Arizona Administrative Code
Title 18 - ENVIRONMENTAL QUALITY
Chapter 9 - DEPARTMENT OF ENVIRONMENTAL QUALITY - WATER POLLUTION CONTROL
Article 3 - AQUIFER PROTECTION PERMITS - GENERAL PERMITS
Part C - TYPE 2 GENERAL PERMITS
Section R18-9-C301 - 2.01 General Permit: Drywells That Drain Areas Where Hazardous Substances Are Used, Stored, Loaded, or Treated

Universal Citation: AZ Admin Code R 18-9-C301

Current through Register Vol. 30, No. 38, September 20, 2024

A. A 2.01 General Permit allows for a drywell that drains an area where hazardous substances are used, stored, loaded, or treated.

B. Notice of Intent to Discharge. In addition to the requirements in R18-9-A301(B), an applicant shall submit:

1. The Department registration number for the drywell or documentation that a drywell registration form was submitted to the Department;

2. For a drywell constructed more than 90 days before submitting the Notice of Intent to Discharge to the Department, a certification signed, dated, and sealed by an Arizona-registered professional engineer or geologist that a site investigation has concluded that:
a. Analytical results from sampling the drywell settling chamber sediment for pollutants reasonably expected to be present do not exceed either the residential soil remediation levels or the groundwater protection levels;

b. The settling chamber does not contain sediments that could be used to characterize and compare results to soil remediation levels and the chamber has not been cleaned out within the last six months;

c. Neither a soil remediation level nor groundwater protection level is exceeded in soil samples collected from a boring drilled within 5 feet of the drywell and sampled in 5-foot increments starting from 5 feet below ground surface and extending to 10 feet below the base of the drywell injection pipe; or

d. If coarse grained lithology prevents the collection of representative soil samples in a soil boring, a groundwater investigation demonstrates compliance with Aquifer Water Quality Standards in groundwater at the applicable point of compliance;

3. Design information to demonstrate that the requirements in subsection (C) are satisfied; and

4. A copy of the Best Management Practices Plan described in subsection (D)(5).

C. Design requirements. An applicant shall:

1. Locate the drywell no closer than 100 feet from a water supply well and 20 feet from an underground storage tank;

2. Clearly mark the drywell "Stormwater Only" on the surface grate or manhole cover;

3. Locate the bottom of the drywell hole at least 10 feet above groundwater. If during drilling and well installation the drywell borehole encounters saturated conditions, the applicant shall backfill the borehole with cement grout to at least 10 feet above the elevation of saturated conditions before constructing the drywell in the borehole;

4. Ensure that the drywell design or drainage area design includes a method to remove, intercept, or collect pollutants that may be present at the operation with the potential to reach the drywell. The applicant may include a flow control or pretreatment device, such as an interceptor, sump, or another device or structure designed to remove, intercept, or collect pollutants. The applicant may use flow control or pretreatment devices listed under R18-9-C304(D)(1) or (2) to satisfy the design requirements of this subsection;

5. Record the accurate latitude and longitude of the drywell using a Global Positioning System device or site survey; and

6. Develop and maintain a current site plan showing the location of the drywell, the latitude and longitude coordinates of the drywell, surface drainage patterns, the location of floor drains and French drains plumbed to the drywell, water supply wells, monitor wells, underground storage tanks, and chemical and waste usage, storage, loading, and treatment areas.

D. Operational and maintenance requirements.

1. A permittee shall operate the drywell only for the disposal of stormwater. The permittee shall not release industrial process waters or wastes in the drywell or drywell retention basin drainage area.

2. The permittee shall implement a Best Management Practices Plan for operation of the drywell and control of pollutants in the drywell drainage area.

3. The permittee shall keep the Best Management Practices Plan on-site or at the closest practical place of work and provide the plan to the Department upon request.

4. The permittee may substitute any Spill Prevention Containment and Control Plan, facility response plan, or an AZPDES Stormwater Pollution Prevention Plan that meets the requirements of this subsection for a Best Management Practices Plan. If the permittee submits a substitute for the Best Management Practices Plan, the permittee shall identify the conditions within the substitute plan that satisfy the requirements of subsection (D).

5. The Best Management Practices Plan shall include:
a. A site plan showing surface drainage patterns and the location of floor drains, water supply, monitor wells, underground storage tanks, and chemical and waste usage, storage, loading, and treatment areas. The site plan shall show surface grading details designed to prevent drainage and spills of hazardous substances from leaving the drainage area and entering the drywell;

b. A design plan showing details of drywell design and drainage design, including flow control or pretreatment devices, such as interceptors, sumps, and other devices and structures designed to remove, intercept, and collect any pollutant that may be present at the operation with the potential to reach the drywell;

c. Procedures to prevent and contain spills and minimize discharges to the drywell;

d. Operational practices that include routine inspection and maintenance of the drywell and associated pretreatment and flow-control devices, periodic inspection of waste storage facilities, and proper handling of hazardous substances to prevent discharges to the drywell. Routine inspection and maintenance shall include:
i. Replacing the adsorbent material in the skimmers, if installed, when the adsorbent capacity is reached;

ii. Maintaining valves and associated piping for a drywell injection and treatment system;

iii. Maintaining magnetic caps and mats, if installed;

iv. Removing sludge from the oil/water separator, if installed, and replacing the filtration or adsorption material to maintain treatment capacity;

v. Removing sediment from the catch basin inlet filters and retention basin to maintain required storage capacity; and

e. Procedures for periodic employee training on practices required by the Best Management Practices Plan specific to the drywell and prevention of unauthorized discharges.

