Hearn’s Pond dam project comes in under its budget
By Lynn R. Parks
Previous dam washed out on August 11, 2001
The Hearn’s Pond dam project, completed two weeks ago, came in under budget, according to Bruce Jones, project manager with the Department of Natural Resources and Environmental Control (DNREC).
The state budgeted $600,000 for the project and while he did not have the final figures, Jones said that repairing the dam cost “well under that, closer to $500,000 than $600,000.”
But that does not mean that the project was all that the state division had hoped. While the central part of the 90-year-old dam, including the spillway and the gates, meets the latest safety standards, the remaining two-thirds of the dam remain the same as they were last August, when rushing water produced by torrential rains pushed over the dam and allowed the pond to drain.
“Had we had adequate funding, we would have liked to have replaced the entire dam,” Jones said. As it was, state funding allowed DNREC to replace about a 150-foot section in the nearly 400-foot dam.
The old dam was a crib structure, meaning that it was made of a wooden frame filled with sand, dirt and debris.
Shortly after the dam collapse, John Hughes, director of soil and water conservation for the Department of Natural
Resources and Environmental Control, said that hollows in the dike (possibly caused by the stumps of long-ago cut trees which were part of the crib’s fill and which subsequently rotted) undermined the dam and allowed it to collapse.
“The presence of high rainfall forced water through the hollows,” he said, eroding the soil and causing the dike to fail.
Jones said that the state has inspected the remaining crib structure and found it to be sound. “There are no problems that we foresee there,” he said.
The new section of the dam has at its core iron sheet piling, covered with a layer of clay to prevent water from getting through to the iron.
In addition, it has stone pilings at its base, on both sides, so that if water does crest the dam, it will not erode the soil around it. “This way, the dam wouldn’t wash out,” Jones said.
The section also has two new spillway gates, which can be lowered or raised, to allow water to go under or over the dam. “This is a huge improvement over the old dam,” Jones said. “Before, it just had stop logs and to allow more water to go over, you had to pick up the logs.”
The new gates are operated by wheels on the dam.
Last August, Hughes said that inspection of the dam would have detected the hollows that allowed the dam to fail. The dam had last been inspected in 1973.
Delaware still has no dam inspection program. But in its last session, the state Senate passed a resolution asking DNREC to prepare legislation to put such a program in place.
The state agency is to have the legislation ready for the start of the legislative session in January.
Hearn’s Pond, created over 100 years ago to power a grain mill, covers an area of 53 acres and when full has a mean depth of 4.4 feet; at its deepest, it is 9 feet. It is fed from the west by Buck’s Branch and spills into Williams Pond.
Its dam broke Saturday, Aug. 11, 2001, when the Seaford area received between eight and 12 inches of rain, depending upon which area of the city from which the measurements were taken.
Jones said that the rate at which the pond fills will be determined by the amount of rainfall we receive. The new gates are open, to allow the stream that connects Hearn’s and Williams ponds to still have a water flow. “To do otherwise, in this kind of heat, would mean a fish kill,” Jones said.
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