Stop the Sand Mine

Updated Issue

 

A Comprehensive Plan change submitted to Citrus County would like to change approximately 322.8 acres from Agricultural to Extractive for a new “sand mine.”The applicant prefers to call the mining area a borrow pit. Both terms are used in the application so we will use them synonymously. 

 

“Borrow Pit” sounds simple but it gets complicated fast when dealing with the safety of our water. Just the very simple process of excavation introduces oxygen into the sand which can result in disastrous effects on the aquifer and springs.

 

The Impact of Oxygen Introduction

 

The introduction of oxygen through excavation, by exposing saturated zones to air, can significantly alter aquifer chemistry. This is particularly relevant in unconfined aquifers, which already have some atmospheric exchange but may have reducing conditions at depth. The introduction of oxygen during excavation in this scenario is a given, not just assumed, due to the physical process of exposing groundwater to air.

 

Conclusion

Something as simple as Oxygen introduction during excavation in this karst-sensitive area will likely degrade groundwater quality by oxidizing reduced species, dissolving limestone, and releasing nutrients, with amplified risks due to rapid flow through karst conduits. Springs, such as those in Citrus County, are particularly vulnerable to water quality degradation and flow alterations.

When you then take the depth of excavation, the high water table, and the sandy soil profile, the introduction of oxygen during  excavation is a given, not assumed. This is due to the physical process of exposing groundwater to atmospheric oxygen, amplified by the large scale and permeability of the soils. Supporting research and expert opinions confirm that such disturbances will increase dissolved oxygen levels, making it an inevitable outcome of the project.

It is our aquifer and our springs that drive the  economy here in Citrus County. Please let’s all protect it.

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The following details the potential effects of Oxygen Introduction

 

Oxidation Reactions: Oxygen can oxidize reduced species in the aquifer, such as organic matter, iron, manganese, or sulfides. For example:

•  Iron and manganese, typically mobilized under reducing conditions, may precipitate under oxidizing conditions, potentially clogging pores or affecting water quality.

•  Arsenic, if present, can be mobilized under oxidizing conditions, especially in sandy or limestone matrices with specific mineralogy.

•  Organic matter oxidation can release nutrients like nitrogen and phosphorus, potentially leading to eutrophication if discharged to surface waters.

 

 

 Limestone Dissolution: In areas with limestone, oxygen, combined with carbon dioxide from the atmosphere or soil, can form carbonic acid (H₂CO₃), which dissolves calcium carbonate (CaCO₃). This process, though slow, can increase porosity and permeability, potentially altering flow paths and increasing water hardness (due to calcium and magnesium ions). The reaction is:

 

Redox Condition Changes: The aquifer, being unconfined, may already have oxygenated zones near the surface, but deeper zones (within 8-25 feet) could be less oxygenated. Excavation can enhance oxygenation, shifting the redox environment from reducing to oxidizing, which can mobilize or immobilize certain elements. For instance, the East Homosassa well site report showed high chloride and sulfate at 120-130 ft bls, suggesting reducing conditions at depth, which excavation could alter if extended deeper.

 

Effects of Excavation on the Aquifer

 

Types of Impacts

 

1. Lowering of the water table.    How this happens-Excavation removes sand holding water, potentially lowering the water table. With the loss of sand there is reduced storage capacity and this has a potential to lower the water table significantly.                                                                            We believe this will happen because: The applicant's geological study states, “The excavation activities will intersect the water table of the surficial aquifer…” meaning much of the sand would be saturated with water and with its removal there will be a loss of water going to the aquifer.                                   

2. Altered Flow Paths.    How this happens-The sand removal changes groundwater flow direction, diverting water towards the excavation site creating a new path. This disrupts discharge and recharge and may create new flow paths through Karst conduits.                                                                  We believe this will happen because: The Stormwater Pollution Plan for this application states, “All of the Stormwater runoff from the active mining area is directed back into the borrow pit excavation.”      

