Uploaded on Dec 12, 2009
(As portions of the soundtrack are distorted by wind-across-microphone NOISE, begin playback at LOW VOLUME.)
This video is an assemblage of 21 clips from different perspectives of a small dam and waterfall along a small natural stream.. The dam was completed on November 29, 2009. The peripheral areas still need stone walks, steps, and benches; and the waterfall pool walls need finishing touches.
Work on the foundation began in mid-September 2008, but came to an early close when freezing weather arrived to stay in mid-October. At this point, two rough earthen coffer dams had been built up- and downstream of the dam site, to allow an area of relative dryness (i.e., it wasn't completely underwater!) in which to work. This "dry" area required repeated pumping-out at intervals to make it "workable" (barely!), a situation complicated by springs leaking from the west (to the left when facing upstream) bank of the stream. A trench was dug from above the upper coffer dam to below the lower coffer dam along the east bank, and corrugated plastic drain pipe was installed to act as the water's bypass conduit around the foundation area.
The foundation trench for the dam wall was dug through the mud and loose silt down to a naturally-compacted layer of stone and gravel. Large stones were piled into the trench until they formed a solid footing, then subsequent stones were laid in with mortar.
By freezeup in mid-October 2008, the foundation wall had been built up along its length to slightly below the regular stream waterline. Flooding in mid-winter began to erode the upstream base of the foundation in the spot where the stream passed over the wall (well to the left of the finished waterfall); but some emergency filling with large stones, and subsequent shifting and settling of silt around these stones, strengthened this vulnerable area.
All the stone for the project was gathered from a larger stream on the property, about 1/3 of a mile northwest of the dam site, and transported in a John Deere 4-wheel drive, 6-wheel Gator utility vehicle.
Work on the project resumed on September 21, 2009. In late summer, a backhoe had been hired for other work, and while it was there, the pool behind the dam was dredged out. This resulted in moving the upper coffer dam (which had been breached and washed and scattered over winter) farther upstream to a spot that allowed slightly drier working conditions along the dam wall; and progress quickened once the dam wall level got above the normal stream level.
Because the position of the dam had been dictated by the requirement that the waterfall be visible from a building upslope and to the west of the dam, there was a three or four foot gap between the dam wall and the old stream bank, where the water currents had been eroding the bank beneath a large maple tree on the west bank. The Christmas fern and accompanying blue bottle mark the edge of the original stream bank; and the water below this bank was its deepest because of the eroding currents. This hole was filled with soil removed from the steep bank to the west of the dam pool, which was regraded to form a relatively level walking path along the west bank, and a level terrace above, which will allow maintenance by mower, rather than weedeater, necessary previously when the ground was too steep, rough and uneven to mow.
The stream bank on the east side, which had originally dropped several feet down to a sand beach about six feet from the stream edge, was raised and filled with soil from the earlier dredging, which had been spread in the meadow to the east.
The design of the dam was complicated by the site. Upstream, two smaller streams join just above the spot where the upstream coffer dam was rebuilt. The original stream bed curved at this point, but as noted, strong flood currents pushed straight into the bank at the base of the maple tree. This required that the dam wall be its highest on the west side, and that it extend farther along the west bank than the relatively sheltered east bank, to minimize overflow that might wash the fill soil in the old undercut.
The waterfall spillway needed to align with the center of the bridge downstream and the springhouse door north of the dam for aesthetic reasons. This combination resulted in an asymmetric positioning of the spillway along the length of the dam, but to good effect nevertheless.
The waterfall pool is formed by curving walls below the dam, which create a resonant sound of splashing water especially evident from the west side, where steps lead down to the very edge of the water, the last step only a fraction of an inch above the waterline. This offers an opportunity to enjoy the waterfall and pool closeup, immersed in enchanting splashes.
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