TECHNICAL SUPPORT FOR ROCKY MOUNTAIN ARSENAL

Offpost Operable Unit

Endangerment Assessment/Feasibility Study

Final Report

Volume III of VIII

(EA Sections 4.0, 5.0, 6.0, 7.0)

November 24, 1992

Contract Number DAAA15-88-0021

Task RIFS1 (Delivery Order 0001)

PREPARED BY

Harding Lawson Associates

Environmental Science and Engineering, Inc.

PREPARED FOR

PROGRAM MANAGER FOR ROCKY MOUNTAIN ARSENAL

THIS DOCUMENT IS INTENDED TO COMPLY WITH THE NATIONAL

ENVIRONMENTAL POLICY ACT OF 1969.

THE INFORMATION AND CONCLUSIONS PRESENTED IN THIS REPORT REPRESENT

THE OFFICIAL POSITION OF THE DEPARTMENT OF THE ARMY UNLESS EXPRESSLY

MODIFIED BY A SUBSEQUENT DOCUMENT. THIS REPORT CONSTITUTES THE

RELEVANT PORTION OF THE ADMINISTRATION RECORD FOR THIS CERCLA

OPERABLE UNIT.

M9200036
TABLE OF CONTENTS

Page

VOLUME I - INTRODUCTION

LIST OF TA BLES ..................................................... xix

LIST OF FIG U RES .................................................... xxv

PR E FA C E ........................................................... P-1

EXECUTIVE SUM M ARY .............................................. ES- I

IN TR O D U CTIO N ...................................................... 1-1

G LO SSA R Y .......................................................... G -1

VOLUME II - ENDANGERMENT ASSESSMENT

PR E F A C E ........................................................... II - P-1

1.0 IDENTIFICATION OF CHEMICALS OF POTENTIAL CONCERN ........... Il - 1-1

1.1 GENERAL SITE DATA EVALUATION CONSIDERATIONS .......... 11-1-4

1.2 STATISTICAL PROCEDURES FOR COMPARISON WITH

BACK GROUND ............................................. 11- 1-8

1.3 SELECTION OF CHEMICALS OF CONCERN ...................... II - 1-15

1.3.1 G roundwater ......................................... 11- 1-15

1.3.2 Surface Water/Sediment ................................. 11- 1-17

1.3.3 Surficial Soil .......................................... 11- 1-21

1.3.4 Biota ................................................ 11 - 1-22

1.4 SU M M ARY ................................................ 11- 1-24

1.5 UNCERTAINTIES ........................................... 11- 1-26

2.0 EXPOSURE ASSESSMENT ......................................... 11-2-1

2.1 PROPERTIES AND PROBABLE ENVIRONMENTAL FATES

OF CHEMICALS OF CONCERN ................................ 11-2-1

2.1.1 Equilibrium Partitioning Properties of Chemicals of Concern ..... 11- 2-2

2.1.1.1 Information Sources .............................. Il - 2-3

2.1.1.2 Data Evaluation ................................ 11- 2-5

2.1.1.3 R esults ....................................... II - 2-7

2.1.2 Offpost Environmental Fate of Chemicals of Concern ........... 11- 2-9

2.1.2.1 Organochlorine Pesticides ......................... 11- 2-9

2.1.2.2 Benzene Compounds ............................. II - 2-15

2.1.2.3 Halogenated Aliphatic Compounds .................. II - 2-19

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2.1.2.4 Compounds Containing Sulfur ...................... II - 2-23

2.1.2.5 Compounds Containing Phosphorus .................. II - 2-24

2.1.2.6 Ionic Chem icals ................................. Il - 2-26

2.1.2.7 Miscellaneous Compounds ......................... Il - 2-30

1. 3 U ncertainties ......................................... Il - 2-31

2.2 CHARACTERIZATION OF EXPOSURE SETTING .................. II - 2-32

I Site Characteristics Affecting Contaminant Migration ........... II - 2-32

2.2.1.1 Site Description and History ....................... II - 2-32

2.2.1.2 Environmental Setting ............................ II - 2-33

2.2.1.3 Sampling Locations and Media ..................... Il - 2-34

2.2.1.4 Summary of Offpost Operable Unit Contamination ...... Il - 2-36

4.2.2 Potentially Exposed Populations ........................... Il - 2-37

2.2.2.1 Residential Land Use ............................ Il - 2-38

.".-.2. 1. 1 Procedures ........................... 11- 2-38

2. 1. 2 R esults .............................. 11 - 2-41

2.2.22. 2 Commercial/Industrial Land Uses 11- 2-42

2. 22. 2.3 Qualitative Assessment of the Likelihood of Occurence

of the Selection of Future Land Use for the Offpost

Endangerment Assessment/ Feasibility Study ........... 11 - 2-44

2.2.2.4 W ater U se ..................................... 11- 2-45

2.2.2.4.1 Existing Groundwater Use ............... 11- 2-45

2.2.2.4.2 Projected Future Use of Groundwater ....... 11- - 2-49

2.2.2.4.3 Surface-Water Use ..................... II - 2-50

2.3 EXPOSURE PATHWAYS ...................................... 11- 2-51

2.3.1 Potential Sources, Release Mechanisms, and Transport Media ..... 11- 2-51

2.3.1.1 G roundwater ................................... 11- 2-51

2.3.1.2 Surface Water and Sediment ....................... 11-2-54

2.3.1.3 A tm ospheric ................................... Il - 2-55

2.3.1.4 Biotic ........................................ 11 - 2-55

2.3.2 Potential Exposure Points ................................ 11-2-56

2.3.3 Potential Exposure Pathways and Routes ..................... 11 - 2-57

2.3.3.1 Inhalation Route ................................ 11- 2-57

2.3.3.2 Dermal Route .................................. 11-2-60

2.3.3.3 Ingestion Route ................................. 11-2-61

2.3.4 U ncertainties ......................................... Il - 2-64

2.4 QUANTIFICATION OF EXPOSURE ............................. 11 - 2-64

2.4.1 Identification of Zones Having Distinct Exposure Concentrations

and/or Pathways ....................................... II - 2-66

2.4.2 Exposure Assessment Procedures and Exposure Point

Concentrations ........................................ Il - 2-71

2.4.2.1 Statistical Procedures Used to Evaluate Monitoring

D ata ......................................... Il - 2-72

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2.4.2.2 Model Used to Estimate 30-Year Groundwater Exposure

Point Concentration ............................. II - 2-73

2.4.2.3 Models Used to Estimate Concentrations in Agricultural

Products .... .... II - 2-74

2.4.2.3.1 icken gs ......................... 11- 2-75

2.4.2.3.2 Vegetables ............................ 11- 2-75

2.4.2.3.3 Beef ................................ 11 - 2-81

Z.4.2.3.4 Dairy ............................... II - 2-82

2.4.2.4 Summary of Nonchemical-specific Parameters ......... 11 - 2-83

Groundwater Fraction Used for

Irrigation (GW F) ....................... II - 2-83

,(-.4.2.4.2 Fraction Exposed (fe) ................... 11 - 2-83

2 .4.2.4.3 Partition Coefficient Deposited from

Spray (K d,p)) .......................... 11- 2-83

2.4.2.4.4 Cattle Water/Feed Intakes (IPWM and Ipwd) .... 11 - 2-84

".4.2.4.5 Cattle Feed/Soil Intake (I ') ............... 11- 2-84

2 P 2.4.2.5 Sample Calculations and Comparison With the Available

M onitoring Data ................................ 11- 2-84

2.4.2.6 R esults ...................... I ................. II - 2-86

2.4.3 Estimation of Chemical Intakes ............................ 11 - 2-90

2.4.3.1 Chemical -specific Parameters ...................... 11 - 2-94

2.4.3.2 Exposure Factors ................................ II - 2-95

2.4.3.3 R esults ....................................... II - 2-98

2.4.4 Estimation of Chemical Intakes for Commercial/ Industrial

Scenario ............................................. 11 - 2-99

2.4.4.1 Estimation of Chemical Intakes ..................... 11-2-100

2.4.5 Uncertainty Analysis (Residential) ......................... 11-2-100

2.4.5.1 Preliminary Sensitivity Analysis .................... 11-2-101

2.4.5.2 Additional Scoping Considerations .................. 11-2-102

2.4.5.3 Procedures .................................... 11- 2-103

2.4.5.4 Determination of Input Parameter Distributions ........ 11 - 2-104

2.4.5.5 Results ............. 11-2-106

2.4.5.5.1 Input Parameters ....................... 11-2-106

2.4.5.5.2 Example Results ....................... 11- 2-108

2.4.5.5.3 Summary of Results .................... 11-2-110

2.5 SUMMARY OF EXPOSURE ASSESSMENT ........................ 11 -2-112

2.5.1 Residential Scenario ...... - - - * I * I I I * * I I I * I I I I I * I * 1 11- 2-113

2.5.2 Commercial/ Industrial Scenario ........................... 11-2-116

2.6 UNCERTAINTIES ........................................... 11 - 2-116

3.0 TOXICITY ASSESSM ENT .......................................... II - 3-1

3.1 HUMAN REFERENCE DOSES ................................. II - 3-1

3.2 POTENTIAL CARCINOGENICITY OF CHEMICALS OF CONCERN .... 11- 3-5

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3.2.1 W eight of Evidence ..................................... 11- 3-5

3.2.2 Slope Factor .......................................... II - 3-6

3.3 NONHUMAN RECEPTOR TOXICITY REFERENCE VALUES ........ 11- 3-7

3.3.1 V egetation ........................................... 11 - 3-8

3.3.2 Aquatic Organism s ..................................... 11- 3-8

3.3.3 Terrestrial Organism s ................................... IT- 3-9

3.3.3.1 Derivation of a No-Observed- Adverse- Effect Level ..... 11 - 3-10

3.3.3.2 Phylogenetic Differences .......................... 11- 3-13

3.3.3.2_. 1 Intraspecies Differences ................. II - 3-16

3.3.3.2.2 Genus and Species Differences ............ II - 3-16

3.3.3.2.3 Family/Order Differences ................ 11 - 3-18

3.3.3.2.4 Threatened or Endangered Species .......... II - 3-19

3.4 MAXIMUM ACCEPTABLE TISSUE CONCENTRATIONS ............ II - 3-19

3.5 UNCERTAINTIES IN TOXICITY ASSESSMENT .................... 11- 3-20

3.5.1 Human Toxicity Assessment .............................. 11- 3-20

3.5.2 Toxicity Reference Values ............................... II - 3-21

VOLUME III - ENDANGERMENT ASSESSMENT

4.0 HUMAN RISK CHARACTERIZATION ............................... 111-4-1

4.1 RESIDENTIAL SCENARIO .................................... 111 -4-2

4.1.1 Hypothetical Future Exposures ............................ 111- 4-3

4.1.1.1 Hypothetical Carcinogenic Risks Related to Background . . III - 4-4

4.1.1.2 Child Chronic Hypothetical Future Hazard Indices ...... III - 4-5

4.1.1.3 Adult Chronic Hypothetical Future Hazard Indices ...... 111-4-6

4.1.1.4 Hypothetical Future Carcinogenic Risk ............... III - 4-6

4.1.1.5 Zone-specific Risks ............................. 111-4-6

4.1.1.6 Acute/Subchronic Effects ......................... 111-4-10

4.1.2 Hypothetic Current Risks Versus Hypothetical Future Risks ...... 111 -4-12

4.1.3 Health Risk at Most Likely Exposure Intakes ................. 111-4-12

4.1.4 Alternative Risk Estimate Based on Predicted Decline in

Groundwater Concentrations .............................. 111 -4-14

4.2 COMMERCIAL/INDUSTRIAL SCENARIO ........................ 111-4-14

4.2.1 Adult Chronic Hypothetical Future Hazard Indices ............. III - 4-15

4.2.2 Hypothetical Future Carcinogenic Risks ..................... III - 4-15

4.2.3 Carcinogenic Risk at Most Likely Exposure Intakes ............. III - 4-15

4.3 RISK CHARACTERIZATION SUMMARY ........................ III - 4-15

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4.4 UNCERTAINTIES IN THE HUMAN HEALTH ASSESSMENT ......... 111 -4-18

