The Evidence Base
Read From Source
Every standard and study behind our claims, quoted from the original document, with access status and limitations stated. Including the parts that qualify our own position.
How To Read This Page
Pond sealing attracts a lot of confident advice and very little citation. This page is the underlying record for the claims we make elsewhere on this site: the federal standard, the two land-grant extension publications, the peer-reviewed geoenvironmental literature, the government geology, and the test method. Each entry gives the full citation, a link, what the document actually measured, and direct quotations rather than our paraphrase.
Three rules govern this page, and they are the reason it is worth reading:
- Every figure here was read out of the source document. Nothing is reproduced from a vendor summary, a blog, or a search snippet.
- Access is disclosed. Where we could only reach an abstract, or could not reach the paper at all, the entry says so and we do not summarize what we have not read. Three papers are in that category and are listed under what we withhold.
- Our own laboratory results are labeled as ours. We do not present them as independent findings.
Where the evidence limits our position, or cuts against it, that is stated in the same type size as the rest. If you are evaluating a supplier’s claim, the useful question is the one we have tried to make answerable here: which document is that number from, and does that document actually measure the thing being claimed?
Standards And Extension Guidance
These three documents are what a designer, an inspector, or a county agent will actually hold you to. They are also the only sources on this page that state application rates.
Conservation Practice Standard 520 — Pond Sealing or Lining, Compacted Soil Treatment
USDA Natural Resources Conservation Service, Conservation Practice Standard Code 520, May 2016. Full standard (PDF). A 2026 redline revision is in public review; the figures below are from the May 2016 version currently in force.
- What it is
- The federal specification for sealing an impoundment with compacted soil, with or without amendment. It defines the practice as “a liner for an impoundment constructed using compacted soil with or without soil amendments” and applies where “in-place natural soils have excessive seepage rates” and suitable soil is available for treatment. It is a construction standard, not a product endorsement.
- The material requirement, verbatim
“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.”— CPS 520, Bentonite Material
The conditional clause is the part most often dropped when this standard is quoted. It is not a ban on lower-swell clay; it is a transfer of cost and liability. Material meeting the 22 mL floor can be designed from the published rates below. Material that does not meet it can only be used if project-specific laboratory testing establishes a rate. There is no published table for sub-specification bentonite, so any “just use more of the cheap one” figure a supplier offers is not derived from this standard.
- Application rates — note the unit
Table 3, minimum bentonite application rates for clean water ponds, applies per 1-inch lift thickness:
- Silts (ML, CL-ML) — 0.375 lb/ft²
- Silty sands (SM, SC-SM, SP-SM) — 0.5 lb/ft²
- Clean sand (SP, SW) — 0.625 lb/ft²
Because the maximum permitted lift is 6 inches, a single full lift of clean sand is 0.625 × 6 = 3.75 lb/ft². Rates quoted from this table without the lift basis understate the requirement by up to six times. The standard introduces the table with the condition “in the absence of laboratory tests or field performance data on soils similar to those to be treated.”
- Geometry and construction
- Minimum finished liner thickness by design storage depth (Table 1): 12 in up to 16 ft, 18 in for 16.1–24 ft, 24 in for 24.1–30 ft — or thicker if a seepage design value or state regulation requires it.
- Maximum lift thickness 6 inches.
- Side slopes 3H:1V or flatter for the “bathtub” method; as steep as 2H:1V may be considered using the “stair-step” method of Appendix 10D of the AWMFH.
- Where a seasonal high water table can rise above the lowest liquid level, the design must protect against uplift — perimeter drains, a maintained minimum liquid depth, or a liner heavy enough to resist it.
- What it does not say
- The standard does not contain an instruction to drain the pond, and we do not claim that it does. It does not need to: every operation it specifies — placing measured lifts, mixing to full depth, compacting to a density — is dry-earthwork. The explicit instruction against applying through water comes from Missouri Extension, below.
What this supports. A 22 mL free-swell floor tied to ASTM D5890; rates that are per-lift, not per-pond; a minimum thickness set by water depth; and the fact that using off-spec clay requires your own laboratory testing rather than a rule of thumb.
What it does not support. Any equivalence ratio between a high-swell and a low-swell clay. The standard offers no such conversion.
