Tag Archives: USA

Did you know not all penstocks are constructed using steel?

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This post provides a background on an extraordinary feature of the walk between Wayatinah and Catagunya Power Stations along the Derwent River.   It is about one of the great surprises of this  ‘walking the Derwent’ project and, as such, reminds me that even the most ordinary of explorations can unearth new discoveries (for those not familiar with an industry – in this case, the industry involved with penstocks).

Okay okay okay I know some readers will have rolled their eyes wondering what a penstock is.  A penstock is a very large pipe that is laid downhill through which water falls at high speed to an electricity generating power station.  Refer to photos in some of my earlier posts such as: Derwent River water passes via the township of Tarraleah .

My typical experience of penstocks, as conduits for water gushing into electricity generating power stations, is of massive steel structures.  I suspect this would be the expectation for others who have seen Tasmania’s penstocks only from the vantage point of our highways.  For people like me, the wooden penstocks feeding Wayatinah Power Station are astounding and therefore I thought it would be of value to undertake some research and learn more. Andrew’s photo below shows the wooden penstocks emerging from an underground tunnel and sloping down towards the Wayatinah Power Station.

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The questions which come to mind include, are there any other wooden penstocks in Tasmania, what wood is used, when were they built, why weren’t they built with metal, who built them, how effective are they, and what is their life span. In my research a constant term was ‘stave’. A stave is a narrow length of wood with a slightly bevelled edge to form the sides of barrels, tanks and pipelines, originally handmade by coopers.

After a little research I now know that wooden penstocks are not unique to Tasmania and have been built in a number of countries including Britain, Canada and the USA. For example, wooden penstocks were built for hydroelectric facilities in Lincoln County, Wisconsin, USA as shown in this article.  This web site contains a great deal of construction and other information which I imagine is similar to that for Tasmanian wooden pipelines, and therefore worth reading. The photo below, from that website, shows redwood penstocks at the Thomson Hydroelectric Station in eastern Minnesota, Wisconsin.

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The website answered some of my questions: “Why wood? First and foremost, keep the wood thoroughly wet and it will not rot. If there is an issue, it has to do with the quality of the metal bands. Expansion joints are not required as the wood absorbs the water and expands. Steel restraining bands are used and the wood will expand against those. The metal bands are used only to provide strength. Even when they corrode and lose their strength, the wood will hold together and the bands can be easily replaced. The carrying capacity exceeds that of metal pipe, in large part because the interior walls remain smooth and do not form tubercles. The wood components are easily transported to the sites, which can be remote. No massive hoisting apparatus is needed. They do not require concrete foundations, but “float” on the gravel. The wood is easy to bend, so the contractors can follow a more natural contour; for example, bending around curves. There is no need to cover them. The wood has natural insulation. They can last for 40-50 years. Simple carpentry can be used for repairs. Assembly is easy.

Why do we see so any leaks? Leaks do occur at the end of a stave, at what is called the butt-joint, most often when combined with a breakdown or severing of a steel band at that point. In addition, steel plates are sometimes placed in the slots at each stave end, and these steel plates can corrode. Also, some erosion can occur at the end of a stave, and develop into a hole. In this instance, the steel band in that area might corrode and sever, and the pressure of the water inside might break off a section of the stave, however small. Metal corrosion also sets up a mild acidic condition. The acid can degrade the wood. There can be a breakdown in the staves when the water pressure inside varies a lot. You will seldom see wooden penstocks for example in positions where turbines can vary the water pressure output in large degrees. This creates what is known as the hammer effect which can beat up a wooden penstock quickly. It’s best to try to keep the inside water pressure as even as possible. This said, small leaks can self-repair as the wood expands. Even large breakdowns in the staves can be repaired. In most instances, the leaks are tracked closely and there is very little risk of a catastrophic failure. “

The hole in a penstock and the story of its repair speedily within one week for the Jackson Hydro Station in New England, USA can be seen here. Another rupture coverage, this time in Quebec, Canada is covered here.  I was surprised when this website included photos of other wooden penstocks around the world including a photo of one of Tasmania’s wooden penstocks.  It looks remarkably like Wayatinah’s penstock, and there are outbuildings in view and some dates as well.  Perhaps a blog reader can make a more accurate identification.

It seems there are only two Tasmanian power stations being supplied by water flowing down wooden penstocks: Lake Margaret Power Station (not on the Derwent River) and Wayatinah Power Station.   Wikipedia  explains the situation in relation to the Lake Margaret Power Station here. For more information refer to the fact sheet for Upper Lake Margaret Power Station, the fact sheet for the Lower Lake Margaret Power Station, and a  note regarding Innovation and heritage feature in Lower Lake Margaret redevelopment. Photos of the pipeline can be seen in Lake Margaret Power Scheme A Conservation Management Plan. I found the photos on pages 11 and 19 particularly helpful with pinpointing the location.

