The importance of inspecting the substructures of bridges spanning waterways and waterfront facilities during the development of maintenance programs or prior to preparing rehabilitation or repair designs is often overlooked by public officials and engineering consultants who are ultimately responsible for overseeing such activities.

By its very nature, the substructure of a marine facility is frequently hidden from view since most of the structural elements comprising it are submerged. Therefore, to assess the actual condition of structural members situated below the waterline generally requires the services of divers who possess a basic knowledge of the effects of deterioration on the safe load-bearing capacity of a marine-based structure.

However, because submerged components remain visually covert, there is a widespread tendency to allocate relatively low budgets toward inspection of these items within the overall scheme of facility maintenance. Such a scenario lends credence to the age-old adage, "Out of sight, out of mind." Unfortunately, giving underwater inspection lower priority on the budgetary scale than other tasks has often proved to be disastrous, both in terms of facility maintenance costs and, more importantly, safety.

The Purpose of Underwater Inspection
Underwater inspection has four primary purposes: ensuring public safety, protecting public assets, preventing or reducing facility downtime, and initiating proactive maintenance.

Many structures situated over water are heavily used by the public, particularly bridges, marine terminals, piers, wharves, and relieving platforms. While one can logically argue that ensuring the safety of the public alone warrants the implementation of periodic inspections aimed at preventing catastrophic failure that could lead to casualties, the reality is that such justification is frequently neglected or diminished by key administrators, decision makers, and technical personnel involved with developing budgets for facility maintenance programs.

In fact, the costs associated with underwater inspection are commonly viewed by many facility owners as negligible in comparison to the total maintenance costs. At the heart of this problem are a substantial contingent of consulting engineering firms who provide services to marine facility owners, often establishing unrealistic and dangerous precedents based on misconceptions about the true nature of underwater inspection. Through association with the engineer, such misconceptions are frequently adopted by the owner. This usually results in past improper practices by a predecessor becoming benchmarks for other consultants to follow at the urging of the owner, particularly during price negotiations when previous rates of production and costs are brought into sharp focus, thus proliferating a very risky and perpetual Catch-22, with no end in sight.

Types of Underwater Inspection
Underwater inspections are categorized into six types: Inventory, Routine, Damage, In-depth, Interim, and Construction. Each is intended to accomplish distinct objectives.

Inventory Inspections: These are normally performed following new construction, modifications, or repairs to establish as-built or baseline structural conditions and collect structural inventory and appraisal data. Inventory inspections are often referred to as "baseline inspections" since they generally become the benchmark for assessing the results of all future inspections. Baseline and inventory inspections identify potential structural problems, such as if the facility is scour critical. They are typically conducted on renovated or newly constructed facilities prior to owner acceptance or final payment to the contractor, frequently providing the actual plan, elevations, and section drawings of the structure as opposed to the original design configuration. This type of inspection establishes the time interval for the next inspection.

Routine Inspections: These determine the physical and functional condition of the facility, identifying changes from inventory, baseline, or previously recorded conditions. They are intended to assess the overall condition of the structure by assigning condition assessment ratings to the various facility components. They also ensure that the structure continues to satisfy its current service requirements and can include objectives aimed at quantitatively analyzing both local and global structural capacity as a result of damage or deterioration. Routine inspections should be performed on a cyclical basis and are a proactive approach to maintenance, since deteriorated elements will be detected and remedied before the deficiencies progress to a level that could jeopardize the structural integrity of the facility. Recommendations for future courses of action usually accompany a report of routine inspection findings, including follow-up maintenance or repair activities and the time interval to the next routine or other type of inspection.

The frequency interval between routine inspections varies from one to six years and is a function of material type, age of the structure, service environment, economic importance of the facility, and rate of further anticipated deterioration. National Bridge Inspection Standards (NBIS), however, mandate that the interval for routine inspections of bridges spanning waterways should never exceed five years.

Because of the covert nature of underwater inspection, reports containing diver observations and descriptions of findings on routine underwater inspections are generally accepted at face value. If a critical structural deficiency on a marine substructure goes undetected or is misinterpreted by the inspection diver or team leader supervising the inspection, structural failure may result.

