Repairing, Sealing or Draining a Pond: Federal Rules and NRCS Standards

Key points

• ProcessEPA says many Clean Water Act programs apply only to 'waters of the United States'. As of its page last updated September 9, 2026, EPA says the agencies are implementing the January 2023 rule, as amended by the conforming rule, in 24 states, the District of Columbia, and the U.S. Territories, and in the other 26 states are interpreting 'waters of the United States' consistent with the pre-2015 regulatory regime and the Supreme Court's decision in Sackett. On September 9, 2026 the agencies published a supplemental notice of proposed rulemaking for an updated definition of 'waters of the United States', supplementing their November 2025 proposal (proposed only; not in effect).

  EPA, About Waters of the United States (last updated Sept. 9, 2026), introductory notice and 'What are' / 'Current Implementation' sections [1]
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  On September 9, 2026, ... published a supplemental notice of proposed rulemaking for the Updated Definition of "Waters of the United States." The notice supplements the agencies' November 2025 proposal. ... Many Clean Water Act programs apply only to “waters of the United States.” ... implementing the January 2023 Rule, as amended by the conforming rule, in 24 states, the District of Columbia, and the U.S. Territories. In the other 26 states, the agencies are interpreting "waters of the United States" consistent with the pre-2015 regulatory regime and the Supreme Court's decision in Sackett

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• ExemptionWhere the Amended 2023 Rule applies, 'artificial lakes or ponds created by excavating or diking dry land to collect and retain water and which are used exclusively for such purposes as stock watering, irrigation, settling basins, or rice growing' are not waters of the United States even if they would otherwise meet paragraphs (a)(2) through (a)(5) of the definition. Also excluded are artificial reflecting or swimming pools or other small ornamental bodies of water created by excavating or diking dry land to retain water for primarily aesthetic reasons.

  Applies when: States where the agencies implement the Amended 2023 Rule (24 states, the District of Columbia and the U.S. Territories per EPA's About WOTUS page, claim 051); in the other 26 states the agencies interpret 'waters of the United States' consistent with the pre-2015 regime and Sackett. 33 CFR 328.3(b)(5)-(6) (88 FR 3142, Jan. 18, 2023, as amended 88 FR 61968, Sept. 8, 2023) [5]
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  (b) The following are not “waters of the United States” even where they otherwise meet the terms of paragraphs (a)(2) through (5) of this section: ... (5) Artificial lakes or ponds created by excavating or diking dry land to collect and retain water and which are used exclusively for such purposes as stock watering, irrigation, settling basins, or rice growing; (6) Artificial reflecting or swimming pools or other small ornamental bodies of water created by excavating or diking dry land to retain water for primarily aesthetic reasons;

  Open eCFR / Office of the Federal Register (opens in a new tab)

• The artificial lakes and ponds exclusion applies only to features excavated in dry land or diked in dry land; paragraph (a)(2) impoundments of waters of the United States (e.g., a pond made by damming a jurisdictional stream) are not covered. Ponds that satisfy the exclusion are not jurisdictional even if they have a hydrologic surface connection to waters of the United States, and non-jurisdictional conveyances created in dry land that are physically connected to and part of the excluded feature remain excluded.

  Applies when: Relevant to embankment ponds built across a drainage: an on-stream impoundment of a jurisdictional water is not an excluded artificial pond. 88 FR 3004, 3116 (Jan. 18, 2023) (preamble) [6]
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  Paragraph (a)(2) impoundments are not covered under this exclusion. This exclusion only applies to features that were excavated in dry land or were diked in dry land. Paragraph (a)(2) impoundments are not excavated in dry land or diked in dry land. ... Artificial lakes and ponds that satisfy the terms of the exclusion would not be jurisdictional under this rule even if they have a hydrologic surface connection to ``waters of the United States.'' Non-jurisdictional conveyances created in dry land that are physically connected to and are a part of the excluded feature remain excluded.

  Open Federal Register (govinfo) (opens in a new tab)

• StatusThe 2023 preamble says that under the pre-2015 regulatory regime, the features it lists, including artificial ponds dug or diked in dry land and used exclusively for stock watering, irrigation, settling basins or rice growing, were 'generally not considered' waters of the United States, but the Corps reserved the right to decide on a case-by-case basis that a particular waterbody in these categories is a water of the United States. The 2023 rule codified the exclusions and removed that case-by-case possibility (only where the 2023 rule is operative).

  Applies when: Background for the 26 states where the agencies interpret 'waters of the United States' consistent with the pre-2015 regime and Sackett (EPA's About WOTUS page, claim 051); the removal of case-by-case review applies only where the 2023 rule is implemented. 88 FR 3004, 3111 (Jan. 18, 2023) (preamble, describing 51 FR 41217, Nov. 13, 1986) [6]
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  artificial lakes or ponds created by excavating or diking dry land ... used exclusively for such purposes as stock watering, irrigation, settling basins, or rice growing; ... Under the pre-2015 regulatory regime, the features listed above were generally not considered ``waters of the United States'' ... the Corps reserves the right on a case-by-case basis to determine that a particular waterbody within these categories of waters is a water of the United States. ... removing the possibility that these waters could be found jurisdictional on a case-by-case basis.

  Open Federal Register (govinfo) (opens in a new tab)

• StatusWhen excluded status ends: the agencies' 2023 rule preamble says that if an artificial pond excavated to collect and retain water is initially used exclusively for stock watering, irrigation, settling basins, or rice growing but is later used for a different purpose, then, consistent with longstanding practice, a previously excluded feature that no longer meets the terms of the exclusion is no longer excluded, and it would be jurisdictional if it otherwise meets the definition of 'waters of the United States'.

  88 FR 3004, 3116 (Jan. 18, 2023) (preamble, sec. IV.C.7.b(3) Implementation) [6]
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  if an artificial pond created by excavating land to collect and retain water is initially used exclusively for stock watering, irrigation, settling basins, or rice growing but is subsequently used for a different purpose, ... Consistent with the agencies' longstanding practice, if a previously excluded feature no longer meets the terms of the exclusion, it is no longer excluded. If it no longer satisfies the terms of an exclusion, it would be jurisdictional if it otherwise meets the definition of ``waters of the United States'' under this rule.

  Open Federal Register (govinfo) (opens in a new tab)

• RequirementExcept as in compliance with the listed Clean Water Act sections, including section 402 (33 U.S.C. 1342, NPDES) and section 404 (33 U.S.C. 1344, dredged or fill material), the discharge of any pollutant by any person is unlawful.

  33 U.S.C. 1311(a) [2]
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  Except as in compliance with this section and sections 1312, 1316, 1317, 1328, 1342, and 1344 of this title, the discharge of any pollutant by any person shall be unlawful.

  Open Office of the Law Revision Counsel, U.S. House of Representatives (opens in a new tab)

• ProcessExcept as provided in 33 CFR 323.4 (discharges not requiring permits), Department of the Army permits are required for discharges of dredged or fill material into waters of the United States. Certain discharges are permitted by the nationwide permits in 33 CFR part 330, others may be authorized by district or division engineers on a regional basis (regional permits), and a discharge that is neither exempted by 323.4 nor permitted by part 330 requires an individual or regional section 404 permit.

  Applies when: Only where the pond (or the area worked in) is a 'water of the United States'. 33 CFR 323.3(a) [4]
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  (a) General. Except as provided in § 323.4 of this part, DA permits will be required for the discharge of dredged or fill material into waters of the United States. Certain discharges specified in 33 CFR part 330 are permitted by that regulation (“nationwide permits”). Other discharges may be authorized by district or division engineers on a regional basis (“regional permits”). If a discharge of dredged or fill material is not exempted by § 323.4 of this part or permitted by 33 CFR part 330, an individual or regional section 404 permit will be required

  Open eCFR (Office of the Federal Register) (opens in a new tab)

• RequirementRGL 05-04 policy: as a general rule, discharging substantial quantities of accumulated bottom sediment from or through a dam into downstream waters is a discharge of dredged material (and possibly fill material) that requires a CWA section 404 permit, and will rarely, if ever, qualify for the 404(f) exemption; a Section 10 (Rivers and Harbors Act) permit may also be required in navigable waters of the United States, where no statutory exemptions apply.

