
    Steve V.B. KELLER, Plaintiff, Appellant, v. UNITED STATES of America, Defendant, Appellee.
    No. 94-1136.
    United States Court of Appeals, First Circuit.
    Heard June 10, 1994.
    Decided Oct. 19, 1994.
    
      Christopher Cole, Manchester, NH, with whom Michael J. Donahue, Donahue, McCaf-frey, Tucker & Ciandella, Exeter, NH, David S. Brown, and Sheehan, Phinney, Bass & Green, Manchester, NH, were on brief, for appellant.
    Gretehen Leah Witt, Asst. U.S. Atty., with whom Paul M. Gagnon, U.S. Atty., Concord, NH, was on brief, for appellee.
    Before TORRUELLA, CYR and BOUDIN, Circuit Judges.
   CYR, Circuit Judge.

Plaintiff Steven V.B. Keller appeals from a belated judgment dismissing his Longshore and Harbor Workers’ Compensation Act suit, see 33 U.S.C. §§ 901-950, § 905(b) (1993) (LHWCA), to recover damages for injuries sustained in a fall on board a maritime vessel owned by defendant-appellee United States of America. As appellant has not demonstrated — nor careful scrutiny disclosed — that the unprecedented decision-making delay in this case rendered the district court’s findings unreliable, we affirm the judgment.

I

BACKGROUND

In 1978, the United States Navy converted the U.S.S. ARTHUR M. HUDDELL, a World War II Liberty Ship, into a non-motorized barge for storing and transporting maritime cable purchased by the Navy from Simplex Wire and Cable Co. The retrofitted HUDDELL was towed to Simplex’s facility at Newington, New Hampshire, for cable loading in May 1979, where it remained moored for two years.

The cargo hold had been adapted to house several round tanks, recessed sixteen feet into the ’tween deck. Simplex hired temporary employees — known as cable loaders — to descend into these tanks from the ’tween deck for the purpose of winding the incoming “wet” cable in concentric layers onto a spool. During the HUDDELL’s retrofitting, the Navy installed a nonremovable metal barrier around Tank 4 to prevent workers on the ’tween deck from falling into the tank. The barrier included two uninterrupted safety railings located at the top of an access ladder attached to the interior wall of the tank to permit access to and from the tank floor. In order to exit the tank, a cable loader would climb to the top rungs of the ladder, at which point three options were available for getting from the tank onto the ’tween deck floor: (1) holding onto a “grab bar,” which was attached to the ’tween deck floor and located six inches from the outside edge of the tank, then crawling forward and passing under the lower railing and between the vertical stanchions supporting the two railings; (2) stepping in a crouched position between the lower and upper railings of the barrier; or (3) climbing over the top railing located approximately five feet above the ’tween deck floor.

At the time Simplex hired Keller as a cable loader, he was a nonmatrieulating sophomore at the University of New Hampshire. On the night of November 4, 1979, Keller went to a bar, where he and his friends drank approximately 120-160 ounces (or two six-packs) of beer between 10:00 p.m. and 11:20 p.m. Keller reported for work at about 11:30 p.m., and was assigned to Tank 4 for the first time. He and several coworkers climbed down the ladder from the ’tween deck into Tank 4 without incident, where they loaded cable until 2:00 a.m.

When it came time for a work break, Keller climbed to the top of the ladder, and, according to coworker Rhonda Rossley, grabbed the lower safety railing with his left hand and placed his left foot on one of the two top rungs of the ladder. Then, as he began to raise his right leg, he fell backward, neither attempting to regain his purchase nor crying out, and plummeted to the tank floor sixteen feet below, landing on his head. When a Simplex foreman administered first aid, he detected the odor of alcohol. A blood-alcohol test taken at 3:00 a.m., some three and one-half hours after Keller had reported for work, revealed a .14 blood-alcohol level, well above the .10 prima facie blood-alcohol level for demonstrating that a motor vehicle operator is under the influence. See N.H.Rev.Stat.Ann. § 262-A:63 (1963) (amended 1994, lowering limit to .08). Since the fall, Keller has remained amnesiac as to all events surrounding the accident.

Following a seven-day bench trial on Keller’s claims against the United States for negligently installing “unsafe” lighting and railings and an “unsafe” ladder in Tank 4, and for failing to warn Simplex workers of the potential danger, see 33 U.S.C. § 905(b), the district court ultimately awarded judgment to the United States. See Keller v. United States, No. 81-549-SD, 1993 WL 743979 (D.N.H. Dec. 30, 1993).

TI

DISCUSSION

Three principal issues must be addressed. First, did the eight-year lapse between the bench trial and entry of final judgment deprive the trial court findings of the customary deference on appeal, or violate Keller’s constitutional rights to access to the courts and due process, see generally U.S. Const, amends. I, V? Second, did the district court make clearly erroneous factual findings, or fail to make required findings, see Fed. R.Civ.P. 52(a), regarding the alleged breach of the vessel owner’s “turnover” duties of care? Third, did the district court misdefine a vessel owner’s “continuing” duty to inspect or supervise cargo loading operations for developing hazards?

A. The Decision-making Delay

First, Keller claims that an unprecedented eight-year delay between trial and the entry of judgment, coupled with the trial judge’s failure to refresh his recollection through recourse to a complete trial transcript prior to making findings of fact, resulted in a violation of his constitutional right to “access to the courts” and to due process, see U.S. Const, amends. I, V; Ad Hoc Comm. on Judicial Admin. v. Massachusetts, 488 F.2d 1241, 1244 (1st Cir.1973) (noting that pretrial delay might violate constitutional rights if a civil litigant is “denied for too long his day in court”), cert. denied, 416 U.S. 986, 94 S.Ct. 2389, 40 L.Ed.2d 763 (1974), or in a violation which warrants withholding the customary appellate deference accorded trial court findings. Cf. Chamberlin v. 101 Realty, Inc., 915 F.2d 777, 787 (1st Cir.1990) (excusing two-year delay); Fernberg v. T.F. Boyle Transp., Inc., 889 F.2d 1205, 1209 (1st Cir.1989) (excusing two and one-half year delay). Keller attributes the purported generality in the district court findings, see infra Section II.B, to this extended decision-making delay, and implicitly relies on a conclusive presumption that the court was unable to make more complete and detailed findings as it could not' recall the evidence presented at trial almost eight years earlier.

Keller concedes that neither Chamberlin nor Femberg concluded that prolonged decision-making delay, per se, requires vacatur. Nor has he cited authority for a per se rule fixing an outer limit on decision-making delay. Cf. Ad Hoc Comm., 488 F.2d at 1244 (rejecting per se rule under Federal Constitution for bounding decision-making delay in state court civil cases); cf. also, Los Angeles County Bar Ass’n v. March Fong Eu, 979 F.2d 697, 705-06 (9th Cir.1992) (conducting ad hoc inquiry to determine whether pretrial delay “exceed[ed] constitutional boundaries”).

