STORMWATER CALCULATIONS REPORT

2348 – Dunns Creek Boat Ramp

Submitted to FDEP and Putnam County

DATE: 09/12/2025

JEREMY W. CALLOWAY, P.E.

CA# 34646, PE# 70838

jcalloway Digital Signature Text

1. Introduction

This drainage analysis is for Dunns Creek Boat Ramp located in in Putnam county, FL. The drainage area in consideration totals 2.54± acres. The project consists of a new boat ramp, restroom, gravel parking, and stormwater management.

Stormwater management for the proposed improvements will utilize a dry retention system which discharges to Dunns Creek to the south of the property. The system will use a series of swales and the void space within the gravel for attenuation. The SCS Unit Hydrograph Method along with ICPR 4 was used to route various storms through the proposed stormwater management facility. Peak flow and max stage considerations were given to the Mean Annual-24hr, 5yr-24hr, 10yr-24hr, and 25yr-24hr storms.

2. Pre-Development

Based on the SCS Soil Survey of Putnam County, there are two soil types present on the site. See attached Soils Map and NRCS Report. In summary, the soil type is listed as follows:

Soils Map Symbol

Soil Name Hydrologic Soil Group

8 Avents, 0-2% Slopes A

The pre-development drainage area totaling 2.54 acres was modeled as unimproved using a single basin (Pre Basin – A). Pre Basin-A flows from Northeast to Southwest into Dunns Creek. See attached Pre- and Post- Development Maps. The TR55 methodology was used to generalize a runoff Curve Number (CN) for the site. The soils present on the site are considered hydrologic soil group A. Hydrologic soil group A was selected to represent the site, and the cover type was considered to be “Woods – poor Condition.”

Pre Basin- A

Area Description Area (sf) Area (ac) CN C

Total (Composite) 110,791 2.54 52.3 0.35

Pavement 15,232 0.35 98.0 0.95

Pervious (HSG ‘D’) 95,559 2.19 45.0 0.25

Time of Concentration Time of concentration (Tc) for the pre-development drainage basin was calculated using the TR-55 methodology. Please see the attached Time of Concentration Calculations. The Tc was calculated to be 24.6 minutes.

Estimated Seasonal High Groundwater Level and Permeability Rates A Geotechnical exploration was performed by Jackson Geotechnical Engineering to provide information about the soils, water table, and design recommendations. Based on the average SHGW on the boring logs, a SHGW of 3.00’ was used for design.

Permeability Rates

We obtained 4 permeability rates throughout the site and averaged them together. A factor of safety (FS) of 2 was applied to the hydraulic conductivity rates in the ICPR model for 72-hour recovery. These values were then conservatively applied in the ICPR model for the recovery analysis.

Kv / FS = 22.4 ft/day / 2 = 11.2 ft/day

Kh / FS = 20.6 ft/day / 2 = 10.3 ft/day

Peak Rate Factor Due to the site’s mild slopes and minimal improvements, a Peak Rate Factor (K) = 256 was used for the pre-development basin.

3. Post-Development

The proposed improvements were analyzed using one post basin. Runoff from the post basin is routed through the gravel and swales to receive treatment. Any discharge from the retention areas will flow through openings in the timber edge and into the creek.

Please see the pose development drainage map and grading plan.

Post Basin-

Area Description Area (sf) Area (ac) CN C

Total (Composite) 110,791 2.54 70.4 0.69

Building 600 0.01 98.0 0.95

Gravel 74,964 1.72 85.0 0.90

Pervious 35,227 0.81 79.0 0.25

Time of Concentration Time of concentration was estimated from the most remote part of the catchment area to the design node. This included inlet or overland flow time and travel time in sewers. A minimum time of concentration of 10 minutes was used in the post-development analysis for the basin.

Peak Rate Factor The post-development will not have any storm pipes for conveyance and no directly connected impervious area. A Peak Rate Factor (K) = 323 was used in the analysis of the post-development basin.

Tailwater Considerations The tailwater for the boundary node was assumed to be 4.00’, which is the approximate Existing top of bank elevation at receiving creek at the proposed discharge locations.

Treatment Volume Requirements This Dry Retention facility was designed to meet St. Johns River Water Management District criteria Chapter 62-330 F.A.C. of the SJRWMD Applicants Handbook, and Putnam County criteria. Treatment volume calculation requirements for the post basin can be seen below.

Post Basin TV Calculation for SJRWMD Dry Pond:

The SJRWMD required treatment volume for Post Basin - 1 was calculated as follows:

1. 0.5-inch of rainfall over the improved drainage area from section 5.2:

𝑉𝑟 = PA = (

0.5 inch × 110,791 sf

12 inch/ft ) = 4,616 cf

2. 1.25-inches of rainfall over the impervious area from section 5.2:

𝑉𝑡 = PAimpervious = (

1.25 inch × 75,564 sf

12 inch/ft ) = 7,871 cf

An additional 0.5 inch over the Drainage area is added to the greater of the above calculations to determine the total required TV per SJRWMD requirements.

