«Landslides, ‘slope erosion Cause siltation A NEW report by Thurber :: Engineering confirms the ‘» Capilano reservoir will contin- ® ue to experience landslides. » By lan Noble \ News Reporter 3 _ The engincering firm's study of the stability of the reservoir's west ‘shoreline shows that clusters of land- », Slide and erosion activity occur in the + study areas at intervals of 15 to 20 3 years, 4 -_. Although remedial measures can i slow the cycle, said the report. they : will not stop the cycle in the reser- voir, The lake supplies the North hore with water. Pointing to a massive October 995 landslide in the area, the Thurber report said: “A new slide from the same site will likely occur ‘after a number of decades. Other ites on the same slope will experi- ce Similar instability in the mean- time.” Steep reservoir slopes are subject sto weathering and failure, continued the report. The products of such aweathering accumulate on flatter NEWS photo Mike Wakefield THE CAPILANO reservoir will continue to experience slides due to soll and siope conditions lin- ing a portion of the iake. The resulting sediment has a negative impact en our drinking water. Periodically, said the report, the softened slide bris fails during heavy rain and flows toward the servoir, “ Such slides occurred in 1985, October 1995 and December 1995. . 2: On March 16, approximately $510,000 in sta- 3 bilization work to the October slide site was com- pleted. | On Wednesday, the Capilano reservoir was laced on-line for the first time since January, when repairs commenced. The Thurber report did contain some good the southern part of the study area. Thurber esti- ‘mated the volume of suspended sediments enter- ing the reservoir from smail streams on the west In addition, erosion of the shoreline area during rainstorms produces an estimated 200 to 500 tonnes of suspended sediments annually. The Capilano River, three large streams on the west side and all streams on the cast side of the reservoir produce additional suspended sediment. said Thurber. : However, Thurber engineer David Smith said the Capilano produces perfectly good water most of the time. . The Capilano reservoir, which provides 40% of the Greater Vancouver Regional District's water supply, is more prone to turbidity and murky tap water than the Seymour and Coquitlam reservoirs. However, in the future North Shore residents and other consumers of Capilano water may beneiit from a plan to pipe water from Coquitlam reser- voir, which provides the clearest water. Administrator of water planning Tom Heath said a Westerly Transfer project now under way will bring water from the Coquitlam reservoir to the North Shore. That may allow the water district to shut down Capilano in the fal! and winter — the time when the Capilano experiences frequent tur- bidity problems. : He said the Capilano’s contribution is needed in summer, when water demand doubles and Capilano reservoir produces good quality water. Heath said it casts about $3,000 a day to pump water and purchase it from the Coquitlam reser- voir, where most of the water rights are owned by B.C, Hydro. In the future, the water district may be able to trade power generated at Capilano reservoir with Coquitlam water, said Heath, He explained the water district is currently looking at installing a $10-million underground power generating station. The “very preliminary” project will require provincial approval, he said. A power-for-water exchange is just one of a number of scenarios the water district is looking at regarding the power project, he said. shoreline at ,000 tonnes a year. acteria exceeds ealth inspector says water is safe to drink ‘THREE NORTH Shore municipalities are 4 among those that did not mect bacteria control guidelines for drinking water in 1995. News Reporter According to the Greater Vancouver Water District's Quality Control Annual Report, North Shore ‘municipalities exceeded B.C.’s Safe Drinking Water Regulation for bacterial contro) in late summer and fall. ; . y However, Rick Kwan, senior public health inspec- * HE sor for North Shore Health, said the results are nothing ’ new and the water is safe. “Ef you look at the past annual reposts. they always mention something like: that,” che said, adding an increase in water-borne diseases has not been noticed. In total, only four of 15 municipalities met all the bacteriological requirements for the entire year. North Shore: municipalities are in the middie of the pack % among Lower Mainland municipalities for meeting the bacteria regulations, said the report. 4. To meet bacteria reguiations, no more than 10% of t samples of chlorinated water should test positive for ‘total coliform bacteria, stated the water quality Teport. ' Generally, bacterial regrowth occurs when water is “* arm in late summer and fall, stated the report. i In 1995, the North Shore was no exception, Up to “15% of tests exceeded coliform regulations in the f August-September period, said the report. _ ¥- However, in October and November . readings spiked locally with up to 20% ot tests containing col- form bacteria. At that time, massive landslides turned Capilano reservoir water muddy. In turn, the Capilano water supply was shut. off and Scymour water was piped to the North Shore. For rea- sons not fully understood, bacterial regrowth is worse in areas supplied with Seymour water, suid the report. The Seymour reservoir routinely supplies much of North Vancouver City and portions of North Vancouver District. Although coliform regrowth is not caused by direct contamination of the water system, “it indicates condi- tions exist for the proliferation of certain types of path- ogenic bacteria should they enter the system,” said the report. High coliform levels also make interpreting true water quality more difficult. Meanwhile, the report said other water quaiity problems remain. They include turbidity in the source water, corrosive water and questions about the risk from low levels of infectious protozoa, including giar- dia and cryptosporidium. Kwan said cases of the intestinal parasite giardia on the North Shore have dropped recently. Eleven cases of cryptosporidium were reported last year, with 12 in 1994. He added such cases cannot be tracked to the water supply. In 1995, the Capilano reservoir, which supplies West Vancouver and parts of North Vancouver City and District, was taken out of service for turbidity readings that reached more than six times the maxi- mum allowed by the Canadian Guidelines for Drinking Water Quality. In the fall, when turbidity readings from Capilano were high, Seymour, the back-up systein for the North Shore, also experienced similar problems. The result was brown water in North Shore taps for three weeks and a jump in bottled water sales. Seymour snow low THE MOST recent snow- pack measurements taken in the Seymour watershed show a low water supply. By Michael Becker News Editor As a result. two-day-a-week lawn sprinkling restrictions will be a reality for the summer. Snow-pack readings conduct- ed at Orchid Lake on March 27 reveal 2 water level equivalent of about 65% of the 20-year aver- age for the time of year. ; The snow-pack is at a similar level to that posted in 1992, the lowest year on record. However, Greater Vancouver Water District (GVWD) staff believe the combined snow-pack and watershed lake levels are sufficient to supply the region’s water demands for the summer. Last week the Seymour Lake reservoir was 95% full and near- ing overfiow. Earlier this year the Jake level in the Capilano reservoir was lowered to allow for repair work to be conducted at a major !and- slide that occurred in October. . Work at the site was complet- ed mid-March and the lake is being refilled.Szaff anticipate the lake will be full by the time the high demand for water kicks in for the summer period. The third reservoir, Coquitlam Lake, is operated by B.C. Hydro. DC The utility had asked the GVWD for permission to do some maintenance work in May and June. The GVWD denied the request due to low snow-pack conditions and the - reduced |, water level at Capilano Lake. - NEWS photo Mike Wakefietd REMEDIAL WORK on this watershed slide site was completed last month.