WAC 173-350-330   Surface impoundments and tanks.  (1) Surface impoundments and tanks - Applicability.

     (a) These standards are applicable to:

     (i) Surface impoundments holding solid waste associated with solid waste facilities including, but not limited to, leachate lagoons associated with landfills permitted under this chapter and chapter 173-351 WAC, Criteria for municipal solid waste landfills, and surface impoundments associated with recycling, and piles used for storage or treatment;

     (ii) Above or below ground tanks with a capacity greater than one thousand gallons holding solid waste associated with solid waste handling facilities used to store or treat liquid or semisolid wastes or leachate associated with solid waste handling facilities.

     (b) These standards are not applicable to:

     (i) Surface impoundments or tanks whose facilities are regulated under local, state or federal water pollution control permits;

     (ii) Leachate holding ponds at compost facilities regulated under WAC 173-350-220;

     (iii) Septic tanks receiving only domestic sewage from facilities at the site;

     (iv) Agricultural waste managed according to a farm management plan written in conjunction with the local conservation district;

     (v) Underground storage tanks subject to chapter 173-360 WAC, Underground storage tanks; and

     (vi) Tanks used to store moderate risk waste subject to WAC 173-350-360.

     (2) Surface impoundments and tanks - Location standards.

     Surface impoundments and tanks shall not be located in unstable areas unless the owner or operator demonstrates that engineering measures have been incorporated in the facility's design to ensure that the integrity of the liners, monitoring system and structural components will not be disrupted. The owner or operator shall place the demonstration in the application for a permit.

     (3) Surface impoundments and tanks - Design standards.

     (a) The owner or operator of a surface impoundment shall prepare engineering reports/plans and specifications, including a construction quality assurance plan, to address the design standards of this subsection. In determining pond capacity, volume calculations shall be based on the facility design, monthly water balance, and precipitation data. All surface impoundments shall be designed and constructed to meet the following requirements:

     (i) Have a liner consisting of a minimum 30-mil thickness geomembrane overlying a structurally stable foundation to support the liners and the contents of the impoundment. (HDPE geomembranes used as primary liners or leak detection liners shall be at least 60-mil thick to allow for proper welding.) The jurisdictional health department may approve the use of alternative designs if the owner or operator can demonstrate during the permitting process that the proposed design will prevent migration of solid waste constituents or leachate into the ground or surface waters at least as effectively as the liners described in this subsection.

     (ii) Have a groundwater monitoring system which complies with the requirements of WAC 173-350-500 or a leak detection layer. If a leak detection layer is used, it shall consist of an appropriate drainage layer underlain by a geomembrane of at least 30-mil thickness.

     (iii) Have embankments and slopes designed to maintain structural integrity under conditions of a leaking liner and capable of withstanding erosion from wave action, overfilling, or precipitation.

     (iv) Have freeboard equal to or greater than eighteen inches to provide protection against wave action, overfilling, or precipitation. During the permitting process the jurisdictional health department may reduce the freeboard requirement provided that other specified engineering controls are in place which prevent overtopping.

     (v) When constructed with a single geomembrane liner, the liner shall be tested using an electrical leak location evaluation capable of detecting a hole 3 millimeters in its longest dimension or other equivalent postconstruction test method prior to being placed in service. Results of the test shall be submitted with the construction record drawings.

     (vi) Surface impoundments that have the potential to impound more than ten-acre feet (three million two hundred fifty-nine thousand gallons) of liquid measured from the top of the embankment and which would be released by a failure of the containment embankment shall be reviewed and approved by the dam safety section of the department.

     (vii) No surface impoundment liner shall be constructed such that the bottom of the lowest component is less than five feet (one and one-half meters) above the seasonal high level of groundwater unless the owner or operator can demonstrate during the permitting procedure that the proposed design will not be affected by contact with groundwater. All surface impoundment liners shall be constructed such that the bottom of the lowest component is above the seasonal high level of groundwater. For the purpose of this section, groundwater includes any water-bearing unit which is horizontally and vertically extensive, hydraulically recharged, and volumetrically significant.

     (b) The owner or operator of a tank used to store or treat liquid or semisolid wastes meeting the definition of solid waste or leachate, shall prepare engineering reports/plans and specifications, including a construction quality assurance plan, to address the following design standards:

     (i) Tanks and ancillary equipment shall be tested for tightness using a method acceptable to the jurisdictional health department prior to being covered, enclosed or placed in use. If a tank is found not to be tight, all repairs necessary to remedy the leak(s) in the system shall be performed and verified to the satisfaction of the jurisdictional health department prior to the tank being covered or placed in use.

     (ii) Below ground tanks and other tanks where all or portions of the tank are not readily visible shall be designed to resist buoyant forces in areas of high groundwater and shall either be:

     (A) Retested for tightness at a minimum of once every two years; or

     (B) Equipped with a leak detection system capable of detecting a release from the tank;

     (iii) For tanks or components in which the external shell of a metal tank or any metal component will be in contact with the soil or water, a determination shall be made by a corrosion expert of the type and degree of external corrosion protection that is needed to ensure the integrity of the tank during its operating life. This determination shall be included with design information submitted with the permit application;

     (iv) Above ground tanks shall be equipped with secondary containment constructed of, or lined with, materials compatible with the waste being stored and capable of containing the volume of the largest tank within its boundary plus the precipitation from the twenty-five-year storm event as defined in WAC 173-350-100;

     (v) Areas used to load or unload tanks shall be designed to contain spills, drippage and accidental releases during loading and unloading of vessels;

     (vi) Tanks and piping shall be protected from impact by vehicles or equipment through use of curbing, grade separation, bollards or other appropriate means;

     (vii) Tanks shall be structurally suited for the proposed use; and

     (viii) Tanks, valves, fittings and ancillary piping shall be protected from failure caused by freezing.