There are sound reasons for abjuring a per se rule even in cases involving plainly excessive delay. In the first place, ad hoc appellate scrutiny is indispensable to the core determination whether delay rendered the decision unreliable. Secondly, it is highly doubtful that direct appellate review affords “an effective means of enforcing district court timeliness.” See Phonetele, Inc. v. American Tel. & Tel. Co., 889 F.2d 224, 232 (9th Cir.1989) (delay approximating four years), cert. denied, — U.S.—, 112 S.Ct. 1283, 117 L.Ed.2d 508 (1992). Thirdly, remands for reconsideration or retrial yield yet further delays, exacerbating the burdens on litigants. For these reasons, and notwithstanding our parallel supervisory responsibility, see, e.g., 28 U.S.C. § 1651 (mandamus jurisdiction); Petition of Henneman, 137 F.2d 627, 630 (1st Cir.1943), we consider it critically important that appellate attention remain focused on ensuring that trial court findings, despite inordinate decision-making delay, not be squandered unless their reliability has been undermined. We therefore opt for careful de novo scrutiny of the entire record with a view to whether the prolonged delay in reaching a decision rendered the trial court’s findings of fact unreliable to the degree that vacation of its judgment is warranted despite the admittedly severe impediments to reliable fact-finding in the event of a remand for new trial. Cf. Barker v. Wingo, 407 U.S. 514, 532, 92 S.Ct. 2182, 2193, 33 L.Ed.2d 101 (1972) (long pretrial delays threaten to impair criminal defense, lest witnesses die, disappear, or suffer memory loss or distortion).

Notwithstanding the eight-year interval between trial and judgment, for which we have been unable to glean adequate explanation, neither Keller nor the record on appeal suggests that the district court did not perform its decision-making responsibility with care. As Keller’s several requests to expedite the decision-making process acknowledge, the district court was in no sense indifferent to its responsibility to render a decision but encountered extraordinary docket pressures at the same time it was required to give precedence to its criminal caseload. See Speedy Trial Act, 18 U.S.C. § 3161 (1993).

Nor would we well serve the interests of justice, or the integrity of the decision-making process, were we to presume that the absence of a complete trial transcript rendered the district court incapable of determining matters relating to witness demeanor and credibility, or to recollect or reconstruct trial testimony, through other reliable means (viz., trial notes, voluminous trial exhibits). See Keller, No. 81-549-SD, slip op. at 16 (“The court in the course of rendering its decision has reviewed all of the exhibits _”). After all, the responsibility incumbent on an appellant to substantiate a challenge to the sufficiency of trial court findings is not met merely with conclusory allegations that the trier of fact could not have recalled or reconstructed the evidence without a complete trial transcript. Moreover, this case does not require us to speculate as to the reliability of the trial judge’s findings, since a complete trial transcript is available for the purpose. Thus, as regards the claim that the trial judge’s findings themselves evince prejudice from the extended decision-making delay, we test Keller’s thesis as in any other case, by inquiring whether the findings were infected with “clear error” based on our own painstaking scrutiny of the entire trial record, including a complete trial transcript. See Interstate Commerce Comm’n v. Holmes Transp., Inc., 983 F.2d 1122, 1129 (1st Cir.1993) (noting that appellate court must defer to trial court fact-finding unless, after reviewing entire record, it is left with the “definite and firm conviction that a mistake has been committed”).

B. The Merits

The district court made seven findings central to the merits-related challenges advanced on appeal:

(1) Keller was a “longshore worker” to whom defendant owed a duty of “ordinary care,” under LHWCA section 905(b), to provide a vessel in such condition that “an expert and experienced stevedore [would] be able to exercise reasonable care to carry on its cargo operations with reasonable safety,” and a duty to warn the stevedore of any latent safety defects on the vessel not reasonably discoverable by an “expert and experienced” stevedore, Keller, No. 81-549-SD, slip op. at 9-10 (quoting Scindia Steam Navigation Co. v. de los Santos, 451 U.S. 156, 166-67 [101 S.Ct. 1614, 1621-22, 68 L.Ed.2d 1] (1981));
(2) Defendant’s expert witness, Jan Bijhouwer, relying on “applicable” maritime safety standards in formulating his opinion that the HUDDELL’s ladder design was “safe,” proved “more persuasive” than plaintiffs competing expert, id. at 13;
(3) No eyewitness observed the precipitating cause of the fall (e.g., whether Keller hit his head on a safety rail), id. at 11-12;
(4) Even if the design of the ladder deviated from “applicable” maritime safety standards in certain respects, there was insufficient evidence that these deviations caused Keller’s fall. No other accidents occurred on this ladder, despite the fact that no less than twelve persons climbed up or down the ladder under identical conditions immediately prior to and after Keller’s accident, id. at 13;
(5) Keller’s blood alcohol level of .14, see supra at p. 4, might have been a “significant [causal] factor” in the accident, Keller, No. 81-549-SD, slip op. at 15;
(6) If any design deviation constituted a potential “hazard,” such hazard was obvious (i.e., not latent), and could be “anticipate^]” by a stevedore “if reasonably competent in the performance of his work,” id. at 13-14; and
(7) Even if custom had required that defendant place a representative aboard the HUDDELL to monitor cargo loading, “a custom-generated duty to supervise and inspect does not transfer to the ship owner a duty to eradicate dangers reasonably known to and managed by the stevedore,” id. at 14.

1. The Vessel Owner’s “Turnover” Duties of Care

a. Applicable Law

The definition of a vessel owner’s duties of care under LHWCA § 905(b) is a matter of law for the district court in the first instance, see Elberg v. Mobil Oil Corp., 967 F.2d 1146, 1149 (7th Cir.1992); Ludwig v. Pan Ocean Shipping Co., 941 F.2d 849, 850 (9th Cir.1991), subject to de novo review, see Williams v. Poulos, 11 F.3d 271, 278 (1st Cir.1993). Keller claims that by failing to distinguish between “turnover” and “continuing” duties, the district court misconstrued the standard of care incumbent upon a vessel owner under LHWCA § 905(b).

As it pertains to Keller and Simplex, in its current incarnation the LHWCA is a strict liability statute. A longshore or harbor worker such as Keller, who incurs a work-related injury, may recover disability and medical compensation from the stevedore-employer {viz., Simplex) even though the stevedore was not at fault. Conversely, an award of compensation under the LHWCA, such as Keller recovered from Simplex, is the longshore worker’s exclusive remedy against the stevedore-employer. See 33 U.S.C. §§ 904, 905(a); Williams v. Jones, 11 F.3d 247, 250 n. 1 (1st Cir.1993).

Until 1972, an injured longshore worker could sue the vessel owner on two distinct legal theories: negligence and breach of the warranty of “seaworthiness.” “Unseaworthiness” could be established more easily than negligence, simply by showing that some condition or appurtenance on board the vessel at the time of the accident was unreasonably hazardous, even if the stevedore-employer was the sole cause of the hazard. See Seas Shipping Co. v. Sieracki, 328 U.S. 85, 94, 66 S.Ct. 872, 877, 90 L.Ed. 1099 (1946); Ellen M. Flynn & Dale S. Cooper, 1A Benedict on Admiralty § 91, at 5-2 to 5-4 (7th ed. 1993) [hereinafter: Benedict on Admiralty ]. Vessel owners thus became virtual insurers of the on-board safety of longshore workers. Although the only legal recourse available to the nonnegligent vessel owner was an indemnification claim against the stevedore-employer, even that remedy was unavailable unless the hazardous condition or appurtenance was due to the stevedore’s negligence.

