DWQ-2024-006918

STATEMENT OF BASIS 

Ground Water Discharge Permit Renewal No. UGW210002 

American Pacific Corporation (AMPAC) 
10622 West 6400 North 
Cedar City, Utah 84721 

October 2024 

Introduction 

The Division of Water Quality (DWQ) under the authority of the Utah Ground Water Quality Protection Rules (Ground Water Rules) issues ground water discharge permits to facilities which
have a potential to discharge contaminants to ground water.  As defined by the Ground Water Rules, such facilities include ponds and lagoons. The Ground Water Rules are based on an antidegradation
strategy for ground water protection as opposed to non-degradation; therefore, discharge of contaminants to ground water may be allowed provided that current and future beneficial uses
of the ground water are not impaired and the other requirements of Rule 317-66.4.A are met.  Following this strategy, ground water is divided into classes based on its quality5; and
higher-quality ground water is given greater protection due to the greater potential for beneficial uses. DWQ has developed permit conditions consistent with R317-6 and appropriate to
the nature of the mined materials, facility operations, maintenance, best available technology (BAT) and the hydrogeologic and climatic conditions of the site, to ensure that the operation
would not contaminate ground water.   

Basis for Permit Issuance 

Under Rule 317-6-6.4A, DWQ may issue a ground water discharge permit if: 

The applicant demonstrates that the applicable class TDS limits, ground water quality standards protection levels and permit limits established under R317-6-6.4E will be met;
The monitoring plan, sampling and reporting requirements are adequate to determine compliance with applicable requirements;
The applicant is using best available technology to minimize the discharge of any pollutant; and
There is no impairment of present and future beneficial uses of ground water. 

Overview 

AMPAC’s groundwater discharge permit, No. UGW210002 is being amended and renewed. UGW21002 was originally issued on July 20, 1992.  The original permit contained language describing
the process used to destroy the azide ion in wastewater before it is discharged to the lined evaporation pond.  Since then, azide destruction has evolved through actual operation of
the process.  The permit was modified in 2010 to reflect the azide destruction process as currently practiced, and to account for discharge of wastewater from deionization resin regeneration
at both the WECCO plant and the azide plant. 
Description of Facility 

Azide Lagoon - Permit No. UGW210002 originally covered the operation of a wastewater lagoon at AMPAC’s sodium azide manufacturing plant 12 miles northwest of Cedar City, Utah. The Azide
Lagoon contains contact process wastewater from the sodium azide manufacturing process. This wastewater contains sodium ions, nitrate and nitrite ions, impurities from the commercial
grade sodium supply, and iron hydroxides from the corrosion of piping. At present, much less wastewater is being discharged to the lagoon than its design capacity, due to decreased demand
for sodium azide for automobile air bags.  Wastewater from deionization resin regeneration from the nearby WECCO oxidizer plant and also from the azide plant will be discharged into
the azide plant’s lagoon.  These waste streams contain the natural dissolved solids from the plant’s water supply. Deionization wastewater from the azide plant will be tested for the
presence of azide ions, and treated if necessary.  Other unanticipated constituents may also be present in the wastewater at de minimis concentrations. 
WECCO Evaporation Pond #1 - There is a current evaporation pond for the WECCO facility. This pond was constructed with a single 60-mil HDPE liner. On January 29, 2013 a Construction
Permit was issued by DWQ for the repair of that pond. For many years AMPAC has been submitting annual Surface Impoundment Updates to the Division of Waste Management and Radiation Control.
These updates included Toxic Characteristic Leaching Procedure (TCLP) analytical results for the wastewater discharged to the current evaporation pond. This current pond and a new
proposed evaporation pond will now be regulated under this Ground Water Discharge Permit. All future submittals shall come to DWQ.
WECCO Evaporation Pond #2 As part of this ground water permit, a construction permit will be issued to AMPAC to construct a second WECCO evaporation pond. The construction permit will
be issued concurrently with this permit. Under authority of the Utah Water Quality Act, Section 19-5-108(1) Utah Code Ann. 1953, as amended and Utah Administrative Code R317-1, the
authorized facilities will be constructed in accordance with the engineering design plans and specifications attached as Appendix A. Part II.D of this permit describes the Best Available
Technology (BAT) standards for these permitted facilities
The authorized evaporation pond will be constructed in accordance with the engineering design plans and specifications approved by the Construction Permit. The pond footprint is approximately
3.7 acres with the maximum storage capacity of 14.5 acre-feet of volume with 3-feet of freeboard. The pond will be lined with two 60-mil high density polyethylene (HDPE) liners and
will have a leak detection system.
The Azide Lagoon and the WECCO Pond #1 and #2 will now all be covered underAMPAC’s groundwater discharge permit, No. UGW210002.

