**4. MSW landfill in ditches in Luiz Antônio, SP, Brazil**

In Brazil, sanitary landfills are considered ideal domestic waste disposal sites that are concepted to minimize public health hazard [13]. However, in small towns that produce less than 10 tons of domestic waste per day, waste final destination remains a challenge to the government. In an attempt to improve this situation, São Paulo State Environmental Agency (CETESB) proposed a financial and environmental low cost alternative to waste disposal for towns with less than 25,000 habitants. Landfill in ditches is a technique accepted by the environmental agency

**Figure 12.** 

*Local map with survey lines and sample points.* 

and has been applied for more than 10 years in the São Paulo State, Brazil. The technical concept of landfill in ditches takes into account the natural attenuation capacity of the soil to minimize the environmental impact.

 Nowadays, there are a great number of landfills in ditches in São Paulo State, whose simple implementation has been highly contested, making environmental investigation an important task to evaluate this activity impact on the environment. This work investigates the geoelectrical response of a landfill in ditches as an environmental impact evaluation tool. Geoelectrical surveys can help to evaluate the impact on soils and groundwater, leachate migration, and contaminant concentration attenuation. The MSW landfill in ditches in Luís Antônio is active since 1999 and operates in ditches of approximately 70 m long, 8 m wide, and 6 m deep.

Due to project designs, compacted soils are not used as impermeable base for the ditches. Therefore, this type of landfill requires favorable permeability soils and the water table at least 3 m below the ditch base. Luiz Antônio landfill was built on soils of 1 × 10<sup>−</sup><sup>5</sup> cm/s, and the water table depth is about 12 m.

The geophysical survey was conducted over the waste disposal area (two sessions) and upstream and downstream the ditches (**Figure 12**).

 The field survey was conducted with resistivity and time domain induced polarization using dipole-dipole array (5 m of spacing and six investigation levels). The Syscal Pro (Iris Instruments) resistivity meter was used to collect resistivity and chargeability data. Metallic electrodes were used for current injection, and nonpolarizing electrodes (Cu/CuSO4) for potential measurement. IP data were acquired with 2 s integration time with 160 ms delay after current shut off. Data were interpreted with the software RES2Dinv.

**Figure 13** shows the line crossing the ditches. Low resistivity (<30 ohm m) and high chargeability (>40 mV/V). No signs of leachate infiltration are observed with the geophysical data. The chargeability value distribution looks complex, but this pattern is a reflex of the waste heterogeneity, and overall, the observed chargeability values are higher than 15 mV/V.

*Resistivity and Induced Polarization Application for Urban Waste Disposal Site Studies DOI: http://dx.doi.org/10.5772/intechopen.81225* 

#### **Figure 13.**

*Resistivity and chargeability sessions of Line 2.* 

**Figure 14.**  *Resistivity and chargeability sessions perpendicular to the landfill ditches.* 

**Figure 14** shows the resistivity session perpendicular to the three ditches. Each ditch is clearly identified by low resistivity and high chargeability values. A low resistivity continuous feature beneath the ditches is observed, suggesting leachate migration.

To verify the contamination plume, another geophysical line was conducted south, 10 m from the ditches. This line does not show low resistivity features that
