ML25170A028
| ML25170A028 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 06/18/2025 |
| From: | ADP CR3 |
| To: | Office of Nuclear Material Safety and Safeguards, Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML25170A017 | List: |
| References | |
| 3F0625-01 | |
| Download: ML25170A028 (1) | |
Text
ADP CR3, LLC 15760 West Power Line Street l Crystal River, FL 34428 ADP CR3, LLC DOCKET NUMBER 50-302 / DOCKET NUMBER 72-1035 LICENSE NUMBER DPR - 72 ATTACHMENT 8 TSD - Groundwater Well and Withdrawal Permit Limits Under the Florida Department of Environmental Protection Regulations 3F0625-01 / Attachment 8 A1
HALEY & ALDRICH, INC.
75 Washington Avenue Suite 1A Portland, ME 04101 207.482.4600 www.haleyaldrich.com TECHNICAL SUPPORT DOCUMENT 21 March 2024 File No. 134300-014 TO:
ADP CR3 John Jernigan, D&D Licensing Manager FROM:
Haley & Aldrich, Inc.
Miles van Noordennen, Senior Technical Specialist Nadia Glucksberg, P.G., Principal Hydrogeologist
SUBJECT:
Groundwater Well and Withdrawal Permit Limits Under the Florida Department of Environmental Protection Regulations To support the License Termination Plan (LTP) for the ADP Crystal River Nuclear Plant Unit 3 (ADP CR3) decommissioning project, Haley & Aldrich, Inc. (Haley & Aldrich) has been asked to provide a selection of geological and hydrogeological parameters for the RESRAD inputs. These have been provided and documented in the Technical Support Document entitled Development of Site-Specific Values for RESRAD Hydrogeological and Hydrological Parameters, and the values are also reflected in Section 2 of the LTP.
During the development of the conceptual site model (CSM), we noted that the modeled horizontal hydraulic conductivities of the underlying shallow limestone units are very high (above 100,000 meters per year [0.317 centimeters per second]) and reflect the dissolution voids common in karst hydrogeological regimes.1 Because of the physical setting, we expanded our evaluation and developed a two-dimensional (2D) model to evaluate the potential of saltwater intrusion and potential coning.
Based on the modeling effort, saltwater intrusion impacts the well as soon as 1,000 days for the resident farmer scenario and at approximately 6,000 days if only a single dwelling was on the property. As noted in the audit meeting held at the Site during the week of 4 December 2023, the Nuclear Regulatory Commission (NRC) commented that saltwater intrusion may negate the ability for a Resident Farmer or single household to use this well as a potable water source. The NRC audit team noted that they would also like to see documentation from the Florida Department of Environmental Protection (FDEP) that limited or banned the use of groundwater wells at the Site.
1 GHS, 2017. CR3 Groundwater Flow Study Summary Report to DUKE Energy Florida, 26 April.
3F0625-01 / Attachment 8 / Page 1 of 23
ADP CR3 21 March 2024 Page 2 GENERAL WELL PLACEMENT IN CITRUS COUNTY Groundwater wells in the region are typically installed between 40 to 60 feet below ground surface, within the Upper Floridian Aquifer. We have assumed that for the Resident Farmer scenario, the required yield would be up to 7,000 cubic meters per year or 5,066 gallons per day, as provided in the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), and with that yield, an aquifer withdrawal or Water Use Permit (WUP) would be required from FDEP.
It should be noted that due to the coastal geology in Citrus County, and as observed at ADP CR3, water withdrawal wells are rarely approved in areas west of Highway 192. This is further supported by the background data set that reports salinity in site monitoring wells at levels above the United States Environmental Protection Agencys Secondary Maximum Contaminant Level (MCL)3. Additionally, and per the FDEPs database, there are several monitoring wells in the area that are used for groundwater quality measurements (in addition to the wells installed by Duke and ADP CR3); however, the only production wells in the area that are used for both Dukes potable water as well as commercial uses, are located on the east side of Highway 19. While there is one production well located on the west side of Highway 19, it is situated on the eastern side of the property, more than three miles east of ADP CR3.