  USACE RGL 05-04 (Aug. 19, 2005), para. 4.a [7]
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  As a general rule, the discharge of substantial quantities of accumulated bottom sediment from or through a dam into downstream waters constitutes a discharge of dredged material (and possibly of fill material) that requires a CWA Section 404 permit. The discharge of substantial quantities of sediment through a dam will rarely, if ever, qualify as exempt under 404(f). Such activities may also require a DA Section 10 permit if they occur in “navigable waters of the United States”, and no statutory exemptions apply to Section 10 for such discharges into navigable waters.

  Open U.S. Army Corps of Engineers (opens in a new tab)

• ExemptionRGL 05-04 lists activities that are not usually considered regulated discharges of dredged material and do not require DA permits, including: operation of continuously sluicing structures that mimic the natural increase and decrease of sediment in a stream (sediment discharged comparable to the amount entering the reservoir from upstream); breaching or removal of a dam that moves only de minimis amounts of material or results solely from an act of nature; releases during high water or flood stages to pass flood waters; and 'the lowering of lake or pond levels that results in the release of only de minimis amounts of sediment.' The RGL does not set a specific amount of sediment that is de minimis.

  Applies when: Pond drawdowns that release only de minimis sediment USACE RGL 05-04 (Aug. 19, 2005), para. 4.b [7]
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  not usually considered regulated discharges of dredged material and do not require DA permits include actions such as the operation of continuously sluicing structures that mimic the natural increase and decrease of sediment in a stream ... comparable to the amount of material entering the reservoir from upstream); breaching or removal of a dam that results in the movement of only de minimis amounts of material ... flood stages ... the lowering of lake or pond levels that results in the release of only de minimis amounts of sediment. ... not propose to set a specific amount of sediment

  Open U.S. Army Corps of Engineers (opens in a new tab)

• ExemptionClean Water Act section 404(f)(1)(C) provides that the discharge of dredged or fill material for the purpose of construction or maintenance of farm or stock ponds or irrigation ditches, or the maintenance of drainage ditches, is not prohibited by or otherwise subject to regulation under section 404, section 301(a) or section 402 (except for effluent standards or prohibitions under section 307), unless recaptured under section 404(f)(2).

  Applies when: Farm or stock ponds that are waters of the United States (an excluded pond needs no exemption). 33 U.S.C. 1344(f)(1)(C) and closing text [10]
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  (1) Except as provided in paragraph (2) of this subsection, the discharge of dredged or fill material- ... (C) for the purpose of construction or maintenance of farm or stock ponds or irrigation ditches, or the maintenance of drainage ditches; ... is not prohibited by or otherwise subject to regulation under this section or section 1311(a) or 1342 of this title (except for effluent standards or prohibitions under section 1317 of this title).

  Open Office of the Law Revision Counsel, U.S. House of Representatives (opens in a new tab)

• AgencyEPA's section 404 exemptions page lists 'construction and maintenance of farm or stock ponds' and 'maintenance of structures such as dams, dikes, and levees' among activities exempt under section 404(f)(1), and explains that if an activity listed as exempt represents a new use of the water and the activity would result in a reduction in reach or impairment of flow or circulation of regulated waters, including wetlands, the activity is not exempt; both conditions must be met for the activity to be considered non-exempt. It directs people to their local Corps district office or EPA regional office to find out whether specific activities are exempt.

  EPA, Exemptions to Permit Requirements under CWA Section 404 (last updated March 10, 2026) [11]
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  Construction and maintenance of farm or stock ponds ... Maintenance of structures such as dams, dikes, and levees ... If an activity listed above as exempt represents a new use of the water, and the activity would result in a reduction in reach or impairment of flow or circulation of regulated waters, including wetlands, the activity is not exempt. Both conditions must be met in order for the activity to be considered non-exempt. ... To find out whether specific activities are exempt, contact your local U.S. Army Corps District office or EPA regional office.

  Open U.S. Environmental Protection Agency (opens in a new tab)

Draining or drawing down a pond

RGL 05-04 tells Corps districts which sediment releases through dams need Department of the Army permits, and the "dams" it covers include barriers that create impoundments of water. It is not intended to require a permit for routine high-water-flow dam operations that let sediment-laden water flow from or through a dam, and it treats sediment released incidentally to normal dam operations (its examples include releasing water through the dam to provide irrigation or drinking water) as de minimis, generally not triggering a permit so long as it is consistent with the sediment loads entering the reservoir; deviations from normal operations that discharge bottom sediment may require a permit. In deciding whether a release is de minimis or exempt as dam maintenance, the RGL says district engineers should consider whether the discharge is necessary for dam maintenance and proportional to the activity and the size of the facility, along with factors that include the time of year, the intended release volume, the speed of the drawdown and the potential for environmental harm. [7]

The RGL says opening a dam's lower gates so that substantial quantities of sediment travel downstream is a discharge of dredged material (and possibly fill material) from a point source requiring a permit regardless of whether the operator intended to discharge sediment, and that sediment releases raising the bottom elevation of downstream waters to a discernible, substantial degree generally require permits. Section 404(f)(1) exempts discharges of dredged or fill material for maintenance of currently serviceable structures such as dikes and dams from regulation under sections 404, 301(a) and 402, except for effluent standards or prohibitions under section 307 and unless recaptured under section 404(f)(2). On that dam-maintenance exemption, the RGL says sediment released through a dam can be exempt only if it must be released for the purpose of dam maintenance, "and not for any other purpose such as maintenance of the reservoir pool," and only if the release is both necessary for essential dam maintenance and proportional to it; the Corps' regulation on the exemption says maintenance does not include any modification that changes the character, scope or size of the original fill design. In Greenfield Mills the Seventh Circuit said the discharger bears the burden of proving both that a 404(f)(1) exemption applies and that the activity is not recaptured, and read the dam-maintenance exemption to cover only dredging that is reasonably necessary to the proposed maintenance. [4][7][8][10]

For releases that need authorization, the RGL describes these routes: district engineers may, case by case, consider it an emergency, subject to the emergency permitting procedures at 33 CFR 325.2(e)(1), to lower a reservoir through one or more flood gates (with the resulting downstream discharge of dredged material) to avoid potential catastrophic dam failure; sluicing less than 25 cubic yards of material through a dam may be authorized under Nationwide Permit (NWP) 18 if all its other conditions are met; and districts may consider developing regional general permits for larger amounts of sediment. The 2026 NWP 18 (the 2026 nationwide permits took effect March 15, 2026 and expire March 15, 2031) authorizes minor discharges where the discharged material and the volume excavated do not exceed 25 cubic yards below the ordinary high water mark, the loss of waters of the United States does not exceed 1/10 acre and the material is not placed for a stream diversion, and it requires a pre-construction notification if the discharge or the excavated volume exceeds 10 cubic yards or the discharge is in a special aquatic site, including wetlands. The 2026 NWP 3 (maintenance) also authorizes removing accumulated sediment and debris within, and in the immediate vicinity of, a previously authorized, currently serviceable structure or fill being maintained. [7][14]

The RGL lists reasonable measures to reduce downstream harm, including dewatering beforehand by pumping or by releasing water from upper control structures, mechanically dredging or excavating the sediment with appropriate disposal, timing releases to coincide with high water for dilution, more frequent flushing to keep discharges small, releasing an amount of sediment that depends on the amount of water flow, and temporary barriers to keep exposed sediment from washing out in later storms. For work authorized by a 2026 nationwide permit, the general conditions require appropriate soil erosion and sediment controls, do not authorize activities that physically destroy an important spawning area (for example by downstream smothering with substantial turbidity), and encourage work during low-flow or no-flow periods; they are general conditions, not drawdown-rate standards. [7][14]

EPA's Water Transfers Rule (40 CFR 122.3(i), effective August 12, 2008) says discharges from an activity that conveys or connects waters of the United States without subjecting the water to an intervening industrial, municipal or commercial use do not require NPDES permits, except for pollutants the transfer activity itself introduces. EPA's preamble says the release through a dam described above is not a water transfer, because the water on both sides of the dam is part of the same water of the United States (it needs no NPDES permit for the separate reason given above), and that conveying water that is not a water of the United States before it is discharged is also not a "water transfer." EPA said nothing in the rule stops a state from regulating, under state law, water transfers not subject to section 402, and reported in 2008 that Pennsylvania was the only NPDES permitting authority that regularly issued NPDES permits for water transfers. [9][15]