Reducing Pond Seepage — publication G1555
Pfost, D.L., Williams, D. and Koenig, R. Reducing Pond Seepage, University of Missouri Extension publication G1555 (revised). extension.missouri.edu/publications/g1555
- Why this one matters most
- Of every source on this page, this is the one that addresses the through-water question directly and without hedging. Two sentences:
- Verbatim
“The pool should be dry before application.”
“Bentonite should not be broadcast on the water surface.”— G1555, Bentonite“There are two varieties of bentonite: Sodium (Wyoming or western), which has a high swelling capacity in water; Calcium (southern), with negligible swelling capacity. … Only sodium bentonite should be used for pond or reservoir sealing.”— G1555, Bentonite
- Rates, and their basis
G1555 puts the laboratory requirement first: “Application rates for bentonite should be based on laboratory tests.” Only in the absence of that data does it give figures — from 1 lb/ft² for a soil with some clay up to 3 lb/ft² for sand-gravel material, and per each 4-inch lift. That is a third different lift basis from the two other documents on this page, which is precisely why a bare lb/ft² number quoted with no lift thickness is meaningless.
- Useful context for diagnosing a leak
- “Seepage loss of 2 inches or less per month should be considered acceptable.”
- Evaporation in Missouri can reach half an inch per day, with a quarter inch per day common in high summer — so a falling gauge is not automatically a leak.
- “Ponds will always lose water during the first fill, because water is absorbed by the embankment and the soils under the reservoir,” and the water mound beneath a new pond may take a couple of years to form.
- Also covered
- Dispersant rates per 6-inch lift — soda ash 10–25 lb/100 ft², sodium chloride 20–33 lb/100 ft², sodium polyphosphate 5–10 lb/100 ft² — with tetrasodium pyrophosphate and sodium tripolyphosphate preferred over other polyphosphate salts.
What this supports. A land-grant extension service stating in plain words that the pool should be dry and that bentonite should not be broadcast on the water surface; that only sodium bentonite is suitable for pond sealing; and that rates properly come from laboratory testing.
Note the disagreement. G1555 is more categorical than Texas A&M, which allows a sprinkle method as a last resort. We have not smoothed that over. Where two extension services differ, both are quoted here.
Sealing Ponds and Lakes with Bentonite
Texas A&M AgriLife Extension Service. Sealing Ponds and Lakes with Bentonite. Current web edition · earlier PDF edition. No author or publication date is stated on either edition.
- Why we cite a Texas source against Texas clay
- This publication is from the extension service of the state whose bentonite deposits are the low-swell ones (see the geology). It is not a competitor’s document, and it is the most detailed method description of the three.
- Three methods, ranked by the source itself
- Blanket method — strip the top 4 to 6 inches, fill crevices with 1 part bentonite to 5 parts soil, spread bentonite evenly over the bottom, replace the soil cover, compact by rolling or tamping. “When done correctly, the blanket method usually produces more effective seepage control than the sprinkle method.”
- Mixed blanket method — disk the bentonite into the top 4 to 6 inches and compact; no cover coat needed. The source cautions it “may be less effective than the blanket method because of uneven mixing,” leaving strips or spots too low in bentonite, and advises increasing the amount to compensate.
- Sprinkle method — coarse granular bentonite scattered on the water surface and allowed to sink. Quoted in full below.
- What it says about the sprinkle method
“The sprinkle method is less effective than other methods. Accurate, uniform placement of bentonite is difficult to accomplish. This method is not recommended for ponds where livestock may wade in the water and disturb the bentonite layer. The sprinkle method is useful in emergencies when isolated leaks need to be stopped.”— Current web edition
“The ‘sprinkle method’ is recommended only when it is impractical to drain the water from the area to be treated.”— Earlier PDF edition
Both editions frame it the same way: a fallback for an isolated leak when draining is impractical, not a way to seal a pond bottom. The current web edition words the condition as “if it is impractical to drain the pond, the sprinkle method can be used.”
- Rates, and a candid allowance
- General range 1 to 2 lb/ft² of soil surface.
- Half a pound per square foot “is usually satisfactory when the bottom of the pond is fine sand or sandy loam and the maximum water depth is less than 6 feet.”
- Same soil at 6 to 20 ft of depth: increase to 1 lb/ft². “Greater water depths increase the pressure on the bottom of the pond and require more bentonite.”
