introduction - alberta · 2018-05-15 · alberta transportation con0017609 southern region g rmp...

1601003L S053 879.04 Road Settlement-Callout.docx A05115A03

Klohn Crippen Berger LTD. • Suite 301, 2627 Ellwood Drive SW • Edmonton AB T6X 0P7 • CANADA 780.444.0706 t • 780.481.2431 f • www.klohn.com

October 3, 2016

Alberta Transportation 2nd Floor, 803 Manning Road NE Calgary, Alberta T2E 7M8 Ross Dickson Project Service Technologist Dear Mr. Dickson: CON0017609 Southern Region GRMP - Call-Out Reports S053 – Hwy 879:04 Road Settlement (km 1.225) (aka “Rattlesnake Dip”)

1 INTRODUCTION

As part of the Geohazard Risk Management Plan (GRMP) Contract for the Southern Region, Klohn Crippen Berger (KCB) was requested by Alberta Transportation (AT) to conduct a call-out inspection of a location of a 20 m long dip in the paved road surface on Highway 879 (H879:04 - km 1.225) 1.225 km north of the Town of Foremost, Alberta along H879.

The site is located at 49°29.347' N, 111°26.5507'W (WGS 84 ) on Highway 879:02 (km 1.225) in Contractor Maintenance Area (CMA) 24.

The site was inspected on June 16, 2016 by Chris Gräpel, M.Eng., P.Eng., Tim Keegan, PhD., P.Eng., and Andrew Brunsdon, P.Eng. of KCB, with Mr. Ross Dickson and Roger Skirrow, P.Eng. of AT. AT reported that the road/pavement has been settling during the last four years. Pavement cracking was not present at the time of the site visit.

This call-out report represents the first documented engineering visit to this site. This report was prepared by KCB for AT Southern Region under Contract No. CON0017609. The results of our site inspections, assessments, and our recommendations for remediation works are presented herein.

2 BACKGROUND

This is a new site that was brought to AT’s attention by the MCI for this area (Warren Lagler) who reported that the road surface has been settling for the last 4 years. Although the dip has been raised with ACP patching (frequency unknown), the rate of settlement did not appear to be slowing down.

The average annual daily traffic (AADT) along Hwy 879 near the site is 510 northbound (Reference No. 65170).

Alberta Transportation CON0017609 Southern Region GRMP

Call – Out Reports S053 – Hwy 879:04 Road Settlement (km 1.225)

1601003L S053 879.04 Road Settlement-Callout.docx

A05115A03 October 2016

3 SITE OBSERVATIONS

The various features observed at the site during the June 16, 2016 site visit are presented in appended Figure 1 and Photos 1 through 5 in Appendix I. The following observations were made during the site visit:

The section of the highway undergoing settlement is perched at the top of a partially filled erosion gully.

There is evidence of numerous pavement lifts in the section with one relatively recent. No cracks were observed in the recent asphalt.

Photos 1 and 2 illustrate the dip in the road pavement was observed coincident with an enclosed depression on the west side of the highway ditch. Figure 1 further illustrates that an apparent seepage erosion feature on the east side in the embankment fill, supporting the east side of the highway,, is also in line with the dip in the road pavement (see Figure 1). The apparent seepage erosion feature on the east side of the highway was not identified during the site inspection but rather during careful examination of the imagery.

The high embankment fill, supporting the east side of the road, appears to be filling the head of a pre-existing gully (see also Photo 4).

The enclosed depression has no indication that surface flows run in or out of it inferring that the loss of material forming the depression is from below.

An investigation of the surrounding area revealed no evidence indicating the dip in the road or enclosed depression were associated with landslide movement.