REGULATORY OVERVIEW Groundwater at ADP CR3, and specifically the future use of groundwater at ADP CR3, is regulated by both the FDEP and the Southwest Florida Water Management District (SWFWMD).
FDEP regulates groundwater quality; however, because saltwater, and specifically salt, is a secondary drinking water contaminant, it is not regulated as a primary contaminant and exceedance of the EPA secondary MCLs are related to aesthetics and not public health. Therefore, wells that are installed into brackish water or that withdraw brackish and saline water are not prohibited. Consequently, saltwater wells are permitted, as the water could be treated, or the salt may be present at levels that are acceptable for the intended use; however, FDEP cannot issue a permit for a well with good quality water that will then become brackish or saline from pumping.
Water withdrawal is regulated under the SWFWMD, and the withdrawal must comply with the following Florida Administrative Code (FAC) Sections:
40D-2.301 - Conditions for Issuance of Permits.
40D-3.045 - Water Use Permit Required.
40D-3.301 - Conditions for Issuance of Permits.
40D-3.505 - Location.
2 Environmental Data Portal l WaterMatters.org (state.fl.us). Accessed on 22 January 2024.
3 Haley & Aldrich, Inc. Haley & Aldrich, Inc. Report entitled: Supplemental Site Investigation Report, Crystal River Nuclear Plant Unit 3, FDEP Site NO. ERIC_15353, Crytal River, Florida, dated February 2023.
3F0625-01 / Attachment 8 / Page 2 of 23
ADP CR3 21 March 2024 Page 3 These regulations (provided in Attachment 1) state that wells that will be actively pumped with groundwater extracted for industrial or public use must obtain a WUP. For approval, the applicant must provide Reasonable Assurance that the criteria are met.
The modeling results below do not meet the following criteria: 40D-2.301(2)(g)3 and 40D-2.301(2)(g)5.
These stipulate that the withdrawal of groundwater will not cause harmful saline water intrusion or harmful upconing and will not otherwise cause harmful hydrogeologic alterations to the water resources of the area, respectfully. A copy of these regulatory sections is provided in Attachment 1.
This requirement is further supported by 40D-3.301(1)(f), where the regulations require that the proposed water well shall not adversely impact the water resource. Saline intrusion, as noted above, is considered an adverse impact.
Finally, on 24 January 2024, we discussed the potential permitting scenario for the resident famer scenario with Mr. Bob Thompson, SWFWMDs Water Use Permit Bureau Supervisor. He confirmed that if saltwater intrusion was likely to occur, then the well use permit would be denied. On 28 February 2024 Mr. Thomson also confirmed that the permit for the single dwelling would also be rejected to potential and estimated impacts to groundwater quality.
NUREG-1757 V2, SECTION 5.5.2 CONSIDERATIONS In addition to saltwater intrusion, there are other regulatory considerations that would limit future groundwater uses on site, which include the following:
Environmental site closure will be achieved following FDEP Commercial/Industrial criteria.
Therefore, future residential use will be restricted and may require land use or deed restrictions placed on the property.
Groundwater contains naturally occurring metals that exceed FDEP Cleanup Target Levels (CTLs). Site-specific background values have been accepted by FDEP and therefore become the accepted site-specific CTLs4. Therefore, the elevated background concentrations of inorganics in groundwater will not require corrective actions. Should future use include using groundwater for a potable source, it would require treatment the end-user to treat the water prior to use.
These accepted valued include the following:
Table 1. Background Concentrations Contaminant Units Shallow Zone Intermediate Zone Groundwater CTL Arsenic ug/L 12.64 20.25 10 Iron ug/L 3,806 7,072 300 Manganese ug/L 867 206 50 Sodium ug/L 1,613,000 7,520,000 160,000 4 FDEP, 2024. Comments provided by John Sego, PG on the Haley & Aldrich Report entitled: Phase II Supplemental Site Investigation Report, and Underground Storage Tank Closure Report. 18 March 2024.
3F0625-01 / Attachment 8 / Page 3 of 23
ADP CR3 21 March 2024 Page 4 Due to the brackish shallow groundwater and low groundwater quality, wells are typically not installed in this area, as demonstrated by the distribution of potable wells in the county.
