The results of KCB s site inspection observations and our recommendations for further work are presented herein.

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Eugene Lawrence
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July 14, 2015 Central Region 401, 4902 51 Street Red Deer, Alberta T4N 6K8 Mr. Tony Penney, P.Eng. Construction Engineer Dear Mr.

1 July 14, 2015 Central Region 401, Street Red Deer, Alberta T4N 6K8 Mr. Tony Penney, P.Eng. Construction Engineer Dear Mr. Penney: June 25, 2015 Site Inspection Report The above site was visited on June 25, 2015 by Messrs. Darren Ratcliffe, P.Eng. and Chris Gräpel, P.Eng. of Klohn Crippen Berger (KCB) in the company of Messrs. Rocky Wang, P.Eng. and Tony Penney, P.Eng. of (AT). The site visit was conducted during the spring 2015 tour of the Central Region Geohazard Risk Management Program (GRMP). The site was previously visited on a Call-Out inspection on April 14, 2015 by Mr. Darren Ratcliffe, P.Eng. of KCB. Photographs from the inspections are included in Appendix I. This report was prepared by KCB for AT under Contract No. CON The results of KCB s site inspection observations and our recommendations for further work are presented herein. 1 PROJECT LOCATION The site is located on Highway 585:02 (km 18) about 2 km west of the Red Deer River crossing (Tolman) and about 13 km east of Trochu. The highway at this location is descending into the valley towards the Red Deer River. The 2013 Annual Average Daily Traffic (AADT) for H585 was 490. The site location is shown on Figures 1 and L H inspection.docx A03038A15 Klohn Crippen Berger Ltd Hopewell Place NE Calgary AB T1Y 7J7 CANADA t f

2 Figure 1 Location Plan Slide Area Page 2

3 Figure 2 Site Plan Culvert Slide Area Culvert Page 3

4 2 SITE OBSERVATIONS Observations made during the June 25, 2015 site inspection are briefly summarized as follows: The slide movement is observed at the crest of 3H:1V (approx.) fill slope about 2 m to 3 m high and is apparent as a 20 m long section of pavement with severe distress (see Photograph 1). The semi-circular crack is about 9 m long. The road width at this location is about 7.5 m and the maximum extent of the crack into the road is about 3 m. The crack has a maximum vertical displacement of about 100 mm near the guardrail. Photos 1 and 2 show the difference in pavement deformation between the June 2015 and the April 2015 site visits. Westbound traffic (travelling uphill), including tractor-trailers, were changing lanes over the double centreline to avoid the pavement roughness at this site. There is limited sight distance in a westbound direction due to curvature of the highway as shown in Photos 3 and 4. Bulging of the slope to the north of the highway was not observed; however, the guardrail posts are tipped over at the ground surface perpendicular to the edge of pavement as shown in Photo 3. Furthermore, the guardrails are also tipped in a westerly direction near the area of greatest pavement distress and thickness as shown in Photo 5. This suggests that shallow, surficial lateral spreading with associated settlement is occurring, possibly due to an underlying weak and/or saturated layer. The highway has been repeatedly patched at this location with asphalt at least 1 m thick observed at the edge. The guardrail is almost level with the highway surface which indicates that deformation at this site has been underway for several years. Vegetation is present on both sides of the highway at this location indicative of shallow groundwater conditions. An increase in vegetation density, including willows, were observed downslope of the area of most severe pavement distress as shown in Photo 5. Erosion channels associated with seepage were observed downslope of the willows as shown in Photos 6 and 7 which indicates that seepage is discharging further downslope with enough velocity to cause erosion. It is considered possible that the highway was constructed over a narrow valley or buried channel trending to the northeast at the observed area of pavement distress. The highway over a length of about 1 km to the west of the slide site contains numerous patches and evidence of previous zones of pavement distress. Steep slopes on the north side of the highway are also apparent. No areas of pavement distress were observed to the east of the subject site L H inspection.docx Page 4