In 1972, the LHWCA remedial scheme underwent dramatic adjustment. Congress greatly increased the amount of compensation recoverable from the stevedore-employer, repudiated the warranty of “seaworthiness” as a basis for third-party actions against the vessel owner, required the injured longshore worker to prove negligence on the part of the vessel owner, and precluded a negligent vessel owner from obtaining indemnification from the stevedore-employer. See 33 U.S.C. § 905(b); supra note 2. These changes were designed “to shift more of the responsibility for compensating injured longshoremen to the party best able to prevent injuries: the stevedore-employer.” Howlett v. Birkdale Shipping Co., — U.S.—,—, 114 S.Ct. 2057, 2063, 129 L.Ed.2d 78 (1994) (emphasis added). Consequently, at the present time the duties of care incumbent upon a 'vessel owner fall into two broad categories: (i) so-called “turnover” duties — those which are to be discharged before the owner consigns the vessel to the stevedore for cargo loading operations — and (ii) so-called “continuing” duties, such as inspection, supervision or intervention, which may persist after the stevedore commences cargo operations. See Scindia, 451 U.S. at 166-67, 172-76, 101 S.Ct. at 1621-22, 1624-26. There are two distinct subcategories of “turnover” duty, depending on whether an unreasonably hazardous condition on board the vessel is patent or latent.

(i) The Vessel Owner’s “Duty of Safe Condition ”

First, the vessel owner’s “duty of safe condition” is met if the condition of the vessel when entrusted to the stevedore poses no reasonably foreseeable risk to any worker, even assuming a complete failure on the part of the stevedore-employer to monitor the vessel workplace for safety. On the other hand, because longshoring is particularly dangerous, in many respects inherently so, see Johnson v. A/S Ivarans Rederi, 613 F.2d 334, 339 n. 5 (1st Cir.1980), few on-board appurtenances would ever satisfy such an exacting threshold. Accordingly, the “foreseeability” standard to which a vessel owner is held under its “duty of safe condition” has been relaxed: “ordinary care under the circumstances” now governs the owner’s discharge of its duty to turn the vessel over “in such condition that an expert and experienced stevedoring contractor, mindful of the dangers he should expect to encounter, arising from the hazards of the ship’s service or otherwise, will be able by the exercise of ordinary care” to conduct cargo operations “with reasonable safety to persons and property.” See Federal Marine Terminals, Inc. v. Burnside Shipping Co., 394 U.S. 404, 416-17 n. 18, 89 S.Ct. 1144, 1151-52 n. 18, 22 L.Ed.2d 371 (1969) (emphasis added) (citation omitted).

Unlike the vessel owner, however, the stevedore is subject to detailed legislative and administrative prescriptions for affording its workers a “safe” workplace. See, e.g., 33 U.S.C. § 941 (1993); 29 C.F.R. §§ 1918.1-1918.106, § 1918.25 (1993) (implementing regulations for “ladders”); see also Scindia, 451 U.S. at 170, 101 S.Ct. at 1623-24. Thus, a vessel owner “reasonably” may rely on the stevedore-employer’s supervision of its own employees in their interaction with and avoidance of “obvious” or “anticipated” hazards foreseeably associated with stevedoring on board the owner’s vessel. See, e.g., Polizzi v. M/V Zephyros II Monrovia, 860 F.2d 147, 149 (5th Cir.1988); Jupitz v. National Shipping Co., 730 F.Supp. 1358,1362 (D.Md.1990) (noting that vessel owner’s duty is “to turn over the cargo area in a reasonably safe condition; ... not to turn over the area completely free of all hazards”) (emphasis added). Conversely, under current law a vessel owner may be held liable, even for “obvious” or “anticipated” hazards, upon a showing that the owner effectively disabled the stevedore-employer or the longshore worker from taking ameliorative measures to avoid the hazard. See Teply v. Mobil Oil Corp., 859 F.2d 375, 378 (5th Cir.1988); Theriot v. Bay Drilling Corp., 783 F.2d 527, 536 (5th Cir.1986).

(ii) The Vessel Owner’s “Duty to Warn ”

The second sub-category of turnover duty is the “duty to warn” prior to turnover, which requires the vessel owner to alert the stevedore-employer to any latent or concealed defect including “any hazards on the ship or with respect to its equipment” which “are known to the vessel [owner] or should be known to it in the exercise of reasonable care” and which “would likely be encountered by the stevedore in the course of his cargo operations^] are not known by the stevedore[,] and would not be obvious to or anticipated by him if reasonably competent in the performance of his work.” Scindia, 451 U.S. at 167, 101 S.Ct. at 1622 (emphasis added).

Although Keller concedes that the trial court correctly quoted verbatim from the Scindia exegesis relating to these two turnover duties Keller, No. 81-549-SD, slip op. at 10-11, he argues that the court focused its factual inquiry exclusively on whether the defendant vessel owner owed Keller a “continuing” duty of intervention. See Brief for Appellant at 27. We cannot agree. Though neither the district court, nor for that matter the Scindia Court, used the term “turnover duty,” the district court focused directly on the two issues material to the pertinent inquiry: (i) “[c]entral to the issue of legal fault in this litigation is whether the [original design of the] ladder at issue was causally defective,” in light of “applicable safety standards” and other evidence proffered by Keller, Keller, No. 81-549-SD, slip op. at 13, and (ii) whether “the notice given by the presence of any such hazard” rendered it obvious, id. at 14. Thus, the district court clearly identified and applied the proper duty of care. We turn then to examine its factual findings.

b. Factual Findings on “Turnover” Duties

Keller asserts two challenges to the district court finding that the United States did not breach its turnover duties. First, he argues that the pivotal finding — that the testimony of Jan Bijhouwer, defendant’s expert witness on marine design, was “more persuasive” than the testimony of plaintiffs expert — is so conclusory that no evidentiary basis for the finding can be gleaned from the record. See Fed.R.Civ.P. 52 (“In all actions tried upon the facts without a jury ... the court shall find the facts specially and state separately its conclusions of law there-on_”) (emphasis added).

The crux of our ad hoc Rule 52(a) inquiry is whether the trial court findings are precise and detailed enough to enable effective appellate review. See Knapp Shoes, Inc. v. Sylvania Shoe Mfg. Corp., 15 F.3d 1222, 1228 (1st Cir.1994). As long as the factual bases essential to the court’s special findings are reasonably discernible from the record, the dictates of Rule 52(a) are met. Id. (noting that the “ ‘judge need only make brief, definite, pertinent findings ... there is no necessity for over-elaboration of detail’ ”) (citation omitted). Contrary to Keller’s contention, the district court did not begin and end its analysis with the observation that Bijhou-wer’s testimony was “more persuasive,” but expressed one very important rationale for so finding: Bijhouwer was the only expert witness who based his opinion on “applicable [maritime] safety standards” and on the possible consequences any “deviations” from those standards might have upon worker safety. Further, the court proceeded to point out that Keller had produced no competent evidence that the Tank 4 ladder was defective in any way. These “special findings” met the Rule 52(a) requirements.

