SECTION 165:10-9-1. Use of commercial pits

(a)   Scope. This Section shall cover the permitting, construction, operation, and closure requirements for any commercial pit. A commercial pit is a disposal facility which is authorized by Commission order and used for the disposal, storage, and handling of deleterious substances or soils contaminated by deleterious substances produced, obtained, or used in connection with drilling, production and/or pipeline construction operations. This does not cover disposal well pits. (See 165:10-9-3 and 165:10-7-20.)

(b)   Application requirements.

(1)   Who may apply. The applicant for a commercial pit shall be the owner of the land (or person having a written firm option to purchase the land at the time the application is filed) on which the proposed pit is to be located: if leased, both the owner and lessee shall be joint applicants.

(2)   Compliance with rules. Before issuance of an order, the applicant shall comply with Commission Rules of Practice 165:5-7-1, 165:5-7-35, 165:5-3-1, and this Section. Subsequent to issuance of an order authorizing commercial pit(s) and prior to commencing construction of such pit(s), the applicant is required to submit a recorded copy of a deed to the Conservation Division reflecting that the applicant owns the land which is to be used for the commercial pit facility.

(3)   Exhibits. Two complete sets of all exhibits which shall be relied upon by the applicant shall be submitted to the Pollution Abatement Department of the Commission, pursuant to 165:5-7-35. Those exhibits shall include, but are not limited, to the following:

(A)   A lithologic log of test borings, identifying the subsurface materials encountered and the depth at which groundwater was encountered pursuant to (c)(2)(D) of this Section.

(B)   Results of permeability tests of the proposed liner materials, pursuant to (e)(7) of this Section.

(C)   A topographic map of the commercial pit site.

(D)   The appropriate Soil Conservation Service (SCS) soil survey aerial photo and legend.

(E)   A detailed drawing of the site, with complete construction plans drawn to scale by or under the supervision of a registered professional engineer.

(F)   A plan for closure of the pit(s) which shall provide for a minimum three feet of soil cover and shall specifically state how all aspects of closure shall be accomplished, including volume and fate of liquids and solids, earthwork to close the pit(s) (including placement of stockpiled topsoil), and revegetation of the site.

(G)   An itemization of projected hauling, closure, reclamation, maintenance, and monitoring costs.

(H)   A plan for post-closure maintenance and monitoring which shall address maintenance of the site as well as monitoring and plugging of wells. Exemption from the plugging of monitor wells may be obtained upon written request and approval of the Manager of Pollution Abatement.

(I)   A plan for operation which shall address the method(s) by which excess water will be disposed.

(c)   Restrictions.

(1)   Order required. No commercial earthen pit shall be constructed, enlarged, reconstructed, or used without a Commission order.

(2)   Site limitations.

(A)   No commercial earthen pit shall be constructed or used unless an investigation of the soils, topography, geology, and hydrology conclusively shows that storage of water-based drilling fluids and/or cuttings at the site will not be harmful to groundwater, surface water, soils, plants, or animals in the surrounding area. No abandoned mine, strip pit, quarry, canyon, or streambed shall be used for disposal of oilfield wastes, nor shall a pit be constructed or used in such a setting.

(B)   No commercial pit shall be constructed or used on any site that is located within a 100-year flood plain.

(C)   No commercial pit shall be constructed or used within a wellhead protection area (WPA) as identified by the Wellhead Protection Program (42 USC Section 300h-7, Safe Drinking Water Act), or within one mile of a public water well for which the WPA has not been delineated.

(D)   No commercial pit shall be constructed unless it can be shown that there will be a minimum of 25 feet between the bottom of the pit and the groundwater level. To ascertain this and to demonstrate the subsurface profile of the site, a minimum of three test borings (the exact number of locations to be determined by the Pollution Abatement Department) shall be drilled to a minimum depth of 25 feet below the proposed bottom of the pit and into the first free water encountered. Perched water tables are not considered for the purposes of this subparagraph. Test borings need not extend deeper than 50 feet below the bottom of the pit if free water has not been encountered before that depth. All boreholes converted to monitor wells shall conform to (e)(15) of this Section. All boreholes not converted to monitor wells shall be plugged from top to bottom with bentonite, cement, and/or other method approved by the Pollution Abatement Department within 30 days of drilling completion.