Furthermore, it is anticipated with climate change and the associated sea level rise predictions, that near-shoreline groundwater at the site will likely continue to be saline and water quality would degrade further.
The existing cutoff wall would lessen the achievable yield of a production well within the berm area.
MODELING RESULTS The numerical model SEAWAT (Langevin et al., 2008)5 was used for the saltwater intrusion modeling effort. SEAWAT is a coupled version of MODFLOW and MT3DMS designed to simulate variable density and saturated groundwater flow; it is routinely applied to saltwater intrusion studies. A 2D cross-section was constructed to model a representative north-south cross-section at the ADP CR3 Site. 2D cross-section models are routinely used to simulate landward migration of saltwater from an ocean or sea boundary toward an inland boundary. In this study, the 2D model boundaries represent the intake canal and discharge canal.
SEAWAT model simulations were conducted to evaluate the salinity at the extraction well and the potential for intrusion of saltwater from the intake and discharge canal boundaries. Model simulation time was set to a sufficiently long period for the evaluation. For the Resident Farmer scenario, the simulation time was set to 10,000 days. For the Single-Family Household scenario, the simulation time was set to 100,000 days. It is noted here that the simulation times are less than the Nuclear Regulatory Commissions requirement to evaluate conditions for 1,000 years; however, with the estimated breakthrough, the simulation time periods are appropriate for this modeling effort.
The modeling summary in Attachment 2 demonstrates that the saltwater profile for the Resident Farmer scenario at the end of simulation impacts groundwater quality and causes saltwater intrusion at irrigation well. It also shows a similar result for the saltwater profile for the Single-Family Household scenario, only with less volume withdrawn from the groundwater, the impacts are seen much later, but impacts are still anticipated. Based on the model results for the Resident Farmer scenario, salinity at the irrigation well increases to a value exceeding the threshold of 0.45 ppt after approximately 1,900 days in layer 3, while the average salinity exceeds the threshold at approximately 2,700 days. For the Single-Family Household scenario, salinity at the domestic well increases to a value exceeding the threshold after approximately 6,000 days.
The above results indicate that both the irrigation well pumping and single residents well use will lead to saltwater intrusion and an exceedance of salinity in the pumped water over time.
5 Langevin, C.D., D.T. Thorne, Jr., A.M. Dausman, M.S. Sukop, and W. Guo, 2008. SEAWAT Version 4: A Computer Program for Simulation of Multi-Species Solute and Heat Transport. Accessed at:
https://pubs.usgs.gov/tm/tm6a22/pdf/tm6A22.pdf.
3F0625-01 / Attachment 8 / Page 4 of 23
ADP CR3 21 March 2024 Page 5 CLOSING Based on our hydrogeological CSM, as well as the numerical modeling completed to better evaluate impacts, we have estimated that saltwater intrusion would be encountered within 50 to 100 days. This would not only limit the uses for the Residential Farmer scenario, but also it does not meet the Reasonable Assurance Criteria required to demonstrate regulatory compliance. More specifically, this shows that up-coning or intrusion would impact the aquifer. With these predicted impacts, induced by the pumping/water extraction, the SWFWMD would deny the permit. Therefore, by regulation, groundwater extraction wells are not permitted in the footprint of ADP CR3; therefore, the groundwater pathway is not applicable for developing derived concentration guideline levels (DCGLs).
Enclosures:
- Regulatory Citations - Groundwater Model Summary 3F0625-01 / Attachment 8 / Page 5 of 23
ATTACHMENT 1 Regulatory Citations 3F0625-01 / Attachment 8 / Page 6 of 23
40D-2.301 Conditions for Issuance of Permits.
(1) To obtain an individual WUP, renewal, or modification, an applicant must provide reasonable assurance that the proposed consumptive use of water, on an individual and cumulative basis:
(a) Is a reasonable-beneficial use; (b) Will not interfere with any presently existing legal use of water; and (c) Is consistent with the public interest.
