North Central Region – Edson Area Call-Out on Hwy 47:06 ... · Golder Associates: Operations in Africa, Asia, Australasia, Europe, North America and South America ... Highway 47

Golder Associates Ltd.

16820 107 Avenue, Edmonton, Alberta, Canada T5P 4C3

Tel: +1 (780) 483 3499 Fax: +1 (780) 483 1574 www.golder.com Golder Associates: Operations in Africa, Asia, Australasia, Europe, North America and South America

Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation.

North Central Region – Edson Area Call-Out on Hwy 47:06, km 39.6

2.2 km North of Fickle Lake Road Dear Mr. Hawley

This report details the results of the call-out undertaken at the above noted site located at km 39.6 of Highway 47:06. The call-out was conducted by Mr. Ian Darrach, P. Eng. and Mr. Eric Leishman, EIT of Golder Associates Ltd. on August 1, 2012 in conjunction with the annual geohazard site inspections. Also present onsite during the call-out were Mr. Roger Skirrow, P. Eng., Mr. Jon Lee, EIT, and Mr. Howard Hawley, all of Alberta Transportation (AT). This letter is an update to one dated October 15, 2012, and supersedes that document.

1.0 BACKGROUND Highway 47 is a paved, undivided two lane highway at this location. The legal land description of the site is SE24-51-19-W4M. The site is located at a bend in the road where the alignment changes from southwest-northeast to north-south. The highway traverses a forested area, with several oil and gas plants nearby. The Embarras River joins the Erith River south of the site, and is located to the east of the highway and continues parallel to the highway until it reaches the McLeod River, approximately 6 km north. At the site, the highway crosses a tributary to the Embarras River. There is a 1200 mm culvert at this crossing, as well as a 760 mm overflow culvert 10 m to the south. 20 m further south is a 400 mm downdrain. The plan and profile from the original construction of the highway in this area is attached for reference.

The first signs of pavement distress at this site comprised of an arched crack and dip in the north bound lane. The upstream and downstream sloped ends of the existing 1200 mm culvert had also separated. Following the separation, it is understood that the upstream channel silted in and vegetated to the elevation of the 760 mm overflow culvert. As a result, all flow was being directed through this overflow culvert, except when flow capacity was high enough to overtop the 760 mm culvert. When this happened, surface water would be directed to the 1200 mm culvert.

Recent work done at this site included the reattachment of the sloped ends of the 1200 mm culvert, with a strut installed approximately 10 m from the downstream end. Struts were installed in several culverts in this area to prevent collapse as a result of improper culvert installation when grading work was done initially in the 1970’s. Asphalt patching was conducted in 2011, and a slight dip in the surface of the pavement was noted subsequent to this patching. Prior to this, it is understood that the embankment slopes had been stable since it was first

January 23, 2013 12-1376-0017

Howard Hawley Alberta Transportation 2nd Floor, Provincial Building 111-54 Street Edson, AB, T7E 1T2

Howard Hawley 12-1376-0017 Alberta Transportation January 23, 2013

2/4

paved in 1971. Shortly after the call-out was conducted, Golder was informed that the area had been patched with approximately 29 tonnes of ACP.

A copy of the plan/profile figure from 1970 is attached. Stick logs show a layer of topsoil overlying a medium to high plastic silty clay. The native clay was encountered to be very wet of optimum in the area of the embankment as well as in the adjacent borrow area.

Golder understands that this site has not previously been viewed by geotechnical personnel in relation to the Geohazard Assessment program. Therefore, the site visit on August 1, 2012 is the first on record.

2.0 OBSERVATIONS During the site visit, the highway surface, embankment side slopes and 1200 mm culvert inlet and outlet were inspected. Select photographs from the inspection are attached at the end of this letter. Figure 1 shows the location of observations made during the site visit.

The overall height of the embankment is in the order of 10 to 12 m. The east embankment slope was found to have a grade of approximately 3H:1V, steepening at the culvert outlet. The ground surface surrounding the outlet was found to be generally bare of vegetation, likely from the recent reinstallation. As seen in Photo 1, the 1200 mm culvert was observed to be operating just below ¼ capacity, however, saturated ground was observed along the downstream banks of the channel to approximately the halfway point of the culvert. This is either a potential high water mark from runoff from recent rainfall or due to groundwater seepage. Also noted in the banks of the downstream channel near the outlet were small erosion gullies.