- After trial testing to find the minimum effective amount, “add 25 to 50 percent more to allow for greater water depths … and challenges with even distribution during the treatment process.”
That last item is worth dwelling on: even for dry, controlled placement the source adds a quarter to a half again for distribution error. Uniformity is the whole problem, and it is the thing you give up entirely when you broadcast into water.
What this supports. That placement uniformity governs performance; that deeper water requires more material; and that the sprinkle method is an emergency measure for isolated leaks, expressly less effective than dry placement.
What it does not support. It gives no separate application rate for the sprinkle method. Nobody has published one. That absence is the single most important gap on this page and it is the reason we publish no multiplier — see standing water.
The Peer-Reviewed Record
One caution before the detail. This literature measures hydraulic conductivity — how fast a liner leaks — in geosynthetic clay liners, where bentonite is confined between geotextiles. It does not measure how many tons of a site-mixed soil-bentonite blanket you need. It tells you that clay quality changes leakage rate. It does not tell you that quantity substitutes for quality, and it does not give you an exchange rate between the two.
Correlating the hydraulic conductivities of GCLs with some properties of bentonites
Ören, A.H., Yükselen-Aksoy, Y., Önal, O. and Demirkıran, H. (2018). Geomechanics and Engineering, 15(5), 1091–1100. doi:10.12989/gae.2018.15.5.1091 · publisher PDF. Dokuz Eylül University; funded by TÜBİTAK grant 111M718.
- What they did
- Measured hydraulic conductivity on a set of conventional GCLs and polymer-amended GCLs using both deionized water and tap water as permeants, then regressed those conductivities against index properties of the bentonites: clay content, liquid limit, plasticity index, swell index, smectite content, specific surface area and cation exchange capacity. Because conductivity to deionized and tap water differed negligibly, the two datasets were combined for the swell-index regression, giving 20 observations — the paper states the residual degrees of freedom as 18.
- The swell-index relationship
- The fitted equation, the paper’s Eq. (4), with a correlation coefficient of 0.68:
k = 3.1 × 10−9 × e−0.055 SI— where k is hydraulic conductivity in cm/s and SI is swell index in mL per 2 g
Evaluating that curve at three swell indices gives 5.9 × 10−10 cm/s at 30 mL, 9.2 × 10−10 cm/s at 22 mL and 1.6 × 10−9 cm/s at 12 mL — about 2.7 times the conductivity at 12 mL versus 30 mL. Those three numbers are our arithmetic on the authors’ equation, not values the authors report. The equation and the 0.68 are theirs.
- Where swell index ranked — including against us
Swell index was not the strongest predictor in this study. Reported correlation coefficients:
- Clay content — 0.85, the highest of any parameter
- Liquid limit — 0.82
- Plasticity index — 0.80
- Swell index — 0.68
- Smectite content, specific surface area, cation exchange capacity — poor, R < 0.5
We publish this because it qualifies our own emphasis. Swell index is a useful, fast, standardized screen — it is not the best available predictor of leakage in this dataset, and we would rather you heard that from us.
- The smectite result, which is counter-intuitive
- Conductivity fell from 2.0 × 10−9 to 5.0 × 10−10 cm/s as smectite content rose from 60% to 77%, fitted as Eq. (5), k = 3.1 × 10−8 × e−0.051 SC — but with a correlation coefficient of only 0.43, which the authors themselves call “rather poor.” Mineral content alone is a weak predictor. This matters for the geology section: how much montmorillonite a clay contains is not the same question as how it behaves in water.
- Limits of this paper for our purpose
- It is a GCL study. Bentonite is confined between geotextiles and restrained by needle-punched fibers. A site-mixed blanket at a given lb/ft² is a different system.
- R = 0.68 on 20 points is a trend, not a design equation.
- It predicts conductivity. Converting conductivity into an equivalent tonnage of lower-grade clay requires an assumption no author in this literature makes.
What this supports. That bentonite quality measurably changes how fast a liner leaks, and that swell index is a legitimate, if imperfect, index for it.
What it does not support. Any “use N times more of the cheap clay” figure. If a supplier gives you one, ask which study it is from.
Three papers we are not summarizing yet
Figures from these papers currently appear on our ASTM D5890 page as reported by Ören et al. (2018). We have not been able to read the originals, so this page gives citations only. Detail will be added when we have the source documents in hand.
