with St.Procopius Creek is not impacted in the proposed condition. However, the floodplain for SteepleRun Tributary is completely displaced in the proposed condition and incorporated into therequired detention facility. Because this property is at the upper limit of this watershed andlimited off-site drainage is tributary to the site, it was agreed to by DuPage County and theVillage of Lisle that the floodplain volume could be replaced by required stormwater detentionvolume, as long as more total volume is provided in the watershed. We have calculated theexisting floodplain volume to be 6.42 acre-feet and the required stormwater detention volume tobe over 13 acre-feet. Therefore the required detention volume will be provided, without theaddition of floodplain compensatory storage volume.

Proposed wetland impacts have been evaluated, and avoidance and minimization alternativeswere considered to the maximum extent practicable. Wetland Area 1, a 5.58 acre emergent/wetmeadow wetland in the southern portion of the property, and Wetland Area 3, a 0.07 acre

Arbor Trails



wooded wetland in the northeast corner of the property, have both been completely avoided.However, in order to develop an efficient and profitable development that meets all Village ofLisle and DuPage County stormwater management requirements, Wetland Area 2, a 1.48 acrewetland along a drainage swale in the center of the property will be impacted. Impacts toWetland Area 2 will be mitigated off-site through the DuPage County in-lieu-fee wetlandmitigation program. Mitigation for impacts to the buffers of Wetland Area 1 and Wetland Area 3will be provided through enhancements of the functions of the remaining buffers.

Public water and sanitary sewer systems are already in place along the perimeter of theproposed project. Connections to the existing systems will occur along Maple Avenue andBenedictine Parkway. The existing systems have adequate capacity to accommodate theproposed development.

Two points of access will be provided to Benedictine Parkway for vehicular traffic. In addition,the site will be linked to adjacent developments via public walkways and a trail system.

In summary, the proposed development fulfills a need for single family housing in the Lislecommunity; infrastructure is in place to support the planned development; and, the project isbeing designed to adhere to regulatory requirements and to mitigate environmental impacts.

WETLAND SUMMARY

1. Wetland Delineation. The 60 acre property was investigated by V3 Companies (V3) onMay 12, 2011 to determine the presence, extent and quality of any wetlands or otherareas under U.S. Army Corps of Engineers (ACOE) and/or DuPage County jurisdiction.Three wetland areas (Areas 1, 2, and 3) totaling 7.13 acres were delineated on thesubject property. Area 1 is an emergent/wet meadow wetland, 5.58 acres in size, at thesouth end of the property. Area 2 consists of restored wetland along a drainage swalethat begins in the middle of the property and extends north towards Maple Avenue. Area2 is 1.48 acres in size. Area 3 is a depression wetland that is dominated by trees nearthe northeast corner of the site. Area 3 is 0.07 acre in size. All three wetlands aresubject to both ACOE and DuPage County jurisdiction and have been classified asRegulatory Wetlands. The delineated wetland boundaries were field verified by Ms.Mary Beth Falsey of the DuPage County Division of Economic Development andPlanning (EDP) on May 24, 2011.

2. Wetland Characterization: Critical vs. Regulatory. Based on Section 15-134 of theOrdinance, the wetlands in the project area have been characterized as regulatorywetlands.

3. Wetland & Wetland Buffer Mitigation Plan. The project will result in direct impacts to onewetland, Wetland Area 2, for a total of 1.48 acres of impact. Impacts to Wetland Area 2will be mitigated off-site through the purchase of 2.22 credits in the DuPage Countywetland mitigation banking program. Due to land planning and stormwater managementconstraints, minor impacts will occur to the buffers around the two preserved wetlands.Buffer impacts will be mitigated through the planting of native shrubs, trees, and

Arbor Trails



herbaceous species in the preserved wetland buffers. These native plantings will greatlyimprove infiltration and other water quality functions of the buffers.

4. Operation and Maintenance Plan. A Wetland Buffer Assessment, Mitigation and BMPPlan & Maintenance & Monitoring Plan has been prepared for the preserved wetlandbuffers.

FLOODPLAIN SUMMARY

Due to the unique positioning of this property at the upper limit of the Steeple Run Tributarywatershed, and limited off-site drainage is tributary to the site, it was agreed to by DuPageCounty and the Village of Lisle that the floodplain volume could be replaced by requiredstormwater detention volume, as long as more total volume is provided in the watershed. It wasalso required to obtain the Village of Lisle approval of this approach, which was done in an April7, 2011 meeting with the Village and their consultant Benes & Associates.

The area which contains the floodplain associated with the St. Procopius Creek floodplain iscontained within a 9.5 acre conservation area which contains a 5.58 acre wetland on the site. Thisarea will be preserved with a conservation easement and will not be impacted by the proposeddevelopment.

DuPage County FEQ Information

DuPage County maintains an FEQ hydraulic model for Steeple Run Tributary for regulatorypurposes within DuPage County. In a 3/11/11 FEQ Data Request, C.Vonnahme of DuPage Countyprovided the PVSTATS Elevations of 726.3 for the 10-year and 727.8 for the 100-year for the subjectproperty. This model represents the “best available data” for the Steeple Run Tributary and theelevations were used for calculating the floodplain volumes on the site.