5.0 ECOLOGICAL ASSESSMENT ....................................... III - 5-1

5.1 SITE CHARACTERIZATION ................................... III - 5-1

5.1.1 Study Area Definition ................................... III - 5-1

5.1.1.1 Terrestrial System s .............................. III - 5-2

5.1.1.2 Aquatic Systems ................................ Ill- 5-3

5.1.2 Ecological Characterization of the Offpost Operable Unit ........ III - 5-4

5.1.3 Contamination Pertaining to Offpost Biota ................... III - 5-5

5.1.4 Selection of Chemicals of Concern for Biota .................. III - 5-6

5.2 EXPOSURE ASSESSMENT ..................................... Ill- 5-7

5.2.1 Potential Biological Receptors and Sensitive Subpopulations ...... III - 5-7

5.2.1.1 Terrestrial Receptors ............................. III - 5-8

5.2.1.2 Aquatic Receptors ............................... III - 5-10

5.2.2 Potential Exposure Pathways .............................. III - 5-11

5.2.3 Exposure Point Concentrations ............................ III - 5-14

5.2.4 Ecological Assessment Endpoints .......................... III - 5-15

5.2.4.1 Terrestrial ..................................... III - 5-15

5.2.4.2 A quatic ....................................... Ill - 5-16

5.2.5 Bioaccumulation Exposure ............................... III - 5-17

5.2.5.1 Terrestrial Food Web Ingestion Pathways .............. III - 5-17

5.2.5.2 Terrestrial Food Web Predicted Tissue Concentrations .... III - 5-19

5.2.5.3 Aquatic Food Web Ingestion Pathways ................ 111-5-20

5.2.5.4 Aquatic Food Web Predicted Tissue Concentrations ...... III - 5-21

5.2.6 Direct Exposure to Chemicals of Concern .................... 111-5-21

5.2.6.1 Surface-Water Ingestion Pathway ......... * , * , , * , , , , 111- 5-21

5.2.6.2 Direct Contact with Surface Water or Sediment ......... III - 5-23

5.2.6.3 Soil Ingestion .................................. III - 5-23

5.2.6.4 Dietary Ingestion for Wildlife ...................... 111- 5-24

5.2.6.5 Dietary and Soil Ingestion Pathways for Livestock ....... III - 5-24

5.3 RISK CHARACTERIZATION .................................. 111- 5-26

5.3.1 Terrestrial Food Web Ecological Risk ....................... Ill- 5-26

5.3.2 Aquatic Food Web Ecological Risk ......................... Ill- 5-29

5.3.3 Underwater Aquatic Life ................................ III - 5-30

5.3.4 Agricultural Life ...................................... 111- 5-30

5.3.5 Ecological Risk Assessment Uncertainty ..................... III - 5-31

5.3.5.1 Site Characterization ............................. III - 5-31

5.3.5.2 Exposure Assessment ............................ III - 5-32

5.3.5.3 Risk Characterization ............................ Ill- 5-34

5.4 SU M M A RY ................................................ III - 5-34

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6.0 CONCLU SIONS .................................................. 111-6-1

7.0 REFER EN CES ................................................... 111- 7-1

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VOLUME IV - ENDANGERMENT ASSESSMENT

LIST OF APPENDIXES

A RELEASE OF VOLATILE CONTAMINANTS FROM GROUNDWATER WITH

SUBSEQUENT EXPOSURE IN BASEMENTS: SCREENING LEVEL ANALYSIS

B ESTIMATE OF AMBIENT PARTICULATE MATTER IMPACT DUE TO WIND

EROSION NEAR ROCKY MOUNTAIN ARSENAL

C EXPOSURE CONCENTRATIONS

D ESTIMATED REASONABLE MAXIMUM EXPOSURE INTAKES

E UNCERTAINTY ANALYSIS

F TOXICOLOGICAL PROFILES

* ESTIMATED REASONABLE MAXIMUM EXPOSURE RISKS AND HAZARD

INDICES

* SUPPORTING INFORMATION FOR THE ECOLOGICAL ASSESSMENT

HI - ANIMAL SPECIES OF POSSIBLE OCCURRENCE IN RMA OFFPOST AREA

H2 - BIOACCUMULATION FACTORS, BIOMAGNIFICATION FACTORS, AND

PREDICTED TISSUE CONCENTRATIONS

- TERRESTRIAL FOOD WEB

- AQUATIC FOOD WEB

H3 - EXPOSURE POINT CONCENTRATIONS OF CHEMICALS IN SURFACE

WATER AND PREDICTED CHEMICAL INTAKE FOR AVIAN SPECIES

H4 - HAZARD QUOTIENT SUMMARY TABLES FOR CATTLE

H5 - MAXIMUM ALLOWABLE TISSUE CONCENTRATION VALUES

H6 - SPATIAL WEIGHING ADJUSTMENT FACTORS

H7 - ONPOST HHRC SOFTWARE BLUE VERSION 1.0 PREPARED FOR THE

PROGRAM MANAGER RMA EBASCO SERVICES, INC., MARCH 1992

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VOLUME V - FEASIBILITY STUDY

PR EFA C E ........................................................... V - P-1

1.0 FEASIBILITY STUDY PURPOSE AND ORGANIZATION ................. V - 1-1

1.1 STEP I - DEVELOPMENT OF REMEDIAL ACTION OBJECTIVES ..... V - 1-1

1.2 STEP 11 - DEVELOPMENT AND SCREENING OF ALTERNATIVES .... V - 1-2

1.3 STEP III - DETAILED ANALYSIS OF ALTERNATIVES ............. V - 1-2

1.4 STEP IV - SELECTION OF THE PREFERRED SITEWIDE

ALTERNATIVE ............................................. V - 1-3

2.0 DEVELOPMENT OF REMEDIAL ACTION OBJECTIVES AND SCREENING

OF TECHNOLOGIES .............................................. V - 2-1

2.1 OVERVIEW OF REMEDIAL ACTION OBJECTIVES DEVELOPMENT .. V - 2-1

2.2 NATIONAL CONTINGENCY PLAN AND ACCEPTABLE RISK RANGE

CONSIDERATIONS .......................................... V - 2-2

2.2.1 Comparison of Cumulative Risk With the Acceptable Risk Range . . V - 2-2

2.2.2 Identification of Media Requiring Remedial Action Objectives .... V - 2-4

2.2.3 Site-specific Factors Considered for Groundwater

Remedial Action Objectives Development .................... V - 2-6

2.3 DEVELOPMENT OF GROUNDWATER REMEDIAL ACTION

OBJECTIVES ............................................... V - 2-6

2.3.1 Development of Remedial Action Objectives, Step 1: Identification

of Chemicals of Concern ............................ ''*** V - 2-7

2.3.2 Development of Groundwater Remedial Action Objectives Step 2:

Identification of Potential Exposure Pathways ................. V- 2-7

2.4 GROUNDWATER REMEDIAL ACTION OBJECTIVES ............... V - 2-8

2.4.1 Groundwater Remedial Action Objectives .................... V - 2-9

2.4.1.1 Human Health .................................. V - 2-9

2.4.1.2 Environmental Protection ......................... v - 2-9

2.5 DEVELOPMENT OF GROUNDWATER PRELIMINARY

REMEDIATION GOALS ..................................... V - 2-10

2.5.1 Effects of Future Land Use on the Development of

Preliminary Remediation Goals ........................... V - 2-11

2.5.2 National Contingency Plan and Point of Departure Considerations

for Development of Preliminary Remediation Goals ............ V - 2-12

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2.5.3 Types of Groundwater Preliminary Remediation Goals .......... V - 2-15

2.5.3.1 Identification of Applicable or

Relevant and Appropriate Requirements ............. V - 2-15

2.5.3.1.1 Chemical -specific Applicable or

Relevant and Appropriate Requirements .... V - 2-17

2.5.3.1.2 Location -specific Applicable or Relevant

and Appropriate Requirements ............ V - 2-19

2.5.3.1.3 Action-specific Applicable or

Relevant and Appropriate Requirements .... V - 2-18

2.5.3.2 Health-based Criteria ............................ V - 2-18

2.5.3.3 Background Concentrations ........................ V - 2-20

2.5.3.4 Ecological Criteria ..................... : * , , , * ... V -2-20

2.5.4 Development and Identification of Preliminary Remediation Goals -

Groundwater ......................................... V - 2-20

2.5.4.1 Groundwater Chemical -specific Applicable or Relevant

and Appropriate Requirements ... V - 2-20

2.5.4.2_ Groundwater Health-based Criteria .................. V - 2-21

";..5.4 3 Selection of Groundwater Preliminary Remediation Goals . V - 2-21

2.6 QUANTITIES OF GROUNDWATER REQUIRING REMEDIATION ..... V - 2-22

2.7 GENERAL RESPONSE ACTIONS ............................... V - 2-22

2.7.1 N o A ction ............................................ V - 2-23

2.7.2 Institutional Controls ................................... V - 2-23

2.7.3 Containment .......................................... V - 2-23

2.7.4 Rem oval ............................................. V - 2-24

2.7.5 Treatm ent ............................................ V - 2-24

2.7.6 Disposal ............................................. V - 2-24

2.8 IDENTIFICATION AND SCREENING OF TECHNOLOGY TYPES AND

PROCESS OPTIONS .......................................... V - 2-25

2.8.1 Universal Screening .................................... V - 2-26

2.8.2 Evaluation and Screening of Selected Process Options ........... V - 2-26

2.8.3 Nonmedia- specific Process Options ......................... V - 2-27

2.8.3.1 No Action ..................................... V - 2-27

2.8.3.2 Institutional Controls ............................. V - 2-28

2.8.3.2.1 Access Restrictions ..................... V - 2-28

2.8.3.2.2 Alternative Water Supplies ................ V - 2-29

2.8.3.2.3 M onitoring ........................... V - 2-29

2.8.4 Groundwater Process Options ............................. V - 2-30

2.8.4.1 Rem oval ...................................... V - 2-30

2.8.4.1.1 Groundwater Extraction ................. V - 2-30

2.8.4.2 Disposal .......... V - 2-33

2.8.4.2.1 Subsurface bis*p'o'sa'l* V - 2-33

2.8.4.2.2 Aboveground Discharge ................. V - 2-35

2.8.4.3 In-vessel Treatment of Groundwater ................. V - 2-37

2.8.4.3.1 Solids Removal ........................ V - 2-37

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2.8.4.3.2 Phase Transfer ........................ V - 2-39

2.8.4.3.3 Sorption ............................. V - 2-40

2.8.4.3.4 Oxidation ............................ V - 2-42

2.8.4.3.5 Radiation ............................ V - 2-44

2.8.4.3.6 Biological Treatment .................... V - 2-45

2.8.4.4 In Situ Treatment ............................... V - 2-46

2.8.4.4.1 Water Flushing ........................ V - 2-46

2.8.4.4.2 Enhanced Biological Treatment ............ V - 2-47

2.ý.4.5 Containment ........ .......................... V - 2-48

2.8.4.5.1 Subsurface Barriers ..................... V - 2-48

2.9 SUMMARY OF PROCESS OPTION SCREENING ................... V - 2-50

2.10 SELECTION OF REPRESENTATIVE PROCESS OPTIONS ............ V - 2-50

.2.10.1 Representative Process Options for Groundwater Remediation .... V - 2-51

VOLUME VI - FEASIBILITY STUDY

3.0 DEVELOPMENT OF REMEDIAL ALTERNATIVES ..................... VI - 3-1

3.1 FEASIBILITY STUDY OVERVIEW .............................. VI - 3-1

3.1.1 U.S. Environmental Protection Agency Guidance for

Alternatives Development and Evaluation .................... VI - 3-1

3.2 ALTERNATIVES IDENTIFICATION ............................. VI - 3-3

3.2.1 A pproach ............................................ VI - 3-3

3.2.1.1 Groundwater Model Input Into Alternatives

Development ................................... VI - 3-4

3.2.1.1.1 Chemicals of Concern .................. VI - 3-4

3.2.1.1.2 Use of the Model in Alternatives

Development .......................... VI - 3-5

3.2.1.2 Groundwater Alternative Types .................... VI - 3-9

3.3 LAND OWNERSHIP IMPLICATIONS FOR IMPLEMENTING REMEDIAL

ALTERNATIVES ............................................ VI - 3-10

3.4 COMMONALITIES OF ALTERNATIVES ......................... VI - 3-10

3.4.1 Commonalities of Groundwater Remedial Alternatives .......... VI - 3-11

3.4.1.1 Groundwater Alternatives Institutional Controls ........ VI - 3-11

3.4.1.1.1 Provision of an Alternative Water Supply

(Exposure Control) ..................... VI - 3-11

3.4.1.1.2 Monitoring Networks ................... VI - 3-12

3.4.1.1.3 Site Review ......... 6 ................. VI - 3-12

3.4.1.2 'Groundwater Pretreatment Process ptions ............ VI - 3-13

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3.4.1.3 Continued Operation of the Boundary Systems and