𝐕𝑺𝑱𝑹𝑾𝑴𝑫 = 4,616 cf + 7,871 = 𝟏𝟐, 𝟒𝟖𝟖 cf

The greater of the above treatment volumes determined the treatment volume required for the system. The treatment volume required, and the treatment volume provided is as follows:

Post Basin

Basin Area

Impervious Area

Required Weir

Required

TV

Design Weir

Provided

TV

(ac) (sf) (ft) (cf) (ft) (cf)

1 2.354 75,564 4.79 12,488 4.90 0.37

Stage vs. Storage Volume

SWMF-1

Stage Area Area Vol. Inc. Vol. Inc. Vol. Sum Vol. Sum

(ft) (sf) (ac) (cf) (ac-ft) (cf) (ac-ft)

BOT 4.00 3,186 0.073 - - - -

4.50 4,847 0.111 2,008 0.046 2,008 0.05

TOB 5.00 6,745 0.155 17,891 0.411 19,899 0.46

4. Pre/Post-Development Discharge Comparison and Staging:

The following table represents the Pre vs. Post development runoff. Please note that the Post-Development runoff is less than the Pre-development runoff after being routed through the dry retention SWMFs:

Pre/Post Comparison

Pre-Creek Post-DCreek

(cfs) (cfs)

MA-24hr 0.42 0

5yr-24hr 1.25 0.39

10yr-24hr 1.57 0.64

25yr-24hr 2.66 2.50

Storm Event

Dry Retention (Swales and Gravel)

(ft)

MA-24hr 4.87

5yr-24hr 4.93

10yr-24hr 4.94

25yr-24hr 5.00

TOB 5.00

5. 72-Hour Recovery for Dry Retention:

Per SJRWMD criteria, The required treatment volume must be recovered within 72 hours following a storm event for dry retention. Infiltration will occur in two stages. Stage 1 allows stormwater to be drawn down by vertical infiltration and Stage 2 occurs through saturated lateral flow. The required treatment volume for Post Basin-1 is 12,488 cf. The volume was applied to the node as a “slug load”. The ICPR model reflects a recovery time of 29.60 hrs (12,609 cf) for the dry system through the swales.

DUNNS CREEK BOAT RAMP

PROJECT #: 2348

ADDRESS: PUTNAM COUNTY, FL

PARCEL ID: 36-10-26-0000-0000-0002

SITE

N

FLOOD ZONE: AE

FEMA PANEL NUMBER: 12107C0328C

BFE: 5.00’ NAVD88

United States Department of Agriculture

A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants

Custom Soil Resource Report for

Putnam County Area, Florida

Natural Resources Conservation Service

July 16, 2025

Preface Soil surveys contain information that affects land use planning in survey areas.

They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers.

Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment.

Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions.

The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations.

Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?

cid=nrcs142p2_053951).

Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations.

The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey.

Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information.

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Contents Preface Soil Map

Soil Map Legend Map Unit Legend Map Unit Descriptions

Putnam County Area, Florida 3—Myakka-Myakka, wet, fine sands, 0 to 2 percent slopes 8—Arents, 0 to 2 percent slopes 26—Terra Ceia muck, 0 to 1 percent slopes, frequently flooded

Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit.

Custom Soil Resource Report Soil Map

439480 439510 439540 439570 439600 439630 439660 439690 439720 439750 439780 439810

439480 439510 439540 439570 439600 439630 439660 439690 439720 439750 439780 439810

29° 34' 50'' N

7'

0' ' W

29° 34' 50'' N

7'

6' ' W

29° 34' 43'' N

7'

0' ' W

29° 34' 43'' N

7'

6' ' W

N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 17N WGS84 0 50 100 200 300

Feet 0 20 40 80 120

Meters Map Scale: 1:1,640 if printed on A landscape (11" x 8.5") sheet.

Soil Map may not be valid at this scale.

MAP LEGEND MAP INFORMATION

Area of Interest (AOI) Area of Interest (AOI)

Soils Soil Map Unit Polygons

Soil Map Unit Lines

Soil Map Unit Points

Special Point Features Blowout

Borrow Pit

Clay Spot

Closed Depression

Gravel Pit

Gravelly Spot

Landfill

Lava Flow

Marsh or swamp

Mine or Quarry

Miscellaneous Water

Perennial Water

Rock Outcrop

Saline Spot

Sandy Spot

Severely Eroded Spot

Sinkhole

Slide or Slip

Sodic Spot

Spoil Area

Stony Spot

Very Stony Spot

Wet Spot

Other

Special Line Features

Water Features Streams and Canals

Transportation Rails

Interstate Highways

US Routes

Major Roads

Local Roads

Background Aerial Photography

The soil surveys that comprise your AOI were mapped at 1:15,800.

