Construction phase

In previous phases the problem definition, project scope, project strategy and design have been addressed. The construction phase elaborates and discusses the project execution approach. EDD can be used to optimise the work method and the selection of materials.

Important aspects to consider involve:

  • Optimisation of the work, selecting appropriate equipment and materials, timing of activities, etc.
  • Optimisation of the design taking a lifecycle perspective.
  • Application of adaptive construction methods to manage unpredicted direct (and if possible indirect) effects.
  • Involvement of stakeholders, information provision and receptiveness to suggestions.
Building with Nature approach
Eco-dynamic projects aim to jointly optimise the cost-effectiveness of a project, its embedding in the natural environment, the use of natural processes and the creation of new opportunities for nature. Careful selection of materials and optimisation of the layout can yield significant advantages. Involvement of stakeholders in this optimisation process may help to turn hesitation and opposition into enthusiasm and cooperation. Room for experimentation and adaptive project development and management are important elements.
Traditional approach
Traditionally projects are optimised in the construction phase by minimising construction time, costs and risks. Delivering the required functionality within these constraints is considered optimal. Aspects considered are reuse of materials that can reduce construction cost, cost-effective timing of construction activities, functional combinations with other projects, financial constructions, optimising of operation and maintenance with design aspects. There is a tendency to use proven technologies in order to reduce risks.


A variety of EDD optimisations is possible in the Construction Phase. What works best varies from site to site. Reducing construction costs can be favourable in one situation, whereas construction times may be critical in another. Careful timing of construction activities, considering aspects such as the breeding season, may reduce environmental impact. Also (minor) adaptations to the project design may enhance the potential for ecological development.

Examples where EDD has been applied in the construction phase are:

  • Ecological borrow areas: (for 2nd Port Extension of Rotterdam): adaptation of the work method resulted in a seabed landscape with enhanced (re)colonisation capabilities.
  • Hard Eco-constructions: application of specific near natural materials/variation of sorting and material choice led to increased habitat diversity. Smart re-use of old worn-out materials further enhances the ecological value of hard structures by providing a less smooth and more suitable substrate for flora and fauna.

It is important to realise that the people handling the construction phase are seldom the same as those that handled the previous phases. As a result, a lot of important knowledge acquired in these previous phases but required for the construction phase may be lost. This is especially the case between the design and the implementation phase of a project when the project team is often completely changed. Knowledge transfer from phase to phase is very important to obtain optimal results. This can be achieved by adequate documentation, but personal communication in a project setting works best. Even better is involvement of team members that were also active in previous phases.

This chapter provides guidance on eco-dynamic construction approaches. Where appropriate, we suggest useful methods and tools.

Financial engineering

Financial engineering starts early in the Planning and Design phase involving especially those that take the project initiative and are expected to make the necessary investments. Nearing construction final commitments need to be made, guaranteeing the budget that is needed to build the project and to ensure proper operation and maintenance.

The form of contracting is an important related aspect, since it determines:

  • the allocation of risks between the contractor and the Clients, and how these risks are financially valued;
  • the functional or more technical specifications that may allow for slightly different or even completely different project proposals;
  • the way in which Operation and Maintenance is made part of the contract or contracted separately;
  • the extent to which Client and Contractor will be jointly responsible for the project execution and will jointly reap the benefits and bear the costs;


When shifting from Planning and Design to Construction, one should focus on the following aspects:

  • It is important that designers clearly transfer full information (data, intentions, considerations, choices, options) to constructors.
  • Make sure that constructors have sufficient time to familiarise with the project context and environment and the new ideas to be implemented.
  • Involve sufficient ecological expertise in the construction lay-out. There is a tendency to work with teams that mainly consist of engineers and to consider ecology as having been handled in the previous phases. It is however important that ecological expertise is involved in the construction phase, not only because much optimisation of the construction work depends on natural processes and ecological effects, but also because ecological effects often can be optimised during construction.

It is advisable for (BwN)projects to involve constructors already in the P&D phase, in order to warrant construction-efficiency of the design.

Decision making and also contracting is also about financial engineering, i.e. developing financial mechanisms and commitments that ensure the proper allocation of costs and benefits over different parties, phasing of investments and benefit streams over time, valuation and handling of risks and appropriate contracting and budgeting.

Step 1) Understand the system

In the BWN approach a good understanding of the system in and with which the project is to be realised is paramount and a first step. It has already been an important activity in the Project Initiation and Planning and Design phases. In the construction phase other experts will look at the project from different angles with more emphasis on technical and commercial aspects and practical implementation. Also environmental issues remain important, in relation to license requirements as well as the environmental effects during execution.

