Abstract:
A method of reducing the contamination of soil in an area having varying degrees of contamination wherein the soils in locations having contaminations above a pre-determined level are first homogenized and then those soils are homogenized with the soil in the remainder of the area to be treated, whereupon the homogenized soils are treated until the contamination is reduced to a desired level.

Description:
RELATED REFERENCES  
         [0001]    Not applicable.  
         FIELD OF THE INVENTION  
         [0002]    This invention relates to method of cleaning contaminated soil, and more particularly, but not by way of limitation, to the treatment of contaminated soil collected from an area having varying degrees of contamination.  
         BACKGROUND OF THE INVENTION  
         [0003]    There are many techniques for reducing the contamination of soil from a relatively small area, such as the location of a fuel tank which may have been leaking into a rather confined area for many years. However, there has not been an effective and efficient technique for reducing the contamination of a relatively large area, such as 5 acres, where the level of contamination varies from location to location throughout the area under consideration.  
           [0004]    In summary, the present invention involves a process of homogenizing contaminated soils from different parts of a site with different degrees of contamination of, for example, crude oil, petroleum distillates, pesticides, PCBs, or chemically similar compounds. Eliminating such chemical “hot spots” is an important first step in remediation of relatively large-area contamination, such as an abandoned refinery, abandoned or closed landfill, chemical production facilities or airports. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a side view of a machine utilized for homogenizing and treating soil pursuant to this invention.  
         [0006]    [0006]FIG. 2 is an elevational view of the opposite side of the machine shown in FIG. 1.  
         [0007]    [0007]FIG. 3 is a plan or top view of the machine shown in FIGS. 1 and 2.  
         [0008]    [0008]FIG. 4 is a plan view of an area to illustrate varying levels of contamination in the area.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0009]    The present invention makes use of a shredder-mixer disclosed in U.S. Pat. No. 4,978,079, the disclosure which is hereby incorporated by reference.  
         [0010]    Referring to the drawings in detail, and particularly FIGS. 1 and 2, reference character  10  generally designates the mixer-shredder machine which basically comprises a frame  12  supported by a pair of wheels  14  at the rear end thereof and having a trailer hitch  16  on the forward end thereof by means of which the machine may be transported from one location to another.  
         [0011]    The machine  10  includes one or more hoppers  18  and a conveyer  20  forming a live bottom for the hoppers  18 . The conveyer  20  extends from underneath the hoppers  18  to a hammermill  22 , whereby material deposited in the hoppers  18  is conveyed into the hammermill  22 , wherein the material is homogenized and discharged out the end  24  of the hammermill  22 . Hammermill  22  and conveyer  20  are driven by an engine  26  mounted on the frame  12  and connected to the hammermill by a chain drive  28  (FIG. 2) and from the hammermill to the conveyer  20  by a chain drive  30  as shown in FIG. 1.  
         [0012]    Pursuant to the present invention, the machine  10  is provided with a tank  32  mounted on the frame  12  and containing a pump (not shown) connected by piping  34  to spray bars  36  and  38  extending adjacent to the discharge end  24  of the hammermill  22 . As shown by looking at FIGS. 1 and 3, the spray bar  36  extends above the path of movement of material discharging from the discharge end  24  of the hammermill  22  to spray material from the tank  32  onto the material being discharged from the hammermill; whereas the spray bars  38  extend along the sides of the path of movement of the material being discharged from the hammermill  22  to spray material from the tank  32  into the sides of that material being discharged from the hammermill. In this manner, the liquid from the tank  32  will be rather thoroughly mixed with the material being discharged from the hammermill  22 . The liquid being pumped from the tank  32  to the spray bars  36  and  38  may be any chemical composition designed to reduce the particular contamination of the soil being discharged from the hammermill  22 . For example, the chemical composition may be surfactants, ozone, chelators and encapsulation agents and biodegration enhancers including nutrients, microbial growth stimulators, and native microbial population.  