Warning: Soil Map may not be valid at this scale.

Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale.

Please rely on the bar scale on each map sheet for map measurements.

Source of Map: Natural Resources Conservation Service Web Soil Survey URL:

Coordinate System: Web Mercator (EPSG:3857)

Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required.

This product is generated from the USDA-NRCS certified data as of the version date(s) listed below.

Soil Survey Area: Putnam County Area, Florida Survey Area Data: Version 22, Aug 23, 2024

Soil map units are labeled (as space allows) for map scales 1:50,000 or larger.

Date(s) aerial images were photographed: Jan 6, 2022—Feb 10, The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident.

Map Unit Legend

Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI

3 Myakka-Myakka, wet, fine sands, 0 to 2 percent slopes

1.0 9.0%

8 Arents, 0 to 2 percent slopes 9.6 87.5%

26 Terra Ceia muck, 0 to 1 percent slopes, frequently flooded

0.4 3.5%

Totals for Area of Interest 11.0 100.0%

Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit.

A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class.

Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils.

Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape.

The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas.

An identifying symbol precedes the map unit name in the map unit descriptions.

Each description includes general facts about the unit and gives important soil properties and qualities.

Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement.

Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series.

Some map units are made up of two or more major soils or miscellaneous areas.

These map units are complexes, associations, or undifferentiated groups.

A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps.

The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.

An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example.

An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.

Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example.

Putnam County Area, Florida

3—Myakka-Myakka, wet, fine sands, 0 to 2 percent slopes

Map Unit Setting National map unit symbol: 2twt7 Elevation: 0 to 160 feet Mean annual precipitation: 38 to 68 inches Mean annual air temperature: 68 to 77 degrees F Frost-free period: 310 to 365 days Farmland classification: Not prime farmland

Map Unit Composition Myakka and similar soils: 70 percent Myakka, wet, and similar soils: 15 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit.

Description of Myakka

Setting Landform: Flatwoods on marine terraces Landform position (three-dimensional): Tread, talf Down-slope shape: Convex Across-slope shape: Linear Parent material: Sandy marine deposits

Typical profile A - 0 to 6 inches: fine sand E - 6 to 20 inches: fine sand Bh - 20 to 36 inches: fine sand C - 36 to 80 inches: fine sand

Properties and qualities Slope: 0 to 2 percent Depth to restrictive feature: More than 80 inches Drainage class: Poorly drained Runoff class: Very high Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high

(0.57 to 5.95 in/hr) Depth to water table: About 6 to 18 inches Frequency of flooding: None Frequency of ponding: None Maximum salinity: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Sodium adsorption ratio, maximum: 4.0 Available water supply, 0 to 60 inches: Low (about 3.9 inches)

Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4w Hydrologic Soil Group: A/D Ecological site: F155XY120FL - Sandy Flatwoods and Hammocks Forage suitability group: Sandy soils on flats of mesic or hydric lowlands

(G155XB141FL)

Other vegetative classification: Sandy soils on flats of mesic or hydric lowlands (G155XB141FL), South Florida Flatwoods (R155XY003FL)

Hydric soil rating: No

Description of Myakka, Wet

Setting Landform: Flatwoods on marine terraces Landform position (three-dimensional): Tread, talf Down-slope shape: Convex Across-slope shape: Linear Parent material: Sandy marine deposits

Typical profile A - 0 to 6 inches: fine sand E - 6 to 20 inches: fine sand Bh - 20 to 36 inches: fine sand C - 36 to 80 inches: fine sand

Properties and qualities Slope: 0 to 2 percent Depth to restrictive feature: More than 80 inches Drainage class: Poorly drained Runoff class: Very high Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high

(0.57 to 5.95 in/hr) Depth to water table: About 3 to 18 inches Frequency of flooding: None Frequency of ponding: None Maximum salinity: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Sodium adsorption ratio, maximum: 4.0 Available water supply, 0 to 60 inches: Low (about 3.9 inches)

Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4w Hydrologic Soil Group: A/D Ecological site: F155XY120FL - Sandy Flatwoods and Hammocks Forage suitability group: Sandy soils on flats of mesic or hydric lowlands

(G155XB141FL)

Other vegetative classification: Sandy soils on flats of mesic or hydric lowlands

(G155XB141FL), South Florida Flatwoods (R155XY003FL) Hydric soil rating: Yes

Minor Components

Placid Percent of map unit: 5 percent Landform: Drainageways on marine terraces, depressions on marine terraces Landform position (three-dimensional): Tread, dip Down-slope shape: Concave Across-slope shape: Concave Ecological site: R155XY070FL - Sandy Freshwater Isolated Marshes and Swamps Other vegetative classification: Sandy soils on stream terraces, flood plains, or in depressions (G155XB145FL), Freshwater Marshes and Ponds