(E)   No commercial pit shall be constructed or used within the following distances from the city limits of an incorporated municipality unless previously authorized by Commission order:

(i)   Three miles if population is 20,000 or less.

(ii)   Five miles if population is greater than 20,000.

(F)   The construction, enlargement, reconstruction or operation of any commercial pit in any area listed in OAC 165:10-29-3 is prohibited.

(3)   Means of water disposal. No commercial pit shall be constructed or used unless the operator can show that there will be an ongoing means of disposal of excess water pursuant to (b)(3)(I) of this Section.

(d)   Surety requirements.

(1)   Agreement with Commission. Any operator of a commercial pit shall file with the Surety Department for the Conservation Division an agreement to properly close and reclaim the site in accordance with approved closure and reclamation procedures upon termination of disposal operations due to abandonment, shutdown, full pits, or other reason. The agreement shall be on forms available from the Conservation Division and shall be accompanied by surety. The agreement shall provide that if the Commission finds that the operator has failed or refused to close the pits or take remedial action as required by law and the rules of the Commission, the surety shall pay to the Commission the full amount of the operator's obligation up to the limit of the surety.

(2)   Surety amount and type. The Commission shall establish the amount of surety in the order for the authority to construct, enlarge, or operate a commercial pit. The amount of surety shall be based on factors such as dimensions of the pit and costs of hauling, closure, reclamation, and monitoring. The amount may be subject to change for good cause. Upon approved closure of a pit, the Manager of Pollution Abatement may administratively reduce the surety requirement to an amount which would cover the cost of monitoring the site and plugging the monitor wells. Surety shall be maintained for as long as monitoring is required. The type of surety shall be a corporate surety bond, certificate of deposit, irrevocable letter of credit, or other type of surety approved for the pit by order of the Commission. Any type of surety that expires shall be renewed prior to 30 days before the expiration date.

(3)   Posting surety before permit is issued. An operator shall post surety with the Commission before a construction permit is issued, pursuant to (e)(1) of this Section.

(e)   Construction requirements.

(1)   Permit required. Prior to constructing any pit, a commercial pit operator shall obtain a permit from the Manager of Pollution Abatement. Application shall be made on Form 1014N. For use of a commercial pit without a permit, the pit operator may be fined up to $5,000.00.

(2)   Runoff water prohibited. No runoff water from surrounding land surfaces shall be allowed to enter a pit.

(3)   Stockpiling of topsoil. Prior to constructing a pit, all topsoil within the top twelve inches of soil on the site shall be stockpiled for use as the final cover at the time of closure. The topsoil may be stockpiled in the outside slopes of the berms, provided it is not used for structural purposes and can be readily distinguishable from other soil materials at the time of closure. In cases where topsoil is stockpiled in the berms, it shall be shown in the as-built drawings pursuant to (e)(16) of this Section.

(4)   Monitoring by engineer. A registered professional engineer or an engineer-in-training working under the supervision of a registered professional engineer (RPE) shall monitor the construction of any commercial pit to assure that approved design specifications and Commission rules are adhered to. A minimum of six on-site visits to the site shall be made; two pre-construction, two during construction, and two post-construction. At least the post-construction on-site visit shall be made by the RPE.

(5)   Maximum fluid depth. Any pit shall be constructed to contain a maximum fluid or sediment depth of seven feet, with a minimum freeboard of three feet.

(6)   Maximum dimensions. Any pit shall not be constructed to dimensions greater than that approved in the order. Furthermore, the maximum width of a pit or pit cell shall not exceed 175 feet if closure must be accomplished from one side or two adjacent sides; 350 feet if closure can be accomplished from at least two opposite sides or three adjacent sides. Pit dimensions shall be measured at the maximum allowable fluid level.

(7)   Soil liners.

(A)   Soil materials to be used in a soil liner shall undergo permeability testing before construction. Pre-construction permeability testing shall consist of laboratory permeability tests on at least two specimens of representative soil liner materials compacted in the laboratory to approximately 95 percent of the material's Standard Proctor Density (ASTM D-698).

(B)   Laboratory permeability test procedures must conform to one of the methods described for fine-grained soils in the Corps of Engineers Manual EM-1110-2-1906 Appendix VII. In no case shall the pressure differential across the specimen exceed five feet of water per inch of specimen length.

