Geotech_Report_-_Eglin_Parkway_Lift_Station_591_Replacement_4.30.26.pdf

This document has been electronically signed and sealed by Keith V. Jacobs (license # 66577) on April 30, 2026. Printed copies of this document are not considered signed and sealed, and the signature must be verified on any electronic copies.

Eglin Parkway Lift Station 591 Replacement Okaloosa County, Florida LMJ File #: 26-160 April 30, 2026

Prepared for

Mr. Brock Jones, PE Kimley-Horn and Associates, Inc.

Brock.Jones@kimley-horn.com

Prepared by

Larry M. Jacobs & Associates, Inc.

328 East Gadsden Street, Pensacola, Florida 32501 Florida Certificate of Authorization #2184

Keith V. Jacobs, PE Principal Engineer FL Reg. #66577 mailto:Brock.Jones@kimley-horn.com

Eglin Parkway Lift Station 591 Replacement LMJ Project 26-160 April 30, 2026

Subsurface Conditions

▼ The boring encountered 11 inches of topsoil over sand to the bottom of the boring at 46 feet with some slightly silty sand between 2-3 feet and organic stain in the 15-ft sample.

▼ The boring was loose in the top 2 feet, medium dense to 4 feet, loose to 28 feet, dense to 33 feet, and very dense to the bottom of the boring at 46 feet.

▼ Groundwater was encountered at 6 feet below grade at the time of drilling.

▼ Groundwater levels will vary with the tide, the amount of local rainfall, and changes in site drainage characteristics and may be different at other times.

General Comments and Recommendations

▼ The boring encountered subsurface conditions that appear to be suitable for construction of the proposed lift station.

▼ The lift station is planned to be installed to roughly 26 feet below existing grade using the tremie method. Groundwater was encountered at 6 feet below existing grade, and water would need to be maintained at a similar depth inside the cased excavation.

▼ Dewatering outside the excavation would be needed to lower the water level inside the well after the soil has been removed (and before the concrete base is set) because of concerns with upward seepage destabilizing (boiling) the bottom of the excavation.

▼ The sand and slightly silty sand soils in the boring are suitable for fill or backfill around the lift station and are relatviely easy to compact but typically require ample moisture to achieve compaction.

Note: The above summary is an overview of the report and should not be used by itself for planning, design, and/or construction. See the relevant sections for further details.

Summary

Project Information

The site is located along the south side of Eglin Parkway (SR 85) between Clifford Drive and Eglin Parkway and roughly 250 feet west of the intersection with Gardner Drive in Fort Walton Beach, Florida. At the time of drilling, the site was wooded with underbrush and some large trees. We understand that the project includes the replacement of an existing lift station, and the proposed lift station is planned roughly 70 feet northwest of the existing generator building onsite. Based on the provided information, existing grade in the lift station area is roughly 6 feet, and the lift station has a planned top of pad elevation of 10 feet and bottom of wet well elevation of -10.2 feet with a bottom of concrete base planned at -20.2 feet. The top of the concrete base is planned at -11.2 feet covered with a 1-foot precast tremie topping slab. The lift station is planned to be polymer concrete installed using the caisson method.

Subsurface Exploration

Our exploration included one Standard Penetration Test (SPT) boring drilled for the proposed lift station to a depth of 46 feet. The boring was drilled using a truck mounted drill rig and was advanced between sampling using a “mud” jetting technique with a Bentonite drilling mud. The subsurface conditions encountered in the boring can be found on the boring log here.

The above project information is the basis of our recommendations. If this information changes or is incorrect, our office should be notified, and changes to our report may be needed.

Project Information

Dewatering

The lift station is planned to be a pre-cast polymer concrete well with an open bottom installed using the tremie method. If the water level inside the well is maintained near the natural groundwater level, the excavation could remain stable without dewatering, and the concrete for the base could be placed from the bottom using the tremie method. If the water level inside the lift station needs to be lowered before installing the concrete base and tremie topping slab, after soil has been removed, we would recommend dewatering outside the lift station using well points before lowering water inside the well. Lowering the water level inside the well after the soil has been excavated without lowering the water level outside could cause upward seepage and destabilize (boil) the bottom of the excavation. If the bottom of the excavation boils or heaves during construction, the excavation should be promptly flooded, and our office should be contacted.

Excavations

The polymer concrete lift station should serve as casing to maintain stability of the excavation.

The contractor is solely responsible for designing and constructing safe excavations that maintain stability during construction. All excavations should be constructed in accordance with the latest local, state, and federal safety regulations.

Backfill Recommendations

▼ The native sand and slightly silty sand soils in the boring are suitable to backfill around the lift station (where necessary) and for filling the pad.

▼ The native sand and slightly silty sand soils and are relatviely easy to compact but typically require ample moisture to achieve compaction.

▼ Backfill and fill material should be the soil types listed in the following table and placed at the noted lift thicknesses.

▼ All backfill and fill should be free of organics, debris, or other deleterious materials and non-plastic.

▼ Samples of imported fill material, if needed, should be submitted to the geotechnical engineer for testing and evaluation prior to shipment to the site.