4 GEOLOGIC SETTING

A review of readily available topographic, geologic, and surficial soil maps indicate the site is located in the prairies of southern Alberta. Figure 2illustrates that regionally, at prairie level the terrain is predominantly stagnant ice, ice-thrust, and ground moraine deposits. These deposits are dissected by broad glacial outwash valleys, several hundreds of meters wide and approximately 50 meters deep. The glacial outwash valley (Chin Coulee) to the north of the site contains some remnant lakes, which have either formed naturally or by the construction of dams. The valley slopes of this reach of the Chin Coulee are marked by distinctive horizontally bedded sedimentary rock outcrops. Figure 3 (Detail A) also shows evidence of bedrock leaching from these outcrops, possibly of carbonaceous shale layers of the Foremost Formation.

The bedrock underlying quaternary sediments consists of the Foremost Formation which contains several bodies of sandstone, mudstone and carbonaceous shale (Gordon, 2000). It also contains some areas with coal-rich deposits. The foremost Formation represents several sequences marking the transition between marine mudstone (calcareous), foreshore sandstone and non-marine carbonaceous shale.





5 TERRAIN ANALYSIS

KCB conducted a terrain analysis of the surrounding landforms to better characterize the geomorphological processes and surficial material that have resulted in their formation. Particular focus was on characterizing the materials and processes that may be effecting the settlement of the road. Geomorphological observations of surficial material, landforms and geological processes, were classified based on the Terrain Classification System described by Howes and Kenk (1997). Landforms are portrayed on Figure 2 as polygons and characterized using a terrain symbol composed of a group of letters (typing) that provide information about the landform. Table 1 summarizes the details of the terrain classifications assigned to the various terrain types shown in Figure 2.

The terrain analysis interprets the S053 site to be situated close to the boundary of terrain types 2, 3 and 6. Terrain type 3 is described as a glaciolacustrine deposit being modified by failing or piping, overlying subdued morainal materials. The flat glaciolacustrine deposits in terrain types 2 and 3 are incised with a distinctive pinnate drainage pattern that feeds into Chin Coulee. Some of these gullies extend up to several kilometers into the plains. Pinnate drainage pattern is indicative of a high silt content of the soil. The S053 site appears to be near the head scarp of a partially filled pinnate gully. It is inferred the fill was placed during the original construction of Highway 879.

Further observations from the terrain analysis are as follows:

Just south of the meltwater spillway, approximately 1 km northeast of the site, a number of enclosed depressions, similar to the one observed at the site were observed (Figure 3 Detail A).

Figure 3 (Detail A) also shows evidence of possible saline drainage from the soil and/or bedrock.





Table 1 Details of the terrain classifications assigned to the various terrain types shown 2.

Type Strata Genetic Material Qualifying Descriptor

Surface Expression

Modifying Process Descriptive Symbol Description

1 Upper Lacustrine Sediments (L) Glacial (G) Veneer (v) N/A

𝐿𝐿𝐺𝐺𝑣𝑣𝑀𝑀𝐺𝐺ℎ

or𝐿𝐿𝐺𝐺𝑣𝑣𝐹𝐹𝐺𝐺ℎ

A glaciolacustrine veneer, overlying

hummocky morainal materials or fluvial sediments Lower Morainal Materials (G)

or Fluvial (F) Glacial (G) Hummocky (h) N/A

2 Upper Lacustrine Sediments (L) Glacial (G) Level (l) N/A 𝐿𝐿𝐺𝐺𝑙𝑙

𝑀𝑀𝐺𝐺𝑚𝑚

A glaciolacustrine deposit, overlying subdued morainal materials Lower Morainal Materials (G) Glacial (G) Subdued (m) N/A

3 Upper Lacustrine Sediments (L) Glacial (G) Level (l) Failing (F) or

Piping (P) 𝑳𝑳𝑮𝑮𝒍𝒍−𝑭𝑭𝑴𝑴𝑮𝑮𝒎𝒎

and/or 𝑳𝑳𝑮𝑮𝒍𝒍−𝑷𝑷𝑴𝑴𝑮𝑮𝒎𝒎

A glaciolacustrine deposit being modified by failing or piping, overlying subdued morainal

materials Lower Morainal Materials (G) Glacial (G) Subdued (m) N/A

4

Upper Lacustrine Sediments (L) Glacial (G) Level (l) Piping (P) 𝐿𝐿𝐺𝐺𝑙𝑙 − 𝑃𝑃𝑀𝑀𝐺𝐺𝑚𝑚