EPA's 2022 Construction General Permit (CGP), as modified, expires at 11:59 pm on February 16, 2027. Its eligibility conditions include disturbing one or more acres (or less than one acre as part of a common plan of development or sale that will ultimately disturb one or more acres) or being designated by EPA as needing coverage, and being in an area where EPA is the permitting authority. Where a site is covered, dewatering water must be routed through a sediment control designed to prevent discharges with visual turbidity. Sites discharging dewatering water to "sensitive waters" (such as waters impaired for sediment or a sediment-related parameter) must take at least one turbidity sample each day a discharge occurs and compare the weekly average to the standard 50 NTU benchmark (or an alternate benchmark EPA has approved); EPA says the benchmark is not an effluent limitation. The permit defines dewatering as draining accumulated stormwater and/or ground water from building foundations, vaults, trenches or similar points of accumulation, with examples that include water pumped from sediment basins or similar impoundments for maintenance or decommissioning; the definition does not mention draining an existing pond or lake. EPA's proposed 2027 CGP, which is not final, would keep the same dewatering definition. [16][17][18]

• AgencyCorps Regulatory Guidance Letter 05-04 (Aug. 19, 2005), 'Guidance on the Discharge of Sediments From or Through a Dam and the Breaching of Dams', tells Corps districts which sediment releases through dams need Department of the Army permits. It does not require a permit for routine high-water-flow dam operations that let sediment-laden water pass, but deviations from normal dam operations resulting in the discharge of bottom sediment may require a DA permit. 'Dams' include barriers that create impoundments of water.

  USACE RGL 05-04 (Aug. 19, 2005), paras. 1.a-1.b [7]
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  Nothing in this guidance is intended to require a DA permit for routine high water flow dam operations that allow sediment-laden waters to flow from or through a dam; however deviations from normal dam operations resulting in the discharge of bottom sediment may require a DA permit. ... Dams, as used in this guidance include, but are not limited to, barriers that create impoundments of water.

  Open U.S. Army Corps of Engineers (opens in a new tab)

• Corps RGL 05-04 on water releases: the guidance says it is not intended to require a Department of the Army (DA) permit for routine high-water-flow dam operations that let sediment-laden water flow from or through a dam. Sediment released incidentally to normal dam operations (the RGL's examples include releasing water through the dam to provide irrigation or drinking water) is treated as de minimis and generally does not trigger a DA permit so long as it is consistent with the sediment loads entering the reservoir. Deviations from normal operations that discharge bottom sediment may require a DA permit.

  USACE RGL 05-04 (Aug. 19, 2005), paras. 1.a, 3.a [7]
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  Nothing in this guidance is intended to require a DA permit for routine high water flow dam operations ... however deviations from normal dam operations resulting in the discharge of bottom sediment may require a DA permit. ... the release of sediments that are incidental to normal dam operations (i.e., the release of water through the dam to provide irrigation water or drinking water ... are considered de minimis discharges of dredged material. ... generally do not trigger the need for a DA permit so long as they are consistent with those sediment loads entering the reservoir

  Open U.S. Army Corps of Engineers (opens in a new tab)

• RGL 05-04 sets no numeric drawdown rate or sediment amount: it states it does not propose a specific amount of sediment that is de minimis or 'more than de minimis'. In deciding whether a release is de minimis or exempt for dam maintenance, District Engineers should consider whether the discharge through the dam is necessary for dam maintenance and proportional to the proposed activity and the size of the facility, and other factors should include the time of year and normal seasonality of high-volume flows, the size of the incoming and outgoing stream/river and the intended release volume, the natural hydrograph, the speed of the drawdown, the normal amount of sediment in the watershed, and the potential for environmental harm.

  USACE RGL 05-04 (Aug. 19, 2005), para. 4.b [7]
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  does not propose to set a specific amount of sediment ... District Engineers should consider whether the discharge ... is necessary for dam maintenance, and proportional to the proposed activity and the size of the facility ... Other factors in this consideration should include the time of year and normal seasonality of high volume flows, the size of incoming and outgoing stream/river and the intended release volume, the natural hydrograph of the system, the speed of the drawdown, the normal amount of sediment in the watershed, and the potential for environmental harm.

  Open U.S. Army Corps of Engineers (opens in a new tab)

• RequirementRGL 05-04: opening a dam's lower gates so that substantial sediment travels downstream is a discharge of dredged material (and possibly fill) from a point source requiring a DA permit regardless of whether the operator intended to discharge sediment; and sediment releases that raise the bottom elevation of downstream waters to a discernible, substantial degree generally require permits as discharges of fill material.

  USACE RGL 05-04 (Aug. 19, 2005), paras. 2.e, 3.c [7]
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  DA permits are generally required for the discharge of sediments from dams when such activities would have the effect of raising the bottom elevation of the downstream waters to a discernible, substantial degree. ... Regardless of whether the dam operators had the intent to discharge sediment through the dam ... the opening of the lower gates of the dam has the effect of allowing substantial quantities of sediment material to travel downstream, thereby constituting the discharge of dredged material (and possibly fill material, as well) from a point source, thereby requiring a DA permit.

  Open U.S. Army Corps of Engineers (opens in a new tab)

• RequirementRGL 05-04 on the 404(f) dam-maintenance exemption: sediment released through a dam can be exempt only if it must be released for the purpose of dam maintenance - 'and not for any other purpose such as maintenance of the reservoir pool' - and the release must be both necessary for essential dam maintenance and proportional to it.

  USACE RGL 05-04 (Aug. 19, 2005), para. 3.b [7]
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  Consequently, the discharge of sediments through a dam cannot be exempted from CWA regulation under Subsection 404(f)(1) unless those sediments must be released for the purpose of dam maintenance, and not for any other purpose such as maintenance of the reservoir pool. ... such discharges of sediments through a dam would have to be both necessary to allow essential dam maintenance to occur, and would have to be proportional to the dam maintenance activities that necessitate the release of sediments.

  Open U.S. Army Corps of Engineers (opens in a new tab)

• ExemptionCorps regulation on the dam-maintenance exemption: maintenance (including emergency reconstruction of recently damaged parts) of currently serviceable structures such as dikes and dams does not include any modification that changes the character, scope, or size of the original fill design, and emergency reconstruction must occur within a reasonable period of time after the damage to qualify.

  33 CFR 323.4(a)(2) [4]
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  Maintenance, including emergency reconstruction of recently damaged parts, of currently serviceable structures such as dikes, dams, levees, groins, riprap, breakwaters, causeways, bridge abutments or approaches, and transportation structures. Maintenance does not include any modification that changes the character, scope, or size of the original fill design. Emergency reconstruction must occur within a reasonable period of time after damage occurs in order to qualify for this exemption.

  Open eCFR (Office of the Federal Register) (opens in a new tab)

• ProcessRGL 05-04 authorization routes: on a case-by-case basis, District Engineers may consider lowering a reservoir through one or more flood gates (and the resulting downstream discharge of dredged material) to avoid potential catastrophic dam failure to be an emergency subject to the emergency permitting procedures at 33 CFR 325.2(e)(1); sluicing less than 25 cubic yards of material through a dam may be authorized under Nationwide Permit 18 if all other conditions of that NWP are met; and districts may consider developing Regional General Permits for larger amounts of sediment.

  USACE RGL 05-04 (Aug. 19, 2005), para. 4.c [7]
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  On a case-by case basis, District Engineers may consider the need to reduce the level of the reservoir through one or more flood gates and the resultant discharge of dredged material downstream, to ... avoid potential catastrophic dam failure, to be an emergency subject to the emergency permitting procedures found at 33 CFR 325.2(e)(1). Sluicing through a dam of less than 25 cubic yards of material may be authorized under Nationwide Permit 18, if all other conditions of that nationwide permit are met. Districts may also consider developing Regional General Permits

  Open U.S. Army Corps of Engineers (opens in a new tab)

• Size cutoffCurrent Nationwide Permit 18 (Minor Discharges), 2026 NWPs: authorizes minor discharges of dredged or fill material into all waters of the United States if the discharged material and the volume excavated do not exceed 25 cubic yards below the ordinary high water mark, the loss of waters of the United States does not exceed 1/10 acre, and the material is not placed for stream diversion; a pre-construction notification is required if the discharge or excavation exceeds 10 cubic yards or is in a special aquatic site including wetlands.