(2) In order to provide reasonable assurances that the consumptive use is reasonable-beneficial, an applicant shall demonstrate that the consumptive use:
(a) Is a quantity that is necessary for economic and efficient use; (b) Is for a purpose and occurs in a manner that is both reasonable and consistent with the public interest; (c) Will utilize a water source that is suitable for the consumptive use; (d) Will utilize a water source that is capable of producing the requested amount; (e) Except when the use is for human food preparation or direct human consumption, will utilize the lowest quality water source that is suitable for the purpose and is technically, environmentally, and economically feasible; (f) Will not cause harm to existing offsite land uses resulting from hydrologic alterations; (g) Will not cause harm to the water resources of the area in any of the following ways:
- 1. Will not cause harmful water quality impacts to the water source resulting from the withdrawal or diversion;
- 2. Will not cause harmful water quality impacts from dewatering discharge to receiving waters;
- 3. Will not cause harmful saline water intrusion or harmful upconing;
- 4. Will not cause harmful hydrologic alterations to natural systems, including wetlands or other surface waters; and
- 5. Will not otherwise cause harmful hydrologic alterations to the water resources of the area.
(h) Is in accordance with any minimum flow or level and implementation strategy established pursuant to Sections 373.042 and 373.0421, F.S.; and (i) Will not use water reserved pursuant to Section 373.223(4), F.S.
(3) For projects that require both an ERP and an individual WUP, an application for an ERP must be deemed complete prior to issuance of the individual WUP when the design of the surface water management system can affect the quantities developed from the project site and the quantities needed to supply project water demands. The applicant may submit an application for a Conceptual ERP to satisfy this requirement, provided that the application contains information from which supplemental irrigation demands, potable water demands, other water use demands, and water supply quantities derived from the surface water management system can be calculated. Otherwise, the applicant shall submit an application for an Individual or General ERP. Phosphate mining projects are not required to have complete ERPs prior to WUP issuance. If the District determines that a permit application involves an area where there are water resource problems and due to the quantity, type or location of the proposed withdrawal it is unlikely that a water use permit will be issued, the requirement for a complete ERP application shall be waived by the District. Where such waivers are granted, and if a WUP is issued, it shall specify that a well construction permit will not be issued and that withdrawals cannot commence until the appropriate ERP is issued.
(4) The standards and criteria set forth in the WUP Applicants Handbook Part B,
(rev.
10/15),
(https://www.flrules.org/Gateway/reference.asp?No=Ref-05856), shall be used to provide the reasonable assurances required in subsections 40D-2.301(1) and (2), F.A.C.
Rulemaking Authority 373.044, 373.113, 373.171 FS. Law Implemented 373.219, 373.223, 373.229 FS. History-New 10-5-74, Amended 12-31-74, 2-6-78, 7-5-78, Formerly 16J-2.11, 16J-2.111, Amended 1-25-81, 10-1-89, 2-10-93, 8-3-00, 4-14-02, 1-1-07, 5-26-10, 6-30-10, 5-19-14, 9-29-15.
3F0625-01 / Attachment 8 / Page 7 of 23
40D-3.045 Water Use Permit Required.
(1) Permits for construction, repair, modification or abandonment of wells for which an individual water use permit is required under Chapter 40D-2, F.A.C., shall not be issued prior to issuance of the water use permit authorizing such water use withdrawals.
(2) Notwithstanding the provisions of subsection (1), above, the District shall issue permits for construction, repair or modification of any well when:
(a) The well to be constructed, repaired, or modified is to be used for aquifer testing, hydrologic monitoring, water quality monitoring, or otherwise for the purpose of gathering hydrogeologic data; or (b) The applicant demonstrates that a compelling need exists to commence construction, repair or modification of the well while an application for a water use permit is pending; and
- 1. The Applicant has filed an application for Water Use Permit including all information required by Rule 40D-2.101, F.A.C.,
and the application has been deemed complete; and
- 2. It appears that the proposed use of water represented in the pending complete Water Use Permit application is a reasonable and beneficial use, will not interfere with any presently existing legal use of water, and is consistent with the public interest.