6. The permittee shall implement waste management practices to prohibit and prevent discharges, other than those exempted in A.R.S. § 49-250(B)(23), in the drywell drainage area, including:
a. Maintaining an up-to-date inventory of generated wastes and waste products;

b. Disposing or recycling all wastes or solvents through a company licensed to handle the material;

c. Where possible, collecting and storing waste in waste receptacles located outside the drywell drainage area. If the permittee collects and stores the waste within the drywell drainage area, the permittee shall collect and store the waste in properly designed receptacles; and

d. Using a licensed waste hauler to transport waste off-site to a permitted waste disposal facility.

E. Inspection. A permittee shall:

1. Conduct an annual inspection of the drywell for sediment accumulation in the chambers and the flow-control and treatment systems, and remove sediment annually or when 25 percent of the effective capacity is filled, whichever comes first, to restore capacity and ensure that the drywell functions properly. The permittee shall characterize the sediments that are removed from the drywell after inspection and dispose of the sediments according to local, state, and federal requirements; and

2. If the stormwater fails to drain through the drywell within 36 hours, inspect the treatment system and piping to ensure that the treatment system is functioning properly, make repairs, and perform maintenance as needed to restore proper function.

F. Recordkeeping. A permittee shall maintain for at least 10 years, the following documents on-site or at the closest place of work and make the documents available to the Department upon request:

1. Documentation of drywell maintenance, inspections, employee training, and sampling activities;

2. A site plan showing the location of the drywell, the latitude and longitude coordinates of the drywell, surface drainage patterns and the location of floor drains or French drains that are plumbed to the drywell or are used to alter drainage patterns, the location of water supply wells, monitor wells, underground storage tanks, and places where hazardous substances are used, stored, or loaded;

3. A design plan showing details of drywell design and drainage design, including any flow control and pretreatment technologies;

4. An operations and maintenance manual that includes:
a. Procedures to prevent and contain spills and minimize any discharge to the drywell and a list of actions and methods proposed to prevent and contain hazardous substance spills or leaks;

b. Methods and procedures for inspection, operation, and maintenance activities;

c. Procedures for spill response; and

d. A description of the employee training program for drywell inspections, operations, maintenance, and waste management practices;

5. Drywell sediment waste characteristics and disposal manifest records for sediments removed during routine inspections and maintenance activities; and

6. Sampling plans, certified laboratory reports, and chain of custody forms for soil, sediment, and groundwater sampling associated with drywell site investigations.

G. Spills.

1. In the event of a spill, the permittee shall:
a. Notify the Department within 24 hours of any spill of hazardous or toxic substance that enters the drywell inlet;

b. Contain, clean up, and dispose of, according to local, state, and federal requirements, any spill or leak of a hazardous substance in the drywell drainage area and basin drainage area;

c. If a pretreatment system is present, verify that treatment capacity has not been exceeded; and

d. If the spill reaches the drywell injection pipe, drill a soil boring within 5 feet of the drywell inlet chamber and sample the soil in 5-foot increments from 5 feet below ground surface to a depth extending at least 10 feet below the base of the injection pipe to determine whether a soil remediation level or groundwater protection level has been exceeded in the subsurface. The permittee shall:
i. Submit the results to the Department within 60 days of the date of the spill; and

ii. Notify the Department if soil contamination at the facility, not related to the spill, is being addressed by an existing approved remedial action plan.

2. Based on the results of subsection (G)(1)(d), the Director may require the permittee to submit an application for clean closure or an individual Aquifer Protection Permit.

H. Closure and decommissioning requirements.

1. A permittee shall:
a. Retain a drywell drilling contractor, licensed under 4 A.A.C. 9, to close the drywell;

b. Remove sediments and any drainage component, such as standpipes and screens from the drywell's settling chamber and backfill the injection pipe with cement grout;

c. Remove the settling chamber;

d. Backfill the settling chamber excavation to the land surface with clean silt, clay, or engineered material. Materials containing hazardous substances are prohibited from use in backfilling the drywell; and

e. Mechanically compact the backfill.

2. Within 30 days of closure and decommissioning, the permittee shall submit a written verification to the Department that all material that contributed to a discharge has been removed and any reasonable probability of further discharge from the facility and of exceeding any Aquifer Water Quality Standard at the applicable point of compliance has been eliminated to the greatest degree practical. The written verification shall specify:
a. The reason for the closure;

b. The drywell registration number;

c. The general permit reference number;

d. The materials and methods used to close the drywell;

e. The name of the contractor who performed the closure;

f. The completion date;

g. Any sampling data;

h. Sump construction details, if a sump was constructed to replace the abandoned drywell; and

i. Any other information necessary to verify that closure has been achieved.

Disclaimer: These regulations may not be the most recent version. Arizona may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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