No information was available for the Zone A floodplain on St. Procopius Creek for the subjectproperty. The DuPage County RFM has floodplain boundary lines which closely match the 730elevation within that area of the site. However, since this floodplain area lies within wetland preservearea that will not be impacted, additional research into this floodplain elevation was not necessary.

Existing Floodplain Volume

The subject property provides 6.42 acre-feet of floodplain volume within the Steeple Run Tributary atthe 100-year base flood elevations. Minimal off-site drainage area (less than 0.50 acres) exists toutilize this volume after development is completed and the subject property is detained per theStormwater Ordinance. This small drainage area is from the landscaped zones along the parking lotof Benedictine University that flows onto the subject property.

Arbor Trails



Compensatory Floodplain Volume

The subject property is not required to provide compensatory floodplain volume because nodrainage area is available to actually utilize this additional volume after the subject property isdetained. Therefore, the site will provide over 15 acre-feet of required detention volume within theSteeple Run Tributary watershed and will restrict peak discharges to less than 3.67 cfs in proposedconditions. These stormwater improvements represent a net benefit to the Steeple Run Tributarywatershed.

STORMWATER SUMMARY

Existing Conditions

The existing 60 acre site is undeveloped agricultural and open space area. Existingresidential properties are adjacent to the subject property on the north, south and west.Benedictine University lies immediately adjacent and east of the subject property.

Approximately 42.5 acres of the site drains north to the Steeple Run Tributary and to theWest Branch DuPage River. The remaining 17.5 acres of the property drains to thesouth and the St. Procopius Creek tributary and to the East Branch DuPage River. Theexisting site currently contains no structures or stormwater detention facilities. Weunderstand that both drainage paths experience flooding problems, but the Steeple RunTributary is more severe. Therefore modifying the ridgeline between the two watershedsto that additional development area would drain toward the St. Procopius Creek wouldbe acceptable, as long as an increase in discharge is from existing conditions is notcreated within that watershed.

Proposed Conditions

As stated in the introduction, the proposed development will consist of an 163 singlefamily residential lots with a small park a 9.5 acre conservation area containing a 5.58acre wetland. The proposed stormwater management system involves the constructionof two detention basins, one located at the north of the property and one located at thesouth of the property.

North Basin – Steeple Run Tributary:A reduction in drainage area has been designed for the northern drainage way for thisproperty. The 42.5 acres in existing conditions has been reduced to 36.73 acres inproposed conditions. This change in ridgeline benefits the residents within the SteepleRun Tributary (currently impacted by flooding conditions) by reducing discharges duringstorm events.

In addition, the existing site has 6.42 acre-feet of floodplain storage volume associatedwith the Steeple Run Tributary. The provided detention volume exceeds 15 acre-feet(more than double) with a peak discharge of less than 3.63 cubic feet per second (a

Arbor Trails



reduction from existing discharge). Therefore development of this property will provide abenefit to the residents who experience flooding within the Steeple Run Subdivision.

South Basin – St. Procopius Creek:The south basin has 17.5 acres draining to the St. Procopius Creek in existingconditions. The conservation area of 9.5 acres will not be impacted within this drainagearea. So only 7.5 acres of the original southern drainage area will be developed. Wehave calculated an existing peak discharge rate of 16.35 cfs during the 100 year, 1 hourstorm event (per critical duration analysis for 100-year discharge).

As mentioned under the north basin section above, there is 5.4 acres of additionaldrainage area which drains to the south and ultimately to the St. Procopius Creek.Based on the DuPage County 0.10 cfs/acre restricted discharge requirements, the peakdischarge from this south stormwater basin is 0.82 cfs, which is less than the existingdischarge calculated from this property into the watershed under existing conditions.Therefore the proposed conditions will provide a significant reduction in discharge ratesto the St. Procopius Creek, even though more area is directed toward this watershed.

STORMWATER DESIGN

Detention Requirements

The detention storage requirements for the proposed development are based on theOrdinance, which stipulates an allowable release rate of 0.10 cfs/acre of development (inthe 100-year/24-hour storm event). TR-20 calculations provided the analysis todetermine the required detention storage volumes at the allowable release rates.

North Basin

The allowable release rate for the north detention basin is 3.67 cfs (0.10cfs/ac * 36.73acres). The TR-20 calculations show that the runoff from the north drainage area wasdetained to 3.63 cfs in proposed conditions. The TR-20 calculations for proposedconditions indicate that 15.88 ac-ft of detention volume is required to reduce the onsiteflow leaving the site to the allowable release rate. The stormwater volume is provided inthe proposed facility with a normal water level of 723.0 and a high water level of 728.44,with a 7.75-inch orifice.