Fill Recommendations

Material Type

Lift Thickness (in) Equipment Type

Large Equipment

Hand Operated

Equipment Large Hand Operated

Sand and Slightly Silty Sand 10-12 6 Vibratory Roller Plate Tamper

Earthwork

Compaction

▼ Fill and backfill material should be moisture conditioned to within 2% of its optimum moisture content prior to compaction.

▼ Note that the white sand soils will loosen when they dry, and these soils should be kept moist until overlying fill is placed and slabs have been poured. Soils that dry and loosen should be rewetted and recompacted prior to placing overlying fill or pouring slabs.

▼ A mechanical plate tamper is recommended for hand-operated compaction equipment.

A small vibratory trench roller could also be used.

▼ Backfill should be compacted and compaction verified per the table below using in-place nuclear density tests. Density tests should be run by a qualified technician working under the supervision of a qualified geotechnical engineer.

Compaction and Testing Recommendations

Site Element Minimum

Compaction

(ASTM D1557)

Minimum Compaction Testing Frequency

Per 12-inch Increment

Backfill and Fill for Lift Station 95% 2 per 12-inch increment

Earthwork

Lift Station Recommendations

▼ The boring encountered conditions that appear to be suitable for the construction of the proposed lift station.

▼ The boring had loose sand at the planned lift station bottom depth of roughly 26 feet below grade. The lift station construction is expected to create a net decrease in stress, and the proposed construction method is not expected to create significant settlement.

▼ Care should be taken not to overly disturb/loosen the soils at the bottom of the lift station.

▼ If the soils are loose or disturbed at the bottom of the lift station excavation, we would recommend removing the loose material and replacing it with a well-graded crushed stone, tamped using the crowd force of the auger.

▼ If needed for lift station analysis and design, our recommend soil parameters for the conditions in the boring are shown on the boring log (left side) and include the estimated unit weight (γ) and angle of friction (φ).

▼ The estimated soil parameters on the boring log are based on the SPT and laboratory results, published correlations, and our experience with similar soils.

▼ Note that the estimated unit weights provided are moist/buoyant above and near the water table and buoyant below the water table.

Lift Station

STANDARD PENETRATION TEST BORING

ALL BORING LOCATIONS ARE APPROXIMATE

N

B-1

03-25-26

BROWN LOOSE SILTY SAND, TRACE ROOTS

(1")(TOPSOIL)(SM)

WHITE/TAN LOOSE SAND (SP)

DARK GRAY MEDIUM DENSE SLIGHTLY SILTY SAND

(SP-SM)

WHITE MEDIUM DENSE TO LOOSE SAND (SP)

TAN LOOSE SAND (SP)

LIGHT TAN LOOSE SAND (SP)

BROWN STAINED LOOSE SAND (ORGANIC ODOR) (SP)

WHITE LOOSE SAND, TRACE CLAY (SP)

WHITE LOOSE TO DENSE TO VERY DENSE SAND (SP)

w=3.8 -200=1.7 w=16.4 -200=4.8 w=21.8 -200=3.8 γ φ 98/48 29

100/50 30

2998/48

Boring Location Map

Boring

L

Test Results

Laboratory testing for this project included three wash #200 sieve and natural moisture content tests run on selected samples to assist in soil classification and to evaluate and document basic soil properties. The laboratory test results are shown on the boring logs adjacent to the samples tested.

Lab

Basis of Recommendations

Recommendations rendered herein are based on assumed and/or design information available at the time of this report, the subsurface conditions encountered in the test boring, generally accepted geotechnical engineering principles and practices, and our experience with similar soil and groundwater conditions. Should final project information or existing conditions differ from the information used in this report, or should any soil conditions not discussed in this report be encountered during construction, our office should be notified and retained so that this report can be modified as needed. LMJ should be provided the final plans and specifications for review to determine if any changes to our report are needed based on the final design and that our recommendations have been properly interpreted.

This report and any correspondence are intended for the exclusive use of our client for the specific application to the project discussed. LMJ is not responsible for the interpretations, conclusions, or recommendations made by others based on the information in this report.

Regardless of the care exercised in performing a Geotechnical Exploration, the possibility always exists that soil and/or groundwater conditions will differ from those encountered at the specific boring location. In addition, construction operations may alter the soil conditions.

Therefore, it is recommended that a representative from LMJ be involved during the construction phases discussed in this report.

Test Methods

Standard Penetration Test

The Standard Penetration Test (SPT) consists of driving a 2-inch diameter split spoon sampler into the ground using a 140-pound hammer dropped 30 inches. The number of blows required to drive the sampler one foot (after seating it 6 inches) is referred to as the blow count or “N” value and represents the relative density of subsurface soils. “N” values can be found on the boring logs. The SPT borings were drilled in general accordance with ASTM D1586 using a track mounted drill rig. Each sample was removed from the sampler, classified in the field by the driller, and packaged for visual classification by our engineering staff and laboratory testing.

Other Test Methods

Wash #200 Sieve (ASTM D1140) and Moisture Content (ASTM D2216).

Appendix

Appendix