A Guide to Safe Field Operations
U.S. Geological Survey Open-File Report 95-777

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Surface-Water Activities

Procedures and guidelines to avoid personal injury during wading measurements, bridge measurements, cableway measurements, boat measurements, measurements under ice cover, indirect flood discharge, maintenance of streamgages, and scuba diving are discussed in this section.

Wading Measurement

Discharge measurements using current meters are best made by wading. Wading measurements have a distinct advantage over measurements made from bridges, boats, or cableways in that it is usually possible to select the best available cross sections for the measurement. However, wading measurements represent one of the greatest potential sources of accidents in the Division. The wide range of conditions, combined with the relatively large number of measurements made by wading, creates the high potential for accidents. Constant awareness of wading dangers and weather conditions needs to be maintained to avoid accidents and potential injury. Listed below are some safety guidelines that need to be observed:

Bridge Measurements

Bridges are often used for making discharge measurements of streams that cannot be waded. Equipment needed in making bridge measurements differs from that used in wading measurements in that a portable metal crane is often used to mount a reel and suspend the meter, sounding weights, and cable over the bridge. Power equipment, which may be mounted on vehicles, is used for large rivers. Some bridges are not adaptable for cranes, and bridge boards must be used. On some foot bridges a special rod or handline is used.

Bridges are inherently dangerous because of vehicular traffic. The following safety procedures are recommended when making discharge measurements from a bridge:

Cableway Measurements

Cableways have been used for many decades by the Division in making discharge measurements. Cableways provide a track for the operation of a cable car from which the hydrographer makes a current-meter measurement. Cable cars also support the sounding reel and other necessary equipment. Cable cars are moved from one point to another on the cableway by means of cable-car pullers. Power-operated cable cars are available for extremely long spans.

Properly constructed and maintained cableways and properly operated cable cars are dependable and convenient. The following safety procedures are recommended to be followed when making cableway measurements:

Boat Measurements

Measurements made from boats require special equipment not used for other types of measurements. Generally, a cross-piece reaching across the boat is clamped to the sides of the boat and a boom attached to the center of the cross-piece extends out over the bow. The cross-piece is equipped with a guide sheave and clamp arrangement at each end, to attach the boat to the tag line and make it possible to slide the boat along the tag line from one station to the next. Power-operated equipment, which may be mounded on boats, is used for large rivers. The following safety procedures are necessary to prevent accidents or damage to equipment:

The essence of boating safety is keeping out of trouble rather than getting out of trouble after you get into it. The operator of the boat is responsible for knowing all equipment requirements and safety procedures for the craft. Employees are referred to U.S. Coast Guard Auxiliary (1986) for detailed boating information and regulations. Some general boating safety guidelines are:

Discharge Measurements Under Ice Cover

Current-meter measurements, made under ice cover require special equipment for cutting holes in the ice through which to suspend the meter. Holes of 6-inch diameter are most often cut with a power ice drill. Where impossible to use an ice drill, ice chisels are used to chop the holes. The most dangerous task of ice measurements is determining whether or not the ice is strong enough to support the hydrographer and the equipment. If the ice thickness is questionable for safety, no measurement will be made. Discharge measurements under ice cover are usually made under conditions that range from uncomfortable to severe.

A few reminders that might prevent accidents or damage to equipment are:

Indirect Flood Discharge Measurements

The measurement of flood discharges at field sites may be impossible or impractical, due to road conditions or high streamwater velocities. Fortunately, technology exists that enables hydrologists to measure peak flood discharges after the fact by indirect methods. These methods require the field surveying of water-surface profiles, from flagged high-water marks, and the geometry of the stream channel which carried the flood.

The field surveying is performed in a timely manner after the flood peak occurrence, and is performed under commonly difficult field conditions. The high-water marks are generally flagged within 24 hours of the crest, when seed lines are fresh. Field conditions can be hazardous and require extreme caution by field people. These conditions can include dead and decaying animals, broken sewer lines, foul humid air, downed power lines and trees, and snakes up in trees. Additional information can be found in Benson and Dalrymple (1967) or Rantz and others (1982).


Some WRD programs require that biological information on fish be collected to help assess the water quality of a stream. A technique which is commonly used by biologists to collect fish is electrofishing (EF). In this method, an electrical charge in the water stuns the fish so they can be captured and examined.

Electrofishing is an inherently hazardous activity in which safety is the primary concern. The electrical energy used in EF is sufficient to cause electrocution. To protect the safety of the employees involved in EF, the WRD has issued Memorandum 93.19 ("Requirements for WRD Personnel Performing Electrofishing") that presents policy on training, immunization, and procedures and responsibilities.

Construction, Repair, and Maintenance of Streamgaging Stations

There are many hazards associated with the construction and repair of streamgaging stations. By using common sense and by taking proper precautions, most accidents can be prevented. This can be accomplished by reading instructions and asking questions related to the job, including planning of work, research for information in field folders, and reading previous field notes of adjacent sites. The type of structure or repair that is needed should be determined and, if necessary, detailed plans for the construction or repair of gages must be prepared. Construction permits and inspections may be required and you must consult your local building department for up-to-date information. On occasion, contractors may be required to complete the work.

The maintenance of gages needs to be conducted on a regular basis. If maintenance is scheduled and carried out properly, it will result in fewer safety risks and less costly repairs. All manufacturer's recommendations must be closely followed when servicing or trouble-shooting equipment. Instructions associated with equipment operation in the field must be filed in the field folder. All specific information related to the maintenance of the gage must be available prior to technician's departure to the field. The following safety procedures relating to gaging stations are recommended.

Gage Inspection and Records Removal

It is required to visit the streamgaging stations at scheduled intervals for record removal and discharge measurement. The field folders provide the specific pertinent information associated with each station. All instructions and notes that are related to the particular station must be left in the field folder and transferred from year to year. Hazards must be well documented in a log and made available to anyone that visits the station.

Upon arrival at the station, one should clear away the brush, vegetation, or debris from around the structure, keeping a sharp eye for poisonous snakes before beginning the inspection and records removal. Open the gage house door carefully and look for unusual conditions that might exist inside. If the station was vandalized, equipment in the gage house may be left in a dangerous condition. Also, look for insects that could be a hazard to you during your work inside the gage house. Brace the door or lid of the shelter so it will not close by strong wind while you are working inside of the gage house. In gage houses with wells or equipped with monitoring manometers, check if there is a supply of oxygen and maintain proper ventilation. The house door should be kept open for at least a few minutes before servicing the equipment. This is because mercury vapor may be present even in ventilated houses.

Do not work inside a gage house with the door closed. Gage house doors are often targets for gun practice. People may not be aware that someone may be behind the closed door.

Share information on any hazard that you discover by leaving a note in the field folder and inside the gage house, and list all hazards on a hazard elimination log. Any problem that field personnel encounter in the field must be corrected immediately, if possible. A problem left unresolved could become a serious hazard.

Keep the inside of the gage house clean.

Scuba Diving

Occasionally it is necessary for Survey personnel to conduct scuba diving activities in support of data collection and environmental studies. Scuba diving is a potentially high risk operation and therefore requires special control and procedures to protect employees from accidents. Compliance with OSHA regulations is required as specified for scientific diving. No scuba operations are permitted without meeting every requirement of the OSHA regulations.

Safety considerations include:

Previous--Specific Procedures and Safety Issues
Next--Ground-Water Activities
A Guide to Safe Field Operations
U.S. Geological Survey Open-File Report 95-777

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