Swimming warnings at beaches and shell-fishing bans along thousands of acres of waters are signs that the state's current rules limiting storm runoff aren't working in coastal counties, state water quality regulators say.
The acres of coastal waters permanently closed to shellfishing have increased about 13% in the past two decades, state data shows. Today, about 76,000 acres of coastal waters are permanently closed because of high pollution levels that make the oysters and clams dangerous to eat, according to the state Division of Shellfish Sanitation. An additional 43,000 acres closed temporarily because of bacteria after one- to two-in. rains.
The state Division of Water Quality is seeking to toughen the stormwater rules in the 20 coastal counties to curb the polluted waters that rush from highways, parking lots and housing developments.
Environmentalists, homeowners and state officials want the state to adopt tougher limits, saying runoff not only affects shellfish but human health when swimming beaches must be closed because of high bacteria levels. Meanwhile, home builders say the changes would raise the cost of building at the coast and lead to an increase in high-density development at the water's edge to justify the expense.
Current regulations allow subdivisions to be built so densely that they overwhelm the land's capacity to filter mud, feces and chemicals from roofs, roads and yards before the pollution reaches the water. The current rules allow developers to build on up to 25 % of a tract of land before controls are required.
The new rule would require developers to design stormwater controls such as detention ponds and basins to limit runoff within a half-mile of shellfish waters when they build on more than 12% of a tract. Scientists say that water quality suffers when more than 10% of a lot is built upon without having well-designed controls to capture rainwater before it rushes pollutants into nearby waterways.
At present, developers are usually only required to get a stormwater permit if the development disturbs an acre or more. The rules would lower that to a quarter acre.
The rules also would require wider buffers of grass, shrubs and other vegetation along waterways to slow and filter runoff. The current requirement is 30 feet, and the proposed change would raise that to 50 feet.