- The papers
- Lee, J.M. and Shackelford, C.D. (2005). “Impact of Bentonite Quality on Hydraulic Conductivity of Geosynthetic Clay Liners.” Journal of Geotechnical and Geoenvironmental Engineering, 131(1), 64–77. doi:10.1061/(ASCE)1090-0241(2005)131:1(64)
- Lee, J.M., Shackelford, C.D., Benson, C.H., Jo, H.Y. and Edil, T.B. (2005). “Correlating Index Properties and Hydraulic Conductivity of Geosynthetic Clay Liners.” Journal of Geotechnical and Geoenvironmental Engineering, 131(11), 1319–1329. doi:10.1061/(ASCE)1090-0241(2005)131:11(1319)
- Ashmawy, A.K., El-Hajji, D., Sotelo, N. and Muhammad, N. (2002). “Hydraulic performance of untreated and polymer-treated bentonite in inorganic landfill leachates.” Clays and Clay Minerals, 50(5), 546–552.
- Why we are being this careful
- Ören et al. cite “Lee and Shackelford (2005)” in their text and report that the higher-quality GCL had 86% montmorillonite and a conductivity to water of 7.0 × 10−10 cm/s, against 77% and 2.4 × 10−9 cm/s for the lower-quality GCL. We reproduce those figures with that attribution. But the 131(1) paper does not appear in Ören’s own reference list — the in-text citation is unresolved in the published article. A number that has passed through a secondary source with a broken reference chain is not a number we are willing to build a detailed summary on.
- What would change this
- The two ASCE papers are available through the ASCE Library store, which sells article packs rather than single articles. The Ashmawy paper is in Clays and Clay Minerals volume 50. When we have all three, each will get the same treatment as Ören above.
Why this entry exists at all. Leaving it out would have been easier and would have made the page look stronger. Naming the gap is the more useful disclosure, and it tells you exactly how much weight the 86%/77% comparison should carry.
Why Geography Decides Quality
This is the part of the argument that no application rate can touch, and it is documented by the United States Geological Survey rather than by anybody selling clay.
Bentonite and Fuller’s Earth Resources of the United States
Hosterman, J.W. and Patterson, S.H. (1992). Bentonite and Fuller’s Earth Resources of the United States. U.S. Geological Survey Professional Paper 1522. pubs.usgs.gov/pp/1522/report.pdf
- The distinction is chemical, not just mineral
“Sodium is the dominant exchangeable ion in the Wyoming (Na or swelling) bentonites, and calcium is the dominant ion in the southern (Ca or nonswelling) bentonites.”— USGS PP 1522
Swelling is governed by which cation sits on the exchange sites. That is a property of the deposit, fixed by its depositional and diagenetic history. Adding tonnage does not change it.
- Where the good clay is
- “The best grade swelling bentonite occurs in the Mowry Shale of Cretaceous age in Wyoming and Montana.”
- “All of the bentonite that has been mined in South Dakota, Wyoming, and Montana, the principal source of sodium-bentonite in the United States, is from beds of Cretaceous age.”
- The Clay Spur Bentonite Bed, near the top of the Mowry Shale, “was the first bed mined and has been the major source of bentonite in the entire region.”
- Where the nonswelling clay is
“The most abundant nonswelling bentonite is found in Tertiary formations of the Jackson and Claiborne Groups in Texas.”— USGS PP 1522
- The detail that settles the “more montmorillonite” objection
“Bentonite beds in the Claiborne Group (lower and middle Eocene) and the Jackson Group (upper Eocene) contain 90-100 percent montmorillonite.”— USGS PP 1522
Read that alongside the sentence above it. The Texas beds are 90 to 100 percent montmorillonite and are still classified by the USGS as the nonswelling variety, because the dominant exchangeable ion is calcium rather than sodium. High montmorillonite content does not make a clay swell. This is also consistent with Ören et al. finding smectite content a poor predictor of conductivity (R = 0.43) while swell index and plasticity performed far better. If a supplier quotes you a montmorillonite percentage instead of an ASTM D5890 swell index, this is the paragraph to read back to them.
