Preliminary Estimate of Water Consumption for the Construction & Maintenance of the Prairie Creek Mine Access Road

Transcription

1 Preliminary Estimate of Water Consumption for the Construction & Maintenance of the Prairie Creek Mine Access Road Prepared by Paul Davidson Kledo Construction Ltd. Fort Nelson, BC December 31, 2010 Page 1 of 7

2 Introduction Kledo Construction Ltd. has been involved in the construction of industrial winter roads for many years in the Fort Nelson, BC area. Typically the roads are built for heavy loads up to 85,000 kg for use by the forest or oil and gas industries. Since the Prairie Creek Mine road is intended for considerably lighter loads (~40,000 kg), construction requirements in terms of water needs may be commensurately considerably less. Therefore, the estimates given here should be considered as conservative maxima. Information provided in this report is based on local empirical knowledge and experience as there have been no known studies regarding water consumption for local road construction. A related report Ice Road Construction in Fort Nelson, BC (see appendix) describes the water consumption for road construction at 130 m 3 per kilometre and for seasonal maintenance at 120 m 3 per kilometre. For construction, muskeg may require more water while overland forested areas may require less water. Typically, the water trucks used in our area can haul m 3 of water per load. The first process in constructing a winter road is to remove the snow from the right of way using snow cats or light dozers. The snow is plowed to the edge of the right of way to allow frost penetration of the opened right of way. Next comes watering and freezing in of the road base. The volume of water used for the base is estimated at 30 m 3 per km, but it is variable due to dry muskeg conditions that may be encountered. When the road base is firm, water trucks and a grader will complete the task of building the constructed travel surface, mixing snow and water capable of supporting the loaded traffic. The volume of water used for the road surface construction is estimated at 100 m 3 per km. Regular daily maintenance of the road surface is required. This may include the sealing of cracks and fissures and snow fills at creek crossings to maintain the safety and integrity of the road and for adequate haul speeds. The volume of water estimated for this activity is 120 m 3 per km. Calculation of Estimated Water Consumption for Construction and Maintenance of Road Road information for this report is taken from Figure 6 20: Prairie Creek Mine Access Road (with Inset Figures) from the CZN Developer s Assessment Report (DAR). 1. Section A: Mine to Tetcela Transfer Facility (84 km) The existing road alignment is already permitted with the exception of the 8.8 km of the proposed Polje Re alignment. This report does not calculate water requirements for this road section because the bed from Km 0 to Km 39 is considered to be of all season condition, the re alignment will require fill placement due to expected permafrost presence, and the remaining road portions mostly traverse a well drained plateau.. Any water needs would be sourced from a supply well at the mine site as annual construction of this road section would occur using equipment captive at the mine site. Page 2 of 7

3 2. Section B: Tetcela Transfer Facility to Liard River Ice Bridge (71 km) This section of road is permitted from Km and Km The remainder consists of proposed re alignments. It is understood that presently, there are two confirmed water sources available, Mosquito Lake at Km 65 and the Liard River at Km 155. It is understood that in the first year, the road will be opened and constructed beginning from the Liard Highway #7, so the water for the road base structure will come from the Liard River. The volume for the construction of the road base is calculated at 30m 3 per km times 71 km = 2,130 m 3. The volume for the construction of the road surface is calculated at 100m 3 per km times 71 km = 7,100 m 3 sourced from the Liard River and Mosquito Lake. The volume for the seasonal maintenance of the road surface is calculated as 120m 3 per km times 71 km = 8,520 m 3 sourced from the Liard River and Mosquito Lake. 3. Section C: Liard River Ice Bridge to Liard Highway #7 (24km) This section of road iconsists of the Old Nahanni Logging Road and part of the Nahanni Butte access road. It can be opened from the Liard Highway #7 to the Liard River. Winter road construction will draw water from the Liard River. The volume for the construction of the road base and road surface is calculated as 130m 3 per km times 24 km = 3,120 m 3. The volume for the seasonal maintenance of the road surface is calculated as 120m 3 per km times 24 km = 2,880 m Table 1: Summary of Water Consumption for Prairie Creek Mine Winter Road 5. Summary Road Segment Source Construction Maintenance Total 0 84 km Not estimated Not estimated km Liard River Lake at km Liard Hwy Liard River Totals (m 3 ) 12,350 11,400 23,750 Note: The volume of the lake at Km 65 has not yet been quantified, therefore it is not known how much water the lake can supply. Any reduction in lake supply would be replaced by the mine and Liard river sources. Information regarding water consumption is based on empirical experience for high capacity roads (loads and speeds) from the Fort Nelson area. Only with operational experience in this location for the required road capacity will we be better able to reliably forecast water volumes required for winter road construction. Page 3 of 7

