(All pictures can be viewed at original resolution by clicking on each.)
|Most sampling locations within Missouri can
be accessed either by wading in the stream or suspending a sampler from
a bridge. However, the large rivers (Mississippi and Missouri) pose more
challenging problems. Working from bridges over large rivers is both a
safety and quality issue. High traffic and often-times narrow bridges
make the one to two hour sampling process very dangerous. From a
quality standpoint, these bridges can be a source of sample
contamination resulting from automobile and truck fumes, dust and dirt
being suspended in the air, and bird dung.
The USGS sampling boat has been specifically designed for obtaining water, sediment, and bottom material samples from a bridge crane mounted on a davet plate welded to the floor on the bow of the boat. The foredeck is large enough to support two technicians, several hundred pounds of equipment, and the bridge crane with sounding weights. The crane can be seen in the above and right-hand pictures. During a sampling event, the boat's crew includes a certified operator, and two technicians to collect the samples.
Towing the boat from site to site has been a challenge. To accomplish this, the USGS has invested in a dual rear wheel, diesel powered, four-wheel drive, 1-ton pickup truck to pull the boat. This rig has allowed us to maintain safe speed limits on the major interstates and highways, and has helped with crossing the many hills and ridge-lines throughout the Ozarks.
Sample collection by boat on the large rivers has proven to be both safe and clean. A typical sample at base stage can be collected in about an hour. This is a significant improvement over the old bridge-deck method which took anywhere from 2 to 3 hours depending on traffic and weather conditions. A representative depth-integrated Equal Discharge Increment (EDI) method sample can be collected at the approximate locations of the former bridge-deck sampling locations. Therefore, data integrity has been maintained for the entire historic database for each site.
Safety is first and foremost when it comes to operating a work boat on the large rivers. At base flow, river currents oftentimes exceed 3.5 feet per second and during flood stage, greater than 7 feet per second. With such a torrent of flow, accidents can happen very fast. Therefore, the boat is equipped with redundant four cycle outboard engines, two personal floatation devices per crew member, and an auto-inflate four-man life raft. During winter operation, all personnel are required to wear floatation exposure suits. The boat is also equipped with a marine band radio, depth gage, and radar.
The boat is currently used on the Mississippi and Missouri Rivers on a monthly basis. The primary program that supports the operation and maintenance of this craft is the federally funded National Stream Quality Accounting Network. Approximately 15 samples at each of three sites are collected annually. About 100 hours of operation time is logged on the engines each year.
U.S. Department of the Interior, U.S. Geological Survey
Maintainer: Rita Choate, Webmaster
Updated: August 27, 2003
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