Damage Inspections: Sometimes referred to as post-event inspections, these are typically unscheduled inspections aimed at rapidly assessing the stability of a structure in the aftermath of a significant, potentially damage-causing event and determining whether further attention to the structure is warranted. Such events as floods, earthquakes, vessel impact, high concentrations of corrosive chemicals in the water, tidal waves, major runoff caused by a severe storm, and scouring currents induced by the presence of ice floes or debris build-up may all dictate the need for a damage inspection. The scope of work or level of effort can vary substantially by the type and severity of event, but typically attempt to assess the need for immediate or longer-term repairs and often determine whether load restrictions or closure to traffic should be imposed on the structure. They also may determine the need for a more involved follow-up inspection effort supplemented by testing.

In-depth Inspections: Because in-depth inspections are most often performed to record defects requiring repairs, they are more frequently referred to as "repair design inspections." These are normally scheduled when there is prior evidence of structural distress, typically upon the recommendation made after a routine inspection. Although they have no standard scope of work, they are commonly performed when the salvageability of an existing substructure must be determined for supporting a new or modified superstructure and can include a load rating analysis to calculate the residual capacity of the structural members. However, they are predominately performed to keep existing marine-based structures in continuous service.

This type of inspection generally involves an extensive close-up, Level II hands-on assessment of structural members or those elements that are anticipated to be modified for supporting a new superstructure. It commonly includes a Level III inspection effort involving non-destructive or partially destructive testing of structural components whereby laboratory analysis of extracted material samples are performed.

Although inconclusive results from a routine inspection will frequently dictate the need for an in-depth or repair design inspection, an in-depth inspection may be called for without being preceded by a routine inspection, particularly when the need for repairs is obvious. This frequently occurs following a damage inspection which recommends that an in-depth inspection be conducted using testing techniques. An in-depth inspection also may be combined with a routine inspection, but the distinction between the two is not always clearly defined.

If improperly performed, an in-depth inspection will invariably result in the preparation of poor quality construction plans and specifications since erroneous or incomplete inspection findings will become the basis of the construction documents. Faulty bid documents will ultimately open the door to unanticipated and costly contractor claims and change orders once the work has begun. Thus, the sins or failings of the underwater inspector will eventually reveal themselves to the owner, assuming that the repair work went out for bid within a relatively reasonable time frame following the repair design inspection. If the firm that performed the diving inspection was hired on a low bid basis by the design engineer responsible for preparing the construction plans, then the owner's wrath will ultimately befall the engineer for failing to exercise a professional standard of care.

For Example: A consulting engineering firm prepared repair documents for the rehabilitation of an active, low-level pier facility, showing that 200 out of 5,000 timber piles averaging 25 feet (8m) in exposed length must be posted with treated wood. The posts would average five feet in length, replacing the upper portions of piles damaged by Limnoria, a type of marine borer. The repair plans were based on an in-depth underwater inspection performed by a diving subcontractor selected by the engineer with the owner's approval on a low bid basis. The cost of the underwater investigation equated to 10 percent of the consulting engineer's overall fee to perform the work.

Built in 1933, the pier was constructed during a time when pollution levels were high enough in the harbor where the pier is located to prevent marine borers from thriving. Thus there was no need to treat the wood against biodeterioration caused by borers at the time of construction. However, as pollution levels dropped, Limnoria began to manifest in the timber. This was documented in previous routine inspection reports, which showed some of the supporting piles taking on an hourglass configuration as their load-bearing capacities gradually diminished with advancing section loss. As Limnoria activity increased, pile diameters shrunk.

In assessing whether the facility could still function up to its required load-bearing capacity, the owner hired the engineer to perform a structural analysis on the pier to determine the appropriate repairs necessary to restore the structural capacity of the damaged piles. The engineer developed the scope of work for an in-depth underwater inspection which would provide the information required to perform the analysis and develop the repair designs. Although the scope did not include destructive core sampling of the timber to evaluate covert deterioration occurring within the piles, it did stipulate that penetration tests using an ice-pick in conjunction with hammer strikes had to be performed on 20 percent of the timber piles at five-foot intervals along their lengths in order to assess the soundness of the wood and would include those portions located at the mudline. The engineer also required that minor cleaning of marine growth had to be performed where necessary in order for the inspection diver to carry out the work. According to past inspection reports, the piles were heavily coated with barnacles and other marine organisms.

After initiating the repair work, the marine contractor discovered the substantial Teredo infestation permeating the piles. As it turned out, both types of marine borers, Limnoria and Teredo, were actively destroying the untreated timber comprising the piles identified for posting, with the Teredo actually predominating and being more destructive. The contractor performed a statistical random sampling of the other piles and determined that the damage caused by Teredo was extensive throughout most of the pile population, causing heavy deterioration in at least 3,000 piles. By striking the piles with a hammer near the mudline, the contractor was able to expose cavities in the timber with as much as 75 percent section loss. The contractor also noted that water velocity peaks at 2.5 feet per second during maximum tidal flow, making it extremely difficult to work during these periods.

