3-CoRR 2MG GST - Addendum 1-signed.pdf

This document is a Geotechnical Engineering Study prepared by Raba Kistner Consultants, Inc. (RKCI) for the City of Round Rock Waste Water Treatment Plant (WWTP) regarding a proposed 2 million gallon ground storage tank project located at 3939 East Palm Valley Boulevard in Round Rock, Texas. The study was conducted on November 19, 2021, and involved subsurface exploration utilizing 7 borings drilled to approximately 20 feet below the existing ground surface, with comprehensive laboratory testing of soil samples to evaluate geotechnical conditions for tank foundation design.

The geotechnical investigation revealed the site is underlain by alluvium deposits overlying Austin Chalk, with soil strata consisting primarily of fat clay and lean clay with varying consistency and gravel content. Groundwater was encountered at depths ranging from 10 to 18 feet during drilling operations. Key recommendations include utilizing a shallow foundation system with select fill replacement to mitigate expansive soil-related movements, implementing specific site drainage and construction considerations, and conducting further geotechnical observation during construction. The report provides detailed guidance on foundation dimensions, bearing pressures, lateral resistance, and site preparation to ensure stable tank infrastructure, with emphasis on managing potential soil-related challenges typical to the central Texas geological region.