Eagle River High School

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Erosion Problem at Yosemite Drive

Download third party report by Shannon & Wilson, Inc.

As you may know, complaints have been made regarding the impact that Eagle River High School (ERHS) drainage is having on the subdivision at the end of Yosemite Drive (Eagle Pointe Subdivision). The results of a third-party review of this issue are outlined below.

The Anchorage School District hired a third-party engineer to determine what caused flooding on Yosemite Drive and the subsequent erosion to the bluff in that area. The engineering firm selected, Shannon and Wilson, Inc., was also approved by the Municipality of Anchorage Engineering Department. The third party report is available here.

These are the three basic findings:

1. The bluff’s slope erosion is the direct result of municipal street maintenance pumping actions to prevent flooding of neighborhood homes. These actions were taken in December 2004 during a period of warm temperatures and relatively heavy rain.

2. The drainage system from the Eagle Pointe Subdivision retention basin failed, thus preventing the system from draining the water to Eagle River as designed. This failure was most likely due to surface pipe movement, separations and blockage due to freezing. The faulty drain pipe is part of the Eagle Pointe Subdivision drainage system.

3. The retention basin constructed on the Eagle River High School site is not impacting the stability of the bluff. Engineers determined that even under the most unfavorable conditions (the basin remains full year-round), it would take water approximately 80 years to migrate underground from the retention basin to the slope face of the bluff.

Another third-party consultant is working with the municipality, the Eagle River High School design team and the school’s construction contractor to determine if actions on the school site are causing excessive surface water to drain improperly. If that is the case, the district will fix the problem during the upcoming spring and summer months of 2005. In the interim, the district has established barriers to direct surface water from the school site to its retention pond.

The Anchorage School District is committed to quality construction practices and cooperation with neighborhoods throughout the municipality. We will continue that practice and welcome your questions and comments. Please contact the Assistant Superintendent for Support Services, George Vakalis, at 742-4305 if you would like additional information or clarification.

We welcome your questions and comments: George Vakalis Assistant Superintendent for Support Services 742-4305 OR use our online comment box