The contractor informed the owner that concrete encasement rather than posting was the appropriate method of repair and that posting would be a waste of money since it would not restore the severe section loss that would progress in the piles below the planned postings. In fact, the facility was in imminent danger of collapse and should be closed for repair. This was confirmed when the owner hired another consultant to validate the contractor's claim. Ultimately, the owner blamed the original design engineer for failing to note the severity of damage and sued for malpractice.

Interim Inspections: Also called "special inspections," these monitor known or suspected deficiencies that can compromise the structural integrity of a facility and provide more detailed information than normally obtained during a routine or repair design inspection. Evidence of or the potential for such occurrences as differential settlement, migrating scour, marine borer attack, or corrosive environments may dictate the need for an interim or special inspection, although they are often scheduled at the discretion of the facility owner and may commonly require the inspection of only one substructure unit or structural element. Interim or special inspections are typically performed on an exceptional basis as a result of a recommendation made after a routine inspection and generally focus on obtaining information necessary to better understand the nature and extent of deterioration prior to determining the need for and type of repairs that will be appropriate.

For example, measurement of electrical potentials at various points on a steel bulkhead are scheduled to be taken at six month intervals to determine the effectiveness of an existing cathodic protection system. In addition, this type of inspection can be used to estimate the remaining useful life of the structure based on deterioration rates of various material components determined from trends established from previous inspection reports. Core sampling of timber elements suspected of hidden biodeterioration as a result of Teredo or shipworm attack is an example of a destructive testing technique that may be used in performing a special inspection. Where appropriate, this type of inspection is sometimes performed concurrently with a routine inspection or an in-depth inspection. Construction Inspections: Construction inspections essentially fall into two categories: new construction inspections and repair construction inspections. Both are intended as quality control measures to ensure that the work of a contractor is carried out in conformance with construction documents. In addition, they serve to verify repair or installation quantities for contractor payment and to develop a list of deficiencies, or punchlist, for which the contractor is to take corrective action. In general, repair construction inspections should be periodically conducted throughout the repair process, rather than at the conclusion of the project, in order to properly interpret and implement the design intent of the construction or bid documents. Not only do they act as a countermeasure against contractor claims, they help keep the project within the established budget and schedule, often resolving field problems and questions.

The scope and frequency is typically dictated by the type of repairs specified by the construction documents and the repair methods used by the contractor. On more complex projects where there is a sequence of underwater tasks to be performed, some of which would hinder or make impossible the inspection of preceding work items, continuous diving inspections on a daily basis may be warranted in order to stay on top of the contractor's work. Marine construction projects failing to have sufficient and competent underwater inspection will almost always result in poor workmanship by the contractor, costly change orders emanating from unverified contractor claims, or hidden construction defects that may not manifest themselves until years later, ultimately resulting in expensive repairs that sometimes exceed the original project cost.

Unfortunately, there has been an emerging trend in recent years in which the construction documents place the burden of quality control in the hands of the contractor who must make the repairs. This entails subcontracting with an independent party to carry out the construction inspection, with the cost of the inspection services coming out of the contractor's bid price. This is analogous to entrusting the fox with the keys to the chicken coop.

Levels of Inspection and Diver Production Rates
Certain inspection types, such as routine and in-depth, focus on the investigation of a statistically representative sample of underwater elements comprising a waterfront or bridge substructure by using a particular effort level of inspection on a percentage of those elements that will adequately define the sample. Three levels of underwater inspection are recognized by both the American Society of Civil Engineers (ASCE) and NBIS.

Level I: This entails a visual or tactile inspection of the entire exposed exterior surface of all accessible submerged components without the removal of marine growth. Commonly known as a "swim-by" inspection effort, it has the dual objective of confirming the as-built condition of a structure and detecting obvious major damage and other glaring deficiencies that could compromise the integrity of the structure, such as discontinuity of structural elements and undermining or exposure of normally buried components. Typically, a Level I effort is conducted on 100 percent of all exposed and accessible components comprising a substructure situated below the waterline. Photographic documentation is often used to record typical and atypical findings. In addition, this level of effort will determine which elements, if any, are to receive a Level II or Level III inspection.

