S"1': ^ i. ^ '?■• Z.Z- 0.:-.. ... n-^___ ^Trnvgp----------------- AUG 02 1990 remd section SECOND STREET SUBSITE REMEDIAL INVESTIGATION TECHNICAL MEMORANDUM AUGUST 1990 EPA Contract No. 68-01-7251 EPA Region 7 EPA Contact Darrell Sommerhauser Project No. 133-7LS2 PRC Work Assignment No. 017-W6884151 Prepared By PRC Environmental Management, Inc. Ray Mastrolonardo, Subsite Manager Telephone No. 312/856-8700 i 30353032 Superfund TABLE OF CONTENTS Section Page 1.0 INTRODUCTION................................................. 1-1 1.1 SCOPE OF WORK..................................... 1-1 1.2 SITE BACKGROUND........................................................................................... 1-1 1.2.1 Site Description.................. 1-1 1.2.2 General Site History ................................................................................. 1-3 1.3 SUBSITE BACKGROUND.............................................................. 1-4 1.3.1 Subsite Description.......................................... 1-5 1.3.2 Subsite History.......................... 1-5 1.3.3 Subsite Investigation................................................................................. 1-5 2.0 SUBSITE GEOLOGY AND HYDROGEOLOGY............................................................ 2-1 2.1 GEOLOGY.......................... 2-1 2.1.1 Topography.................................................................................................. 2-1 2.1.2 Stratigraphy and Depositions Environment ......................................... 2-1 2.2 HYDROGEOLOGY............................................................................................... 2-9 3.0 DISCUSSION OF INVESTIGATION RESULTS ............................................................ 3-1 3.1 DATA QUALITY AND OBJECTIVES........................ 3-1 3.2 SURFACE SOIL GAS CONTAMINATION....................................................... 3-2 3.3 SUBSURFACE SOIL GAS CONTAMINATION................................................ 3-2 3.4 SUBSURFACE SOIL CONTAMINATION................ 3-4 3.5 GROUND-WATER CONTAMINATION ..................... 3-5 3.6 SITE RELATED FATE AND TRANSPORT............................. 3-8 3.6.1 Soil Fate and Transport............................................................................ 3-10 3.6.2 Ground-Water Fate and Transport................. 3-10 4.0 RISK ASSESSMENT........................................................................................................... 4-1 4.1 INTRODUCTION ................................................................................................... 4-1 A2 EXPOSURE ASSESSMENT .............................................................. ;................ 4-1 4.2.1 Potential Exposure Pathways.................................................................. 4-1 4.2.1.1 Ground Water ............................................................................... 4-2 42.12 Soil................................................................ 4-2 422 Population at Risk..................................................................................... 4-3 4.2.2.1 GroundWater ............................................................................... 4-3 4222 Soil.................................................................................................. 4-4 TABLE OF CONTENTS Section Page 4.2.3 Exposure Estimation............................ 4-4 42.3.1 Ingestion........................................................................................ 4-4 4J2.3J2 Inhalation ...................................................................................... 4-4 4J.3.3 Dermal ........................................................................................... 4-6 4.2J.4 Exposure Dose Calculations ..................................................... 4-6 4.3 TOXICITY ASSESSMENT...................................................... 4-7 4.3.1 Toxicity Summaries.................................................... 4-7 4.3.2 Exposure Standards, Criteria, and Guidelines........................................ 4-9 4.4 RISK CHARACTERIZATION............................................................................. 4-12 % 4.4.1 Risk Estimation Methodology...................... 4-12 4.4.2 Ground-Water Use Risk .......................................................................... 4-13 4.4.3 Comparison to Drinking Water Standards.............................................. 4-14 4.4.4 Limitations and Assumptions................................................................... 4-14 4.4.4.1 Uncertainty Factors ........................ ..................................... 4-14 4.4.4J Assumptions ................................................................................. 