The Department of Natural Resources (DNR) has proposed guidance regarding the extent of best management practices a developer must implement for the “common plan of development” requirement for construction site storm water discharges. The purpose of the guidance is to answer the question whether a developer has to install storm water management facilities to account for the runoff from the impervious surfaces that subsequent owners will construct on subdivision lots.

The short answer is yes, but it is limited. A developer must develop a storm water management plan that addresses storm water discharges for the development after the construction in the common plan of development is completed. If the full extent of the impervious surfaces is unknown, the developer has to estimate the anticipated impervious surfaces. The developer does not need to address each land-disturbing construction activity that will occur over the life of the common plan of development in its erosion control plan.

The Wisconsin Administrative Code requires that a notice of intent (NOI) be submitted to the DNR or to an authorized local program by any landowner who intends to create a point source discharge of storm water from a “construction site” to waters of the state. Prior to submitting the NOI, the landowner must develop a site-specific erosion control plan and a storm water management plan for each construction site. The landowner must implement and maintain all best management practices specified in the erosion control plan from the start of land disturbing construction activities until final stabilization of the construction site. The landowner also must develop a storm water management plan to address pollution caused by storm water discharges from the construction site after construction is completed, including roof-tops, parking lots, roadways and the maintenance of grassed areas.

A construction site is defined as an “area upon which one or more land disturbing construction activities occur that in total will disturb one acre or more of land, including areas that are part of a larger common plan of development or sale where multiple separate and distinct land disturbing construction activities may be taking place at different times on different schedules but under one plan such that the total disturbed area is one acre or more.”

The DNR has determined that it is not reasonable to require the developer’s site-specific erosion control plan to address each land-disturbing construction activity that will occur over the life of the common plan of development, such as those that may be carried out by purchasers of undisturbed lots within the developer’s planned subdivision. But, at a minimum, the developer’s erosion control plan must control storm water pollution from all land disturbing construction activities carried out under the direction or control of the developer.

The DNR has further determined that is reasonable that the storm water management plan can address the entire construction site, as fully developed under the developer’s common plan of development. Where the developer does not know up front how much impervious area will be developed by subsequent purchaser or whether even some activities will occur, the developer should estimate future development such that storm water management systems are not undersized when the project has been completed.

Comments are due on the proposed guidance by November 19, 2014.

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