Production rates for inspecting various types of structural elements will vary widely under this level of effort. For instance, as a general rule of thumb, with fairly good underwater visibility (i.e., eight feet or greater) and little or no current, an experienced diver can inspect anywhere from 200 to 300 timber piles per eight-hour day when piles average 25 feet (8m) in exposed length and are spaced within six feet of one another. This assumes approximately five hours spent in the water after taking into consideration other field tasks such as mobilization to the site, dive station setup and breakdown, bent row numbering/stationing, diver changeovers, and demobilization. This equates to an inspection rate of 40 to 60 piles per hour, with each diver averaging 60 to 90 seconds per pile.

Keep in mind that the diver must alternately descend down one pile to a depth of at least 17 feet (5m) to observe the pile where it enters the mudline before traversing over to an adjacent pile and ascending. The diver must also keep verbally communicating his location and observations to the team leader stationed topside. He will frequently answer questions and clarify observations, often stopping while findings and measurements are documented or the surface tender pulls up or slackens his umbilical air hose upon the diver's directives. Very often he will carry a camera for documenting discovered damage and must periodically take photographs. Significant time can be lost if his umbilical hose becomes snagged on an obstruction, in which case the diver must backtrack to unsnag it.

However, as conditions become more adverse in the way of reduced underwater visibility, stronger currents, deeper water, and lower water temperatures, this production rate will drop considerably. For instance, zero underwater visibility in combination with a water velocity of two feet per second will frequently result in 70 piles or less being inspected at Level I during five hours of water time, assuming an experienced diver is performing the inspection. In zero visibility, a diver must first descend and then ascend along the same pile before swimming to the next pile, otherwise disorientation will ensue. A water velocity of two feet per second is about the highest flow most physically fit divers can handle for any extended period before fatigue sets in. In harbors and tidally affected waterways, diver productivity will be greatest during slack flow periods, particularly at low tide when some of the damage may be seen above the waterline. Although the scheduling of inspection dives to coincide with slack tide occurrences are advantageous to a dive team, such events are typically of short duration before water velocity escalates.

A variation of this type of effort is a surface swim-by inspection that keeps the inspector positioned within three feet of the water surface while examining structural elements. Unless the water depth is shallow and underwater visibility is good, a surface swim-by inspection will not allow the diver to observe all exposed exterior surfaces of submerged elements. Therefore it has limited value in locating all of the existing severe damage on most marine structures situated in deeper, murkier water. Although neither the ASCE nor the NBIS would recognize this mode of inspection as an acceptable level of effort if it fails to reveal all major damage that would have been obvious to a diver at depth, many divers will inappropriately substitute a surface swim-by in lieu of a Level I inspection. While this occurs predominantly out of ignorance as to what a Level I swim-by actually entails, surface swim-by inspections are frequently misused by divers falling behind their inspection schedule and are applied as a means of catching up.

Unfortunately, surface swim-bys are also widely misused by firms low-balling a bid price to perform an inspection. However, unless authorized by the owner as part of the defined scope, a surface swim-by effort should never be employed when the water depth exceeds the underwater visibility. In general, a diver claiming a Level I inspection rate of 100 piles per hour is indicative of a surface swim-by.

Level II: More detailed in nature than a Level I inspection, a Level II effort requires partial cleaning of marine growth or other surface fouling encrustations in order to reveal hidden deterioration. Because of the additional expense and time-consuming labor, a Level II inspection effort is limited to representative portions of the components on which the inspection is being performed. Often referred to as a "hands-on" inspection, it typically includes measurements not only intended to document the type of defect and its size or dimensions, but also its position on the structural element as well as the element's location with respect to the structure. Photographic or video documentation is commonly included.

As an example, a Level II inspection on steel members may also involve the scraping away of oxidized metal or rust on two to 10 percent of their surface area to assess the remaining cross-section obscured by the rust. This information may then be used in determining the appropriate type of repair needed to correct the damage. This type of inspection effort also may involve the technique of tapping and sounding a component with a hammer to identify weakened sections of steel or concrete, or hollow areas in members comprised of timber that have been eaten away by marine borers. In addition, a Level II inspection on wooden elements may frequently employ a simple penetration test using an ice pick or awl to determine if the timber is undergoing soft rot. In particular, timber piles subjected to a Level II examination may often warrant systematic circumferential measurements at specific elevations along their length to ascertain overt section loss caused by abrasion or Limnoria attack. The documented residual pile diameters resulting from the inspection may then be used in a load-bearing analysis of the structure to compute residual capacity, and perhaps to determine what structural modifications or retrofits will be required in a repair design aimed at restoring or increasing a pile's original load-bearing capacity.