Compliance With Offpost Operable Unit Preliminary

Remediation Goals .............................. VI - 3-13

3.5 GROUNDWATER REMEDIAL ALTERNATIVES IDENTIFICATION ... VI - 3-13

3.5.1 Identification of Groundwater Alternatives: North

Plum e G roup .................. :***'*''*****'***"*''** VI - 3-14

3.5.1.1 Alternative No. N-1: No Action .................... VI - 3-14

3.5.1.2 Alternative No. N-2: Continued Operation of the North

Boundary Containment System With Improvements as

Necessarv ................... VI - 3-14

3.5.1.3 Alternative No. N-3: Land Acquisition and Use

Restrictions ........... :*- **- '- *********** VI - 3-15

3.5.1.4 Alternative No. N-4: Interim Response Action A ....... VI - 3-16

3.5.1.5 Alternative No. N-5: Expansion I to Interim Response

A ction A ..................................... V I - 3-18

3.5.1.6 Alternative No. N-6: Expansion 2 to Interim Response

Action A ......... ''*''*''** ...... VI - 3-19

3.5.1.7 Summary of Alternatives Identified for the North Plume

Group ............. VI - 3-21

3.5.2 Identification of Groundwater Alternatives: Northwest Plume

Group ...................... :*,*''*,****'** ... - - 1 VI - 3-22

3.5.2.1 Alternative NW-1: No Action ...................... VI - 3-22

3.5.2.2 Alternative NW-2: Continued Operation of the Northwest

Boundary Containment System ..................... VI - 3-22

3.5.2.3 Alternative No. NW-3: Land Acquisition With Use

Restrictions .................................... VI - 3-23

3.5.2.4 Alternative No. NW-4: Northwest Plume Group

Extraction /Recharge System ....................... VI - 3-24

3.5.2.5 Summary of Alternatives Identified for the Northwest

Plume Group .................................. VI - 3-25

4.0 SCREENING OF ALTERNATIVES ................................... VI - 4-1

4.1 M ETHODOLOGY ............................................ VI - 4-1

4.1.1 Effectiveness Evaluation ................................. VI - 4-1

4.1.2 Implementability Evaluation .............................. VI - 4-2

4.1.3 Cost Evaluation ............. VI - 4-3

4.2 SCREENING OF ALTERNATIVES .............................. VI - 4-4

4.2.1 Screening of Alternatives - North Plume Group ............... VI - 4-4

4.2.1.1 Alternative No. N- 1: No Action .................... VI - 4-4

4.2.1.1.1 Effectiveness .......................... VI - 4-5

4.2.1.1.2 Implementability ....................... VI - 4-6

4.2.1.1.3 Cost ................................ V I - 4-6

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Page

4.2.1.2 Alternative No. N-2: Continued Operation of the North

Boundary Containment System With Improvements as

N ecessary ..................................... V I - 4-6

4.2.1.2.1 Effectiveness .......................... VI - 4-7

4.2.1.2.2 Implementability ....................... VI - 4-8

4.2.1.2.3 Cost ...... ......................... VI - 4-8

4.2.1.3 Alternative No. N-3: Land Acquisition and Deed

Restrictions .................................... V I - 4-9

4.2.1.3.1 Effectiveness .......................... VI - 4-9

4.2.1.3.2 Implementability ....................... VI - 4-10

4.2.1.3.3 Cost ....... : * , , * , * , * , * * , * * .... * , * , * V I - 4-11

4.2.1.4 Alternative No. N-4: Interim Response Action A ....... VI - 4-11

4.2.1.4.1 Effectiveness .......................... VI - 4-11

4.2.1.4.2 Implementability ....................... VI - 4-12

4.2.1.4.3 Cost ................... : * , , * , * * , * , I I VI - 4-13

4.2.1.5 Alternative No. N-5: Expansion I to Interim

Response Action A .............................. VI -4-13

4.2.1.5.1 Effectiveness .......................... VI - 4-13

4.2.1.5.3 Implementability ....................... VI - 4-14

4.2.1.5.3 Cost ....... ........................ V I - 4-15

4.2.1.6 Alternative No. N-6: Expansion 2 to Interim

Response Action A .............................. VI - 4-15

4.2.1.6.1 Effectiveness .......................... VI - 4-15

4.2.1.6.2 Implementability ....................... VI - 4-16

4.2.1.6.3 Cost ..... .......................... VI - 4-17

4.2.1.7 Alternative Screening Summary and Recommendation .... VI - 4-17

4.2.2 Screening of Groundwater Alternatives - Northwest Plume

G roup ............................................... V I - 4-18

4.2.2.1 Alternative No. NW-I: No Action .................. VI - 4-18

4.2.2.1.1 Effectiveness .......................... VI - 4-19

4.2.2.1.2 Implementability ....................... VI - 4-20

4.2.2.1.3 Cost ................................ VI - 4-20

4.2.2.2 Alternative No. NW-2: Continued Operation of the

Northwest Boundary Containment System With

Improvements As Necessary ....................... VI - 4-20

4.2.2.2.1 Effectiveness .......................... VI - 4-21

4.2.2.2.2 Implementability ....................... VI - 4-22

4.2.2.2.3 Cost ................................ VI - 4-22

4.2.2.3 Alternative No. NW-3: Land Acquisition and Deed

Restrictions .................................... VI - 4-23

4.2.2.3.1 Effectiveness .......................... VI - 4-23

4.2.2.3.2 Implementability ....................... VI - 4-24

4.2.2.3.3 Cost ................................ VI - 4-24

4.2.2.4 Alternative No. NW-4: Northwest Plume Group

Extraction /Recharge System ....................... VI - 4-25

4.2.2.4.1 Effectiveness .......................... VI - 4-25

4.2.2.4.2 Implementability ....................... VI - 4-26

4.2.2.4.3 Cost ................................ VI - 4-27

4.2.2.5 Alternative Screening Summary and Recommendation .... VI - 4-27

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Page

5.0 DETAILED ANALYSIS OF ALTERNATIVES ........................... VI - 5-1

5.1 CR ITER IA ................................................. V I - 5-2

5.1.1 Overall Protection of Human Health and the Environment ....... VI - 5-2

5.1.2 Compliance With Applicable or Relevant and

Appropriate Requirements ..... ......................... VI - 5-2

5.1.3 Long-term Effectiveness and Permanence .................... VI - 5-3

5.1.4 Reduction of Toxicity, Mobility, or Volume .................. VI - 5-3

5.1.5 Short-term Effectiveness ................................ VI - 5-3

5.1.6 Im plem entability ....................................... VI - 5-4

5.1.7 C ost ................................................ V I - 5-4

5.1.8 State Acceptance ....................................... VI - 5-4

5.1.9 Community Acceptance ................................. VI - 5-5

5.2 MODELING RESULTS SUMMARY ............................. VI - 5-5

5.3 FURTHER DEFINITION OF ALTERNATIVES ..................... VI - 5-7

5.3.1 Alternative No. N-1: No Action ........................... VI - 5-7

5.3.2 Alternative No. N-2: Continued Operation of the North

Boundary Containment System With Improvements as Necessary ... VI - 5-8

5.3.3 Alternative No. N-4: Interim Response Action A .............. VI - 5-8

5.3.4 Alternative No. N-5: Expansion I to Interim Response

A ction A ............................................ V I - 5-10

5.3.5 Alternative No. NW- 1: No Action ........................ VI - 5-11

5.3.6 Alternative No. NW-2: Continued Operation of the Northwest

Boundary Containment System With Improvements as Necessary VI - 5-11

5.4 DETAILED ANALYSIS OF ALTERNATIVES ..................... VI - 5-12

5.4.1 Overall Protection of Human Health and the Environment ...... VI - 5-12

5.4.1.1 Alternative No. N-1: No Action ..... :* *******'*'' VI - 5-12

5.4.1.2 Alternative No. N-2: Continued Operation of

the North Boundary Containment System With

Improvements as Necessary ....................... VI - 5-13

5.4.1.3 Alternative No. N-4: Interim Response Action A ...... VI - 5-14

5.4.1.4 Alternative No. N-5: Expansion I to Interim

Response Action A ............................. VI - 5-15

5.4.1.5 Alternative No. NW-1: No Action ........... *****' VI - 5-15

5.4.1.6 Alternative No. NW-2: Continued Operation of the

Northwest Boundary Containment System With

Improvements as Necessary ....................... VI - 5-16

5.4.2 Compliance With Applicable or Relevant and

Appropriate Requirements . **'*''* :**--'---- VI - 5-16

5.4.2.1 Alternative No. N-1: No Action ................... VI - 5-17

5.4.2.1.1 Chemical -specific Applicable or

Relevant and Appropriate Requirements ... VI - 5-17

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Page

5.4.2.1.2 Action-specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-17

5.4.2.1.3 Location -specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-17

5.4.2.2 Alternative No. N-2: Continued Operation of the North

Boundary Containment System With Improvements

as Necessary ................................... VI - 5-17

5.4.2.2.1 Chemical -specific Applicable or

Relevant and Appropriate Requirements .... VI - 5-17

5.4.2."2.2 Action-specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-18

5.4.2.2.3 Location -specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-18

5.4.2.3 Alternative No. N-4: Interim Response Action A ....... VI - 5-18

5.4.2.3.1 Chemical -specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-18

5.4. 21. 3.2 Action-specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-18

5.4.2.3.3 Location -specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-18

5.4.2.4 Alternative No. N-5: Expansion I to Interim

Response Action A .............................. VI - 5-18

5.4.2.4.1 Chemical -specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-18

5.4.2.4.2 Action-specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-19

5.4.2.4.3 Location -specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-19

5.4.2.5 Alternative No. NW- 1: No Action ................. VI - 5-19

5.4.2.5.1 Chemical -specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-19

5.4.2.5.2 Action-specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-19

5.4.2.5.3 Location -specific Applicable or Relevant

and Appropriate Requirements .... * , * * * * , , VI - 5-19

5.4.2.6 Alternative No. NW-2: Continued Operation of the

Northwest Boundary Containment System With

Improvements as Necessary ............... VI - 5-19

5.4.2.6.1 Chemical -specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-19

5.4.2.6.2 Action-specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-20

5.4.2.6.3 Location -specific Applicable or Relevant

and Appropriate Requirements ............ VI - 5-20

5.4.3 Long-term Effectiveness and Permanence ................... VI - 5-20

5.4.3.1 Alternative No. N-1: No Action .................... VI - 5-20

5.4.3.2 Alternative No. N-2: Continued Operation of North

Boundary Containment System With Improvements as

Necessary ..................................... VI - 5-20

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Page

5.4.3.3 Alternative No. N-4: Interim Response Action A ....... VI - 5-21

5.4.3.4 Alternative No. N-5: Expansion I to Interim

Response Action A ... VI - 5-21

5.4.3.5 Alternative No. NW-1: No Action ................. VI - 5-22

5.4.3.6 Alternative No. NW-2: Continued Operation of the

Northwest Boundary Containment System With

Improvements as Necessary ........................ VI - 5-22

5.4.4 Reduction of Toxicity, Mobility, or Volume .................. VI - 5-23

5A.A.1 Alternative No. N-1: No Action .................... VI - 5-23

5.4.4.2 Alternative No. N-2: Continued Operation of the

North Boundary Containment System With

Improvements as Necessary ............ *'*''**'  VI - 5-23

5.4.4.3 Alternative No. N-4: Interim Response Action A ....... VI- 5-23

5.4.4.4 Alternative No. N-5: Expansion I to Interim

Response Action A Vl- 5-24

5.4.4.5 Alternative No. NW- 1: No Action .................. VI- 5-25

5.4.4.6 Alternative No. NW-12: Continued Operation of

Northwest Boundary Containment System With

Improvements as Necessary ........................ Vl- 5-25

5.4.5 Short-term Effectiveness ................................ VI- 5-25

5.4.5.1 Alternative No. N-1: No Action .................... Vl- 5-26

5.4.5.1.1 Protection of Community and Workers ...... VI- 5-26

5.4.5.1.2 Adverse Environmental Impacts ........... VI- 5-26

5.4.5.1.3 Implementation Period .................. VI - 5-26

5.4.5.2 Alternative No. N-2: Continued Operation of

North Boundary Containment System ................ VI - 5-26

5.4.5.2.1 Protection of Community and Workers ...... VI - 5-26

5.4.5.2.2 Adverse Environmental Impacts ........... VI- 5-26

5.4.5.2.3 Implementation Period .................. VI- 5-26

5.4.5.3 Alternative No. N-4: Interim Response Action A ........ VI- 5-27

5.4.5.3.1 Protection of Community and Workers ...... VI- 5-27

5.4.5.3.2 Adverse Environmental Impacts ........... V1- 5-27

5.4.5.3.3 Implementation Period .................. VI- 5-27

5.4.5.4 Alternative No. N-5: Expansion I to Interim

Response Actoin A .............................. VI- 5-27

5.4.5.4.1 Protection of Community and Workers ...... VI- 5-27

5.4.5.4.2 Adverse Enviornmental Impacts ........... VI - 5-27

