REMOVAL OF THE ORIENTA DAM AND CONSTRUCTION OF FISH AND LAMPREY BARRIER

摘要

In September 1985, a significant rainfall occurred in northern Wisconsin near the town of Port Wing. The event was so large that a significant amount of trees and brush washed downstream where it accumulated on the Orienta dam, including the tainter gate spillway. Once the operator reached this remote dam site, he found that the overflow spillway and tainter gates were blocked by an enormous amount of debris and were inoperable. The dam was soon overtopped, causing the left earthen embankment to fail with a large section washed downstream. Feasibility studies were performed to evaluate redevelopment of the dam and the damaged powerhouse and generating facilities. The evaluations did not result in the site being redeveloped. In 1996, Northern States Power (Xcel Energy) applied for an abandonment permit with the Wisconsin Department of Natural Resources (WDNR). Removal of the Orienta dam caused a variety of responses. Local residents both wanted the dam rebuilt and the reservoir restored and others wanted the dam permanently removed to restore a free flowing river. These local differences as well as concerns with fish and lamprey movement from Lake Superior to the upstream waters that had resident brook trout and a Federal cold water fish hatchery raised concerns with regards to the scope and configuration of the removal project. After a series of meetings with the Federal, State, and local agencies as well as the public, resolution for the final removal of the Orienta dam and abandonment and restoration of the site was established in 2001. Plans were developed for substantial removal of the dam and construction of a new fish and lamprey barrier to restrict movement of fish and lamprey from Lake Superior upstream to native trout waters. Only the dam foundation was to remain to allow construction of the fish and lamprey barrier. To insure that the lamprey barrier (of which the old dam acted as such) was intact for fish lamprey migrations, removal of the dam and subsequent installation of a barrier needed to be closely coordinated. In order to coordinate the engineering and construction, Xcel Energy partnered with the WDNR to use one engineering firm and one contractor to complete removal of the dam and construction of the barrier. Xcel Energy paid for the removal and construction of the fish and lamprey barrier was paid by the WDNR. This plan initiated teamwork that was critical to allow a coordinated, and timely completion of the project work in a cost effective manner. Explosives and conventional construction removal methods were used to remove the dam within a few months in the fall of 2001. This paper discusses the technical aspects of how the removal items were kept to a minimum and on-site disposal was maximized to provide an economic removal. This item included an agreed upon removal plan established between Owner, Agencies and Contractor. Although difficult, the use of a performance specification approach saved engineering and contractor costs that resulted in an acceptable product by all stakeholders.