Tasking and Budget Estimates

• Lower band assumes:

• • Favorable rates for site investigations;

  • Re-usable material freely available;

  • No significant investments needed to mitigate geotechnical risks; and

  • Settlement does not impact maintenance significantly.

• Middle band assumes:

• • Normal rates for site investigations;

  • Re-usable material available but some investments needed to procure;

  • Investments needed to mitigate geotechnical risks; and

  • Maintenance needed to cover for settlement.

• Upper band assumes:

• • Site investigations expensive;

  • No re-usable material available, needs to be directly supplied;

  • Significant design impact to mitigate geotechnical risks; and

  • Maintenance needed to cover for settlement.

In relation to these, the RHDHV, in coordination with the local stakeholders, provided the details for the conceptual budget estimates to include sub-project details as follows:

• Design, construction, and maintenance:

• • Detailed engineering design. Detailed engineering design (DED) is important as the pilots needed to be designed properly to function during their design life. These include site investigations, model studies, and drawings among others.

  • Permitting. It is deemed necessary for the budget estimate to provide for the costs related to the payment for permits, area clearance, and other assessments related to the project.

  • Procurement. The procurement procedure will need to align with the general procurement rules from the contracting entity/government agency from the finalization of the conditions and specifications of the contract to tender award.

  • Construction of the Bagna-Panasahan green embankment and Pamarawan sediment trapping, breakwater, and green embankment. In addition to the construction components, it is assumed that the project management for the construction and supervision of the pilot projects will be combined for the two (2) locations.

  • Project management. During this phase, costs related to project management including the guidance and supervision in the realization of the process will be accounted for.

  • Maintenance of the project components. It is also taken into consideration that maintenance for five (5) years are accounted for. Among the items under the maintenance components are settlement monitoring, sedimentation/erosion monitoring, and mangrove growth monitoring, among others.

For the next phase of the project, the following tasks are seen to be undertaken by the Project team:

a. Site investigations: Soil investigations

As the pilots will be constructed on existing (unconsolidated) soil, geotechnical investigations need to be carried out to allow the DED to properly classify the soil underneath the pilot locations. Expected soil investigations are boreholes and subsequent laboratory testing in the most relevant parameters. 

It is important that the contractor carrying out the investigations uses appropriate standards and workmanship, which should be set-out in the Terms of Reference, prior to contracting the contractor. This is seen to be supervised by experts.

b. Site investigations: Sediment samples/ADCP campaign 

The effectiveness of the sediment traps will depend on the availability of the amount of sediment in the water column and the flow velocities (or impact of the traps on the existing flow velocities). Sampling the existing presence of sediment in both the water and seabed is an important baseline for the design. As is, monitoring flow velocities is to be done over at least a two (2)-month period. Ideally year-round monitoring would be available, but that will not fit the schedule. It needs to consider the flow velocities in wet and dry seasons with the main differences in daily conditions. Flow velocities can be measured using ADCP or other type of survey equipment. It is important that the contractor carrying out the investigations uses appropriate standards and workmanship, which should be set-out in the Terms of Reference, prior to contracting the contractor. The results of these investigations shall be checked by experts.

c. Site investigations: Bathymetric and topographic surveys 

As input for the design elevations of the existing seabed and adjacent lands near/around the pilot locations are needed. This will need to be a combination of a bathymetric (e.g., river profiles) and topographic (e.g., shallow and land areas). It is important that the contractor carrying out the investigations uses appropriate standards and workmanship, which should be set-out in the terms of reference, prior to contracting the contractor. 

d. Numerical model studies 

For the pilot locations, which are exposed to open water, sensitivity on the effectiveness of the sedimentation numerical model studies will give input to the design. Most important outputs include: 

• Waves and surge during typhoon conditions; 

• Flow velocities during daily conditions; 

• Flow velocities during daily conditions with pilots implemented; and 

• Sedimentation during daily and pilot conditions.

For the green embankment/dyke design river water levels are an important design input, but the creation of such a model will be require (very) detailed inputs, which are not available. River water levels would be acquired via literature or through the City of Malolos data. The results might be given in bandwidths, which imply that the Malolos LGU need to consider the calculations with the upper band costs.

e. Basis of Design 

The basis of outlines the fundamental principles, criteria, and design parameters for the DED. It includes project objectives, design standards, environmental considerations, materials, and any specific technical details crucial for successful project planning and execution. In addition, results from the previous studies and surveys will be translated into design inputs. The materials available for the construction of the pilots will be set including the stakeholders that need to be involved. 

f. Detailed Engineering Design (DED) 

With the basis of design completed the DED will, amongst others, consist out of:

• Green Embankment/Dyke 

• • Geotechnical calculations for the green embankment/dyke focused on slope stability during static and seismic conditions;  

  • Geotechnical settlement calculations to identify how much consolidation of the subsoil is needed during construction;  

  • Any ground improvement/slope stabilizations methods needed which are required to work with the available materials; and

  • 3D geometrical models/quantification

• Sediment trapping 

• • Design of the sediment traps, sensitivity analysis in combination with the numerical model; 

  • Material usage; and 

  • Phasing/setup various pilots (with and without added sediment, with and without planted mangroves etc.) 

• Enchanted breakwaters 

• • Materialization, which (commercial) elements are in available in the market;

  • Calculation of wave transmission/reduction; and

  • Submerged vs. Elevated data