5.4.5.4.3 Implementation Period .................. VI- 5-28

5.4.5.5 Alternative No. NW-I: No Action .................. VI - 5-28

5.4.5.5.1 Protection of Community and Workers ...... VI - 5-28

5.4.5.5.2 Adverse Environmental Impacts ........... VI- 5-28

5.4.5.5.3 Implementation Period .................. VI- 5-28

5.4.5.6 Alternative No. NW-2: Continued Operation of

Northwest Boundary Containment System With

Improvements as Necessary ........................ VI- 5-28

5.4.5.6.1 Protection of Community and Workers ...... VI- 5-28

5.4.5.6.2 Adverse Environmental Impacts ........... VI- 5-29

5.4.5.6.3 Implementation Period .................. VI- 5-29

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Page

5.4.6 Im plem entability ....................................... VI - 5-29

5.4.6.1 Alternative No. N-1: No Action .................... VI - 5-29

5.4.6.2 Alternative No. N-2: Continued Operation of North

Boundary Containment System With Improvements as

Necessary ..................................... VI - 5-29

5.4.6.3 Alternative No. N-4: Interim Response Action A ....... VI - 5-30

5.4.6.4 Alternative No. N-5: Expansion I to Interim

Response Action A .............................. VI - 5-30

5.4.6.5 Alternative No. NW-1: No Further Action ............ VI - 5-30

5.4.6.6 Alternative No. NW-2: Continued Operation of the

Northwest Boundary Containment System With

Improvements as Necessary ........................ VI - 5-31

5.4.7 Cost .......... ** - **- - - :''**''*'***'******** * * VI- 5-31

5.4.7.1 Alternative No. N-1: No Action .................... Vl- 5-31

5.4.7.2 Alternative No. N-2: Continued Operation of the North

Boundary Containment System With Improvements as

N ecessarN .................. .................. V l - 5-31

5.4.7.3 Alternative No. N-4: Interim Response Action A ....... VI- 5-32

5.4.7.4 Alternative No. N-5: Expansion I to Interim

Response Action A .............................. VI - 5-32

5.4.7.5 Alternative No. NW-1: No Action .................. VI - 5-32

5.4.7.6 Alternative No. NW-2: Continued Operation of the

Northwest Boundary Containment System With

Improvements as Necessary ........................ VI - 5-32

5.5 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES ........ VI - 5-33

5.5.1 Comparison of Alternatives - North Plume Group .............. Vl- 5-33

5.5.1.1 Overall Protection of Human Health and the

Environm ent ................................... VI - 5-33

5.5.1.2 Compliance With Applicable or Relevant and

Appropriate Requirements ........................ VI - 5-34

5.5.1.3 Long-term Effectiveness and Permanence ............. VI - 5-34

5.5.1.4 Reduction in Toxicity, Mobility, and Volume .......... VI - 5-34

5.5.1.5 Short-term Effectiveness .......................... VI - 5-35

5.5.1.6 Implementability ................................ VI - 5-35

5.5.1.7 Cost ................... * * * * ' * 6 r* * * ' * * * ** * * '' ' VI - 5-36

5.5.2 Comparison of Alternatives - Northwest Plume oup .......... VI - 5-36

5.5.2.1 Overall Protection of Human Health and the

Environm ent ................................... VI - 5-37

5.5.2.2 Compliance With Applicable or Relevant and

Appropriate Requirements ........................ VI - 5-37

5.5.2.3 Long-term Effectiveness and Permanence ............. VI - 5-37

5.5.2.4 Reduction in Toxicity, Mobility, and Volume .......... VI- 5-37

5.5.2.5 Short-term Effectiveness .......................... VI - 5-38

5.5.2.6 Im plementability ................................ VI - 5-38

5.5.2.7 Cost ......................... VI - 5-38

5.5.3 Ranking of Alternatives - North Plume Group and

Northwest Plume Group ................................. VI - 5-39

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TABLE OF CONTENTS

(Continued)

Page

6.0 SELECTION OF THE PREFERRED SITEWIDE ALTERNATIVE ........... VI - 6-1

6.1 IDENTIFICATION OF THE PREFERRED SITEWIDE ALTERNATIVE . . VI - 6-1

6.1.1 Preferred Sitewide Alternative Description ................... VI - 6-3

6.1.1.1 Alternative No. N-4: Interim Response Action A ....... VI - 6-3

6.1.1.2 Alternative No. NW-2: Continued Operation of the

Northwest Boundary Control System With

Improvements as Necessary ........................ VI - 6-6

6.2 CONSISTENCY WITH THE REQUIREMENTS OF CERCLA

AND THE NATIONAL CONTINGENCY PLAN .................... VI - 6-7

6.2.1 Principal Threats Addressed by the Preferred Sitewide

Alternative VI - 6-7

6.2.2 Consistency With the Statutory Requirements of CERCLA in

Section 121 ........................................... V I - 6-7

6.2. 1 Protection of Human Health and the Environment ....... VI - 6-7

6.2- Compliance With Applicable or Relevant and

Appropriate Requirements ........................ VI - 6-8

6.2.2.3 Cost-effectiveness ...................... *''***'*' VI - 6-8

6.2.21.4 Utilization of Permanent Solutions to the Maximum Extent

Practicable .................................... V I - 6-8

6.2.3 Consistency With the National Contingency Plan ............... VI - 6-8

6.3 SU M M A RY ................................................ VI - 6-9

7.0 REFERENCES ................................................... VI - 7-1

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(Continued)

VOLUME VII - FEASIBILITY STUDY

LIST OF APPENDIXES

A APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS (ARARs)

ANALYSIS

B WETLAND DELINEATION AND ASSESSMENT

C DERIVATION OF HEALTH-BASED CRITERIA AND ECOLOGICAL CRITERIA

D SECOND LEVEL PROCESS OPTION SCREENING

E GROUNDWATER MODELING RESULTS SUMMARY

F COST ESTIMATES

VOLUME VIII - RESPONSES TO COMMENTS

U.S. ENVIRONMENTAL PROTECTION AGENCY

U.S. FISH AND WILDLIFE SERVICE

COLORADO DEPARTMENT OF HEALTH

SHELL OIL COMPANY

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LIST OF TABLES

Table No.

Volume II - ENDANGERMENT ASSESSMENT

1.0-1 Data Needs in Each Medium

1.3.1-1 Statistical Comparison With Background - Groundwater

1.3.1-2 Chemicals of Concern - Groundwater

1.3.1-3 Summarv of Available Information on Toxicity and Essentiality of Calcium, Iron,

Potassium, Magnesium, and Sodium

1.3.2-1 Statistical Comparison With Background - Surface Water (First Creek)

1.3.2-2 Chemicals of Concern - Surface Water (First Creek)

1.3.2-3 Statistical Comparison With Background - Surface Water (Canals)

1.3.2-4 Statistical Comparison With Background - Surface Water (Barr Lake)

1.3.2-5 Statistical Comparison With Background - Sediment (First Creek)

1.3.2-6 Statistical Comparison With Background - Sediment (O'Brian Canal)

1.3.2-7 Statistical Comparison With Background - Sediment (Barr Lake)

1.3.3-1 Statistical Comparison With Background - Surf icial Soil

2.1-1 Henry's Law Constant (Dimensionless) for Organic Groundwater Chemicals of

Concern

2.1-2 Molecular Diffusivity in Air and Water (m 2 /day)

2.1-3 Solubility (mg/1) and Vapor Pressure (torr) for Organic Groundwater Chemicals

of Concern

2.1-4 Octanol/Water Partition Coefficients (log KOW)

2.1-5 Adsorption Coefficient (1/kg) for Chemicals Elevated in Soil or Sediment

2.1-6 Uptake to Roots, K,,, (1/kg), for Organic Groundwater Chemicals of Concern

2.1-7 Uptake to Plants, Kwp (1/kg), for Organic Groundwater Chemicals of Concern

2.1-8 Plant Uptake Coefficients, K., (Dimensionless), for Chemicals of Concern in

Offpost Surficial Soil

2.1-9 Plant Uptake Coefficients, K.., for Chemicals of Concern in Offpost Surficial

Soil

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LIST OF TABLES

(Continued)

2.1-10 Beef Bioaccumulation Coefficients, KPM1 for All Chemicals of Concern

2.1-11 Milk Bioaccumulation Coefficients, Kpd, for All Chemicals of Concern

2.1-12 Fish Bioaccumulation Coefficients, K,,f (1/kg), for Surface-Water Chemicals of

Concern

2.2.2.1.2-1 Population by Land-Use Area

--. 2.1.2-2 Land Use by Land-Use Area (in acres)

2.2.2.1.2-3 Potentially Sensitive Subpopulations

2.2.2.4.1-1 Well-Use Data From Colorado State Master Extract Register

2.2.2.4.1-2 Well-Use Data From Consumptive Use Phase 1, 11, and III Studies

Preliminarv Estimate of the Number of Wells b,, Well Use in the Offpost

Operable Unit

2.2.'( '_. 4.1 - 4 Well Use Data From the Tri-Countv Health Department Survey

2.2.2.4.1-5 Combined Estimate of the Number of Wells bv Well Use in the Offpost Operable

Unit

2.3.3.1-1 Exposure Pathways: Inhalation Route

2.3.3.2-1 Exposure Pathways: Dermal Route

2.3.3.3-1 Exposure Pathways: Ingestion Route

2.4.2.4-1 Non chemical- specific Parameters Used in Bioaccumulation Models

2.4.2.5-1 Concentration of Aldrin Plus Dieldrin in Zone 3

2.4.2.5-2 Chemical -specific Properties of Aldrin and Dieldrin

2.4.2.6-1 Exposure Concentrations, Groundwater, Zone 1

2.4.2.6-2 Exposure Concentrations, Groundwater, Zone 2 (Northern Paleochannel)

2.4.2.6-3 Exposure Concentrations, Groundwater, Zone 3 (96th Avenue and Peoria Street)

2.4.2.6-4 Exposure Concentrations, Groundwater, Zone 4 (First Creek Paleochannel)

2.4.2.6-5 Exposure Concentrations, Groundwater, Zone 5 (Northwest Boundary)

2.4.2.6-6 Exposure Concentrations, Groundwater, Zone 6

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(Continued)

2.4.2.6-7 Estimated Future Exposure Concentrations for Aldrin and Dieldrin, Groundwater, Zones 3 and 4

2.4.2.6-8 Exposure Concentrations in Surface Water

2.4.2.6-9 Exposure Concentrations in Surficial Soil and Sediments (mg/kg)

2.4.2.6-10 Reasonable Maximum Exposure Concentrations in Vegetables: Maximum

Concentrations Estimated in Anv Zone

2.4.2.6-11 Reasonable Maximum Exposure Concentrations in Dairy and Meat Products:

Maximum Concentration Estimated in Any Zone

2.4.2.6-12 Reasonable Maximum Exposure Concentration in Eggs (Zones 1, 2, and 6)

2.4.3-1 Summary of Land Use Scenarios Used to Estimate Reasonable Maximum

Exposure Intakes by Zone

2.4.3.1-1 Dermal Absorption from Soil/Sediment

2.4.3.2-1 Exposure Factors: Ingestion Rates

2.4.3.2 - I a Parameters Used in Time-weighted Average Intakes Calculation (Milk and Soil

Ingestion)

2.4.3.2-2 Exposure Factors: Exposure Frequency and Duration

2.4.3.2-3 Exposure Factors: Physiology

2.4.4-1 Exposure Factors: Commercial/ Industrial (Reasonable Maximum Exposure)

2.4.4-2 Exposure Factors: Commercial/Industrial (Most Likely Exposure)

2.4.5.1-1 Sensitivity Analysis Summary

2.4.5.5.3-1 Uncertainty Analysis Results

3.1-1 Hierarchy of Documents Referenced Regarding Toxicity Data

3.1-2 Toxicity Data for Rocky Mountain Arsenal Offpost Chemicals of Concern

3.1-3 Noncarcinogenic Reference Doses and Potential Noncarcinogenic Effects

3.1-4 Cancer Slope Factors and Potential Carcinogenic Effects of Carcinogenic

Operable Unit Offpost Chemicals of Concern

3.1-5 Regulatory Criteria for Rocky Mountain Arsenal Offpost Operable Unit,

Chemicals of Concern

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LIST OF TABLES

(Continued)

3.3.1-1 Reference Media Concentrations for Vegetation and Aquatic Organisms

3.3.3-1 Toxicity Reference Values for Avian and Terrestrial Vertebrate Species of

Concern Identified at Rocky Mountain Arsenal

3.3.3-2 References for Critical Toxicity Studies Used to Derive Terrestrial Toxicity

Reference Values Listed in Table 3.3.3-1

3.3.3.2.1 -1 Nonprimate Mammalian Oral LD50 Data

Volume III

4.0-1 Target Organ- or System-specific Chemicals of Concern

4.1.1-1 Summary of Residential Hypothetical Future Carcinogenic Risks: Reasonable

Maximum Exposure

4.1.1-2 Summarv of Residential Child Chronic Combined Noncarcinogenic Hazard

Indices (H]s >1)

4.1.1-3 Contribution of Dieldrin and Other Chemicals to the Child Acute Hepatic Hazard

Index

4.1.1-4 Summary of Residential Hypothetical Future Reasonable Maximum Exposure

Subchronic Hazard Indices: Children

4.1.1-5 Summary of Residential Hypothetical Future Reasonable Maximum Exposure

Subchronic Hazard Indices: Adult Females

4.1.1-6 Comparison of Residential Reasonable Maximum Exposure and Most Likely

Exposure Hypothetical Future Carcinogenic Risks by Zone

5.1.2-1 Wildlife Species Observed in Offpost Operable Unit: Winter 1989-90

5.1.4-1 Chemicals of Concern and Tissue Chemicals of Concern for the Offpost

Ecological Risk Assessment

5.2.1-1 Terrestrial Species Selected as Indicators of Ecological Impacts

5.2.1-2 Aquatic/Wetland Species in Relation to Indicator Species Selection Criteria

5.2.2-1 Potential Exposure Pathways for Biota

5.2.3-1 Exposure Point Concentrations for Soil, Surface Water, and Sediment Used for

the Offpost Ecological Assessment

5.2.5.1-1 Dietary Fractions for Each of the Species in the Terrestrial Food Web

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(Continued)

5.2.5.2-1 Predicted Tissue Concentrations (mg/kg) for the Terrestial Food Web Ecological

Receptors

5.2.5.4-1 Predicted Tissue Concentrations (mg/kg) for the Aquatic Food Web Ecological

Receptors on the Basis of Surface-Water Concentrations

5.2.5.4-2 Predicted Tissue Concentrations (mg/kg) for the Aquatic Food Web Ecological