A glaciolacustrine deposit being

modified by piping, overlying subdued morainal materials Lower Morainal Materials (G) Glacial (G) Subdued (m) N/A

5 Upper Bedrock (R) N/A Ridged (r) Karst Modified (K) 𝑅𝑅𝑅𝑅 − 𝐾𝐾 A ridge of bedrock being modified by dissolution

6 Upper Colluvial Materials (C) N/A Steep (s) N/A 𝐶𝐶𝐶𝐶 Steep slopes of colluvial materials

7

Upper Fluvial (F) N/A Veneer (v) N/A 𝐹𝐹𝑣𝑣𝐹𝐹𝐺𝐺

or 𝐹𝐹𝐺𝐺 A veneer of fluvial materials,

overlying fluvioglacial deposits; or fluvioglacial deposits Lower Fluvial (F) Glacial (G) N/A N/A





6 ASSESSMENT

There is insufficient technical evidence available at this point to conclusively assess the cause of the dip at this site. The dip at the subject site could be due to settlement of poorly compacted fill in the gully. However, it is apparent from the indicators described in the previous sections that the ongoing road settlement could also include some combination of adverse ground conditions and processes of internal erosion such as:

Piping - induced by regressive erosion of particles from downstream and along the upstream line towards an outside environment until a continuous pipe is formed. Piping occurs when water flowing through material opens a tunnel or pipe that remains open and continues to erode material. Piping is dependent on the hydraulic gradient; soil permeability; preferential flow paths; ability to maintain an arched opening; chemical makeup; and the erosive nature of the material. As piping progresses, the flow path shortens, the hydraulic gradient increases and the piping accelerates up the flow path.

Seepage Erosion - due to exit velocity of groundwater is sufficient to cause particle erosion. It is dependent on the hydraulic gradient, soil permeability, preferential flow paths, chemical makeup and the erosive nature of the material. As erosion occurs, the hydraulic gradient is increased, which further increases exit velocities and seepage erosion.

Suffusion - induced by seepage flow causing the migration of soil particles through the soil matrix. It is dependent on the soil permeability, preferential flow paths, gap grading of particle sizes, and the erosive nature of the material.

Dispersion - the process in which clays saturated with sodium ions ("sodic soils"), soil can break down very easily into fine particles and wash away under seepage gradient. Dispersive clays differ from ordinary, erosion resistant clays because they have a higher relative content of dissolved sodium in the pore water.

Based on the collaborating evidence in Figure 1 showing the alignment of the enclosed depression (west side); the section of road settlement; the seepage erosion feature; and the relative location of the site near the head scarp of a pinnate erosion gully the leading hypothesis or probable failure mode involves a combination of piping and seepage erosion. This is by no means conclusive and further assessment will require additional investigation as recommended in Section 9.





7 RISK LEVEL

Risk levels have not been prepared for this site to date. The following risk assessment is based on the piping-seepage erosion hazard scenario as it is currently the most probable failure mode.

Risk levels for AT GRMP sites are determined according to the following:

Risk Level (RL) = Probability Factor (PF) x Consequence Factor (CF)

Where:

PF varies from 1 (inactive, very low probability of slide occurrence) to 20 (catastrophic slide is occurring).

CF varies from 1 (minor consequences, no impact to driver safety, maintenance) to 10 (safety of public at risk, loss of infrastructure, rapid mobilization of large slides).

It is important to note that the GRMP Risk Level system was developed primarily for landslides and therefore the risk level associated with this site (primarily erosion) was interpreted from the existing scale by replacing slide terminology with erosion (i.e., inactive slide with moderate probability of remobilizing was replaced with inactive erosion with moderate probability of remobilizing).

