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Construction Considerations
217
Chapter 17
Construction Considerations
17.1 Construction arrangements Arrangements for construction can be even more varied than arrangements for design. These can range from complete 'turn-key' contracts to complete 'do it yourself' approaches, with everything in between. Complete 'turn-key' situations are unlikely except for governmental facilities or for large companies with no previous experience in the field. Most of the smaller seawater systems to date have been predominately towards the 'do it yourself' side with varying degrees of outside contracted support. In many cases the user acts as his own general contractor. This has both advantages and disadvantages. The big advantage is that as problems surface they can be addressed and resolved with a minimum of contractual conflicts. In short, this option allows much more flexibility in handling the unexpected. On the other hand, the often stated major time and cost savings associated with being your own general contractor, in many cases, may not be that substantial. The big disadvantages are that the seawater user rarely has any directly relevant prior construction experience, does not have the required supportive infrastructure both in physical equipment or management systems, and generally grossly underestimates the problems encountered in the construction of aquaculture facilities. For a project of any size, a lot of time and effort goes into developing the required infrastructure, often by trial and error. Construction and deployment schedules, based on inexperience, rarely can anticipate errors or circumstances that lose time. Schedule slippage create a self-destructive panic mentality. This results in the adoption of short-term stop gap solutions rather than viable long-term answers. For owners with limited seawater construction experience, it may be prudent to retain an aquacultural engineer for some level of construction management (see Mayo, 1998) for a discussion of roles and responsibilities of the aquacultural engineering consultant). The level of involvement can range from periodic site visits to a full-time construction inspector. In large projects, the design engineer may also review shop drawings from the general contractor or subcontractors or review change orders (see Section 17.3). In the absence of a significant role in construction management it is difficult to hold the design engineer responsible for field changes made by the owner or contractor.
17.2 Construction cost estimating For many projects, being able to accurately estimate costs may be critical. Costs may well be the dominant factor in major design decisions. Large estimating errors that become apparent late in a project can prove fatal to the project. It is, therefore, important to look at the estimating process.
218 Costing numbers can come from many sources. Some of the better general sources are commercially available construction costing guide annuals (Dodge, 2000; Means, 2000). These guides have not only unit prices but also installation and service costs with adjustment factors for different parts of the U.S. Such convenient cost estimating guides may not be available for some parts of the world. Initial cost estimating for projects in some of these countries has used the available guides, for lack of a better alternative, with adjustment factors for transportation, importation and local service costs. Since much of the specialized equipment is commonly imported for projects in these countries, these estimates are usually adequate for preliminary design, evaluation of alternatives, and decision making. When operating in unfamiliar parts of the world, it is very advisable, at some point in the design process, to develop an arrangement with a local engineering and design firm that has specific knowledge about conditions in the area, even though they may not have any aquacultural experience. Additional general sources for pricing data are catalogues from major mail-order firms such as Granger, McMaster and Sears. With these equipment cost numbers, it is important to adjust the values for the passage of time from the present to the estimated ordering date. It is also important to include related services, such as engineering services, transportation, import duties, broker fees, storage and assembly or preparation for installation. Neglecting these considerations can lead to major cost underestimations. There are other major sources of error. These include uncosted essential components or services. These missed items are often necessary but secondary components. Examples include a chain link fence around the facility, a concrete base for machinery, or a storage area. Another major source of errors results from the inclusion of new or upgraded requirements. These might include the requirement for water filtering halfway through design, where it had previously been judged to be unnecessary. Increased flow rate or additional temperature control are also examples. Surprisingly, the overall error on correctly identified items is usually small, even though the uncertainty about the cost of individual items is often high. While some items may prove to have been estimated high, others will be estimated low, and they tend to cancel. An exception is estimating the cost of in-water construction of intakes and discharges. Even engineers and architects with some experience in this area, will generally estimate far too low, and the cost discrepancies can be large. Rapidly increasing regulatory construction constraints are dramatically increasing in-water costs. In addition to in-water work, any changes in direction or requirements, project stoppages, and overlooked items or services are the major sources of underestimated costs. Cost estimates will usually be generated early in the project and continually modified as design progresses. These estimates are usually as detailed as design definition will allow and are often a source of feedback information that strongly influences the design efforts. Cost estimates almost inevitably creep or sometimes leap upward as the design definition progresses. Without dramatic downward scope changes, a general guide is that the final cost after everything is included will be about a factor of 7r greater than the first estimate. Why Jr ? The humorous answer is because it is an irrational number, but considerable experience indicates that a cost increase of about 300% is correct. Downward cost changes are usually the result of specific management decisions to reduce the project's size or scope. The budgeted cost contingency factor over the current cost estimate is a function of the design status and specific circumstances. However, with a completely specified design ready for construction bidding and a complete cost estimate, the cost contingency should not be less than 25%. This
219 is a somewhat higher value than sometimes used for general contracting but it is not a large number, since the major cost estimating errors already discussed can easily increase costs by a factor of two or more.