(R155XY010FL)

Hydric soil rating: Yes

Eaugallie Percent of map unit: 5 percent Landform: — error in exists on — Landform position (three-dimensional): Tread, talf Down-slope shape: Convex Across-slope shape: Linear Ecological site: F155XY120FL - Sandy Flatwoods and Hammocks Other vegetative classification: Sandy soils on flats of mesic or hydric lowlands

(G155XB141FL), South Florida Flatwoods (R155XY003FL) Hydric soil rating: No

Basinger Percent of map unit: 5 percent Landform: Flats on marine terraces, drainageways on marine terraces Landform position (three-dimensional): Tread, talf, dip Down-slope shape: Convex, concave Across-slope shape: Linear, concave Ecological site: F155XY120FL - Sandy Flatwoods and Hammocks Other vegetative classification: Slough (R155XY011FL), Sandy soils on flats of mesic or hydric lowlands (G155XB141FL) Hydric soil rating: Yes

8—Arents, 0 to 2 percent slopes

Map Unit Setting National map unit symbol: bvkd Elevation: 0 to 150 feet Mean annual precipitation: 46 to 54 inches Mean annual air temperature: 68 to 75 degrees F Frost-free period: 304 to 334 days Farmland classification: Not prime farmland

Map Unit Composition Arents and similar soils: 100 percent Estimates are based on observations, descriptions, and transects of the mapunit.

Description of Arents

Setting Landform: Rises on marine terraces Landform position (three-dimensional): Rise Down-slope shape: Convex Across-slope shape: Linear Parent material: Altered marine deposits

Typical profile AC - 0 to 80 inches: sand

Properties and qualities Slope: 0 to 2 percent Depth to restrictive feature: More than 80 inches Drainage class: Somewhat poorly drained Runoff class: Negligible Capacity of the most limiting layer to transmit water (Ksat): Very high (19.98 to

50.02 in/hr) Depth to water table: About 20 to 40 inches Frequency of flooding: None Frequency of ponding: None Maximum salinity: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Sodium adsorption ratio, maximum: 4.0 Available water supply, 0 to 60 inches: Very low (about 2.4 inches)

Interpretive groups Land capability classification (irrigated): None specified Hydrologic Soil Group: A Forage suitability group: Forage suitability group not assigned (G155XB999FL) Other vegetative classification: Forage suitability group not assigned

(G155XB999FL)

Hydric soil rating: No

26—Terra Ceia muck, 0 to 1 percent slopes, frequently flooded

Map Unit Setting National map unit symbol: 2svzm Elevation: 0 to 130 feet Mean annual precipitation: 43 to 55 inches Mean annual air temperature: 68 to 79 degrees F Frost-free period: 350 to 365 days Farmland classification: Not prime farmland

Map Unit Composition Terra ceia and similar soils: 90 percent Minor components: 10 percent Estimates are based on observations, descriptions, and transects of the mapunit.

Description of Terra Ceia

Setting Landform: Flood plains on marine terraces Landform position (three-dimensional): Tread, talf Down-slope shape: Convex, linear Across-slope shape: Linear Parent material: Herbaceous organic material

Typical profile Oa1 - 0 to 28 inches: muck Oa2 - 28 to 80 inches: muck

Properties and qualities Slope: 0 to 1 percent

Depth to restrictive feature: More than 80 inches Drainage class: Very poorly drained Runoff class: High Capacity of the most limiting layer to transmit water (Ksat): High to very high (5.95 to 19.98 in/hr) Depth to water table: About 0 inches Frequency of flooding: Frequent Frequency of ponding: None Maximum salinity: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Sodium adsorption ratio, maximum: 4.0 Available water supply, 0 to 60 inches: Very high (about 23.9 inches)

Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 7w Hydrologic Soil Group: A/D Ecological site: R155XY060FL - Organic Freshwater Floodplain Marshes and

Swamps Forage suitability group: Organic soils in depressions and on flood plains

(G155XB645FL)

Other vegetative classification: Organic soils in depressions and on flood plains

(G155XB645FL), Freshwater Marshes and Ponds (R155XY010FL) Hydric soil rating: Yes

Minor Components

Gator Percent of map unit: 3 percent Landform: Depressions on flood plains on marine terraces Landform position (three-dimensional): Tread, dip, talf Down-slope shape: Concave, linear Across-slope shape: Concave, linear Ecological site: R155XY060FL - Organic Freshwater Floodplain Marshes and

Swamps Other vegetative classification: Organic soils in depressions and on flood plains

(G155XB645FL), Freshwater Marshes and Ponds (R155XY010FL) Hydric soil rating: Yes

