Low Impact Sustainable Development Design Manual for Morris, Connecticut

In 2018, Trinkaus Engineering was retained by the Town of Morris in northwest Connecticut to write a design manual for the implementation of Low Impact Sustainable Development (LISD) in their community. LISD is next generation terminology for Low Impact Development (LID) as what we are really trying to accomplish is the creation of sustainable developments which are in harmony with the natural environment.
The Morris LISD Manual is a comprehensive document for designers, regulators, and installers to follow to ensure that LISD practices, particularly those which depend on infiltration are designed properly and then can easily be installed by a contractor even if the contractor does not have practical experience with installing LISD practices.
A unique feature of the LISD Manual is a series of matrices to direct designers to choose the most appropriate LISD practice for a site which evaluates the following:
a. Contributing Drainage Area,
b. Percentage of Impervious Area,
c. Hydrologic Soil Group,
d. Depth to Seasonal High Groundwater,
e. Depth to Bedrock,
f. Land Slope,
g. Hydrologic Performance Requirements, and
h. Pollutant Load Reductions.
In addition to these matrices, there are detailed specifications for each LISD practice which are to be implemented in the Town of Morris. Hydrologic modeling of LISD practices here in Connecticut is often not done by a designer to demonstrate that a practice will function as intended. There does not appear to be a common reason why designers do not model LISD practices, but to overcome this issue, a sample modeling analysis using HydroCAD software is provided for a designer to follow.