sheltered side. A possible explanation for this difference is that the 

 toxic chemicals were removed most rapidly from the side of the panels 

 exposed to the current. In the absence of the toxic chemicals, the 

 fouling organisms might thrive better in the quieter water on the side 

 protected from the current. 



The panels protected by a layer of rubber or epoxy compound contain- 

 ing TBTO at the 1 00-ml-per-liter level had less fouling than the untreated 

 control panels but more fouling than the panels made from the aggregate 

 impregnated with mixtures of creosote and TBTO. There was about the 

 same amount of fouling on the panels made from aggregates impregnated 

 with copper naphthenate mixture as there was on the control panels. 



Near-Surface Exposure at Guantanamo Bay. A few panels of experi- 

 mental antifouling concrete were exposed for 1 year near the seawater 

 intake of the desalination plant at Guantanamo Bay. Panels made from 

 aggregates impregnated with a mixture of creosote containing TBTO at the 

 1 00-ml-per-liter level (System 7) were essentially free of fouling 

 organisms and the untreated control panels were covered by a heavy 

 growth of fouling organisms. 



Near-Surface Exposure at Point Mugu. Concrete panels made from 

 aggregates impregnated with numerous toxic mixtures (Systems 1 through 6 

 and 13) were exposed near the surface at Point Mugu, California. Approxi- 

 mately 10 months after the first of the panels had been placed in the 

 water, a storm destroyed the exposure rack, and all of the panels were 

 lost. The only data on the panels was that obtained during inspections 

 made after the panels had been in the water 3 to 8 months. In 3 months 

 the control panels were covered by a light growth of algae, calcareous 

 tubeworms , branching bryozoa, and hydroids , but no mussels or barnacles. 

 In 8 months the surfaces of the control panels and the surfaces of the 

 panels containing a quaternary ammonium compound were completely covered 

 with a dense growth of tubeworms, encrusting and branching bryozoa, 

 mussels, and barnacles. In 8 months concrete panels made with aggregate 

 impregnated with 100% TBTO were covered by a light growth of bryozoa, 

 algae, hydroids and a few barnacles. In 3 months, concrete panels made 

 from an aggregate which was impregnated with 100% creosote and no other 

 toxic chemical were already covered by a light growth of algae and 

 numerous barnacles. In 8 months panels made from an aggregate which was 

 impregnated with a creosote mixture containing TBTO at the 25% level 

 (System 5) were free of fouling except for an occasional small barnacle. 

 Those made with a mixture of creosote, copper naphthenate, and TBTO at 

 the 1 00-ml-per-liter level (System 13) were covered by only a scanty 

 growth of brown algae. 



Near-Surface Exposure at Port Hueneme. The greatest number of 

 tests and the longest tests were conducted from the materials test dock 

 at Port Hueneme. Concrete panels containing no toxic chemicals were 

 heavily covered by a dense growth of fouling organisms of all types 

 (Figures 5 and 6) . The panels impregnated with mixtures of creosote and 

 other toxic chemicals, including TBTO at the 250-ml-per-liter level 

 (Systems 5 and 8) , were sometimes temporarily covered by light growth of 



12 



