Report of Geotechnical Review - 237 Anya Lane

January 15, 2015

Levelton File # R715-0112-00

Mr. David Cung 237 Anya Lane Victoria BC

Attention: Mr. David Cung

Project: Retaining Wall Review – 237 Anya Lane, View Royal Subject: Report of Geotechnical Review

Further to our Field Review Report dated November 21, 2013, Levelton provides this letter to discuss the geotechnical aspects of the existing retaining wall at the above-referenced property. The retaining wall was constructed by Design West Construction Ltd., for whom Levelton was employed to conduct the November 2013 review. It is understood that the Town of View Royal has asked that the wall be considered in regard to slope stability and bank erosion as part of the Environmental Development Permit Application for the subject property.

The retaining wall was constructed as a stacked boulder wall to retain a gravel-surfaced driveway that accessed the lower portion of the property, on the foreshore of Millstream Creek. The toe of the wall was excavated into dense, native, silty sand and is situated at least 6m away from the crest of the slope that extends approximately 3 to 4m down to Millstream Creek. The foreshore slope angle was measured to have a localized maximum of 35 degrees and the soil exposures observed along the bank consist of the same dense, silty sand material observed at the toe of the retaining wall.

Retaining wall construction ranged in height from 1 to 4m and was conducted with large (~1m diameter), angular boulders. The boulders were interlocked during placement and sloped back at an approximate 1H:1V slope where possible. As the Owner wished to protect some trees at the toe of the slope, the face batter of the wall was increased to a maximum 3/4H:1V in some localized locations. Backfilling was conducted concurrently with boulder placement and a free-draining, granular material was observed to be used as backfill, which will provide support for the gravel driveway.

As the toe of the wall is located above the high water mark and on an approximately level portion of ground 6m away from the crest of the slope, erosion at the toe of the boulder wall is expected to be minimal and based on the size of the boulders and free-draining nature of the backfill, the integrity of the wall will not be compromised as a result of erosion. Slope stability review of the wall configuration indicates that the wall is stable under static conditions. Using the design seismic loading, there is potential for a toppling-type failure, where the boulders along the upper row would become detached and roll down the wall face. As the wall is located a minimum 6m onto the subject property, the expected rollout of a toppling failure would be contained on the property and as such, the consequence of failure is minimal. The Owner has been made aware of this risk during the design.

This report has been prepared for Mr. David Cung in accordance with the attached Terms of Reference for Geotechnical Reports. The Town of View Royal is considered an authorized user of this report. We trust that this information meets your current needs.

Yours truly,

Levelton Consultants Ltd.

Per: Alec Morse, P. Eng.

Reviewed by: Russell Scott, M.Sc., P.Eng.

Attachment(s): Terms of Reference for Geotechnical Reports