The west side of the embankment was also observed to have an overall slope of 3H:1V; however, this slope was benched at two levels, corresponding approximately to the 1/3 points of the slope. Similar to the outlet, the inlet was observed to lack established vegetation in the area immediately surrounding the culvert, shown in Photo 2. Saturated ground was also observed along the channel banks at the inlet to approximately 400 mm above the current water level. Small cracks were noted in the ground adjacent to the inlet; however, these were likely caused by fill settlement from the culvert end installation.

Although no toe bulges or tension cracks were noted in the embankment at the time of the call-out, some signs of instability were observed along the surface of the highway. A 40 m long depression in the northbound lanes of the highway was noted, as indicated on Figure 1, although no toe bulge was apparent downslope. The overall settlement of this section appears to be in the order of 200 to 300 mm, with higher degrees of settlement along the outside shoulder due to the superelevation of the road through the curve. The settlement is evident in Photo 3 when comparing the embedment depths of the guardrail posts and the dip in the road.

The guardrails on the west side of the highway were observed to be leaning slightly to the west, shown in Photo 4, although this may not be attributed to instability of the embankment. There are no surface cracks in the pavement indicating a slope failure in this direction, nor are there any toe bulges, scarps or tension cracks observed within the west slope.

3.0 ASSESSMENT No obvious cause of the settlement of east side of the pavement has been determined based on the limited available information.

One potential mechanism for the observed settlement of the pavement could have been wetting induced settlement of the cohesive clay fill material triggered by the silting in of the 1200 mm diameter culvert. The silting in of the culvert could have led to saturation of the granular envelope around the pipe which then could have


3/4

caused saturation of the clay fill at the downstream end of the pipe. If water entered the gravel envelope, it would be expected to flow down the slope of the CSP and then be blocked by the downstream clay seal. Clay fills can sit stable for many decades, but soften and collapse with wetting. Dry fills have more potential for collapse, and more poorly compacted fills have potential for more settlement with wetting. The zone of influence of this wetting would depend on the level of water in the granular backfill and the slope of the pipe. It is possible that the surface expression of the settlement at the top of the fill could be as wide as noted on the east side of the pavement.

With no toe bulge evident on the slope, there is presently no signs that this is a circular failure within the fill or down into the foundation clays.

4.0 RISK LEVEL The risk level at this site, based on AT’s risk level system, has presently been determined to be:

PF(6) x CF(6) = 36

A Probability Factor of 6 was chosen to reflect that the slope had been stable prior to the initial patch, and that the rate of movement is apparently very slow with an indeterminate movement pattern. The rate however, could increase with surcharges from additional patching.

A Consequence Factor of 6 was chosen since continued movement will result in further distress at the site. A slide would also have a direct adverse affect on the culvert and the flow of the Embarras River tributary. A full or partial closure of the highway would be required if the rate of movement accelerated and the backscarp began to propagate through the pavement. Construction of a detour would be a major undertaking due to the heavily forested nature of the area and the depth of the tributary valley.

5.0 RECOMMENDATIONS Short term mitigation should include regular inspections by the MCI to monitor the condition of the site. Maintenance to the pavement surface should be conducted to ensure a satisfactory ride quality, including either maintaining the superelevation across the highway through patching or decreasing the speed limit at this location. Any surface cracks in the pavement should be sealed to decrease the amount of water infiltrating into the embankment.

If wetting collapse of poorly compacted fill is the actual mechanism of movement, all that may be required is asphalt patching to the pavement surface as the settlement should decrease over time. However, if a different mechanism is found to be occurring, a geotechnical investigation with instrumentation installation should be considered. Instrumentation to be installed at the site should include slope inclinometers and piezometers to monitor movements in the slope and pore pressures. Prior to the investigation, some access preparation would be required. The guardrails would need to be removed and drilling platforms would be required on the east side of the highway through minor cut and fill for drill rig access.

If a mechanism other than wetting collapse is found to be occurring, as determined through geotechnical investigation or other observations, long term remedial measures may include flattening the side slopes with the construction of toe berms (with or without a shear key). Drains could also be considered with the construction of the toe berm in order to improve drainage within the embankment and increase stability.


4/4

6.0 CLOSURE We trust that the information presented in this report meets your present requirements. Should you require any additional information, or further clarification regarding any of the above, please do not hesitate to contact the undersigned.

Respectfully Submitted

GOLDER ASSOCIATES LTD.