A Level II effort is typically conducted on at least 10 percent of the submerged components of a structure, particularly during execution of a routine underwater inspection normally consisting of a 100 percent Level I and 10 percent Level II effort. By contrast, repair design inspections will frequently entail a 30 percent or higher Level II effort in combination with a 100 percent Level I, although the number of components requiring a Level II inspection has been known to include all submerged structural elements. Production rates for inspecting different types of structural components will vary markedly when performing a Level II inspection effort and depend on the structural materials comprising the underwater members, environmental conditions, amount of encrusting substances that must be removed, configuration of the substructure, amount of existing deterioration, and the proficiency level of the diver. However, Level II inspections are generally much more time consuming than a Level I. With fairly good underwater visibility and little or no current, an experienced diver can inspect an average of 14 steel H-piles per hour at Level II while working in water depths of 25 feet (8m). This production rate will lessen as conditions get worse.

Level III: A Level III inspection effort is highly detailed in nature, typically utilizing non-destructive testing (NDT) or partially destructive testing methods in order to detect covert or interior material section loss and damage. Such techniques are generally focused on suspected areas of representative or critical structural members. Often requiring extensive cleaning, detailed measurements, and the use of ultrasounding technology to evaluate material homogeneity or remaining section for corrosion profiling of steel members, a Level III effort is conducted on a statistically representative sample, normally five percent, of a specific population of structural components such as piles or pile caps. It may also involve physical material sampling in which timber or concrete corings are removed for laboratory analysis. Typically, Level III inspections are substantially slower in execution than a Level II effort.

For example, a Level III effort conducted on steel H-piles under good conditions would equate to a production rate of roughly five piles per hour. This is because more extensive cleaning is performed in combination with the taking of more detailed measurements, noting zones of corrosion and thickness of flanges and webs at various elevations using ultrasonic thickness measuring devices and micrometers.

Minimum Qualifications for Diving Personnel
A properly conducted underwater inspection goes well beyond the documentation of observed defects, frequently necessitating that sound judgement be applied to decisions made throughout the inspection process. An understanding of load paths, structural redundancy, and the structural significance of observed damage are all important aspects of underwater investigations, particularly when assigning condition assessment ratings to the various components of a structure during a routine inspection.

Inspection personnel must not only be proficient in commercial diving techniques in order to gain access to submerged structural elements, they must also possess a firsthand knowledge of a wide array of deterioration and their causes for the purpose of quantifying the damage and determining the most economical and cost-effective repairs. The task of measuring and recording section loss along a member can be meaningless unless it is determined where the loss has occurred relative to the point of maximum bending moment or shear. For example, conducting an interim or special inspection on a population of timber piles undergoing Limnoria attack may require documenting circumferences at periodic intervals along representative members to evaluate section loss against bending moments at various locations along the piles. Ultimately, the results of the special inspection may recommend that a follow-up in-depth or repair design inspection be performed. However, the special inspection findings will generally dictate the appropriate levels of follow-up inspection effort, including testing, to be undertaken based on the repairs that will be most cost-effective. Obviously, piles that are to be jacketed in order to remediate Limnoria-induced biodeterioration will not require the same level of inspection effort as piles on which each defect will be repaired individually by such methods as posting, shimming, and concrete encasement.

While the Underwater Investigations Standard Practice Manual published by the ASCE recommends that an underwater inspection team shall be led by and under the direct on-site supervision of a registered professional civil or structural engineer who acts as team leader, it also stipulates that the team leader should be a trained diver who physically performs at least 25 percent of the diving inspection work. The ASCE further recommends that the team leader should have a minimum of five years experience conducting subaqueous structural investigations in combination with a minimum of five years engineering experience specifically related to the type of facility being inspected.

Although such recommended requirements typically apply to baseline (inventory), routine, damage (post-event), special (interim), and repair design (in-depth) inspections, the ASCE has less stringent team leader requirements relating to construction inspections, whether they be focused on new construction or repair construction. In such cases, a graduate of a four-year civil or structural engineering curriculum will suffice as team leader in lieu of a licensed professional engineer as long as the individual has a minimum of two years of construction inspection experience. However, the ASCE also concedes that, for construction inspections, an individual with a minimum of 10 years construction inspection experience and possessing certification from a nationally recognized building authority such as the National Institute for Certification in Engineering Technologies (NICET Level IV) or the US Department of Transportation's 80-hour course in "Safety Inspection of in-Service Bridges" can also qualify as a team leader.