(c) The applicant agrees to all conditions attached to the well permit.
(3) The District is under no obligation to issue a water use permit merely because construction, repair or modification of a well has been authorized.
Rulemaking Authority 373.044, 373.113, 373.171, 373.309, 373.337 FS. Law Implemented 373.309 FS. History-New 7-1-90, Amended 9-30-91, 12-31-92, 3-30-93, 8-10-93, 7-12-15.
3F0625-01 / Attachment 8 / Page 8 of 23
40D-3.301 Conditions for Issuance of Permits.
(1) In order to obtain a water well construction, repair, modification or abandonment permit, an applicant must demonstrate compliance with the following conditions:
(a) The applicant shall have a current, valid water well contractor license from the State of Florida unless the permit is for a water well two (2) inches or less in diameter constructed by an individual for his own private use on his own or leased property as specified in Section 373.326(2), F.S.
(b) The applicant shall submit a permit application as specified by Rule 40D-3.101, F.A.C.
(c) The application must be complete and meet the requirements of Chapter 373, F.S., and this chapter.
(d) A Water Use Permit, if applicable under Chapter 40D-2, F.A.C., shall have been obtained.
(e) The applicant shall not have overdue well completion reports.
(f) The proposed water well shall not adversely impact the water resource.
(2) The District shall impose on any permit issued under this chapter such reasonable conditions as are necessary to protect the water resource and assure that the permitted activity will be consistent with the overall objectives of the District. The District shall attach such conditions to the permit, and well construction, repair, modification or abandonment shall be performed accordingly. An applicant who believes that a condition is unreasonable or is not necessary to protect the water resource or to assure that the permitted activity is consistent with the Districts overall objectives, has the right to petition and be heard in an administrative hearing pursuant to Chapter 120, F.S., regarding imposition of the condition.
Rulemaking Authority 373.044, 373.113, 373.171, 373.309, 373.337 FS. Law Implemented 373.109, 373.306, 373.308, 373.309, 373.313 FS.
History-New 10-5-74, Formerly 16J-3.11(1)-(3), Amended 1-8-87, 7-1-90, 12-31-92, 7-2-98, 8-19-08.
3F0625-01 / Attachment 8 / Page 9 of 23
40D-3.505 Location.
(1) Wells shall be located so as to not pose a threat of contamination to the water resource and to provide for the protection of the health, safety and welfare of the user.
(2) Minimum spacing between wells and sanitary hazards, including but not limited to, septic tanks, drain fields and ground water contamination areas, shall be as specified by Section 381.0065, F.S., and subsection 62-532.400(7), F.A.C. The District shall increase these distances if necessary to protect the health, safety and welfare of individuals who may be exposed to ground water contamination through ingestion, inhalation or dermal absorption.
(3) The District will deny a permit application to construct a water well if use of the well would increase the potential for harm to public health, safety and welfare, or if the proposed well would degrade the water quality of the aquifer by causing pollutants to spread.
(4) A variance from the above-specified restrictions may be obtained from the District as provided in Rule 40D-1.1001, F.A.C.
The review of a variance request shall include an evaluation of the following criteria, as applicable: surface and ground water gradients, well location, withdrawal amount, well depth (including depth of casing), natural barriers, impermeable geological strata, water quality sampling, compliance with the requirements of Chapter 62-524, F.A.C., other grouting or protective well construction measures, and the use of treatment systems acceptable to the Department or Department of Health.
(5) Nothing in this section relieves an applicant of the responsibility to comply with the requirements of any other regulatory agency with jurisdiction over the applicants activities.
Rulemaking Authority 373.044, 373.113, 373.171, 373.309, 373.337 FS. Law Implemented 373.306, 373.308, 373.309 FS. History-New 7-1-90, Amended 12-31-92, 7-2-98, 5-4-05.
3F0625-01 / Attachment 8 / Page 10 of 23
ATTACHMENT 2 Groundwater Model Summary 3F0625-01 / Attachment 8 / Page 11 of 23
Page 1 www.haleyaldrich.com ATTACHMENT 2 - Groundwater Model Summary 21 March 2024 File No. 134300-014 To:
NorthStar Group Services, Inc.
