CENTRAL REGION GEOHAZARDS RISK ASSESSMENT SITE INSPECTION FORM

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1 SITE NUMBER AND NAME C55 H861:02 Slide LEGAL DESCRIPTION NW W4 CENTRAL REGION GEOHAZARDS RISK ASSESSMENT SITE INSPECTION FORM HIGHWAY & KM NAD 83 COORDINATES N E PREVIOUS INSPECTION DATE INSPECTION DATE June 19, 2012 May 15, 2013 RISK ASSESMENT PF: 9 CF: 4 TOTAL: 36 SUMMARY OF SITE INSTRUMENTATION: INSPECTED BY: None LAST READING DATE: PRIMARY SITE ISSUE: Embankment Slide APPROIMATE DIMENSIONS: 15 m to 20 m wide DATE OF ANY REMEDIAL ACTION: None ITEM Pavement / Road Surface Distress CONDITION EISTS DESCRIPTION AND LOCATION NOTICABLE CHANGE FROM LAST INSPECTION YES NO YES NO Cracking and a depression extended across the entire road width before the highway was re-graded with gravel fill. The guardrail has been re-located to the correct level. Slope Movement A large slide has developed along the edge of the road causing a drop in the roadway over a 15 m to 20 m length of roadway. The slope movement was initially slow moving, but was reactivated in June of 2011 due to high rainfall levels. Erosion Seepage Culvert Distress COMMENTS A site investigation program, including installation of a slope inclinometer and standpipe piezometer, is recommended to assess the zone and rate of movement before designing a repair for the site. The road is regularly topped up with gravel to preserve the driving surface, but this continues to load the top of the slide and exacerbate movement. See attached photos and previous reports.

2 September 13, 2013 Central Region #401, Street Red Deer, Alberta T4N 6K8 Mr. Dennis Grace, P.Eng. Construction Engineer Dear Mr. Grace: Slide Report The above site was inspected on May 15, 2013 by Mr. Darren Ratcliffe, P.Eng. of Klohn Crippen Berger Ltd. (KCB). A drilling investigation and instrumentation installation was performed by KCB on June 21, This report was prepared by KCB for Central Region under Contract No. CON PROJECT BACKGROUND This site is located on Highway 861:02 about 1 km south of the Battle River crossing and about 7 km south of Galahad, Alberta. The slide movement is observed at the crest of a 15 m high slope and was apparent as a 600 mm drop over a 15 m to 20 m length of the gravel road in June It is understood that the age of the feature is unknown, but it was first visited by KCB in The slide was initially moving at a slow rate but was apparently re-activated in June 2011 due to the high rainfall levels in the region. The slide was likely triggered by ground saturation from the relatively high precipitation levels in recent years. Springs are also present in the area and the precipitation levels have raised the groundwater levels in the region. The soil type is consistent with the Horseshoe Canyon Formation and the slope instability is similarly consistent with failures observed in the Drumheller area. Since June 2011, the slide appears to have progressed further. However, the actual amount of displacement is difficult to determine because the road surface has been continually topped up with gravel to preserve the driving surface. It is suspected that the road surface has dropped by over 1 m on the north side. Additional cracking and slumping was also observed on the slope below the road surface R C55 H861 Investigation.docx A03038A13 Klohn Crippen Berger Ltd Hopewell Place NE Calgary AB T1Y 7J7 CANADA t f

3 2 SITE OBSERVATIONS On May 15, 2013, no slide activity was apparent within the highway as shown on Photograph 1. Since the last inspection, the guard rail had been reset to the correct height and was realigned to a position inside the previous alignment. A topographic survey was completed by Stewart, Weir & Co. Ltd. (SWG) on May 14, 2013 as shown on Figure 1. Following heavy rainfall in June 2013, the slide mobilized again, as shown in Photograph 2. The extents of the slide were essentially the same as observed in Photograph 1 Highway Condition May R C55 H861 Investigation.docx Page 2

Photograph 2 Highway Condition June 26, 2013 3 JUNE 2013 SITE INVESTIGATION 3.

4 Photograph 2 Highway Condition June 26, JUNE 2013 SITE INVESTIGATION 3.1 General A standpipe piezometer (SP13-01) was installed at the edge of the highway approximately 16 m east of the failure in the southbound lane as shown on Figure 1 on June 21, Drilling was undertaken with a truck-mounted auger rig provided by Mobile Augers and Research Ltd. (MARL) of Edmonton, Alberta. During drilling, Standard Penetration Test (SPT) and grab samples were obtained at approximately 1.5 m intervals. All samples were bagged and transported to the Stewart, Weir & Co. Ltd. (SWG) soil laboratory for testing. 3.2 Soil Stratigraphy The test hole was completed to a depth of about 15 m. The stratigraphy of the site can be generalized as follows: R C55 H861 Investigation.docx Page 3

