This video documents the process of excavating a trench and installing the initial sections of a 6-inch PVC penstock for a small-scale hydroelectric system. The project's primary challenge is encountering extensive, solid rock, which requires renting a second mini-excavator with a hydraulic hammer. The narrative covers the strategic planning to dig the trench without draining the pond, the arduous process of breaking and removing rock, and the careful installation of the pipe. Key steps include bedding the pipe in rock-free clay, creating a compacted clay anti-seep plug, and installing a 6-inch butterfly valve. The video also details significant equipment-related work, including managing rental machinery, dealing with galling on stainless steel hardware, and a substantial fabrication project to adapt a wider 36-inch bucket to the host's excavator for future backfilling. The video ends abruptly when the host's excavator suffers an electrical failure.
From Pond to Power: The Challenge of Digging the Penstock Trench
0:40 Strategic Planning: To avoid building a coffer dam and draining the pond, the plan is to dig the trench in stages, install the pipe and a valve, and then backfill a section with compacted clay to create a waterproof plug before connecting to the pond.
5:07 Initial Miscalculation: The creator realizes his initial ditch plan was flawed; he forgot the intake pipe needs to start 3 feet below the water's surface, not just below ground, requiring the entire trench to be significantly deeper.
12:16 Hitting Unexpected Rock: Progress halts upon hitting a solid layer of rock, a major complication requiring a change in strategy and equipment.
13:04 Renting a Rock Hammer: A second mini-excavator with a hydraulic rock hammer is rented for $430/day to break through the rock layer, as it's a more effective solution than trying to use a larger bucket excavator.
17:53 Trench Safety: The creator enters the deep, un-shored trench to inspect the work, noting that while this is common practice locally with stable clay, it is not an OSHA-compliant or recommended practice.
34:00 Trench Completion: After extensive hammering and digging, the trench is completed, measuring approximately 85 feet long and up to 8.5 feet deep at its deepest point.
47:25 Pipe Installation and Sealing: The 6-inch PVC pipe is laid on a bed of rock-free clay. A rubber anti-seep collar is installed and clamped to the pipe to prevent water from leaking along the outside of the penstock.
53:27 Compacting a Clay Plug: To seal the trench, imported clay is backfilled in layers ("lifts") and heavily compacted with a jumping jack compactor to create a dense, waterproof barrier.
1:02:04 Installing a Sensor Conduit: A separate 3/4-inch conduit is laid high in the trench to allow for running sensor wires to the pond in the future.
1:04:16 Expensive Valve Assembly: A 6-inch butterfly valve is installed. The valve itself was relatively inexpensive ($90), but the required PVC flanges and stainless steel bolts brought the total cost to approximately $260.
1:08:32 Stainless Steel Galling: A significant setback occurs when the stainless steel bolts for the valve gall (cold weld) during tightening with a power tool, requiring several to be cut off and replaced. Lesson: use anti-seize and tighten stainless hardware slowly by hand.
1:14:05 Bucket Modification Project: To use a more suitable trench compactor, a wider trench is needed. This leads to a major fabrication project where the creator cuts the mounting brackets off a 36-inch backhoe bucket and welds on new custom brackets to fit his excavator.
1:24:39 Cliffhanger: Equipment Failure: Immediately after successfully mounting the newly modified bucket, the host's excavator develops an electrical problem and will not maintain voltage, halting all work.