John Jernigan, D&D Licensing Manager From:
Haley & Aldrich, Inc.
Raghavendra Suribhatla Maruti, Ph.D., Technical Expert Nadia Glucksberg P.G., Principal Hydrogeologist
Subject:
Groundwater Model Summary Crystal River Unit 3, Crystal River, Florida INTRODUCTION On behalf of Accelerated Decommissioning Partners (ADP), Haley & Aldrich, Inc. (Haley & Aldrich) has prepared this memorandum to provide a summary of the saltwater intrusion model constructed to evaluate the impact of a groundwater production well at the Crystal River Nuclear Plant Unit 3 (ADP CR3). The groundwater modeling analyses were conducted to support the License Termination Plan (LTP) for two scenarios with respect to the Florida Department of Environmental Protection (FDEPs) water protection regulations. The two scenarios evaluated include: 1) Single-Family Household scenario; and 2) Resident Farmer scenario. The following text describes the model construction, assumptions, and results of the seawater intrusion analyses.
METHODS AND ASSUMPTIONS The numerical model SEAWAT (Langevin et al., 2008)1 was used for the saltwater intrusion modeling effort. SEAWAT is a coupled version of MODFLOW and MT3DMS designed to simulate variable density and saturated groundwater flow; it is routinely applied to saltwater intrusion studies. A two-dimensional (2D) cross-section was constructed to model a representative north-south cross-section at the ADP CR3 Site. 2D cross-section models are routinely used to simulate landward migration of saltwater from an ocean or sea boundary toward an inland boundary. In this study, the 2D model boundaries represent the intake canal and discharge canal.
The ADP CR3 saltwater intrusion flow model domain (Figure 1) covers a width of 500 feet (ft),
representing the average distance between the canals, and 90 ft in the vertical direction. The model consists of 50 columns uniformly spaced 10 ft apart, and 18 layers with a uniform thickness of 5 ft. Studies have shown that the shallow portion of the Floridan Aquifer beneath 1 Langevin, C.D., D.T. Thorne, Jr., A.M. Dausman, M.S. Sukop, and W. Guo, 2008. SEAWAT Version 4: A Computer Program for Simulation of Multi-Species Solute and Heat Transport. Accessed at:
https://pubs.usgs.gov/tm/tm6a22/pdf/tm6A22.pdf.
3F0625-01 / Attachment 8 / Page 12 of 23
Page 2 the Site consists of two primary zones in the Inglis Formation: 1) a zone from the surface to approximately 30 ft below land surface (BLS); and 2) a zone extending from between 40 to 60 ft BLS down to where the Inglis and Avon Park Formations interface. The upper zone contains many large, interconnected solution cavities and channels that are highly permeable, whereas the solid, unfractured limestone between the two zones has a much lower permeability.
The lower zone contains smaller voids and solution channels that are not as transmissive as those in the upper zone. Model layers 1 and 2 represent shallow soil, 3 through 7 represent the Inglis formation limestone, and 8 through 19 represent the transition to Avon Formation dolomite. Hydraulic conductivity values for the model layers were assigned based on available Site-specific data and the Central Springs Model (Southwest Florida Water Management District
[SWFWMD] and St. Johns River Water Management District [SJRWMD], 2023).2 Hydraulic conductivity of shallow soil was set to 10 feet per day (ft/day) based on the Central Springs model values for the area. Hydraulic conductivity of the limestone layers is set to 200 ft/day (layers 3 and 4) and 300 ft/day (layers 5, 6, and 7), respectively, based on historical pumping test data from the Site. Model layers 8 through 18 are assigned a hydraulic conductivity of 10 ft/day, which is representative of the lower permeability zone.
The following discussions presents these boundary conditions in the context of the conceptual site model for groundwater at ADP CR3:
The intake and discharge canals are represented as specified head and concentration boundaries. A head value of 90 feet (Site datum) and a concentration of 5.3 parts per thousand (ppt) was assigned to the boundaries. For reference, seawater salinity is generally recognized as 35 ppt. Based on the National Secondary Drinking Water Regulations of 250 milligrams/liter for chloride, the corresponding salinity threshold is approximately 0.45 ppt.