Keller next argues that the trial court’s findings (e.g., that the ladder design was “generally safe,” or its hazardous features, if any, should have been obvious to the stevedore’s employees) were based upon inherently unreliable or inadmissible evidence, or its refusal to admit or consider competent evidence entitled to greater weight. Whether the defendant breached a duty of care is a question of fact, which we review only for clear error. See Fed.R.Civ.P. 52(a); Martinez v. Korea Shipping Corp., 903 F.2d 606, 609 (9th Cir.1990); Miller v. Patton-Tully Transp. Co., 851 F.2d 202, 205 (8th Cir.1988). Clear error review presupposes appellate deference to trial court findings of fact unless we are left with the “definite and firm conviction that a mistake has been committed.” Holmes Transp., Inc., 983 F.2d at 1129. Particular deference is due trial court findings dependent on witness credibility, see DesRosiers v. Moran, 949 F.2d 15, 19 (1st Cir.1991), to the degree that error is seldom considered “clear” unless the credibility assessments were based on testimony which was inherently implausible, internally inconsistent, or critically impeached. See Anderson v. City of Bessemer City, 470 U.S. 564, 575, 105 S.Ct. 1504, 1512, 84 L.Ed.2d 518 (1985); Rivera-Gomez v. de Castro, 900 F.2d 1, 4 (1st Cir.1990).

Under LHWCA § 905(b), the plaintiff must prove, by a preponderance of the evidence, both proximate causation and a breach of the applicable duty of care. See Bjaranson v. Botelho Shipping Corp., 873 F.2d 1204, 1208 (9th Cir.1989); Biggs v. Logicon, Inc., 663 F.2d 52, 53-54 (8th Cir.1981). Since actionable negligence under the LHWCA depends on the fluid concept of “reasonableness” in the circumstances, the LHWCA provides little substantive guidance on vessel-owner conduct violative of the various duties of care. See Scindia, 451 U.S. at 165-66,101 S.Ct. at 1621 (“Section 905(b) did not specify the acts or omissions of the vessel that would constitute negligence.... Much was left to be resolved through the ‘application of accepted principles of tort law and the ordinary process of litigation.’”) (citation omitted). Generally speaking, the fact-finder should assess the “reasonableness” of the vessel owner’s conduct “by balancing the usefulness to the [vessel] of the [allegedly] dangerous condition and the burden involved in. curing it against the probability and severity of the harm it poses.” Johnson, 613 F.2d at 348 (emphasis added); see also Miller, 851 F.2d at 205 (same). And, even though “proof of [the vessel owner’s] adherence to an industry practice or custom is not dispositive on the issue of negligence,” Martinez, 903 F.2d at 610 (citations omitted) (emphasis added), often the plaintiffs case will “depend on the existence of statutes, regulations and customs allocating responsibility for repairs of defective equipment [between the owner and stevedore],” since these sources are probative of the risks a “reasonably competent” stevedore should anticipate and manage. See 1A Benedict on Admiralty § 94, at 5-25 (emphasis added); see also, e.g., Martinez, 903 F.2d at 609 (noting, on review of summary judgment, that “[vessel owner] ... submitted the affidavits of a licensed ship master and a naval architect, who claimed that the platform is standard in the industry and meets international requirements”).

Keller challenges the cornerstone finding by the district court: that Bijhouwer’s expert opinion was founded on a “persuasive” appraisal of “applicable” industry standards. The gist of Bijhouwer’s testimony was that he personally inspected the Tank 4 ladder after Eeller’s fall, measured its dimensions, and climbed out of Tank 4 several times by pulling himself under the lower railing with the aid of the metal grab bar mounted in the ’tween deck floor. In twenty-four years as a marine surveyor, approximately five to ten percent of the vessels Bijhouwer had encountered were equipped with ladder-railing configurations similar to Tank 4. Bijhou-wer found the Tank 4 ladder “easy” to climb, and “perfectly safe.” He consulted two fixed-ladder safety standards governing “shipboard installation as opposed to land-based installation”: the Maritime Administration standard (MARAD) (1965) and the American Society for Testing and Materials standard (ASTM) (1983). In Bijhouwer’s opinion, both standards confirmed that the Tank 4 ladder-railing design met or surpassed applicable maritime safety standards.

Finding no merit in Keller’s other challenges to the district court’s credibility determinations, we focus on two related contentions. First, Keller quarrels with the district court ruling that ASTM was an “applicable” industry standard. He points out that the ASTM was promulgated several years after Keller’s fall, for the purpose of facilitating inter-vessel exchangeability of component parts, rather than promoting safety concerns. And, because Bijhouwer conceded at trial that MARAD required an unobstructed gap in the Tank 4 railing, Keller contests the district court ruling that MARAD was an “applicable” industry standard and disagrees that the Tank 4 ladder substantially conformed with the MARAD design.

These contentions cannot withstand scrutiny. Keller does not explain why a maritime safety standard like ASTM would be wholly “inapplicable” .simply because it had been promulgated after the accident. In this context, “applicability” connotes no statutory or regulatory compulsion to conform with a particular standard. See infra note 5. Rather, “applicability” connotes mere relevance: that ASTM had some tendency to make it more or less likely that the defendant and Simplex would have regarded the ASTM norm as a minimum safety standard for the industry. There is no evidence that general maritime safety standards changed so dramatically between 1979 and 1983 that ASTM was rendered wholly immaterial as an indicator of 1979 industry safety practices, see Fed. R.Evid. 401, nor that ASTM was based exclusively on post-1979 data. Further, in response to Keller’s contention that ASTM’s purpose was merely to facilitate the interchangeability of component parts, we note Bijhouwer’s testimony that though the maritime standards he relied upon (including• ASTM) might not be exclusively safety-oriented, there were “safety-related aspects to all of [these industry] standards.” Thus, it was not clear error to find that ASTM possessed some probative value in determining industry safety practices in 1979.

Even if ASTM were deemed wholly “inapplicable,” however, it was but one of two independent maritime safety standards on which Bijhouwer relied. Keller therefore would have had to hobble both the ASTM and the MARAD standards in order to prevail. Viewed as an enumeration of minimum safety recommendations for the industry, MARAD is conspicuously silent on many matters Keller considered pertinent to the defendant vessel owner’s duty of care, including any unequivocal recommendation that a gap be left in safety railings which extend around the top of a fixed ladder. Bijhouwer testified that MARAD recommended such a gap (or removable railings) only as needed to facilitate cargo loading via the deck on which the railings are located. Here, of course, the cable was not loaded into Tank 4 across the HUDDELL’s ’tween deck where the safety railings were located, but from the main deck, down through an upper hatch and into Tank 4. He further testified that MARAD recommends such an “access opening” only in “deck” railings near ladders, citing two plausible reasons that this would not indicate that a complete gap should have been left in the Tank 4 railings: (1) the MARAD provision refers exclusively to railings on the periphery of the main or weather deck of the vessel, not to railings on lower decks, like the ’tween deck; and (2) the undefined term “access opening” might reasonably mean any aperture through which a person could exit safely, such as the 27-ineh space under the lower railing on Tank 4. Bijhouwer’s testimony likewise was bolstered by OSHA regulations, which presumably impose a heightened obligation on the stevedore to provide its employees with a “safe” workplace. See 33 U.S.C. § 941. Yet even the OSHA standards do not discourage the ladder configuration found on Tank 4. See 29 C.F.R. § 1918.25. Thus, Keller failed to weaken Bijhouwer’s interpretation and application of MARAD.

