November 6,

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1 November 6, Jon Lee, EIT Alberta Transportation 2nd Floor, Provincial Building Street Edson, AB, T7E 1T2 North Central Region Edson Area NC76 Hwy 658:02 Bridge File at Bull Creek 2012 Annual Inspection Dear Mr. Lee This report details the observations made during the annual inspection of the Bridge File at Bull Creek site, north of the Hamlet of Blue Ridge on Hwy 658:02. The legal land description of this site is SW W5M. The inspection was conducted by Mr. Ian Darrach, P.Eng. and Mr. Eric Leishman, EIT of Golder Associates Ltd. (Golder) on July 31, Also present on-site during the inspection were Mr. Roger Skirrow, P.Eng., Mr. Jon Lee, EIT, and Jeff Zhang, P.Eng. of Alberta Transportation. 1.0 BACKGROUND This site was last visited as part of a Call-out conducted in October 2011 by Thurber Engineering Ltd. Observed site conditions at that time are available in the Call-out report, dated October 14, 2011, in Section E of the site binder, with additional information regarding the history of the site available in Section A. A geotechnical drilling and instrumentation program was undertaken by Thurber in early This is the first annual inspection report on record for this site. 1.1 Culvert Replacement The site is located approximately 0.5 km north of the Hamlet of Blue Ridge, AB, on Hwy 658:02. Highway 658 is a paved, undivided two lane highway at this location, with a north-south orientation, and crosses Bull Creek, which flows from east to west through a 3.99 m diameter culvert. The horizontal alignment of the culvert is skewed northwest-southeast at approximately 35 o to the highway, with a slight curve to the south near the outlet. The Bridge File for this culvert is The culvert was replaced in 2009 by Klassen Brothers, with MPA Engineering acting as the Prime Consultant. The purpose of the replacement was twofold: 1) the previous culvert was near the end of its service life, and 2) the size of the culvert was increased from a diameter of 2430 mm to 3990 mm. The vertical alignment of the highway was kept consistent with the original grades, with similar embankment side-slopes. Prior to construction, two test holes were drilled along the highway alignment to aid in the culvert design. These boreholes indicate clay and sand fill up to a maximum depth of 10 m. The fill was underlain by native clay over clay till. A 1.5 m thick layer of organic clay was found underlying the fill on the south side of the culvert, while a 1 m thick layer of peat was encountered below the fill on the north side. Golder Associates Ltd Avenue, Edmonton, Alberta, Canada T5P 4C3 Tel: +1 (780) Fax: +1 (780) Golder Associates: Operations in Africa, Asia, Australasia, Europe, North America and South America Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation.

2 Construction began on August 1, 2009 and was completed on November 3, 2009; with paving completed by October 24. Construction consisted of the excavation of the approximately 13 m high embankment in order to remove the old culvert. The material was then replaced once the new culvert was installed, with some unsuitable material being wasted. During construction, several slope stability issues became apparent: Several springs were exposed within the open excavation. Perforated pipe subdrains were added to counter this problem; Slumping of the north side of the excavation was observed; and The as-built reports of the excavation indicate that the slopes were cut at 2H:1V with midslope berms. Slope movements were observed in both the north slope of the excavation and the detour. It was determined in the field that a benched excavation completed in stages would limit stability concerns. 1.2 Call-out Report Distress at the site was first noticed in the summer of 2010, with the highway surface being affected in June A crack and minor settlement was observed over a length of between 3 and 4 m, starting from the shoulder and extending to the midpoint of the southbound lane. A patch was undertaken in this area prior to the Call-out in October of Signs of distress observed during the Call-out inspection included two major scarps in the west embankment, as well as several minor scarps, all of which were located north of the culvert in the west embankment. A culvert survey completed in October 2011 showed 6% sag along two separate sections of the culvert, from rings 14 to 17 and from 23 to 25. These locations correspond roughly with the 1/3 points of the horizontal alignment of the culvert. Remediation options were put forward by Thurber, and included slope flattening (berm construction) or a pile wall to support a portion of the slope. Recommendations included conducting a geotechnical investigation and the installation of slope monitoring instrumentation, which was completed by Thurber in early Investigation In January of 2012, Thurber completed a geotechnical investigation at the site subsequent to the Call-out. The results of this investigation are detailed in a report dated March 30, 2012, and can be found in the site binder. Two boreholes were drilled in the west embankment slope, north of the culvert. It was noted in the report that two attempts were made to complete TH12-3 due to squeezing ground conditions. The stratigraphy encountered at the site consisted of fill material overlying native silt, clay and clay till. A thin layer of rafted clay shale was observed in TH12-4 at 15.5 m below ground surface. A layer of peat was encountered in this borehole as well at a depth of 2.4 m. High plastic clay was encountered in both boreholes, with moisture contents in this material at about 40%, with plastic limits of 20 to 25% and liquid limits of 80 to 84%. One slope inclinometer, nested with one pneumatic piezometer was installed in each borehole. Readings were taken upon completion of drilling, and on February 10 and March 9, Data from these readings indicated that the movement was taking place within the high plastic clay underlying the fill. Rates of movement based on the March readings were 18.9 mm/year and 10.5 mm/year in TH12-3 and TH12-4, respectively. The squeezing soil in TH12-3 mentioned above is located approximately 1.5 m below the indicated movement zone. 2/5