17.3 Design changes The end purpose of the design and construction phase is an operational system. The design is based on a multitude of facts and assumptions about the site, species, operating procedures and operator skills. A specific project is likely to have some unique characteristics or unique combination of parameters that have never been tried before. Some of the possible inherent design problems and mistakes may show up during construction. Others will not be obvious until full-scale operations. The 'facts and assumptions' and value judgments on which the design is based may well change before construction is completed. This can occur as new information is received, from direct experience (if the site and species preparatory work has been properly done there should not be any site or species surprises, yet they do often occur), or from 'improvements' that are perceived during construction. Even more likely are important management decisions which result in a major change in the scale of the project, usually downward for cost and schedule reasons. Some design changes may be applied directly during construction, while the more disruptive changes may be held for retrofitting after the primary construction phase. Some changes may not fit either pattern. These are the critical changes that cannot be deferred or readily accommodated. These can halt construction completely while the problems are sorted out. These changes can easily kill a project, because a construction halt is very expensive, very disruptive, and certain to trigger a top management reassessment of the entire project.
17.4 Installation of seawater lines If an intake system is to be placed offshore, its installation may be the single most difficult aspect of the project. Under the unlikely conditions that a site has no waves or water currents under any conditions or that the deployment is for a very short time period, the intake lines can be left exposed on the bottom. Even in this case, they will have to be secured with heavy collars, screw auger anchors, tiebacks, pilings or bent over rods driven into the bottom. For most conditions, the lines and intakes will have to be both excavated and secured. This excavation, placement and backfilling of lines and intakes may only be possible at certain seasons, tidal conditions and environmental conditions. This may impose severe scheduling constraints or delays into the entire project. Environment regulatory constraints on construction may dramatically increase these problems (see Section 3.3). Deployment opportunities may be very limited and not completely predictable. Environmental changes that occur during deployment can severely threaten the operation. It is therefore important to carry out the deployment cleanly and quickly. Due to these problems, intake and discharges may actually be built at considerable variance with the design specifications. Excavation methods will depend on soil types and environmental conditions. For common sand, clay, and mud bottoms with no appreciable waves or current, the trenches for the lines can be excavated with a backhoe or dragline from the beach at low tide, and from a barge at high tide. The trench will usually not backfill itself before the lines can be installed. Jetting
220 and blasting, if allowed, are two other options. Sediment curtains surrounding the excavation may be required. In the presence of significant current or waves, the tasks become much more difficult and should not be attempted by the inexperienced. At best, the jobs are difficult and can be almost impossible. There are at least two ways to lay the lines in the excavated trench. Since most intake lines are likely to be continuous synthetic pipes, these pipes will readily float, especially if full of air. These lines need weight to hold them on the bottom, even when full of water. This can be done with concrete collars. The entire line with concrete collars can be pulled off the beach, floated and held in position, then sunk in place by opening a temporary valve at the offshore end (Sclairpipe Marine Pipeline Installation Construction, 1969; Janson, 1975). After removal of the end plug and valve, the intake structure can be lowered and secured to the end of the line. The intake structure and line can then be secured to the bottom and backfilled. Under some conditions, the pipe may tend to rise in the trench on being backfilled (Janson, 1975). The second method is to assemble the line and intake together on shore. If the intake is formed into a sled type arrangement, the intake and line can be dragged directly down the trench along the bottom (Bouck, 1981). In this case, weight was added after positioning, by filling some of the pipes with concrete. It would probably be possible to add some jetting capability directly to an 'intake' sled, so that it could excavate its own trench in some soil types. There is trenching equipment used in the offshore oil industry to bury pipe lines, which might also be useable but it is very expensive. If the trench shows a tendency to backfill itself, it may be possible to let nature carry out this task. In sheltered areas, nature may be too slow and the trench may have to be backfilled.
