The current process

The initiative party of a new BRP is a municipality. In most cases there is a client versus contractor relation. A municipality contracts a consultancy or engineering company (the experts) to compose the calculation models for the BRP. Large municipalities (e.g. Rotterdam or Almere) have their own

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knowledge and experts for composing calculation models in order to perform a BRP. The municipality adopt to the role as policy-maker in this process of composing a BRP. Important to acknowledge is that these policy-makers are often also responsible for composing the GRP, which defines the requirements of the BRP. Result of a BRP is to determine improvement measures where the sewage system does not meet the requirements. This generates (financial) input for the GRP. Because the BRP and GRP are in most cases conducted by the same people, the policy-makers are often also the decision-makers. The eventual consideration of which proposed measures will be carried out and which not is decided by the decision-makers based on the BRP and GRP. (Deckers, 2014)

The need for a new BRP follows from current state of affairs within a municipality, which could be summarized in the considerations according to ‘Module C1000 – Opstellen Basisrioleringsplan’ (Stichting RIONED, 2008) in Text box 2. When the need for a new BRP is determined, the process of formulation a new BRP is given in Figure 42. The goal of a new BRP is to get insight in the hydraulic and environmental functioning of the sewage system in the current situation and in the close and distant future. For example in the BRP of the municipality of Assen (Nelen & Schuurmans, 2008) three scenarios are defined; for the current situation, the 2015 situation and the 2050 situation. Within a municipality the strategic advisor gives the sewage manager the order to define a new BRP. Dependent on the size of a municipality the sewage manager conducts a BRP or outsources this to a consultancy or engineering company. The average processing time of composing a BRP is 3-12 months and will in most cases be conducted before the start of the GRP set-up. However in some cases it could be beneficial to conduct a BRP and GRP parallel to each other (e.g. in the case of important policy adjustments).

In the process of BRP formation, alignment with other (external) parties and other planning forms is important for up-to-date information exchange and using technical models. In Figure 42 is indicated which intern and extern parties are involved for information exchange and in which process step(s) they are involved. In step 2 (Text box 2) of the process is considered which other plan forms (next to the GRP) need to be taken into account in the formulation of a BRP, and which external parties need to be contacted to gain this information. In step 3 the assumptions of the BRP are formulated in accordance with other plans of influence on a BRP (Text box 2). Think about plans like the land use plan, a (municipal)water plan, an integral area-analysis [Dutch: integrale gebiedsanalyse (IGA)] or a wastewater optimization study [Dutch: optimalisatie afvalwaterstudie (OAS)].

In the current process of BRP formulation hydraulic models are used, together with measured situations and reports (e.g. complaints from citizens) to calculate the hydraulic functioning of the sewage system (both in normal and extreme circumstances) and to calculate effects of (possible) measures. For example in the BRP of the municipality of Assen, The Netherlands, a precipitation- discharge model and an integrated hydraulic model is used (modelled in SOBEK) to calculate the hydraulic functioning of the sewage system (Nelen & Schuurmans, 2008). The BRP consists largely of results of calculations together with graphical representations of relevant situations.

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FIGURE 42: THE PHASED PROCESS OF BRP FORMATION, INVOLVED PARTIES AND MODEL USE (ADAPTED FROM FIGURE 3.1 IN LEIDRAAD RIOLERING - MODULE C1000 OPSTELLEN BRP (STICHTING RIONED, 2008)).

TEXT BOX 2: EXPLANATION OF PROCESS STEPS FOR COMPOSING A BRP, ACCORDING TO LEIDRAAD RIOLERING – MODULE C1000 OPSTELLEN BASISRIOLERINGSPLAN (BRP) (STICHTING RIONED, 2008)

Step 1: Is the formulation of a new BRP necessary? The following considerations apply:

 Could important changes in size or structure of (sewage) systems be observed compared to the previous BRP?  Are there indications of dysfunction (like (ground) water nuisance, odour nuisance, etc.)?

 Have there been changes in the requirements of functioning of the sewage system (leading from GRP, permit requirements or legislation)?

 Are important changes expected in spatial planning, for example indicated in the land use plan?  Are areas without a BRP present, or areas which are not included in the current BRP?

Step 2: Is all data available and up-to-date?

 Check the data on quality: accuracy, reliability, completeness, timeliness, and consistency  Are policy principles clearly quantified in the GRP?

 Is data about systems from third parties available (like surface water levels and pump capacities)  Measurement data if any

 Register of complaints/reports

 Which other plan forms need to be taken into consideration or need to be connected (other than GRP) when formulation a BRP. Think about a land use plan, (municipal) water plan, integral area-analysis or wastewater optimization study

Step 3: Define assumptions

 Which works are under construction or will be implemented within the GRP period?  Define the time-horizon of the BRP in conjunction with the GRP

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 Collect all relevant plans which are of influence of the BRP. Think about a water plan, land use plan, wastewater optimization study, integral area-analysis, water quality norms and measurement plans

Step 4: Define the draft-BRP

 Where necessary: conduct a (re)assessment of the data and assumptions for the BRP  Describe the current situation: which systems are present and on which place

 Describe the current functioning of these systems based on reports, measurements and model calculations  Determine, if yes, where, how, and to which extent these systems do not meet the requirements as defined in

the GRP

 Compose a list of possible measures to fulfil the functional requirements Step 5: Check the draft-BRP

 Test the draft-BRP with the requirements of the GRP  Test the draft-BRP with the water plan

 Test the draft-BRP with the land use plan

 Test the draft-BRP with the wastewater optimization study, if present Step 6: Determine and distribute the BRP

 Make the BRP final

 Distribute the BRP intern and extern. Intern: department of spatial planning, department of management and executive department. Extern: water manager(s)

6.3.

OPPORTUNITIES AND BARRIERS FOR USING 3DI IN COMPOSING AN