3 The instrumentation was not read during the Spring 2012 cycle, as Golder was not informed until the time of this inspection that there was existing instrumentation at the site. Golder obtained the MPA Engineering s Construction Report from Jeff Zhang while onsite, and received a copy of Thurber s Call-out report and geotechnical report on August 30, A culvert survey was also undertaken as part of the investigation and it was determined that the culvert had deformed along its entire length. This is especially noticeable at the downstream end of the culvert, as shown in Photo OBSERVATIONS Select photographs from the inspection are attached at the end of this report. Any observed changes in conditions since the previous inspection are documented on the site plan. Highway 658 north of Blue Ridge slopes down towards the site, shown in Photo 2, with the low point corresponding to the culvert location. The highway then begins to rise again to the north. The embankment side slopes on each side of the highway are approximately 3H:1V. Two slope inclinometers and two pneumatic piezometers have been installed at this site on the west side of the highway, north of the culvert. In total, the height of the embankment is about 12 to 13 m, as referenced from the streambed. The pavement surface appeared to be in the same condition as described in the previous call-out report. The crack, patched in September 2011, showed no signs of reappearing or reflecting through the patch, shown in Photo 3. No additional settlement was evident from the visual inspection. Visual observations were made of the culvert at the upstream and downstream ends. At the time of the inspection, Bull Creek was flowing at approximately one quarter the capacity of the culvert, as seen in Photo 1. This photo also shows that the sidewalls of the outlet have been deformed since installation, resulting in an elliptical shape of the culvert at the outlet. The main stability issue at the site is the west embankment, north of the culvert, where the instrumentation has been installed. During the inspection, a toe bulge was noted on the west side of the highway, below the slope monitoring instrumentation near the north end of the silt fence surrounding the outlet. This silt fence was observed to be leaning downslope. A tension crack was found beneath the erosion control matting in the same area, just above the toe bulge, as seen in Photo 4. The crack was observed to be up to 600 mm in width, with no height differential, and was filled with water. Several other cracks, approximately 75 mm in width were observed a third of the way downslope on the west embankment. In general, the ground surface was found to be saturated and soft, particularly near the toe bulge, indicating a high water table. 3.0 ASSESSMENT The distress observed during the site inspection is indicative of continued slope movements since the replacement of the culvert. It is anticipated that the culvert will continue to deform as the slope fails unless remediation measures are conducted. As discussed onsite, the culvert was y experiencing 6% sag at the time of the site inspection, and it is understood that repairs are generally undertaken at 15% sag. It is noted that the elevation of the movement zone in SI12-4 corresponds to the invert elevation of the culvert in the downstream section. 3/5