4-22 4.5 SUMMARY.............................................................................................................. 4-22 5.0 REFERENCES .. ................................................................................................................... 5-1 Appendices I METHODS OF INVESTIGATIONS H REGIONAL GEOLOGY AND HYDROGEOLOGY m BOREHOLE LOGS IV PHYSICAL RESULTS V ANALYTICAL RESULTS V.A Symbol Nomenclature for Analytical Results VJ) Borehole Soil Data < V.C Borehole Soil Gas Data VJ) Ground Water Data VJE Surface Soil Gas Data VI SOIL, MOISTURE, AND SOIL GAS CONCENTRATION PROFILES (CHEMPLOTS) VH ENVIRONMENTAL FATE AND TRANSPORT Vm TOXICOLOGICAL EVALUATION OF CONTAMINANTS LIST OF TABLES Table Page 2- 1 ESTIMATED HYDRAULIC CONDUCTIVITY AND POROSITY VALUES..............2-14 3- 1 CONCENTRATIONS OF CONTAMINANTS IN SOILS FROM BOREHOLE B-23 . 3-6 3- 2 SUMMARY OF GROUND WATER DATA Qlg/L) FOR MW-9................................. 3-9 4- 1 AGE-SEX DISTRIBUTION FOR THE HASTINGS POPULATION......... ............... 4-3 4-2 REGULATORY STANDARDS AND GUIDELINES FOR INDICATOR CHEMICALS ....................................................................................................................... 4-10 4-3 RISK ESTIMATE CONCENTRATIONS...................................... ................................ 4-15 4-4 NONCARCINOGENIC RISKS FOR CHILDREN........................................................... 4-16 4-5 NONCARCINOGENIC RISKS FOR ADULTS................................................................ 4-17 4-6 EXCESS CANCER RISK ESTIMATES.............................................................................. 4-18 4-7 RESULTS FROM THE COMPARISON OF HIGHEST DETECTED MEAN CONCENTRATIONS ......................................................................................................... 4-19 4-8 GENERAL RISK ASSESSMENT........................................................................................ 4-20 4-9 SUBSITE RISK ASSESSMENT........... ......................................... 4-21 LIST OF FIGURES Figure Page 1-1 SITE LOCATION ...................................................... 1-2 1-2 SECOND STREET SUBSITE...................... 1-6 1-3 GAS PLANT FACILITY PLOT PLAN IN 1910 ............................................................. 1-7 1-4 GAS PLANT FACILITY PLOT PLAN IN 1924 ............................................................. 1-8 1- 5 SAMPLE LOCATIONS..................................................................................................... 1-10 2- 1 CROSS-SECTION LOCATIONS.....................'............................................................... 2-2 2-2 GEOLOGIC CROSS-SECTION A-A*.......................... 2-3 2-3 GEOLOGIC CROSS-SECTION B-B’ ................................................................................ 2-4 2-4 GEOLOGIC CROSS-SECTION C-C ............................................................................. 2-5 2-5 GEOLOGIC UNIT CROSS-SECTION A-A’................. 2-6 2-6 GEOLOGIC UNIT CROSS-SECTION B-B’ ........................ 2-7 2-7 GEOLOGIC UNIT CROSS-SECTION C-C .................................................................... 2-8 2-8 HYDROGEOLOGIC UNIT CROSS-SECTION A-A’...................................................... 2-10 2-9 HYDROGEOLOGIC UNIT CROSS-SECTION B-B’ ...................................................... 2-11 2-10 HYDROGEOLOGIC UNIT CROSS-SECTION C-C................................................... 2-12 2-11 GROUND-WATER POTENTIOMETRIC SURFACE FEBRUARY 1988 .................. 2-16 2- 12 GROUND-WATER POTENTIOMETRIC SURFACE JULY 1988 .............................. 2-17 3- 1 SAMPLE LOCATIONS................................................................... 3-3 1.0 INTRODUCTION This technical memorandum (TM) presents the results of the remedial investigation performed at the Second Street subsite of the Hastings Ground-Water Contamination site in Hastings, Nebraska, by PRC Environmental Management, Inc. (PRC), a member of the REM IV team. The purpose of this TM is to present soil. Soil gas and ground-water data that were collected between November 1917 and March 1989 at the Second Street subsite. The work was performed in partial satisfaction of U.S. EPA Contract No. 68-01-7251, Work Assignment No. 133-7LS2. Section 1.0 provides background information on the Second Street subsite investigation; Section 2.0 describes subsite-specific geology and hydrogeology; Section 3.0 describes the investigation results of the fate and transport of contaminants at the Second Street subsite; and Section 4.0 is a baseline risk assessment. The methods used during the investigation are described in Appendix I. 1.1 SCOPE OF WORK PRC conducted remedial investigation (RI) activities at the Second Street subsite to identify the