Stormwater Management


In recent years, regulation of stormwater runoff has undergone drastic changes in Vermont. The design, permitting, construction and on-going operation of stormwater management systems are more involved than ever, and require careful consideration as part of the overall project.


The State of Vermont, Water Quality Division now manages several distinct stormwater permitting programs. The three major programs are:

                   Operational Stormwater Permit (post-construction)

                   Construction General Permit (runoff from construction sites)

                   Multi-Sector General Permit (for industrial activities)


In addition, other state agencies (Act 250, Wetlands) and municipalities often have additional requirements. Navigating the various requirements is entirely possible, but it does require someone who is intimately familiar with the process. Long Trail Engineering, P.C. has extensive experience in stormwater management and its varying permit programs.


Operational Stormwater Permit

This is the “classic” stormwater permit, and what most people think of when it comes to stormwater. This program involves stormwater treatment once a project has been completed. Treatment is required for both quality (sediment removal) and quantity (detaining peak runoff).


For new projects, a permit is generally required when a project creates more than one acre of new impervious surfaces. Impervious surfaces include paved and gravel surfaces, rooftops, patios, sidewalks, etc.


For expansions of existing projects, the trigger for requiring a permit can be as little as 5,000 square feet of new impervious surfaces.


Further complicating matters, the Water Quality Division now looks at the “common plan of development” when determining whether a permit is required. If your project is “linked” to another project by virtue of a state or local permit, then the total impervious area for the entire “common plan” must be considered. Thus, the addition of a new garage to an existing home in a subdivision could require a permit. 


Construction General Permit

This permit deals with stormwater runoff from a project while it is under construction. The goal is to prevent erosion from disturbed soils, and keep what sediment does erode from reaching streams and rivers.


Projects are segregated into three risk categories: low, medium and high. The risk categories depend on the soil type, slope and amount of disturbed soils at any given time.


Low risk projects are the easiest to manage and implement, generally by complying with the state’s low risk erosion prevention handbook. Medium and high risk projects are more complicated, and require site-specific designs for erosion prevention and sediment control measures.


Multi-Sector General Permit

This program deals with stormwater runoff from industrial projects. Most people will never have to deal with the requirements of this permit.


The goal of this permit is to reduce to the extent possible the amount of rainfall over potentially hazardous substances that are part of industrial activity. If you can manage your site to avoid any rainfall exposure, the requirements of the program become quite simple.


If not, a detailed plan for dealing with the exposure is required, among other things. This is incorporated in a site specific Stormwater Pollution Prevention Plan.


Note: this information is provided for general informational purposes only; please contact Long Trail Engineering, P.C. to discuss how the programs might affect you in particular.