Samsula Percent of map unit: 2 percent Landform: Depressions on marine terraces Landform position (three-dimensional): Tread, dip Down-slope shape: Concave Across-slope shape: Concave Ecological site: R155XY100FL - Organic Freshwater Isolated Marshes and

Swamps Other vegetative classification: Organic soils in depressions and on flood plains

(G155XB645FL), Freshwater Marshes and Ponds (R155XY010FL) Hydric soil rating: Yes

Riviera Percent of map unit: 2 percent Landform: Flats on marine terraces, drainageways on marine terraces Landform position (three-dimensional): Tread, talf, dip Down-slope shape: Linear Across-slope shape: Concave, linear

Ecological site: R155XY080FL - Sandy over Loamy Freshwater Isolated Marshes and Swamps

Other vegetative classification: Sandy over loamy soils on flats of hydric or mesic lowlands (G155XB241FL), Slough (R155XY011FL)

Hydric soil rating: Yes

Favoretta Percent of map unit: 1 percent Landform: Flood plains on drainageways on marine terraces Landform position (three-dimensional): Tread, talf Down-slope shape: Linear Across-slope shape: Concave Ecological site: R155XY050FL - Loamy and Clayey Freshwater Floodplain

Marshes and Swamps Other vegetative classification: Loamy and clayey soils on stream terraces, flood plains, or in depressions (G155XB345FL) Hydric soil rating: Yes

Bluff Percent of map unit: 1 percent Landform: Flood plains on drainageways on marine terraces Landform position (three-dimensional): Tread, talf Down-slope shape: Linear Across-slope shape: Concave Ecological site: R155XY050FL - Loamy and Clayey Freshwater Floodplain

Marshes and Swamps Other vegetative classification: Loamy and clayey soils on stream terraces, flood plains, or in depressions (G155XB345FL), Freshwater Marshes and Ponds

(R154XY010FL)

Hydric soil rating: Yes

Okeelanta Percent of map unit: 1 percent Landform: Depressions on marine terraces Landform position (three-dimensional): Tread, dip Down-slope shape: Concave Across-slope shape: Concave Ecological site: R155XY100FL - Organic Freshwater Isolated Marshes and

Swamps Other vegetative classification: Organic soils in depressions and on flood plains

(G155XB645FL), Freshwater Marshes and Ponds (R155XY010FL) Hydric soil rating: Yes

JACKSON GEOTECHNICAL

ENGINEERING, LLC

Consulting Geotechnical Engineers

Serving North and Central Florida and South Georgia Since 1994

PRELIMINARY REPORT OF GEOTECHNICAL EXPLORATION

PUTNAM COUNTY, FLORIDA

JGE PROJECT NO. 24-539.1

Prepared for:

Maverick Engineering

10 Willow Winds Parkway

St. Johns, Florida 32259

Prepared by:

Jackson Geotechnical Engineering

164 Plaza Del Rio Drive

St. Augustine, Florida 32084

Phone: 904-252-2292

July 2, 2024

JACKSON GEOTECHNICAL ENGINEERING, LLC

July 2, 2024

Maverick Engineering

10 Willow Winds Parkway

St. Johns, Florida 32259

Att: Mr. Jeremy Calloway, P.E.

Report of Geotechnical Exploration and Engineering Services

Dunns Creek Boat Ramp

Putnam County, Florida

JGE Project No. 24-539.1

Dear Mr. Calloway:

As requested, Jackson Geotechnical Engineering has completed a geotechnical exploration for the subject project. The exploration was performed to evaluate the general subsurface conditions within the proposed construction areas, and to provide guidelines to facilitate foundation support, earthwork preparation, paving and drainage design.

We appreciate this opportunity to be of service as your geotechnical consultant on this phase of the project. Please contact us if you have any questions, or if we may be of any further service.

Sincerely:

Jackson Geotechnical Engineering, LLC.

Jeff S. Jackson, P.E.

Licensed, Florida 51979

Table of Contents

1.0 PROJECT INFORMATION

1.1 SITE LOCATION AND DESCRIPTION

1.2 PROJECT DESCRIPTION

2.0 FIELD EXPLORATION

2.1 SOIL BORINGS

2.2 RELATIVELY UNDISTURBED SOIL SAMPLES

3.0 LABORATORY TESTING

3.1 INDEX TESTING

3.2 PERMEABILITY TESTING

4.0 GENERAL SUBSURFACE CONDITIONS

4.1 GENERAL SOIL PROFILE

4.2 GROUNDWATER LEVEL

5.0 BUILDING AREA RECOMMENDATIONS

5.1 GENERAL

5.2 BUILDING FOUNDATIONS

5.2.1 BEARING PRESSURE

5.2.2 FOUNDATION SIZE

5.2.3 BEARING DEPTH

5.2.4 BEARING MATERIAL

5.2.5 SETTLEMENT ESTIMATES

5.3 SITE PREPARATION FOR SHALLOW FOUNDATIONS

6.0 GRAVEL AREAS

6.1 GENERAL

6.2 SITE PREPARATION FOR PARKING AND DRIVE AREAS

6.2.1 GROUNDWATER SEPARATION

7.0 DRY RETENTION RECOVERY PARAMETERS

8.0 LIMITATIONS

APPENDIX A ................................................................................................................................. I BORING LOCATION PLAN ........................................................................................................................................... I SUBSURFACE PROFILES ............................................................................................................................................. I

