How are urban sewerage systems designed and implemented?

The process is divided into eight chained stageseach with concrete deliverables and validations:

Phase	What is done	Key aspects
Diagnosis and planning	Inventory of the existing network, LIDAR topography, flow gauging and demographic projections.	Defines the design flow rates and the scope of the project.
2. Hydrologic-hydraulic modeling	Storm simulation (T = 2-50 years) with EPA-SWMM or other software.	Optimizes diameters and estimates relief flow rates (CSO).
3. Preliminary layout and dimensioning	Establishment of starting and discharge elevations, minimum slopes, manholes and critical points.	Check self-cleaning speeds.
4. Selection of materials and structures	Choice of pipes (concrete, PVC, GRP, HDPE) and of pumping stations, spillways and storm tanks.	Complies with UNE-EN 752 and local ordinances.
5. Detailed engineering	Plans, reports, specifications, easement management, EIA and permits.	Defines whether certain crossings will be executed with microtunneling.
6. Construction	Open pit excavation or trenchless methods (ramming, microtunneling) in critical areas.	Reduces traffic cuts and service relocations.
7. Testing and commissioning	Tightness tests, CCTV, cleaning, disinfection and meter calibration.	Guarantees operability before final filling.
8. Operation and maintenance	O&M plan with inspections, preventive cleaning and real-time flow control (RTC).	Minimizes overflows and prolongs service life.

Why incorporate microtunneling?

In sections under riversroads or urban centersmicrotunneling avoids deep trenches, reduces traffic diversions and maintains slope accuracy, while protecting the pipe against dynamic loads and external corrosion. Thus, the design must reserve bending radii, attack and arrival shafts adequate to the diameter of the TBM.