Contaminated material such as soil or sludge is remediated by injecting a suitable remediation fluid into the material during excavation of the contaminated material with a trenching tool. The remediation fluid is injected into the contaminated material through an injection means, preferably a plurality of injection nozzles positioned along the length of the trenching tool. The thusly treated material is backfilled or deposited directly into the trench excavated by trenching tool thereby obviating the need for off-site disposal. The constituent remediation agents in the remediation fluid may be adjusted to adapt to varying site conditions and contaminants. The remediation fluid may also be heated to accomplish volatile stripping of the contaminated material or to activate microbial agents in a low temperature environment.