Replacing the dam & hut chimney - Swamp Working Bee

The old pond dam was put in 13 years ago, with a solid concrete foundation around a 12” pipe with a cut-off valve. So far it’s been the longest lasting dam, taking into consideration the constant threat of willow tree roots and eel digging action. This season the dam finally blew in a reasonably big way, so we knew we had a big job on our hands. Dad rounded up the materials needed to effect repairs, 1.5 tons of builders mix, cement, tongue and groove treated timber. Paul and dad moved the materials down to the hut which in itself was a horse sized job.

Concrete precursors

I arrived at the hut on Saturday morning – dad, Rick, Jason, Tom and Andrew were in residence and we got started. Dad put in a coffer dam to hold back the flow, and then we dropped in another just upstream of the dam. The tide was way out, which helped us immensely with draining the working area.

The old dam

After a quick meeting to work out the scope of work, Tom got started on the chimney. He toiled all day on the roof cutting away the burned out old chimney, seating the new chimney and capping it off.

Andrew planning

Then, we started digging. Digging was the recurring theme of the day.... we had to remove the clay filling to find the cavity causing all our problems. We removed the fill to below the level of the pipe, drove in new boards on the front facing of the dam and removed the short boards at the rear which appeared to be the root cause of the issue.

Jason Excavating

Removing & replacing facings

We removed the spillway and then under Andrew's professional geotech engineering guidance we cut a channel in which to pour concrete. The trenched concrete was to cover both sides of the pipe down to below stream bottom level and for extra strenth we drove boards down into the base of the trench. Rather than boxing the concrete, we elcted to fill the dam completely with concrete so the big mix was on. Concreting took several hours of grunt in itself, joy, joy joy.

Then we set about building "wings" from the dam facing, to reduce water turbulence and cavitation associated. This in itself required another cubic metre of clay for the filling... by now we were pretty stuffed. The boys were pretty much walking wounded. Tom was dehydrated. But the end was in sight.

We finished after 6, the job having taken 10 hours of grunt. The coffer was released and we packed up and headed back to the hut. I dropped Andrew, Jason and Rick at the ramp and headed back for dinner and a sleeeeep.

Man the mosquitos were thick as pig poo that night!

Sunday it was 3 tired blokes who finally hit the floor. To be honest I awoke at 5 am and went upriver at about 6.15 to get the plants that we had to plant out. There were about 20 cabbage trees and 40 or so flaxes. We had breakfast and then planted the new plants around the ponds. Then we pulled the pin and went home.... a big weekend indeed.