Highway Construction Impact on Water-Supply Lakes

A unique opportunity existed and was taken advantage of, in Halifax, to assess the environmental impact of highway construction on four water-supply lakes (Long Lake, First Chain Lake, Second Chain Lake, and Withrod Lake) two of which were as close as 30 ft (10 m) from the proposed highway. Although the water qualities of Long and Chain Lakes have not deteriorated significantly as a result of construction, certain parameters such as conductivity, chloride, and total organic carbon have been increasing throughout the study period indicating the increasing uses of the watersheds. The gabions, intended to be the pollution control devices, were not effective in reducing the suspended impurities in the runoff, because the surface runoff bypassed the gabions in some cases and the pore sizes of the gabion structures were too coarse to effectively filter the water in other cases. However, sand bags installed near the First Chain Lake were successful in diverting runoff from the construction site and, thus, reduced the pollution load entering that lake.