Leachability of active ingredients from some CCA treated and creosoted poles in service. A progress report after 10 years testing
A J Nurmi
CCA K33 TYPE B treated or creosoted poles, 10 pieces of each treatment type, have been monitored from the treatment plant to an electricity line, which was build up in Southern Finland in 1978. Preservative retention was determined by taking borings at four different levels: 1.5 m from the top end, 1 m above ground line, ground line and 0.5 m below ground. Determinations were made before setting up the poles and then after 2, 4 and 10 years in service. Also the soil around the poles and in some cases under the but end was analyzed to find evidence of leached heavy metals or creosote oil. After 10 years service the distribution of creosote has been dramatically changed. Only 1/3 of the originally analyzed creosote (150 kg/m³) was found in the borings taken 1 m above the ground level and 1.5 m from the top of the poles. However, the reduction at ground line and below ground was only 10%. This suggests that creosote oil runs down effectively and finally the flow becomes slower when creosote oil reaches the butt end, where the moisture content is much higher and the temperature lower. Significant quantities of creosote oil, 51 g/kg oven dry soil at the highest, were found in soil around the poles and under the but ends. In CCA treated poles arsenic has been leached out in large quantities at every level. At its highest the average loss was 33% at the ground line. In other parts of the poles the average loss of arsenic varied from 21% to 25%. From the top of the poles the average loss of copper was 11%. The other observation points gave figures near 20%. Chromium had been leached out in considerable amounts only from the ground level, where the average loss of 24% was analyzed. The soil samples around the poles showed some high heavy metal contents. The average amount of arsenic analyzed was 180 mg/dm³ (oven dried soil) and the greatest amount detected was as high as 420 mg/dm³. The copper content was 79 mg/dm³ and chromium 65 mg/dm³ in average.