APPENDIX B ............................................................................................................................... II KEY TO SOIL CLASSIFICATION ................................................................................................................................. II FIELD AND LABORATORY TEST PROCEDURES ...................................................................................................... II

Project No. 24-539 1 July 2, 2024

1.0 PROJECT INFORMATION

1.1 Site Location and Description

The site for the subject project is located within the southwestern quadrant of the intersection of U.S. Highway 17 and Magnolia Trail in Putnam County, Florida. The site is partially wooded. Based on visual observation, the topography of the site appears to slope gently downward towards the west. Single-family residential structures are located on the adjacent parcels abutting the western property boundary. Existing concrete slabs were noted in various portions of the property.

1.2 Project Description

Project information was provided during correspondence with you, and Messrs. Tisdale and Sowell of your office. We were provided with a copy of a Conceptual Site Plan for the subject project. The requested boring locations were shown on the provided plan.

We understand the proposed project will consist of constructing a boat ramp facility at the subject site. In general, the construction will include a restroom building, three stormwater bio-infiltration areas, parking and drive areas.

The proposed structure will enclose one level of floor space. It is anticipated the structural components of the proposed building will include timber framing or concrete-masonry-units (CMU). The floor slab will be constructed of soil-supported concrete. Detailed structural loading information was not provided; therefore, we have assumed maximum wall and column foundation loads will not exceed 2.5 klf and 30 kips, respectively.

Parking and drive areas will be constructed of gravel over improved subgrade. The stormwater system will include bio-infiltration landscaped islands. We have assumed maximum fill heights will vary roughly between one to three feet.

2.0 FIELD EXPLORATION

2.1 Soil Borings

To explore the subsurface conditions within the area of the proposed building, 1 Standard

Penetration Test (SPT) boring (B-1) was conducted to a depth of 15 feet below existing grade. Within the area of the proposed stormwater facilities, we performed 4 SPT borings

(PB-1 through PB-4) to a depth of 10 feet each below the existing ground surface. Five auger borings (A-1 through A-5) were performed to a depth of 6 feet each within the proposed gravel areas. The borings were located by referencing existing site features, utilizing GPS methods, and should be considered accurate to the degree implied by the methods utilized. The SPT and auger borings were conducted in accordance with ASTM

D 1586, and ASTM D 1452, respectively. The locations of the borings, and the subsurface conditions encountered at each boring location, are presented in Appendix A on the Boring

Location Plan and Subsurface Profiles, respectively.

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2.2 Relatively Undisturbed Soil Samples

A total of 8 relatively undisturbed soil samples were obtained at the locations of Borings

PB-1 through PB-4 for the purpose of permeability (hydraulic conductivity) testing. The soil samples were obtained using thin-walled tube sampling techniques (Shelby tube). The

Shelby tubes were transported to our laboratory for permeability testing.

3.0 LABORATORY TESTING

3.1 Index Testing

Soil samples recovered during the field exploration were visually classified in accordance with ASTM D 2488. The results of the classification testing are presented on the

Subsurface Profiles in Appendix A.

3.2 Permeability Testing

Permeability (hydraulic conductivity) tests were conducted on the undisturbed soil samples to estimate the coefficients of permeability of the appropriate soil layers. The coefficient of permeability is a measure of a soil’s ability to transmit water under hydraulic loading conditions. It typically is a required input parameter for groundwater modeling, such as dry pond recoveries, background seepage, etc. The laboratory permeability test is typically conducted by placing the undisturbed soil sample in a permeameter, and while in the permeameter, the soil sample is subjected to differential hydraulic loading over a period of time. The volume of water that is transmitted through the soil sample is recorded, and along with the known hydraulic loading conditions, Darcy’s law is utilized to calculate the coefficient of permeability. The coefficients of permeability are shown on the Subsurface

Profiles at the depths of which the soil samples were obtained.

4.0 GENERAL SUBSURFACE CONDITIONS

4.1 General Soil Profile

The boring locations and general subsurface conditions that were encountered are presented on the Boring Location Plan and Subsurface Profiles. When reviewing these records, it should be understood the soil conditions may change significantly between the boring locations. The following discussion summarizes the soil conditions encountered.

