The Mystery Bridge under 600 North

By Michael R. Polk, Aspen Ridge Consultants

The intersection of 600 North and Pugsley Street in Salt Lake City today marks the boundary between the posh Marmalade District and the industrial park surrounding the train tracks. Thousands of people drive over this section of road every day to get to and from the I-15 freeway, never realizing what lies beneath.

In July 1998, Wasatch Constructors, Inc. (Wasatch) of Salt Lake City were working on the I-15 reconstruction project for Utah Department of Transportation’s (UDOT). Specifically, they were working near what was once the end of the 600 North eastbound off-ramp from I-15 that had been removed in 1997. Underneath 600 North at the intersection with Pugsley Street they hit large wooden planks four feet under the modern ground surface. Wooden planks, deep under a major urban street? They called in the experts.

Time to call in the archaeologists!

UDOT, being responsible or the protection of cultural resources in their right-of-ways and on projects that they carry out under Section 106 of the National Historic Preservation Act of 1966 (NHPA) among other laws, requested that Sagebrush Consultants, L.L.C. (Sagebrush) (now Commonwealth Heritage Group) come out to inspect the discovery. The archaeologists arrived on the scene and began their work.

The first thing to do was measure and describe the feature, often just a visual inspection will give an archaeologist clues about when a feature was built and what for. The structure measured 19 ft long by about 10 ft wide and was made of timbers, rough-cut lumber and machine cut nails. The planks measured 2 in by 12 in and 2 in by 10 in in size. It also included five large diameter logs underneath the lumber.

The logs rested on a wet surface, perhaps a historic seep or spring, which was in the path of the planned roadway for 600 North. Historic engineers nailed the long, wooden planks to these logs as decking, two layers deep.

Archaeologists cleared off debris and found this structure. They measured and described it – but what was it?

The machine cut nails contained a clue about when the structure was created. They pre-date the late 1890s, which if you remember from last week’s post, Trash Talk, is an important date associated with the nearby railroad. Archaeologists had a date, but they couldn’t figure out exactly what this structure was used for. Because of the small size and nature of the structure, it is not easy to term the feature as either a bridge or culvert.

Portions of the deck of the structure appear to have been patched since it was originally constructed. These “patched” areas had well fitted boards showing that the structure was constructed by knowledgeable workers. A worn running surface showing wheel rut or other damage was not observable. Also, at the northeast corner of the bridge, the planks appear to have been severely compressed by a very heavy overlying weight. Archaeologists could tell that the effects of compression occurred after the structure was buried by street fill material. The planks had been compressed and partially wrapped over the underlying log supports, most likely due to the weight of the former off-ramp from the I-15 freeway.

Putting the Planks in Perspective
View of double plank bridge surface and interface with underlying bearing logs.

The nature of the structure and its method of construction (rough-cut milled lumber, machine cut nails) are consistent with European American building practices of the latter half of the 19th Century. Salt Lake City, during the 1870s and into the 1880s, was an expanding city, especially into areas south and west of Temple Square where the business district became established. Unlike the Capitol Hill Neighborhood to the east with mostly wealthy residents, this area was relatively rural with many orchards and open fields. It may have been the rural character and light traffic along roads in the project area during the 1870s that led to the construction of only a small structure along 6th North to span a wet area.

We will never really know when the bridge was constructed, whether it was a local fix to a local problem or a city-sponsored effort to cross a wet spot. But we do know that it was built in from 1870 to about 1885, and witnessed an amazing growth of Salt Lake City’s industrial infrastructure and a shift from an agricultural community to a bustling commercial center before being covered by the trappings of a modern city.

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