- A fair caveat
- PP 1522 is a resource assessment of industrial clay deposits, written for the drilling-mud, foundry-sand and taconite-pelletising markets. It is not a pond-sealing document and makes no recommendation about impoundments. We cite it for what it does establish: the geographic and geochemical distribution of swelling versus nonswelling bentonite in the United States.
What this supports. That swell capacity is a property of the deposit, set by exchangeable cation chemistry; that the premium sodium bentonite is Cretaceous, from Wyoming, Montana and South Dakota; and that the abundant Texas material is the nonswelling calcium variety despite being 90–100% montmorillonite.
The consequence for buyers. No quantity of a calcium bentonite converts it into a sodium bentonite. That is a geological fact, not a sales position.
The Test Method Itself
ASTM D5890 — Swell Index of Clay Mineral Component of Geosynthetic Clay Liners
ASTM International. Standard Test Method for Swell Index of Clay Mineral Component of Geosynthetic Clay Liners, ASTM D5890. store.astm.org/standards/d5890. The standard is sold, not published openly; we have read the Scope and the Significance and Use sections, which are shown publicly, and not the full procedure text.
- What the standard says it is for
“An index method that enables the evaluation of swelling properties of a clay mineral in reagent water for estimation of its usefulness for permeability or hydraulic conductivity reduction.”— ASTM D5890, Section 1.1
“Clay mineral quality can vary significantly and effect the hydraulic conductivity of the GCL composite.”— ASTM D5890, Section 4.2
- Why the unit is written mL/2 g
- The test hydrates a 2.00 gram oven-dried, ground sample in 100 mL of deionized water in a graduated cylinder and reads the settled volume of the swollen clay after a specified period. The sample is specified by mass, 2.00 g — not by volume. Results are therefore properly written as mL/2 g, which is how Ören et al. express the SI term in their regression. Where our site describes this as roughly 2 mL of dry clay, that is a conversion for illustration: at the bulk densities published on granular sodium bentonite technical data sheets, 2.00 g occupies roughly 1.9 to 2.6 mL. It is an honest approximation, and it is an approximation.
- What it is explicitly not
- By its own description this is an index test. It is a screening measurement on the clay mineral component, not a permeability test on a finished liner and not a design method. CPS 520 uses it exactly that way: as a threshold a material must clear before published application rates may be used.
Access note. Because we have not read the full standard, this entry stays at the level of the publicly posted Scope and Significance and Use. The 22 mL threshold we quote comes from CPS 520, which is open, not from the ASTM text.
Applying Through Standing Water
This is the question we are asked most, and it is the one where the published record and thirty years of our own field experience point the same direction. Collected in one place:
Missouri Extension G1555 is unambiguous. “The pool should be dry before application.” “Bentonite should not be broadcast on the water surface.”
Texas A&M AgriLife allows it only as a fallback. The sprinkle method “is recommended only when it is impractical to drain the water from the area to be treated,” it “is less effective than other methods,” “accurate, uniform placement of bentonite is difficult to accomplish,” and it is “useful in emergencies when isolated leaks need to be stopped.”
NRCS CPS 520 specifies only dry earthwork. Measured lifts of 6 inches or less, mixed to full depth, compacted to a density, on slopes flat enough to run a compactor. The standard does not discuss broadcasting into water because none of its operations can be performed that way.
Why the mechanism fails, not just the paperwork
A seal requires three things at once: the clay has to be where the water is actually leaving, it has to be confined, and it has to be compacted. Broadcasting onto a water surface delivers none of them. You cannot aim it, the seepage path will not reliably draw it in, and it settles as a loose unconfined layer on the bottom rather than being mixed into the soil and compacted. Most of what you buy comes to rest where there was never any seepage to begin with. Texas A&M adds 25 to 50 percent to a measured rate to cover distribution error under dry, controlled placement — uniformity is the governing problem even at its easiest.
What we will not tell you
We will not give you a multiplier. We looked for one specifically. No source on this page — and no source we have found anywhere — publishes a separate application rate for the sprinkle method or an equivalence ratio against dry placement. Texas A&M says it is “less effective” and assigns it no rate at all. The retired NRCS 521C bentonite standard gave rates per treated layer only. Anyone quoting you a precise through-water figure is not getting it from the literature.
