Driveway and Walkway Bridges

A bridge is one of those things that are often taken for granted until you don’t have one, especially if you live on a rural property and there’s a creek between your house and the county road. DSLD designs and builds driveway and walkway bridges in a variety of settings.
While most walk bridges are simple structures with little environmental impact, some driveway bridge builds require considerable planning, especially when it is located over a waterway that is under the jurisdiction of several different government agencies. It doesn’t have to be a significant river for several governing bodies to claim control over the rights to build any kind of structure near the waterway. There are agencies that regulate flood control, water quality, fish habitat, etc., and each one of these agency’s regulations must be satisfied before the project can proceed.

DSLD can help you navigate the river!

DSLD can create a riparian landscape plan, file an application with the Department of Fish and Wildlife, deal with an agency called the National Marine Fisheries Service, submit a fish passage plan, get the approval of the Department of Forestry, and deal with the County Planning and Development Department. We can certify a base flood elevation and our engineers can draw up the bridge plans as required by the County.
The local Fire District may also be involved by requiring that the bridge hold a loaded fire truck (weighing 50,000 lbs.), and that the approach angles to the bridge be within specifications, and that a turnaround be provided on the other side of the bridge.
Another government agency that may need to be contacted prior to building is FEMA to insure the bridge is not in a flood plain. DSLD will address concerns ranging from impact on water quality, on fish migration, on flood mitigation and on vegetation.
In the unlikely event that a government agency is not forth coming with specifications for elevation and span on your bridge project, (it happens) we will make sure the bridge is above the 100-year high water mark. A bridge that is built too low, or with a span too narrow, can cause a significant choke point during those winter storms or spring thaws that bring streams out of their banks. Debris can hang-up on a bridge, which can catch more debris and eventually dam up the stream, causing a great deal more damage than many people can imagine.

Strong Foundations

Once all the concerned government agencies, community input, surveying and engineering aspects are completed, the actual construction of the bridge can begin. Just like with house construction, the sub-base for the foundation must be shaped and compacted first. For this bridge, which was designed with I-beams, the two foundation pieces that support the ends of the beams are called abutments.
Specifications may include pouring each of the abutments in two parts on top of thoroughly compacted sub-bases topped with 3/4 minus crushed rock. Using the surveyor’s base flood-elevation mark to set the top of the footing portion of the abutment, we can build the forms to make the footing 3 feet thick and 2 feet high, which will make it top out at 1 foot above the base flood elevation. We may also form 2-foot wing walls at 45 degrees on each end of the abutment to help transition to finish grade.
You cannot place too much emphasis on the importance of having adequate foundation members for optimum long-term performance, particularly resistance to flooding and scour conditions. The abutments are susceptible to overturning under severe flooding and scour conditions, and may require either deep piling or adequate spread footings to properly support them.

Bridges

by | Feb 5, 2020

A simple summer creek can appear harmless enough and you may be tempted to span it with a fallen log or simple bridge on grade, however after a large rain that spanning structure may become a floating projectile to your downstream neighbors or act as a plug in a downstream culvert. Put DSLD on your team before you undertake your bridge project!

PLEASE CONTACT US

With any additional questions, please feel free to contact us by phone (205-437-1012) or email dsldsocialmedia@gmail.com