Eric Leishman, EIT Ian Darrach, M.Eng., P.Eng. Geotechnical Engineer-in-Training Senior Geotechnical Engineer EML/IDD/sw Attachments: 1. Select Photographs 2. Site Plan 3. Plan and Profile, 1971 \\golder.gds\gal\edmonton\active\2012\1376 geotech 2012\projects\12-1376-0017 - at - edson slope services\7. geohazard sites\hwy 47;06 km 39.6\part d - call outs\2012 47;06 call-out report.docx


Special risks occur whenever engineering or related disciplines are applied to identify subsurface conditions and even a comprehensive investigation, sampling and testing program may fail to detect all or certain subsurface conditions. The environmental, geologic, geotechnical, geochemical and hydrogeologic conditions that Golder interprets to exist between and beyond sampling points may differ from those that actually exist. In addition to soil variability, fill of variable physical and chemical composition can be present over portions of the site or on adjacent properties. The professional services retained for this project include only the geotechnical aspects of the subsurface conditions at the site, unless otherwise specifically stated and identified in the report. The presence or implication(s) of possible surface and/or subsurface contamination resulting from previous activities or uses of the site and/or resulting from the introduction onto the site of materials from off-site sources are outside the terms of reference for this project and have not been investigated or addressed.

Soil and groundwater conditions shown in the factual data and described in the report are the observed conditions at the time of their determination or measurement. Unless otherwise noted, those conditions form the basis of the recommendations in the report. Groundwater conditions may vary between and beyond reported locations and can be affected by annual, seasonal and meteorological conditions. The condition of the soil, rock and groundwater may be significantly altered by construction activities (traffic, excavation, groundwater level lowering, pile driving, blasting, etc.) on the site or on adjacent sites. Excavation may expose the soils to changes due to wetting, drying or frost. Unless otherwise indicated the soil must be protected from these changes during construction.

Sample Disposal: Golder will dispose of all uncontaminated soil and/or rock samples 90 days following issue of this report or, upon written request of the Client, will store uncontaminated samples and materials at the Client’s expense. In the event that actual contaminated soils, fills or groundwater are encountered or are inferred to be present, all contaminated samples shall remain the property and responsibility of the Client for proper disposal.

Follow-Up and Construction Services: All details of the design were not known at the time of submission of Golder’s report. Golder should be retained to review the final design, project plans and documents prior to construction, to confirm that they are consistent with the intent of Golder’s report. During construction, Golder should be retained to perform sufficient and timely observations of encountered conditions to confirm and document that the subsurface conditions do not materially differ from those interpreted conditions considered in the preparation of Golder’s report and to confirm and document that construction activities do not adversely affect the suggestions, recommendations and opinions contained in Golder’s report. Adequate field review, observation and testing during construction are necessary for Golder to be able to provide letters of assurance, in accordance with the requirements of many regulatory authorities. In cases where this recommendation is not followed, Golder’s responsibility is limited to interpreting accurately the information encountered at the borehole locations, at the time of their initial determination or measurement during the preparation of the Report.

Changed Conditions and Drainage: Where conditions encountered at the site differ significantly from those anticipated in this report, either due to natural variability of subsurface conditions or construction activities, it is a condition of this report that Golder be notified of any changes and be provided with an opportunity to review or revise the recommendations within this report. Recognition of changed soil and rock conditions requires experience and it is recommended that Golder be employed to visit the site with sufficient frequency to detect if conditions have changed significantly.

Drainage of subsurface water is commonly required either for temporary or permanent installations for the project. Improper design or construction of drainage or dewatering can have serious consequences. Golder takes no responsibility for the effects of drainage unless specifically involved in the detailed design and construction monitoring of the system.

IMPORTANT INFORMATION AND LIMITATIONS OF THIS REPORT Standard of Care: Golder Associates Ltd. (Golder) has prepared this report in a manner consistent with that level of care and skill ordinarily exercised by members of the engineering and science professions currently practising under similar conditions in the jurisdiction in which the services are provided, subject to the time limits and physical constraints applicable to this report. No other warranty, expressed or implied is made.

Basis and Use of the Report: This report has been prepared for the specific site, design objective, development and purpose described to Golder by the Client. The factual data, interpretations and recommendations pertain to a specific project as described in this report and are not applicable to any other project or site location. Any change of site conditions, purpose, development plans or if the project is not initiated within eighteen months of the date of the report may alter the validity of the report. Golder can not be responsible for use of this report, or portions thereof, unless Golder is requested to review and, if necessary, revise the report.