Receptors on the Basis of Sediment Concentrations

5.3.1-1 Summarv of Intakes from Zone 3 Soil, Surface Water, and Diet for the Bald Eagle

5.3.1-2 Summarv of Intakes From Zone 3 Soil, Surface Water, and Diet for the American

Kestrel

5.3.1-3 Summary of Intakes From Zone 3 Soil, Surface Water, and Diet for the Great

Horned Owl

5.3.1-4 Summarv of Intakes From Zone 3 Soil, Surface Water. and Diet for the Deer

Mouse

5.3.1-5 Summary of Intakes From Zone 3 Soil. Surface Water, and Diet for the Prairie

Dog

5.3.2-1 Summarv of Intakes From Zone 3 Sediment, Surface Water, and Diet for the

Great Blue Heron

5.3.2-2 Summary of Intakes From Zone 3 Sediment, Surface Water, and Diet for the

Mallard Duck

5.3.4-1 Summary of Chicken Hazard Quotient by Zone, Offpost Operable Unit

Volume V - FEASIBILITY STUDY

2.2.1-1 Offpost Operable Unit Carcinogenic Risks for Each Medium

2.3.1-1 Offpost Operable Unit Groundwater Chemicals of Concern

2.5.2-1 Preliminary Chemical -specific Applicable or Relevant and Appropriate

Requirements for Groundwater

2.5.2-2 Health-based Criteria for Groundwater Chemicals of Concern Without Applicable

or Relevant and Appropriate Requirements

2.5.2-3 Preliminary Remediation Goals for Offpost Operable Unit Groundwater

2.8.1-1 Screening of Process Options for Groundwater

2.10.1-1 Selection of Representative Process Options for Groundwater

20000,317.10 - 1-toc

0306111992 xxiii
LIST OF TABLES

(Continued)

Volume VI

3.5.1-1 Groundwater Alternatives for the North Plume Group

3.5.1.7-1 Summary of Preliminary North Plume Group Groundwater Alternatives

3.5.2-1 Groundwater Alternatives for the Northwest Plume Group

3.5.2.5-1 Summary of Preliminary Northwest Plume Group Groundwater Alternatives

4.2.1.7-1 Summary of Screening of Groundwater Alternatives; North Plume Group

4.2.2.5-1 Summary of Screening of Groundwater Alternatives; Northwest Plume Group

5.5.3-1 Summarv of the Detailed Analysis and Ranking of Groundwater Alternatives for

the North Plume Group

5.5.3-2 Summary of the Detailed Analysis and Ranking of Groundwater Alternatives for

the Northwest Plume Group

20000,317.10 - 1-toc

0306111892 xx1v
LIST OF FIGURES

Figure No.

Volume I - INTRODUCTION

I Location Map of Onpost Operable Unit, Rocky Mountain Arsenal

2 Offpost Area, Rocky Mountain Arsenal

3 Distribution of Diisopropylmethyl Phosphonate (DIMP) in the Offpost

Unconfined Flow System

4 Distribution of Dicyclopentadiene in the Offpost Unconfined Flow System

5 Distribution of Dieldrin in the Offpost Unconfined Flow System

6 Distribution of Endrin in the Offpost Unconfined Flow System

7 Distribution of Chloroform in the Offpost Unconfined Flow System

8 Distribution of Chlorobenzene in the Offpost Unconfined Flow System

9 Distribution of Dibromochloropropane in the Offpost Unconfined Flow System

10 Distribution of Trichloroethene (TRCLE) in the Offpost Unconfined Flow

System

I I Distribution of Tetrachloroethene in the Offpost Unconfined Flow System

12 Distribution of Arsenic in the Offpost Unconfined Flow System

13 Distribution of Chloride in the Offpost Unconfined Flow System

14 Distribution of Fluoride in the Offpost Unconfined Flow System

15 Offpost Operable Unit Confined Denver Formation Monitoring Well Network

16 Distribution of Organochlorine Pesticides Detected in Offpost Soil

17 Distribution of Organochlorine Pesticides Detected in 96th Avenue Area Offpost

Soil

18 Distribution of Organic Compounds Detected in Offpost Operable Unit Surface

Water

19 Distribution of Organic Compounds Detected in Offpost Operable Unit StreamBottom Sediment

20000,317.10 - 1-toc

0306111892 xxv
LIST OF FIGURES

(Continued)

Volume Il - ENDANGERMENT ASSESSMENT

1.0-1 Preliminary Site Conceptual Model, Pre-Remedial Investigation, Offpost

Operable Unit

1.2-1 Offpost Operable Unit Background Surficial Soil Sampling Locations

1.2-2 Offpost Operable Unit Designated Surficial Soil Data Sets for Comparison With

Background

1. 2' - 3 Offpost Operable Unit First Creek Surface-Water Sampling Locations

1.2-4 Offpost Operable Unit First Creek Sediment Sampling Locations

1.2-5 Offpost Operable Unit Surface-Water Sampling Locations

1.2-6 Offpost Operable Unit Sediment Sampling Locations

2.2.2.1.1-1 Offpost Operable Unit Land Use Areas and Consumptive Use Phase 11 Study

Area

2.2.2-.1.2-1 Offpost Operable Unit - Future Land Use

2.2.2.1.2-2 Offpost Operable Unit Study Area Selected Current Zoning Map, 1991

2.3.1-1 Site Conceptual Model Offpost Operable Unit

2.4.1-1 Offpost Operable Unit Zones Major Pathways of Groundwater Contaminant

Transport

2.4.1-2 Offpost Operable Unit Endangerment Assessment Zones

2.4.2.6-1 Estimated Future Exposure Concentrations for Dieldrin, Groundwater, Zones 3

and 4

2.4.2.6-2 Estimated Future Exposure Concentrations for Aldrin, Groundwater, Zones 3

and 4

2.4.3.3-1 Offpost Operable Unit Chronic Intake of Chloroform by Pathway and

Groundwater Zone - Residential Scenarios

2.4.3.3-2 Offpost Operable Unit Intake of Dieldrin by Zone and Pathway - Residential

Scenario

2.4.5-1 Offpost Operable Unit Histograms Describing the Distribution of Ingestion Rate

of Locally Produced Milk (IRd, kg/day) for the Child Chronic and Lifetime

Scenarios - Residential

20000,317.10 - 1-toc

0306111992 xxvi
LIST OF FIGURES

(Continued)

2.4.5-2 Offpost Operable Unit Histograms Describing the Distribution of Ingestion Rate

of Locally Produced Vegetables (IRv, kg/day) for the Child Chronic and Lifetime

Scenarios - Residential

2.4.5-3 Offpost Operable Unit Histograms Describing the Distribution of Ingestion Rate

of Locally Produced Meat (IRm, kg/day Fresh Weight) for the Child Chronic and

Lifetime Scenarios - Residential

2.4.5.5.2-1 Offpost Operable Unit Distribution of Lifetime Oral Intake of Dieldrin in Zone 3

(mg/kg/day) - Residential

2.4.5.5.2-2 Off'post Operable Unit Uncertainty in the Mean Concentration of Dieldrin in

Groundwater (mg/1) in Zone 3

2.4.5.5.2-3 Offpost Operable Unit Uncertainty in the Mean Concentration of Dieldrin in

First Creek Surface Water (mg/1)

2.4.5.5.2-4 Offpost Operable Unit Uncertainty in the Mean Concentration of Aldrin and

Dieldrin in Surface Soil of Zone 3 (mg/1)

2.4.5.5.2-5 Offpost Operable Unit Uncertainty in the Mean Concentration of Dieldrin in

Vegetables (CFv, mg/kg, Fresh Weight) in Zone 3

2.4.5.5.2-6 Offpost Operable Unit Distribution of Child Chronic Oral Intake of DIMP in

Zone 4 (mg/kg/day) - Residential

2.4.5.5.2-7 Offpost Operable Unit Distribution of Lifetime Oral Intake of Chloroform in

Zone 2 (mg/kg/day) - Residential

2.4.5.5.2-8 Offpost Operable Unit Distribution of Lifetime Inhalation of Chloroform in

Zone 2 (mg/kg/day) - Residential

3.3.1-1 Methodology for Determining Water and Soil Reference Media Concentrations

for Vegetation and Aquatic Organisms

3.3.3-1 Methodology to Derive Toxicity Reference Values (TRVs) From Class-specific

Toxicity Data

Volume III

4.1.1-1 Offpost Operable Unit Combined Carcinogenic Risks (All Pathways) by

Groundwater Zone - Residual Scenarios

4.1.1-2 Offpost Operable Unit Child Resident Hazard Indices Described for Toxic

Chemicals and Exposure Pathways - Residential Scenarios

4.1.1-3 Offpost Operable Unit Contributors to Carcinogenic Risks - Residential Scenario

20000,317.10 - 1-toc

0306111992 xxvii
LIST OF FIGURES

(Continued)

4.1.1-4 Carcinogenic Risks Described by Chemical, Medium, and Exposure Pathway -

Zone I A, Lifetime Rural Resident, RME

4.1.1-5 Carcinogenic Risks Described by Chemical, Medium, and Exposure Pathway -

Zone 113, Lifetime Rural Resident, RME

4.1.1-6 Carcinogenic Risks Described by Chemical, Medium, and Exposure Pathway -

Zone IC, Lifetime Rural Resident, RME

4.1.1-7 Carcinogenic Risks Described by Chemical, Medium, and Exposure Pathway -

Zone 2. Lifetime Rural Resident, RME

4.1.1-8 Carcinogenic Risks Described by Chemical, Medium. and Exposure Pathway -

Zone 3, Lifetime Urban Resident, RME

4.1.1-9 Carcinogenic Risks Described by Chemical, Medium, and Exposure Pathway -

Zone 4. Lifetime Urban Resident, RME

4.1.1-10 Carcinogenic Risks Described by Chemical, Medium, and Exposure Pathway -

Zone 5, Commercial/ Industrial, RME

4.1.1-11 Carcinogenic Risks Described by Chemical, Medium, and Exposure Pathway -

Zone 6, Lifetime Rural Resident, RME

4.1.1-12 Child Acute Liver Hazard Indices

4.1.1-13 Subchronic Child Liver Hazard Indices, Maximum and Minimum of Range

4.2.1-1 Noncarcinogenic Hazard Indices Zone 5; Adult Commercial/Industrial; Chronic

RME

5.1.1-1 Offpost Operable Unit Biota Sampling Locations

5.1.1-2 Habitat Map for First Creek Portion of Offpost Operable Unit

5.2.2-1 Ecological Site Conceptual Model Offpost Operable Unit

5.2.5.1-1 Offpost Operable Unit Terrestrial Food Web

5.2.5.3-1 Offpost Operable Unit Aquatic Food Web

5.2.6.5-1 Offpost Operable Unit Agricultural Food Web

20000,317.10 - 1-toc

0306111892 xxviii
LIST OF FIGURES

(Continued)

Volume V - FEASIBILITY STUDY

2.5.1-1 Offpost Operable Unit Feasibility Study Contaminant Distribution Zones

2.6.1 Areas of Exceedances of Groundwater PRGs in the Offpost Unconfined Flow

System

2.8-1 Groundwater Process Options

2.8.1-1 Results of Universal Screening of Groundwater Process Options

2.9-1 Results of the Second Level Screening of Groundwater Process Options

2.10.1-1 Selected Representative Process Options for Development of Groundwater

Remedial Alternatives

Volume VI

3.2.1-1 Offpost Operable Unit Groundwater Plume Groups

3.5.1.4-1 Alternative No. N-4: Interim Response Action A

3.5.1.5-1 Alternative No. N-5: Expansion I to Interim Response Action A

3.5.1.6-1 Alternative No. N-6: Expansion 2 to Interim Response Action A

3.5.2.4-1 Alternative No. NW-4: Northwest Plume Group Extraction/ Recharge System

20000,317.10 - 1-toc

0306111892 xxix
4.0 HUMAN RISK CHARACTERIZATION

This section integrates, summarizes, and interprets information from the exposure and

toxicity assessments for the 0) rural residential and (2) commercial /industrial and recreational

scenarios, The procedures used are presented in RAGS (EPA, 1989a) and include the following:

1. Determine Hazard Indices (HI) by comparing chronic and acute/subchronic intake

estimates to RfDs to evaluate the potential for noncarcinogenic effects. An HI greater

than 1.0 may warrant further evaluation.

2. Multiply estimated lifetime intakes by cancer SFs to estimate the UL95 of individual

lifetime cancer risk under the RME assumptions.

3. Add His and cancer risks of multiple contaminants that are expected to cause similar

effects.

4. Interpret the results by identifying chemical pathways and media contributing substantial]y to the overall risks and characterizing the uncertainties associated with the

assessment.

Based on information presented in the toxicity assessment, COCs were categorized with

respect to the target organ,'system that was affected in the critical study, or studies, used to define

the RfD. Some chemicals affect more than one organ or system at similar doses and may be

placed in multiple categories. His are summed within categories. The target organ-specific COCs

are presented in Table 4.0- 1. The majority of chemicals presenting noncarcinogenic effects (i.e.,

HI >I) affect the liver, so additivity of chemical -specific His is most significant to the liver.