BwN approach
In the BWN approach the design and the way in which it is realised are optimised with respect to all system aspects. Apart from keeping costs and environmental impacts within acceptable bounds, also ecological and economic benefits are important. Timing of the work in line with natural processes may be an issue, as well as adaptive management of risks and opportunities.
Traditional approach
The Scope of Work describes the building activities and the envisaged result. The focus is on a simple and cost effective project meeting environmental requirements. Understanding processes is limited to those relevant to the cost-effective execution of the work. Less attention is paid to processes relevant to Operation and Maintenance, because this is usually not part of the contract.

Since BwN-type projects take place in dynamic ecosystems, it is recommendable to update the information on the existing state right before execution. This update may involve items such as coastal profiles, habitat inventories, state and presence of protected species. It is also important to involve stakeholders that may be confronted with effects that take place during the execution of the work. This will enable working methods that will limit effects on businesses, access to premises etc. There may also be useful new information from reference monitoring programmes and pilot projects that were started in order to study specific aspects of projects.

This update is important as baseline information for the contract and contribute to a cost-efficient design and execution of the work. Such baseline information may be made available by the client, but often the contractor retrieves extra information in order to refine his working methods and cost estimates.

On top of this baseline information on the actual state of the system, additional information comes available, for instance on the geological setting of the project and the availability of natural resources. This information can be used to optimise the working method, but also to refine and update the final design.

Socio-economic effects have played their role in thee design and decision making phases leading to the preferred alternative, but stakeholder involvement does not stop there. During execution the project becomes visible to the stakeholders and the public at large. Publicity may influence public opinion and stakeholder positions. Stakeholders can play a crucial part in further optimising and supporting mitigating measures during execution. There are contracting procedures which explicitly address this dimension. Moreover, much needs to be detailed, discussed and decided in this phase for which interaction with stakeholders is vital.

Step 2) Identify realistic BwN alternatives

The previous phases have defined a design and scope for further optimisation (see Next phase from previous chapter). Modes of operations and innovations can be elaborated in this phase. In the previous phases, the EDD process has led to the identification and selection of a preferred alternative. Work in this phase will focus on optimising implementation. Yet, this may feedback on the design and forward on operation and management.

The optimisation of design and construction principles involves:

  • Translating optimal modes of implementation (see below) into the design itself. If for example the implementation can be made more cost effective by making use of natural processes, this may require a more natural alignment of the contours of the work than originally designed. In the case of a mega-nourishment more comprehensive information on the type of sand available, may lead to the differentiated use of sand fractions in order to have a better performance during construction. Often the Planning & Design phase focuses on the end result and does not consider intermediate construction stages, implicitly leaving construction issues to the contractors. These possible feedbacks mean that a two way transition between the P&D-phase and the construction phase is needed.
  • Full potential of phasing. Many marine engineering projects involve several phases that deal with different parts of the work and construction may take many years. Often optimisation is possible depending, for instance, on the availability of equipment, the response of natural system, the possibility of creative re-use of materials, etc. This, too, may have implications for the design.
  • Exploiting win-wins. The contracting party may see other win-wins, for instance with other ongoing projects in the vicinity, or because of the availability of special methods, techniques or equipment that were not foreseen in the Planning and Design phase. Possibly there are also win-wins to be made with stakeholders that have not been involved so far. Win-wins may relate only to a cost-effective execution of the existing design, but they may also require a modification to the project scope.
  • Contract adjustment. Depending on the extent of change and the type of contract, changes in the design can be handled within the existing contract or agreement; or renewed contract negotiations between client and contractor are required. In a shift in scope may affect the interests and responsibilities of third parties and will require also re-negotiating and new agreements.
  • Mitigation planning. Larger projects often affect the environment, the functioning of nearby infrastructure, nearby economic activities and nearby living conditions (noise, traffic, dirt, etc.) Work optimisation seeks to mitigate these effects by taking proactive measures, such as providing temporary access roads, or working outside critical periods. Often work is often phased taking into account breeding or spawning seasons of critical animals, or periods when the ecosystem is less vulnerable.
  • Use of innovations. Depending on the kind of work, the contractor may also put forward novel ways of working, that were not foreseen in the Planning and Design phase. The strengthening of the Delfland coast was partly executed by bringing sand directly into the surf zone via pipes, instead of using only beach and foreshore nourishment. Another example is the use of eco-structures as part of the Case – Eastern Scheldt dike foreshore ecological upgrading and other types of Rich Revetments.
  • Joint optimisation of construction and O&M. Especially in contracts that combine construction and subsequent operation and maintenance, contractors often find opportunities for lifecycle optimisation, in financial as well as ecological terms. Stimuli for cost optimisation are always there, but an incentive to optimise on ecological aspects needs be vested explicitly in the contracting and rewarding procedure. In the Maasvlakte 2 project comparatively steep sandy shores were built, that involve more maintenance, but are expected to be more cost-effective from a lifecycle perspective. In addition they act as a source of nourishment for the adjacent shallow sea.