  NWP 18 (2026), 91 FR 768, 862 (Jan. 8, 2026); DATES [14]
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  Minor discharges of dredged or fill material into all waters of the United States, provided ... (a) The quantity of discharged dredged or fill material and the volume of area excavated do not exceed 25 cubic yards below the plane of the ordinary high water mark ... will not cause the loss of more than \1/10\-acre of waters of the United States; and (c) ... not placed for the purpose of a stream diversion. ... or the volume of area excavated exceeds 10 cubic yards ... or (2) the discharge of dredged or fill material is in a special aquatic site, including wetlands.

  Open Federal Register / U.S. Army Corps of Engineers (opens in a new tab)

• ProcessCurrent Nationwide Permit 3 (Maintenance), 2026: paragraph (a) also authorizes removal of accumulated sediment and debris within, and in the immediate vicinity of, the previously authorized, currently serviceable structure or fill being maintained. Paragraph (b) authorizes removal of accumulated sediments and debris outside the immediate vicinity of existing structures (the NWP's examples are bridges, culverted road crossings and water intake structures), limited to the minimum necessary to restore the waterway near the structure to its approximate as-built dimensions and no farther than 200 feet in any direction from the structure (the 200-foot limit does not apply to maintenance dredging of accumulated sediments blocking or restricting outfall and intake structures, or canals associated with them); dredged or excavated material must be deposited and retained in an area with no waters of the United States unless the district engineer specifically approves otherwise under separate authorization. Paragraph (b) work requires a pre-construction notification to the district engineer, which must include the original design capacities and configurations of the outfalls, intakes, small impoundments, and canals.

  NWP 3 (2026), 91 FR 768, 858-859 (Jan. 8, 2026) [14]
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  sediment and debris within, and in the immediate vicinity of, the structure or fill. ... removal of accumulated sediments and debris outside the immediate vicinity of existing structures (e.g., bridges, culverted road crossings, water intake structures, etc.). ... cannot extend farther than 200 feet in any direction from the structure. This 200 foot limit does not apply to maintenance dredging to remove accumulated sediments blocking or restricting outfall and intake structures ... unless otherwise specifically approved by the district engineer ... small impoundments, and canals.

  Open Federal Register / U.S. Army Corps of Engineers (opens in a new tab)

• RequirementRGL 05-04 reasonable measures to reduce downstream harm when discharging sediment from or through a dam include prior dewatering by pumping or releasing water from the upper control structures; mechanical dredging or excavation of sediment with appropriate disposal; timing releases to coincide with high water for dilution; more frequent flushing to keep discharges small; releasing sediment in proportion to water flow; and temporary barriers to keep exposed sediments from washing out in later storms.

  USACE RGL 05-04 (Aug. 19, 2005), para. 4.d [7]
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  Reasonable measures include, but are not limited to, prior dewatering by pumping or by releasing water from the upper control structures on a reservoir; mechanical dredging or excavation of sediments and appropriate disposal; timing releases to coincide with high water periods for better dilution; more frequent flushing to keep the discharges small; releasing a sediment amount that is dependent on the amount of water flow; and installing temporary barriers to prevent exposed sediments from being transported by runoff from subsequent storm events.

  Open U.S. Army Corps of Engineers (opens in a new tab)

• ExemptionNPDES exclusion for water transfers: discharges from a 'water transfer' do not require NPDES permits. 'Water transfer' means an activity that conveys or connects waters of the United States without subjecting the transferred water to intervening industrial, municipal, or commercial use. Limit: the exclusion does not apply to pollutants introduced by the water transfer activity itself to the water being transferred. The eCFR amendment history for section 122.3 lists 73 FR 33708 (June 13, 2008), the Water Transfers Rule, which added paragraph (i).

  40 CFR 122.3(i) [15]
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  The following discharges do not require NPDES permits: ... (i) Discharges from a water transfer. Water transfer means an activity that conveys or connects waters of the United States without subjecting the transferred water to intervening industrial, municipal, or commercial use. This exclusion does not apply to pollutants introduced by the water transfer activity itself to the water being transferred. ... 73 FR 33708, June 13, 2008

  Open eCFR (opens in a new tab)

• EPA's 2008 preamble dam example: releasing water from Reservoir A through a dam into River A is not a 'water transfer' because the water on both sides of the dam is part of the same water of the U.S. EPA adds (footnote 3) that the release would still not require an NPDES permit, because EPA and the federal courts have determined that a discharge from a dam does not result in an 'addition' of a pollutant unless the dam itself discharges a pollutant, such as grease, into the water passing through it (citing Gorsuch and Consumers Power). EPA also noted that CWA section 401 certification may be needed in some instances (citing S.D. Warren v. Maine Board of Environmental Protection).

  Applies when: Releasing water through a dam or outlet of an impoundment that is a water of the United States 73 FR 33697, 33699-33700 & n.3 (June 13, 2008) [9]
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  The first example is the release from Reservoir A to River A. This does not constitute a water transfer under EPA's definition because the water on both sides of the dam is part of the same water of the U.S. ... this release would still not require an NPDES permit because EPA and the Federal courts have determined that a discharge from a dam does not result in an ``addition'' of a pollutant unless the dam itself discharges a pollutant such as grease ... (Certification under CWA section 401 may be needed in some instances).

  Open U.S. EPA / Federal Register (govinfo) (opens in a new tab)

• DefinitionEPA's 2008 preamble: to be a 'water transfer' (and so be exempt from NPDES), the water being conveyed must be a water of the U.S. before it is discharged to the receiving waterbody; if the conveyed water is not a water of the U.S. before discharge, the activity is not a water transfer under the rule. The water must also be conveyed from one water of the U.S. to another; conveyances within the same water of the U.S. are not water transfers, although EPA says movements of water within a single water body are also not subject to NPDES permitting.

  Applies when: Draining or pumping a pond into another water 73 FR 33697, 33699 (June 13, 2008), preamble sec. II [9]
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  If the water that is being conveyed is not a water of the U.S. prior to being discharged to the receiving body, then that activity does not constitute a water transfer under today's rule. Additionally, the water must be conveyed from one water of the U.S. to another water of the U.S. Conveyances that remain within the same water of the U.S., therefore, do not constitute water transfers under this rule, although movements of water within a single water body are also not subject to NPDES permitting requirements.

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• RequirementCGP Part 2.4 construction dewatering requirements include: route dewatering water through a sediment control (e.g., sediment trap or basin, pumped water filter bag) designed to prevent discharges with visual turbidity (a sediment plume, or a cloudy, opaque or visibly contrasting discharge); do not discharge visible floating solids or foam; to the extent feasible, infiltrate dewatering water in well-vegetated upland areas before discharge; and do not use receiving waters as part of the treatment area.

  Applies when: Dewatering discharges authorized under the EPA CGP EPA 2022 CGP (as modified), Part 2.4.1-2.4.4 and n.56 [16]
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  Route dewatering water through a sediment control (e.g., sediment trap or basin, pumped water filter bag) designed to prevent discharges with visual turbidity; ... Do not discharge visible floating solids or foam; ... visual turbidity is present where there is a sediment plume in the discharge or the discharge appears cloudy, or opaque, or has a visible contrast ... use well-vegetated (e.g., grassy or wooded), upland areas of the site to infiltrate dewatering water before discharge. ... You are prohibited from using receiving waters as part of the treatment area;

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• Size cutoffCGP turbidity benchmark for dewatering: sites discharging dewatering water to 'sensitive waters' (waters impaired for sediment or a sediment-related parameter, Tier 2, 2.5 or 3 antidegradation waters, or waters within Lands of Exclusive Federal Jurisdiction) must collect at least one turbidity sample from the dewatering discharge each day a discharge occurs and compare the weekly average of the results to the standard 50 NTU benchmark (or to an alternate benchmark if EPA has approved one). EPA states the benchmark is not an effluent limitation. Separately, sites discharging dewatering water must be inspected during the discharge once per day on which the discharge occurs.