ASCE guidelines further suggest that other dive team members should either hold a four-year engineering degree or have completed a course of study in structural inspections.

Diver Training and Safety
Of equal importance alongside technical qualifications, an underwater inspector should be experienced and proficient as a diver in order to perform structural inspections under hostile environmental conditions. Swift currents, swirling vortices, poor underwater visibility, cold water, confined spaces, and submerged hazards can often distort an inspection diver's perceptions about the actual condition of a submerged structure, frequently disorienting the diver, as well as subject him to substantial physical and psychological duress.

Even a recreational sport scuba diver with hundreds of hours logged underwater may not be fully prepared to adjust to such adverse conditions. As a general rule, sport divers typically restrict their diving to open water settings where warm, clear water and slower currents often predominate. Whereas recreational scuba enthusiasts dive for enjoyment and will usually have the option of selecting a comfortable environment, inspection divers are task-oriented and often must deal with a harsh environment in order to complete the job. This necessitates that they receive training in commercial diving techniques in order to learn how to function effectively under more difficult conditions.

OSHA makes a valid distinction between commercial diving and recreational scuba diving. The training and certification a recreational diver obtains is relatively miniscule in comparison to the hundreds of training hours a commercial diver receives. Recreational dive training organizations, such as NAUI, PADI, and YMCA, openly acknowledge that diving certification under their auspices is inadequate training for underwater commercial work which, by its very nature, normally utilizes hard hat gear supported by surface-supplied air in combination with diver-to-surface audio communications and frequently employs the use of underwater tools. The use of scuba equipment in underwater commercial operations has minimal value, particularly when applied to Level II and Level III inspection efforts, since its limited air supply and lack of communications render it impractical and inefficient for subqueous structural inspections.

By contrast, diving investigations using surface-supplied air produce far better results. For one, diver measurements and observations can be readily documented by topside personnel, thus providing accurate information on which to base complex rehabilitation schemes and repair designs. In addition, the umbilical air hose used in conjunction with such an investigation not only tethers the diver to a supporting cast on the surface, but also provides him with an unlimited supply of breathable air, making diving much safer and allowing extended underwater operations, both of which contribute immeasurably to the effectiveness and overall quality of the inspection.

Currently, the minimum manning requirement for a commercial diving operation as mandated by OSHA, the US Coast Guard, and the ADC Consensus Standards is three persons - the team leader, diver, and tender. However, a standby safety diver must be added to the dive team as a fourth member when diving in excess of 100 feet (30m), when in-water decompression is necessary, or when underwater hazards exist. Furthermore, an additional diver must be stationed at the underwater point of entry for the purpose of tending the primary diver's umbilical hose whenever diving is conducted in enclosed or physically confining spaces. According to the commercial diving standards put forth by the governing agencies, each in-water diver must be continuously tended from the surface by a separate dive team member.

Based on these guidelines, an underwater inspection carried out in a confined space environment would warrant a dive team comprised of six persons: the team leader, primary inspection diver, in-water diver/tender, standby safety diver, and two surface tenders. Such an operation would require three separate umbilical air hose rigs in combination with diver communications, each with a compressed air supply consisting of both primary and backup sources, and if the dive surpassed a depth of 100 feet (30m) or exceeded the no-decompression limits, a recompression chamber should be readily available at the site.

Unfortunately, recreational divers continue to be hired for underwater inspection work which they are insufficiently trained, experienced, and equipped to undertake. In point of fact, the utilization of recreational divers to perform underwater structural inspections that are clearly commercial in nature is extremely widespread among many public agencies and engineering consulting firms alike. Quite often, this is attributable to an ignorance of the risks involved in this type of work. Such ignorance commonly manifests itself in criteria found in issued RFPs, bid requests, and contracts which nebulously stipulate that the inspector need only be certified as a diver, thus allowing an individual with only basic YMCA sport diver training to qualify for the work.

Sometimes this can lead to a tragedy, as was the case in March 1997 when two recreationally-trained scuba divers hired by a state agency in Washington entered an underground, 104 feet (31m) deep water-filled tunnel. They had only a limited air supply in the form of scuba tanks strapped to their bodies, no surface tethering, no means of communication, and no stand-by safety diver immediately on hand. After the divers failed to emerge from the murky, 40-degree Fahrenheit water, the agency called in two additional scuba divers, also with limited training and inadequate equipment, to effect a rescue. The end result was that all four divers perished after running out of air. Several times a year, unqualified and poorly trained divers lose their lives in very similar accidents.