3. Increased Infiltration.    How this happens-The pit creates depressions collecting surface water, this then increases aquifer recharge. We believe this is a given because with a pit 150 acres in size and excavation being dug 18-20 feet deep as the applicant’s representative stated at the quasi-judicial meeting 6/27. This gigantic pit is one big depression, this entire area will be collecting surface water as that is the plan for all water runoff.                                                                                         

4. Oxygen Introduction.  As established, oxygen introduction is a given due to excavation intersecting the water table, exposing groundwater to atmospheric oxygen through direct exposure and dewatering. Sandy soils facilitate oxygen diffusion, while karst features enhance connectivity, potentially spreading effects to springs and the broader aquifer (Oxygenation of aquifers with fluctuating water table).Contamination Risk. Increased risk of pollutant inflation, degrading water quality.                                                                                                                                   

5. Physical Disturbance     Mixing layers then creates preferential flow paths, altering aquifer structure. This again seems to be a given as the terrain is being altered from a sandy hill to a deep pit in the ground.

 

Known Facts Increasing Risk to Aquifer

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Facts that were learned in this research and assessment show us this specific area or borrow pit location can alter groundwater flow significantly and evidence leans towards oxygen introduction causing chemical changes, potentially releasing contaminants into the aquifer.

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1. The Location: Sections 11 & 12, Township 18 South, Range 18 East, Citrus County, Florida 

 

2. “The project is located in a sensitive Karst area and a historic sinkhole is located onsite.” (Please look at our sinkhole map for this area)

 

3. The project involves excavating to a depth of 18-20 feet and 14 borings done show water at 7-23 feet, with 10 borings 16 feet or less. It seem clear

 

4. For this research we used 203 acres for the pit area and only 3.5 million cubic yards of sand vs. the 150 acre pit and 4.5 million cubic yards previously stated. Obviously with a small pit the risk to the aquifer and spring increases and the same if there was an increase in the amount of sand. Keep in mine the bottom line is if 322.8 acres is labeled as extractive

322.8 acres may be used for this borrow pit.

 

5. Boring readings suggest, “…the two aquifers are in hydraulic communication. This notion is supported by the borings that penetrated sand and then limestone, with no intervening clay or low permeability soils.

 

6. A karst landscape is a geological term describing a type of terrain formed by the dissolution of soluble rocks, such as limestone, dolomite or gypsum by water. Karst landscapes are characterized by  springs, underground drainage systems and sinkholes. 

 

7. In Florida, where water resources are critical, sand mining can contaminate aquifers and springs, impacting drinking water quality and agricultural irrigation. The Florida Springs and Aquifer Protection Act was put in place for these reasons.  Crystal River is part of the Springs Coast Watershed and Crystal River/Kings Bay spring group is listed as one of the major five springs. Our local Crystal River Springs were named Outstanding by the Florida Legislature and they are a designated priority water body or in other words called a Priority Focus Area! 

 

“A   is defined as the areas of a basin where the Floridan aquifer is generally and most vulnerable to pollutant inputs and where there is a known connectivity between groundwater pathways and an outstanding Florida spring. The Priority Focus Area provides a guide for focusing strategies where science suggests these efforts will best benefit the spring.”3 This information was provided from Citrus County Geographic Information Systems address lookup specifically for the sand mine location. Our Citrus County board members are responsible stakeholders of this vulnerable location and they are required to follow the Basin Management Action Plan.

 

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Key Citations

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•  Oxygenation of aquifers with fluctuating water table study

•  Can groundwater have dissolved oxygen research

•  Dissolved Oxygen and Water USGS page

•  Oxygen Content overview ScienceDirect

•  Soil physical properties and processes manual

•  Floridan aquifer system | U.S. Geological Survey

•  Geohydrologic Data | WaterMatters.org

•  Oxygenation of aquifers with fluctuating water table

•  Influence of Stone Quarries on Groundwater Quality | ScienceDirect

•  Oxygen Content - an overview | ScienceDirect Topics

•  Hydraulic Impacts of Quarries and Gravel Pits | Minnesota DNR

•  Construction with Dewatering FAQ | Florida DEP

•  State of Florida Erosion and Sediment Control Manual

•  Springs | WaterMatters.org

•  Karst Aquifers | U.S. Geological Survey

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