  Applies when: CGP dewatering discharges; benchmark only for discharges to sensitive waters EPA 2022 CGP (as modified), Parts 3.3, 3.3.1, 3.3.2, 3.3.3, 4.3.2 [16]
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  For sites discharging dewatering water to “sensitive waters” (i.e., receiving waters listed as impaired for sediment or a sediment-related parameter ... EPA notes that the benchmark threshold is not an effluent limitation ... at least one turbidity sample from your dewatering discharge each day a discharge occurs. ... unless EPA has authorized the use of an alternate benchmark ... Compare the weekly average ... of your turbidity monitoring results to the standard 50 NTU benchmark ... you must conduct an inspection ... during the discharge once per day on which the discharge occurs.

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Does sealing or lining need a federal permit?

The Corps and EPA define "fill material" by its effect: material placed in waters of the United States that replaces any portion of a water with dry land or changes the bottom elevation of any portion of a water, with non-exclusive examples that include rock, sand, soil, clay and plastics; the Corps' rule also says trash or garbage is not fill material. The Corps' definition of "discharge of fill material" includes building any structure, infrastructure or impoundment requiring rock, sand, dirt or other material for its construction, and its only reference to a liner is placing fill for a liner associated with solid waste landfills; whether sealing or lining a pond is a section 404 discharge is listed below as not confirmed. [4][26]

In the May 2002 joint rule that adopted this "fill material" definition, the agencies said placing berms, liners and other infrastructure for a solid waste landfill in waters of the United States replaces water with dry land or raises the bottom elevation, so under that rule those liners are fill material. The same preamble says the agencies do not consider suspended or settleable solids, which can raise a water's bottom over time as they settle, to be "fill material," and the Supreme Court held in Coeur Alaska (2009) that EPA may not issue section 402 permits for fill material that falls under the Corps' section 404 authority. [27][28]

Corps regulations say discharges of dredged or fill material from construction or maintenance of farm or stock ponds are not subject to section 404 regulation, but a section 404 permit is still required if the discharge contains a toxic pollutant listed under section 307, or if it is part of an activity whose purpose is to convert an area of waters of the United States to a use to which it was not previously subject, where flow or circulation may be impaired or reach reduced. On bottom elevation, the recapture regulation says a discharge that raises the bottom of waters of the United States without converting it to dry land "does not thereby reduce the reach of, but may alter the flow or circulation of," those waters; whether sealing or relining counts as exempt pond maintenance is listed below as not confirmed. [4]

Among the 2026 nationwide permits (effective March 15, 2026, expiring March 15, 2031), NWP 3 authorizes the repair, rehabilitation or replacement of a previously authorized, currently serviceable structure or fill, provided it is not put to uses differing from those specified or contemplated in the original permit or the most recently authorized modification, and its note says it authorizes such work on structures or fills that do not qualify for the section 404(f) maintenance exemption. NWP 18 authorizes minor discharges within its 25-cubic-yard and 1/10-acre limits (its conditions and notification triggers are described under draining, above). For nationwide permit limits, "loss of waters of the United States" counts waters permanently adversely affected by the regulated activity, including by permanent discharges of dredged or fill material that increase the bottom elevation of a waterbody, but not waters temporarily filled, flooded, excavated or drained and then restored to pre-construction contours and elevations. Whether a Corps district would authorize sealing or lining under either permit is listed below as not confirmed. [14]

The 2023 rule's preamble, explaining the term "dry land" used in the rule's exclusions, says jurisdictional and non-jurisdictional waters are not considered "dry land" just because they lack water at a given time, and a Corps regulatory note says unauthorized discharges do not eliminate Clean Water Act jurisdiction, even where they have the effect of destroying waters of the United States. How these apply to a pond drained for sealing is listed below as not confirmed. [4][6]

For products added to pond water: FIFRA bars distributing or selling an unregistered pesticide except as the Act provides. EPA's rules consider a product a pesticide requiring registration (subject to listed exceptions) if the seller claims, states or implies that it can or should be used as a pesticide, if it contains active ingredients and has no significant commercially valuable use other than pesticidal use or use to manufacture a pesticide, or if the seller has actual or constructive knowledge that it will be used, or is intended to be used, for a pesticidal purpose. EPA's rules treat algae and other plants growing where not wanted as pests when circumstances make them deleterious to man or the environment, and EPA says point-source discharges to waters of the United States from applying biological pesticides, or chemical pesticides that leave a residue, have required NPDES permits since October 31, 2011. [29][30][31]

• DefinitionUnder the Corps' section 404 regulations, 'fill material' is material placed in waters of the United States that has the effect of (i) replacing any portion of a water of the United States with dry land, or (ii) changing the bottom elevation of any portion of a water of the United States. The regulation's non-exclusive examples include rock, sand, soil, clay, plastics, construction debris, wood chips, overburden from mining or other excavation, and materials used to create any structure. The term does not include trash or garbage.

  Applies when: Only where the pond (or the area worked in) is a 'water of the United States'. 33 CFR 323.2(e)(1)-(3) [4]
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  the term fill material means material placed in waters of the United States where the material has the effect of: (i) Replacing any portion of a water of the United States with dry land; or (ii) Changing the bottom elevation of any portion of a water of the United States. (2) Examples of such fill material include, but are not limited to: rock, sand, soil, clay, plastics, construction debris, wood chips, overburden from mining or other excavation activities, and materials used to create any structure ... (3) The term fill material does not include trash or garbage.

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• DefinitionThe Corps defines 'discharge of fill material' as the addition of fill material into waters of the United States. Its listed examples include placement of fill necessary to construct any structure or infrastructure in a water of the United States; building any structure, infrastructure, or impoundment requiring rock, sand, dirt, or other material for its construction; and 'placement of fill material for construction or maintenance of any liner, berm, or other infrastructure associated with solid waste landfills' (the only reference to a liner in the definition). The term does not include plowing, cultivating, seeding and harvesting (for the production of food, fiber, and forest products, per the full text).

  Applies when: Only where the pond (or the area worked in) is a 'water of the United States'. 33 CFR 323.2(f) [4]
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  The term discharge of fill material means the addition of fill material into waters of the United States. ... Placement of fill that is necessary for the construction of any structure or infrastructure in a water of the United States; the building of any structure, infrastructure, or impoundment requiring rock, sand, dirt, or other material for its construction; ... placement of fill material for construction or maintenance of any liner, berm, or other infrastructure associated with solid waste landfills; ... The term does not include plowing, cultivating, seeding and harvesting

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• The 2002 preamble describes a court decision (Resource Investments v. Corps, 9th Cir. 1998) finding that neither solid waste nor a landfill liner of layers of gravel and low-permeability soil was 'fill material' under the Corps' then-current regulations. The agencies responded that fills typically serve some purpose other than just creating dry land or raising a water's bottom elevation, and stated that placing berms, liners and other infrastructure for a solid waste landfill in waters of the U.S. has the effect of replacing water with dry land or raising the bottom elevation of a water, so under the 2002 rule they constitute fill material.

  67 FR 31129, 31136-31137 (May 9, 2002), preamble sec. D ('The Final Rule and the Resource Investments Decision') [27]
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  Neither the solid waste itself nor the liner consisting of layers of gravel and low-permeability soil constituted ``fill material'' under Corps regulations ... fills typically serve some other purpose than just creating dry land or raising a water's bottom elevation ... The placement of berms, liners and other infrastructure (such as roads) associated with construction of a solid waste landfill in waters of the U.S. has the effect of replacing water with dry land or raising the bottom elevation of a water. Therefore, under today's rule, they constitute fill material.

  Open U.S. Army Corps of Engineers and U.S. EPA / Federal Register (govinfo) (opens in a new tab)

• The 2002 fill-rule preamble states that the rule generally is intended to maintain the agencies' existing approach to regulating pollutants under either section 402 or section 404; that, recognizing that some discharges (such as suspended or settleable solids) can have the associated effect, over time, of raising the bottom elevation of a water due to settling of waterborne pollutants, the agencies do not consider such pollutants to be 'fill material'; and that discharges subject to an effluent limitation guideline and standards will continue to be regulated under section 402.

  67 FR 31129, 31135 (May 9, 2002), preamble sec. 'Effluent Guideline Limitations and 402 Permits' [27]
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  today's rule generally is intended to maintain our existing approach to regulating pollutants under either section 402 or 404 of the CWA. ... Recognizing that some discharges (such as suspended or settleable solids) can have the associated effect, over time, of raising the bottom elevation of a water due to settling of waterborne pollutants, we do not consider such pollutants to be ``fill material,'' ... discharges that are subject to an effluent limitation guideline and standards, which will continue to be regulated under section 402 of the CWA.

