In Reply Refer To:                                                December 20, 2004 
Mail Stop 415

In Reply Refer To:
Mail Stop 415


SUBJECT: Requirements for coating lead sounding weights, cleaning and testing potential lead-contaminated areas, and monitoring lead in blood


Testing of Columbus-type sounding weights and of surfaces in contact with or near them has indicated that the weights may be a source of lead contamination. Hazards associated with this contamination were described in a USGS Safety Memorandum (URL: issued on January 17, 2004, by USGS Safety and Environmental Branch (SEMB).

In response to the SEMB safety memorandum, the Office of Surface Water (OSW) tasked the Hydrologic Instrumentation Facility (HIF) with investigating lead weight coatings that could be used to abate the contamination hazards arising from continued use of the Columbus weights. In addition, SEMB prepared technical guidance describing recommended procedures for cleaning contaminated areas and for disposing of the resulting refuse.

The purpose of this memo is to (1) describe new requirements for the coating of Columbus-type lead sounding weights, (2) transmit SEMB guidance for the clean-up and testing of surfaces that may have been contaminated by lead during the storage or transportation of the weights, and (3) describe requirements for testing employee blood lead-levels.

Powder coating of sounding weights

Based on tests conducted by the HIF and the recommendation of the SEMB, OSW has concluded that encasing Columbus-type lead weights in polyester powder will effectively prevent the weights from shedding lead dust or debris. Powder coating is a process by which a polyester powder is electrostatically sprayed and heat cured onto an item to create a tough outer coating. Test applications of the coatings to the Columbus weights have shown that they effectively adhered to the surface of the weights. Hydraulic tests conducted by the HIF have demonstrated that the coatings on the weights do not result in changes in profile, thickness, or roughness sufficient to alter drag or velocity fields associated with use of the weights. The coatings are expected to perform well for many years.

Therefore, in order to eliminate lead weights as a contamination source, districts are required to have all actively used Columbus-type sounding weights powder coated Powder coating services are widely available throughout the country and are often associated with automobile repair/refurbishing and metal-works industries. HIF has had good experience with both the “Tiger Drylac Series 49 Exterior” and “Rohm and Hass Company 20-2078HY” coatings, but most powder coatings will produce acceptable results if the weight is thoroughly washed, degreased, and etched before coating. The coatings are generally applied to result in a thickness of 2.5 to 3.5 mils, an adhesion of 5B (ASTM D3359), and a minimum hardness of 2M (ASTM B3363). Coatings should be colored “safety yellow.” The Regional Hydrologist, in consultation with the regional safety offices, will establish deadlines for this work, but SEMB and OSW suggest that it be completed by December 2005.

The cost of coating a 75 pound weight is typically about $50. Districts that cannot locate a powder-coating provider can arrange to have their weights coated by the HIF. Alternatively, HIF now stocks only the powder-coated weights for sale (URL:

Weights that are not actively used within a district might be useful to other districts. Lead has value and weights that are not expected to be actively used should be retired and deposited with a lead recycler or returned to the HIF. Local lead recyclers are available in many communities. The Institute of Scrap Recycling Industries (202-737-1770) can assist you with locating a lead recycling firm in your area.

Testing and cleaning of lead-contaminated areas

Areas where lead sounding weights are stored (vehicles, lockers, warehouse shelves, and floors) may exhibit unacceptably high levels of lead contamination. These surfaces should be tested and cleaned of lead contamination. The attached Lead Clean-up Plan, provided by SEMB, describes the clean-up and testing process and identifies sources for testing kits and laboratory services. Once a contaminated surface has been cleaned, a test should be conducted to verify that the surface is no longer contaminated. Please contact your Regional Safety Officer or the Bureau Industrial Hygienist for advice or if you have questions.

Testing employee blood-lead-levels

Heath screening and blood lead tests conducted by Water Resources Discipline cost centers have not, to date, identified any persons experiencing high-levels of lead in their blood, and we have no reason to believe that exposure to lead weights has caused elevated concentrations in blood . However, concerned employees are entitled to have their blood tested for lead at cost center expense. Blood testing can be achieved through existing arrangements with contract occupational health units or local doctors and health clinics. The venous blood sample that is collected should be shipped to a laboratory participating in the Center for Disease Control (CDC) National Center for Environmental Health (NCEH) Blood Lead Level Reference System (BLLRS). A list of OSHA approved laboratories is posted on the OSHA home page (URL: In addition, cost centers should include testing for lead in blood as a routine part of their medical monitoring program. Please contact your Regional Safety Officer or the Bureau Industrial Hygienist (currently Cynthia Duffield) for advice or if you have questions.


Stephen F. Blanchard /s/
Chief, Office of Surface Water