HPC Italia has recently completed the detailed remediation design for an industrial area in Northern Italy covering a surface of 270,000 sq.m.
The site was utilized since the 1960's for production of chlorinated solvents and phenol-based compounds and is currently used for the production of industrial lube oil additives.
The overall remediation concept is complex and diversified, addressing both soil and groundwater, impacted by a wide spectrum of contaminants.
This note deals specifically with an 87,000 sq.m portion of the site where the upper level of the unsaturated soil is impacted by light and heavy Petroleum Hydrocarbons, Chrome and Zinc.
This portion of the site is abandoned and no future usage is foreseen, thus the decision was made to clean up surface soil (0 to 5m) by phytoremediation.
The choice of phytoremediation was dictated by the nature of the contaminants and by the client's wish to also overcome the state of abandon of the area by remodelling and landscaping.
The efficiency of the method and the suitability of native trees and shrubs were verified with a pilot application on a limited area, involving local "black poplar" (Populus Nigra) planted on a 2.5m by 2.5m grid and the inoculation of selected species of native fungi at roots level.
The pilot test results confirmed the suitability of the approach.
Basing on the positive outcome of the pilot test, HPC completed the remediation design which foresees :
- Excavation of parallel trenches 75 cm deep and 2.5 m apart
- Fertilization with organic compounds
- Planting of 6300 young poplar trees to a depth of 80-100 cm
- Inoculation of a fungi association into the roots of the trees (50 cm depth)
- A "drip" irrigation system designed to operate 4.5 hrs./day for each tree
The main advantages of HPC's remediation approach are :
- Significant landscape improvement
- Negligible energy costs and generation of waste
- Reduced remediation costs (20-40 euro/ton)
Limitations of the approach are those typical of phytoremediation, i.e. limited remediation depth (maximum 5m), extended remediation time (years…) and the non-availability of the site for any use or construction until remediation is completed.
However in the specific case these factors are of no concern to the Client, who was also praised by stakeholders for returning a sizeable patch of abandoned land to its pre-development state.