  Open U.S. Army Corps of Engineers and U.S. EPA / Federal Register (govinfo) (opens in a new tab)

• ExemptionThe Corps' regulation lists 'construction or maintenance of farm or stock ponds or irrigation ditches, or the maintenance (but not construction) of drainage ditches' among discharges not requiring a section 404 permit, subject to the toxic-pollutant and recapture exceptions in 33 CFR 323.4(b) and (c).

  33 CFR 323.4(a)(3) [4]
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  (a) General. Except as specified in paragraphs (b) and (c) of this section, any discharge of dredged or fill material that may result from any of the following activities is not prohibited by or otherwise subject to regulation under section 404: ... (3) Construction or maintenance of farm or stock ponds or irrigation ditches, or the maintenance (but not construction) of drainage ditches.

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• RequirementEven for an otherwise exempt activity (such as farm or stock pond construction or maintenance), if the discharge of dredged or fill material contains any toxic pollutant listed under CWA section 307, the discharge is subject to any applicable toxic effluent standard or prohibition and requires a section 404 permit.

  33 CFR 323.4(b); see also 40 CFR 232.3(a) [4]
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  (b) If any discharge of dredged or fill material resulting from the activities listed in paragraphs (a) (1) through (6) of this section contains any toxic pollutant listed under section 307 of the CWA such discharge shall be subject to any applicable toxic effluent standard or prohibition, and shall require a section 404 permit.

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• RequirementThe Corps' recapture regulation requires a permit for an otherwise exempt discharge that is part of an activity whose purpose is to convert an area of waters of the United States to a use to which it was not previously subject, where flow or circulation may be impaired or reach reduced; where a discharge will result in significant discernible alterations to flow or circulation, flow or circulation is presumed to be impaired. On bottom elevation, the regulation says a discharge that elevates the bottom of waters of the United States without converting it to dry land 'does not thereby reduce the reach of, but may alter the flow or circulation of,' those waters.

  33 CFR 323.4(c) [4]
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  must have a permit if it is part of an activity whose purpose is to convert an area of the waters of the United States into a use to which it was not previously subject, where the flow or circulation ... may be impaired or the reach of such waters reduced. ... significant discernible alterations to flow or circulation, the presumption is that flow or circulation may be impaired by such alteration. ... A discharge which elevates the bottom of waters of the United States without converting it to dry land does not thereby reduce the reach of, but may alter the flow or circulation of,

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• ProcessNWP 3 (Maintenance, 2026) paragraph (a) authorizes the repair, rehabilitation, or replacement of any previously authorized, currently serviceable structure or fill, provided it is not put to uses differing from those specified or contemplated in the original permit (or the most recently authorized modification, per the full text); minor deviations in the structure's configuration or filled area, including those due to changes in materials, that are necessary to make the repair, rehabilitation, or replacement are authorized. A Note states that NWP 3 authorizes repair, rehabilitation, or replacement of any previously authorized structure or fill that does not qualify for the section 404(f) maintenance exemption.

  Applies when: Structures or fills previously authorized by the Corps (or authorized by 33 CFR 330.3) in waters of the United States. NWP 3(a), Notification and Note, 91 FR 768, 858-859 (Jan. 8, 2026) [14]
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  any previously authorized, currently serviceable structure or fill ... not to be put to uses differing from those uses specified or contemplated for it in the original permit ... Minor deviations in the structure's configuration or filled area, including those due to changes in materials ... that are necessary to make the repair, rehabilitation, or replacement are authorized. ... authorizes the repair, rehabilitation, or replacement of any previously authorized structure or fill that does not qualify for the Clean Water Act Section 404(f) exemption for maintenance.

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• DefinitionFor NWP thresholds, 'loss of waters of the United States' means waters permanently adversely affected by filling, flooding, excavation, or drainage because of the regulated activity; permanent adverse effects include permanent discharges of dredged or fill material that change an aquatic area to dry land, increase the bottom elevation of a waterbody, or change the use of a waterbody. Waters temporarily filled, flooded, excavated, or drained but restored to pre-construction contours and elevations after construction are not counted.

  2026 NWP Definitions, 'Loss of waters of the United States', 91 FR 768, 884 (Jan. 8, 2026) [14]
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  Waters of the United States that are permanently adversely affected by filling, flooding, excavation, or drainage because of the regulated activity. ... Permanent adverse effects include permanent discharges of dredged or fill material that change an aquatic area to dry land, increase the bottom elevation of a waterbody, or change the use of a waterbody. ... Waters of the United States temporarily filled, flooded, excavated, or drained, but restored to pre-construction contours and elevations after construction, are not included in the measurement of loss

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• RequirementEPA's rule on which products must be registered (40 CFR 152.15), whose registration requirement is subject to 40 CFR 152.20, 152.25 and 152.30: a substance is considered intended for a pesticidal purpose, and thus a pesticide requiring registration, if (a) the person who distributes or sells it claims, states, or implies (by labeling or otherwise) that it can or should be used as a pesticide (or, per the full text, that it contains an active ingredient that can be used to manufacture a pesticide); (b) it consists of or contains one or more active ingredients and has no significant commercially valuable use as distributed or sold other than pesticidal use or use to manufacture a pesticide (per the full text); or (c) the person who distributes or sells it has actual or constructive knowledge that it will be used, or is intended to be used, for a pesticidal purpose.

  40 CFR 152.15 [30]
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  except as provided in §§ 152.20, 152.25, and 152.30. ... to be a pesticide requiring registration, if: (a) The person who distributes or sells the substance claims, states, or implies (by labeling or otherwise): (1) That the substance ... can or should be used as a pesticide; ... (b) The substance consists of or contains one or more active ingredients and has no significant commercially valuable use as distributed or sold other than ... (c) ... has actual or constructive knowledge that the substance will be used, or is intended to be used, for a pesticidal purpose.

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• DefinitionEPA's rules declare an organism to be a pest, under circumstances that make it deleterious to man or the environment, if it is any vertebrate animal other than man; any invertebrate animal such as an insect, other arthropod, nematode, or mollusk such as a slug and snail (excluding internal parasites of living man or other living animals); or any plant growing where not wanted, including any moss, alga, liverwort, or other plant of any higher order. Under that rule, algae and other plants growing where not wanted are pests when the circumstances make them deleterious to man or the environment.

  40 CFR 152.5 [30]
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  An organism is declared to be a pest under circumstances that make it deleterious to man or the environment, if it is: (a) Any vertebrate animal other than man; (b) Any invertebrate animal, including but not limited to, any insect, other arthropod, nematode, or mollusk such as a slug and snail, but excluding any internal parasite of living man or other living animals; (c) Any plant growing where not wanted, including any moss, alga, liverwort, or other plant of any higher order, and any plant part such as a root;

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• RequirementEPA states that, as a result of a Sixth Circuit decision, point source discharges to waters of the United States from pesticide applications have required NPDES permits since October 31, 2011; permits are required for any point source discharge to waters of the United States from the application of (1) biological pesticides and (2) chemical pesticides that leave a residue, and the CWA gives EPA no authority to exclude small 'de minimis' or short-term discharges.