South Basin

The allowable release rate for the south detention basin is 1.34 cfs (0.10cfs/ac * 13.40acres). The TR-20 calculations show that the runoff from the north drainage area wasdetained to 0.82 cfs in proposed conditions. The TR-20 calculations for proposedconditions indicate that 6.00 ac-ft of detention volume is required to reduce the onsiteflow leaving the site to the allowable release rate. The stormwater volume is provided in

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the proposed facility with a normal water level of 730.7 and a high water level of 734.60,with a 4-inch orifice.

Best Management Practices

This 60 acre single family residential project must meet the DuPage County BMPOrdinance for treatment of stormwater discharges. Therefore, BMP’s should treat 100%of the developed area with a 2.0 or greater average importance value.

The developed area of the project is collected in the stormwater system, or directed byoverflow routes, so that the entire project is tributary to the north and south detentionbasins. These basins will be native wet bottom detention facilities with wetlandshorelines. The Importance Value for this type of stormwater BMP treatment is 2.0.

Detailed information on the temporary BMPs for sediment and erosion control can befound below.

Sediment and Erosion Control Plan

This Storm Water Pollution Prevention Plan (SWPPP) was developed consistent with therequirements of the National Pollutant Discharge Elimination System (NPDES) GeneralStorm Water Permit for Construction Activities.

The plan, properly implemented, should result in the discharge of water to theenvironment without the violation of water quality standards.

The purpose of this plan is to:

• Describe best management practices (BMPs) to minimize erosion and sedimentrunoff at the site,

• Identify, reduce, eliminate, or prevent the pollution of storm water, and• Prevent violations of surface water quality or groundwater quality standards.

Schedule of Implementation for Stormwater Plan

Erosion control measures shall be installed before site construction commences.

The intended sequence of the construction activities is as follows: clearing and grubbingfor haul road access, installation of erosion and sediment control measures (i.e.stabilized construction entrance, construction fence, silt fence…etc.), haul roadinstallation (mulch or other natural material to preserve existing tree root systems frommachine traffic), dam modifications, riffle installation, installation of wetland plugs andseed (including blanket and/or mulch as shown on the plans), final stabilization ofdisturbed areas, ongoing maintenance of erosion control measures, removal oftemporary erosion control measures.

TITLE: PROJECT AND SITE LOCATION:

BASE LAYER: PROJECT NO. FIGURE: SHEET:OF:

CLIENT: QUADRANGLE: DATE: SCALE:K. Hovnanian T&C Homes

at Illinois, LLC1806 S. Highland Avenue

Lombard, IL 60148

ESRI World Street Map

Project Location MapMaple Avenue and Benedictine Parkway

Lisle, Illinois

11022ARBOR I

1"= 700'11/03/11

11

N/A

Project Location

V3 Companies7325 Janes AvenueWoodridge, IL 60517630.724.9200 phone630.724.9202 faxwww.v3co.com

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500 0 500 1,000250Feet

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CLIENT: QUADRANGLE: DATE: SCALE:K. Hovnanian T&C Homesat Illinois, LLC

1806 S. Highland AvenueLombard, IL 60148

USGS Topographic Map (1993)

National Wetlands Inventory MapMaple Avenue Property

Lisle, IL

11022ARBOR II

See Scale Bar11/03/11

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Wheaton

Project Location


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610 0 610 1,220Feet

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DuPage CountyWetland Inventory Map Maple Avenue and Benedictine Parkway

11022ARBOR III


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DuPage County WetlandsRegulatory Wetland

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USGS Hydrologic AtlasMaple Avenue and Benedictine Parkway

Lisle, Illinois

11022ARBOR IV


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Wheaton

Project Location


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610 0 610 1,220Feet

K. Hovanian T&C Homesat Illinois, LLC

1806 S.Highland AvenueLombard, IL 60148

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REGULATORY FLOODINSURANCE RATE MAP

Maple Avenue PropertyLisle, IL

11022ARBOR IX

NTS12/20/11

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Wheaton

±Project Location

TITLE: PROJECT:

PROJECT NO.: EXHIBIT: SHEET:OF:

BASE LAYER:

CLIENT:QUADRANGLE: DATE: SCALE:


K. Hovanian T&C Homesat Illinois, LLC

1806 S.Highland AvenueLombard, IL 60148

N/A

DUPAGE COUNTY DIGITAL FLOODINSURANCE RATE MAP

Maple Avenue PropertyLisle, IL

11022ARBOR VIII

NTS12/20/11

11

Wheaton

±Project Location

TITLE: PROJECT:

PROJECT NO.: EXHIBIT: SHEET:OF:

BASE LAYER:

CLIENT:QUADRANGLE: DATE: SCALE:


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WTITLE: PROJECT AND SITE LOCATION:




AirPhoto USA (2008)

Soil Survey ofDuPage County, Illinois

(1999)Maple Avenue and Benedictine Parkway

Lisle, Illinois

11022ARBOR VII


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N/A

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610 0 610 1,220Feet

Wetland Area 2

Wetland Area 3

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AirPhoto USA (2008)

Wetland DelineationMaple Avenue and Benedictine Parkway

Lisle, Illinois

11022ARBOR VI


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environmental impact study

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