In relation to the wooden penstocks feeding the Wayatinah Power Station,  a You Tube video is worth watching. Page 25 of the booklet ‘The Power of Nature’ includes a photo of the woodstave penstocks at Wayatinah. Other informative photos of dams and power stations and penstocks associated with other parts of the Derwent River are also presented.  Most are glamour shots taken from excellent locations and, after the gritty often basic photos which I have taken, these make the extraordinary engineering feats look even more magnificent and significant. This website offers the following information:  “Wayatinah is the sixth station on the Nive/Derwent cascade and is downstream of Liapootah HPP. Water is supplied from a small storage lake called Wayatinah Lagoon and diverted into a 2 km tunnel to two 1.3 km low-pressure wood stave pipelines. Finally, water drops 56 m through three steel penstocks to the powerhouse.”

Now the scene is set for the story of the walk between Wayatinah and Catagunya Power Stations.

Getting perspective

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I discovered the following graphic on the Australian Native T-Shirts website.

For readers who do not know Australia well, note Hobart is located at the southern end of the island state of Tasmania at the bottom of the country.  Slightly east of Hobart is where the Derwent River flows out into the sea.  The source of the Derwent River is located north west of Hobart roughly in the centre of Tasmania.

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A comparison map showing Australia and the United States of America is located at the site ‘On Walkabout’.

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Finally, I found a most amusing map with multiple overlays of Australia across the world.

Australia-over-the-world

Seeing such images certainly helps me to understand the scale of our nations.

Claremont beside the Derwent River

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I have wondered why there has been so much interest from USA readers for my posting about the Claremont Bowling Club.  The Club is an ordinary lawn bowling club the like of which is found in every town and city across Australia.  My blog site statistics do not indicate which part of the USA my readers come from, so more research was required.

The name Claremont derives from the French for clear mountain, and was introduced into England by refugee French Hugenots in the early 18th century.  The concept of clear mountain works here in Hobart because our town of Claremont sits comfortably at the feet of Mount Wellington.

There a city named Claremont in Sullivan County, New Hampshire, USA. It was named after Claremont, also known historically as ‘Clermont’, an 18th-century Palladian mansion of Thomas Pelham-Holles, Earl of Clare less than a mile south of the centre of Esher in Surrey, England.  This New Hampshire city is located between the Ascutney State Park and the Hawks Mountain area to the west and Mount Sunapee to the east.  Presumably offering clear mountains.

In addition, Wikipedia informs me that “Claremont is a college town on the eastern border of Los Angeles County, California, United States. Claremont is known for its many educational institutions, its tree-lined streets, and its historic buildings. In July 2007, it was rated by CNN/Money magazine as the fifth best place to live in the United States. Due to its large number of trees and residents with doctoral degrees, it is sometimes referred to as “The City of Trees and PhDs.”

Our Claremont in the City of Glenorchy within the Greater Hobart Area is very different than the Californian town with the same name.

In America, the Gold Rush of 1849 opened up California so I suspect the name Claremont was probably given by someone remembering their English heritage when the town was created in the 1880s, or by someone who had travelled west from the New Hampshire town of the same name.  I understand that the peaks of Mount Baldy, Mount San Antonio, Timber Mountain and others in the distance overlook the Californian city.

So now I have either or both California readers on the west coast of USA and New Hampshire readers on the east coast of the USA.  Will the real reader/s stand up!

The great and wonderful Sydney to Hobart Yacht race is about to enter the Derwent River

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For 69 years annually on Boxing Day (26th December), over 100 yachts have set sail from Sydney Harbour for the internationally renowned Sydney to Hobart Yacht race.  Their well-trained crews have great ambitions of becoming line or overall winner depending on the size and class of their yachts.

The website (http://rolexsydneyhobart.com/about-the-race) explains this race is an egalitarian event, attracting yachts as small as 30-footers or large maxis, sailed by crews who range from weekend club sailors to professionals from the America’s Cup and Volvo Ocean Race circuits. The Rolex Sydney Hobart Race 2014 is a classic long ocean race open to anyone who owns a yacht that qualifies for this challenging event and which meets all the safety requirements of a Category 1 safety race.

Today is the exciting one for Hobart residents, thousands of yachtie fans and plane loads of tourists who expect to see the first two towering maxis come over the final line later this afternoon.  As I type this posting, an Australian yacht Wild Oats XI (which has won the race 7 times) leads the USA maxi Comanche which is trailing by 10 kilometres. The rest of the fleet are over 140 kilometres north and none of those yachts can be expected to arrive until tomorrow at the earliest.

But, for today’s two maxis, the big trial will be sailing the final 11 nautical miles of the Derwent River to the finish line.  A change in the wind is forecast and this could be to Comanche’s advantage.  The history of this race is littered with leaders who are overtaken during the last leg on the Derwent due to fickle, conflicting or no winds. Currently the winds around Hobart are north-westerly 15 to 20 km/h and are expected to shift south to south-easterly 15 to 25 km/h in the early afternoon then become light in the late evening.

As I sign off, Wild Oats XI has entered Storm Bay which is the last expanse of water before the Derwent River.

Check out the website http://rolexsydneyhobart.com/ for stunning photos of the yachts and in a few hours you will see the arrival of the first two in Hobart, on this gorgeous sunny blue sky day.