4 It is postulated that the slope of the excavation during replacement of the culvert was over steepened at 2H:1V, and that the high plastic clay layer yielded at that time, reducing the strength to residual. Then, with replacement of the embankment fill, this weakened plane is leading to movements of the sideslope. It is anticipated that higher rates of movement will be experienced during periods of heavy rainfall. 4.0 RISK LEVEL The risk level for this site, based on AT s risk level system, has been determined to be: PF(12) x CF(6) = 72 A probability factor of 12 was chosen since the slide is active with a high rate of movement, that is steady and may be increasing. A consequence factor of 6 is applicable since continued movement will result in additional stresses on the culvert, as well as full or partial closure of the highway. Due to the location of the site, no practical detour is available should a road closure be warranted. 5.0 RECOMMENDATIONS A geotechnical investigation was recently conducted by others, in which slope monitoring instrumentation was installed. These instruments should continue to be read as part of the Geohazard Monitoring Program, with site inspections conducted annually. In the short term, the MCI for the area should closely monitor the embankment and the pavement surface increased signs of distress. Any cracks developing in the pavement should be sealed as necessary to reduce the infiltration of surface water into the embankment. Erosion control measures should also be considered along the slope north of the culvert such that stream flow does not cut into the slope, further destabilizing the toe. Further, the span of the culvert walls should be measured at the five locations noted in Thurber s geotechnical report (marked with spray paint) to determine if further deformation has taken place along the culvert since the last measurement. This should be done on a monthly basis at the present time with results reviewed by Golder in conjunction with AT staff to determine appropriate remediation options, if required. Additional instrumentation readings may be necessary in the near future based on the results of the culvert measurements to confirm rates of movement and pore water pressures. Long term remediation for this site may include berm construction to flatten the slope and buttress the embankment. Consideration may be given to combining this option with subsurface drainage to lower the groundwater table as well. This option will be limited by geometric constraints, and may require rerouting the downstream portion of the creek. Another possible remediation measure is a pile wall to support a portion of the slope. A detailed engineering analysis would be required in order to select the most feasible option. Costs associated with berm construction and pile wall construction may be in the range of $750,000 and $3,000,000, respectively. 4/5

5 6.0 CLOSURE We trust that the information presented in this report meets your present requirements. Should you require any additional information, or further clarification regarding any of the above, please do not hesitate to contact the undersigned. Respectfully Submitted GOLDER ASSOCIATES LTD. Eric Leishman, EIT Junior Geotechnical Engineer Ian Darrach, M.Eng., P.Eng. Senior Geotechnical Engineer EL/ID/sw Attachments: 1. Site Photographs 2. Site Plan cc: Mr. Roger Skirrow, P.Eng., Director of Geotechnical Services, Alberta Transportation n:\active\2012\1376 geotech 2012\projects\ at - edson slope services\7. geohazard sites\nc76\2012\part b - annual inspection\2012 nc76 inspection report.docx 5/5

6 IMPORTANT INFORMATION AND LIMITATIONS OF THIS REPORT Standard of Care: Golder Associates Ltd. (Golder) has prepared this report in a manner consistent with that level of care and skill ordinarily exercised by members of the engineering and science professions currently practising under similar conditions in the jurisdiction in which the services are provided, subject to the time limits and physical constraints applicable to this report. No other warranty, expressed or implied is made. Basis and Use of the Report: This report has been prepared for the specific site, design objective, development and purpose described to Golder by the Client. The factual data, interpretations and recommendations pertain to a specific project as described in this report and are not applicable to any other project or site location. Any change of site conditions, purpose, development plans or if the project is not initiated within eighteen months of the date of the report may alter the validity of the report. Golder can not be responsible for use of this report, or portions thereof, unless Golder is requested to review and, if necessary, revise the report. The information, recommendations and opinions expressed in this report are for the sole benefit of the Client. No other party may use or rely on this report or any portion thereof without Golder s express written consent. If the report was prepared to be included for a specific permit application process, then upon the reasonable request of the client, Golder may authorize in writing the use of this report by the regulatory agency as an Approved User for the specific and identified purpose of the applicable permit review process. Any other use of this report by others is prohibited and is without responsibility to Golder. The report, all plans, data, drawings and other documents as well as all electronic media prepared by Golder are considered its professional work product and shall remain the copyright property of Golder, who authorizes only the Client and Approved Users to make copies of the report, but only in such quantities as are reasonably necessary for the use of the report by those parties. The Client and Approved Users may not give, lend, sell, or otherwise make available the report or any portion thereof to any other party without the express written permission of Golder. The Client acknowledges that electronic media is susceptible to unauthorized modification, deterioration and incompatibility and therefore the Client can not rely upon the electronic media versions of Golder s report or other work products. The report is of a summary nature and is not intended to stand alone without reference to the instructions given to Golder by the Client, communications between Golder and the Client, and to any other reports prepared by Golder for the Client relative to the specific site described in the report. In order to properly understand the suggestions, recommendations and opinions expressed in this report, reference must be made to the whole of the report. Golder can not be responsible for use of portions of the report without reference to the entire report. Unless otherwise stated, the suggestions, recommendations and opinions given in this report are intended only for the guidance of the Client in the design of the specific project. The extent and detail of investigations, including the number of test holes, necessary to determine all of the relevant conditions which may affect construction costs would normally be greater than has been carried out for design purposes. Contractors bidding on, or undertaking the work, should rely on their own investigations, as well as their own interpretations of the factual data presented in the report, as to how subsurface conditions may affect their work, including but not limited to proposed construction techniques, schedule, and safety and equipment capabilities. Soil, Rock and Groundwater Conditions: Classification and identification of soils, rocks, and geologic units have been based on commonly accepted methods employed in the practice of geotechnical engineering and related disciplines. Classification and identification of the type and condition of these materials or units involves judgment, and boundaries between different soil, rock or geologic types or units may be transitional rather than abrupt. Accordingly, Golder does not warrant or guarantee the exactness of the descriptions.

