Journal of Cold Regions Engineering

In northern rivers, reaches of open water in the ice cover may exist throughout the winter season. Some of these reaches are the result of a tributary effluent of higher temperature or of fast‐moving water that alter the thermal and hydrodynamic conditions of ice‐cover progression. The temperature distribution downstream of the point of effluent discharge is controlled by the hydrodynamic characteristics of the stream and the meteorological conditions prevailing at the site. This paper deals with the development and the testing of an analytical approach concerned with the suppression of ice cover from the point of effluent discharge up to the ultimate advancing of its fronts. The the‐oretical formulation is based on a quasi‐one‐dimensional approach; however, it allows for special consideration of the nonlinear variation in the stream geometry and adjustment for a partial mixing assumption. The formulation of the upstream ice‐edge location is developed based on the 0 °C isotherm. The up‐stream and the downstream ice edges are investigated for the unsteady uniform flow and for the steady nonuniform flow. Conditions for the nonsuppression of the ice cover are also obtained based on the relative positions of the upstream and downstream ice edges. Comparison with field data suggests a good agreement with the formulation incorporating the thermal velocity effluent.

A computational method is developed for analyzing the hydraulics in a channel network with ice cover under steady‐state conditions. The formulation permits computations for networks in which both ice‐covered and free‐surface areas exist. The network resistance coefficient, as well as the discharge distribution and water surface profiles in each reach, is computed. Application of the method to the upper St. Lawrence River is presented, along with discussion of the spatial and temporal variations of ice cover resistance coefficients.

In 1983, CH2M HILL was named design/construction manager for a $35‐million project to expand Anchorage's wastewater treatment plant. The project will double the size of the Anchorage Water and Wastewater Utility's existing primary treatment plant to 2005 design year flows of 54 mgd $(2.4m^3/s)$ average day, and 128 mgd $(5.6m^3/s)$ maximum day. Significant design and construction considerations include stabilizing a bluff against erosion by ice and other forces; installing a new outfall diffuser in upper Cook Inlet; maximizing construction efficiency by minimizing impacts from darkness, cold, and winter storms; providing a system to economically heat sludge thickeners and primary clarifier scum boxes; protecting clarifiers during their first winter; and extending a multifunction utilidor system. Construction of the new diffuser is expected to be complete by September 1987. The project is expected to be complete, with the expanded plant in full operation, by early 1988.