Optimal modes of construction process implementation may focus on:

  • The use of natural processes for/in implementation. In the case of coastal nourishment, working with tides and wave-driven currents is an important aspect to be elaborated. In general the capacity of the natural system to contribute to project implementation may determine the most cost-effective and environmentally benign way of implementation.
  • Positive/Minimum environmental impact during execution. Special modes of operation and timing (e.g. environmental windows) may be used in order to limit or even reverse the environmental impact of a project. Especially working close to or in protected areas may require special techniques in order to minimise impacts (e.g. sound, light, emissions, turbidity).
  • Adaptation on the go. Also during the execution of the work it is important to monitor critical parameters , since optimisation of the workflow or even of the design may still be possible or necessary. One can predict possible effects with models, but measuring actual processes and effects, if possible extended with a model-based projection into the near future, is to be preferred. The Øresund Fixed Link project is an example of how this may work. In the different stages of implementation the effects on the flow through the Øresund (the Sound) – a critical aspect – were closely monitored and any reduction was immediately compensated by additional dredging. If uncertainties are large it may be advisable to start up execution slowly and monitor intensively, in order to enable optimisation at an early stage of implementation.
  • Flexibility in re-use of materials. There are many engineering projects that produce residues, such as dredged material, which can be used elsewhere in nature development or restoration projects, for instance. During project implementation one gets a better overview of the materials that become available, which may lead to a different re-use. One may also take a learning by doing approach in the construction of compensation and nature restoration projects with dredged material.
  • Dedicated and optimised monitoring. Monitoring of environmental parameters is often compulsory and a good monitoring plan is part of the implementation plan. The contractor may propose alternatives, based on more reliable and cost-effective modes of monitoring than originally planned, for instance by focusing on critical issues and locations only. Moreover, there are always possibilities to improve the monitoring plan on the basis of observed processes and data.. Identifying opportunities for optimisation may require dedicated monitoring, which should be made possible in the monitoring plan.
  • Dedicated environmental standards. Improved monitoring and system knowledge enable defining more meaningful environmental standards, trimmed to the situation and the kind of work at hand. Often a generic set of standards is used, which may fail to safeguard critical environmental processes and habitats in the specific situation, or are stricter than necessary and lead to unnecessary costs and delays. Real-time monitoring of critical organisms may show that more stringent standards are needed, or that standards may be relaxed. Real-time species monitoring was part of the Øresund monitoring plan, for instance. Yet, adaptive monitoring will seldom lead to relaxation of standards, only to an adapted extent and frequency of the monitoring.

Step 3) Evaluate and select alternatives

A Social Cost Benefit Analysis is the tool of choice in the planning and design phase, since it covers all the issues that are important to (political) decision making. Similar assessments are used to evaluate proposals, but can also be used to rank tender documents.

Normally contracting procedures involve award criteria, which should ideally meet the following conditions:

  • They correspond with the most important criteria in the decision framework used in the Planning and Design phase. The same main aspects should drive design and decision making in all project phases. Possibly, these criteria can be made more tailor-made and meaningful as the project progresses.
  • They cover all requirements set by authorities as well as legislation. It is important that licences and permits give room to optimisation and are not so stringent that they preclude better alternatives. As has been discussed in the Project Initiation and Planning and Design phases assumptions and prerequisites need to be tested to see whether they are indeed relevant and correct.
  • They work as environmental incentives, i.e. they are formulated in such a way that they stimulate optimisation on environmental aspects as well as on costs (see contracting aspects).

In the Netherlands a form of Best Value Procurement exists under the name of EMVI (Economic Most Viable Proposal). EMVI is used to assess, compare and select the best proposal. Costs are always important, but also quality criteria play an important role. These quality criteria can be related to environmental as well as socio-economic, cultural, landscape or risk management aspects.

The EMVI system may work well as an incentive to better creative and beneficial solutions or alternatives, using the ingenuity and creativity of contractors, within the indicated range of freedom. However it is difficult to stipulate functional specifications and requirements in such a way that the intention of the Client and the interpretation of the Contractor are close to one another. The match between both can be improved by a combination of system engineering and explicit validation methods and by an active dialogue between Client and Contractor on the interpretation of set specifications and requirements.