5 3 SITE ASSESSMENT The subject area is limited in extent with a gently sloping, relatively low height fill slope below. The area of distress is considered to be slow moving (creep movement) and likely represents a shallow lateral spreading. The subgrade at this location (and at other locations to the west) is likely weakened by high groundwater associated with subsurface flow to the north/northeast towards the nearby ravine. The observed erosion gully caused by seepage indicates that groundwater flows can be substantial during periods of elevated groundwater. Based on KCB s observations in April and June of 2015, it seems reasonable to conclude that either a natural valley was in-filled during the original construction of the highway or that a spring was buried without adequate drainage measures being installed. Groundwater levels should be expected to vary seasonally. AT should monitor the site for evidence that rates of movement are dependent on periods of high runoff caused by snowmelt freshet or sustained periods of rainy weather. 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 settlement zone, and a consequence factor of 4 due to the impact to vehicles travelling on the highway. 4 RECOMMENDATIONS It is recommended that the pavement distress can be managed in the short term with the provision of pavement milling, patching, and resetting the guardrail to the correct height to reduce the hazard to traffic and reduce the frequency of westbound traffic crossing into the east bound lane. A long term remedial approach would be to establish subsurface drainage to lower the groundwater table and replace weak materials beneath the pavement. This would start with removal of the thick layer of asphalt placed at this location. The embankment fill should then be excavated to a depth of about 1.5 m to 2.0 m and replaced with compacted gravel fill that includes filter fabric wrapped perforated drains that extend from the eastbound lane ditch to the erosion gully described earlier. Drains should typically comprise 150 mm diameter perforated HDPE pipes at about 3 m centres which can be joined to a common discharge point draining to the erosion gully. The excavation below the highway should be conducted to below the groundwater table, if possible, to increase the effectiveness of the drains. Depending on the depth and lateral extent of the excavation as well as the condition of the excavation subgrade, geo-grid reinforcement and a basal separation layer of nonwoven geotextile can be placed to further strengthen the subgrade. The intent is to lower the groundwater table, protect the drains from being eventually clogged with silt and replace weak material with coarse granular materials. The excavation may also expose a weak layer under the road that can be removed and replaced with a gravel shear key. The outlet from the drain pipe should be protected with armouring such as perforated geo-cell backfilled with coarse gravel to prevent the erosion gully from enlarging due to concentration of groundwater discharge L H inspection.docx Page 5

6 5 CLOSURE 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 Central Region Geohazard Assessments. The report's contents may not be relied upon by any other party without the express written permission of Klohn Crippen Berger. In this report, Klohn Crippen Berger has endeavoured to comply with generally-accepted professional practice common to the local area. Klohn Crippen Berger makes no warranty, express or implied. Please contact the undersigned if you have any questions regarding this report. Yours truly, KLOHN CRIPPEN BERGER LTD. Chris Gräpel, P.Eng. Senior Civil Engineer APEGA Permit to Practice No Attachments Photographs L H inspection.docx Page 6

7 APPENDIX I Photographs L H inspection.docx

Site Photograph Photograph 1 Pavement distress on June 25, 2015.

14, 2015 from same perspective as Photograph 1.

8 Site Photograph Photograph 1 Pavement distress on June 25, Photograph taken facing east Photograph 2 Pavement distress on April 14, 2015 from same perspective as Photograph 1. Note that Photograph 1 shows additional movement and pavement distress Site Photographs Page 1

9 Site Photograph Photograph 3 Pavement distress and limited sight distance to the west. Note that the guardrails have been tipped by ongoing deformation at this site. Photograph taken facing west. Photograph 4 Condition of pavement and limited sight distance to the west. Photograph taken facing southwest Site Photographs Page 2

Note density of willows downslope of guardrail. Photograph taken facing south.

10 Site Photograph Photograph 5 Inclination of guardrails in a westerly direction. Red arrow and highway markers indicate area of most severe pavement distress at this site. Note density of willows downslope of guardrail. Photograph taken facing south. Photograph 6 Start of erosion gully which appears to be due to groundwater discharge on the slope below the highway. Red arrow shows approximate location of most severe pavement distress. Photograph taken facing south west Site Photographs Page 3

11 Site Photograph Photograph 7 Erosion gully downslope of pavement distress and Photograph 6 location. Photograph taken facing north east Site Photographs Page 4

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