Structural Condition
North and South Pylons (Waterline Supports) Three masonry pylons are the remaining extant features of a waterline support constructed of a mixture of local sandstone, tumbled field stones from the creek, and salvaged blocks of early concrete. The masonry has been repointed with a hard, cementitious mortar. The structures generally taper from the base to the top and there are some remnants of metal components embedded into the masonry structures, such as the metal bar atop the northernmost pylon. The northernmost pylon is on the north bank of Boulder Creek, while the southern two pylons are on the south bank of Boulder Creek. The two on the south bank were inaccessible at the time of the observation visit since they require access through private property. Overall, the masonry pylons are in fair condition. Although there are no signs of major failure or displacement, there are several issues that could be improved to increase the longevity of the pylons. Most of the following were identified at the north pylon due to access, but likely occur at the other pylons as well. Several of the masonry units, primarily the reused concrete, have cracked. Some stones are missing. In some areas, mortar is missing between the stones. Additionally, the mortar is quite hard or cementitious for direct contact with the softer stones (i.e. the sandstone). The parge coat cap atop the masonry pylon is cracked and does not cover all elements. Biogrowth on the masonry is abundant in shady areas of the pylons. The pylons directly adjacent to the banks of Boulder Creek are slightly undercut due to scour from the moving creek water. Steel Girders Extending north from the northernmost pylon are two built-up girders. These elements consist of a vertical plate riveted to a channel at the top and bottom. The open side is faced with a lattice of thin steel strips. At the south end, they bear on the masonry pylon while at the north end they now bear on grade. The girders are in fair condition. Although they are structurally stable, the north ends of the girders are currently buried in the earth. If there is no substantial foundation element below these ends, the soil could settle and cause the north end of the girders to settle as well. Also, there are areas of the girders where rust has started to form due to exposure to the elements. Lastly, there are trees and other plants growing in close proximity to the steel girders that could cause the steel girders to displace if the plants grow larger.
Figure 1-14. Southern pylons on south side of Boulder Creek, 2020 (source: JVA)
Figure 1-13. Biogrowth and areas of missing mortar, 2020 (source: JVA)
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