AWARD OF EXCELLENCE / NATURAL RESOURCES, MINING, INDUSTRY & ENERGY Palo Viejo Hydroelectric Plant
“This is a very innovative project in its application of engineering techniques. It is also admirable for how it responded to the
The Palo Viejo hydroelectric project
in San Juan Cotzal, Quiche, Guatemala is a testament to complexity. Through 20 km. of canals, 0.63 km of tunnel, 0.5 km of inverted siphons, and 1.4 km of steel penstock, the power flow is diverted from the river and creeks at elevations between 1200 and 1190 metres and conveyed to a 305,000-m3 daily storage regulating reservoir. An 85 MW surface powerhouse with two vertical turbines converts 5.5 m3/s of flow and 388 m of head into 370,000,000 kWh each year.
All these components are set in a remote, mountainous, highly seismic region, subject to tropical storms, landslides, and other geological issues. The project itself is situated in a working coffee plantation, presenting a number of social challenges. Innovative solutions were required.
First the geometry of the river meant that a conventional tunnel was not economically feasible. Meanwhile, on the opposite side of the river were two large river valleys which would have required a longer conveyance, multiple powerhouses, and significant additional costs.
Water from five waterways
To solve this problem on behalf of owner Enel Green Power (EGP), Hatch designed the 20-km long surface canal system. The canal system required custom designs to suit the complex nature of the site topography and geological conditions.
Where the risks of landslides were highest, for example, Hatch designed unique structures to divert the slides overtop of the canal. To deal with ponded water produced by landslide blockages, an innovative system of isolation gates and overflow spillways were designed to divert the water into existing dried watercourses. Removable covers protect the open canal from becoming filled with debris due to localized slope instabilities.
To bring water across the two steep valleys with minimal energy loss in a cost effective manner, Hatch designed specialized inverted siphons. These siphons, engineering marvels in themselves, are up to 100 metres in height, span river valleys as wide as 350 metres with slopes as steep as 60 degrees.
Ensuring that adequate environmental protection measures were in place was essential. For example, solutions were needed to ensure that lubricating oils from turbine machinery would not contaminate the river. To address this problem, Hatch devised a unique oil separation technology commonly used in the petrochemical industry consisting of a custom-system comprised of separation baffles and valves. To Hatch’s knowledge, this is the first time the technology has been applied to a hydroelectric facility.
Water returned to watercourses
The project has the environmental advantages of a run-of-river plant. It enables the storage of energy for maximizing revenue through the use of a regulating pond that did not result in any flooding of prime agricultural lands or the need to relocate people. The project returns the water to the watercourse to be used for agricultural and domestic needs.
The community benefits from the project by having green energy and fewer blackouts. As well, approximately 1,000 Guatemalans and 300 Ixil First Nations were hired to construct the project.
EGP committed $1.4 million to conserving the ecosystem of the site and for reforestation. And after ruins of an ancient Mayan sports site were uncovered, a canal was rerouted and a structure was built to protect them.The project was connected to the electricity grid in March 2012. cce
Palo Viejo Hydroelectric
Award-winning firm/owner’s engineer:
Hatch, Mississauga, Ont. (Ian Ainslie, P.Eng.; Alan Mee, P.Eng.; Stephen Perkins, Tech; Mike Ragwen, P.Eng.; Shahin Motamedi, P.Eng.; Dragi Debeljevich, P.Eng.; Ralph Salfi, Tech; Richard Jack, Tech; Jason Molenaar, Tech; Manual Villalobos, Tech.)
Enel Green Power
Other key players:
Solel Boneh (civil
contractor); Voith Hydro (W2W