A risk level for this site is assessed as follows:

PF (12) x CF (6) = RL (72)

The probability factor of 12 reflects that potential for internal erosion processes to have caused continuous or incremental settlement of the road. Additionally, if this is dip is due to seepage and piping erosion, the nature of both piping and seepage erosion is that the more they progress the higher the likelihood the erosion will accelerate, potentially resulting in a sinkhole in the road.

The consequence factor of 6 reflects that ground collapse may cause complete closure of the road.

8 RECOMMENDATIONS

8.1 General

Given the observations of settlement over the past four years, the settlement of the road is still active. However the processes and mechanics of internal erosion, suspected to be causing the settlement, are not fully understood and thus the remediation measures are also not readily apparent. Therefore, further field-based investigation is recommended to better understand the cause of road settlement, and propose long term remediation options. Key parameters required to investigate, assess and remediate the geohazard include:

stratigraphic profile;

material properties both physical and chemical;





petrology of the soils and possibly the bedrock;

past and future behaviour of the road surface;

surface expression of contributing processes; and

ground water hydrology (seepage analysis).

The proposed short-term and long-term repair recommendations for the road settlement are discussed in the following subsections.

8.2 Short Term

In the short term the MCI should continue to monitor the settlement of the road and, if the extent and depth of the dip appears to accelerate, install hazard signs and a speed reduction. In addition the AT Pavement LiDAR data should be analyzed to assess the road surface settlement behavior over the past 5 years. AT maintenance records will be requested to assess the thickness of asphalt placed at this site over the past five years. The estimated cost of processing the AT pavement LiDAR data is $3,500.

8.3 Long Term

If a long term settlement trend is confirmed with review of the AT pavement LiDAR data, survey monitoring pins should be installed at pavement edge and on centreline and survey monitor should be conducted quarterly or more frequently, depending on the rate of movement. Addition pavement LiDAR data will be requested for future surveys to update the record of settlement.

Given the number of unknowns about the adverse ground conditions and destabilizing processes that are causing the road settlement and apparent internal erosion, KCB recommends a phased investigation approach. The recommended preliminary subsurface geotechnical investigation consists of two hollow or solid stem auger boreholes drilled through the surface deposits and into firm ground or bedrock (estimated depths 30m to 50m) to assess fill and soil/bedrock conditions and to install instrumentations to monitor depth to groundwater in the deposits and bedrock and to assess the depth and kinematic character of movement within the disturbed soil mass. Disturbed and undisturbed samples would be taken to complete an index and strength testing laboratory program to develop material parameters.

The rough order of magnitude costs for survey of survey monitoring points (one year), review of additional AT pavement LiDAR data and preliminary subsurface geotechnical investigation including surveying, drilling investigation, and report is between $50,000 to $70,000. A detailed proposal for further engineering services can be prepared upon request and after discussion with AT.





REFERENCES

Environment Canada, 2016. http://climate.weather.gc.ca/ (website visited on July 15, 2016).

Fenton, M.M., Waters, E.J., Pawley, S.M., Atkinson, N., Utting, D.J., Mckay, K., 2013. Surficial geology of Alberta. Alberta Energy Regulator, AERéAGS Map 601, scale 1:1,000,000.

Gordon, J., 2000. Stratigraphy and sedimentology of the Foremost Formation in Southeastern Alberta and Southwestern Saskatchewan. Master Thesis, University of Regina.

Hamilton, W.N., Langenberg, C.W., Price, M.C., Chao, D.K., 2012. Geological Map of Alberta. Alberta Geological Survey, Map 236 at 1:1,000,000 scale.

http://climate.weather.gc.ca/





FIGURES

³³³

To be read with KCB report dated September 2016

CLIENT PROJECT AS A MUTUAL PROTECTION TO OUR CLIENT, THE PUBLIC AND OURSELVES, ALL REPORTS AND DRAWINGS ARE SUBMITTED FOR THE CONFIDENTIAL INFORMATION OF OUR CLIENT FOR A SPECIFIC PROJECT AND AUTHORIZATION FOR USE AND/OR PUBLICATION OF DATA, STATEMENTS, CONCLUSIONS OR ABSTRACTS FROM OR REGARDING OUR REPORTS AND DRAWINGS IS RESERVED PENDING OUR WRITTEN APPROVAL. FIG No. PROJECT No.

