Care of Stone Arch Bridges With Insufficient Waterway

Debris Blocking an Arch

Some historic stone arch bridges and stone arch culverts were built with waterway that is simply insufficient. Some stone arch bridges have a high enough “hump” over the bridge proper so that, during floods, water actually flows over the road around the bridge rather than over the bridge proper, thereby relieving the structure of some pressure. While this is not, perhaps, an ideal situation, it does tend to be easier on the bridge.

Polecat Creek Bridge
The Polecat Creek Bridge in Butler County, Kansas, rises considerably above the main road level, with the result that, during all but the most severe flooding, water flows around the bridge as opposed to over it when the water is high.

Some stone arch bridges simply are too small, with the result that they tend to become submerged rather frequently, and periodically damaged. While the worst offenders in this regard are usually long gone, surviving stone arch bridges that are too small often need some special attention in order to remain serviceable.

Maintenance Items for Constricted Arch Bridges

For a stone arch bridge that is generally sufficient save during massive floods, the best method of keeping the bridge from being damaged is to keep it maintained. For a mortared structure, the mortar joints should be kept in reasonably good condition in order to keep stones tight. Loose stones are rather vulnerable to being knocked out during flooding. Other high-maintenance items are the spandrel walls, approaches and wingwalls. All of these retaining walls are vulnerable to washouts, usually leading to loss of roadway and even damage to the main portion of the bridge. Bulging walls are the first sign of a problem, but can often be rectified with tie-rods. Signs of scour, of course, need to be dealt with promptly. Significant debris accumulation against a bridge also needs to be removed as soon as possible.

Debris Blocking an Arch
A rather extreme case of debris buildup on a stone arch bridge. The debris was removed sometime after this picture was taken. This stone arch bridge, spanning Gillion Creek in Butler County, Kansas, is typical of the county’s earliest stone arch bridges, inasmuch as the span is rather small for the stream being crossed, hence the debris buildup. This waterway problem caused some difficulties early on in Butler County’s earliest stone arch bridges, with the result that the county started building their stone arch bridges with larger spans and added extra spans on some of the county’s earlier stone bridges. (See below.)

Preventing Damage

Capping retaining walls of any sort with concrete tends to help stabilize these sections of a stone arch bridge. Scour is an especial threat for a stone arch bridge that is too small, and scour aprons often end up being a necessity. One excellent solution for bridges that go underwater periodically is to replace the original fill with concrete and/or pour a concrete surface on top of the whole bridge. This solid concrete barrier prevents the roadway from being washed out, and provides a solid weight over the arch, which helps stabilize it during flooding.

115th Whitewater River Bridge
This small stone arch culvert spans the mighty Whitewater River in Butler County, Kansas. A concrete surface has been poured atop this bridge, allowing it to act well as the low-water bridge it actually is. The span is a mere 16 feet, and is much too small for the river.

Increasing Waterway

Sometimes if the waterway is too constricted, it may be necessary to add an additional span of some sort to a bridge. While not a very historic treatment, adding an additional span to a stone arch bridge does not need to look glaringly out of place. A small culvert or other span can often be placed somewhere in the approach as opposed to directly against the arch of the bridge, thereby retaining the historic appearance of the main portion of the bridge.

NE 110th Street Double Arch Walnut River bridge
This double-arch stone bridge in northern Butler County, Kansas, spans the Walnut River near Cassoday. This bridge actually was once a single-arch bridge, and the waterway was terribly insufficient. A small span was tacked onto this bridge some time shortly after it was completed in order to rectify the waterway difficulty, but this still was not enough. At last, only four years after the bridge was built, Butler County had an additional full-sized arch added, resulting in the double-arch bridge we see today.

Replacing Stones Knocked Loose

Sometimes, despite our best efforts, a stone arch bridge is damaged during flooding. Usually, this damage seems to consist of partial failure of a spandrel wall, and extensive loss of any stone curbing. Often, after the flood, the missing stones can be fished out of the water and restacked. However, where stones are missing new ones can be cut to fit, if care is taken to size them correctly.

Polecat Creek Bridge
As it happens, some of the stones on the Polecat Creek Bridge in Butler County, Kansas, are not original, especially in the curbing. This bridge was damaged over the years from impacts and flooding, and, while many of the original stones were recovered and used, some had simply gone missing. However, new ones were cut and, while not an exact original fix, this repair tastefully matches the character of the original work on the bridge. The Polecat Creek Bridge is on the National Register of Historic Places.

Historic photos of the bridge before the damage can be invaluable for rebuilding the bridge as authentically as possible. However, for stone arch bridges that are not considered particularly historic, concrete is often used to rebuild missing sections of stonework.