Crystal_Beach_Geotech_2019.pdf

This document is a Subsurface Soil Investigation Report prepared by Driggers Engineering Services Incorporated for Pinellas County Public Works for a Drainage and Road Improvements project in Crystal Beach, Florida. The investigation was conducted to assess the current pavement section, subsurface soil, groundwater, and permeability conditions for potential roadside drainage and stormwater management improvements. The field investigation program included forty-one (41) locations of pavement cores and hand auger borings across the project area, with borings conducted to depths of 2-6 feet below grade.

The investigation revealed predominantly sandy soils classified as SP to SP-SM in the Unified Soil Classification System, with surface elevations ranging from approximately +2.9 to +17.3 feet (NAVD). Groundwater observations were made during an intermittent rainfall season, with estimated seasonal high groundwater levels varying between 2.5 and 8.0 feet. Laboratory testing included ten grainsize analyses and four organic content tests. The soil investigation noted some locations with organic content between 7-8%, which was considered marginal to excessive, and recommended further investigation and potential removal and replacement of highly organic soils. The study also indicated that the sandy soil types are generally suitable for subgrade support for potential stormwater piping, provided the subgrade is properly prepared and compacted.