Putting the LID on Stormwater (Paul Justus Commentary)

A group of Northwest Arkansas city planners and engineers recently attended the eighth annual Environmental Protection Agency Region 6 stormwater management conference held in San Antonio, Texas.

The conference, designed for builders and developers, vendors of stormwater management equipment, and operators of Municipal Separate Storm Sewer Systems (MS4s), showcased a wide variety of stormwater management programs, practices and techniques.

The Northwest Arkansas representatives had to pay very close attention to the conference because they plan to host the five-state meeting at the new John Q. Hammons Convention Center in Rogers in June 2007.

Much of this stormwater management activity has grown out of the efforts of local and state governments to meet the requirements of the Clean Water Act as established in 1977.

Fifteen MS4s located in the official census designated urbanized area of Northwest Arkansas are in the third year of a five-year program to prevent stormwater pollution.

Public education and outreach is a major component of the EPA stormwater pollution prevention program. The 15 Northwest Arkansas MS4s engaged the University of Arkansas Cooperative Extension Service to carry out the public education and outreach requirements of the five-year program.

Through the educational efforts of the Cooperative Extension Service, local residents are learning that many things that people normally have taken for granted — such as the silt from construction sites, oil and cigarettes on parking lots, excess fertilizer from landscapes, and the dumping of wastewater into storm sewers — all add to the pollution of our stormwater.

Contrary to a general misconception, water going into our storm sewers does not get treated. Instead, it flows directly into our streams, reservoirs, and underground water systems. With the continuous growth in population and building in Northwest Arkansas, stormwater pollution prevention has become a growing priority.

There are many techniques, known as Best Management Practices (BMPs), which people can employ to prevent stormwater pollution. These practices include activities such as regular city street sweeping, the strategic placement of silt fencing and other devices during construction, and the careful application of lawn fertilizers and pesticides.

At the San Antonio EPA conference, a very promising and innovative stormwater management approach, known as low impact development (LID), caught the attention of many participants. LID adopts a basic principle, modeled after nature, that rainfall is managed at the source using evenly distributed small-scale controls.

According to a paper by the Low Impact Development Center Inc., the main purpose of LID is to replicate a site’s predevelopment water conditions by using design methods that infiltrate, filter, store, evaporate and detain runoff close to the source. With a LID approach, stormwater management should not be seen as stormwater disposal into large, costly end-of-pipe facilities located at the bottom of drainage areas. Instead, LID uses cost-effective landscape features located at the lot level. These landscape features include not only open space, but also streetscapes, parking lots, sidewalks, medians and rooftops.

The list of common LID techniques includes: bio-retention cells (also called rain-gardens), grass swales, filter strips, disconnected impervious areas and cistern collection systems. Additional site design methods include reducing roadway surfaces, use of permeable pavement surfaces,and vegetative roof systems.

An important feature to know about bioretention cells is that when properly designed, they are very effective at removing toxic heavy metals and other pollutants from stormwater.

Placed in parking lots, these bioretention “islands” act as valuable filters. Studies show that the mulch, plants and soils in these rain garden systems can remove more than 90 percent of the heavy metals and up to 80 percent of the phosphorus — an important element to reduce in Northwest Arkansas.

The use of LID techniques, which increase on-lot multi-purpose landscaping and vegetation, also can add to aesthetic beauty and, hence, property values.

Additional environmental benefits include not only groundwater recharge and cleaner streams, but also increased urban forest, reduced urban heat, improved air quality, reduced thermal stream pollution and enhanced community appearance. Greener neighborhoods also help increase a neighborhood sense of place and quality of life.

For developers, LID practices offer many economic benefits. LID reduces the cost of stormwater drainage facilities and lowers costs of streets, curbs, gutters and other infrastructure. Also, LID may lower construction costs by reducing the need for mass clearing, grading and sediment controls. Furthermore, LID may allow for more lots by reducing the size of stormwater retention ponds.

According to the Low Impact Development Center, “case studies and pilot programs show at least a 25 percent to 30 percent reduction in costs associated with site development, stormwater fees, and maintenance for residential developments that use LID techniques.”

Given that elected city officials, planners and builders are constantly searching for ways to develop that are both better for the environment and less costly, it may be that we will see more employment of LID techniques throughout Northwest Arkansas. At the ninth annual EPA Region 6 stormwater management conference next year, participants can expect these LID and other best management practices to be demonstrated.

(Paul Justus is a regional planner with the Northwest Arkansas Regional Planning Commission.)