         [0013]    As shown in FIGS. 2 and 3, another tank  40 , containing a suitable pump (not shown) is mounted on the frame  12  and is connected by piping  42  to a spray bar  44  extending over the top of the conveyer  20  between the hoppers  18  and hammermill  22 . The spray bar  44  is utilized to spray liquid on soil  46  being transported by the conveyer  20  from the hoppers  18  to the hammermill  22 . The tank  40  may contain any desired liquid, such as water for moistening the soil  46  and/or, a suitable composition for treating the soil  46 . In some cases, water in the tank  40  may be ozonated as it is being sprayed onto soil just before the soil is fed into the hammermill  22 .  
         [0014]    [0014]FIG. 4 is provided to illustrate a contaminated area  48  which may be, for example,  5  acres of contaminated soil wherein the level of contamination varies from location to location within the area  48 . For example, as a result of a contamination survey, it may be determined that three locations  50 ,  52  and  54  are contaminated to a level above a predetermined amount. For example, the locations  50 ,  52  and  54  may be contaminated with hydrocarbon to levels exceeding 20,000 mg/kg total petroleum hydrocarbons (TPLt); whereas the remaining portion of the area  48  is contaminated to a lesser extent.  
         [0015]    Pursuant to the present invention, the more highly contaminated soils in the locations  50 ,  52  and  54  are excavated and moved to a location X which may be on the area  48  or adjacent to the area  48 . The soils from the locations  50 ,  52  and  54  are then mixed by use of a front end loader, for example, to obtain what may be considered a rather rough mixture of the soils.  
         [0016]    The machine  10  would then be located at X and the grossly mixed soils from the areas  50 ,  52  and  54  would be repeatedly run through the machine  10  to homogenize these soils into a rather uniform level of contamination. In this use of the machine  10 , the tank  40  would preferably contain water which is sprayed by the spray bar  44  onto the soil  46  being moved by the conveyer  20  in order to obtain a moisture content for the homogenized soils of, for example, 5%.  
         [0017]    After the soil from the areas  50 ,  52  and  54  have been homogenized, then the remainder of the soil from the area  48  is in turn progressively moved through the machine  10  along with the soil from the areas  50 ,  52  and  54  to produce a homogenized soil having a relatively uniform level of contamination. When that level of contamination is achieved, then the soil may be repeatedly passed through the machine  10  and treated with the desired chemical compositions by spraying those compositions using the spray bars  36 ,  38  and  44 . As previously mentioned, the chemical composition used for decontamination may be, for example mixtures of surfactants, chelalation and/or encapsulation agents, and biodegration enhancers, including nutrients microbial growth stimulation and native microbial population. Ozone treatment may also be used, depending upon the particular contamination and level of contamination. For example, if the contamination was a result of diesel oil the chemical composition may be surfactants and biodegradtion enhancers.  
         [0018]    It should also be noted that the soil excavated from not only the highly contaminated areas  50 ,  52  and  54 , but the remainder area  48  can be treated either on the area  48  or outside the area  48 , depending upon the circumstances required.  
         [0019]    After all of the soil from the area  48  has been decontaminated to the desired level, then the decontaminated soil will be spread back over the area  48 , preferably to a uniform level.  
         [0020]    After the decontaminated soil is spread back over the area  48 , a layer of compost may be applied onto the decontaminated soil to a level of, for example 2 inches. Alternatively, the compost may be mixed with the decontaminated soil during passage of the soil through the machine  10 .  
         [0021]    Also, after the decontaminated soil has been redistributed over the area  48 , the desired grass seeds may be distributed through the soil to provide an attractive reclaimed area. Further, if desired, earth worms may be distributed throughout the distributed soil to enhance the productivity of the soil.  
         [0022]    The soil  46  will be discharged from the hammermill  22  in a more or less rectangular cross sectional pattern as illustrated in FIGS. 1, 2 and  3  before gravity takes over and the soil falls; whereby the sprays from the spray bars  36  and  38  will thoroughly coat the soil.  
         [0023]    Changes may be made in the combination and arrangement of steps and procedures as set forth in the specification and shown in the drawings, without departed from the spirit and scope of the invention as defined in the following claims.