To the extent that the technical aspects of’MARAD invited expert interpretation, the district court was entitled to rely on Bijhouwer’s testimony, especially since Keller tendered no persuasive counter-interpretation:

Compliance with the customs and practice of an industry, while relevant and admissible[,] is not necessarily due care. It may, however, be evidence of due care and when relied on by the fact finder “his findings will not be lightly disregarded unless there is a particularly strong showing of the unreasonableness of the customary practice.”

1 Martin J. Norris, The Law of Maritime Personal Injuries § 9:5, at 453 (4th ed. 1990) (quoting Cia Maritima Del Nervion v. James J. Flanagan Shipping Corp., 308 F.2d 120, 125 (5th Cir.1962) (emphasis added)); McGann v. Compania De Navegacio Maritima Netumar, 586 F.Supp. 1568, 1571 (D.Md.1984) (evidence that ladder was “typical” or “standard” is probative of vessel owner’s nonnegligent conduct). Van Dissell, Keller’s expert witness, conceded that he never consulted the ASTM standards, and neither referenced nor analyzed MARAD before surveying the Tank 4 ladder. We think it clear that this effort fell well short of the “particularly strong showing,” see Cia Marítima Del Nervion, 308 F.2d at 125 (emphasis added), needed to demonstrate clear error in the trial court’s decision to credit Bijhouwer’s expert recommendations relating to an “applicable” industry “standard.”

Keller concedes that van Dissell relied on three land-based safety standards, or at least on safety standards not intended for applications distinctively maritime in nature: Department of Defense Military Standard Human Engineering Design Criteria for Military Systems, Equipment and Facilities, MIL-STD-1472 (1970); American National Standards Institute’s (ANSI) Standard Safety Code for Fixed Ladders (1956 & 1974); and OSHA Standards for Fixed Ladders, 29 C.F.R. § 1910.27 (1975). In general, differentials between land-based and maritime design and safety codes are necessitated by the unique spatial and weight constraints on working maritime vessels. The van Dissell benchmarks undoubtedly set more stringent safety specifications than the MARAD model, and thus were relatively “safer,” but Scin-dia inquires only whether Simplex could have anticipated that the vessel owner would consign a vessel with these heightened land-based safety specifications. By contrast, Bijhouwer testified that shipyards commonly consult standards, such as MARAD, in designing and constructing merchant vessels; rather than the more generalized military specifications like MIL-STD-1472; and, further, that he had encountered the Tank 4 ladder configuration in at least five to ten percent of the merchant vessels he had surveyed.

Second, Keller attacks, as internally inconsistent and inherently implausible, the Bijhouwer testimony that the 27-inch space beneath the lower safety railing on Tank 4 afforded an adequate “access opening” according to MARAD. Bijhouwer testified on deposition that a minimum vertical gap of twenty-five inches beneath the lower railing would be a “safe” “access opening” for exiting Tank 4. At trial, however, Bijhouwer conceded that the grab bar, which was 4¿é inches high, was set into the ’tween deck floor six inches from the ladder and the rim of Tank 4. Confronted with this configuration — indicating an actual clearance of 22% inches — Bijhouwer nonetheless stated that the grab bar posed no hazardous interference. He explained that there would remain at least a 26-inch clearance directly beneath the lower railing where it passed over the six-inch ledge of the tank, and that this clearance was needed only to accommodate the height of the climber’s body as he placed his knee up onto the tank ledge. In that position, the climber would attain maximum vertical posture (measured from stooped head/shoulders to knee), at which point his body would flatten out to less than twenty-five inches as he pulled himself forward and through the narrower opening between the top of the grab bar and the lower railing. While Keller characterizes these movements as dangerously acrobatic, it is well recognized that longshore workers are called upon to cope with uncomfortable, cramped positions in the close confines of a vessel. See, e.g., Bjaranson, 873 F.2d at 1208 (“the men, according to the testimony, could have squeezed around the leg of the crane” to avoid the hazard) (emphasis added). Further, Bijhouwer testified that the lower railing served both (i) a safety function, since it would protect an exiting climber from falling backward into the tank, and (n) a utilitarian purpose, since it would provide Simplex with the option to spool wire into Tank 4 above the ’tween deck level. See Johnson, 613 F.2d at 348 (trier of fact may consider “the usefulness to the [vessel] of the [allegedly] dangerous condition”) (emphasis added); see also Miller, 851 F.2d at 205 (“The court found that the toolbox was a necessary piece of equipment for the barge and that it was situated reasonably to keep it out of the way of the workers on the barge.... Similarly, the court found that whatever hazard was presented by the counterweight was justified by its important safety purpose of keeping the toolbox lid from snapping shut unexpectedly.”) (emphasis added).

According to Bijhouwer, therefore, the Tank 4 ladder incorporated at least one “safe” method of egress compatible with MARAD (i.e., “under” the lower safety railing); hence, the vessel owner had not provided Simplex with an “unavoidably” hazardous ladder. See Teply, 859 F.2d at 378. Thus, even if MARAD had been the only “applicable” industry standard on which Bijhouwer could rely, it afforded sufficient support for the district court finding that the defendant vessel owner had discharged its turnover duty of safe condition, on the ground that Simplex should have “anticipated” and managed the equipment as designed, whatever its inherent, but avoidable, risks.

Keller further contends that the trial court erred in finding that any potential risks attending the use of the Tank 4 ladder were “obvious.” He relies on (i) Bijhouwer’s testimony that it would be “reckless” for Simplex employees to attempt to exit Tank 4 by passing between the two safety railings or “over” the top railing, and (ii) evidence that Simplex employees continued to use both these methods after turnover. Keller argues that this latent design “defect” generated the independent turnover duty that the vessel owner warn Simplex or its longshore workers of the hidden danger. This contention, too, is flawed.

First, Keller incorrectly assumes that by adopting Bijhouwer’s testimony that MAR-AD and ASTM were “applicable” safety standards, the trial court likewise necessarily credited Bijhouwer’s expert opinion (not based on MARAD) that it would have been reckless to utilize the two other methods of egress. On the contrary, however, the court did not adopt that portion of the Bijhouwer testimony but went on to note instead that Keller had proffered no evidence of any design defect whatsoever in the Tank 4 ladder; for example, that any accident had ever occurred on the ladder when persons other than Keller used these two alternate methods under substantially similar conditions (wet, cold, artificial lighting). See, e.g., McKinnon v. Skil Corp., 638 F.2d 270, 277 (1st Cir.1981) (subject to Rule 403 balancing, evidence of prior accidents under similar conditions admissible to show design defect); cf. Martinez, 903 F.2d at 609 (at summary judgment, vessel owner met burden by “offer[ing] evi-denee that during the vessel’s seven years of operation no longshoreman ever fell into one of the ladder openings on the lashing platforms and no complaints were lodged concerning the platforms”); McGann, 586 F.Supp. at 1571 (“[N]o other accidents or complaints concerning this type of ladder have been reported....”); accord Pittman v. Littlefield, 438 F.2d 659, 662 (1st Cir.1971) (absence of other accidents under substantially similar conditions may be probative of “safe” condition) (applying blew Hampshire law).

