13-13. 2024-03-31 Alpha Geotech MLK Soils.pdf

Alpha Geotechnical and Testing Services, Inc. 4778-A Woodlane Circle, Tallahassee, FL 32303 (850) 514-4171 www.alpha-geotech.com

March 31, 2024 File No. 24-5781

Ms. Caroline Reynolds, EI Singhofen & Associates 11723 Orpington Street, #100 Orlando, FL 32817

Subject: MLK Jr Blvd Drainage Improvements Project, Tallahassee, FL

Dear Ms. Reynolds:

As authorized by your Mr. Robert Gaylord, PE, we have completed performance of seven asphalt cores and soil bores along the subject roadway improvement project. The project generally extends from about 50’ north of the intersection of Dr. Martin Luther King, Jr. Boulevard (MLK) and Barbourville Street southward to the intersection of MLK and Osceola Street. We first used a 4” diameter thin-walled core bit to obtain asphalt core samples and then augered through the underlying soil (and limerock in one case) until about 6’ to 6 ½’ below the pavement surface.

The bore holes were later back-filled with drill cuttings and topped with emulsified asphalt patching material. The relatively narrow street with street-side parking required traffic control on all seven locations. At four of these locations we had sufficient work area space to conduct our borings with the Standard Penetration Test (SPT) procedure and limit traffic to one lane, but the other three locations done closer to the centerline of the road required use of more portable equipment to keep from closing both lanes of traffic. In these three more restrictive locations, we use a dynamic cone penetrometer (DCP) device to evaluate the soil consistency (relative hardness). The DCP “P-value” readings are generally comparable to the SPT “N-value”.

Based on our visual observations, the existing pavement in the project area has been extensively patched in the past but appears generally stable with no current “failure” areas. It is apparent that at least two and possibly three asphalt overlays have been done since up to 9.4” of asphalt was found at our core location C-4 and tapering toward the edges to as little as 2.6” at C-5. Beneath the asphalt, six of the sample locations encountered apparent sand-clay road base (limerock base was found only at the southernmost location, C-7). Predominantly clayey sands and silty sands underly these base materials. The attached Figure 1 shows the locations and profiles of the conditions at each core/bore. Laboratory classification tests are summarized adjacent to the profiles. Based on the SPT N-value and DCP P-value readings, most of the subgrade soils are in a very loose to loose condition until the borings done around Young Street and southward where these are generally very loose to loose in the upper 3’ and becoming medium dense with depth.

Sincerely, Alpha Geotechnical and Testing Services, Inc.

Stephen P. Shanley, PE

FL #40653

Alpha

Alpha Geotechnical and Testing Services, Inc.

Certificate of Authorization No. 00007967

Foundation Evaluations Environmental Studies Construction Materials Testing

This item has been digitally signed and sealed by Stephen P. Shanley, PE on the date adjacent to the seal. Printed copies of this document are not considered signed and sealed and the signature must be verified on any electronic copies.