Set no. 2, TBTO Alone and TBTO/Creosote Mixture. In this set, TBTO 
alone did not perform as well as the TBTO/creosote mixture (see Table 4). 
Cylinders prepared with TBTO alone accumulated 83% as much biofouling as 
the control after 596 days at Port Hueneme, compared with 52% for the 
TBTO/creosote mixture (Figure 2). At Key Biscayne, biofouling was 96% 
of the control for TBTO alone, and 59% for TBTO/creosote after 524 days 
(Figure 3). 
Set no. 3, TBTO Alone, Cuprous Oxide Alone, and TBTO/Cuprous Oxide 
Mixture. TBTO was employed at half the concentration used in set no. 2, 
both alone and combined with cuprous oxide. Cuprous oxide alone was 
also evaluated and found to have no effect at the concentration used. 
At Port Hueneme the weight increases after 153 days due to biofouling of 
members of this set compared to the control were: TBTO alone, 81%; 
TBTO/Cu,0, 69%, and Cu,0 only, 93% (Figure 4). Data from Key Biscayne 
after 283 days showed the same trend: TBTO alone, 92%, TBTO/Cu,0, Iib5 
and Cu,0 only, 116% (Figure 5). The specimens in this set exposed at 
Key West have not shown any signs of attack by pholads. The cylinders 
are suspended a few feet from a 6/-year-old concrete pier which exhibits 
evidence of pholad activity. 
Set no. 4, Methoxychlor Alone, Methoxychlor/Cuprous Oxide/TPTH 
Mixture, and Organotin Coating. This set was prepared to investigate 
the antifouling properties of two basic toxicants: methoxychlor and a 
proprietary organotin coating. Methoxychlor was employed alone and in 
combination with TPTH and Cu,0. At Port Hueneme, the weight increase of 
members of this set versus an untreated control after 153 days was: 
methoxychlor alone, 124%, methoxychlor with TPTH and Cu,0, 65%, and 
organotin coating, 42% (Figure 3). At Key Biscayne, the results for 
replicates of this set after 139 days were: methoxychlor, 99%, meth- 
oxychlor with TPTH and cu,0, 90%, and organotin coating, 66% (Figure 6). 
Set no. 5, Organotin-Impregnated Rubber Cover. The cylinders 
covered with the organotin-impregnated rubber accumulated an average of 
15.8 gm of biofouling after 60 days in Port Hueneme. No data are avail- 
able at this time on the replicates exposed in Key Biscayne. 
Compressive Strength 
Various solvents for washing aggregate impregnated with TBTO/creosote 
(60/40) were tested. The prepared specimens had 7-day compressive 
strengths shown below when tested according to ASTM Method C-873-77T 
(Ref 10): 
Wash Solvent Compressive Strength (psig) 
None (control) 3,920 
Acetone:water (90:10) 3,660 
None SR L90 
Mineral spirits 2,960 
Trisodium phosphate solution 220 