  Applies when: Only if the product applied is a pesticide (for example, a product with algae- or weed-control claims) and the pond is a water of the United States. EPA, Pesticide Permitting - Frequent Questions (last updated March 31, 2026) [31]
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  As a result of the Sixth Circuit’s decision, point source discharges to waters of the United States from the application of pesticides require NPDES permits as of October 31, 2011. ... permits are required for any point source discharge to waters of the United States from the application of (1) biological pesticides and (2) chemical pesticides that leave a residue. ... The Clean Water Act (CWA) does not provide EPA with the authority to exclude certain types of discharges from the need to obtain permit coverage, such as small “de minimus” or short-term discharges,

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NRCS pond sealing and lining standards (CPS 520, 521, 522)

As retrieved September 28, 2026, NRCS's national practice standards index lists three pond sealing or lining standards with these version dates: Pond Sealing or Lining, Compacted Soil Treatment (Code 520), 05/2016; Pond Sealing or Lining, Concrete (Code 522), 05/2016; and Pond Sealing or Lining, Geomembrane or Geosynthetic Clay Liner (Code 521), 08/2023. [12]

The current CPS 520 (May 2016) defines Compacted Soil Treatment as a liner for an impoundment built of compacted soil with or without soil amendments to reduce seepage losses, and applies where in-place natural soils have excessive seepage rates and an adequate quantity and type of soil is available either for a compacted soil liner without amendments or for an amended liner treated with a soil dispersant or bentonite. The finished compacted liner must be at least the greatest of the thickness needed to meet a specific-discharge design value, a thickness required by state regulations, or the Table 1 minimum: 12 inches for a design storage depth of 16 feet or less, 18 inches for 16.1-24 feet and 24 inches for 24.1-30 feet. Side slopes should be 3H:1V or flatter when the "bathtub" construction method is used, and slopes as steep as 2H:1V can be considered with the "stair-step" method. [35]

CPS 520 requires bentonite to be sodium bentonite with a free swell of at least 22 milliliters measured by ASTM D5890, unless laboratory tests using other bentonite types are used for design. For clean water ponds without laboratory tests or field performance data on similar soils, the minimum bentonite rates per 1-inch lift are 0.375 lb/sq ft for silts (ML, CL-ML), 0.5 lb/sq ft for silty sands (SM, SC-SM, SP-SM) and 0.625 lb/sq ft for clean sand (SP, SW), installed in lifts no thicker than 6 inches; the minimum soil dispersant rates per 6-inch lift are 7.5 lbs per 100 sq ft for polyphosphate (TSPP, STPP) and 15 lbs per 100 sq ft for soda ash. A clean water pond liner is to be designed to reduce seepage to a rate that will allow the pond to function as intended, while a waste storage impoundment liner must meet specific discharge rates and requires laboratory testing. [35]

CPS 521 (August 2023 revision) covers geomembrane or geosynthetic clay liners where in-place natural soils have excessive seepage rates and lining or sealing is needed for water conservation or to protect surface or groundwater from contamination; its Table 1 lists minimum clear-water thicknesses including 30 mil for HDPE, LLDPE and PVC and 45 mil for EPDM, and 0.75 lbs./square foot for a geosynthetic clay liner. It requires PVC liners and geosynthetic clay liners to be covered with at least 12 inches of soil placed within 24 hours after liner placement and anchorage, and its considerations say PVC geomembranes are not recommended for aquatic production because stabilizers in the liner material leach out and may be harmful to aquatic species. CPS 522 (May 2016) covers liners of reinforced or nonreinforced concrete and requires the designer to select either "reduced seepage" or "liquid tight" criteria. [36][37]

PROPOSED, not final: on September 1, 2026 NRCS published a notice of availability and request for comments (91 FR 56102, Docket NRCS-2026-0100) on proposed revisions to 48 conservation practice standards, including 520 and 522, and will consider comments received by October 1, 2026. The notice says NRCS State Conservationists who choose to adopt these standards in their states will incorporate them into their state's electronic Field Office Technical Guide. [13]

The notice describes the proposed 520 changes as no major technical revisions; clarifications and readability edits; two added purposes; new criteria on compliance with applicable laws, safety and existing impoundment requirements; and a reduced minimum liner thickness for clean-water storage impoundments. The proposed September 2026 draft of 520 would keep the Table 1 minimum liner thicknesses by depth "unless the impoundment is for water storage where the minimum thickness is 12 inches at all depths," would keep the 22-milliliter bentonite specification and the same clean-water-pond rates with a 6-inch maximum lift, and would state that "The landowner or operator is responsible for obtaining all necessary permits and approvals prior to, during, and after construction of the facility." For 522, the notice says the only major technical revision is the addition of leak-detection requirements for installations in high-permeability soils. [13][38]

• StatusNRCS's national Conservation Practice Standards index lists three pond sealing/lining standards with these current version dates: Pond Sealing or Lining, Compacted Soil Treatment (Code 520), unit square feet, dated 05/2016; Pond Sealing or Lining, Concrete (Code 522), dated 05/2016; and Pond Sealing or Lining, Geomembrane or Geosynthetic Clay Liner (Code 521), dated 08/2023.

  NRCS, Conservation Practice Standards index (National Handbook of Conservation Practices) [12]
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  Pond Sealing or Lining, Compacted Soil Treatment (Sq.Ft). (520) 05/2016 Pond Sealing or Lining, Concrete (Sq.Ft) (522) 05/2016 Pond Sealing or Lining, Geomembrane or Geosynthetic Clay Liner (Sq.Ft.) (521) 08/2023

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• DefinitionNRCS CPS 520 (national, May 2016) defines Pond Sealing or Lining - Compacted Soil Treatment as a liner for an impoundment constructed using compacted soil with or without soil amendments, installed to reduce seepage losses from impoundments constructed for water conservation and environmental protection.

  NRCS CPS Pond Sealing or Lining - Compacted Soil Treatment (Code 520), NHCP May 2016, Definition and Purpose, p. 520-CPS-1 [35]
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  DEFINITION A liner for an impoundment constructed using compacted soil with or without soil amendments. PURPOSE This practice is installed to reduce seepage losses from impoundments constructed for water conservation and environmental protection.

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• RequirementCPS 520 applies where in-place natural soils have excessive seepage rates AND either (a) an adequate quantity and type of soil suitable for a compacted soil liner without amendments is available, or (b) an adequate quantity and type of soil suitable for treatment with a soil dispersant or bentonite amendment is available for an amended soil liner.

  NRCS CPS 520 (May 2016), Conditions Where Practice Applies, p. 520-CPS-1 [35]
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  This practice applies where— • In-place natural soils have excessive seepage rates, and • An adequate quantity and type of soil suitable for constructing a compacted soil liner without amendments is available, or • An adequate quantity and type of soil suitable for treatment with a soil dispersant or bentonite amendment is available for an amended soil liner.

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• Size cutoffCPS 520 minimum finished compacted liner thickness is the greatest of: the thickness needed to achieve a specific-discharge design value, a thickness required by State regulations, or the Table 1 minimum by design storage depth - 12 inches for depths of 16 ft or less, 18 inches for 16.1-24 ft, and 24 inches for 24.1-30 ft.

  NRCS CPS 520 (May 2016), Criteria - Liner Thickness and Table 1, pp. 520-CPS-1 to -2 [35]
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  Liner Thickness. The minimum thickness of the finished compacted liner must be the greater of— • The liner thickness required to achieve a specific discharge (unit seepage) design value, or ... A liner thickness required by State regulations, or • The minimum liner thickness as shown in table 1. Table 1. Minimum liner thickness by design storage depth. Design Storage Liner Thickness Depth (ft) (in) ≤16 12 16.1–24 18 24.1–30 24

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• RequirementCPS 520 bentonite material specification: bentonite must be sodium bentonite with a free swell of at least 22 milliliters measured by ASTM D5890, unless laboratory tests using other bentonite types are used for design. For waste storage impoundments, laboratory permeability tests using bentonite of the same quality and fineness as proposed are required.

  NRCS CPS 520 (May 2016), Additional Criteria for Bentonite Treatment - Bentonite Material; Application Rate, p. 520-CPS-3 [35]
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  Bentonite Material. The bentonite must be a sodium bentonite with a free swell of at least 22 milliliters as measured by ASTM Standard Test Method D5890, unless laboratory tests using other bentonite types are used for design. Application Rate. For waste storage impoundments, conduct laboratory permeability tests using bentonite of the same quality and fineness as that proposed for use.

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• Size cutoffCPS 520 minimum bentonite application rates for clean water ponds (used when there are no laboratory tests or field performance data on similar soils), in lbs per sq ft per 1-inch lift thickness: silts (ML, CL-ML) 0.375; silty sands (SM, SC-SM, SP-SM) 0.5; clean sand (SP, SW) 0.625. The liner is installed with a maximum 6-inch lift thickness.