What we will tell you is what we have seen. In our own experience the quantity required to chase broad or diffuse seepage through standing water is high enough that the material cost alone usually exceeds the cost of draining the pond and doing the job once. That is our field judgment, offered as field judgment and not dressed up as a laboratory result.
The distinction that gets blurred
A trench repair around a drain pipe, a spillway, or through a dam is a different operation and it works at modest quantity: it is excavated, mixed at a high rate, and recompacted — confined and compacted, exactly as CPS 520 requires. Do not let anyone use the success of that kind of repair as evidence that broadcasting across open water seals a pond bottom.
What We Withhold, And What Is Ours
A page of citations is only as good as its disclosures. Ours, in one place:
Papers we have not read
Lee & Shackelford (2005), Lee et al. (2005) and Ashmawy et al. (2002) are cited on this site but are behind publisher paywalls. Where their figures appear, they are marked as reported by Ören et al. (2018). We give no detailed summary of any of the three, and we have noted that Ören’s reference list does not resolve the Lee & Shackelford in-text citation.
Numbers that are ours, not the literature’s
- The 30 mL PondLock® free swell index and the 12 mL typical Texas-source value are PondLock laboratory results by ASTM D5890. They are our own tests, disclosed as such, and they are not independent findings.
- The conductivity figures at 30, 22 and 12 mL quoted from Ören’s equation are our arithmetic on their published curve, not values those authors report.
- The claim that through-water application becomes uneconomic before it becomes effective is our field experience. No citation is offered because none exists.
Where the evidence is weaker than we would like
- The GCL literature is the best-controlled data available on bentonite quality, but it tests a confined manufactured product, not a site-mixed blanket at a given lb/ft².
- In Ören et al., swell index (R = 0.68) was a weaker predictor of conductivity than clay content (0.85), liquid limit (0.82) and plasticity index (0.80).
- CPS 520 is under revision and a 2026 redline draft is in public review. Figures here are from the May 2016 version in force.
- Neither extension publication states an author-attributed publication date on its current edition, so we cite them as revised editions.
- Water chemistry matters and is barely addressed by anything here. For brackish, saline or industrial water, site-specific testing beats any swell number, including ours.
References
- USDA Natural Resources Conservation Service. Conservation Practice Standard 520 — Pond Sealing or Lining, Compacted Soil Treatment (May 2016). nrcs.usda.gov · 2026 redline draft
- Pfost, D.L., Williams, D. and Koenig, R. Reducing Pond Seepage, University of Missouri Extension publication G1555 (revised). extension.missouri.edu/publications/g1555
- Texas A&M AgriLife Extension Service. Sealing Ponds and Lakes with Bentonite. web edition · earlier PDF edition
- Ören, A.H., Yükselen-Aksoy, Y., Önal, O. and Demirkıran, H. (2018). “Correlating the hydraulic conductivities of GCLs with some properties of bentonites.” Geomechanics and Engineering, 15(5), 1091–1100. doi:10.12989/gae.2018.15.5.1091
- Lee, J.M. and Shackelford, C.D. (2005). “Impact of Bentonite Quality on Hydraulic Conductivity of Geosynthetic Clay Liners.” Journal of Geotechnical and Geoenvironmental Engineering, 131(1), 64–77. doi:10.1061/(ASCE)1090-0241(2005)131:1(64) — not read; see disclosures
- Lee, J.M., Shackelford, C.D., Benson, C.H., Jo, H.Y. and Edil, T.B. (2005). “Correlating Index Properties and Hydraulic Conductivity of Geosynthetic Clay Liners.” Journal of Geotechnical and Geoenvironmental Engineering, 131(11), 1319–1329. doi:10.1061/(ASCE)1090-0241(2005)131:11(1319) — not read; see disclosures
- Ashmawy, A.K., El-Hajji, D., Sotelo, N. and Muhammad, N. (2002). “Hydraulic performance of untreated and polymer-treated bentonite in inorganic landfill leachates.” Clays and Clay Minerals, 50(5), 546–552. — not read; see disclosures
- Hosterman, J.W. and Patterson, S.H. (1992). Bentonite and Fuller’s Earth Resources of the United States. U.S. Geological Survey Professional Paper 1522. pubs.usgs.gov
- ASTM International. Standard Test Method for Swell Index of Clay Mineral Component of Geosynthetic Clay Liners, ASTM D5890. store.astm.org/standards/d5890