In general, the SPT borings (B-1, PB-1 through PB-4) encountered loose to medium dense fine sand (SP) throughout the 10 to 15-foot exploration depths. As an exception, layers of medium dense to dense fine sand with silt (SP-SM) were present between the upper and lower depth ranges of 3 to 9 feet at the locations of Borings PB-1 through PB-4. Some layers of the fine sand with silt exhibited cementation.

Project No. 24-539 3 July 2, 2024

The auger borings (A-1 through A-5) encountered fine sand (SP) and fine sand with silt

(SP-SM) thought the 6-foot exploration depths. Layers of fine sand with silt exhibiting cementation were noted at various locations. As an exception to the above, Boring A-2 could only be performed to a depth of 4 feet due to impenetrable conditions.

4.2 Groundwater Level

The groundwater level was measured at the boring locations, 48+ hours subsequent to boring completion, at depths varying between 3.2 and 4.9 feet below existing grade. The groundwater level was not encountered within the 4-foot exploration depth of Boring A-2.

The depth of the groundwater level encountered at each boring location is presented on the

Subsurface Profiles. It is noted the borings were performed during a relatively dry period.

The groundwater table will fluctuate depending on seasonal variations, adjacent construction, surface water runoff, etc. Our estimates of the normal seasonal-high groundwater level at each applicable boring location are presented on the Subsurface

Profiles in Appendix A. Our estimates are based on the results of the soil borings, review of available published literature, and information provided for this study. Should rainfall intensity exceed normal quantities, or should other variables that affect the seasonal high groundwater level be altered, the groundwater profile at the site could change significantly.

5.0 BUILDING AREA RECOMMENDATIONS

5.1 General

The following recommendations are made based upon a review of the attached soil test data, our understanding of the proposed construction, and experience with similar projects and subsurface conditions. If the structural loads, construction locations, or grading information change from those discussed previously, we request the opportunity to review and possibly amend our recommendations with respect to those changes.

Please report to us any conditions encountered during construction that were not observed during the performance of the borings. We will review, and provide additional evaluation, as required.

5.2 Building Foundations

Based on the results of the subsurface exploration, we consider the subsurface conditions at the site favorable for support of the proposed structure when constructed on a properly designed shallow foundation system. Provided the soils are prepared in accordance with the Site Preparation Section of this report, the following parameters may be used for foundation design.

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5.2.1 Bearing Pressure

The maximum allowable net soil bearing pressure for shallow foundations should not exceed 2,500 pounds per square foot (psf). Net bearing pressure is defined as the soil bearing pressure at the base of the foundation in excess of the natural overburden pressure.

The foundations should be designed based upon the maximum load that could be imposed by all loading conditions.

5.2.2 Foundation Size

The minimum widths recommended for any isolated column footing and continuous wall footings are 24 inches and 18 inches, respectively. Even though the maximum allowable soil bearing pressure may not be achieved, these width recommendations should control the size of the foundations.

5.2.3 Bearing Depth

The exterior foundations should bear at a depth of at least 12 inches below the exterior final grades and the interior footings should bear at a depth of at least 12 inches below the finish floor elevation to provide confinement to the bearing level soils. We recommend stormwater and surface water be diverted away from the building exterior, both during and after construction, to reduce the possibility of erosion adjacent to the exterior footings.

5.2.4 Bearing Material

The foundations may bear on either the compacted suitable in-place natural soils or compacted structural fill. The bearing level soils, after compaction, should exhibit densities of at least 95 percent of the maximum dry density as determined by ASTM D

1557 (Modified Proctor), to the depth described subsequently in the Site Preparation section of the report. In addition to compaction, the bearing soils must exhibit stability and be free of “pumping” conditions.

5.2.5 Settlement Estimates

Post-construction settlement of the proposed structure will be influenced by several interrelated factors, such as (1) subsurface stratification and strength/compressibility characteristics of the bearing soils; (2) footing size, bearing level, applied loads, and resulting bearing pressures beneath the foundations; (3) site preparation and earthwork construction techniques used by the contractor, and (4) external factors, including but not limited to vibration from offsite sources and groundwater fluctuations beyond those normally anticipated for the naturally-occurring site and soil conditions which are present.

Our settlement estimates for the structure are based upon the use of successful adherence to the site preparation recommendations presented later in this report. Any deviation from these recommendations could result in an increase in the estimated post-construction settlement of the structure.

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Due to the sandy nature of the surficial soils, following the compaction operations, we expect a significant portion of settlement to be elastic in nature. This settlement is expected to occur relatively quickly, upon application of the loads, during and immediately following construction. Using the recommended maximum bearing pressure, the assumed maximum structural loads presented in this report, and the field and laboratory test data which we have correlated to the strength and compressibility characteristics of the subsurface soils, we estimate the total settlements of the structure to be approximately one-half inch or less.

