Like many towns in Connecticut, Mansfield has seen increased interest in balancing community growth and natural resource conservation. When an undeveloped site is converted into residential housing or commercial areas, roads, roofs, parking lots and driveways replace the native vegetation and soils that were on the site. As would be expected, more water runs off developed sites in response to rainstorms. Pollutants, such as oil from vehicles, bacteria, nitrogen and phosphorus collect on the impervious surfaces and are washed off during precipitation events. Typical development approaches do not provide adequate treatment for this stormwater, and receiving waters suffer a variety of impairments due to these human induced charges in the landscape. Stormwater runoff has been identified as one of the biggest causes of stream quality degradation.

Low Impact Development (LID) is an approach that will help to minimize the impacts of traditional development while still allowing for growth. Pioneered in Maryland (1), this approach is being successfully utilized throughout the country. LID has also been adopted as the preferred method of design in the 2004 Connecticut Stormwater Quality Manual (2). In addition to protecting ecosystems and receiving waters, the LID approach can often result in cost savings on projects.

This form includes five areas of focus to help guide planning for your project; additional information on each focus area is provided at the beginning of the relevant form section.

• Assessment of Natural Resources
• Preservation of Open Space
• Minimization of Land Disturbance
• Reducing and Disconnecting Impervious Cover
• Installing LID Practices

References:

1. Prince George's County, Maryland. 1999. Low-Impact Development Design Strategies: An Integrated Approach. MD Department of Environmental Resources, Programs and Planning Division.
2. CT DEP. 2004. Connecticut Stormwater Quality Manual.
3. US EPA. 2007. Reducing Stormwater Costs through Low Impact Development (LID), Strategies and Practices. EPA Publication Number 841-F07-006.

Based on the type of information requested, we recommend that this form be completed by the professional engineer responsible for design of the project.

Due to individual site differences, not all practices will apply to each property. Identify practices that have been applied and explain why other practices have not been used. For more information on LID practices and how to implement them, please refer to the 2011 Low Impact Development Appendix to the Connecticut Stormwater Quality Manual.

Please contact the Department of Planning and Development at PlanZoneDept@MansfieldCT.gov or 860.429.3330 with any questions.

The following information is needed to complete this form:

• Project Name. The project name should match the project name that is used on the application submitted to the Inland Wetlands Agency or Planning and Zoning Commission.
• Project Location - Street Address if available; Tax Assessor Parcel Identification Number(s) if no street address has been assigned.
• Natural Diversity Database (NDDB). A copy of the latest NDDB map produced by the Connecticut Department of Energy and Environmental Protection (CTDEEP) identifying whether the site has the potential to contain State or Federal listed species or significant natural communities. If the site is located within an NDDB area, the following additional information will be required:
  
  • A copy of the completed form requesting NDDB review from CTDEEP
  • A copy of CTDEEP's response/review

In completing and submitting this checklist, I hereby certify that all information provided is true and correct to the best of my knowledge.

Ideally, LID is considered early in the site planning process. The objective is to allow for the development of the property, while maintaining the essential hydrologic functions of the site. A thorough assessment of the existing natural resources on the site needs to be performed, so that essential features can be preserved, and suitable sites for development can be identified.

Cluster design can complement the LID approach. For example, cluster subdivisions provide a key way to protect natural resources while still providing landowners with the ability to develop their property. In most cases, the number of residential units allowed in a cluster subdivision equals the number allowed under conventional subdivision regulations. Cluster design can also be used in commercial and multi-family developments by clustering buildings and site improvements to reduce land disturbance and preserve open space.

Once the development envelope is defined, the goal is to minimize the amount of land that needs to be disturbed. Undisturbed forest, meadow, and wetland areas have an enormous ability to infiltrate and process rainfall, providing baseflow to local streams and groundwater recharge. Construction equipment causes severe compaction of soils, so after development, even areas that are thought to be pervious such as grass, can be quite impervious to rainfall.

With careful planning, the overall percentage of impervious cover in a proposed project can be minimized. Roads, driveways, sidewalks, parking lots, and building footprints can be minimized to reduce impacts, but still provide functionality. With proper planning, runoff from impervious surfaces can be directed to pervious areas such as grass or forest, or to LID treatment practices. It should be noted that every project is unique, and not every LID practice will be appropriate. For example, sidewalks or bike paths may be an asset to a new subdivision, if there is some connection to existing pedestrian travel routes. However, sidewalks may not be needed in other settings, and would add unnecessary costs and impervious cover. The objective is to evaluate each site individually and determine the most appropriate management techniques to reduce impacts to waterways.

There are a variety of practices that can be used to maintain the pre-development hydrologic function of a site. For more detail on the following practices, see the references listed in the introduction to this form:

• Bioretention areas or rain gardens are depressed areas in the landscape that collect and infiltrate stormwater.
• Vegetated swales can be used to convey runoff instead of the typical curb and gutter system, and they can also infiltrate and filter stormwater.
• Water harvesting techniques can be employed, so that stormwater can be a resource rather than a waste product.
• Pervious pavements allow rainfall to pass through them, and can be installed instead of traditional asphalt or concrete.
• Green roofs can reduce stormwater runoff through evaporation and transpiration through plants, and they can help save on heating/cooling costs.

LID represents a change from typical design approaches. Proper installation and maintenance of LID practices is critical to their performance. Therefore, installation should be performed by someone with LID experience to avoid costly mistakes. With proper design and installation, LID can provide multiple benefits including decreased construction costs, reduced impacts to receiving waters, increased habitat for wildlife, beautiful landscape features, and increased property values.