RE: HWY 63:02 HIGHWAY EMBANKMENT REPAIR NORTH OF LABICHE RIVER BRIDGE COMPLETION REPORT

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1 THURBER ENGINEERING LTD. Suite 200, st Avenue EDMONTON, Alberta T6E 6A5 Phone (780) Fax [780) I \ DO THURBER February 2, 1999 File: Alberta Transportation & Utilities Unit #2, Street Athabasca, Alberta T9S 1A9 Attention: Mr. Andy Brown, P.Eng. RE: HWY 63:02 HIGHWAY EMBANKMENT REPAIR NORTH OF LABICHE RIVER BRIDGE COMPLETION REPORT Dear Sir: This letter provides a summary of work undertaken for an embankment repair on Highway 63:02, located approximately 1.5 km north of the Labiche River Bridge northeast of Grassland, Alberta. Thurber Engineering Ltd. (TEL) provided the geotechnical design, prepared drawings for construction, and carried out geotechnical inspection services during construction for the project. The project manager for the project was Mr. Don Law, P.Eng. of TEL. The work was authorized by Mr. Andy Brown, P.Eng. of Alberta Transportation and Utilities (AT&U) and was coordinated by Mr. Nick Bucyk, P.Eng. of AT&U (Athabasca). 1. BACKGROUND The five metre high embankment fill flanking an oxbow feature to the west had been experiencing distress since Subsidence has historically occurred in the roadway surface over a 60 m length, with some minor surface cracking occurring in the pavement surface to the north and south of this zone of major distress (1 00 m length total). Inclinometers and piezometers have been installed at the site by others to monitor slope movements and pore water pressures. GEOTECHNICAL AND GEOLOGICAL ENGINEERING CALGARY /EDMONTON/TORONTO/VANCOUVER/VICTORIA/FT. McMURRAY

2 THURBER ENGINEERING ~ Alberta Transportation -2- February 2, 1999 The roadway embankment was originally constructed through an extensive area of muskeg. From review of aerial photography and site inspection it appears that the embankment likely acts as a long dam between the muskeg area to the east and the Labiche River to the west. Prior to construction in 1997, surface water from the region to the east was directed through two culverts in the immediate vicinity of the embankment failure into the oxbow lake to the west of the highway. A failure in the embankment occurred near the end of June 1997 which formed a scarp extending a distance of 45 m along the southbound lane. The failure movement was in a westerly direction, toward the oxbow feature. It is understood that granular fill material was placed in the area of subsidence and the speed limit was reduced to maintain trafficability through the area. The rate of subsidence increased during the summer of 1997 such that maintenance was required on a weekly and sometimes daily basis to maintain safe driving conditions. 2. PROJECT ACTIVITIES Project activities prior to the initiation of construction included the following: Site inspection and engineering assessment Review of existing information (AT&U geotechnical files and GAEA Report) Initial survey undertaken by Spyglass Consulting Ltd. and EXH Engineering Ltd. Slope stability analysis Clay borrow investigation Pre-construction meeting (on-site August 20, 1997, record attached in Appendix A) Survey layout and borrow area pick-up (EXH Engineering Ltd.) Due to the requirement to get the highway back in service in a timely manner the work was not tendered. Pine-West Maintenance Ltd. (Pine-West), the highway maintenance contractor for the area, was selected by AT&U to undertake the work under their existing contract with AT&U. It is understood that work items not covered under the maintenance contract were dealt with under a separate agreement between AT&U and the contractor. Superintendent duties for the project were provided by Mr. Terry Colosimo, P.Eng. of Pine-West. A fibre optic line located at the toe of the embankment on the west side of the highway was located within the slide mass and was relocated away from the problem area prior to the commencement of construction activities.

3 THURBER ENGINEERING~ Alberta Transportation -3- February 2, 1999 Construction inspection was initiated on September 2, 1997 with some initial site grading undertaken by the contractor prior to this time. The embankment repair and ditch regrading work undertaken by the contractor is described below. Substantial completion of the project was achieved on October 30, Final acceptance was provided by Mr. Bucyk of AT&U on October 30, 1997 as recommended by Mr. Law of TEL, subject to final grading and clean-up in the spring of It is understood that final grading and clean-up operations have been completed by the contractor. Construction supervision was provided by Mr. Brian Gilliatt of TEL. Geotechnical inspection of clay borrow during excavation was undertaken by TEL personnel and load checking for granular haul was performed by a local hire under the direction of Mr. Gilliatt. Asphaltic concrete pavement inspection was undertaken by Mr. Jim Palmer of TEL. Engineering support and site visits during construction were undertaken by Mr. Law. Survey and quantity measurements during construction were provided by EXH Engineering Ltd. New slope inclinometer instrumentation was installed by TEL on October 15, 1997 to replace instrumentation destroyed during construction. Existing inclinometers were extended through the toe berm fill where required. 3. EMBANKMENT REPAIR AND DITCH REGRADING The cause of the roadway embankment failure was determined to be a combination of slope instability due to weak foundation soils below the embankment and high pore water pressures within the embankment. The repair and stabilization design is shown on the attached site plan and crosssection, Drawing No.'s A and -2A respectively (Appendix A). The design drawings correspond in general with the as-built dimensions. The embankment repair consisted of the following major components; A 1 00 m long section of the roadway was cut out to a depth of approximately 3.5 m and was replaced with compacted clay and granular backfill materials. The clay was obtained from a borrow area located 6 km east of the site on the ALPAC road. The granular material was obtained from an AT&U stockpile located 58 km south of the site near Boyle, Alberta. Road crush was obtained from an AT&U stockpile near Wandering River, Alberta. Excavation and backfill operations were staged to allow traffic to pass the site at all times during construction. 08\0:\15\ et Continued...