The next elements deserve particular attention when following a creative approach in this project phase:

  • Added value that can be achieved for nature; sometimes explicit options are indicated, such as the re-use of dredged material, but the key question is what the project adds to nature, taking into account also the legal, costs and stakeholder implications. Proposals that include nature-friendly options are less problematic than proposals in which the creation of nature is an essential functional element of the design and not just an additional benefit. Such a proposal may significantly differ in scope and fall outside the range of possibilities explored and discussed with stakeholders. This makes it politically risky and also the contractor takes an additional risk in proposing such a different solution. There are examples of good managed contracting procedures that also allowed (limited) alteration of the scope of work, without leading to substantial delays.
  • Cost optimisation beyond the phase of construction; in principle costs and benefits of this can be shown in a lifecycle-based Cost Benefit Analysis (CBA). This can be included as a criterion in a best value procurement. Ideally this is done on the basis of a wide set of ecosystem benefits and not only on investment and OM costs.
  • Risk management directed at uncertain elements and assumptions in the design. This incentive favours more robust and flexible solutions. In practise it is difficult to value the benefits of a more flexible solution. An assessment of the potential performance of a design under a bandwidth of scenarios may be needed, and also be prescribed as part of the verification procedure.

The underlying problem/challenge is how to make these criteria SMART so they work as an incentive, but also as a means of environmental optimisation. Sometimes this is solved by defining an environmental quality reference that is based on a maximisation of environmental benefits/aspects, which is discussed with stakeholders prior to the contracting procedure. It can be SMART to make a distinction between a set of functional requirements and a set of desired specifications that can have the form of a reference design that has been consulted with stakeholders.

Step 4) Elaborate selected alternatives

During the tendering or contracting period, the contractor and the client may agree upon the preferred final design and the way it will be implemented.

In their further elaboration special attention should be paid to:

  • Detailing the work method and the project plan: clear definitions of intermediate construction stages, materials to be used and workflows. This involves a detailed timing of work in order to limit effects on habitats and protected species.
  • Project organisation and quality assurance program, at the contractor’s as well as the client’s side; a fixed and rigid structure will hamper flexible and open ways of working, based on adaptive monitoring, for instance. It should be possible to pro-actively implement interesting but unforeseen options, even if this would lead to amendments to the contract; the QA-program should secure the quality of such choices.
  • Environmental management & monitoring plan, including an inspection and test plan: it is essential to decide well before the start of the works which parameters are going to be monitored, how and for what purpose, and how the resulting data are going to be processed, presented, analysed and evaluated; moreover, one must identify adaptive or corrective measures that can be taken if necessary and agree on how and when they will be taken.
  • Environmental inspection and test plan: to be agreed with the client and the relevant stakeholders, for the sake of openness and clarity in the environmental management.
  • Adaptive management procedures. These procedures are closely linked to the monitoring plan. Adaptive measures can be taken during construction, or they can be part of the Operation&Maintenance Phase.
  • Stakeholder involvement: even during construction there are good reasons to involve stakeholders, for instance in design optimisation and work planning. Local residents, but also nature management organisations and municipalities will have valuable local knowledge.
  • Communication strategy: project execution requires timely information of the public; in BwN-type projects it is advisable to pay due attention to the natural processes, including the uncertainty they involve. Also, successes as well as unexpected developments should be communicated openly.

Next action will be that the project Organisation – Contractor and Project Owner jointly – assure that the works are executed as intended, as specified in above plans. Adherence to these principles requires close management monitoring, and adoption or adjustment of plans and procedures when required.

Step 5) Next phases

After finalisation of contractual and organisational matters, the execution of the work can start. This also means that the next phase, operation and maintenance, comes within sight.

Apart from the usual workflow management, important points of attention are:

  • Monitoring environmental effects: more than in mono-functional projects, BwN-type projects require monitoring of the environmental effects – positive or negative – during execution. In order to enable an adequate response, it is important to process the data right after acquisition and translate them into usable management information.
  • Keeping stakeholders and the public informed of the progress during execution. It is important not to stop informing the public at the end of the Planning and Design phase, even if it is no longer legally required. The use of modern communication media is recommendable.
  • Preparing for O&M procedures. A BwN-type project does not end at handover of the completed works, since the response of the natural system will take much longer to develop. This response will have to be monitored, and, depending on the situation, management and maintenance may be necessary. As nature is largely unpredictable, this management will always be adaptive. If the system is actively operated, like in the case of economic activities, this may interfere with the natural system. Monitoring is needed to assess whether this remains within acceptable bounds. Ideally O&M procedures and agreements are established prior to project execution, but this should not exclude revision and optimisation on the go.