Individual lifetime cancer risks are summed for all carcinogens regardless of target organ and

weight-of -evidence classification (EPA, 1989a) to estimate the additive individual lifetime cancer

risk. It is appropriate, however, to distinguish between carcinogens on the basis of target organ

and weight of evidence as part of the risk management process, as presented and described in

Section 4.3.

Uncertainties in the risk characterization represent the combined uncertainties of the

exposure and toxicity assessments. Overall, these uncertainties were resolved by conservative

assumptions. The quantitative uncertainty analysis of the estimated intakes indicates that the

RME intake estimate is at the 98th to 99.8th percentile of the expected range of hypothetical

20000,317.10(3) - OEA

0306111892 111 - 4-1
intakes among the exposed population. Hypothetically, most individuals would experience much

lower intakes. For the Offpost OU, the 50th percentile of the uncertainty analysis resultant

distribution is 10 to 100 times lower than the RME, and the 95th percentile is a factor of 3 lower

than the calculated RME. This is an important finding to consider in the evaluation of the

hypothetical risks described in subsequent sections since it suggests that exposures may be at or

above the 99th percentile and therefore meets the definition of an RME (EPA, 1989a).

The quantitative uncertainty analysis did not address the uncertainty associated with

infrequently detected chemicals. The uncertainty is resolved conservatively by the replacement

method, which assumes nondetections are equal to one-half the CRL (Haas and Scheff, 1990).

A substantial portion of the estimated carcinogenic risk is attributable to EPA category B2

(probable human) carcinogens, particularly chloroform, and dieldrin. Category B2 designates

chemicals for which there is sufficient evidence that the chemicals cause cancer in laboratory

animals, but insufficient data that they are carcinogenic in humans. Because much of the total

carcinogenic risk is based on the extrapolation of animal data to an assessment of human health

effects, it is possible that these chemicals are not carcinogenic to humans at the estimated

exposure levels.

A major fraction of the estimated noncarcinogenic HIs also rests on RfDs derived from

extrapolation of laboratory animal data to an assessment of human health effects. Considering

uncertainties associated with such extrapolation, as well as other factors (Section 3.1), the RfDs

that critically determine the higher HIs reported here (e.g., liver toxicants and DIMP) incorporate

uncertainty factors ranging from 100 to 1000.

4.1 RESIDENTIAL SCENARIO

As required by the NCP and RAGS (EPA, 1990a; EPA, 1989a), this section focuses on the

estimation of an RME for the residential scenario, including the potential for future exposures

that are not occurring currenfly. The alluvial aquifer is used for domestic supply only in zones

I A, I C, and 6. Local agencies plan to develop a community water system, and the water supplied

would come from uncontaminated sources or would be treated in compliance with the Safe

20000,317.10(3) - OEA

0306111892 111 - 4-2
Drinking Water Act (SACWSD, 1991). Consequently, it is unlikely that residents of the Offpost

OU are being or would be exposed to chemicals in groundwater at the RME intake rates.

Groundwater is the ultimate source of approximately 80 to 90 percent of chemical intakes

estimated under the RME scenario. Nonetheless, it was assumed conservatively that use of the

alluvial aquifer as the primary domestic water supply could occur; therefore, the EA evaluated the

use of the alluvial aquifer.

Parts of the offpost operable unit are expected to remain rural for the foreseeable future. In

these areas, specifically zones 1, 2, and 6, a rural residential scenario in which residents keep

chickens and/or cattle and consume their eggs, milk, and meat, is the land use likely to result in

RME exposures. In other areas (zones 3 and 4), an urban residential land use, excluding farm

animals, is possible and represents the RME. Finally, zone 5 is not expected to develop

residentially, and commercial/ industrial scenarios represent the RME.

Chemical intakes will vary widely among a potentially exposed residential population. The

degree of variability is shown by the quantitative uncertainty analysis results presented in

Section 2.4.5.5 (Volume II). Hypothetically, 91 to 99.8 percent of the population would experience

intakes less than the calculated RME. According to the results of the quantitative uncertainty

analysis (Section 2.4.5), the calculated RMEs for the Offpost OU have been found to be in the

range of the 99th percentile and to exceed the 95th percentile by approximately 3-fold.

Recognizing the conservative aspects of this assessment, consistent with relevant guidance,

most of this section is devoted to characterization of the risks at RME intake levels.

4.1.1 Hypothetical Future Exposures

Hypothetical future HIs and carcinogenic risks were calculated by zone, chemical, and

pathway. Consistent with guidance (EPA, 1989a), zone carcinogenic risks have been rounded to

one significant figure in the text and tables. The term "hypothetical future" is intended to address

the conditions that exposure is only assumed (hypothetical) for the future scenario, that additional

remediation is absent, and that the risks and HIs are derived from risk assessment methodologies,

including low-dose and interspecies extrapolation, that are difficult to verify for humans.

20000,317.10(3) - OEA

0306111892 111 - 4-3
Additive risks for each chemical (all pathways) and each pathway (all chemicals) were determined

for each zone, leading to grand totals by zone for each target organ (noncarcinogenic) and total

individual lifetime cancer risk. Results of these calculations are presented in a series of matrices

in Appendix G. With respect to cancer risk, the cancer SFs used in these calculations are

established at the UL95. Based on the uncertainty analyses, hypothetical risks cited in this section

are likely overstated by 3-fold compared to the 95th percentile. Results of the assessment for

carcinogens are summarized in Figure 4. 1. 1 - 1, which illustrates the data presented in

Table 4. 1. 1 - 1.

Hypothetical future RME cancer risks may exceed I X 10-4 in zones 2, 3, and 4 with

maximum risks of approximately 3 x 10-4 in zone 3. The hypothetical future combined risks from

exposure to aldrin, arsenic, atrazine chloroform, and dieldrin account for more than 82 percent of

the additive risk in each zone.

The results of the assessment of noncarcinogenic hypothetical future His are summarized in

Table 4.1.1-2, which lists all child chronic combined His that exceed 1. Child chronic His are

shown because His are greater for children than adults based on intake rates. Acute/subchronic

results will be described separatel\.

Chlordane, chloroform, dicyclopentadiene, dieldrin, DIMP, and manganese are the only

chemicals that contribute significantly to hypothetical future His greater than 1.

Reviewing these results, it is apparent that only a few COCs contribute substantially to

hypothetical future cancer risks and His. The majority of the discussion will emphasize the

COCs, arsenic, chloroform, DIMP, and dieldrin.

4.1.1.1 Hyvothetical Carcinogenic Risks Related to Background

As indicated in Section 2.4.2.5, dieldrin concentrations in surficial soil outside zones 3 and 4

do not appear to be attributable to RMA but instead to agricultural practices. However, the risk

associated with the dieldrin soil data was quantified. The hypothetical risk associated with

dieldrin in soil in zones I A, I B, I C, '41, 5, and 6 may be as great as 4 x 10-5. This risk may not be

attributable to RMA sources.

20000,317.10(3) - OEA

0306111892 111 - 4-4
Naturally occurring arsenic also contributes to carcinogenic risk in several zones. The UL95

concentration of arsenic in the Offpost OU comparison data set was 1.86 ug/l; an additional

comparison group located in the onpost southeastern tier had an UL95 arsenic concentration of

3.13 AgIll. The additive carcinogenic risk associated with these concentrations ranges from

4.4 x 10-5 to 7.4 x 10-5 for the offpost and onpost comparison data sets.

Combining the hypothetical risks from dieldrin in soil outside of zones 3 and 4 (4 x 10-5)

and from arsenic in groundwater (4.4 x 10-5) yields a risk of 8 x 10-5 from sources that are either

non-RMA related or naturalIN: occurring background risks.

4.1.1.2 Child Chronic Hwothetical Future Hazard Indices

The hypothetical future HI for liver toxicants exceeds I in zones 2, 3, and 4, with a

maximum HI of 2 in zone 3. Therefore, particularly in zones 2, 3, and 4, there is a hypothetical

hazard of liver toxicity from future chronic exposure at RME intake levels. The hypothetical

hazard of liver toxicity is predominantly attributable to exposure to chloroform, chlordane,

dicyclopentadine, and dieldrin. The OCPs and the chlorinated aliphatics are included in the list of

liver toxicants. Figure 4.1.1-'.2 shows the chemicals and pathways that pose the greatest

hypothet-ical occurrence of liver toxicity. No single chemical or single pathway yields a hazard

quotient greater than 1. Exposure by inhalation and ingestion routes to chloroform in shallow

groundwater assumed to be used for domestic supply contributes significantly to the combined

liver hazard index of 2 estimated for zone 2. Exposure to dieldrin in vegetables is the largest

contribution to the combined liver hazard index of 2 in zone 3, and exposure to chlordane in

groundwater is the largest contributor in zone 4.

Two chemicals have the potential to affect the CNS for which the hypothetical future RME

HI exceeds I in zones 2 and 4 (Table 4.1.1-2). DIMP attains a maximum hypothetical future HI of

3.1 in zone 4 (Appendix G) and, in combination with manganese, produces an RME HI of 3.7 in

zone 4. These chemicals are elevated in groundwater, and all exposure is oral. Uptake by

vegetable crops when groundwater is used for irrigation contributes to exposure and HIs for these

chemicals.

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0306111892 111 - 4-5
4.1.1.3 Adult Chronic Hvvothetical Future Hazard Indices

As presented in Section 2.4.3, adult chronic intakes are consistently less than child chronic

intakes, and His are also lower in direct proportion. The greatest hypothetical future HI for the

adult chronic scenario is 1.3 for liver toxicants in zone 3, with dieldrin the largest contributor, and

is approximately one-half the value of 2 estimated for children in the same zone. Hypothetical

future adult chronic His greater than I occur for liver toxicants in zones 3 and 4. DIMP is the

major contributor to a hypothetical future HI of 2.4 in zone 4.

4.1.1.4 HvI)othetical Future Carcinogenic Risk

The hypothetical future risk associated with each carcinogenic chemical by zone is shown in

Figure 4.1.1-3. These risks may be overstated by a factor of 3, according to the results of the

uncertainty analysis. These results are based on the RME assumptions and an UL95 for the cancer

SF. Clearly, hypothetical future carcinogenic risks are greater in zones 2, 3, and 4 than in other

zones. Chloroform, arsenic, and dieldrin present the highest incremental risks. Chloroform

risks are limited primarily to zone 2, and risk attributable to dieldrin is distributed more

uniformly. Figure 4.1.1-3 further supports the identification of arsenic, chloroform, and dieldrin

as the carcinogenic COCs of greatest concern.

4.1.1.5 Zone-svecific Risks

In this subsection, the contribution of the most important exposure pathways to carcinogenic

risk by COC is described for each zone. Several exposure pathways contribute to total carcinogenic risk, depending on chemical and zone. The hypothetical future carcinogenic risk in each

zone is attributable to the following pathways: ingestion of shallow groundwater (47 percent),

consumption of homegrown vegetables (average contribution to total carcinogenic risk -

26 percent), ingestion of locally produced milk (9 percent), consumption of locally produced eggs

(6 percent), inhalation of volatiles via domestic use of groundwater (7 percent), and consumption

of locally produced meat (3 percent). Dermal exposure does not contribute significantly to

carcinogenic risk, nor does incidental ingestion of soil and sediment. The oral route accounts for

20000,317.10(3) - OEA

0306111892 111 - 4-6
more than 90 percent of total hypothetical future carcinogenic risk, with the remainder predomi7

nantly by inhalation. As indicated previously, risks presented in this section may be overstated by

a factor of 3 as indicated by the uncertainty analysis.

Zon e IA. north of O'Brian Canal, is an area of relatively low groundwater and soil contamination (Figure 2.4.1-2). Atrazine and arsenic in groundwater and dieldrin in soil are the largest

contributors to hypothetical future carcinogenic risk in zone IA. Dieldrin hypothetical future

risks result from several exposure pathways because aldrin and dieldrin are bioaccumulated

effectively by root vegetables, milk, meat, and eggs. The method for estimating exposure

concentrations in foods assumes that agricultural products can bioaccumulate chemicals from soil

and surface water and that aldrin is converted to dieldrin upon uptake. Groundwater and surface

water in zone I A do not contain large concentrations of dieldrin, thus, the dieldrin residues

estimated in foods are attributable predominantly to uptake from soil.

An alternative way of characterizing the sources of the estimated risk is to disaggregate risk

associated with the abiotic media (groundwater, surface water, and soil) from which each of the

agricultural products may accumulate chemicals (Section 2.4.2). In zone IA, surface water is

uncontaminated, groundwater contributes approximately 60 percent of total potential risk, and soil

contributes approximately 40 percent.

Zone I B, south of O'Brian Canal, between the northwest boundary plume and the First

Creek paleochannel (Figure 2.4.1-2), is an area of relatively low groundwater and soil contamination. No permanent surface-water features are in zone I B, and agricultural water supply is

assumed to be exclusively by alluvial groundwater. Otherwise, exposure conditions are identical

in zones I A and I B. Results in these two zones differ (Figures 4.1.1-4 and 4.1.1-5) because

agricultural water supplies were assumed to have higher concentrations of COCs because they are

not diluted by uncontaminated surface water. As a result, future hypothetical risks are slightly

higher in zone I B.

