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Main Canal Siphon at IH-10 Slope Failure Repair, Highlands, Texas
Constructed in the late 70s, the Main Canal is a part of the Trinity Water Conveyance System between the Trinity River and Lynchburg reservoir located south of IH-10, and east of San Jacinto River near Highlands, Texas. A siphon structure serves as an underpass at IH 10 between the main canal and Lynchburg Reservoir. A rotational failure had occurred immediately downstream of the Main Canal siphon inlet structure and Coastal Water Authority (CWA).
Our task was to find a long-term solution for a slope failure downstream of the Main Canal siphon inlet structure. CWA provides untreated surface water for municipal purposes to the cities of Houston, Baytown, and Deer Park and approximately 100 industrial customers. Failure of the siphon would reduce available water supply to less than a month.
To assure reliable water service to CWA customers by designing and constructing durable repairs to the siphon inlet.
Working as a sub-consultant for Lockwood, Andrews & Newnam, Inc. (LAN), HVJ Associates® (HVJ) performed a geotechnical investigation at the site, evaluated the potential cause or causes of failure and developed repair alternatives. HVJ reviewed the as-built drawings, established groundwater level, soil parameters, and identified the factors that could have triggered the failure. Back-analysis of the slope failure was performed to establish a model that resembles the actual failure occurred.
HVJ developed several options to reuse the slide material by strengthening or reinforcing the material before replacing it. In addition, we investigated a possibility to reinforce the slide material in place with soil nails. We assisted LAN in developing the cost estimates for soil nails, slope paving, replace the slide material with stabilized fill, and to reuse and reinforce the slide material using geogrids. After analysis of all the options, we selected a repair based on reinforcing the slope with geogrids. HVJ developed the geogrid schedule; assisted LAN in preparing PS&E documents and specifications; and provided construction phase services, completing construction on schedule without difficulties.