(C)   If permeability testing shows that addition of bentonite or other approved material is needed to assist the native soils in meeting the permeability standard, it shall be applied at a minimum rate specified by the testing or engineering firm. Any bentonite used for liner material shall not have been previously used in drilling muds.

(D)   Any soil liner shall be constructed by disturbing the soil to the depth of the bottom of the liner, applying fresh water as necessary to the soil materials to achieve a moisture content wet of optimum, then recompacting it with heavy construction equipment, such as a footed roller, until the required density is achieved, pursuant to (H) of this paragraph. The liner shall be constructed in maximum six inch lifts (after compaction), with each lift being scarified before placement of the next lift.

(E)   Any soil liner shall cover the bottom and interior sides of the pit entirely.

(F)   Any soil liner shall be installed on a slope no steeper than 3:1 (horizontal to vertical).

(G)   Any soil liner shall have a minimum thickness of 18 inches (after compaction) and shall have a maximum coefficient of permeability of 1.0 x 10^-7 cm/sec.

(H)   Any soil liner shall be field tested for compaction, unless a post-construction permeability test is performed pursuant to (I) of this paragraph.

(i)   A minimum of six compaction tests shall be performed on any soil liner; a minimum of four widely spaced tests in the bottom of the pit and two tests on different slopes of the pit are required, unless otherwise directed by a Conservation Division representative. Particular emphasis shall be placed on selecting locations for compaction tests where nonuniformity in soil texture or color can be observed.

(ii)   Compaction tests shall be conducted in accordance with ASTM methods D-2922 or D-1556.

(iii)   The soil materials of any liner shall be compacted to at least 95 percent of the Standard Proctor Density.

(I)   Post-construction permeability testing shall consist of at least two laboratory permeability tests on undisturbed samples of the completed soil liner.

(i)   Particular emphasis shall be placed on selecting the location(s) for permeability tests or test samples where nonuniformity in soil texture or color can be observed.

(ii)   Field permeability tests shall be conducted only by the double ring infiltrometer method as described in ASTM D-3385. Permeability tests may be discontinued prior to flow stabilization upon satisfactory evidence that the permeability rate is less than 1.0 x 10^-7 cm/sec.

(8)   Geomembrane liners.

(A)   Any geomembrane liner that is installed in a commercial pit shall have a minimum thickness of 40 mil.

(B)   Any geomembrane liner used in a commercial pit shall be chemically compatible with the type of substances to be contained and shall have ultraviolet light protection.

(C)   Any geomembrane liner shall be placed over a specially prepared, smooth, compacted surface void of sharp changes in elevation, rocks, clods, organic debris, or other objects.

(D)   Any geomembrane liner shall be continuous, although it may include welded or extruded seams, and shall cover the bottom and interior sides of the pit entirely. Sewing of seams is prohibited. The edges shall be securely placed in a minimum twelve inch deep anchor trench around the perimeter of the pit.

(9)   Width of the crown. The crown (top) of any berm shall be a minimum of eight feet in width.

(10)   Slopes. The inside slope of any exterior berm (having fluid on one side) shall not be steeper than 3:1 (horizontal to vertical) and the outside slope 2.5:1. The slopes of any interior berm (having fluid on both sides) shall not be steeper than 3:1.

(11)   Earthwork compaction. All earthwork, except as noted in (7)(H)(iii) of this subsection, shall be compacted to achieve a minimum 90% Standard Proctor Density and shall be applied in lifts where some method of bonding is achieved between lifts, with each lift not to exceed eight inches prior to compaction.

(12)   Pipe installation. Any pipe, tinhorn, culvert, or conduit in the berm between two adjoining pits shall be placed so that there is a minimum of 36 inches between the top of the pipe, tinhorn, culvert, or conduit and the lowest point in the top of the berm separating the pits.

(13)   Splash pad. All pits which receive fluids directly from a vacuum truck shall have a splash pad at the point where fluids are received unless a waiver is obtained from the Manager of Pollution Abatement by showing that erosion of the liner will not occur. The pad must be constructed of materials and to the dimensions necessary to effectively prevent the liner from eroding.

(14)   Fluid level marker. A minimum of one stationary fluid level marker shall be erected in each pit or cell. The marker shall be erected in a location within the pit or cell where it can be easily observed. The marker shall be of such design that the maximum fluid level at any time may be clearly identified. Details of the proposed marker installation shall be approved by the Manager of Pollution Abatement prior to installation. Markers shall be installed under the supervision of a registered professional engineer, licensed land surveyor, or other person approved by the Manager of Pollution Abatement prior to installation.