17.5 Start-up It is virtually inevitable, especially in the 'do it yourself' projects, that initial start-up and operations will commence before construction is fully completed. Even if both construction and operating crews work for the same company, it is imperative that there be a clear chain of command and coordinated activities between the groups to avoid mutual interference. Initial start-up of various systems has to be done with some care, whether by construction or operating personnel. The system to be started must be carefully and personally checked by the person in charge immediately prior to initial start-up. Things to be checked include that the system to be tested is complete (an incomplete system may not perform as intended), all components and parts are firmly secured (not just in position), there are no tools, rocks or debris in lines or sumps, the system is in start-up configuration (switches, valves and hatches in correct position, guards, interlocks and safeties 'on') and lastly that all personnel are clear of hazards and aware of what is about to happen. The previous sentences appear to be obvious and logical, but not doing these things has resulted in much serious damage. Examples of problems include a foreman taking the word of a worker that rocks have been removed from a sump, a switch in the full-on position instead of full-off, an open unvalved pipe in a large tank and a worker unaware of impending operation of a piece of equipment. Even if all these things are well done, the initial start-up is still a relatively high risk operation. If anything has been designed, fabricated, or installed improperly it may quickly become apparent. Start-up procedures have to be well thought out before hand, and implemented as planned. This is not the time for hasty or snap judgments. When starting equipment, alertness and prompt
221 shutdown can avert otherwise serious damage if something is wrong. This may require stationing people in various critical places and providing them means for communicating. Signs of problems include unusual noise or vibration, burning smells or smoke; water where it is not supposed to be; lack of water where it is supposed to be; and equipment getting hotter than it should. It is not uncommon to have several cycles of start-stop-reevaluate-restart, even for a perfectly good system. Common problems can be: a virgin 'self-priming' pump not priming itself the first time; some squeaking rotating machinery that was not lubricated; air locks in the pipes; vibrating parts that need to be better secured; and a system that is erroneously configured. The first few minutes of operations, as the equipment proceeds to steady state or equilibrium conditions, and testing over the first few operating cycles (such as tidal) are the most dangerous. Weak components usually will fail after some relatively short period of actual use, generally a few days up to a few weeks. After this 'burn in' period the probability of the equipment failing is relatively low. However, there is the possibility of operational problems due to seasonal factors, which may take some time to develop. In addition, there is a high potential for serious problems during the first few major storm events experienced by a new system. During initial start-up the experience level of all personnel with the specific equipment involved is usually at a minimum. The operators are not familiar with the equipment capabilities, limitations and specific constraints. Problems that have occurred include: toxicity due to 'new' materials; destruction of piping by water hammer due to closing valves too quickly; the overheating and death of brood stocks due to uncalibrated or poorly set heating controls; drain lines clogged with construction residues; or inadvertently contaminating or cross-feeding with different water types.
Chapter 17
Construction Considerations
17.1 Construction arrangements Arrangements for construction can be even more varied than arrangements for design. These can range from complete 'turn-key' contracts to complete 'do it yourself' approaches, with everything in between. Complete 'turn-key' situations are unlikely except for governmental facilities or for large companies with no previous experience in the field. Most of the smaller seawater systems to date have been predominately towards the 'do it yourself' side with varying degrees of outside contracted support. In many cases the user acts as his own general contractor. This has both advantages and disadvantages. The big advantage is that as problems surface they can be addressed and resolved with a minimum of contractual conflicts. In short, this option allows much more flexibility in handling the unexpected. On the other hand, the often stated major time and cost savings associated with being your own general contractor, in many cases, may not be that substantial. The big disadvantages are that the seawater user rarely has any directly relevant prior construction experience, does not have the required supportive infrastructure both in physical equipment or management systems, and generally grossly underestimates the problems encountered in the construction of aquaculture facilities. For a project of any size, a lot of time and effort goes into developing the required infrastructure, often by trial and error. Construction and deployment schedules, based on inexperience, rarely can anticipate errors or circumstances that lose time. Schedule slippage create a self-destructive panic mentality. This results in the adoption of short-term stop gap solutions rather than viable long-term answers. For owners with limited seawater construction experience, it may be prudent to retain an aquacultural engineer for some level of construction management (see Mayo, 1998) for a discussion of roles and responsibilities of the aquacultural engineering consultant). The level of involvement can range from periodic site visits to a full-time construction inspector. In large projects, the design engineer may also review shop drawings from the general contractor or subcontractors or review change orders (see Section 17.3). In the absence of a significant role in construction management it is difficult to hold the design engineer responsible for field changes made by the owner or contractor.
17.2 Construction cost estimating For many projects, being able to accurately estimate costs may be critical. Costs may well be the dominant factor in major design decisions. Large estimating errors that become apparent late in a project can prove fatal to the project. It is, therefore, important to look at the estimating process.
