A second labor dispute halted work on the bridge when 200 members of Sand and Gravel Workers Union Local 22075 went out on strike over a refusal by the Smoot Sand and Gravel Corporation to adopt the closed shop. The strike, which began on August 14, immediately halted concrete work not only on the new Sousa Bridge but on more than 20 building and transportation infrastructure projects, and idled more than 5,000 workers. Howard T. Colvin, a United States Department of Labor conciliator, was called in to help end the dispute. Initially, Colvin expressed optimism that the strike could be settled swiftly. But the union rejected a potential settlement on August 23 because it lacked specific wage and hour agreements. On August 25, Representative William Alvin Pittenger (R-Minnesota) asked the Army Corps of Engineers to break the strike and supply sand and gravel itself. The Army refused. On August 28, the federal government intervened in the strike. Federal Works Agency Administrator John M. Carmody questioned why the single source was used to supply all the sand and gravel to so much projects, and threatened to find a new supplier if a settlement was not forthcoming. John R. Steelman, head of the Federal Mediation and Conciliation Service, announced he was personally intervening in the negotiations to bring an end to the strike. Meanwhile, Colvin proposed a strike settlement which was immediately accepted by the union and rejected by the company. Carmody and Steelman's intervention appeared to work. Progress in strike talks was announced on August 30, and on September 5 the company and union ended the strike after agreeing to Colvin's terms.