Air-gap disclaimer:
Estimation of "air gap" (also commonly referred to as
"air draft" or "clearance") is provided as the
difference in low-steel elevation obtained from US Army Corps of
Engineers navigation charts and stream stage (elevation) obtained
either directly, or indirectly, from USGS streamflow-gaging stations.
This air-gap data is provided as a planning tool only and users of
this data must exercise due diligence while underway and assume full
responsibility for ensuring safe transit through all bridge openings.
Although USGS intends to make this data available through the USGS
server 24 hours a day, 7 days a week, timely delivery of data and
products from this server through the Internet is not guaranteed. The
USGS provides this data "as-is" for a quick reference,
planning tool but assumes no legal liability or responsibility
resulting from the use of this information.