The fly-fishing community opposed this strongly, and eventually when test borings showed that the bedrock in those valleys could not support the necessary dams, the city relented.
Extensive test borings were made to determine the suitability of the land, and pressure tests were carried out on the material to be used in construction to determine its durability.
Deep excavations in 2007 confirmed findings from earlier test borings, that several types of earth and clay from different sources had been used successively.
One large scale excavation was carried out in 1974-76, while test borings in 1984-87 indicated that some of the archeological layers extend far into the lake.
