Figure 1.
Determining the rank of the consequences of occurrence of an emergency in a sewer tunel
| Criterion | Parameter value according to the rank of consequences | ||
|---|---|---|---|
| I | II | III | |
| Technical characteristics of the emergency section (C1)*: | 1500 to 2000 | 2000 to 2500 | Over 2500 |
| Impact aureole of the sewer tunnel on the environment (C2) | Up to 50 m, no pollution of water resources | 50 to 150 m, no pollution of water resources | over 150 m, there is pollution of water resources |
| Population coverage (C3), thous. people | up to 5 | 5 to 25 | over 25 |
| Extent of damage or deterioration and maintenance of temporary (or permanent) wastewater disposal system (C4) | Switching over to the redundant wastewater disposal line | Arrangement of a temporary wastewater disposal system by means of pumps and temporary ground wastewater disposal lines | Inability to arrange a temporary wastewater disposal system and shutdown of water supply |
| Cost of complete elimination of consequences (C5), thous. of € (in equivalent to the national currency in Ukraine) | Up to 20 | 20 to 40 | Over 40 |
| Organizational and technological measures of restoration of sustained operation of the sewer tunnel (C6) | Typical measures to restore the operation of a sewer tunnel | Organizational and technological measures of increased complexity | Innovative measures for the complete reconstruction of the existing tunnel and facilities or construction of new ones |
Group of ecological consequences of emergency occurrence in a sewer tunnel
| Sphere of impact | Nature of impact | Consequences |
|---|---|---|
| Atmosphere | Release of hydrogen sulfide, mercaptan, sulfur dioxide, carbon dioxide, methane and the like | Intense man-caused environmental load, which is a source of significant environmental hazards for urban areas, especially if the exceedance of maximum allowable concentrations for substances of hydrogen sulfide, mercaptan, sulfur dioxide, carbon dioxide, methane and the like [15] |
| Hydrosphere | Penetration into groundwater | Changing the chemical composition of water and the appearance of other undesirable components that threatens environmental safety |
| Penetration into surface water of sources | Dangerous increase of concentrations of substances and pollution of the main sources of water supply | |
| Lithosphere | Flooding of territories and disturbance of water exchange | Increase in the level of groundwater and their aggressivity as a result of feces water contamination causes the impact on existing karst voids, which leads to the formation of karst holes, which threate ns facilities, the deterioration of the body of foundations, corrosion of reinforcement and concrete; deterioration of soil mechanical properties (shear resistance decreases) |
| Soil degradation | Deterioration of soil beneficial properties and fertility due to the allocation of hydrogen sulfide which is highly toxic | |
| Suppression of plant complex | Reduced seed germination, slow growth of plants, abnormal development of root systems, chlorosis, withering, plant death | |
| Contamination of the topsoil with heavy metals | Toxic, even in minimal amounts, heavy metals are not susceptible to decomposition processes, but are only able to be redistributed between natural environments; therefore, they are concentrated in living organisms, causing different pathologies. |
Group of economic consequences of an emergency occurrence in a sewer tunnel
| Sphere of impact | Nature of impact | Consequences |
|---|---|---|
| Macroenvironment of the operating company | The need to allocate additional funds from the budget for carrying out work | Destabilization of the financial environment of the local budget |
| Microenvironment of the operating company | The need to eliminate the emergency | Allocation of funds for temporary stoppage of wastewater disposal, local elimination of consequences of an emergency |
| The need for temporary provision of uninterrupted operation of the wastewater disposal distribution system | Allocation of funds for the installation of a wastewater bypass line, pumping equipment, etc. | |
| The need to overhaul a worn-out sewer tunnel or build a new one | Allocation of funds for the development and approval of the complete set of design, budget and as-built documentation; carrying out construction works for the rehabilitation of an existing or construction of a new sewer tunnel |
Findings of the survey of experts in the field of sewer system
| Item | Criterion | Expert | Score | |||||
|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | |||
| C1 | Technical characteristics of the emergency section | 5 | 5 | 6 | 6 | 6 | 5 | 33 |
| C2 | Impact aureole of the sewer tunnel on the environment | 4 | 3 | 3 | 3 | 3 | 4 | 20 |
| C3 | Population coverage | 2 | 1 | 2 | 2 | 1 | 1 | 9 |
| C4 | Extent of damage or deterioration and maintenance of temporary (or permanent) wastewater disposal system | 3 | 4 | 4 | 4 | 4 | 3 | 22 |
| C5 | Cost of complete elimination of consequences | 1 | 2 | 1 | 1 | 2 | 2 | 9 |
| C6 | Organizational and technological measures of restoration of sustained operation of the sewer tunnel | 6 | 6 | 5 | 5 | 5 | 6 | 33 |