slide name: (gp 1) hwy 40:42 wapiti hill inspection …...0104-00-22537.002 - 3 - december 2002...

0104-00-22537.002 - 3 - December 2002 Dec2002SlideTourRpt.doc Slide Name: (GP 1) Hwy 40:42 Wapiti Hill Inspection Date: June 5, 2002 Inspection By: Alberta Transportation Staff (see attached list of attendees) EBA Staff (Karl Li and Tony Ruban) 1.0 BACKGROUND Refer to EBA 2001 and earlier reports for site conditions and details of risk assessment. The current instrumentation data and details of data interpretation are provided in the Spring 2002 Instrumentation Monitoring Report. 2.0 OBSERVATIONS • The previous and current (May 2002) SI readings were reviewed to indicate that: • At SI #11 and #12, movement rates of approximately 100 mm/2.5 year are occurring at the top portion of this slide at a 21 m depth. The backscarp crack has retrogressed to the toe area of the backslope (SI#3) with minor shear movements monitored at 3 m depth. • Movements at 22 to 23 m depth (SI #12 at centre portion of slide) and at 7 m depth (SI #13 at east edge of the slide) were recorded. • At SI #11 and #12, movement rates of approximately 100 mm/2.5 year and 50 mm/1.5 year were recorded at the centre of the slide. • At SI #13, movement rate of approximately 110 mm/3 year at edge of slide. • Movement rate is classified as slow to moderate. • SI#11 was sheared off in June 2001 and SI#12 was vandalized (possibly sheared off). • MCI informed that patching was carried out at (approximate) yearly basis. Minimal change to pavement settlement and cracking repair. • The depths of movements (22 to 23 m) were discussed as very difficult to stabilize. • The adjacent 40 m stretch of highway settlement (approximately 75 m distance north and downgrade from the slide) has started to show signs of deterioration. No instrumentation has been installed at this distress area. • It was discussed more practical to shift the alignment towards the backslope realizing that an overpass at Weyerhaeuser Access Road may be a geometric constraint for realignment. • To date, all the instrumentations have been installed at the upper portion and middle of this slide. • Additional installation instrumentation was previously recommended for the lower portion of sideslope to define the movement of this slide. • This option of additional instrumentation is still valid and will require access clearing. 2.1 Site Discussions (June 2002) • In the June 2002 inspection, it was discussed and prioritized (with AT) to instrument and monitor the new distress portion of roadway. The investigation of realigning the highway (towards the backslope) was considered a priority by AT.

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0104-00-22537.002 - 3 - December 2002

Dec2002SlideTourRpt.doc

Slide Name: (GP 1) Hwy 40:42 Wapiti HillInspection Date: June 5, 2002Inspection By: Alberta Transportation Staff (see attached list of attendees)

EBA Staff (Karl Li and Tony Ruban)

1.0 BACKGROUNDRefer to EBA 2001 and earlier reports for site conditions and details of risk assessment.The current instrumentation data and details of data interpretation are provided in theSpring 2002 Instrumentation Monitoring Report.

2.0 OBSERVATIONS• The previous and current (May 2002) SI readings were reviewed to indicate that:

• At SI #11 and #12, movement rates of approximately 100 mm/2.5 year areoccurring at the top portion of this slide at a 21 m depth. The backscarp crackhas retrogressed to the toe area of the backslope (SI#3) with minor shearmovements monitored at 3 m depth.

• Movements at 22 to 23 m depth (SI #12 at centre portion of slide) and at 7 mdepth (SI #13 at east edge of the slide) were recorded.

• At SI #11 and #12, movement rates of approximately 100 mm/2.5 year and50 mm/1.5 year were recorded at the centre of the slide.

• At SI #13, movement rate of approximately 110 mm/3 year at edge of slide.• Movement rate is classified as slow to moderate.• SI#11 was sheared off in June 2001 and SI#12 was vandalized (possibly

sheared off).• MCI informed that patching was carried out at (approximate) yearly basis.

Minimal change to pavement settlement and cracking repair.• The depths of movements (22 to 23 m) were discussed as very difficult to stabilize.• The adjacent 40 m stretch of highway settlement (approximately 75 m distance

north and downgrade from the slide) has started to show signs of deterioration. Noinstrumentation has been installed at this distress area.

• It was discussed more practical to shift the alignment towards the backsloperealizing that an overpass at Weyerhaeuser Access Road may be a geometricconstraint for realignment.

• To date, all the instrumentations have been installed at the upper portion and middleof this slide.

• Additional installation instrumentation was previously recommended for the lowerportion of sideslope to define the movement of this slide.

• This option of additional instrumentation is still valid and will require accessclearing.

2.1 Site Discussions (June 2002)• In the June 2002 inspection, it was discussed and prioritized (with AT) to

instrument and monitor the new distress portion of roadway. The investigation ofrealigning the highway (towards the backslope) was considered a priority by AT.

0104-00-22537.002 - 4 - December 2002

Dec2002SlideTourRpt.doc

3.0 RISK ASSESSMENTPF (9) and CF (4) = 36Risk rating has not changed from that assessed in 2001 Inspection Report. Any currentadditional comments are provided in the 2002 Spring Instrumentation MonitoringReport.

Note:The Risk Assessment rating is based on scheme proposed by AT in 2000.

Probability Factor (PF):Consequence Factor (CF):

1 to 20 scale1 to 20 scale

4.0 ACTION• It was decided to further monitor this slide with additional instrumentation and

investigate the realignment option.• EBA will submit proposal (i) on additional instrumentation for the existing slide

area, (ii) new instrumentation for the adjacent settlement distress area, and (iii) toinvestigate the realignment design to shift the roadway from the slide area.