The Town has taken temporary emergency actions to mitigate and/or reduce the possibility of slide movement by stock piling soil at the toe of the slide to add a resistive force, and they have constructed temporary drainage facilities above the slide to divert surface runoff away from the slide head scarp.
During the first two weeks of the landslide movement the Town installed 2 isolation valves on the 12-inch water main, one on the east end and one on the west end of the effective landslide area, which will help shut down 12-inch main water flow through the landslide area. We also installed 2 fire hydrants at the same locations which allows us to jumper/reconnect with a temporary above ground temporary water hose from the east fire hydrant to west fire hydrant through the affected landslide area. This only restores some domestic water pressure and flow but will not provide critical fire flow. The Town also continues to perform video surveillance of the sewer mains.
Water Main Concerns
The Town recognizes if the slide is not mitigated in the next few years, that the accumulation of movement may over-stress buried utilities, including the water main. This is why the Town is actively pursuing mitigation of the slide and the funding in order to accomplish it. The Town mentions the risk of future water main problems because this is one of the risk factors for needing to construct permanent long-term slide mitigations. At the current rates of slide movement, it is our engineer’s assessment that it would take more than a few years to over-stress the buried water main. Therefore, in the short term, this risk is manageable with monitoring and pipeline inspections.
If there was substantial movement of the slide it could break the 12-inch diameter ductile iron water line on the north side of Broadway, similar to how the slide broke the 8 inch ductile iron pipes in Budge Drive. It could also break the 8 inch diameter PVC sewer main on the north side of Broadway. The broken 12-inch water line could discharge up to 6,400 gallons per minute of water, flooding Broadway and disrupting traffic. The Town maintenance staff may not be able to close the two isolation valves to prevent complete draining of the tank however there would be substantial damage to Broadway, loss of water supply to the area this 12-inch main supplies water to in Jackson. This could contaminate the water system from the sewage leaking from the broken sewer line.