Section R18-9-C301. 2.01 General Permit: Drywells That Drain Areas Where Hazardous Substances Are Used, Stored, Loaded, or Treated

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 sub- mitted to the Department;

2.        For a drywell constructed more than 90 days before sub- mitting the Notice of Intent to Discharge to the Depart- ment,  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 resi- dential 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 groundwa- ter 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 sur- face grate or manhole cover;

3.        Locate the bottom of the drywell hole at least 10 feet above groundwater. If during drilling and well installa- tion the drywell borehole encounters saturated condi- tions, the applicant shall backfill the borehole with cement grout to at least 10 feet above the elevation of sat- urated 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 pollut- ants that may be present at the operation with the poten- tial to reach the drywell. The applicant may include a flow control or pretreatment device, such as an intercep- tor, 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 require- ments 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 coordi- nates of the drywell, surface drainage patterns, the loca- tion 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 dis- posal of stormwater. The permittee shall not release industrial process waters or wastes in the drywell or dry- well retention basin drainage area.

2.        The permittee shall implement a Best Management Prac- tices Plan for operation of the drywell and control of pol- lutants 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 Con- tainment and Control Plan, facility response plan, or an AZPDES Stormwater Pollution Prevention Plan that meets the requirements of this subsection for a Best Man- agement Practices Plan. If the permittee submits a substi- tute for the Best Management Practices Plan, the permittee shall identify the conditions within the substi- tute 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 enter- ing the drywell;

b.        A design plan showing details of drywell design and drainage design, including flow control or pretreat- ment 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 mini- mize discharges to the drywell;

d.        Operational practices that include routine inspection and maintenance of the drywell and associated pre- treatment and flow-control devices, periodic inspec- tion 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 skim- mers, 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 prac- tices required by the Best Management Practices Plan specific to the drywell and prevention of unau- thorized discharges.

6.        The permittee shall implement waste management prac- tices 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 drain-

age area. If the permittee collects and stores the waste within the drywell drainage area, the permit- tee 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, which- ever comes first, to restore capacity and ensure that the drywell functions properly. The permittee shall character- ize 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 lati- tude 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 pretreat- ment technologies;

4.        An operations and maintenance manual that includes:

a.         Procedures to prevent and contain spills and mini- mize any discharge to the drywell and a list of actions and methods proposed to prevent and con- tain 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 man- ifest 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 sam- pling 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 dry- well 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 treat- ment 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 deter- mine whether a soil remediation level or groundwa- ter 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 pro- hibited from use in backfilling the drywell; and

e.         Mechanically compact the backfill.

2.        Within 30 days of closure and decommissioning, the per- mittee shall submit a written verification to the Depart- ment 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 compli- ance 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 dry- well;

e.         The name of the contractor who performed the clo- sure;

f.         The completion date;

g.        Any sampling data;

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

i.         Any other information necessary to verify that clo- sure has been achieved.

Historical Note

New Section adopted by final rulemaking at 7 A.A.R. 235, effective January 1, 2001 (Supp. 00-4). Amended by final rulemaking at 11 A.A.R. 4544, effective November 12, 2005 (05-3).