4 THURBER ENGINEERING Alberta Transportation -4- February 2, 1999 A 600 mm thick granular drainage layer was placed below the fill in this road section to reduce the likelihood of pore pressure buildup in the embankment. A geotextile separation layer was placed above and below the granular layer. A toe berm was constructed along the west flank of the roadway embankment with a width of approximately 15 m beyond the original embankment toe. The berm extends over a length of approximately 230 m. Waste material from the excavation was used as toe berm fill. The surface water flow was directed north of the site to prevent the flow of surface water to the oxbow on the west side of the highway. This work consisted of east ditch regrading and installation of a new 900 mm diameter culvert across the ALPAC road to the north of the site. The centreline culverts crossing the highway at this location were abandoned by constructing a clay plug at the inlet end of each culvert to prevent flow from the east ditch to the oxbow. Selected photographs taken during the project are attached in Appendix B. Daily inspection reports filled out by the TEL inspector are attached in Appendix C. 4. QUALITY CONTROL AND QUANTITY MEASUREMENTS Compaction testing was undertaken on clay fill and granular base course material. The compaction test results are provided in Appendix D and indicate the clay was compacted to at least 95o/o of Standard Proctor maximum dry density and was typically 2o/o to 3% above optimum moisture content. The 20 mm crushed gravel base course was compacted to a minimum density of 1 00 /o of Standard Proctor. Density testing was undertaken on cores taken from the asphaltic concrete pavement. The results of three test cores indicated an average density of 94.9o/o as compared with the Marshall design density. The density is low likely as a result of lower than ideal placement temperatures resulting from the length of haul and cold air temperatures (approximately 0 C). The low density was accepted by AT&U and TEL based on the knowledge that an overlay was planned in early summer It is understood that the overlay design through this area takes into account the potentially weaker pavement through this section of roadway. The asphaltic concrete testing results are included in Appendix D. Table 1 in Appendix A provides a summary of final quantities of excavation, clay borrow, granular fill and miscellaneous items (geotextile, culvert, etc.) which were used by AT&U as a basis of payment for the contract. The quantities of pit run and granular base course were higher than initially estimated due to the requirement to use granular backfill in place of clay when access to the clay borrow source via the ALPAC haul road was shut down due to wet weather.

5 THURBER ENGINEERING Alberta Transportation - 5- February 2, SLOPE MOVEMENTS Instrumentation monitoring is ongoing at the site under TEL's Instrumentation Monitoring Contract with AT&U for the North Central Region. Some minor movement at depth was measured between October 1997 and June 1998 in two of the slope inclinometers. Recent readings (November 1998) indicate that the rate of movement in the two inclinometers has slowed. Continued instrumentation monitoring is recommended at this site. 6. CONTRACTOR EVALUATION The quality of the product produced by the contractor was considered satisfactory, however the contractor was not organized and did not follow his proposed work plan. It was originally anticipated that the project would be completed in a three week period, however a late start by the contractor and inefficiencies in utilization of equipment led to a lack of progress during late August and early September when the weather was favourable. The project was delayed in mid September and early October (Sept. 13 through 21, 1997 and Oct. 8 through 14, 1997) due to wet weather which hampered clay placement and ultimately forced the use of granular fill material to complete the embankment backfill. As a result of the delay the asphaltic concrete pavement was delayed until the weather was cold, resulting in a marginal product subsequently corrected for during overlay. It is expected that the contract could have been administered in a more efficient manner had a contract specific to this work been drawn up. A clear definition of the methods of measurement for payment would likely have averted misunderstanding regarding payment at the end of the contract. 7. CLOSURE We trust this information satisfies your requirements. If questions or concerns arise, please contact the undersigned. Yours very truly, Thurber Engineering Ltd. D. Papanicolas, P.Eng. ~t! D.J. Law, P.Eng. Project Engineer attachments 08\D:\ 15\ et