Not everyone agrees ~ with the proposed plan Michael Becker Newsrooms Editor mbecker@nsnews.com THOSE who stroll across Cleveland Dare invariably pause halfway to marvel at the power of the water | cascading down its spillway. The dam is an engineering wonder, 3 giant concrete and steel plug holding back a lake with a surface area of 670 acres (271 hectares) filled with approximately 16.5 billion gallons of water to help quench the region’s thirst. At the crest wt m) above the high water mark at English Bay, the dam seems permanently fixed into place and impermeable. Yet from the day it was officially complet- ed in 1954 it has leaked water through its eastern abutment. While the dam is connected to solid bedrock to the west, at the east abutment the main buried rock valley extends in depth to “below sea level and is tilled with a complex mix of silt, sand, gravel and glacial tl. The area includes an upper and lower aquifer. The Greater Vancouver Regional District (GVRD) is about to embark on a $25-million Project to upgrade the cast abutment of the dam to protect the water supply and ensure ° public safety. The project will see ‘the construction of a seepage control blanket, a three-metre thick " concrete liner, that will cover the east abut- “ment reservoir slope of the dam below the full water level. Said GVRD senior engineer David Siu, The concern about seepage through the east abutment was recognized right after the dam . was built. Ever since, the GVRD has been werking: with consultants, has a monitoring program, and drainage tunnels were put into the dam to control the problem.” . Siu said the upgrade will “avoid potential © pip! ag problems through the east abutment. SIF there is erosion happenin wo re > ground, a pipe could be formed. If th “propagates back to the reservoir, then | would be a failure,” he said. - According to Frank Huber, the G VRD" 's senior project engincer for the east abutment ‘upgrade, the goal is to. build a.260-metze extension’. to the: existing seepage control blanket. cre “Right now approximately 1,600 litres per- minute seep through the cast abutment, » draining through tunnels on. the cast side of 2 the dam.. When the work is finished that vol- ume, is expected to be reduced by roughly ~ half... :,. Construction has already ‘started on a “water pipeline forthe Capilano fish hatchery to compensate for a reduction in water supply > during the ‘ construction’. period and after- wards. Said Siu, “Kight now. the hatchery “receivés water. from two sources: one from an “intake in the dam and also from groundwater drainage from the east‘abutment.” ‘To com- phote North Vancouver Museum and Archives | “THIS steel ball was used! to knock ‘down trees to accommodate the Capilano reservol The area was. 3 cleared by the spring of 1953. the spillway, 449 feet (137 GVAD senior engineer David Siu points out the extent of the werk area for tt the east abutment sespege control project at. Cleveland Dam. The work will extend to an area now framed bya log boom. : pensate, the GVRD is placing two pump wells in the watershed and a new pipeline roughly 2,000 meires long and eight inches in diame- ter. Construction cn the pipeline began mid- November. The seepage control job is expected to begin in March and is set to be completed by July 2002. Nasi Siu, “The contractor will start at the top, do the excavation and then the reservoir wil be drawn down during the summer.” In September the lake will be brought down to the. 120-metre elevation. At that point the -reservoir, which supplies approximately 40 per cent of the region's water, will be taken off-line. It. will continue to supply water to the fish hatchery downstream of the dam. The contractor will build a cut-off wall at the 126-metre point of the lake. It’s a trench that will be filled with plastic concrete (a flex- ible’ concrete). Said Siu, “Once the wall is constructed, they will build a roller-compact- “ed concrete blanket up the slope. On the upstream face of it, there will be a granular fill zone as well as rock fill zone for wave protec- tion.” Construction. will take place up to 12 hours a day, six days a week over an 18-month : period. Some of the work will take place on a 24-hour-per-day basis in the late fall and win- ter of 2001-2002. The reservoir is set to returis to its full level by June 1, 2002. The job requires the removal of a proxi- mately 250,000 cubic metres of clay, silt, sand and gravel. Some of the ‘material will be replaced to the newly graded surface to con- struct the blanket. : Excavated soil will be disposed of at sever- al sites in the Capilano watershed to reduce truck traffic on Capilano Road. Five hectares of Capilano watershed forest, will be cut down to make way for piles that will be visible from Grouse Mountain. Construction of a sound barrier to reduce truck noise: from Mainline Road will begin ahead of the originally scheduled . January start. Barrier construction work will start in . the coming week, Siu said. Engineering consultants . Kiohn-Cri Crippen presented the GVRD with a report on the Cleveland; Dam in 1996..The document in part looked at the consequences of a breach of the east abutment. The report notes that in 1992 the dam was upgraded to pass the “probable maximum flood” and to withstand the “maximum cred- ible earthquake event.” However, Klohn- Crippen recommended remedial construction phoio North Vancouver | Museum and Archives . THIS photo taken in June 1952 shows a view across a canyon now filled by the Clevetand Dam. ; ‘be: “in. Focus” to reduce the risk of piping failure. The engineering company looked -at a most probable piping failure scenario — through a soil strata made of silts and fine sands at the east abutment. An outflow of. - water at the east abutment breach. would cause flooding downstream in 1.5 to two hours. . Flooding would occur just downstream of. the Upper Levels Highway bridge at Cagilano River. The flood would be contained within: the banks of the canyon to that point. The Capilano fish hatchery would be inun- dated to a depth of 30 m (160 feet). Downstream of the Upper Levels Highway : bridge the flood would. overflow the. river banks and cause flowing water . depths ‘of petween four metres to 12 metres (13 to 40 eet) Flooding on | the right bank in. West Vancouver would reach to just west of Park’ Royal mall. The left bank in North Vancouver. District would see flooding extend to: McKay.’ Creek. The. southwest corner of the province,” home to the North Shore, is rated the: most” hazardous: earthquake region in C anada, - according to geologists. West Vancouver resident: Jack Sunell - worked for the GVRD as an engineer before °- he retired. He believes the GVRD_- doesn’t need to spend $25 million to address. the seepage problem at Cleveland. Dam. By com- parison, the total cost of the dam, its fixtures * andthe. clearing of the reservoir was $10. 7. million back in the 1950s. : “> » Said Sunell, “Fundamentally it (the: seep: { : “age project) should be looked at. What [ve asked Len Hayton (GVRD assistant commis- sioner) in a letter, is to delay this project for a -year and let’s have.a good look-at it. : “However the people on the North Shore. “are so concerned about it that all the GVRD See s Engineer page 5° Coming i in Sunday Focus . NEXT week in Sunday Focus Deana ‘Lancaster spends some time volun- teering with the Christmas Bureau. To suggest a feature story that deserves to. ‘write to, Martin Millerchip, North’: Shore. News, 1139. Lonsdale “Ave.,” - North Vancouve V7M 2H4, fax 985-2104 or