Well Designed Plant Concerning SPCC

Asphalt Batch Plant to Operate in Whitefield Gravel Pit

Story date: 07/25/2007
By Lucy L. Martin

A temporary asphalt batch plant in Crooker & Sons' Whitefield gravel pit will rely on a state-of-the-art containment system that was put in place five years ago.

In addition, under a water quality monitoring program developed in 1995, three wells will be sampled prior to startup in mid-August to establish baseline data.

Practices of 20 years ago, when the Topsham based company operated unlicensed asphalt plants in the Whitefield pit with small, inadequate containment berms, prompted opposition and a legal challenge in 1994, initially by the town of Whitefield and then by neighbors and conservationists fearing fuel leaks. They demanded a spill contingency plan, assurances that the buried liner of the spill containment system wouldn't break, and additional test wells to track groundwater movement.

The Sheepscot River is about a half mile away and groundwater is within five feet of the pit floor.

Mark Stebbins, mining coordinator in the Dept. of Environmental Protection's (DEP) Land and Water Bureau, said the company "constructed a secondary containment system" in 2002. "If there's a spill of petroleum products, the system catches it so it doesn't get released into the groundwater. It's like a landfill synthetic liner system."

According to engineering diagrams, 12 inches of compacted sand underlie a 60 or 80 mil geomembrane liner; above that is 18 inches of compacted sand, topped by six inches of compacted gravel. Three inches of bituminous pavement, grade B, covers all.

Stebbins compared one part of the facility to a bathtub into which the whole batch plant is placed. "They back the asphalt plant over and up a ramp and slide it into a containment structure which is like a bathtub. If there's a leak, it's contained."

The system addresses the major concern, which is the possible leakage of diesel fuel, used to run the burner which heats the plant. The storage tank, Stebbins said, might hold anywhere from 10,000 to 20,000 gallons. Escaping liquid asphalt is less of a threat because it thickens as it cools.

Stebbins said, "Crooker has a very impressive design. I can't think of any other in the state like it. He went above and beyond."

The pit used to be licensed under the state's Site Location of Development law. Then, a provision in state statutes allowed previously permitted gravel pits to meet newly designed performance standards, Stebbins said, and Crooker was transferred to that program in 1999/2000. The performance standards program does not require a formal application every time the company wants to make a change, such as bring in an asphalt plant or rock crusher. The pit owner simply has to notify the DEP and the towns where the activity is to take place, in this instance, Alna and Whitefield. Each town received notification by letter on June 25.

The program is "a time saver," said Stebbins, "whereas under the old site law, when they sent in an application, it could be several months before they got a permit. Since October, 1993, we've licensed 650 gravel pits under the performance standards. There were previously 250 in the state under the old site law." Stebbins also said the compliance rate is 87 percent, "which is high compared to other department programs. There are 139 pits left under the old site law, so the program has worked well as an alternative regulatory program."

DEP environmental specialist Molly Zogby, who works with Stebbins, said the company "laid down an impervious liner for an aboveground (fuel) storage tank. All fuel has to be contained in a secondary containment structure designed to contain 110 percent of the fuel being stored."

In an advisory letter dated June 21 to Crooker & Sons, project engineer Steven E. Patch of Sevee & Maher Engineers said the company should make sure that existing contours at the site leave a five-foot separation from the containment system and groundwater. He recommended that three test wells and a spring be used as "water quality monitoring points for the temporary operation of the batch plant.... Samples will be analyzed by an independent qualified laboratory for diesel range organic compounds (DROs) according to a Maine Health and Environmental Testing Laboratory method." After the plant is started up, "a detection monitoring program will be initiated, which will include collection of samples for DRO analysis on a semi-annual basis." Follow-up sampling would occur in the fall and spring of each year "for a period of one year following shutdown of plant operations."

In addition, data collected during the sampling and monitoring rounds are to be submitted annually by Crooker to the DEP's land and water bureau "for review. However, if analysis indicates that the batch plant may be impacting ground-water or surface water quality, the [DEP] will be notified immediately," Patch wrote.

The site's Spill Prevention, Countermeasure and Control Plan requires operator training, routine inspections, monitoring and reporting.

The batch plant, scheduled for operation between mid-August and mid-October, will provide pavement for a Damariscotta region contract Crooker has with the Dept. of Transportation.