Figure 2 shows the plan view of the measurement locations. Figure 3 shows a simplified north-south cross-section of the measured salinity data. Note that all measured data are projected on to this simplified cross-section, including wells located the farthest distance from the canals. The assigned concentration value is the average of recently measured salinity data from the Site.
Measured salinity values ranged from 24.5 ppt in the deepest screened well (CR3-6D) to 0.1 ppt in a shallow well (CR3-3S) located farther inland. The data show increasing salinity with depth and decreasing salinity at inland wells located farther away from the canals. The data support a conceptual model of freshwater discharging out toward the canals and increasing in salinity westward as it mixes with the denser seawater through the discharge zone. This conceptual model of freshwater-saltwater is typical of the groundwater systems in southwest Florida.
Under natural conditions, this seaward movement of freshwater prevents saltwater from intruding farther inland. The interface between freshwater and saltwater is maintained near the coast and gradually deepens as a seawater wedge forms beneath the land surface.
An average salinity of 5.3 ppt was used for boundary values for the scenario modeling. This average value was used because a continuous depth profile was not available. Nevertheless, using a vertical profile of increasing salinity (e.g., from 3.06 ppt at CR3-5 to 24.54 ppt at CR3-6D along the boundary) will lead to seawater intrusion due to pumping at a time similar to or slightly later than when an average value is used. This is because the average assigned value to deeper units represents significantly lower than measured salinity. For the Resident Farmer scenario, one irrigation well, pumping a total of 700 cubic feet per day (cfd), is placed in the 2 Accessed at: https://www.sjrwmd.com/water-supply/planning/csec-rwsp/#central-springs.
3F0625-01 / Attachment 8 / Page 13 of 23
Page 3 center of the model domain, and is screened in the model layers representing the highly permeable limestone aquifer. This volume represents annual usage under the Resident Farmer scenario to fill water demand for households, livestock, and crop irrigation. The applied volume of 700 cfd was published as a default value in the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM).
For the single-family household use scenario, one domestic well, pumping a total of 70 cfd, is placed in the center of the model domain, and is screened in the model layers representing the highly permeable limestone aquifer. This volume represents annual usage for a four-person family, based on data from the Southwest Florida Water Management District 2021 Estimated Water Use Report.
Recharge was assigned to the model domain based on the data from the Central Springs Model.
The assigned recharge value is equal to 5 x 10-3 ft/day or 27 inches per year.
SEAWATER INTRUSION ANALYSIS SEAWAT model simulations were conducted to evaluate the salinity at the extraction well and the potential for intrusion of saltwater from the intake and discharge canal boundaries. Model simulation time was set to a sufficiently long period for the evaluation. For the Resident Farmer scenario, the simulation time was set to 10,000 days. For the Single-Family Household scenario, the simulation time was set to 100,000 days. It is noted here that the simulation times are less than the Nuclear Regulatory Commissions requirement to evaluate conditions for 1,000 years; however, with the estimated breakthrough, the simulation time periods are appropriate for this modeling effort.
Figure 4a shows the saltwater profile for the Resident Farmer scenario at the end of simulation and the impact of irrigation well. Figure 4b shows the saltwater profile for the Single-Family Household scenario at the end of simulation and the impact of domestic well. Figures 5a and 5b show the plots of concentration observed at the wells in the two scenarios respectively. Based on the model results for the Resident Farmer scenario, salinity at the irrigation well increases to a value exceeding the threshold of 0.45 ppt after approximately 1,900 days in layer 3, while the average salinity exceeds the threshold at approximately 2,700 days. For the Single-Family Household scenario, salinity at the domestic well increases to a value exceeding the threshold after approximately 6,030 days in layer 7, while the average salinity exceeds the threshold after approximately 10,450 days.
The above results indicate that the irrigation well pumping will lead to saltwater intrusion and an exceedance of salinity in the pumped water over time.
