WASHINGTON COUNTY HISTORICAL SOCIETY (Washington County, Utah)
SHEM DAM AND THE 1938 FLOOD
on the Santa Clara River/Creek
HISTORY
HAER No. UT-96, Pages 9-11Significant alterations were made to Shem Dam on two occasions to repair damage caused by flooding. In early March 1938, heavy rains caused the Santa Clara River to swell drastically, raising concerns that the dam would be swept away.16 The dam proper was not damaged, but the lower parts of the spillway—the churning bowl, the secondary crest, the wing walls, and the apron—were damaged significantly. Photographs of the damage taken by Winsor later that year show that the flow over the spillway had undercut these features, causing them to subside, crack, and fall apart (see Appendix B, Figures 18–21). In notes on the photographs, Winsor attributed the damage to a shortcoming in the construction. The secondary crest had been built on top of loose gravel, due to the fact that the C.C.C. camp could not procure a pump with sufficient capacity to remove water during construction. Therefore, the structure was not carried down to sufficient depth to make it secure against erosive action of heavy flood.17 The CCC crew apparently had no such difficulty when raising the rest of the dam, but this part of the spillway was the very first part of the dam to be built (see Part II below), so perhaps the lack of a pump was resolved before construction of the dam proper began. By December 1938, local business interests, including the irrigation company that relied on the diversion at the dam, were pressing the Forest Service, the Soil Conservation Service, and the CCC to make the needed repairs.18 Winsor, who by 1938 was working for the U.S. Biological Survey and based in Salt Lake City,19 was evidently still available to design and oversee a CCC project for the Forest Service, although the only record of his role in the repairs are photographs of the dam he took at the time.20 The St. George CCC camp and Company 961 no longer existed, but Company 585, based at Camp SCS-7 in Leeds, Utah, about 15 miles north of St. George, was active in the area and loaned the Forest Service a crew of about 30 men for the repairs, which were made in May 1939. 21 The repairs consisted of rebuilding the churning bowl, the secondary crest, the wing walls, and the apron, providing all with a solid foundation, then adding a row of “breakers” along the downstream edge of the apron to slow the flow off the apron and prevent it from being undercut. The breakers were low, freestanding concrete piers, poured in place and aligned in a row, and spaced about 4' apart. Each breaker was diamond-shaped in plan, with the long axis of the diamond oriented parallel to the flow; the top of each breaker stood about 2' above the streambed and measured about 15" × 18" in plan. The completed repairs to the spillway were documented by Winsor in photographs in June 1939 (see Appendix B, Figures 22 and 23).22 The CCC crew from the Leeds camp left informal inscriptions in wet concrete on the upper surface of the repaired southwest wing wall, including their company number and a few names and dates, as documented in the fieldwork for the current HAER documentation (see Part II below)
HAER No. UT-96, Page 30
The damage sustained by the dam in the 1938 flood was completely repaired the following year, returning the structure to its original 1935 appearance except for the addition of a line of “breakers” (low, freestanding concrete piers) along the downstream edge of the spillway apron.
PHOTOS
WCHS-03916 Shem Dam following the spring 1938 flood that damaged the lower portion of the spillway
Other WCHS photos:
WCHS-03917 Photo of the damaged lower portion of the Shem Dam spillway at the start of repairs in 1938
WCHS-03918 Photo of the damaged lower portion of the Shem Dam spillway at the start of repairs in 1938
WCHS-03919 Photo of the damaged southwest wing wall at Shem Dam in 1938
WCHS-03920 Photo of the Shem Dam spillway after the completion of repairs in 1939
WCHS-03921 Photo of the Shem Dam spillway after the completion of repairs in 1939
REFERENCES
Historic American Engineering Record, Shem Dam (Winsor Dam), HAER No. UT-96Prepared by Scott O'Mack, William Self Associates, Inc.,
for the USDA Natural Resources Conservation Service (NRCS)
March 2016, 96 Pages (see pp. 9-11, 30)
[Large file, so this may take a while to load]
Flood Conditions Exist as Rain Continues
Washington County News, March 3, 1938
C. of C. Helps Save Dam Above Indian Reservation
Washington County News, December 29, 1938
Leeds CCC Camp
Washington County News, May 5, 1939
Baldridge, “Nine Years of Achievement: The Civilian Conservation Corps in Utah,” 373, gives the camp and company numbers for the Leeds camp in the thirteenth enrollment period, April 1–September 30, 1939