ALBERTA TRANSPORTATION GEOHAZARD ASSESSMENT PROGRAM PEACE REGION - PDF document

ALBERTA TRANSPORTATION GEOHAZARD ASSESSMENT PROGRAM PEACE REGION – PEACE-HIGH LEVEL 2009 INSPECTION Site Number Location Name Hwy km PH12 Judah Hill Heart River Slides 744:04 57.30 Legal Description UTM Co-ordinates SE¼ 20-083-21 W5M 11V E 483284 N 6229209 Date PF CF Total 02-Jun-2008 9 2 18 Previous Inspection: Current Inspection: 26-May-2009 10 2 20 Road AADT: 2250 Year: 2007 Simon Cullum-Kenyon Don Proudfoot Inspected By: Roger Skirrow Ed Szmata Neil Kjelland Photographs Report Attachments: Plans Maintenance Items Primary Site Issue: Four slides on the east side of Hwy 744, adjacent to a layby. Slide 1 was repaired in March 1998. Slides 2 and 4 are most active, with backscarps now 2.4 m and 3.3 m from the guardrail, respectively. Dimensions: Slide 1: 45 m wide Slide 2: 25 m wide, backscarp is 2.4 m from guardrail Slide 3: 20 m wide, backscarp is 6.5 m from guardrail Slide 4: 15 m wide, backscarp is 3.3 m from guardrail No maintenance activity since 2008. Maintenance: Observations: Description Worsened? Pavement Distress Backscarps of Slide 2 (Photos 3 and 4) and Slide 4 (Photo 6) have retrogressed. There is erosion on the south flank of Slide 2, caused by drainage from the ditch. The vertical offset on Slope Movement the incipient scarp between Slides 2 and 3 has increased (Photo 3). There has been significant movement of debris in the bowl of Slide 4 (Photo 7). PF increased to 10 from 9 to reflect retrogression of slides. Erosion Seepage Client: Alberta Transportation Date: November 10, 2009 File No.: 15-16-229 Page 1 of 2 E File: \\tefsts01\PROJECTS\15\16\PH Geohazard Assessments\PH12 Heart River\Part B Assessments\2009\PH12 Heart R 2009.doc

Bridge/Culvert Distress Other Instrumentation: No instrumentation installed at this site. Assessment: Surface water drainage in the ditch appears to be driving retrogression of the slides that have not been repaired. The repairs at slide 1 continue to perform well. Slides 2, 3 and 4 are expected to continue to expand laterally and retrogress back towards the road. The incipient failure between slides 2 and 3 (Photo 3) is expected to cause these slides to coalesce in the future. Slide 4 appears to be most active over the last few years, though slide 2 has also shown significant movement. All the slides are sufficiently far away from the active road lanes that there are no immediate concerns. Recommendations: Cost Repair slides 2 and 4 using similar method as slide 1 (drain to the $ 220,000 or toe of the slope, gravel fill buttress). Alternate stabilisation methods higher for could include a pile wall, micro-pile supported retaining wall and alternates smaller gravel buttress. Install French drain along ditch to capture drainage and direct it down slope in a controlled manner (to prevent further slide $ 45,000 retrogression). Client: Alberta Transportation Date: November 10, 2009 File No.: 15-16-229 Page 2 of 2 E File: \\tefsts01\PROJECTS\15\16\PH Geohazard Assessments\PH12 Heart River\Part B Assessments\2009\PH12 Heart R 2009.doc

Photo 1. Slide 1 at the north end of the site. No fresh slide movement. Photo 2. Looking down slope (eastwards) at Slide 1. No significant changes since 2007. Note the water in the sag pond above the Heart River. Client: Alberta Transportation Date: November 10, 2009 File No.: 15-16-229 Page 1 of 4 E File: \\tefsts01\PROJECTS\15\16\PH Geohazard Assessments\PH12 Heart River\Part B Assessments\2009\PH12 Heart R PHOTOS 2009.doc

Photo 3. Looking south along the backscarp of Slide 2. There is fresh movement in the backscarp, and erosion due to water draining from the ditch. The vertical offset at the indistinct backscarp south of this slide (arrow) appears to have increased. Photo 4. North end of Slide 2. There may be some fresh movement at this end of the slide, though there is some grass take on the debris at this end of the slide bowl. Client: Alberta Transportation Date: November 10, 2009 File No.: 15-16-229 Page 2 of 4 E File: \\tefsts01\PROJECTS\15\16\PH Geohazard Assessments\PH12 Heart River\Part B Assessments\2009\PH12 Heart R PHOTOS 2009.doc

Photo 5. Looking southwards across the backscarp of Slide 3. No fresh movement. Photo 6. Further significant slide movement in the backscarp of Slide 4. Note the bands of wet soil in the backscarp. Client: Alberta Transportation Date: November 10, 2009 File No.: 15-16-229 Page 3 of 4 E File: \\tefsts01\PROJECTS\15\16\PH Geohazard Assessments\PH12 Heart River\Part B Assessments\2009\PH12 Heart R PHOTOS 2009.doc

Photo 7. Slide runout for Slide 4. Note the steep, high flanks of the slide bowl. Client: Alberta Transportation Date: November 10, 2009 File No.: 15-16-229 Page 4 of 4 E File: \\tefsts01\PROJECTS\15\16\PH Geohazard Assessments\PH12 Heart River\Part B Assessments\2009\PH12 Heart R PHOTOS 2009.doc