In view of this type of catastrophe, it follows that public agencies and engineering consulting firms should take heed of the potentially dangerous liability of hiring recreational divers for commercial diving work since, in the event of an accident, it can be viewed as negligence that significantly contributed to the dire consequence. Even citing recreational diving certification as a prerequisite to qualify for the work can lead to possible OSHA violations, since their regulations stipulate that an employer's obligation exists for compliance with all provisions of the commercial diving standards. The Washington disaster was carried out in a manner that defied commercial diving safety standards on three major counts: insufficient training, undermanning, and inadequate equipment. An undertaking of this scale would have required a minimum of six properly trained and experienced individuals on the dive crew, equipped with surface-supplied diver support gear with primary air and at least two separate sources of backup air, diver-to-surface communications, and a recompression chamber. And while such an operation would have been many times more expensive than the one that ended in tragedy, the lower cost of using recreational divers supported by marginal equipment will ultimately prove to be insignificant when weighed against the staggering liability costs that will surely result once the smoke clears from this debacle.

Sacrificing Safety and Quality to Save Money
Even with an awareness of OSHA guidelines, there are some public agencies and engineering firms that will frequently sacrifice safety in favor of the potential cost savings associated with using recreational divers. As a general rule, correctly performed underwater inspections are expensive and require considerable effort to execute. Associated costs will vary and are sensitive to many factors, including the size and type of submerged structure, inspection level of effort performed, water depth, water velocity, polluted water, water temperature, the extent of underwater visibility, the existence of confined or enclosed spaces, the amount of obscuring marine growth or other encrustations requiring removal, and the presence and amount of obstructing debris. Special equipment requirements such as workboats, underwater cameras and video systems, waterblasters for removing marine growth, ultrasonic instruments for gauging section loss or remaining thickness of steel members, hydraulically-powered coring tools for obtaining timber and concrete samples, and recompression chambers will further contribute to the cost.

The desire to curtail costs at the expense of quality and safety can be a strong motivational force among organizations which are routinely strapped with limited budgets. Most owners of marine facilities will rely almost exclusively on engineering consulting firms either to develop a maintenance program for its facility or to work on some phase of their maintenance program involving underwater inspection. They often contract with the consultant offering the lowest price from among a short-listed field of the most technically qualified firms submitting proposals to perform the owner's stipulated scope of work. It is not uncommon for the owner to ask the consultant to sharpen its pencil further before an agreement is reached that favors the owner's budget. If one cannot be reached, the owner will occasionally go to the next firm in the short-list ranking until a reduction in price is achieved without a corresponding modification of the workscope.

Sometimes the owner will select a firm based strictly on technical merit, then enter into negotiations with the chosen firm until a not-to-exceed price or upset limit is agreed upon for the consultant to provide the required services. The riskiest contracting approach, however, occurs when the owner puts the work out for bid without giving any consideration whatsoever to a firm's qualifications. This tactic has occasionally proved to be disastrous, sometimes putting public safety at risk.

Quite often, the owner will have a preconceived but unrealistic expectation of what the engineering services should cost and will use this as a basis for negotiating the price downward to levels that will compromise the quality of the work. When this happens, the risk of reduced safety escalates, not only in terms of the personnel performing the diving inspection, but also in terms of diminished safety to the public since poor quality can easily translate into the potential for impending structural failure conditions to be overlooked.

Such unrealistic expectations are typically predicated on previous work performed by past consultants who, eager to get the work, did not adhere to underwater inspection protocol established by the ASCE and OSHA and either intentionally or mistakenly underestimated the minimum amount of time needed to properly conduct the inspection. In fact, breaches in quality and safety are most often proliferated by consulting engineering firms, making underwater inspection one of the most abused areas within the civil engineering industry. Because of its covert nature, poorly conducted inspection activities taking place below the waterline can routinely go unchallenged, the consequences of which can be extremely costly to an owner over the long term. A diver failing to note relatively minor deterioration that can be remediated at minimal expense in its early stages may ultimately cost the owner millions of dollars in major repairs down the road if left unchecked.

Once the work is awarded, the consultant will normally invoice the owner on either a lump sum or a time and materials basis, depending on the contract stipulations. If the hired engineering firm lacks in-house diving capability, the consultant, in an effort to achieve maximum profitability, will frequently subcontract with the least expensive diving entity to collect information about the condition of the submerged structures requiring inspection.

