Looking at Clubhouse Erosion

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Jeremy Wolf, LISE Member and Vice-President of GeoTest Services will be presenting his observations at the next board meeting on Sunday, May 19.

This is an initial report after noticing erosion on the point on which the clubhouse stands.

General Description

The clubhouse rests on a bedrock point extending northward into Hale Passage. The west side of the clubhouse faces a cove beach and the community boat launch. Bedrock is exposed at the north and east side of the clubhouse and soil exposure is visible at its west side.

It is apparent that the west side of the clubhouse has received man-made fill that is retained by a cement and quarry rock wall. The clubhouse drain field may be present at this location. Man-made earth fill also appears to be present at the paved roadside parking area overlooking the beach.

Observations

LISE Clubhouse orientation

  • The clubhouse foundation consists of a footing, stem wall and pier system which appears to bear entirely on soil of varying thickness overlying bedrock.

  • Due to its close proximity to the bedrock slope and exposure to wave action and erosion the east side of the clubhouse is at risk.

  • At the east foundation wall, the concrete piers under the deck are on a thin layer of soil over bedrock. The setback from the slope is minimal, in some areas inches, and subject to erosion.

  • The southeast corner of the clubhouse (below the kitchen) is in jeopardy and the east ridge (below the storage closet and deck facing Mt Baker) is seriously undermined.

Photo #1: southeast corner

Photo 2: below clubhouse kitchen

  • The natural arc of the bedrock below the east side of the clubhouse captures wave energy and the jointed and fractured bedrock at this location has been undermined. It visually appears (without measurements) that if the rock overhang at this location were to fail, the east wall of the clubhouse would fail.

  • It is possible that within 15 years or less, with storm surge and wave action, the clubhouse could become unsafe and at risk of condemnation.

  • With the east foundation exposure to erosion and close proximity to the slope, ground level access under decks may be unsafe within an estimated 5 years.

  • The root systems of the large trees at the east side of the clubhouse are significantly undermined and exposed. A cedar tree and madrona tree are stabilizing the southeast of the foundation corner but wind action on the trees could cause the point to fail.

Photo #3: down from kitchen southeast corner

Phoot #4: southeast corner

  • From an engineering standpoint, slope stability modelling the existing foundations would result in an unsuitable safety factor and likely failure during seismic conditions. In plain English, the clubhouse would likely not survive an earthquake.

  • Immediate prevention: reroute downspouts away from edge to reduce erosion.

Photo #5: east foundation wall