THE ST. LOUIS SMELTING AND REFINING COMPANY OPERATED A LEAD SMELTING FACILITY AT THE SITE FROM 1904 UNTIL NOVEMBER 1933. IN MARCH 1950S, RESIDENTIAL DEVELOPMENT BEGAN IN THIS AREA. IN MARCH 2002, IEPA CONDUCTED FIELD-BASED CHARACTERIZATION OF RESIDENTIAL SOILS AND LAKE SEDIMENT. RESIDENTIAL SOIL INDICATED LEAD CONCENTRATIONS FROM BELOW DETECTION LEVELS TO OVER 90,000 PPM. BASED ON THE SAMPLE RESULTS TAKEN, OVER 41 DIFFERENT PARCELS CONTAIN LEAD LEVELS OVER 1,000 PPM IN THE UPPER TWO FEET OF SOIL. IN APRIL 2002, IEPA REFERRED THE MATTER TO EPA FOR CONSIDERATION OF A TIME CRITICAL REMOVAL. THE RESPONDENT NL INDUSTRIES, INC. IS A RESPONSIBLE PARTY AND IS LIABLE FOR PERFORMANCE OF RESPONSE ACTION AND FOR RESPONSE COSTS INCURRED AND TO BE INCURRED AT THE SITE. THE RESPONDENT SHALL REMOVE SOILS TO A MAXIMUM DEPTH OF 15 OR A LEAD CONCENTRATION AT OR BELOW 600 PPM, WHICH EVER OCCURS FIRST. THE RESPONDENT SHALL PAY EPA ALL RESPONSE COSTS NOT INCONSISTENT WITH THE NCP, AND SHALL BE LIABLE TO EPA FOR STIPULATED PENALTIES FOR FAILURE TO COMPLY WITH THE REQUIREMENTS OF THIS ORDER.