Differential settlement results from differences in applied bearing pressures and the variations in the compressibility characteristics of the subsurface soils. Based on the subsurface conditions as determined by the borings, and the recommended earthwork preparation, it is anticipated that differential settlements will be within tolerable limits.

5.3 Site Preparation for Shallow Foundations

We recommend the following site preparation guidelines for the building area:

1. Prior to construction, the location of existing underground utility lines within the construction area should be established. Provisions should then be made to relocate interfering utilities to appropriate locations. It should be noted that if underground pipes are not properly removed or plugged, they may serve as conduits for subsurface erosion which may subsequently lead to excessive settlement of the overlying structure.

2. Implement temporary groundwater control measures, as required. The groundwater should be maintained at least two feet below the depth of excavation required and two feet below compacted surfaces. Temporary groundwater control measures should be the responsibility of the contractor.

3. Strip the proposed construction limits of all grass, roots, topsoil, slab/building debris, and other potentially deleterious materials from within, and extending at least 5 feet beyond, the perimeter of the proposed structure. Expect initial clearing and grubbing to average depths of approximately 9 to 15 inches. During stripping operations, roots with a diameter greater than 0.5 inches, stumps, and roots in a concentrated state, should be completely removed.

4. Compact the exposed surface using a vibratory drum roller having a minimum static, at-drum weight of 5 tons and a drum diameter of at least 4 feet. It is recommended that repeated passes of the roller be made in one direction, followed by repeated passes of the roller in a direction perpendicular to the initial passes. The upper one foot of soil below the exposed surface (after stripping and grubbing) within the building area should be improved to achieve a minimum compaction requirement of 95% of the Modified Proctor

Test (ASTM D 1557). We recommend the soils, at the time of compaction, exhibit

Project No. 24-539 6 July 2, 2024 moisture contents within 2 percent of the optimum moisture content as determined by the

Modified Proctor Test (ASTM D 1557).

The use of the vibratory mechanism on the roller should be used with caution when compacting the exposed surface and the initial lifts of fill in order to avoid drawing the groundwater to the surface and causing soil instability (pumping) conditions. If vibration is drawing water to the exposed surface, the vibratory mechanism should be turned off and the roller should be operated in static mode.

Should the soils experience pumping and soil strength loss during the compaction operations, compaction work should be immediately terminated and (1) the disturbed soils removed and backfilled with dry structural fill soils which are then compacted, or (2) the excess moisture content within the disturbed soils allowed to dissipate before recompacting.

Care should be exercised to avoid damaging any nearby structures while the compaction operation is underway. Prior to commencing compaction, occupants of adjacent structures should be notified and the existing conditions of the structures be documented with photographs and survey (if deemed necessary). Compaction should cease if deemed detrimental to adjacent structures and Jackson Geotechnical Engineering should be contacted immediately. It is recommended the vibratory roller remain a minimum of 75 feet from existing structures. Within this zone, use of a vibratory roller operating in the static mode (vibration turned off) is recommended.

5. Test the compacted surface for density at a minimum of two locations within the building area.

6. Place structural fill in loose lifts not exceeding a thickness of 8 to 12 inches and compact until finished subgrade is achieved. Structural fill and backfill is typically defined as non-plastic, inorganic, granular soil having less than 12 percent material passing the No. 200 mesh sieve and containing less than 4 percent organic material. Typically, the material should exhibit moisture contents within 2 percent of the Modified Proctor optimum moisture content (ASTM D 1557) during the compaction operations. Compaction should continue until densities of at least 95 percent of the Modified Proctor maximum dry density (ASTM D 1557) have been achieved within each foot of the compacted structural fill.

7. Perform density tests within each lift of fill at a minimum of two locations within the building area.

8. Excavate, compact and test footing excavations for density to a depth of one foot below bearing level. We recommend that you test one out of every two column footings and perform one test per every 50 linear feet of wall footing (minimum of two locations).

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Compaction operations in confined areas, such as footing excavations, can best be performed with a lightweight vibratory sled or other hand-held compaction equipment.

6.0 GRAVEL AREAS

6.1 General

We understand the subject project will utilize gravel over improved subgrade in the parking and drive areas. In the following sections, we have presented our recommendations to guide site preparation in the parking and drive areas.

To reduce long-term maintenance associated with the gravel, consideration should be given to implementing a woven geosynthetic fabric, such as TC Mirafi Rs280i. The utilization of the geotextile is discussed in Section 6.2., Item (7), below.

6.2 Site Preparation for Parking and Drive Areas

We recommend the following site preparation guidelines for the gravel laydown area:

1. Implement temporary groundwater control measures, as required. The groundwater should be maintained at least two feet below the depth of excavation required and two feet below compacted surfaces.