LIMITATIONS SEAWAT model was built using available information to support saltwater intrusion evaluations and conclusions. The models level of accuracy is directly dependent on the data available to construct the model and should not be construed by the user as a definitive predictor of the future. Instead, the model simulation results and the threshold exceedance time should be primarily considered as screening-level information for seawater intrusion due to pumping near the intake and discharge canals.
3F0625-01 / Attachment 8 / Page 14 of 23
Page 4 CONCLUSIONS Based on this 2D groundwater model, groundwater quality is impacted by the extraction or withdrawal of groundwater needed to support the Resident Farmer and Single-Family scenario. Saltwater intrusion due to pumping would impact the aquifer at ADP CR3.
Although the FDEP does not restrict the drilling and installation of groundwater wells in Citrus County, it does require a water use permit (WUP). Based on the modeling results, we cannot provide reasonable assurance that the pumping would not cause up-coning or degradation of the aquifer water quality. In compliance with the regulations, FDEP cannot issue this permit for water withdrawal, especially at the volumes needed to support the Resident Farmer or the Single-Family scenarios to maintain their sustenance for 1,000 years.
Enclosures:
Figure 1 - Model Boundary Conditions Figure 2 - Plan View of Well Locations with Salinity Measurements Figure 3 - Simplified Cross-Section View of Measured Salinities at Monitoring Wells Figure 4a - Resident Farmer Scenario Simulated Salinity at 10,000 Days Figure 4b - Single-Family Scenario Simulated Salinity at 100,000 Days Figure 5a - Resident-Farmer Scenario Simulated Salinity at Irrigation Well Figure 5b - Single-Family Scenario Simulated Salinity at Domestic Well
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Modeling\\2024_0321_Modeling_Attachment 2_D2.docx 3F0625-01 / Attachment 8 / Page 15 of 23
FIGURES 3F0625-01 / Attachment 8 / Page 16 of 23
Figure 1-Model Boundary Conditions Irrigation Well I '
I
/
Intake Canal Boundary Discharge Canal Boundary 3F0625-01 / Attachment 8 / Page 17 of 23
Figure 2. Plan View of Well Locations with Salinity Measurements 3F0625-01 / Attachment 8 / Page 18 of 23
CR3 Salinity Cross-Section (ppt)
- I
'lai c 20 J.. I 0.10 j.30 I 2.33 CR3-3S Cf\\3-6 I
2.26 CR3-1S I
0.63
°'3-10 l
1.51 i -<<>
~ *SO 8.83 24.54 4.43
.(j()
.70 80
.90 0
100 2
300 400 S00 600 1
Dist nee North from Intake Channel fft, Figure 3. Simplified Cross-Section View of Measured Salinities at Monitoring Wells 3F0625-01 / Attachment 8 / Page 19 of 23
Figure 4a: Resident-Farmer Scenario Simulated Salinity at 10,000 days Salinity 5.3 ppt 0.0 ppt 3F0625-01 / Attachment 8 / Page 20 of 23
Figure 4b: Single-Family Scenario Simulated Salinity at 100,000 days Salinity 5.3 ppt 0.0 ppt 3F0625-01 / Attachment 8 / Page 21 of 23
Figure Sa: Resident-Farmer Scenario Simulated Salinity at Irrigation Well Simulated Salinity (parts per thousand) 3.00 Layer3 2.50 Layer4 Layers
~2.00
- a.
Layer6
- a.
Layer7
-~1.50 C
* Average Salinity (ppt) ro V'l 1.00 0.50 0.00 0
2000 4000 6000 Simulation Time (days) 8000 10000 3F0625-01 / Attachment 8 / Page 22 of 23
Figure Sb: Single-Family Scenario Simulated Salinity at Domestic Well 2.00 1.80 1.60
'R 1.40
~ l.20 z;-1.00
.c 0.80
~ 0.60 0.40 0.20 0.00 0
10000 20000 Simulated Salinity (parts per thousand) 30000 40000 50000 60000 Simulation Time (days)
Layer3 Layer4 Layers Layer6 Layer7
Average Salinity 70000 80000 90000 100000 3F0625-01 / Attachment 8 / Page 23 of 23