Second, even if the district court had agreed with Bijhouwer’s assessment of the risks attending the two alternate methods of egress, Bijhouwer never intimated that those methods posed hazards not readily foreseeable by Simplex. Scindia, 451 U.S. at 167, 101 S.Ct. at 1622 (noting that duty to warn exists only if “defect” “would not be obvious to or anticipated by [stevedore] if reasonably competent in the performance of his work”). The alleged design defect (two fixed railings) was in no sense latent. Unlike a hairline fracture in the rung of a ladder, for example, which might render the ladder configuration not reasonably safe for any unwarned usage, the juxtaposition of the two railings and the absence of posted instructions put Simplex on notice that its employees, unless instructed otherwise, might attempt to exit Tank 4 in any of three ways. If Simplex had deemed Bijhouwer’s “under” method the only “safe” one, it could have instructed its employees not to use the two alternate methods. Or if it considered all three methods “unsafe,” it could have removed the railings between the stanchions at the top of the ladder.

Relying on the fact that he was never in Tank 4 prior to the night of the accident, Keller wrongly presumes that obviousness and latency are measured by what a relatively inexperienced longshore worker might observe. Instead, the Scindia standard turns primarily on what an “experienced” stevedore, like Simplex, reasonably would be expected to notice. By the same token, if the district court correctly found that even Simplex longshore workers reasonably could be expected to recognize any such defects, it surely follows that their more experienced stevedore-employer should have discovered the defects during the course of its extended two-year stewardship of the HUDDELL. See Bjaranson, 873 F.2d at 1209 n. 7 (“The condition of the ladder was apparent and obvious when Bjaranson’s employer, the ste-vedoring contractor, boarded the ship and assumed the control of the cargo operation. Although the condition may not have been obvious to Bjaranson at night, the fact that the condition was obvious to his employer eliminated whatever duty there may have been upon [the vessel owner] to warn the individual employees.”) (emphasis added).

Next, Keller contends that the district court improperly considered his blood-alcohol level at the time of the accident, since the doctrine of pure comparative fault would not permit contributory negligence to defeat Keller’s LHWCA claim, but only to abate damages. See Johnson, 613 F.2d at 347; 1A Benedict on Admiralty § 56, at 3-33. First, the district court explicitly acknowledged that had Keller proven that the defendant vessel owner was a cause of Keller’s accident, the court could not have treated Keller’s blood-alcohol level as a total bar to recovery under the LHWCA. See Keller, No. 81-549-SD, slip op. at 15 (“The court is, of course, aware that were negligence found on the part of the ship owner, the intoxication of Keller ... would not serve necessarily to totally disqualify him from recovery.”) (emphasis added). Second, under the analogous comparative fault doctrine for LHWCA compensation awards, a stevedore may defend by proving that the longshore worker’s injuries were caused “solely” by his intoxication, cf 33 U.S.C. § 903(c). While the longshore worker initially enjoys a rebuttable presumption against such a finding, id. § 920(c), the stevedore’s defense is not unprovable. See, e.g., Walker v. Universal Terminal & Stevedoring Corp., 645 F.2d 170, 173 (3d Cir.1981) (finding § 903(c) intoxication defense established, and noting that the rebuttable presumption “falls out of the case” once stevedore proffers “substantial evidence” that longshore worker’s intoxication was sole cause of injury or death).

Similarly, in a section 905(b) action, the trial court may assess the quality of the vessel owner’s rebuttal evidence where the longshore worker failed to demonstrate a vessel “defect” and where the vessel owner has proffered “substantial” evidence of the longshore worker’s intoxication. Here, the trial court’s consideration of the blood-alcohol level followed directly upon its observations concerning Keller’s failures of proof: (1) the absence of persuasive expert testimony that the Tank 4 ladder design was so inferior to anticipated safety standards that the defendant vessel owner could not entrust the equipment to the stevedore’s able charge; and (2) the absence of evidence of other accidents on the ladder under substantially similar conditions. In this context, we interpret these trial court observations as an acknowledgment not only that Keller utterly failed to carry his burden of proof but that the only credible evidence of possible causation (i.e., Keller’s heavy drinking earlier in the evening and his high blood-alcohol level one hour after the fall) in no respect implicated the defendant vessel owner. See supra note 8.

Keller further claims that but for two items of evidence which the district court improperly ignored or excluded, we would be compelled to conclude that the district court committed clear error. First, the district court excluded the deposition testimony of eyewitness Rhonda Rossley, who expressed the opinion that Keller had hit his head on a railing prior to the fall. Nonexpert-opinion testimony is permitted only if “(a) rationally based on the perception of the witness and (b) helpful to a clear understanding of the witness’ testimony or the determination of the fact in issue.” Fed.R.Evid. 701. See Swajian v. General Motors Corp., 916 F.2d 31, 36 (1st Cir.1990). The trial court ruled that the proffered deposition testimony did not meet the first Rule 701 test because Rossley “did not see [Keller] strike his head, nor could she see his right hand before he fell[, nor] observe whether his left hand or his left foot first lost contact with, respectively, the railing or the ladder rung.” Keller, No. 81-549-SD, slip op. at 12.

We review a Rule 701 ruling only for manifest abuse of discretion. See United States v. Paiva, 892 F.2d 148, 156 (1st Cir.1989). We find no abuse of discretion. First, Ross-ley’s opinion necessarily depended upon a forbidden Rule 701 “inference,” because she (i) neither saw Keller strike his head on the railing, (ii) nor testified to any other sensory perception from which one might rationally infer such an impact {e.g., the sound of impact, a sudden jolt or halt in Keller’s upward progress, a pre- or post-impact cry, or any outward appearance of a head wound or bleeding). Cf. Swajian, 916 F.2d at 36 (finding clear abuse of discretion in allowing lay opinion that wheel fell off rear axle before car flipped over, based exclusively on the witness’s observation that he first saw wheel crossing the road while the flip-over was in progress). Although Keller’s failure to call out or to try to regain hold of the ladder could be consistent with sudden disorientation or even unconsciousness, as a lay witness Rossley would have had no nonspeeula-tive basis for excluding possible causes other than a blow to the head (e.g., intoxication, fatigue and heavy exertion).

Second, and perhaps more importantly, this was a bench trial, in which the trial judge would not only determine the admissibility of the evidence but serve as the ultimate trier of fact. The Rule 701 admissibility determination turns on whether the inference drawn by the nonexpert lay witness would be “helpful to ... the determination of the fact in issue.” Thus, having considered the entire proffer, the trial judge excluded the Rossley opinion testimony because the court found no sufficiently reliable basis for the speculative inference on which it was based. Not only do we agree, but nothing would have required the trial judge, as trier of fact, to credit the Rossley opinion had it been admitted in evidence, especially since she possessed no particular skill or experience which would have assisted the trial court’s fact-finding insight. Cf., e.g., Soden v. Freightliner Corp., 714 F.2d 498, 512 (5th Cir.1983) (nonexpert witness with eighteen years’ experience repairing trucks can give lay opinion whether truck was defective).