  Applies when: Clean water ponds, absent laboratory tests or field performance data NRCS CPS 520 (May 2016), Additional Criteria for Bentonite Treatment - Application Rate, Table 3, p. 520-CPS-3 [35]
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  For clean water ponds, in the absence of laboratory tests or field performance data on soils similar to those to be treated, apply the bentonite at a rate equal to or greater to the amount listed in table 3. Install the liner with a maximum of 6-inch-lift thickness. Table 3. Minimum Bentonite Application Rates for Clean Water Ponds. ... Silts (ML, CL-ML) 0.375 Silty Sands (SM, SC- 0.5 SM, SP-SM) Clean Sand (SP, SW) 0.625

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• DefinitionNRCS CPS 521 (national, August 2023 revision) defines Pond Sealing or Lining, Geomembrane or Geosynthetic Clay Liner as a liner for a water, wastewater, salt, manure, or similar agricultural by-product impoundment constructed using a geomembrane or geosynthetic clay material. It applies where in-place natural soils have excessive seepage rates and lining or sealing is needed for water conservation or to protect surface or groundwater from contamination.

  NRCS CPS Pond Sealing or Lining, Geomembrane or Geosynthetic Clay Liner (Code 521), NHCP August 2023R, Definition; Conditions Where Practice Applies, p. 521-CPS-1 [36]
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  A liner for a water, wastewater, salt, manure, or similar agricultural by-product impoundment constructed using a geomembrane or a geosynthetic clay material. ... This practice applies where in-place natural soils have excessive seepage rates and pond lining or sealing is needed for water conservation or to protect surface or groundwater from contamination.

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• Size cutoffCPS 521 requires geomembrane and GCL materials to meet Table 1, which lists these minimum thicknesses in mil for clear water (wastewater value in parentheses): HDPE 30 (60); LLDPE 30 (60); LLDPE-R 24 (45); PVC 30 (40); EPDM 45 (45); FPP 30 (45); FPP-R 36 (45, marked with footnote 3, 'NR - Not recommended for waste storage'); PE-R 36 (NR - not recommended for waste storage). For a geosynthetic clay liner (GCL) the table lists 0.75 lbs./square foot. 1 mil = 1/1000 inch.

  NRCS CPS 521 (August 2023R), Materials, Table 1, p. 521-CPS-2 [36]
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  Geomembrane and geosynthetic clay liner (GCL) materials must meet the requirements in table 1. ... Type 1 Name Minimum Thickness (mil) 2 Wastewater Clear Water ... HDPE Polyethylene 60 30 ... LLDPE Polyethylene 60 30 ... LLDPE-R Polyethylene 45 24 PVC Polyvinyl Chloride 40 30 ... EPDM Diene Terpolymer 45 45 ... FPP Polypropylene 45 30 ... FPP-R Polypropylene 45 3 36 ... PE-R Polyethylene NR 3 36 ... GCL Liner 0.75 lbs./square foot ... 1 mil = 1/1000 inch 3 NR – Not recommended for waste storage.

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• DefinitionNRCS CPS 522 (national, May 2016) defines Pond Sealing or Lining - Concrete as a liner for an impoundment constructed using reinforced or nonreinforced concrete. Its 'Conditions Where Practice Applies' section lists three bulleted conditions, without saying whether all or any of them must be met: in-place natural soils have excessive seepage rates; construction of a compacted soil liner is not feasible with available soils; and use of the impoundment requires concrete both as a liner and a protective subgrade cover.

  NRCS CPS Pond Sealing or Lining - Concrete (Code 522), NHCP May 2016, Definition; Conditions Where Practice Applies, p. 522-CPS-1 [37]
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  A liner for an impoundment constructed using reinforced or nonreinforced concrete. ... This practice applies where— • In-place natural soils have excessive seepage rates. • Construction of a compacted soil liner is not feasible with available soils. • Use of impoundment requires concrete both as a liner and a protective subgrade cover.

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• StatusPROPOSED (not final): On September 1, 2026 NRCS published a notice of availability and request for comments (91 FR 56102-56106, FR Doc. 2026-17863, Docket No. NRCS-2026-0100) proposing revisions to 48 conservation practice standards, including Pond Sealing or Lining, Compacted Soil Treatment (Code 520) and Pond Sealing or Lining, Concrete (Code 522). Comments received by October 1, 2026 will be considered.

  91 FR 56102 (Sept. 1, 2026), FR Doc. 2026-17863, Docket No. NRCS-2026-0100 [13]
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  [Docket No. NRCS-2026-0100] Proposed Revisions to the National Handbook of Conservation Practices ... ACTION: Notice of availability, request for comments. ... DATES: We will consider comments that we receive by October 1, 2026. ... NRCS is requesting comments on the following 48 CPSs: ... Pond Sealing or Lining, Compacted Soil Treatment (Code 520); Pond Sealing or Lining, Concrete (Code 522);

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• StatusPROPOSED: The Sept. 1, 2026 notice describes the CPS 520 changes as: no major technical revisions; clarifications, examples and readability edits; two purposes added; new criteria on compliance with applicable laws, safety, and existing impoundment requirements; and a reduced minimum liner thickness for clean-water storage impoundments.

  91 FR 56102, 56105 (Sept. 1, 2026), Pond Sealing or Lining, Compacted Soil Treatment (Code 520) [13]
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  Pond Sealing or Lining, Compacted Soil Treatment (Code 520): No major technical revisions were made to this CPS. All updates were made to clarify content, provide examples, improve readability, and maintain consistency across paragraphs. Two purposes were added to the ``Purpose'' section, and new criteria were included in the ``Criteria'' section regarding compliance with applicable laws, safety, and existing impoundment requirements. The minimum liner thickness for clean-water storage impoundments was reduced in the ``Criteria'' section.

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• Size cutoffPROPOSED CPS 520 (draft dated September 2026, posted by NRCS for the Docket NRCS-2026-0100 comment period): the Table 1 minimum liner thickness by depth would remain (12 in for <=16 ft; 18 in for 16.1-24 ft; 24 in for 24.1-30 ft) 'unless the impoundment is for water storage where the minimum thickness is 12 inches at all depths.'

  Applies when: Proposed; water-storage (clean water) impoundments NRCS CPS 520, proposed draft "520 NHCP CPS Pond Sealing or Lining, Compacted Soil Treatment 2026 FR" (NHCP September 2026), Liner thickness, Table 1, p. 520-CPS-2 [38]
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  The minimum liner thickness as shown in Table 1 unless the impoundment is for water storage where the minimum thickness is 12 inches at all depths. Table 1. Minimum liner thickness by depth. Design Storage Depth (ft) Liner Thickness (in) ≤16 12 16.1–24 18 24.1 - 30 24

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• RequirementPROPOSED CPS 520 (Sept. 2026 draft) would add general criteria that the liner be planned, designed and constructed to comply with all federal, state, tribal and local laws and regulations, and that 'The landowner or operator is responsible for obtaining all necessary permits and approvals prior to, during, and after construction of the facility.' Its Purpose section would list three purposes: reduce seepage losses from impoundments constructed for water conservation including irrigation or water for livestock; reduce pollution to surface and groundwater, including potential drinking water sources; and protect soil and water from contaminants or erosion. (The Sept. 1, 2026 notice describes two purposes as added; the current 2016 standard has one purpose.)

  NRCS CPS 520, proposed draft (NHCP September 2026), Purpose; General Criteria Applicable to All Purposes, p. 520-CPS-1 [38]
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  Reduce seepage losses from impoundments constructed for water conservation including irrigation or water for livestock. • Reduce pollution to surface and groundwater, including potential drinking water sources. • Protect soil and water from contaminants or erosion. ... Plan, design, and construct the liner to comply with all federal, state, tribal, and local laws and regulations. The landowner or operator is responsible for obtaining all necessary permits and approvals prior to, during, and after construction of the facility.

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• StatusPROPOSED: The Sept. 1, 2026 notice says the only major technical revision to CPS 522 is the addition of leak-detection requirements for installations in high-permeability soils; two purposes were added and criteria added on compliance with applicable laws, safety, and existing impoundment requirements.

  91 FR 56102, 56105 (Sept. 1, 2026), Pond Sealing or Lining, Concrete (Code 522) [13]
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  Pond Sealing or Lining, Concrete (Code 522): The only major technical revision to this CPS was the addition of leak-detection requirements for installations in high-permeability soils. Other revisions throughout the CPS were made to clarify content, provide examples, improve readability, and maintain paragraph structure. Two purposes were added to the ``Purpose'' section, and additional criteria were included in the ``Criteria'' section to address compliance with applicable laws, safety, and existing impoundment requirements.

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