Advanced Geotechnical Solutions was hired by Hydrosolutions Inc. to provide geotechnical engineering for a new produced water treatment plant. A main structure in the plant consisted of a 24 feet deep pump sump structure for circulating water. The structure had 18-inch-thick concrete walls and weighed approximately 768 kips. After the completion of the design, we were retained by Merit Energy to provide field engineering for the project as construction issues arise and density testing of soil backfill. The excavation for the sump structure was 24+ feet deep and was approximately 250 feet wide near the surface. In-field engineering was required to handle backfill material changes and unexpected groundwater from the unusually wet year. Personnel were on-site for weeks at a time performing density tests during backfill of the structure. To support field density testing a large number of soils were tested in the lab for maximum dry density.