The information, recommendations and opinions expressed in this report are for the sole benefit of the Client. No other party may use or rely on this report or any portion thereof without Golder’s express written consent. If the report was prepared to be included for a specific permit application process, then upon the reasonable request of the client, Golder may authorize in writing the use of this report by the regulatory agency as an Approved User for the specific and identified purpose of the applicable permit review process. Any other use of this report by others is prohibited and is without responsibility to Golder. The report, all plans, data, drawings and other documents as well as all electronic media prepared by Golder are considered its professional work product and shall remain the copyright property of Golder, who authorizes only the Client and Approved Users to make copies of the report, but only in such quantities as are reasonably necessary for the use of the report by those parties. The Client and Approved Users may not give, lend, sell, or otherwise make available the report or any portion thereof to any other party without the express written permission of Golder. The Client acknowledges that electronic media is susceptible to unauthorized modification, deterioration and incompatibility and therefore the Client can not rely upon the electronic media versions of Golder’s report or other work products.

The report is of a summary nature and is not intended to stand alone without reference to the instructions given to Golder by the Client, communications between Golder and the Client, and to any other reports prepared by Golder for the Client relative to the specific site described in the report. In order to properly understand the suggestions, recommendations and opinions expressed in this report, reference must be made to the whole of the report. Golder can not be responsible for use of portions of the report without reference to the entire report.

Unless otherwise stated, the suggestions, recommendations and opinions given in this report are intended only for the guidance of the Client in the design of the specific project. The extent and detail of investigations, including the number of test holes, necessary to determine all of the relevant conditions which may affect construction costs would normally be greater than has been carried out for design purposes. Contractors bidding on, or undertaking the work, should rely on their own investigations, as well as their own interpretations of the factual data presented in the report, as to how subsurface conditions may affect their work, including but not limited to proposed construction techniques, schedule, and safety and equipment capabilities.

Soil, Rock and Groundwater Conditions: Classification and identification of soils, rocks, and geologic units have been based on commonly accepted methods employed in the practice of geotechnical engineering and related disciplines. Classification and identification of the type and condition of these materials or units involves judgment, and boundaries between different soil, rock or geologic types or units may be transitional rather than abrupt. Accordingly, Golder does not warrant or guarantee the exactness of the descriptions.

12-1376-0017


16820 107 Ave, Edmonton, Alberta, Canada T5P 4C3 Tel: +1 (780) 483 3499 Fax: +1 (780) 483 1574 www.golder.com

Golder Associates: Operations in Africa, Asia, Australasia, Europe, North America and South America

SITE PHOTOGRAPHS (All photos taken on August 1, 2012)

12-1376-0017




Photo 1: Culvert outlet, east side of Highway 47

Photo 2: Culvert inlet, west side of Highway 47

12-1376-0017




Photo 3: East guardrail and north boundary of depression.

Photo 4: Leaning west guardrail

12-1376-0017




Photo 5: North end of pavement distress

Photo 6: South end of pavement distress

ACCESS

ROAD

CU

LVE

RT

TOE OF

EMBANKMENT

TO

H

W

Y 16

GUARDRAIL

POSTS

H

W

Y

4

7

:0

6

5 mm WIDE (2012)

5 mm WIDE (2012)

LEANING

GUARDRAIL

POSTS

5 mm WIDE (2012)

NC EDSON CALL-OUT HWY 47 06, KM 39.6

ALBERTA TRANSPORTATION

GEOHAZARD MONITORING PROGRAM

FIGURE 1

L:\2

012\1376\12-1376-0017\2000\R

epo

rt_

A\F

ig

1_

12

137

60

01

72

00

0A

001

_N

C_E

dso

nH

wy4

7.d

wg

| Layou

t: L

ayout | M

odified: A

NW

ong

0

9/2

8/2012

2:52 P

M | P

lo

tted: IG

riffin

10/16/2012

10/15/2012ID

10/15/2012EL

09/26/2012AW

09/25/2012EL

12.1376.0017.2000 12137600172000A001

1:750

15 30 45m0

REFERENCE

NOTE

1:5,000

100 200 300m0

LIDAR IMAGE OBTAINED FROM AT.

1. ALL SITE FEATURE LOCATIONS ARE APPROXIMATE

SITE DETAIL OBTAINED FROM SKETCH.

2012 FEATURES SHOWN IN RED

Documents

North Central Region – Edson Area Call-Out on Hwy 47:06 ... · Golder Associates: Operations in Africa, Asia, Australasia, Europe, North America and South America ... Highway 47