5 0 0.9 m GRAVEL, well graded (Fill); 0.9 m 8.5 m CLAY (CI-CH), silty, trace fine sand, medium to high plasticity (liquid limit up to 60%), firm to very stiff, moist to wet (moisture contents typically 20% to 30%), grey with tan silt pockets, iron oxide staining. SPT N values increased with depth from 7 to 20 blows per 300 mm; >8.5 m SANDSTONE, fine, silty, bluish grey, dry, hard, homogenous, poorly graded (uniform), (weathered bedrock). A topsoil layer was encountered at a depth of about 3.6 m. It is unknown if this represents the original ground surface or is a topsoil layer buried in the fill. The standpipe was installed to a depth of 9.1 m with the bottom 3 m being hand slotted and backfilled with 10/20 filter sand. The standpipe was read on June 26, 2013 and the water level was 5.20 m below ground surface. The test hole log of SP13-01 is provided in Appendix I. The descriptions applied to the various soil units as shown on the logs follow the Unified Soil Classification System. Such descriptions are judgmental in nature and may differ in detail from that actually encountered in the field. The descriptions noted in the test hole logs are based solely on inspections of soil samples recovered or cuttings observed on the auger flights. The actual nature of the materials between samples may vary. 3.3 Laboratory Testing Laboratory testing was performed on selected samples by SWG in Sherwood Park, Alberta. The testing included natural moisture content and Atterberg limits. The results of the laboratory testing are provided on the test hole logs. The laboratory tests were performed following standard soil testing procedures or protocol, unless otherwise noted. The test results are to provide a general indication of some of the engineering properties of the material. 4 SITE ASSESSMENT Movements are likely occurring on a shear plane in the high plasticity clay material located at a depth of about 4 m to 5 m below the existing ground surface as shown on Figure 2. The slide is likely caused by a spring within the slope that increases the pore pressure in the low strength material during times of greater precipitation. The failure surface could also represent the interface between the original ground and the overlying fill. Based on the risk level criteria provided by relating to safety, a risk rating of 36 was assigned to this site. This is based on a probability factor of 9 for an active slide and a consequence factor of 4 due to the partial closure of the low-use road R C55 H861 Investigation.docx Page 4

6 5 RECOMMENDATIONS The addition of gravel fill in the slide area should be continued as required to reduce the hazard to traffic. Also gravel fill should be placed in the ditch area to widen the road behind the scarp. The ditch width can be reduced by minor excavation at the toe of the backslope. Gravel-filled geocell reinforcement could also be adopted in the ditch area to prevent erosion and also allow the area to be driven over. Considering the low vehicle count on this highway, moving the road into the existing ditch area is likely the most cost effective solution. Other alternatives to stabilize the slope include: 1. Driven H-pile wall H-piles driven side by side at a spacing of about 0.75 m will effectively create a wall on the south side of the highway. This approach was used at the NC33 H759:02 site using 12 m long HP310 x 110 piles in March The NC33 pile wall was installed at a horizontal distance of about 7 m from the south shoulder of the road and was about 70 m in length. It is considered that a similar remedial solution can be adopted for this site with 12 m long piles (3 times the slide depth and driven about 3 m into bedrock) and installing at a distance of about 1 m from the guardrail. This results in a line of 40 piles over the 30 m length of the slide area. Cost estimates were obtained from Red Deer Piling and indicated supply and installation costs of about $120,000 for 12 m long piles. It is recommended that the piles be installed with a 0.3 m stickup so that the top deflections of the piles may be monitored by visual or survey methods. Pros: quick fix, no need to excavate highway, single lane closure during piling with the road open at night. Cons: further gravel fill may be required as piles pick up load of slide. 2. Deep Excavation The slide is located at a depth of about 4 m to 5 m below the road and it is feasible to excavate the high plasticity clay fill and replace with compacted gravel fill to attempt to strengthen the upper portion of the slope and improve the drainage. It is estimated that about 3,000 m 3 of clay will require excavation and replacement with gravel at a cost of about $300,000. The excavated clay would be placed at the toe of the slope to increase stability. Pros: excavate below failure plane, can install drainage to reduce water pressures due to springs. Cons: deep excavation safety issues, road closed during construction R C55 H861 Investigation.docx Page 5

7 6 CLOSURE The analyses, conclusions and recommendations contained in this report are based on data derived from a limited number of test holes obtained from widely spaced subsurface explorations. The methods used indicate subsurface conditions only at the specific locations where samples were obtained or where in-situ tests would infer, only at the time they were obtained, and only to the depths penetrated. The samples and tests cannot be relied on to accurately reflect the nature and extent of strata variations that usually exist between sampling or testing locations. This report is an instrument of service of Klohn Crippen Berger Ltd. The report has been prepared for the exclusive use of for the specific application to the Highway 861:02 slide investigation. The report s contents may not be relied upon by any other party without the express written permission of KCB. In this report, KCB has endeavoured to comply with generally accepted geotechnical practice common to the local area. KCB makes no other warranty, express or implied. Yours truly, KLOHN CRIPPEN BERGER LTD. Darren W. Ratcliffe, P.Eng. Project Manager APEGA Permit to Practice No R C55 H861 Investigation.docx Page 6

1 PROJECT BACKGROUND. August 14, Alberta Transportation Central Region #401, Street Red Deer, Alberta T4N 6K8

1 PROJECT BACKGROUND. August 14, Alberta Transportation Central Region #401, Street Red Deer, Alberta T4N 6K8 August 14, 2013 Alberta Transportation Central Region #401, 4902 51 Street Red Deer, Alberta T4N 6K8 Mr. Dennis Grace, P.Eng. Construction Engineer Dear Mr. Grace: Central Region Geohazard Assessment 2013