Finally, Keller contests the exclusion of evidence that Simplex cut out the two railings on the Tank 4 ladder one day after the accident, as proof that the original ladder design constituted an “unreasonably” dangerous condition. Keller suggests that this evidence was admissible notwithstanding Rule 407, which requires the exclusion of subsequent remedial repairs by the defendant only, not by nondefendants like Simplex. See Raymond v. Raymond Corp., 938 F.2d 1518, 1524 (1st Cir.1991); Koonce v. Quaker Safety Prods. & Mfg. Co., 798 F.2d 700, 719-20 (5th Cir.1986).

At best, subsequent remedial measures are considered marginally probative of prior negligence. See John H. Wigmore, Evidence § 283, at 174-75 (1979). In this case, moreover, defendant could have capitalized on the very same evidence to demonstrate that Simplex was expected to make such structural alterations to the HUDDELL without first consulting defendant, and that defendant was entitled to rely on Simplex, as a reasonably competent stevedore, to take such preemptive measures provided Simplex deemed them necessary for its employees’ safety. See also infra note 11. Under the Scindia delineation of turnover duty, therefore, this evidence was at least a “wash” for Keller, and actually may have helped defendant more than Keller. For these reasons, we conclude that the exclusion of this evidence was at most harmless. See Fed.R.Civ.P. 61 (erroneous exclusion of evidence harmless if it “does not affect the substantial rights of the parties”).

2. Post-Turnover Duties of Intervention

Leaving no ground unturned, Keller argues that the court erred in ruling that the defendant did not breach its post-turnover duties: to supervise and inspect the HUD-DELL during cable loading and to intervene and remedy any hazardous condition that developed following turnover. See Scindia, 451 U.S. at 172, 101 S.Ct. at 1624-25 (noting that post-turnover duty to intervene to remedy unreasonably dangerous condition may derive from custom or from the vessel owner’s contractual obligation to the stevedore). Keller contends that the court (1) disregarded his claim that the contract with Simplex required the defendant vessel owner to intervene to effect any safety-related alterations during cargo operations; (2) ignored Keller’s evidence that it was a customary or established practice that the defendant monitor the HUDDELL during loading operations; and (3) erred as a matter of law in determining that “a custom-generated duty to supervise and inspect does not transfer to the ship owner a duty to eradicate dangers reasonably known to and managed by the stevedore.” Keller, No. 81-549-SD, slip op. at 14 (citing LaMartina v. Pan Ocean Shipping Co., Ltd., 815 F.Supp. 878, 880-81 (D.Md.1992)).

A vessel owner’s duty of care normally ceases once it has discharged its “turnover” duties and the stevedore-employer’s cargo operations have begun. Nonetheless, the Supreme Court has suggested three settings in which an owner might remain under some “continuing” duty to monitor, supervise, or inspect the vessel for hazards developing after stevedoring operations commence. First, the vessel owner might remain under such a duty were it to retain actual physical control or custody of a portion of the vessel, or participate in stevedoring operations. Scin-dia, 451 U.S. at 167, 101 S.Ct. at 1622. Keller concedes that these conditions were not met. Second, a duty to intervene might attach in the event the vessel owner were to acquire actual knowledge that “unsafe conditions” had developed in the vessel’s appurtenances since turnover, that the stevedore-employer will not address the unsafe condition, and that the stevedore’s decision not to remedy the developing hazard was “obviously improvident” in the circumstances. Id. at 174-75, 101 S.Ct. at 1625-26. Third, even absent actual control, participation or knowledge, a post-“turnover” duty may arise if the vessel owner was obligated, by contract, statute or custom, to monitor stevedoring operations for the purpose of detecting and remedying unsafe conditions. Id. at 172,101 S.Ct. at 1624-25.

Keller’s “continuing duty” claim was founded on the contention that the defendant vessel owner had either actual or constructive knowledge of an unreasonably dangerous condition during cable loading operations. However, he does not suggest that the basic structure or design of the Tank 4 ladder changed after cable loading began (e.g., ladder rungs displaced, loosened or fractured). Therefore, the defendant could have breached no continuing duty of care to Keller, since the district court supportably found that the Tank 4 ladder configuration created no “unreasonable” hazard ab initio. See Scindia, 451 U.S. at 172, 101 S.Ct. at 1624-25 (“We are of the view that ... the shipowner has no general duty by way of supervision or inspection to exercise reasonable care to discover dangerous conditions that develop [i.e., a malfunctioning winch] within the confines of the cargo operations that are assigned to the stevedore.”); Martinez, 903 F.2d at 611 (“[T]he alleged unsafe condition [employees working on “unsafe” platform] did not develop during cargo operations; it was either safe or unsafe at the time the cargo operations began....”); Pluyer v. Mitsui O.S.K Lines, Ltd., 664 F.2d 1243, 1246 (5th Cir.1982) (noting “different situation” than in Scindia where the “case involves the vessel’s liability for hazards that antedate or are coincident with the commencement of cargo operations”).

Keller intimates that the relevant “change” or “development” which would have been discovered had defendant met its alleged continuing duty to monitor and intervene was the failure of Simplex cable loaders to use the Tank 4 ladder in the intended manner. Thus, Keller would interpret the district court ruling — that “a custom-generated duty to supervise and inspect does not transfer to the ship owner a duty to eradicate dangers reasonably known to and managed by the stevedore” — as holding that a vessel owner can never be duty-bound to intervene once an on-board danger (the risk that longshore workers might resort to the “over” and “between” methods of egress) becomes “obvious” to the stevedore.

We cannot subscribe to Keller’s reasoning. First, as already noted, we discern no indication that the trial court credited evidence that the two alternate methods of exiting Tank 4 were not reasonably safe. Second, even if the district court had found these other methods of egress “unsafe,” initially the vessel owner could rely on Simplex to manage such “obvious” defects, unless and until it appeared that Simplex’s decision not to take remedial measures (warnings or railing removal) was “obviously improvident” under the circumstances. Keller conceded, however, that Simplex, which plainly had actual or constructive notice as to how its long-shore workers were exiting Tank 4, never received an employee complaint about the Tank 4 ladder and that no accident ever occurred on the ladder either before or after the Keller incident. Thus, evidence presented by Keller did not begin to establish defendant’s actual knowledge of the alleged “hazard” on the part of the defendant vessel owner, let alone any obvious improvidence on the part of Simplex. For the same reason, even if the defendant vessel owner had been under a contractual or custom-generated duty to monitor and intervene, Keller failed to establish a breach.

Ill

CONCLUSION

Given the exacting standards of care incumbent upon a stevedore under the LHWCA, and the supportable trial court findings, we are left with nothing approaching a “definite and firm conviction that a mistake has been committed.” Holmes Transp., Inc., 983 F.2d at 1129. Once the trier of fact determined that the Tank 4 ladder was “safe,” its design compatible with “applicable” maritime safety standards, and any potential hazards sufficiently “obvious” to Simplex longshore workers, it followed inexorably that the vessel owner was entitled to rely on Simplex, as an “expert and experienced” stevedore, to act with reasonable care in supervising its workers in their interaction with and avoidance of any such “obvious” hazards on board the vessel during cargo loading operations. Any relevant “hazard” could have been averted by Simplex in various ways, including the permanent removal of the safety railings at the top of the Tank 4 ladder, a warning on the ladder as to safe methods of egress, or simple instruction of its longshore workers.

