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Village of Thornton, IL
Cook County
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Table of Contents
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[4-3-2006]
A. 
It is hereby determined that:
1. 
Land development projects alter the hydraulic response of local watersheds and increase storm water runoff rates and volumes, flooding, stream channel erosion, and sediment transport and deposition;
2. 
This storm water runoff contributes to increased quantities of water-borne pollutants, and;
3. 
Storm water runoff, soil erosion and non-point-source pollution can be controlled and minimized through the regulation of storm water runoff from development sites.
B. 
Therefore, the Village of Thornton establishes this set of water quality and quantity policies applicable to all surface waters to provide reasonable guidance for the regulation of storm water runoff for the purpose of protecting local water resources from degradation. It is determined that the regulation of storm water runoff discharges from land development projects and other construction activities in order to control and minimize increased in storm water runoff rates and volumes, soil erosion, stream channel erosion, and non-point-source pollution associated with storm water runoff is in the public interest and will prevent threats to public health and safety.
[4-3-2006]
The purpose of this chapter is to establish minimum storm water management requirements and controls to protect and safeguard the general health, safety, and welfare of the public residing in watersheds within this jurisdiction. This chapter seeks to meet that purpose through the following objectives:
A. 
Minimize increases in storm water runoff form any development in order to reduce flooding, siltation, increases in stream temperature, and streambank erosion, and maintain the integrity of stream channels.
B. 
Minimize pollution caused by storm water runoff from development that would otherwise degrade local water quality.
C. 
Minimize the total annual volume of surface water runoff that flows from any specific site during the following development to not exceed the predevelopment hydrologic regime to the maximum extent practicable.
D. 
Reduce storm water runoff rates and volumes, soil erosion and pollution, wherever possible, through storm water management controls and to ensure that these management controls are properly maintained and pose no threat to public safety.
[4-3-2006]
A. 
This chapter shall be applicable to all subdivisions or site plan applications, unless eligible for an exemption or granted a waiver by the Village under the specifications of § 7-13-4 of this chapter. The chapter also applies to land development activities that are smaller than the minimum applicability criteria if such activities are part of a larger common plan of development that meets the following applicability criteria, even though multiple separate and distinct land development activities may take place at different times on different schedules.
B. 
To prevent the adverse impacts of storm water runoff, the Village has developed a set of performance standards that must be met at new development sites, if determined to be applicable by the Village. These standards apply to any construction activity disturbing one acre or more of land. The following activities may be exempt from these storm water performance criteria:
1. 
Additions or modifications to existing single-family structures.
2. 
Developments that do not disturb more than one acre of land, provided that they are not part of a larger common development plan.
3. 
Repairs to any storm water treatment practice deemed necessary by the Village.
C. 
When a site development plan is submitted that qualifies as a redevelopment project as defined in § 7-13-2 of this chapter, decisions on permitting shall be determined by the Building Commissioner and on-site storm water requirements shall be determined by the Village Engineer. This determination shall be dependent upon the amount of impervious area created by the redevelopment and its impact on water quality. Final authorization of all redevelopment projects will be determined after a review by the Village.
[4-3-2006]
This chapter is not intended to interfere with, abrogate, or annual any other chapter, rule or regulation, statute, or other provision of law. The requirements of this chapter should be considered minimum requirements, and where any provision of this chapter imposes restrictions different from those imposed by any other chapter, rule or regulation, or other provision of law, whichever provisions are more restrictive or impose higher protective standards for human health or the environment shall be considered to take precedence.
[4-3-2006]
If the provisions of any article, section, subsection, paragraph, subdivision or clause of this chapter shall be judged invalid by a court of competent jurisdiction, such order or judgment shall not affect or invalidate the remainder of any article, section, subsection, paragraph, subdivision or clause of this chapter.
[4-3-2006]
APPLICANT
A property owner or agent of a property owner who has filed an application for a storm water management permit.
CHANNEL
A natural or artificial watercourse with a definite bed and banks that conducts continuously or periodically flowing water.
DETENTION
The temporary storage of storm runoff in a storm water management practice with the goals of controlling peak discharge rates and providing gravity settling of pollutants.
DETENTION FACILITY
A detention basin or alternative structure designed for the purpose of temporary storage of stream flow or surface runoff and gradual release of stored water at controlled rates.
ILLINOIS URBAN MANUAL
The Illinois Urban Manual developed by the USDA Natural Resources Conservation Service and the Illinois Environmental Protection Agency current edition.
INFILTRATION
The process of percolating storm water into the subsoil.
LAND DISTURBANCE ACTIVITY
Any activity that changes the volume or peak flow discharge rate of rainfall runoff from the land surface. This may include the grading, digging, cutting, scraping, or excavating of soil, placement of fill materials, paving, construction, substantial removal of vegetation, or any activity which bares soil or rock or involves the diversion or piping of any natural or man-made watercourse.
MWRDGC
Metropolitan Water Reclamation District of Greater Chicago.
OFF-SITE FACILITY
A storm management measure located outside the subject property boundary described in the permit application for land development activity.
ON-SITE FACILITY
A storm water management measure located within the subject property boundary described in the permit application for land development activity.
REDEVELOPMENT
Any construction, alteration or improvement exceeding 1.0 acre in areas where existing land use is high density commercial, industrial, institutional or multi-family residential.
