|The initial topsoil removal and cutting back of the bank (notice the eroded area close to the structure footing), while Crow Creek Nation archaeological monitor looks on.|
In May, floodwaters engulfed the Crow Creek Reservation located in central South Dakota, damaging several roads and structures. Flash flooding eroded a ravine next to one of Western’s transmission towers located on private land within the reservation boundary. The erosion endangered both the tower and the line’s operability and reliability near a 230-kilovolt steel transmission line. Had the bank caved to the edge of the footing, the tower would have begun to lean and could eventually have collapsed, cutting power to the customers who rely on the line. Western’s Upper Great Plains region employees, in cooperation with the Crow Creek Nation, worked to prevent its destruction.
Western’s Engineering and Maintenance employees determined that the best way to fix the erosion problem was to use simple but effective Gabion baskets to stabilize the bank and divert water away from the structure. Gabion baskets are large wire baskets filled with rip-rap and connected together—in this instance, three tiers high— to divert the flow of water away from an eroding bank. Initially, the floor of the ravine was leveled in order for a track-hoe to cut back the bank for the placement of the baskets. Filter fabric that allows for the passage of water, but not sediment, was layered between the baskets, and the soil from the excavated bank was then filled in behind the baskets. A layer of clay was then placed in the ravine in front of the baskets to prevent soil from eroding out from underneath.
The Crow Creek Nation, as stewards of the cultural resources within the reservation boundaries, felt that it was important to protect and preserve these sites. It’s also Western policy to preserve, protect and avoid disturbance to cultural resources whenever possible. For that reason, UGP developed several project alternatives to address the emergency situation without damaging the archaeological sites. Western was able to keep its construction “footprint” to a minimum, thereby reducing the amount of ground disturbance around the project area.
Field work began Nov. 2 and concluded within two weeks. Nice weather conditions helped the work progress quickly. Following completion of the project, Western restored the excavated bank and reintroduced the removed vegetation to the topsoil so that it has a chance to recover in spring.