Operation of Facility 

The Azide Lagoon is operated as a no discharge impoundment for process wastewater. After the manufacturing process, the wastewater will contain sodium azide. Sodium azide, when disposed
of in its commercially pure form, is a listed hazardous waste. Although the sodium azide in the wastewater stream will not be commercially pure, American Azide prevents discharge of
sodium azide to the lagoon by treating the wastewater from the azide plant in batches until no sodium azide is detected. Records are kept of the test results for each batch of wastewater
treated.  If any untreated wastewater containing azide is discharged to the lagoon, AMPAC will report the incident to DWQ and to DSHW. Salts and sediments, which accumulate in the lagoon,
will be removed upon closure. 
The WECCO Ponds #1 and #2 will be used for the washdown of the WECCO facilities and may have trace amounts of ammonium perchlorate. The facilities are initially swept and cleaned prior
to the washdown.
WECCO Pond #2 will be a double lined pond with a leak detection system. The point of compliance will be the leak detection system. A monitoring plan of the leak detection system is
required for review and approval before Pond #2 can be put into use. This may be part of the operations and maintenance manual required in the Construction Permit. Upon completion
of Pond #2, Pond #1 will be taken out of service and allowed to dry. Pond #1 will then be carefully inspected and repaired as necessary. At that time, Pond #1 may also be reconstructed
and converted to a double lined pond with a leak detection system. A Construction Permit shall be required for that work.

Site Hydrogeology 

The site is located in an alluvial fan area draining toward the Escalante Desert. As such, it is probably a potential recharge zone for alluvial aquifers to the north and west. Ground
water also flows into the Escalante Desert from Cedar City Valley through Iron Springs Gap, about three miles southwest of the site. Regional water level data suggests that the hydraulic
gradient slopes to the west-northwest at the plant site. AMPAC has constructed an upgradient monitor well, MW1, approximately 600 feet east of the east boundary of the sodium azide plant
site. Materials encountered during drilling of this well were predominantly clays and silts with minor sand and gravel lenses. Moist soil was first encountered at 170-190 feet during
drilling, and the static water level measured after well completion was about 140 feet below land surface. This indicates that the uppermost ground water under the site is underneath
confining layers and under artesian pressure. Under these conditions, ground water monitoring would probably be an ineffective means to demonstrate compliance with the BAT containment
technology standard of this permit. 

Background Ground Water Quality 

Water quality data from the upgradient monitor well indicates that groundwater at the site has an average dissolved solids content of 543 mg/l. Mean concentrations of other constituents
derived from monitoring this well over one year are contained in Table 1 of the permit. Because AMPAC has chosen source monitoring rather than ground water monitoring as a mechanism
to insure compliance with the terms of the permit, downgradient monitoring to demonstrate that protection levels are being met will not be required for this permit. Permit compliance
is demonstrated by compliance with Best Available Treatment Technology. 

Ground Water Classification 

Based on monitoring results from well MW-1, ground water at the site is classified as Class II. 

Best Available Technology 

AMPAC is using best available technology to achieve a no discharge situation. The liner technology used in the Azide Lagoon is described below (top to bottom): 

80-mil HDPE liner 
Drainage net 
40-mil HDPE liner 
Drainage net 
40-mil VLDPE liner 
12 inches of clay with hydraulic conductivity 1 x 10-7 or less 

Drainage nets between the flexible membrane liners shall slope to sumps, which can be monitored for leaks. 
The WECCO Pond #1is lined with a single 60-mil HDPE liner. WECCO Pond #2 will be a double lined pond with a leak detection system.

Monitoring Procedures for Leak Detection 

Azide Lagoon - AMPAC is to monitor any flows entering the sumps on a daily basis for the upper leak collection and removal layer (head break system) and the lower leak detection layer.
Flow information for the head break layer is informational only. The lower leak detection system will be the compliance monitoring mechanism for the permit. The presence of wastewater
in the leak detection sump will constitute failure of BAT and the permittee will be considered out-ofcompliance with the permit unless affirmative defense is established in accordance
with Part I E 1 (b). AMPAC will be required to take the steps outlined in I E 1 (b) of the permit if wastewater is detected in the leak detection sump. 

WECCO Pond #1 shall be sampled quarterly and the sample shall be taken at the outfall of the pipe flowing into the pond. A grab sample from the pond shall also be taken.
WECCO Pond #2 will be a double lined pond with a leak detection system. The point of compliance will be the leak detection system.
All sampling results will be sent to DWQ.
Corrective Action Plan 

Azide Lagoon - If seepage of wastewater is confirmed in the lower leak detection sumps pursuant to the procedure outlined in Part I E 1 (b) of this permit, AMPAC is required to evaluate
whether contaminants have been released to the environment. If releases from the pond or any other source on the site are confirmed, the company shall develop a plan to fully evaluate
the extent of the contamination and identify the measures that will be taken to protect existing ground water quality. The plan will be submitted within 30 days of the date that release
of contaminants is confirmed and implemented upon approval by the Executive Secretary. 
WECCO Pond #2 – Upon completion and approval to use, Pond #2 will be put into use. The point of compliance will be the leak detection system.If seepage of wastewater is confirmed in
the leak detection system, AMPAC is required to evaluate whether contaminants have been released to the environment. If releases from the pond or any other source on the site are confirmed,
the company shall develop a plan to fully evaluate the extent of the contamination and identify the measures that will be taken to protect existing ground water quality. The plan will
be submitted within 30 days of the date that release of contaminants is confirmed and implemented upon approval by the Executive Secretary. 
WECCO Pond #1 - Upon completion of Pond #2, Pond #1 will be taken out of service and allowed to dry. Pond #1 will then be carefully inspected and repaired as necessary. At that time,
Pond #1 may also be reconstructed and converted to a double lined pond with a leak detection system. A Construction Permit shall be required for that work.
DWQ-2024-