Zone IC is identical to IA except that irrigation water is drawn from O'Brian Canal and the

Burlington Ditch upstream of the outfall of First Creek and is not affected by RMA

20000,317.10(3) - OEA

0306111892 111 - 4-7
(Figure 2.4.1-2). In fact, no carcinogenic COCs were detected at elevated concentrations in the

canals downstream of First Creek, resulting in identical results for carcinogenic risks in zones ]A

and IC (compare Figures 4.1.1-4 and 4.1.1-6).

As described in Section 4.1.1.1, background concentrations of arsenic in groundwater and

dieldrin in surf icial soil may contribute as much as 8 x 10-5 carcinogenic risk to the totals shown

in Table 4. 1. 1 - 1. The contribution of background risk to Zones I A, IB, IC, 2, 5, and 6 should be

considered when evaluating total risks in the Offpost OU.

Zone 2 is located directly north of the RMA northern boundary (northern paleochannel,

Figure 2.4.1-2) and south of O'Brian Canal. No permanent surface-water features are in zone 2,

an area with relatively high concentrations of COCs in groundwater but relatively low

concentrations in surf icial soil. Approximately 30 percent of the hypothetical future carcinogenic

risk, In zone 2 is attributable to the domestic use of groundwater containing chloroform and

(Figure 4.1.1-7). Consistent with EPA guidance, inhalation intakes of volatile chemicals such as

chloroform were assumed to equal intakes from ingestion of groundwater. Chloroform has a

much higher slope factor by the inhalation route than the ingestion route, so hypothetical future

risks by the groundwater inhalation pathway were estimated to be much greater than the

groundwater ingestion pathway. More than 80 percent of the hypothetical future carcinogenic

risk estimated for zone 2 'Is ultimatelv attributable to the use of groundwater. The inhalation

route of exposure contributes approximately 30 percent of total hypothetical future carcinogenic

risk in zone 71 (the highest relative contribution of the inhalation route for any zone, related to the

dominance of volatile COCs in zone 2 groundwater).

Zone 3 is the area within approximately 0.5 mile of the intersection of Peoria Street and

96th Avenue (Figure 2.4.1-2). First Creek traverses zone 3, which is an area with relatively high

concentrations of COCs in surficial soil, groundwater, and surface water. No human receptors

currenfly reside in zone 3. Figure 4.1.1-8 presents RME estimates of hypothetical future risk

under the hypothetical urban residential land use scenario for zone 3. Hypothetical future

carcinogenic risk would be dominated by exposure to dieldrin by vegetable and groundwater

20000,317.10(3) - OEA

0306111892 111 - 4-8
ingestion pathways. The oral route would account for approximately 97 percent of the total risk.

Total hypothetical future carcinogenic risk for zone 3 under the hypothetical urban residential

scenario would be attributable primarily to chemical concentrations in shallow groundwater

(60 percent), with significant contributions from surface water (150 percent) and soil (30 percent).

Arsenic and dieidrin are the predominant contributors to hypothetical future carcinogenic

risk in zone 4 (Figure 4.1.1-9). Zone 4 (First Creek paleochannel) is northwest of zone 3 and

traversed by First Creek (Figure 2.4.1-2) and is an area of relatively high surface-water and

groundwater contamination and relatively low surficial soil contamination. No human receptors

reside in zone 4 at this time. COCs in groundwater ultimately are the source of approximately

80 percent of the total hypothetical future carcinogenic risk. Surface water contributes approximately 10 percent of total risk, and 10 percent of the hypothetical future carcinogenic risk is

ultimate]\ attributable to OCPs in surficial soil.

As shown in Figure 4. 1. 1 -10, dieldrin and arsenic have the greatest contribution to total

hypothetical future carcinogenic risk in zone 5, an area downgradient of the NWBCS and south of

the canals (Figure 2.4.1-2). No surface-water features are in zone 5, soil concentrations are

relatively low, and groundwater concentrations are moderate. Groundwater ingestion is the most

important pathway, accounting for 89 percent of hypothetical risk. In zone 5, 99 percent of the

hypothetical future RME risk is attributable to groundwater and less than I percent to soil

concentrations.

Zone 6 is the extension of the northwest boundary plume north of the canals

(Figure 2.4.1-2). Hypothetical future carcinogenic risks are predominantly attributable to dieldrin

(Figure 4. 1.1 -1 1). Soil and groundwater each contribute approximately 50 percent of the

hypothetical future risk.

A summary of the contributions to hypothetical future carcinogenic risk by chemical,

exposure pathwaý, exposure route, and source media follows:

1. The contribution of dieldrin to total carcinogenic risk is greater than that of any other

chemical in zones 1, 3, and 6. Chloroform poses the greatest risk in zone 2 and arsenic in

zone 4.

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2. Groundwater ingestion is the exposure pathway with the greatest contribution to total risk

in all zones except zone 3. Ingestion of homegrown vegetables is the largest pathway in

zone 3. Domestic use of groundwater (ingestion and inhalation) accounts for

approximately 50 percent of hypothetical future carcinogenic risk outside zone 2 and

67 percent in zone 2.

3. Consumption of vegetables produced in the Offpost OU is also an important pathway

contributing approximately 25 percent of the hypothetical future risk.

4. The oral exposure route contributes more than 90 percent of the total risk in each

zone except zone 2, where inhalation contributes approximately 30 percent of total risk.

5. Background concentrations of dieldrin in soil attributable to agricultural practices appear

to contribute 20 to 50 percent of the total hypothetical future carcinogenic risk in zones

1A, 113, W, 2, and 6. Groundwater is the dominant source medium contributing to total

hypothetical future carcinogenic risk. Naturally occurring arsenic in groundwater

contributes a risk of approximately 4 x 10-5. Surface water contributes less than

15 percent of total risk in zones 3 and 4.

4.1.1.6 Acute/Subchronic Effects

H\,pothetical future acute effects were evaluated by comparison of acute intake estimates

with Minimal Risk Levels (MRLs) developed by the ATSDR and summarized by EPA (1991b).

Reference doses were also estimated from EPA's short-term health advisories (HAs) (shorter than

14 days). Acute intakes were estimated for two potentially sensitive subpopulations: women of

childbearing age and children. MRLs were not exceeded for any chemical in any zone. Dieldrin

is the only chemical estimated hypothetically to exceed HAs. EPA's one-day HA for dieldrin is

exceeded hypothetically in zones 2, 3, and 4. An acute HI has been estimated by dividing acute

intakes by acute reference doses. Results from children are illustrated in Figure 4.1.1-12

indicating that dieldrin is the predominant contributor to acute His and that the HI exceeds I in

zones 2, 3. and 4, with a maximum acute HI of 4 in zone 3. Table 4.1.1-3 presents these results

numerically. Adult female acute His are consistently about 60 percent less than children and less

than I in all zones except 3. These results indicate that the potential for adverse health effects

exists as the result of hypothetical future short-term exposure to dieldrin at the RME acute intake

level in zones 2, 3, and 4.

Available data sources used to define exposure factors (Section 2.4.3.2) do not readily

support the estimation of exposure factors averaged over subchronic exposure durations. Acute

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and chronic intakes have been estimated. RME intakes over subchronic exposure durations are

expected to be less than RME acute intakes and greater than or approximately equal to RME

chronic intakes. Exposure assumptions adopted in the residential scenario assume continuous

residency over periods encompassing a chronic exposure, and the most important exposure

pathways are not expected to result in extreme seasonal variability in exposure. Vegetable

consumption may vary seasonally with the availability of homegrown produce. Thus, although the

RME subchronic intake is clearly less than the RME acute intake and greater than the RME

chronic intake, it is probably in the low end of that range (i.e., slightly greater than the RME

chronic intake).

The method used to estimate subchronic His is as follows: for the lower range, the RME

chronic intake was divided bv the subchronic reference dose; for the upper range, the RME acute

intake was divided by the subchronic reference dose. Tables 4.1.1-4 and 4.1.1-5 summarize the

zone/chemical combinations that have the potential for adverse effects as a result of exposures

over subchronic duration for children and adult females, respectively (all chemicals whose RME

acute intake exceeds the subchronic reference dose). Figure 4.1.1-13 illustrates the range of

hepatic His for children by zone.

Dieldrin and manganese are the only chemicals with the potential for noncarcinogenic

effects as a result of exposure of subehronic duration. When the upper end of the range reported

exceeds 1, the potential for adverse effects exists; also, if the lower end of the range is greater

than 1. the RME chronic intake exceeds the subehronic reference dose.

Subchronic reference doses have not been published by EPA for all offpost COCs. For those

COCs, RME acute intakes were compared to chronic reference doses and subchronic MRI-s

(developed by ATSDR and summarized by EPA, 1991b). This final comparison revealed that no

chemicals without subchronic reference doses have significant hypothetical future potential for

adverse effects as the result of exposures over subchronic durations (i.e., RME acute intakes

exceeded neither chronic reference doses nor subchronic MRI-s for chemicals without subchronic

reference doses).

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4.1.2 HvDothetic Current Risks Versus Hypothetical Future Risks

As used in this subsection, the term "hypothetical" refers to the application of risk

assessment methodologies that extrapolate from high doses to low doses and from laboratory

animals to humans.

No residents are in zones 3 or 4 at this time; hence, exposure pathways are not complete, and

there are no hypothetical current health risks in these zones for the residential scenario. Residents

in zones I B and 2 do not use the alluvial aquifer for domestic use; hence, these pathways are not

complete. Based on the consumptive use surveys, alluvial groundwater may still be used as an

agricultural water supply in zones I B and 2, and RME intake levels associated with agriculture

would result in hypothetical risks of less than 8 x 10-5. These risks were determined by subtracting the hypothetical risks associated with the groundwater oral and inhalation exposure pathways

(Volume IV, Appendix G). Background risks due to zone 1, 2, and 6 contaminants in soil alone,

regardless of the source or use of water, are approximately 4 x 10-5 for residents who consume

agricultural products produced in the Offpost OU at RME intake levels. All cited risks may be

overstated bv a factor of 3 as indicated by the uncertainty analysis.

By a similar process of eliminating currently incomplete pathways, the maximum hazard

index under existing exposures is less than I in all zones.

4.1.3 Health Risk at Most Likelv Ext)osure Intakes

The principal focus of the human risk characterization was to estimate health risks at RME

intake levels. An uncertainty analysis was performed to characterize the distribution of chemical

intakes among the potentially exposed population, the uncertainty associated with intake

estimates. and the degree of conservatism incorporated in the RME risk estimate. To provide

additional perspective on this topic, the MLE intakes as well as chronic HIs and cancer risks at the

MLE intakes have been estimated. In calculating MLE risks, the same conservative RFDs and SFs

used in the RME risk calculations were used, so the appropriate interpretation of the MLE risk

estimates would be that they are conservative estimates of risk for individuals experiencing MLE

intakes.

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MLE intakes were estimated for all COCs and completed pathways for the hypothetical

future exposure scenario. The chronic MLE intakes were estimated using the same equations used

for tile RME intakes. The input parameters selected for this analysis, however, were mean or

median values. Mean values were used for exposure concentrations and parameters used to

estimate exposure concentrations in food. Median values were used for exposure factors such as

ingestion rates and exposure frequency and duration. As a result, the MLE intakes represent the

best estimate of the median intake for the potentially exposed population. Because the toxicity

factors were the same in both the MLE and RME analyses, the ratio of RME intakes to MLE

intakes is the same as the ratio of RME risks to MLE risks. Table 4.1.1-6 summarizes the additive

hypothetical carcinogenic risks at the MLE intake levels and compares these estimates to the RME

risks. At MLE intake levels, hypothetical carcinogenic risks would not exceed 3 x 10-5 (zone 4).

Risks at RME intake levels typically exceed MLE risks by a factor of 10. It is estimated that

approximately half of a potentially exposed rural residential population would experience intakes

less than the MLE and half would experience higher intakes. Less than 2 percent of the

population would experience intakes as high as the RME (see Section 2.4.5).

With respect to potential noncarcinogenic effects, child-chronic His for hepatic effects at

MLE intakes do not exceed I in any zone. Hepatic His at MLE intake levels are approximately

one-third of the RME His. At MLE intake levels, the CNS HI was estimated to be 4 in zone 4.

This result is affected by the unique features of the distribution of observed concentrations of

DIMP in groundwater (see Section 2.4.5.5.2). Selection of the sample mean as the best estimate of

the population mean, instead of the lognormal estimator (Gilbert, 1987) would have resulted in an

MLE central nervous system HI <1 for zone 4.

An important implication of the MLE analysis, which is also supported by the uncertainty

analysis, is that risks presented at RME intake levels are not representative of the risks faced by

the majority of the hypothetically exposed population. Although a few individuals might be

exposed at RME levels, the MLE intakes are more representative of the typical exposure levels.

The RME exposure rates and corresponding risks overstate the carcinogenic risk to the typical

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resident by factors ranging from 8 to 12 times. Similarly, the typical child's noncarcinogenic

hepatic HI would be three times less than RME HIs reported (MLE hepatic HI :51).