218 Costing numbers can come from many sources. Some of the better general sources are commercially available construction costing guide annuals (Dodge, 2000; Means, 2000). These guides have not only unit prices but also installation and service costs with adjustment factors for different parts of the U.S. Such convenient cost estimating guides may not be available for some parts of the world. Initial cost estimating for projects in some of these countries has used the available guides, for lack of a better alternative, with adjustment factors for transportation, importation and local service costs. Since much of the specialized equipment is commonly imported for projects in these countries, these estimates are usually adequate for preliminary design, evaluation of alternatives, and decision making. When operating in unfamiliar parts of the world, it is very advisable, at some point in the design process, to develop an arrangement with a local engineering and design firm that has specific knowledge about conditions in the area, even though they may not have any aquacultural experience. Additional general sources for pricing data are catalogues from major mail-order firms such as Granger, McMaster and Sears. With these equipment cost numbers, it is important to adjust the values for the passage of time from the present to the estimated ordering date. It is also important to include related services, such as engineering services, transportation, import duties, broker fees, storage and assembly or preparation for installation. Neglecting these considerations can lead to major cost underestimations. There are other major sources of error. These include uncosted essential components or services. These missed items are often necessary but secondary components. Examples include a chain link fence around the facility, a concrete base for machinery, or a storage area. Another major source of errors results from the inclusion of new or upgraded requirements. These might include the requirement for water filtering halfway through design, where it had previously been judged to be unnecessary. Increased flow rate or additional temperature control are also examples. Surprisingly, the overall error on correctly identified items is usually small, even though the uncertainty about the cost of individual items is often high. While some items may prove to have been estimated high, others will be estimated low, and they tend to cancel. An exception is estimating the cost of in-water construction of intakes and discharges. Even engineers and architects with some experience in this area, will generally estimate far too low, and the cost discrepancies can be large. Rapidly increasing regulatory construction constraints are dramatically increasing in-water costs. In addition to in-water work, any changes in direction or requirements, project stoppages, and overlooked items or services are the major sources of underestimated costs. Cost estimates will usually be generated early in the project and continually modified as design progresses. These estimates are usually as detailed as design definition will allow and are often a source of feedback information that strongly influences the design efforts. Cost estimates almost inevitably creep or sometimes leap upward as the design definition progresses. Without dramatic downward scope changes, a general guide is that the final cost after everything is included will be about a factor of 7r greater than the first estimate. Why Jr ? The humorous answer is because it is an irrational number, but considerable experience indicates that a cost increase of about 300% is correct. Downward cost changes are usually the result of specific management decisions to reduce the project's size or scope. The budgeted cost contingency factor over the current cost estimate is a function of the design status and specific circumstances. However, with a completely specified design ready for construction bidding and a complete cost estimate, the cost contingency should not be less than 25%. This
219 is a somewhat higher value than sometimes used for general contracting but it is not a large number, since the major cost estimating errors already discussed can easily increase costs by a factor of two or more.
17.3 Design changes The end purpose of the design and construction phase is an operational system. The design is based on a multitude of facts and assumptions about the site, species, operating procedures and operator skills. A specific project is likely to have some unique characteristics or unique combination of parameters that have never been tried before. Some of the possible inherent design problems and mistakes may show up during construction. Others will not be obvious until full-scale operations. The 'facts and assumptions' and value judgments on which the design is based may well change before construction is completed. This can occur as new information is received, from direct experience (if the site and species preparatory work has been properly done there should not be any site or species surprises, yet they do often occur), or from 'improvements' that are perceived during construction. Even more likely are important management decisions which result in a major change in the scale of the project, usually downward for cost and schedule reasons. Some design changes may be applied directly during construction, while the more disruptive changes may be held for retrofitting after the primary construction phase. Some changes may not fit either pattern. These are the critical changes that cannot be deferred or readily accommodated. These can halt construction completely while the problems are sorted out. These changes can easily kill a project, because a construction halt is very expensive, very disruptive, and certain to trigger a top management reassessment of the entire project.