     (4) Surface impoundments and tanks - Operating standards. The owner or operator of a surface impoundment or tank shall:

     (a) Operate the facility to:

     (i) Prevent overfilling of surface impoundments or tanks and maintain required freeboard;

     (ii) Control access to the site;

     (iii) Control nuisance odors for wastes or liquids with the potential to create nuisance odors; and

     (iv) Control birds at impoundments storing wastes capable of attracting birds.

     (b) Inspect surface impoundments, tanks and associated piping, pumps and hoses as needed, but at least weekly, to ensure they are meeting the operational standards, unless an alternate schedule is approved by the jurisdictional health department as part of the permitting process. In addition, surface impoundments shall have regular liner inspections. Their frequency and methods of inspection shall be specified in the plan of operation and shall be based on the type of liner, expected service life of the material, and the site-specific service conditions. The inspections shall be conducted at least once every five years, unless an alternate schedule is approved by the jurisdictional health department as part of the permitting process. The jurisdictional health department shall be given sufficient notice and have the opportunity to be present during liner inspections.

     (c) Maintain daily operating records on the quantity and the types of waste removed from the surface impoundment or tank. Facility inspection reports shall be maintained in the operating record. Significant deviations from the plan of operation shall be noted in the operating record. Records shall be kept for a minimum of five years and shall be available for inspection upon request by the jurisdictional health department.

     (d) Shall prepare and submit a copy of an annual report to the jurisdictional health department and the department by April 1st. The annual report shall detail the facility's activities during the previous calendar year and shall include the following information:

     (i) Name and address of the facility;

     (ii) Calendar year covered by the report;

     (iii) Results of groundwater monitoring in accordance with WAC 173-350-500;

     (iv) Results of leak detection system monitoring, if applicable; and

     (v) Any additional information required by the jurisdictional health department as a condition of the permit.

     (e) Develop, keep and abide by a plan of operation approved as part of the permitting process. The plan shall describe the facility's operation and shall convey to site operating personnel the concept of operation intended by the designer. The plan of operation shall be available for inspection at the request of the jurisdictional health department. If necessary, the plan shall be modified with the approval, or at the direction of the jurisdictional health department. Each plan of operation shall include the following:

     (i) A description of the types of solid waste to be handled at the facility;

     (ii) A description of how wastes are handled on-site during the facility's active life;

     (iii) A description of how equipment, structures and other systems are to be inspected and maintained, including the frequency of inspection and inspection logs. This description shall include:

     (A) The groundwater monitoring system, if required;

     (B) The overfilling prevention equipment, including details of filling and emptying techniques;

     (C) The liners and embankments, tank piping and secondary containment;

     (D) Safety and emergency plans;

     (E) The forms used to record weights and volumes; and

     (F) Other such details to demonstrate that the facility will be operated in accordance with this subsection and as required by the jurisdictional health department.

     (5) Surface impoundments and tanks - Groundwater monitoring requirements.

     (a) Surface impoundments not equipped with a leak detection layer are subject to the groundwater monitoring requirements of WAC 173-350-500.

     (b) Surface impoundments equipped with a leak detection layer and tanks are not subject to the groundwater monitoring requirements of this chapter; however, surface impoundments must meet the requirements provided under WAC 173-350-040(5).

     (6) Surface impoundments and tanks - Closure requirements. The owner or operator of a surface impoundment or tank shall:

     (a) Notify the jurisdictional health department sixty days in advance of closure. All waste from the surface impoundment or tank shall be removed to a facility that conforms with the applicable regulations for handling the waste.

     (b) Develop, keep and abide by a closure plan approved by the jurisdictional health department as part of the permitting process. At a minimum, the closure plan shall include the methods of removing waste.

     (7) Surface impoundments and tanks - Financial assurance requirements. There are no specific financial assurance requirements for surface impoundments or tanks subject to this chapter; however, surface impoundments and tanks must meet the requirements provided under WAC 173-350-040(5).

     (8) Surface impoundments and tanks - Permit application contents.

     (a) The owner or operator of a surface impoundment or tank shall obtain a solid waste permit from the jurisdictional health department. All applications for permits shall be submitted in accordance with the procedures established in WAC 173-350-710. In addition to the requirements of WAC 173-350-710 and 173-350-715, each application for a permit shall contain:

     (i) Engineering reports/plans and specifications that address the design standards of subsection (3) of this section;

     (ii) A plan of operation meeting the requirements of subsection (4) of this section;

     (iii) For surface impoundments not equipped with a leak detection layer, hydrogeologic reports and plans that address the requirements of subsection (5) of this section;

     (iv) A closure plan meeting the requirements of subsection (6) of this section.

     (9) Surface impoundments and tanks - Construction records. The owner or operator of a surface impoundment or tank shall provide copies of the construction record drawings for engineered facilities at the site and a report documenting facility construction, including the results of observations and testing carried out as part of the construction quality assurance plan, to the jurisdictional health department and the department. Facilities shall not commence operation until the jurisdictional health department has determined that the construction was completed in accordance with the approved engineering report/plans and specifications and has approved the construction documentation in writing.



[Statutory Authority: Chapter 70.95 RCW. 03-03-043 (Order 99-24), § 173-350-330, filed 1/10/03, effective 2/10/03.]