STORM WATER MANAGEMENT
The use of structural or non-structural practices that are designed to reduce storm water runoff pollutant loads, discharge volumes, peak flow discharge rates and detrimental changes in stream temperature that affect water quality and habitat.
STORM WATER RUNOFF
Flow on the surface of the ground, resulting from precipitation.
WATERCOURSE
A permanent or intermittent stream or other body of water, either natural or man-made, which gathers or carries surface water.
[4-3-2006]
A. 
Permit Required. No land owner or land operator shall receive any of the building, grading or other land development permits required for land disturbance activities of one acre or more without first meeting the requirements of this chapter prior to commencing the proposed activity.
B. 
Application Requirements.
1. 
Unless specifically excluded by this chapter, any land owner or operator desiring a permit for a land disturbance activity shall submit to the Village a permit application.
2. 
Unless otherwise exempted by this chapter, a permit application must be accompanied by the following in order that the permit application be considered: a storm water management concept plan and a maintenance agreement.
3. 
The storm water management plan shall be prepared to meet the requirements of § 7-13-5 of this chapter.
C. 
Application Procedure. Applications for land disturbance activity permits must be accompanied by four sets of plans submitted to the Building Commissioner.
[4-3-2006]
A. 
Waiver of Eligibility Criteria.
1. 
Every applicant shall provide for storm water management as required by this chapter, unless this requirement is waived by the Village.
2. 
The minimum requirements for storm water management may be waived in whole or in part upon request of the applicant, provided that at least one of the following conditions applies:
a. 
It can be demonstrated that the proposed development is not likely to impair attainment of the objectives of this chapter.
b. 
Alternative minimum requirements for on-site management of storm water discharges have been established in a storm water management plan that has been approved by the Village and the implementation of the plan is required by local chapter.
c. 
Provisions are made to manage storm water by an off-site facility. The off-site facility is required to be in place, to be designed and adequately sized to provide a level of storm water control that is equal to or greater than that which would be afforded by on-site practices and there is a legally obligated entity responsible for long-term operation and maintenance of the storm water practice.
d. 
The Village finds that meeting the minimum on-site management requirement is not feasible due to the natural or existing physical characteristics of the site.
e. 
Non-structural practices will be used on the sites that reduce: a) the generation of storm water from the site, b) the size and cost of storm water storage, and c) the pollutants generated at the site. These non-structural practices are explained in detail in the Illinois Urban Manual.
B. 
Assurances Required for Waiver. In instances where one of the conditions above applies, the Village may grant a waiver from strict compliance with these storm water management provisions, as long as acceptable mitigation measures are provided. However, to be eligible for a variance, the applicant must demonstrate to the satisfaction of the Village that the variance will not result in the following impacts to downstream waterway.
1. 
Deterioration of existing culverts, bridges, dams, and other structures.
2. 
Degradation of biological functions or habitat.
3. 
Accelerated streambank or streambed erosion or siltation.
4. 
Increased threat of flood damage to public health, life and property.
[4-3-2006]
Unless judged by the Village to be exempt or granted a waiver, the following performance criteria shall be addressed for storm water management at all sites:
A. 
All site designs shall, to the maximum extent possible, establish storm water management practices to control the peak flow rates of storm water discharge associated with specified design storms and reduce the generation of storm water runoff. These practices should seek to utilize previous areas for storm water treatment and to infiltrate storm water runoff from driveways, sidewalks, rooftops, parking lots, and landscaped areas to the maximum extent practical.
B. 
To protect stream channels from degradation, a specific channel protection criterion shall be provided as prescribed in the Illinois Urban Manual.
C. 
Certain industrial sites are required to prepare and implement a storm water pollution prevention plan, and shall file a notice of intent (NOI) under the provisions of the National Pollutant Discharge Elimination System (NPDES) general permit. The storm water pollution prevention plan requirement applies to both existing and new industrial sites.
D. 
Prior to design, applicants are required to consult with the Village to determine if they are subject to additional storm water design requirements.
E. 
The calculations for determining peak flows as required by the MWRDGC shall be used for sizing all storm water management practices where applicable.
[4-3-2006]
A. 
Detention basins shall incorporate design features to capture storm water runoff pollutants. In particular, designers shall give preference to wet bottom and wetland designs in locations adjacent to or near existing wetlands or in other areas where they are suitable and acceptable to the Village and all flows from the development shall be routed through the basin.
B. 
Dry basins with low flow bypasses may be preferred in certain developments to enhance multiple uses where suitable and acceptable to the Village. Retention and infiltration of storm water shall be promoted throughout the property's drainage system to reduce the volume of storm water runoff and to reduce the quantity of runoff pollutants.
C. 
The drainage system should incorporate multiple uses where practicable. Uses considered compatible with storm water management include open space, aesthetics, aquatic habitat, recreation, wetlands and water quality mitigation. The applicant should try to avoid using portions of the property exclusively for storm water management.
[4-3-2006]
A. 
The requirements of Section IV(D)(2)(b) of NPDES permit No. ILR10 including management practices, controls and other provisions at least as protective as the requirements contained in the Illinois Urban Manual, 2002, or most recent edition.
B. 
The long term operation and maintenance of all BMP's shall be provided for.