Mid-Western Placer Regional Sewer


Placer County
City of Lincoln


Materials Testing


Placer County, CA


2010 – 2016


The Mid-Western Placer Regional Sewer project is located between North Auburn and Lincoln, California. The project had four major components:

  • Expansion of the Lincoln Wastewater Treatment and Reclamation Facility,
  • Diversion and decommissioning of the SMD1 WWTP,
  • Construction of 13 miles of 28 to 36 inch diameter pressurized pipe from the SMD1 WWTP to Hwy 193 near Lincoln,
  • Construction of 2.5 miles of 12 to 30 inch diameter pressurized pipe at East Catlett Rd. for recycled water distribution.


Blackburn Consulting prepared a Geotechnical Design Report and Geotechnical Data Report. Our site investigation included:

  • logging and sampling of 70 borings to depths ranging from 3 to 51 feet below ground surface (7 of the borings were performed for the Lincoln Wastewater Treatment and Reclamation Facility improvements),
  • 15 test pit excavations,
  • geologic mapping,
  • 15 seismic refraction surveys to evaluate rock hardness and excavatability, and
  • a large laboratory testing program.


During construction, Blackburn provided geotechnical support and quality assurance materials testing. When there appeared to be issues with trench settlement during construction, Blackburn engineers helped the County evaluate the stability of the trenches and provided mitigation recommendations.


At one point during construction, an important over-excavation stockpile was contaminated with lime. Blackburn helped avoid construction delay through emergency field and laboratory testing to verify the soil would still meet project specifications.