Low Impact Development

We have been working on a 500 acre, mixed-use development over the last several years. These types of developments just do not happen overnight. They require that the planning take the economic feasibility of the project, the community infrastructure needs, the development’s impact on existing infrastructure, as well as the concerns of the nearby property owners into consideration. As we were finalizing the planning on this project and undertaking the entitlement work (zoning), we began to identify a lot of concerns from some area environmental groups and individuals about the development and its ability to be a sustainable development.

This particular development was located along the James River, which will be directly impacted by the storm water run-off from this development. Typically, developers consider the community’s existing ordinances relating to storm water management as the controlling factor in their development, and they do not often examine those regulations and consider whether they are adequate.

Most communities initially worked to manage the storm water quantity since flooding downstream of development is the most immediate and visible impact from development. Recently, the EPA and State Natural Resource Departments have added water quality concerns to the mix.

Conventional storm water management measures can best be described as “end of pipe” solutions. In that solution, the storm water is collected at the source, piped through an underground system to some sort of a detention basin where it is collected and released over time. The concept is that the flow of the storm water leaving the development will leave it at the same rate post-development as pre-development. The volume of water is much greater so it takes much longer to be released. This is intended to mitigate downstream flooding by letting the drainage ways downstream manage the water volume at the same rate it has always done so. Problems with this relate to the collection of the storm water and releasing it in a point load rather than a distributed manner.

Storm water quality is a little different in that the pollution which is inherent from the rain event usually is carried in the “first flush” or the first one inch of rain. In that rain event, the pollutants from our development are washed off the impervious surfaces (parking lot paving, roofs, sidewalks, etc.) from the surfaces and carried with the storm water down stream. If measures are not implemented to filter this initial flush, those pollutants travel directly into our rivers and streams.

Low impact development (LID) uses integrated management practices (IMP) to address ways to increase the absorption of the storm water at the source, to distribute the storm water rather than to collect it and then also to use vegetated drainage ways to filter and provide for more opportunities for absorption into the ground thereby recharging the water table.

We have ways to increase the pervious surfaces on our sites and still to use them. For example, pervious concrete, or paver stones allows for water to travel into the ground at the source rather than run off. If we provide for a reasonable volume of rock bed underground, the storm water can fill the voids between the rock pieces and be detained there for absorption. This is where that “first flush” of storm water with the pollutants would go. Then, when that system is full, the runoff would then travel off site using the various vegetated drainage ways. These vegetated drainage ways continue to filter and absorb the storm water so that the volume of water that ultimately leaves the development is significantly reduced but it is also much cleaner and better for our environment.

The problem that we face in working with LID in our cities is that the ordinances are not written to reflect the use of LID practices and it often takes special action through the City Council or other bodies to deviate from the existing ordinances. It takes a Public Works staff who understands LID and the benefits of its use and their willingness to work with us to identify the changes necessary and to promote it to the City Leaders.

In this recent development effort we were doing a Planned Development for the entitlements and that was a perfect vehicle to add the LID measures. With the support of the local environment groups and individuals who are committed to sustainable development practices, we were able to quickly sort out some measurable criteria which would work for LID practices and to make the changes in the PD document so that as we move forward on the development the City staff have the ability to deviate from the conventional requirements and allow the LID systems.

We are confident that this effort will be a huge game changer in the development of property going forward. It will be the model, in this community at least, for future development efforts and will help to protect our natural environment so that our kids, and their kids, can enjoy all the natural beauty that we have enjoyed here for centuries. Hopefully, in the future, we can change the standards that communities use to manage our storm water and promote the LID practices for all new development.