7 Special risks occur whenever engineering or related disciplines are applied to identify subsurface conditions and even a comprehensive investigation, sampling and testing program may fail to detect all or certain subsurface conditions. The environmental, geologic, geotechnical, geochemical and hydrogeologic conditions that Golder interprets to exist between and beyond sampling points may differ from those that actually exist. In addition to soil variability, fill of variable physical and chemical composition can be present over portions of the site or on adjacent properties. The professional services retained for this project include only the geotechnical aspects of the subsurface conditions at the site, unless otherwise specifically stated and identified in the report. The presence or implication(s) of possible surface and/or subsurface contamination resulting from previous activities or uses of the site and/or resulting from the introduction onto the site of materials from off-site sources are outside the terms of reference for this project and have not been investigated or addressed. Soil and groundwater conditions shown in the factual data and described in the report are the observed conditions at the time of their determination or measurement. Unless otherwise noted, those conditions form the basis of the recommendations in the report. Groundwater conditions may vary between and beyond reported locations and can be affected by annual, seasonal and meteorological conditions. The condition of the soil, rock and groundwater may be significantly altered by construction activities (traffic, excavation, groundwater level lowering, pile driving, blasting, etc.) on the site or on adjacent sites. Excavation may expose the soils to changes due to wetting, drying or frost. Unless otherwise indicated the soil must be protected from these changes during construction. Sample Disposal: Golder will dispose of all uncontaminated soil and/or rock samples 90 days following issue of this report or, upon written request of the Client, will store uncontaminated samples and materials at the Client s expense. In the event that actual contaminated soils, fills or groundwater are encountered or are inferred to be present, all contaminated samples shall remain the property and responsibility of the Client for proper disposal. Follow-Up and Construction Services: All details of the design were not known at the time of submission of Golder s report. Golder should be retained to review the final design, project plans and documents prior to construction, to confirm that they are consistent with the intent of Golder s report. During construction, Golder should be retained to perform sufficient and timely observations of encountered conditions to confirm and document that the subsurface conditions do not materially differ from those interpreted conditions considered in the preparation of Golder s report and to confirm and document that construction activities do not adversely affect the suggestions, recommendations and opinions contained in Golder s report. Adequate field review, observation and testing during construction are necessary for Golder to be able to provide letters of assurance, in accordance with the requirements of many regulatory authorities. In cases where this recommendation is not followed, Golder s responsibility is limited to interpreting accurately the information encountered at the borehole locations, at the time of their initial determination or measurement during the preparation of the Report. Changed Conditions and Drainage: Where conditions encountered at the site differ significantly from those anticipated in this report, either due to natural variability of subsurface conditions or construction activities, it is a condition of this report that Golder be notified of any changes and be provided with an opportunity to review or revise the recommendations within this report. Recognition of changed soil and rock conditions requires experience and it is recommended that Golder be employed to visit the site with sufficient frequency to detect if conditions have changed significantly. Drainage of subsurface water is commonly required either for temporary or permanent installations for the project. Improper design or construction of drainage or dewatering can have serious consequences. Golder takes no responsibility for the effects of drainage unless specifically involved in the detailed design and construction monitoring of the system.