THE DIGGER

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To be most effective, the dam should rest on a pair of sill timbers that traverse the stream, lying flat on the bottom and butted into the banks. To insure that the dam does not slide, an elaborate anchoring technique was suggested in the N.Y. State Bulletin. A trench is excavated about two feet wide, four feet deep into the banks, the base level with the streambed. If stream water is high, it may be diverted to one side by temporary dams made of logs or stone. Here on the Podunk, to save labor and comply with Vermont regulations against stream course alteration, we found low-water construction best.

Drift bolts are used to pin the twin timbers to the streambed, and an additional log is entrenched about four feet upstream. The sills are then tied to this anchor log with galvanized poultry wire. The pond maker drills one-inch holes every six feet or so in parallel sills and pins down the base by sledge hammering three-quarter-inch concrete reinforcing bars through the logs, deep into the streambed. Six-foot lengths of rebar sunk five feet deep leave a foot to crimp over and hold down the sills. Obstructions in the streambed may be sidestepped by repositioning the bolts or backfilling and weighing down the butt ends of the sills. Additional drift bolts should be pinned two feet to either side of the joints. The six-inch anchor log is then entrenched about four feet upstream of the sills, flush with the streamed, and drift-bolted or otherwise firmly secured. The chicken wire is then used to tie the sills to the anchor, as well as create a ramp to sweep water over the dam. The wire is blanketed over the width of the stream and secured to the anchor log and sills with galvanized nails or staples. Fine brush is layered over the wire and anchored with flat stones to complete the seal. Finally, two logs of similar girth are fitted into the sill crevice and spiked at the outside ends, leaving a midstream gap of a foot or two. The central opening is then cut wide enough to pass the entire flow of the stream into the center of the pond. This trimming should be synchronized with a run of low water. Additional spikes are added to secure the logs, with an eight-inch board nailed over the exposed sills to cleat the wire.

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