The judgment is affirmed. The parties shall bear their own costs. 
      
      . Among other things, Keller alleged that (1) the ladder rungs were wet, slippery, worn, and irregularly spaced; (2) the metal railings protruded so as to make it likely that a climber would strike his head; and (3) no warning of these protrusions was posted on the ladder.
     
      
      . Section 905(b) provides in pertinent part:
      In the event of injury to a person covered under this Act caused by the negligence of a vessel, then such person ... may bring an action against such vessel as a third party ..., and the employer shall not be liable to the vessel for such damages directly or indirectly and any agreements or warranties to the contrary shall be void.... The liability of the vessel under this subsection shall not be based upon the warranty of seaworthiness or a breach thereof at the time the injury occurred.
      33 U.S.C. § 905(b).
     
      
      . Minor measurement "deviations” between MARAD-ASTM and Tank 4 included, inter alia: the facial width of ladder rungs (slightly over 14 inches; standard 14 inches); rungs (1% inches by % inch; standard % inch by % inch); and toe clearance behind rungs (5 inches at sides, 14% inches in middle; standard minimum 5 inches).
     
      
      . For example, Bijhouwer testified that a person who was exiting Tank 4 for the first time might be able to do so “blindfolded.” Keller characterizes this testimony as patently incredible, especially in view of other testimony that Tank 4 was "more difficult” to exit than the tanks on other vessels (e.g., the FURMAN) then moored at Simplex. On redirect, however, Bijhouwer clarified that the ladder and grab bar combination installed in Tank 4 was so well designed that, after one trip up, a climber could use it "blindfolded.” Bijhouwer's redirect testimony would enable a reasonable inference that Simplex, once it became acquainted with the Tank 4 configuration following turnover, was in no sense disabled from informing its employees about at least one safe method of exiting the tank. Moreover, the fact that other witnesses testified that the Tank 4 ladder was "more” difficult to climb did not compel a finding that it was defective, since (1) these lay witnesses testified to their personal experiences only, not to safety design; and (2) this inapposite comparison (i.e., “more difficult" as opposed to "too difficult”) would not show that the Tank 4 ladder was "unsafe,” only that other Navy ships moored at Simplex had "safer” ladders (i.e.; exceeded applicable maritime safety standards).
     
      
      . Keller did not contend that these OSHA standards directly applied to defendant. Therefore, even a failure to comply with the OSHA standards would not entitle Keller to claim negligence per se. And in fact, the OSHA standards were not directly applicable to defendant, because (1) they do not pertain to maritime employment of longshore and harbor workers, cf. 33 U.S.C. § 941; 29 C.F.R. §§ 1918.1-1918.106; and (2) they regulate only the obligations of employers, see Martinez, 903 F.2d at 611; Bandeen v. United Carriers (Panama), Inc., 712 F.2d 1336, 1339-40 (9th Cir.1983) (same), and defendant was not Keller’s employer.
     
      
      . Keller argues that the method of egress endorsed by Bijhouwer was unmanageable because the climber would have to place his knee on a narrow coaming that raised % inches at the edge of the tank, which Bijhouwer conceded would "cut" into the climber's knee. In fact, however, Bijhouwer testified that a climber could place his knee "momentarily” between the coaming and the grab bar, not on top of the coaming. When asked if the coaming would then "dig[ ] into your knee," Bijhouwer simply responded that “[y]ou can feel the coaming.”
     
      
      . Keller likewise relies on Bijhouwer’s admission that at the time he first formulated his opinion that the ladder design was safe, he had not considered the actual conditions (e.g., wet, cold, artificial lighting) in Tank 4 on the night of the accident. Nevertheless, when asked at trial, Bijhouwer testified that those conditions did not alter his opinion as to the safety of the ladder design. He explained, for example, that even though Keller was wearing heavy clothing at the time, the clearance beneath the lower safety railing would be adequate for a climber emerging from the tank, because clothing might catch on the railing only as a climber was backing into the tank, not as he was pushing forward.
     
      
      . Given the Scindia standard, evidence of Keller's high blood-alcohol level cannot be wholly divorced from the threshold question whether a defective design rendered the Tank 4 ladder "unreasonably” dangerous. A written policy forbade Simplex workers from reporting to work intoxicated. Thus, Keller’s blood-alcohol level would be relevant to whether the ladder constituted an "unreasonably” dangerous condition, since the vessel owner, in turning over the Tank 4 ladder, reasonably could rely on compliance with the stevedore’s policy on intoxication. See Johnson, 613 F.2d at 348 (trier of fact must consider “the probability and severity of the harm [the condition] poses”).
     
      
      . Although a medical doctor testified that Keller sustained an eye injury which could have been consistent with the Rossley inference, given that Keller also suffered head trauma when he landed head-first on the tank floor sixteen feet below the 'tween deck the doctor could not testify that such an inference was compelled.
     
      
      . Keller catalogues various documentary exhibits which he contends were improperly excluded. We find no error. For example, Exhibits 10, 21, and 65 were proffered to establish the contents of the contract between Simplex and defendant. This issue was mooted by the finding that the Tank 4 ladder did not constitute an unreasonably dangerous condition. See infra Section II.B.2 & note 11. Exhibits 34 and 34A were largely cumulative of evidence already admitted and any noncumulative portions were provided in the van Dissell testimony. See Fed.R.Civ.P. 61 (harmless error); Fed.R.Evid. 403 (governing admission of "cumulative” evidence). Finally, Exhibit 73 — a mock-up of a portion of the Tank 4 ladder, used for demonstrative purposes at trial — was excludable due to failure to lay a proper foundation for es admission. See Rogers v. Raymark Indus., Inc., 922 F.2d 1426, 1429 (9th Cir.1991) (admission of demonstrative evidence entrusted to trial court discretion). At trial, Bijhouwer challenged the accuracy of the van Dissell measurements upon which Exhibit 73 was predicated. See United States v. Myers, 972 F.2d 1566, 1579 (11th Cir.1992) (noting that admission turns on whether there is foundation testimony that demonstrative evidence is "fair" and "accurate” depiction of original), cert. denied,-U.S.-, 113 S.Ct. 1813, 123 L.Ed.2d 445 (1993); Nichols Constr. Corp v. Cessna Aircraft Co., 808 F.2d 340, 353 (5th Cir.1985) (same). Finally, relevant portions of Exhibits 91 and 91A were read into the trial record. See Fed.R.Civ.P. 61; Fed.R.Evid. 403.
     
      
      . Keller argues that the contract between defendant and Simplex unambiguously provided that defendant, not Simplex, would bear primary responsibility for ongoing "safety” inspections and modifications to the HUDDELL's work areas following turnover. Keller points to a contract provision barring Simplex from making unilateral structural alterations to the HUDDELL. From this premise, he contends that Simplex was compelled to use the Tank 4 ladder in existence at turnover. We do not agree. First, contrary to the trial court's alternate finding, this argument presumes that the ladder was "unsafe.” Second, the contract contemplated that Simplex would bear the primary role in determining whether modifications were needed, even if defendant was to be consulted before “major” modifications were undertaken. In any event, this contention falls far short of demonstrating a contractual duty on the part of the vessel owner to monitor in the first instance.
      
     