(15)   Monitor wells. All commercial pits shall have a minimum of three monitor wells installed- one upgradient and two downgradient from the pit. The exact number and location of wells shall be approved by the Pollution Abatement Department prior to installation. No monitor well shall be installed more than 250 feet from the toe of the outside berm of a commercial pit, nor shall any existing water well be used as a monitor well unless approved by the Manager of Pollution Abatement. Monitor wells installed prior to the effective date of this Section may be accepted by the Manager of Pollution Abatement if it can be shown that they adequately monitor a site. All new monitor wells shall be drilled to a depth of at least ten feet below the top of the first free water encountered, and all monitor wells shall be drilled to a depth of at least ten feet below the base of the pit. All new monitor wells shall be drilled and completed by a licensed monitor well driller. If documentation is submitted to the Manager of Pollution Abatement prior to drilling the monitor wells to show that no free water will be encountered within 50 feet below the bottom of the pit, the Manager of Pollution Abatement may require that monitor wells be drilled to a lesser depth. All new monitor wells shall meet the requirements as set out in rules established by the Oklahoma Water Resources Board, in addition to the following requirements:

(A)   A removable and lockable cap shall be placed on top of the casing. The cap shall remain locked at all times, except when the well is being sampled.

(B)   Within 30 days of installation, specific completion information, a diagram of the locations and numerical labeling for all monitor wells shall be submitted to the Manager of Pollution Abatement.

(16)   As-built drawing. A detailed, as-built drawing of the pit(s) and monitor wells by or under the supervision of a registered professional engineer shall be submitted to the Manager of Pollution Abatement before operation of the pit(s) commences.

(17)   Liner certification. An affidavit signed by the person who was responsible for installing the pit liner, certifying that the liner meets minimum requirements and was installed in accordance with Commission rules, shall be submitted to the Manager of Pollution Abatement before operation of the pit commences. Supporting documentation shall also be submitted, such as post-construction permeability or compaction test results, bentonite receipts, and geomembrane liner specifications from the manufacturer.

(18)   Pit approval. Acceptance of fluids into a pit shall not commence until a representative of the Conservation Division has inspected and approved the pit.

(19)   Hydrologically sensitive areas. If the proposed site is known to be located over a hydrologically sensitive area, in addition to the foregoing construction requirements, the additional requirements shall apply:

(A)   The total depth of a pit shall not exceed eight feet, and the total designed fluid or sediment depth shall not exceed five feet.

(B)   A soil liner having a minimum thickness of three feet and a coefficient of permeability no greater than 1.0 x 10^-8 cm/sec or a minimum 60-mil geomembrane liner shall be required.

(C)   The Manager of Pollution Abatement shall determine the minimum depth of all monitor wells.

(f)   Operation and maintenance requirements.

(1)   Vegetative cover. Vegetative cover shall be established on all areas of earthfill immediately after pit construction or during the first planting season if pit construction is completed out of season. The cover shall be sufficient to protect those areas from soil erosion and shall be maintained.

(2)   Fencing. All commercial facilities shall be completely enclosed by a fence at least four feet in height. No livestock shall be allowed inside the fence.

(3)   Sign. A waterproof sign bearing the name of the operator, legal description, most current order number, and emergency phone number shall be posted within 25 feet of the entrance gate to any commercial pit and shall be readily visible.

(4)   Site security. Dumping into a commercial pit shall occur only when there is an attendant on duty. All sites shall be secured by a locked gate when an attendant is not on duty. A key or combination to the lock shall be provided to the appropriate Field Inspector for the purpose of carrying out inspections.

(5)   Fluid level. Drilling fluids and/or cuttings shall not be accepted into a commercial pit unless the fluid level can be maintained at an elevation no higher than the maximum level of the fluid level marker.

(6)   Acceptable materials.

(A)   No operator of a commercial pit shall receive any substances other than water-based drilling fluids and/or cuttings or salt contaminated soils.

(B)   No operator of a pit permitted prior to July 9, 1987, shall receive fluids and/or cuttings with a chloride content greater than 3500 mg/l. No operator of a pit permitted after July 9, 1987, shall receive fluids and/or cuttings with a chloride content greater than 5000 mg/l.

