Retaining wall protects lake’s shoreline

The St. Paul (Minn.) Parks and Recreation Department recently completed installation of a segmental retaining wall along the shoreline of Como Lake. The retaining wall is part of a project to improve the lakeside area.

Before the retaining wall was installed, a sloping bank made the shoreline subject to variable conditions, like the weather and waterline, and the lakeside area was difficult to use. The retaining wall leveled the elevation along the shoreline and formed a boundary between the lake and a nearby pavilion.

Don Ganje, a designer employed by the St. Paul Parks and Recreation Department, came up with a basic plan for the wall. Oakdale, Minn.-based Versa-Lok served as the project engineer.

Construction of the wall was a joint effort of the St. Paul Parks and Recreation Department, the Twin Cities Tree Trust and the Summer Youth Employment and Training Program, a state-funded program under which low-income and high-risk youths are hired to work on city projects. About 30 teens worked over two summers to complete 75 percent of the wall. Twin Cities Tree Trust provided crew leaders, tools and support services for the project, and the city paid for materials. The wall was constructed on non-rigid, granular leveling pads so it could tolerate minor earth movement without damage. Concrete units were stacked without mortar and reinforced with horizontal layers of geogrid soil. Mortarless construction allows water to pass through the structure’s joints and helps prevent excess hydrostatic pressure from forming behind the wall. The top surface of the wall is a layer of clay to keep water from building up behind the wall.

The project began in 1999, and construction was completed during the fall of 2000. The retaining wall is part of a project that will be finished next summer when the city crew puts final touches on a plaza for the Como Lake Pavilion. The final phase of the project will include paving and landscaping.