Methodology Adopted for Analysis;-
The Study was conducted to define and understand the current problem of waste disposal in Ranchi and to suggest best possible sites for waste disposal. We have used RS and GIS techniques to identify and selection of such sites. As we know that modeling process of analysis gets enhanced by GIS , which can be further combined in meaningful sequences to develop new models. There are number of methods available to tackle problems like selection of waste disposal site. One of the problems in decision theory of multi-parameter analysis is the determination of the relative importance of each parameter. The site selection for solid waste disposal facility involves comparison of different options based on social evaluation of each of them for detailed environmental, social and community impact. Thus the problem requires human judgement at all levels. Hence based on experience and likely impact on surrounding environment different weights were assigned to all the parameters.
In order to achieve the objective sets for, the cross parameter relationship method has been adopted in which weightage of different parameters were assigned on the basis of their importance (Table-1). This methodology comprises the following steps: -
- Selecting criteria for evaluation of sites.
- Apportioning a total score of 1000 among the assessment criteria based on the importance.
- Developing Site Sensitivity Index (SSI).
- Estimating score for each parameter for various sites alternatives using SSI.
- Adding the score for individual site alternatives to rank the alternatives based on total score.
- Classification of the site based on final score.
Based on extensive study, following parameters were used for the selection of solid waste disposal sites: -
- Depth of bedrock.
- Slope of the ground.
- Type of rocks present in the area.
- Structural feature of the area.
- Water table depth in meter.
- Fluctuation of water table in meter.
- Distance of surface drainage in meter.
- Ground water yield.
- Soil type.
- Permeability of soil in cm/sec.
- Population around the site in km radius.
- Landuse of the area.
- Distance of the sites from the waste producing units.
- Present Transport route.
- Type of waste.
Table 1: - Criteria with Weightages for Municipal Waste Disposal sites: -
| Criteria | Weightage for Municipal Waste Disposal Site |
| Geological | 280 |
| Bedrock depth | 80 |
| Slope of the ground | 60 |
| Type of rock | 70 |
| Structural features | 70 |
| Hydrological (Surface and Ground Water) | 260 |
| Water table depth | 90 |
| Fluctuation of water table | 80 |
| Drainage distance(m) | 50 |
| Ground water yield | 40 |
| Geotechnical | 80 |
| Soil type | 30 |
| Permeability | 50 |
| Socio-Economical | 380 |
| Population within 1km radius | 90 |
| Landuse | 100 |
| Distance from waste producing units | 40 |
| Transport route present | 30 |
| Distance from Airport | 60 |
| Type of waste | 60 |
In the present study GIS has played a very important task. With the help of Network analysis in ARC/INFO software most economical route for transportation has been computed. The distance between two points along the Road Network was computed through GIS.
Hydrogeological map was interpolated over the entire study area in GIS Environment. Buffer zone was created with the help of available data around the proposed site in GIS Environment.
Table 2: - Rating Parameters with Sensitivity Levels of Various Sites:-
| Criteria | Sensitivity Index |
| | 0.0-0.25 | 0.25-0.5 | 0.5-0.75 | 0.75-1.0 |
| 1. Geological | | | | |
| Bedrock depth (m) | >100 | 100-60 | 60-20 | <20 |
| Slope of the ground | <1% | 1 to 3% | 3 to 5% | >5% |
| Type of the rock | Highly compact (Massive & stable) | Compact | Weathered | Poor & highly weathered |
| Structural features | Without fault and joints | Small fault and joints | More fault and joints | Highly faulted and jointed |
| 2. Hydrological (Surface and Ground water) | | | | |
| Water table depth ( m) | >30 | 30-20 | 20-10 | <10 |
| Fluctuation of water table | <1 | 1-3 | 3-5 | >5 to waterlog |
| Drainage distance ( m) | >500 | 500-300 | 300-100 | <100 |
| Ground water yield | Limited | Moderate | Good | Very good |
| 3. Geotechnical | | | | |
| Soil type | Saline/Alkaline | Rocky stony | With Silt | Alluvium |
| Permeability | <10-5 | 10-5-10-4 | 10-4 -10-3 | >10-3 |
| 4. Socio-Economical | | | | |
| Population within 1km radius | Negligible | Low | Moderate | High |
| Landuse | Wasteland | Agricultural | Residential | Forest |
| Distance fromwaste producing units (Km) | <10 | 10-20 | 20-30 | >30 |
| Transport route present | Rail | Metalled road | Unmetalled road | Nothing |
| Distance from Airport(Km) | >20 | 20-10 | 15-10 | 5 |
| Type of waste | Organic | Municipal | Municipal with small amount of Hazardous | Hazardous |