**4. Decision Support System and Type of Contract**

A significant increase in the size of the plants has been observed due to technological development and the effect of economies of scale. The bidding process, financing, the selected type of contract, the operation, and maintenance are the key factors for the achievement of the objectives set in the development of a desalination plant. This situation makes these plants increasingly complex, making the choice of contract decisive.

At the end of the 20th century, the type of contract for projects in question was part of the selection process and professional advisors in the sector proposed contract models that helped investors find the best contract for each specific project. These decision support methods or systems are known in the international market as "Decision Support Systems" (DSS). There are numerous authors who have proposed different methods, such as Gordon [52]; Bennett, Pothecary, and Robinson [53]; Molenaar [54]; Konchar and Sanvido [55]; Ibbs et al. [56]; Gransberg, Koch, and Molenaar [57]; Hale et al. [58]; Touran et al. [59]; Park and Kwak [60]; Sullivan et al. [61]; and Jiyong, Wang, and Hu [62].

From among the numerous decision support systems, authors have proposed the method of determining factors [63], published in 2020: (1) client, (2) contractor, (3) contract, (4) budget, (5) financing, (6) risks, and (7) technological developments. It offers a procedure which adapts to any kind of project, specially indicated for large-scale infrastructure projects.

This method consists of the quantitative and qualitative evaluation of the mentioned factors. The qualitative evaluation analyzes the client and contractor capabilities, the suitability of the contract and the assignment of responsibilities, the feasibility of budget compliance and financial availability to meet payments, the risks of the development of the project, and the technological innovations implemented. The quantitative evaluation consists of assigning a score from 1 to 5 to every determining factor, with an increasing value the higher the degree of compliance. The method that will indicate the degree of compliance of each determining factor is applied to each contract modality, so that the higher the score, the more suitable the type of chosen contract will be to develop the project.

The international industrial construction market has great dynamism, which leads those involved in the project to look for new contracting formulas which adapt to their needs, in order to carry out the project. It is normally done by combining other types of contract or modifying the existing ones according to said particular needs. Many authors have written about the most used types of contracts and their differential characteristics, such as El-Wardani, Messner, and Horman [64]; Ohrn and Rogers [65]; Hinze [66]; Chamarro [67]; Franz et al. [68]; and Farnsworth [69].

Therefore, updating the list given by Hernández [70], the most used types of contracts are summarized below:

(a) Traditional contract or "Design then bid" or "Design Bid Build" (DBB). This implies the participation of at least three parties: client, engineering, and contractor. From the legal point of view, it is structured on the conclusion of two contracts: one between client-engineering, and another between client and contractor. This results in the division of the project into design and construction phases. The construction will start once the project is completed. The client uses this method when they feel more confident about a completed project.

(b) Accelerated construction process or "fast track construction". This contract allows construction work to begin before the project has been drawn up completely. It implies a fragmentation of the project into different phases. From the legal point of view, the accelerated construction process can be structured on the basis of: (1) separated contracts between the client and each of the parties involved in engineering and construction; (2) a traditional construction contract; (3) a design and build contract (DB), in which case the contractor will be responsible for the design and the construction; or (4) a Construction Management or Project Management contract. From these contractual formulas, the best suited, considering the fragmentation of the project, are the last two, which will be discussed later.

(c) "Project Management". This attribute the functions of supervision, direction, and coordination of the project as a whole to an entity, called the Project Manager, which through their services, tends to get maximum control and a consequent reduction in the time and costs involved in the execution of the work. Compared to the traditional method, it involves the participation in the process of a fourth party, which assumes certain functions which are usually attributed to the client, the engineer and/or the contractor.

(d) "Design and build" (DB) and turnkey contracts imply a progressive expansion of the obligations assumed by the contractor. It involves that the general contractor is tasked with gathering a group of designers and constructors to carry out the work. In the late twentieth century, English/American law had a great influence in the international arena of contracts. Thus, through the design and build contract, the contractor undertakes to conceive and execute the industrial project in accordance with the needs and requirements of the client. Therefore, the benefits derived from this contract are limited to the construction operation itself. Obligations outside the contract, such as the commissioning of the installation or the training of personnel, are not included in its content, as in the case of the turnkey contracts.

Based on this difference in content between the two contracts, it can be claimed that while a design and build contract can never be equated to a turnkey contract, a turnkey contract, however, always includes the obligations derived from the design and build contract—something that is understandable, considering that, in the international arena, the design and build contract has served as the basis for the configuration of international turnkey contracts. Similarly, both contracts have been the benchmark for the creation of other contractual forms, such as the turnkey product contract and the turnkey market contract.

(e) BOT and BOOT projects. The formula BOT (Build-Operate and Transfer) as well as the contracts called BOOT (Build-Own-Operate and Transfer) are different mechanisms used to finance projects (Project Financing) of mainly infrastructures or public works, through which the public sector has been transferring to the private sector. Traditionally, this was an activity in which the public sector took charge drawing on its own financing.

(f) "Engineering" contracts. Through these contracts, a party (the engineering company) subcontracts another party (called client) to develop manage and supervise a project, and when agreed, depending of circumstances, other obligations, including the maintenance and management of the finished work. Despite the fact that in business practice, the engineering contracts may include different content, a common denominator is observed: they all have an obligation for results. Be it simple or global, whether it involves the development of a project and/or its execution. The contractual compliance is borne by a business entity in which the activity of the individual professional is depersonalized.

(g) "Engineering, Procurement, and Construction Management", also known by its acronym EPCM, which means that in this type of Engineering Contract the Contractor will provide the Client with Engineering Services, Purchasing Management, and Construction Management. In the EPCM contract, the Contractor develops engineering, processes acquisition, and manages the work on behalf of the Client, but does not construct the project. The Contractor, thus, becomes a representative, working hand in hand with the Client, and managing the contractual relations with Suppliers and Contractors. In this way, the Client will be ultimately responsible for the acquisitions and approve all contracts. Thus, the construction risks fall on the client.

(h) "Open Book Estimation", OBE. An OBE contract consists of an agreement between Property/Client and Contractor to carry out work in which the costs are reimbursable to the latter, plus a previously agreed margin. Client and Contractor also agree on how to pay for the works. This type of contract has become important in recent years and has been generalized as a previous phase to the award of a turnkey contract for large industrial installations.

(i) "Progressive Design-Build", PDB, is an emerging variation of alternative contracting methods, which allows the client to hire a project and construction contractor without a price commitment until reasonable design details are defined. They have been used for water treatment plants and for airports. The critical issues are: what responsibilities are transferred to the contractor, the need for the client participation during the design and the provision of cost saving measures that do not jeopardize the quality of the project. Gad el al. [71] and Gransberg and Molenaar [72] have studied this new type of contract.

In the area of desalination, the turnkey contract stands out as the most proven and efficient tool for the development of projects, offering the following advantages:


It is advisable to introduce a phase in the modality of open book estimation, prior to hiring, that allows designs and prices to be adjusted and agreed, which will reduce project risks, contingencies and deviations during the construction, leading to a better final result. This modality has been successfully offering the solutions given in the mentioned PDB.
