As part of distribution improvements, National Grid’s contractor bored 830LF through rock using HDD. The bore was 30″, with a 16″ HDPE casing, carrying three, 4″ HDPE conduits.
As part of the installation, the NY Thruway Authority required the casing be backgrouted, and the casing pipe’s annular space grout filled.
The proposed backgrout had to be pumpable 830LF at very low pressure, dense enough to displace the 10PPG drilling mud, and provide sufficient strength to meet Thruway requirements. The proposed annular space grout had to be pumpable 830LF at very low pressure, light enough to not apply excessive pressure on the conduit pipes, and also provide sufficient strength to meet Thruway requirements.
CJGeo proposed two different grout mixes to meet the project requirements. 85lb/cuft casing backgrout for displacement of the 10PPG (75lb/cuft) drilling mud, and 25lb/cuft annular space grout for within the casing.
CJGeo’s crew mobilized to the site, and successfully performed the backgrouting and annular space grouting in a single day.