However, there is a widespread propensity among many engineering firms demonstrating an expertise in marine engineering to perceive themselves as having qualified divers on staff simply because some of their engineers happen to possess basic scuba certification. These same firms also have a tendency to believe that basic scuba gear is all that is needed to accomplish an underwater inspection. Generally speaking, most scuba certified divers are too inexperienced to adequately cope with adverse underwater environmental conditions to perform a meaningful inspection, often spending the majority of their diving time adapting to difficult situations and frequently becoming physically exhausted, hypothermic, or disoriented. The existence of strong currents, poor underwater visibility, and cold water will invariably hamper the quality of an untrained, inexperienced diver's inspection, substantially hindering productivity and causing such work to take longer to complete than originally anticipated.

In an attempt to save face with their employers, these same divers may be forced to shortcut an inspection in order to satisfy allotted time frames and budgeted man-hours, factors which ultimately determined the firm's final negotiated price or bid. If these same divers carry out the work using scuba gear, the accuracy of the inspection findings may be seriously flawed and incomplete since the documentation of various types and sizes of defects on a relatively
large, but deteriorated substructure would be made all the more difficult, to say the least, assuming none of the personnel examining the structural elements were endowed with a photographic memory. Keep in mind that unless scuba bottles are used in conjunction with a
band mask or diving helmet that incorporates diver-to-surface communication, the diver must keep coming to the surface to report observations and measurements to topside personnel. In addition, a major shortcoming of scuba is the limited time it permits the diver to stay submerged. On a fairly large substructure, there is always the temptation to rush the inspection in order to avoid having to change air tanks.

Various types and combinations of diving conditions encountered can directly affect the amount of time required to inspect a substructure in a manner that conforms to ASCE and NBIS guidelines. Swift currents and vortices will dramatically increase inspection time. One must remember that most bridges span the narrowest gap in a channel where water velocity is usually at a maximum and will quickly sap a diver's strength. Cold water can also slow the inspection and will constrain a diver's water time before the effects of hypothermia create mental confusion and drain the diver's energy. Deep water will limit bottom times because of dissolved nitrogen build-up in the tissues. Note that a diver working as deep as 60 feet (18m) is limited to 60 minutes in the water without having to undergo decompression. This time restriction becomes more severe with increasing water depth. Additionally, poor underwater visibility can easily cause a diver to become disoriented.

Construction debris in the form of cables, H-piles, pipes, and other items that commonly exist around bridge footings and the base of other types of marine structures are all potential diver hazards. Submerged driftwood and tree limbs can also hamper a diver, catching and entangling an umbilical hose. Ice floes pushed along by tidal and river currents during cold weather can also menace inspection divers. Overall, the more adverse the conditions, the less time a diver can realistically spend performing an inspection before he becomes ineffectual or endangers himself. For this reason, more frequent diver changeover is needed to continue the inspection. Because of this, one or more additional divers may be required to conduct the inspection in a safe, efficient, and reliable manner. A diver that is easily fatigued or has trouble equalizing the ambient pressure on his eardrums while submerged on an inspection assignment will often become a liability to the success of the project, no matter how skilled he is at recognizing deterioration that can lead to structural compromise. To avoid excruciating ear pain or risking personal safety, such an individual may defer going more than a few feet below the waterline altogether, only performing a surface swim-by inspection, at most.

To go a step further, if adverse diving conditions exist but were either unanticipated or disregarded during the bid proposal or price negotiation process, the diving contractor may very likely have insufficient manpower and equipment to execute a competent or meaningful inspection, thus burning out his diver or divers all too quickly. As a rule of safety, and to assure the quality and completeness of the inspection requirements, all members of the dive
team should be qualified inspection divers whenever adverse conditions are present so that frequent diver changeovers are possible.

Cutting Costs Can Cost Lives
Because of these problems, bridges and other water-based structures located in environments where severe conditions preside are often the most likely candidates for a structural collapse due to undetected compromise when award of the underwater inspection work is acquired through unrealistically low bid prices or cost negotiations which overwhelmingly favor the owner. Consulting engineers and owners must come to realize that unrealistic pricing tends to cultivate four primary conditions which lead to poor underwater inspections and can ultimately be very costly to an owner over the long run:

• The inspection diver is technically unqualified to recognize structural deterioration and deficiencies and their relationship to the integrity of the marine facility
  
• The diver is too inexperienced with adverse underwater conditions to give the inspection his full attention and complete all scope requirements
  
• The dive team is improperly or insufficiently manned and equipped to effectively execute the inspection
  
• The diver spends insufficient time inspecting the substructure.