TITLE

S053 H879:04 Site Layout

1 A05115A03

S053 H879:40 – Road Settlement

Erosion

Dip in Road

Area of Road Settlement

Apparent Seepage Erosion Feature (to be confirmed)

Enclosed Depression S053 H879:40 – Road Settlement

Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA,USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS UserCommunity

File: Z:

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M\A051

15A03

ABT S

outher

n Regi

on GR

MP\40

0 Draw

ings\2

016\H8

79-04\

160901

H879-

04 Fig

2.mxd

SOUTHERN REGION GEOHAZARD RISK MANAGEMENT PROGRAM

S053 H879:04 - Road Settlement Physiography and Surficial Geology

A05115A03 2

PROJECT

TITLE

PROJECT No. FIG No.

CLIENT

³

0 1,000Metres

1. HORIZONTAL DATUM: NAD832. GRID ZONE: UTM Zone 12N3. IMAGE SOURCE: World Imagery from ESRI

ArcGIS Online. Image dated July 15, 2012

SCALE

NOTES:

Time: 1

2:20:4

7 PM

Date:

Septe

mber 0

1, 2016

1:25,000

Kettle holes

5

?

6/76/7

5

5

5

4

5

5

_̂Foremost

5

2

2

1

2

2

2

5

Pinnatedrainage

3

Site H879:04

GLACIAL OUTWASH VALLEY (Chin Coulee)

X

AS A MUTUAL PROTECTION TO OUR CLIENT, THE PUBLIC AND OURSELVES, ALL REPORTS AND DRAWINGS ARE SUBMITTED FOR THE CONFIDENTIAL INFORMATION OF OUR CLIENT FOR A SPECIFIC PROJECT AND AUTHORIZATION FOR USE AND/OR PUBLICATION OF DATA, STATEMENTS, CONCLUSIONS OR ABSTRACTS FROM OR REGARDING OUR REPORTS AND DRAWINGS IS RESERVED PENDING OUR WRITTEN APPROVAL.

To be read with KCB report dated July 2016

CLIENT PROJECT

FIG No. PROJECT No.

TITLE

Site H879:40 – Road Sag

Google Earth Observations

3 A05115A03

North

200 m

Detail C

Detail A

Detail C

Detail C Detail B

Detail A

Detail B

Enclosed Depression Ground deformation ?

Collapse features

Leaching

Area of Road Settlement

Apparent Seepage Erosion Feature (to be confirmed)





APPENDIX I Photographs


S053 – Hwy 879:04 Road Settlement (km 1.225)

161003 Photographs.docx

Page I -1 A05115A03 October 2016

Appendix I Photographs

Photo 1 Dip in road coincident with enclosed depression feature. Photo taken facing south on June 16, 2016.

Photo 2 Embankment fill at head of gully in line with dip in road and enclosed depression feature. Photo taken facing southwest on June 16, 2016.

Dip in the road

Embankment fill at head of gully

Dip in the road Enclosed depression feature

Erosion Feature


S053 – Hwy 879:04 Road Settlement (km 1.225) Appendix I - Photographs



Photo 3 Lower portion of highway embankment fill in a gully. Photo taken facing south on June 15, 2016.

Photo 4 Enclosed depression feature. Note no apparent flow erosion in or out of depression. Photo taken facing northeast on June 2, 2016 by MCI.


S053 – Hwy 879:04 Road Settlement (km 1.225) Appendix I - Photographs



Photo 5 Dip in road approximately 20m long section and 0.15 to 0.3 m deep. Photo taken facing south on June 2, 2016 by MCI.

Dip in the road

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