NOVA has provided geotechnical engineering, special inspection, and materials testing for two projects under this as-needed contract:
- The Gordon Hill Road Replacement Pipeline project consists of the replacement of 4,700 feet of 10-inch steel water main with a 12-inch PVC water main. 3,200 feet of the replacement requires excavation of all new pipeline trench, while the rest of the replacement reuses the existing pipeline trench.
- The Lilac Road Pipeline Replacement project consists of the replacement of the existing 6-inch diameter asbestos cement pipe (ACP) water main with an 8-inch PVC pipe water main along either the existing alignment or a new alignment.
GEOTECHNICAL ENGINEERING
The geotechnical investigation consisted of background review, site reconnaissance, geologic mapping, excavation and logging of test pits, seismic refraction lines, laboratory testing, engineering evaluations, and reporting. NOVA understood from the District that in the past, they had struggled with abundant change orders submitted by the contractors for encountering unexpected hard rock during installation of water lines. NOVA customized an investigation for the District to walk and carefully map the whole length of the proposed water line and visually identify areas where hard rock could possibly be encountered. Where these areas were identified, they were subsequently explored with test pits and seismic lines. For Gordon Hill, 17 test pits were excavated, logged, and sampled.
For Lilac Road, 16 test pits were excavated, logged, and sampled, and 2 seismic refraction lines were performed to correlate the rippability of the material in the subsurface. The samples were sent to our in-house laboratory for testing. Engineering evaluations were conducted using the information from the preceding tasks and then a geotechnical investigation report was composed with our geologic and geotechnical-related findings and recommendations for design and construction. NOVA provided an estimate of the rippability along the entire alignment, with zones rated from 1-5 on excavation difficulty. This allowed the contractors to more precisely bid the job with the known areas of hard rock. The District was protected from change orders when the contractor submitted change orders in areas where NOVA had previously identified hard rock.
SPECIAL INSPECTION AND MATERIALS TESTING
Testing and inspection services for both projects included observation and testing of utility trench backfill, subgrade, aggregate base material, and asphalt coring. The Lilac Road Pipeline Replacement also included shoring observation.