THURBER ENGINEERING LTD. G E O T E C H N I C A L E N V I R O N M E - - PDF document

Client: Alberta Transportation Date: August 2, 2011 File No.: 15-16-264 Page 1 of 2 E File: H:\15\16-264 PH Geohazard Assessments - 2011 - Edmonton Office\Callouts\PH12 Judah Hill Heart Valley Slides, Aug 2, 2011\PH12 Heart R 2011.docx

ALBERTA TRANSPORTATION GEOHAZARD ASSESSMENT PROGRAM PEACE REGION – PEACE-HIGH LEVEL 2011 CALLOUT (AUGUST 02) 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 Previous Inspection: 25-May-2011 12 2 24 Current Inspection: 2-Aug.-2011 13 3 39 Road AADT: 570 Year: 2010 Inspected By: Roger Skirrow Don Proudfoot Erwin Kurz Report Attachments: Photographs Plans Maintenance Items Primary Site Issue: On July 25, 2011, a heavy rain storm caused the slides to regress resulting in a 5 m by 2.9 m section of pavement from the brake check lane falling into the slide bowl at the Slide 2 site. Additional backscarp movement was observed on July 31, 2011 Dimensions: Slide 1: 45 m wide Slide 2: 30 m wide, backscarp is 2.2 m past guardrail Slide 3: 30 m wide, backscarp is 2.8 m from guardrail Slide 4: 30 m wide, backscarp is 0.9 m from guardrail Maintenance: No maintenance activity since 2009. Observations: Description Worsened? Pavement Distress

Slide 2 has now encroached 2.9 m into the brake check lane pavement, with a 10 m long section lost along guardrail with undermining and surface cracking along additional 4 m long sections immediately to the north and south.

Slope Movement

Continuing movement, retrogression and expansion of the slide bowls at Slides 2, 3 and

• 4. Backscarp of slide 2 has retrogressed

nearly 2.2 m since May 25, 2011 and 5 guardrail posts are now hanging and the curve ahead roadway sign has fallen over into slide (Photos 3 and 4). Backscarp of Slide 3 retrogressed by about 2 m, and flank is now

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G E O T E C H N I C A L E N V I R O N M E N TA L M AT E R I A L S P P

Client: Alberta Transportation Date: August 2, 2011 File No.: 15-16-264 Page 2 of 2 E File: H:\15\16-264 PH Geohazard Assessments - 2011 - Edmonton Office\Callouts\PH12 Judah Hill Heart Valley Slides, Aug 2, 2011\PH12 Heart R 2011.docx

• nly 8 m north of Slide 4 (Photos 5 and 6).

Backscarp

• f

slide 4 has noticeably retrogressed to 0.9 m from edge of pavement, with visible fresh ravelling and a harder layer now visible at the base of the slide bowl. (Photos 7 and 8).

Erosion Seepage Bridge/Culvert Distress Other Instrumentation: No instrumentation installed at this site. Assessment: Heavy rainfall from a flash storm on July 25, 2011 had saturated the slid emass and accelerated the retrogression of the backscarps of Slides 2, 3 and 4. Additional movement was observed on July 31, 2011. Recommendations: Cost Short Term: Inspect the slides regularly (particularly after heavy and/or prolonged rain, rapid snowmelt). Shift the guardrail west of the current slide scarp to close off the brake check lane, in order to avoid exposing the public to a hazard. Post a warning sign “Steep Slopes” and/or “Landslide Hazard”. Maintenance Longer Term: Repair slides 2, 3 and 4 using similar method as slide 1 (drain to the toe of the slope, reinforce with gravel fill reinforced with geogrid to buttress backscarp). Alternate stabilization methods could include a pile wall, micro-pile supported retaining wall and smaller gravel buttress. $ 450,000 (all 3 slides) or higher for alternates

THURBER ENGINEERING LTD.

Client: Alberta Transportation Date: August 2, 2011 File No.: 15-16-264 Page 1 of 4 E File: H:\15\16-264 PH Geohazard Assessments - 2011 - Edmonton Office\Callouts\PH12 Judah Hill Heart Valley Slides, Aug 2, 2011\PH12 Heart River Aug 2, 2011 Callout Photos.doc

Photo 1. Looking south along Hwy 744 from the south end of Slide 1. Photo 2. Little change in the backscarp of Slide 1 since May 25, 2010 – the repair continues to be effective. Some evidence of pit run are visible in slope

THURBER ENGINEERING LTD.

Client: Alberta Transportation Date: August 2, 2011 File No.: 15-16-264 Page 2 of 4 E File: H:\15\16-264 PH Geohazard Assessments - 2011 - Edmonton Office\Callouts\PH12 Judah Hill Heart Valley Slides, Aug 2, 2011\PH12 Heart River Aug 2, 2011 Callout Photos.doc

Photo 3. Significant additional movement in the backscarp of Slide 2. The backscarp is now extending as far as 2.9 m past guardrail into pavement, five guardrail posts are now hanging and curve ahead sign has fall over – Photo 4. Slide bowl of Slide 2 – significant additional debris has been added.

THURBER ENGINEERING LTD.

Client: Alberta Transportation Date: August 2, 2011 File No.: 15-16-264 Page 3 of 4 E File: H:\15\16-264 PH Geohazard Assessments - 2011 - Edmonton Office\Callouts\PH12 Judah Hill Heart Valley Slides, Aug 2, 2011\PH12 Heart River Aug 2, 2011 Callout Photos.doc

Photo 5. North side of Slide 3. Backscarp has retrogressed by 2 m to 2.8 m from the edge of pavement since May 25, 2010. Photo 6. Significant movement

• n the south flank of

the backscarp of Slide 3, with now only 8 m left along bush line south to Slide 4.

THURBER ENGINEERING LTD.

Client: Alberta Transportation Date: August 2, 2011 File No.: 15-16-264 Page 4 of 4 E File: H:\15\16-264 PH Geohazard Assessments - 2011 - Edmonton Office\Callouts\PH12 Judah Hill Heart Valley Slides, Aug 2, 2011\PH12 Heart River Aug 2, 2011 Callout Photos.doc

Photo 7. Looking northwards across the backscarp

• f Slide 4. There has

been slight retrogression since May 25, 2011 and some ravelling. Photo 8. Looking downslope at additional debris surface flow from Slide 4, harder layer now noticeable at base of bowl.

THURBER ENGINEERING LTD.