Site description: Pipe was located along the east side of North Siwell Road, approximately one-half mile north of Mississippi State Highway 18. The soil was a saturated organic gray and brown silty clay.

Soil evaluation: Resistivity ohm-cm: 880. pH: 4.4. Redox: -150.

Sulfides: Positive.

Pipe specifications: 8" ductile iron pipe encased in 8-mil polyethylene.

Date of installation: September, 1977.

Date of dig-up: April 1, 1986.

Condition of pipe and encasement: The polyethylene was tested and found to be in excellent condition. It exceeded the standard values specified in ANSI/AWWA C105/A21.5. The 8" ductile iron pipe was found to be in good condition beneath the polyethylene encasement. The pipe's black asphaltic shop coating and manufacturer's painted markings were still very much intact. No oxidation was observed at any point along the exposed pipeline.

Conclusions: Polyethylene encasement provided excellent protection for the 8" ductile iron pipe, even in extremely corrosive, saturated soils.

Site description: Approximately 2,000 feet north of Sarasota Bay near the Manatee County Waste Water Treatment Plant in Bradenton, Florida. On the mainland, the pipe traversed a salt-water mangrove and tidal swamp and paralleled a large irrigation and drainage ditch. Pipeline was under seven to eight feet of cover. Soil next to the pipe, which was saturated, was a mixture of light brown, tan, black, and light gray sand and muck with a strong hydrogen-sulfide odor.

Soil evaluation: Resistivity ohm-cm: 2,880. pH: 6.9. Redox: - 44.

Sulfides: Positive.

Pipe specifications: 20" ductile iron sewer force main encased in 8-mil polyethylene.

Date of installation: 1974.

Date of dig-up: December 10, 1985.

Condition of pipe and encasement: Polyethylene was in excellent condition, with no tears or imperfections. Although the entire pipe surface under the polyethylene had a thin, wet film of black graphite, the original pipe markings were clearly visible. When brushed with a steel wire brush and sounded with a geologist's hammer, the pipe surface showed no pitting whatsoever.

Conclusions: The 8-mil polyethylene encasement provided the 20" ductile iron pipe excellent protection from the corrosive environment during 11 years of service.

Site description: Located in the southeast sector of Little Rock. The soil was a saturated dark reddish and grayish brown clay.

Soil evaluation: Resistivity ohm-cm: 600. pH: 6.9. Redox: +40.

Sulfides: Trace.

Pipe specifications: 30" ductile iron pipeline encased in 8-mil loose polyethylene.

Date of installation: 1972.

Date of dig-up: July 21, 1986.

Condition of pipe and encasement: A few minor tears in the polyethylene were evident, and trace amounts of soil were sparsely scattered over the pipe surface. No oxidation had occurred, and the pipe's asphaltic shop coating was still intact. No pitting or graphitization had occurred, even at locations where the polyethylene had been perforated. No deterioration of the polyethylene encasement was evident.

Conclusions: Inspection revealed that polyethylene encasement has provided excellent protection for the ductile iron pipe for 14 years, and that the polyethylene has maintained its integrity.