17.4 Installation of seawater lines If an intake system is to be placed offshore, its installation may be the single most difficult aspect of the project. Under the unlikely conditions that a site has no waves or water currents under any conditions or that the deployment is for a very short time period, the intake lines can be left exposed on the bottom. Even in this case, they will have to be secured with heavy collars, screw auger anchors, tiebacks, pilings or bent over rods driven into the bottom. For most conditions, the lines and intakes will have to be both excavated and secured. This excavation, placement and backfilling of lines and intakes may only be possible at certain seasons, tidal conditions and environmental conditions. This may impose severe scheduling constraints or delays into the entire project. Environment regulatory constraints on construction may dramatically increase these problems (see Section 3.3). Deployment opportunities may be very limited and not completely predictable. Environmental changes that occur during deployment can severely threaten the operation. It is therefore important to carry out the deployment cleanly and quickly. Due to these problems, intake and discharges may actually be built at considerable variance with the design specifications. Excavation methods will depend on soil types and environmental conditions. For common sand, clay, and mud bottoms with no appreciable waves or current, the trenches for the lines can be excavated with a backhoe or dragline from the beach at low tide, and from a barge at high tide. The trench will usually not backfill itself before the lines can be installed. Jetting
220 and blasting, if allowed, are two other options. Sediment curtains surrounding the excavation may be required. In the presence of significant current or waves, the tasks become much more difficult and should not be attempted by the inexperienced. At best, the jobs are difficult and can be almost impossible. There are at least two ways to lay the lines in the excavated trench. Since most intake lines are likely to be continuous synthetic pipes, these pipes will readily float, especially if full of air. These lines need weight to hold them on the bottom, even when full of water. This can be done with concrete collars. The entire line with concrete collars can be pulled off the beach, floated and held in position, then sunk in place by opening a temporary valve at the offshore end (Sclairpipe Marine Pipeline Installation Construction, 1969; Janson, 1975). After removal of the end plug and valve, the intake structure can be lowered and secured to the end of the line. The intake structure and line can then be secured to the bottom and backfilled. Under some conditions, the pipe may tend to rise in the trench on being backfilled (Janson, 1975). The second method is to assemble the line and intake together on shore. If the intake is formed into a sled type arrangement, the intake and line can be dragged directly down the trench along the bottom (Bouck, 1981). In this case, weight was added after positioning, by filling some of the pipes with concrete. It would probably be possible to add some jetting capability directly to an 'intake' sled, so that it could excavate its own trench in some soil types. There is trenching equipment used in the offshore oil industry to bury pipe lines, which might also be useable but it is very expensive. If the trench shows a tendency to backfill itself, it may be possible to let nature carry out this task. In sheltered areas, nature may be too slow and the trench may have to be backfilled.
17.5 Start-up It is virtually inevitable, especially in the 'do it yourself' projects, that initial start-up and operations will commence before construction is fully completed. Even if both construction and operating crews work for the same company, it is imperative that there be a clear chain of command and coordinated activities between the groups to avoid mutual interference. Initial start-up of various systems has to be done with some care, whether by construction or operating personnel. The system to be started must be carefully and personally checked by the person in charge immediately prior to initial start-up. Things to be checked include that the system to be tested is complete (an incomplete system may not perform as intended), all components and parts are firmly secured (not just in position), there are no tools, rocks or debris in lines or sumps, the system is in start-up configuration (switches, valves and hatches in correct position, guards, interlocks and safeties 'on') and lastly that all personnel are clear of hazards and aware of what is about to happen. The previous sentences appear to be obvious and logical, but not doing these things has resulted in much serious damage. Examples of problems include a foreman taking the word of a worker that rocks have been removed from a sump, a switch in the full-on position instead of full-off, an open unvalved pipe in a large tank and a worker unaware of impending operation of a piece of equipment. Even if all these things are well done, the initial start-up is still a relatively high risk operation. If anything has been designed, fabricated, or installed improperly it may quickly become apparent. Start-up procedures have to be well thought out before hand, and implemented as planned. This is not the time for hasty or snap judgments. When starting equipment, alertness and prompt
221 shutdown can avert otherwise serious damage if something is wrong. This may require stationing people in various critical places and providing them means for communicating. Signs of problems include unusual noise or vibration, burning smells or smoke; water where it is not supposed to be; lack of water where it is supposed to be; and equipment getting hotter than it should. It is not uncommon to have several cycles of start-stop-reevaluate-restart, even for a perfectly good system. Common problems can be: a virgin 'self-priming' pump not priming itself the first time; some squeaking rotating machinery that was not lubricated; air locks in the pipes; vibrating parts that need to be better secured; and a system that is erroneously configured. The first few minutes of operations, as the equipment proceeds to steady state or equilibrium conditions, and testing over the first few operating cycles (such as tidal) are the most dangerous. Weak components usually will fail after some relatively short period of actual use, generally a few days up to a few weeks. After this 'burn in' period the probability of the equipment failing is relatively low. However, there is the possibility of operational problems due to seasonal factors, which may take some time to develop. In addition, there is a high potential for serious problems during the first few major storm events experienced by a new system. During initial start-up the experience level of all personnel with the specific equipment involved is usually at a minimum. The operators are not familiar with the equipment capabilities, limitations and specific constraints. Problems that have occurred include: toxicity due to 'new' materials; destruction of piping by water hammer due to closing valves too quickly; the overheating and death of brood stocks due to uncalibrated or poorly set heating controls; drain lines clogged with construction residues; or inadvertently contaminating or cross-feeding with different water types.