City preaches, practices stormwater management

Like many cities, Chattanooga, Tenn., has experienced rapid growth without a sufficient erosion control program and overall stormwater infrastructure. Growth eliminated forests and pasture land and replaced it with buildings, roads and large parking lots, adding to erosion and urban runoff. Concrete ditches, catch basins and large pipe conduits to carry the new quantity of water actually expanded the problem of pollutants in receiving streams.

Although the city’s growth has been positive in many ways, federal and state NPDES regulations to reduce sediments and other pollutants in stormwater have changed the way Chattanooga and others now need to manage stormwater.

For its part, the city is now putting a reinforced vegetative cover in all channels, such as roadside ditches, that it digs or maintains. This cover reduces the velocity of water and thereby helps control erosion, reduce pollution and protect the area’s receiving bodies of water.

To help establish this vegetative cover, the city is using erosion control matting manufactured by locally based Synthetic Industries. In low-velocity channels, a biodegradable, open-weave matting is staked on top of seed, fertilizer and mulch, while a permanent, 3-D matting is installed after seeding in high-volume areas. To date, no reseeding has been necessary despite several record rainfalls.

While the city has changed its own practices, the story is different in the private sector. Changing the thinking of the construction work force away from baring the ground and/or concreting and toward more use of vegetation on slopes and channel banks has been difficult.

The city has found that smaller construction sites actually cause more runoff than big sites since the smaller sites tend to be less prepared to control this runoff. Thus, the city’s erosion control requirements go beyond the NPDES minimum of five acres and apply to land-disturbing activity of any size.

Since ignorance of the city’s requirements has been the most common excuse for non-compliance in the private sector, education and training have been a major focus. Chattanooga started with three-hour training sessions on private job sites. These training sessions were somewhat helpful, but many contractors continued to fail to comply with erosion control requirements. City inspectors, frustration grew, and the problems of runoff persisted.

So, the city’s department of public works announced in its spring newsletter the start of a new contractor certification program, sponsored by the department’s stormwater management office and the Chattanooga Home Builders Association. The course involves presentations, videos and slides as well as a test before and after the course. The successful attendees are awarded a card that will, in the near future, be required of all contractors planning to engage in any land-disturbing activity.

The class teaches the use of efficient, cost-effective methods of controlling erosion rather than complete reliance on typical silt fences and straw bales. Such measures advocated in the course include diversion dikes, temporary sedimentation ponds and brush barriers. Participants in the class learn that pleading ignorance will no longer work. To date, approximately 150 people have completed the course, which will soon be mandatory for all city inspectors, designers and construction personnel, as well as for the private sector.

The Stormwater Management program also includes a facility pollution prevention program. For existing facilities, it is a good housekeeping program outside where it comes in contact with rainwater. Employee instruction is vital in the maintenance of the work area and parking lots. Employee training is important to deal with spills and simple routine maintenance of a facility. For new facilities, it also includes maintenance of catch basins, floatable skimmers and detention ponds.

Chattanooga’s erosion control efforts and its overall stormwater management program are geared to the use of Best Management Practices, soft solutions, public participation, pollution prevention, education and training, and, if necessary, the city has an environmental court that is used as a last resort.