Rockdale County may choose to make substantive changes or otherwise customize this practicability
policy. These further changes and customizations are allowable so long as their substance meets the
requirements of Rockdale County’s MS4 permit. EPD is responsible for evaluating MS4 permit and
District Plan compliance, which includes verifying whether changes and customizations are “at least as
effective.” EPD has reviewed this document and their comments have been incorporated.
Conditions that may warrant a Determination of Infeasibility
The GSMM provides broad guidance about conditions that may lead a local jurisdiction to waive or reduce
the runoff reduction requirement. The following conditions may warrant a Determination of Infeasibility
due to economic hardship, risk posed to a protected resource, or other site constraints. To claim
economic hardship associated with various site conditions and constraints, one must demonstrate that
the cost of retaining the first 1.0 inch of rainfall onsite using runoff reduction practices is a minimum of
three times greater than the cost of providing conventional water quality treatment practices.
• Poor Soil Infiltration Rate: The performance of a contemplated runoff reduction practice will be
negatively affected by native soil having an infiltration rate is less than 0.5 inch per hour.
Consideration should be given to infiltration rates throughout the soil profile.
• High Water Table: The seasonal high water table is less than two feet from the bottom of a
contemplated runoff reduction practice.
• Shallow Bedrock: A contemplated runoff reduction practice will require substantial removal of
non-rippable rock, which cannot be excavated except by hammering, drilling, or blasting.
• Extreme Topography: Existing topography of the site requires at least 50% of the proposed
development to have slopes steeper than 3:1, making the use of a contemplated runoff reduction
• Environmental Concerns: A contemplated runoff reduction practice will either negatively affect
or be negatively affected by features such as streams, lakes, wetlands, springheads, frequently
flooded areas, groundwater wells, specimen trees, environmental protection buffers and
setbacks, conservation easements, endangered species, bury pits, sinkholes, septic systems,
existing soil contamination, or proposed hotspot land uses.
• Historic Resources: A contemplated runoff reduction practice will negatively impact buildings,
structures, or historic sites included in the Georgia Historic Preservation Division’s Historic
Resources Survey, listed in the National Register of Historic Places, or that has been recommended
as a historic resource by a Preservation Professional.
• Other Site Constraints: Construction or maintenance of a contemplated runoff reduction practice
will be complicated by laws, rules, administrative procedures, agreements, and other issues
associated with the proposed development, such as zoning setbacks, landscaping standards,
utility easements, ADA requirements, regulatory floodplains, HOA covenants, emergency access
• Other Economic Hardship: Construction of a contemplated runoff reduction practice is
complicated by financial constraints that are unforeseeable, unavoidable, or unmanageable. A
Determination of Infeasibility cannot be based on this factor alone, and this factor shall not
account for more than 50% of the runoff reduction volume.