(C)   A sample from each incoming load shall be collected, filtered using a standard API filter press, and tested for chlorides.

(D)   The date, volume, source, and chloride level of each load received shall be entered into a log book. The log book shall be available for inspection by a representative of the Conservation Division of the Commission at all times. Log books shall be kept for a minimum of five years after closure is completed.

(7)   Pit contents. No pit permitted prior to July 9, 1987, shall contain fluids and/or cuttings with a chloride content greater than 5,000 mg/l. No pit permitted after July 9, 1987, shall contain fluids and/or cuttings with a chloride content greater than 10,000 mg/l. The contents of each pit or pit cell shall be sampled and analyzed by the operator at least once every six months (during January and July) after operations commence. More frequent sampling may be required by the Manager of Pollution Abatement. The following procedures shall be used:

(A)   The appropriate Field Inspector shall be notified at least 24 hours in advance of sampling to allow a Commission representative an opportunity to witness the sampling.

(B)   Samples shall be collected and handled by the operator according to EPA-approved standards. (RCRA Groundwater Monitoring Technical Enforcement Guidance Document, EPA, OSWER-9950.1, September 1986, pp. 99-107.)

(C)   A minimum of five samples per 50,000 bbls., or part thereof, is required for each pit or pit cell. Samples must be taken from different horizontally and vertically distributed locations in each pit or pit cell.

(D)   The samples shall be combined and thoroughly mixed, then a minimum two pint composite sample taken for analysis.

(E)   If requested by a representative of the Conservation Division, each composite sample shall be split and an adequate portion (approximately one pint) shall be properly labeled and delivered or otherwise provided to the appropriate Conservation Division District Office or Field Inspector.

(F)   All samples delivered to the laboratory shall be accompanied by a chain of custody form. The chain of custody form and sample analyses must be submitted to the Conservation Division.

(G)   All composite samples must be analyzed for chlorides, pH and TDS by a laboratory certified by the Oklahoma Department of Environmental Quality or operated by the State of Oklahoma. Analysis of additional parameters may be required, as determined by the Manager of Pollution Abatement.

(H)   A copy of each analysis shall be forwarded to the Pollution Abatement Department within 30 days of sampling.

(8)   Oil film.

(A)   No commercial pit shall contain an oil film covering more than one percent of the surface area of the pit.

(B)   The protection of migratory birds shall be the responsibility of the operator. Therefore, the Conservation Division recommends that to prevent the loss of birds, oil films be removed, or the surface area covered by the film be protected from access to birds. (See Advisory Notice in 165:10-7-3(c).)

(9)   Aesthetics. All commercial pit sites shall be maintained so that there is no junk iron or cable, oil or chemical drums, paint cans, domestic trash, or debris on the premises.

(10)   Structural integrity. All commercial pits shall be used, operated, and maintained at all times so as to prevent the escape of their contents. All erosion, cracking, sloughing, settling, animal burrows, or other condition that threatens the structural stability of any earthfill shall be repaired immediately upon discovery.

(11)   Monitor wells. Sampling of monitor wells shall begin prior to accepting any drilling fluids and/or cuttings into a new facility and within 30 days of drilling completion on existing facilities, and shall be done at least once every six months (during January and July) after operations commence until three years after closure is completed. Sampling of greater frequency of duration may be required by the Manager of Pollution Abatement. The following procedures shall be used:

(A)   The appropriate Field Inspector shall be notified at least 24 hours in advance of sampling to allow a Commission representative an opportunity to witness the sampling.

(B)   Samples shall be collected and handled by the operator according to EPA-approved standards. (RCRA Groundwater Monitoring Technical Enforcement Guidance Document, EPA, OSWER-9950.1, September 1986, pp. 99-107.)

(C)   If requested by a representative of the Conservation Division, an adequate portion of each sample (approximately one pint) shall be properly labeled and delivered or otherwise provided to the appropriate Conservation Division District Office or Field Inspector.

(D)   All samples delivered to the laboratory shall be accompanied by a chain of custody form. The chain of custody form and sample analyses must be submitted to the Conservation Division.