4 Appendix 1: Winter Road Construction in Fort Nelson, BC Paul Davidson, Kledo Construction Ltd. August 18, 2010 Page 4 of 7

5 Winter Road Construction in Fort Nelson, BC For many years, the forest industry based in Fort Nelson, B.C. constructed winter roads and ice bridges as the predominant access structures for transportation of manufactured logs to the mills. These winter access structures were designed for heavy industrial use and loaded 5 8 axle log haulers could typically reach loads of 85,000 KG. The roads were constructed in November and December, but daily maintenance was required to strengthen and repair the surface through to breakup in late March. Drivers were not permitted to use tire chains except on designated grades. The area generally does not contain significant areas of permafrost. The knowledge and expertise developed by local contractors remains available, but fewer contractors are building roads and bridges. Typically, the forest industry roads followed seismic roads and trails where the vegetation had already been removed from the right of way. Low ground pressure dozers (typically a Caterpillar D5 or 6, and more recently a blade equipped Snowcat) would enter onto the right of way in early November to plow the snowfall from the cleared right of way to the edges, maximizing the area available to construct the road. The snow would be stored in windrows at the edge of the road for later use. Skilled equipment operators removed all the snow and herbaceous vegetation cover without removing the root mat or damaging the moss covering. After the exposed ground was exposed to night time freezing temperatures typically 15 o Celsius for 2 3 nights, road construction would begin. Any significant delay beyond 3 days due to warm or cold weather or operational delays could sometimes affect the success of the next phase. Page 5 of 7

6 In the second phase, water tank trucks with a capacity of 10m 3 (10,000 litres) were used to carry fresh water from approved borrow pits, ponds and lakes to the road surface. Typically the first loads were ½ the full volume to protect the trucks from breaking through the thin frozen upper layer of root mat and soils. In the first pass, up to 6 loads of water would be applied per kilometre. Usually this first pass was about 11/2 lanes wide for a one way off highway road with pullouts. One measure of a good road builder and the longevity and strength of his road was how well he could have the water penetrate into the soils. Good absorption and deep penetration of water provided a sound base to build the road surface. Volume of water used in this phase on average may accumulate to 30 m 3 per kilometre, but can be highly variable depending on ground conditions. Muskeg may require more water while overland forested conditions may require less water. Once the base was built, for the third phase, usually one road grader and two water trucks would work together constructing an ice surface. The water truck would apply water and the grader would sweep snow from the plowed windrow onto the freshly watered surface. Mixing of the snow and water would be used to fill in voids and smooth out the road. Typically, day time temperatures of 25 o Celsius made for good freezing conditions and maximizing construction. Volume of water used in this phase on average may accumulate to 100 m 3, or about 10 full truck loads per kilometre. Regular daily maintenance of the surface is required to seal cracks and fissures and to maintain a smooth travelling surface. Specialized equipment was designed and installed on water trucks whereby a remote controlled blade was attached to the frame to enable drivers to direct snow Page 6 of 7

7 to these road defects and apply water in the same pass. Then road traffic compacted the snow and water to repair the surface. Regular application of water and snow throughout the season was required to maintain the strength of the surface. Volume of water used in this phase on average may accumulate to 10 m 3, or about 1 full truck load per kilometre per week over 12 weeks. Total volume of water for road maintenance could amount to 120 m3 per season per kilometre. This estimate is highly variable, depending on seasonal conditions and traffic. Total annual water consumption per kilometre: Phase 1: building the subsurface = 30 m 3 Phase 2: building the ice surface = 100 m 3 Phase 3: seasonal maintenance = 120 m 3 Total water use for all three phases is about 250 m 3 per kilometre. This is an estimate given for the average conditions observed and worked in the Fort Nelson area for heavy industrial use with traffic flows averaging 100 loaded trucks per day at 85,000 kg per truck. Average loaded speed was variable from kmph. Typically, the NWT Department of Transportation designs and maintains snow roads for 64,000 kg loads with an average rate of speed at 35 kmph. Ice bridges are designed for 64,000 kg with a speed limit of 20 kmph. Water is used sparingly, only for snow fills, very rough road sections and ice bridges. The author acknowledges the expertise, information and assistance provided by Gordie Smith and his employees from G&C Products, a long term road construction contractor in the forestry and oil and gas industry in Fort Nelson. Paul Davidson, RFT Health and Safety Coordinator Kledo Construction, Fort Nelson, BC Page 7 of 7