The North Branch Otter Creek Bridge in Greenwood County, Kansas, is a well-known, triple-arch stone bridge listed on the National Register of Historical Places. It was built by pioneer bridge builder Walter Sharp, as shown by the plaque. Walter Sharp is renowned for being the foremost builder of the famous Cowley County stone arch bridges.
When the old Otter Creek Bridge was replaced with a modern structure, the old bridge was preserved at the insistence of the local people, and left for pedestrians to walk on and passersby to admire.
The Otter Creek Bridge is one of the few remaining bridges Walter Sharp built employing a series of highly rounded arches. Where a large waterway was critical, Walter Sharp seems to have favored this method of constructing a series of smaller, rounded arches on thin piers instead of one or several long, flat arches. The famous Dunkard Mill Bridge over the Walnut in Cowley outside of Arkansas City was an example of this kind of construction. Greenwood’s double-arch Fall River stone bridge shows this design as well.
The Otter Creek bridge is unusual inasmuch as it features a stone arch facing, while the middle of the arch is actually concrete. The Otter Creek Bridge, incidentally, was actually a replacement for a previous stone arch bridge at the same site which failed not too long after construction.
When the bridge was preserved, it was already deteriorating. Undermining of the piers was a major issue with this bridge even then. Now, over a decade later, the deterioration has reached significant levels. All of the piers are undermined to varying degrees and masonry is dropping out in places.
One of the abutments and the approach leading to it have been scoured out and part of the guard rail has toppled off and is hanging.
The center arch is missing stones at the bottom.
Undermining of the supports of a stone arch bridge is arguably the single most common cause of stone arch bridge failure. Since stone arch bridges were frequently built on shallow foundations, they are rather easily undermined by the water action. Incidentally, an old photograph of the Otter Creek Bridge from the 1920s reveals a rather startling fact: The bridge rests on grassy ground, rather than over a large stream like we see today. Apparently, Otter Creek has changed its habits over the last hundred or so years, which is probably why the foundations have been undermined. Nowadays, to prevent undermining, modern bridges have there piers sunk deep into the ground and even beyond bedrock, where applicable. As for stone arch bridges with shallow foundations, the addition of concrete aprons is usually a beneficial idea to protect the foundations where undermining is occurring.