(E)   All samples must be analyzed for pH, chlorides and TDS by a laboratory certified by the Oklahoma Department of Environmental Quality or operated by the State of Oklahoma. Analysis of additional parameters may be required based on the operation of the facility as determined by the Manager of Pollution Abatement.

(F)   A copy of each analysis and a statement as to the depth to groundwater encountered in each well, or a written statement that no water was encountered, shall be forwarded to the Pollution Abatement Department within 30 days of sampling.

(12)   Prevention of pollution. All commercial pits shall be used, operated, and maintained at all times so as to prevent pollution. In the event of a nonpermitted discharge from a commercial pit, sufficient measures shall be taken to stop or control the loss of materials, and reporting procedures in 165:10-7-5(c) shall be followed. Any materials lost due to such discharge shall be cleaned up as directed by a representative of the Conservation Division. For a willful non-permitted discharge, the pit operator may be fined up to $5,000.00.

(g)   Semiannual report. The operator of any commercial pit shall submit a semiannual report on Form 1014A to the Manager of Pollution Abatement by February 1 and August 1 of each year.

(h)   Closure requirements.

(1)   Notification. The Manager of Pollution Abatement shall be notified in writing whenever a commercial pit becomes inactive, is abandoned, full of sediment, or operation of the pit ceases for any reason. A commercial pit may be considered to be inactive by the Commission if:

(A)   The pit has been shut down by the Commission because of a violation which results in the filing of an application for an order to vacate the operator's authority.

(B)   The authority to operate has been terminated by failure to comply with (j) of this Section.

(C)   The operator is unable to furnish documentation to show that there has been receipt of drilling fluids and/or cuttings into the pit during the previous twelve months.

(2)   Time limit. Closure of all commercial pits shall be commenced within 60 days and completed within one year of cessation of pit operations, pursuant to (1) of this subsection. In cases where extenuating circumstances arise, one extension of six months may be administratively approved in writing by the Manager of Pollution Abatement. Closure shall be in accordance with an approved closure plan. A progress report shall be submitted to the Manager of Pollution Abatement, every three months (during January, April, July, and October) after cessation of pit operations until closure is completed.

(3)   Restrictive covenant. A restrictive covenant shall be filed with the County Clerk of the county in which a commercial pit is located. The document shall accurately describe the pit location and shall specifically restrict the current or future landowners of the pit site from puncturing the final cover of the pit or otherwise disturbing the site to the extent that pollution could occur.

(4)   Penalty for failure to meet closure requirements. An operator failing to meet the closure requirements set out in this subsection may be fined up to $1,000.00.

(i)   Additional requirements. The requirements set forth in this Section are minimum requirements. Additional requirements may be made upon a showing of good cause that an operator has a history of complaints for failure to comply with Commission rules and regulations, the site has certain limitations, or other conditions of risk exist.

(j)   Application to existing pits. Subsections (a), (c)(1), (d), (e), (f), (g), (h), and (i) of this Section shall apply to all commercial pits permitted or ordered prior to the adoption of this Section. All pits permitted, but yet to be constructed as of the effective date of this Section, shall be subject to all of the construction requirements under (e) of this Section.

(k)   Variances. Except as otherwise provided in this Section, variances from provisions of this Section may be granted for good cause by order after application, notice, and hearing.

(l)   Compliance history. In the event the Commission has evidence that an applicant for a commercial disposal pit may not possess a satisfactory compliance history with Commission rules, the Director of the Conservation Division may seek an order of the Commission, issued after application, notice, and hearing, determining whether the applicant should be authorized to operate such a facility.

[Source: Amended at 9 Ok Reg 2295, eff 6-25-92; Amended at 9 Ok Reg 2337, eff 6-25-92; Amended at 25 Ok Reg 2187, eff 7-11-08; Amended at 27 Ok Reg 2128, eff 7-11-10; Amended at 28 Ok Reg 1949, eff 7-11-11; Amended at 29 Ok Reg 950, eff 7-1-12; Amended at 30 Ok Reg 1041, eff 7-1-13; Amended at 32 Ok Reg 768, eff 8-27-15; Amended at 33 Ok Reg 593, eff 8-25-16; Amended at 34 Ok Reg 921, eff 9-11-17; Amended at 35 Ok Reg 973, eff 9-14-18; Amended at 36 Ok Reg 534, eff 8-1-19; Amended at 37 Ok Reg 1121, eff 1-1-20]