4.1.4 Alternative Risk Estimate Based on Predicted Decline in Groundwater Concentrations

As presented in Section 2.4.2.2, groundwater concentrations are declining in zones 3 and 4,

and may be expected to decline further over chronic 9- and 30-year average concentrations for

aldrin and dieldrin. All other organic contaminants may be expected to decline at least as fast as

these relative]y immobile groundwater COCs. Over the 9-year exposure duration used for the

noncarcinogenic assessment. concentrations were predicted to decline to 42 to 48 percent less than

the RME concentrations based on 1989 to 1991 monitoring data. Over the 30-year exposure

duration, average concentrations were predicted to decline by 48 to 74 percent.

The effect of using these predicted aldrin and dieldrin concentrations while holding other

COC concentrations constant is not substantial. Cancer risk in zone 3 would be reduced from

3 x 10-4 to 2 x 10-4 , and the child chronic hepatic hazard index would remain at 2. In zone 4 the

carcinogenic risk is unaffected when rounded off to one significant figure at 2 x 1 0-4 , and the

child chronic hepatic hazard index would decline from 1.4 to 1.2. If, on the other hand, one

assumes that all organic groundwater COCs would be reduced by similar percentages, the effect

would be more significant. Carcinogenic risk would decline from 3 x 10-4 to 2 x 1 0-4 in zone 3

and from 2 x 10-4 to I X 10-4 in zone 4. The child chronic hepatic hazard index would decline

from 2 to 1.4 in zone 3, and from 1.4 to 0.7 in zone 4. As noted in Section 2.4.2.2, these are

conservative assumptions used in the aldrin/dieldrin decline prediction. Actual declines may be

greater.

4.2 COMMERCIALANDUSTRIAL SCENARIO

The C11 scenario differs from the rural residential scenario in that no agricultural pathways

are present (e.g., dairy, meat, vegetables). For this scenario, exposure pathways relating to

groundwater and soil were evaluated. RME-estimated intake scenarios for carcinogenic risks and

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noncarcinogenic His were quantified for zone 5 because of the likelihood of future land uses in

this zone (Section 2.2.2.2).

The exposure pathways that were evaluated for the adult C/I worker included ingestion of

groundwater and inhalation of volatiles from groundwater (including showering) and dermal

exposure to and ingestion of soil. The sediment and surface-water exposure pathways were not

evaluated because the ingestion and dermal exposure routes were not expected to occur in zone 5.

4.2.1 Adult Chronic Hypothetical Future Hazard Indices

The additive hypothetical future HI for liver toxicants was <0.1 in zone 5 (Figure 4.2.1-1).

The OCPs account for the highest His through the soil and groundwater pathways via the

ingestion route of exposure. Because the chronic liver His were less than 1, acute HIs are not

presented.

4.2.2 Hvt)o hetical Future Carcinopenic Risks

The hypothetical future carcinogenic risks for the CII scenario range from 1.8 x 10-9 to

1.6 x 10-5 in zone 5. Arsenic is the major contributor to the hypothetical future carcinogenic risks

in zone 5. Arsenic accounts for approximately 60 percent of the estimated risk in zone 5.

Exposure to arsenic by the ingestion of groundwater is the single largest pathway component to

the overall hypothetical future risk.

4.2.3 Carcinopenic Risk at Most Likelv Exposure Intakes

For the CII scenario, MLE His are approximately 67 percent less than the RME His. The

MLE liver H1 is 0.07 for zone 5. The MLE hypothetical future carcinogenic risks are

approximately 30 percent less than the RME risks, with risks of 7 x 1 0-6 zone 5.

4.3 RISK CHARACTERIZATION SUMMARY

Additive carcinogenic risks for potential future residential exposures at RME intake levels

by zone are summarized in Table 4. 1. 1 - 1, which shows that cancer risk is highest in zones 2, 3,

and 4. These zones are south of O'Brian Canal and within approximately I mile of the north

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RMA boundary. Hypothetical future cancer risks in each of these zones are estimated to be less

than 3 x 10-4 . These risks may be overstated by a factor of 3 as indicated by the uncertainty

analvsis. More than 60 percent of the risk Jn each of these zones is attributable to category B2 and

C carcinogens. Thus, the carcinogenic risk estimate is critically dependent on the extrapolation of

toxicological data from animal to human. Discussions on the potential carcinogenicity of each

COC are in the toxicological profiles, including Shell Oil Company's toxicological profile for

aldrin and dieldrin, located in Appendix F of the EA. Dieldrin is the dominant contributor to

total cancer risk in zones 3 and 6 and is significant in all other zones with an average contribution

of approximately 50 percent. Chloroform contributes 30 percent in zone 2 and arsenic 30 percent

in zone 4.

Several exposure pathways contribute to total hypothetical carcinogenic risk, depending on

chemical and zone. More than 95 percent of the carcinogenic risk in each zone, however, is

attributable to the following pathways. listed in order of their contribution to risk (highest to

lowest):

I . Ingestion of shallow groundwater

2. Consumption of homegrown vegetables

3. Ingestion of locally produced milk

4. Inhalation of volatiles via domestic use of shallow groundwater

5. Ingestion of locally produced eggs

6. Ingestion of locally produced meat

Dermal exposures do not contribute significantly to carcinogenic risk, nor does incidental

ingestion of soil and sediment. The oral exposure route accounts for more than 90 percent of total

carcinogenic risk, with the remainder predominantly by inhalation.

Shallow groundwater is the dominant source medium contributing to total hypothetical

carcinogenic risk in all zones accounting for 45 to 80 percent of total risk, depending on the zone.

Soil contributes 20 to 60 percent of the risk in zones I A, I B, I C and 6. Groundwater, surface

water. and soil contribute to estimated risks via multiple pathways, specifically those involving

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M

local food production. Groundwater and surface water were assumed to be used for irrigating

vegetable crops and watering livestock. Each of the food pathways may also accumulate COCs

from soil, and these relationships are quantified via the equilibrium partition models presented in

Section 2.4.2.

Hypothetical risks from all carcinogens were added to determine total carcinogenic risk,

regardless of target organ/system or weight-of -evidence category. The dominant contribution to

total carcinogenic risk in all zones is from category B2 and C carcinogens, as previously described.

Hypothetical future noncarcinogenic effects were evaluated for all COCs. Children are a

potentially sensitive subpopulation with the largest potential for adverse noncarcinogenic effects

due to higher chemical intakes (mg/kg/day). Considering the target organ/system potentially

affected bv each of the COCs, the most probable nonearcinogenic effect would be on the CNS as a

result of hypothetical future exposure to DIMP in zone 4, where the HI is 4. The hypothetical

additive child chronic HI for liver toxicants has a maximum of 2 in zone 3.

The probability of adverse effects to women and fetuses is less than the risk, to children

because the adult female intake is less than the child intake based on intake rates and body weight.

None of the chemicals with Hls approximately equal to or greater than I (indicating potential for

adverse noricarcinogenic effects) demonstrate developmental toxicity effects at doses lower than

those that adversely affect the mother. Consequently, the chronic and subchronic RfDs are

protective for developmental effects.

RMEs of existing exposures and resultant health risks are substantially less than hypothetical

future exposures. No human receptors reside in zones 3 and 4 at this time; hence, there is no

current risk in these zones. Residences with RME concentrations in shallow groundwater wells in

zones I B. 2, 3, and 4 (before relocation) use water supplies other than shallow groundwater.

Consequently, groundwater pathways are not complete in these zones. Residential risks due to

existing exposure to soil, regardless of water use, range from as little as I x 10-5 (zone 4), to as

much as 8 x 10-5 (in zone 3) for residents who might consume foodstuffs produced in the

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Offpost OU at RME intake levels. However, the 4 x 10-5 risk associated with soil in zones other

than zone 3 and 4 may not be attributable to RMA sources but to agricultural practices.

MLE His and carcinogenic risks were estimated for the residential scenario. The

carcinogenic risks were from 8 to 12 times less than corresponding RME risks, depending on the

zone.

Hypothetical future carcinogenic risks and noncarcinogenic His were estimated for RME

intake levels for the C11 scenario. Dieldrin, aldrin, and arsenic account for the largest portion of

risk. approximately 80,percent, through the groundwater ingestion exposure pathway. The

chronic His for liver toxicants were all <0.1 for zone 5; the OCPs (chlordane, dieldrin, and aldrin)

are the major HI chemical contributors through the groundwater ingestion pathway.

MLE His and carcinogenic risks for the C11 scenario are approximately 67 and 33 percent

of the RME risks, respectively.

4.4 UNCERTAINTIES IN THE HUMAN HEALTH ASSESSMENT

Uncertainties in the risk characterization represent the combined uncertainties of the

exposure and toxicity assessments. Overall, these uncertainties were resolved by conservative

assumptions. Consideration of the risk characterization results permits identification of the most

important contributors to overall uncertainty.

1. Identification of COCs

Potential uncertainties in identification of COCs have a minor or insignificant effect on

RME risk estimates. COCs contributing significantly to risk are clearly attributable to

migration from RMA, and it is extremely unlikely that excluded chemicals could

contribute significantly to the total RME risk.

2. Chemical Fate

The quantitative uncertainty analysis documents that identified uncertainties in

equilibrium partition coefficients used to estimate exposure concentration in foods do

not contribute significantly to uncertainty in RME risk estimates. Bioaccumulation of

pesticides in agricultural products was estimated from experiments using freshly applied

chemicals. Site conditions differ; pesticides have aged in soil for many years. This

ýource of uncertainty cannot be evaluated because of lack of pertinent research

information. Numerous COCs have been shown to biodegrade over time in soil, surface

water, sediment, and groundwater. Biodegradation processes were not quantified due to

lack of pertinent site-specific information. This limitation of the assessment may cause

chronic and lifetime risks to be overestimated.

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3. Exposure pathways

Exposure pathways contributing most of the residential RME risk in zones 2, 3, and 4.

are not complete at this time. In zone 2, alluvial groundwater is not used for domestic

supply, but this pathway contributes 74 percent of RME total carcinogenic risk and

56 percent of the child chronic hepatic HI. Pathways excluded from the quantification,

through potentially complete, have the potential to add less than 15 percent to total

carcinogenic risk.

4. Intake Estimation

Chemical concentrations are expected to decline over time. Intake estimates are based

on monitoring data from 1989 to 1991 and may overestimate current and future

exposure concentrations. Exposure and risks may be greater than zonewide average risk

estimates in localized (e.g., one to five acres) hot spots (up to twice as high in identified

hot spots in zones 2 and 3). On the other hand, the risk throughout most of each zone is

probably lower than the zonewide RME.

RME exposure concentrations calculated from monitoring data may differ from actual

exposure concentrations due solely to the selection of the statisticaf calculation procedure. The effect of these differences on carcinogenic risk estimates in any zone is

estimated to be less than 40 percent. However, the CNS hazard index in zone 4 may be

overstated bv a factor of 5 for this reason.

The results of the quantitative uncertainty analysis indicate that RME intakes achieve

the goal of the RME in estimating an exposure in the upper range of those possible. In

fact, RME estimates could significantly exceed the 95th percentile exposure, the lower

boundary suggested by EPA for an upper range exposure estimate. The RME intakes

consistently fall at or above the 98th percentile of the distribution of intakes and

typically exceed the 95th percentile by a factor of 3. Most people in the Offpost OU

will experience intakes substantially less than the RME.

5. Toxicity Assessment

Reference doses typical]\, are set 100 to 1000 times lower than the lowest doses found to

produce an adverse effect in animal studies. These uncertainty factors are reflective of

the uncertainties in risk caused by uncertainties in the toxicity assessment. These

uncertainties are resolved conservatively by the EPA-recommended procedures adopted

in the assessment.

An overwhelming portion (59 to 100 percent, depending on zone) of total carcinogenic

risk estimated for humans is attributable to category B2 and C carcinogens. There is

insufficient evidence that these chemicals cause cancer in humans. Thus, it is possible

that these chemicals are not carcinogenic to humans.

In summary, the RME risk estimates presented here are sufficiently conservative for use in

risk management decisions for the offpost operable unit.

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5.0 ECOLOGICAL ASSESSMENT

The objective of the Offpost OU ecological risk assessment was to evaluate potential adverse

effects to the environment and nonhuman receptors as a result of potential exposure to chemicals

migrating from onpost sources. This section of the EA reviews the site characterization with

emphasis on ecological receptors. An ecological exposure assessment is provided that describes

two ecological assessment endpoints: (I ) residue concentration in tissue that could adversely affect

function or health and (2) contaminant concentrations in abiotic media at levels that could have an

impact on ecological receptors through direct toxicity. Procedures for evaluating each are

described. The final section characterizes the risk to ecosystems, with particular reference to

zones 3 and 4 in the Offpost OU.

Although the EPA has recently published several documents on ecological risk assessment

(EPA, 1992a, 1992b, 1992c), guidance similar to that for human health risk assessments (EPA,

1989a) Is not available. Therefore, the procedures the Army used to evaluate the potential effects

of offpost chemicals of concern in ecological receptors for this ecological assessment have been

developed from several sources, including the open literature, EPA documents, and professional

judgement. Because of the evolving nature of ecological risk assessment methodology, the

assumptions and approaches adopted for the Offpost OU Ecological Assessment may not be

applicable for use at sites or locations outside the Offpost OU boundaries. Also, the acceptance of

the Offpost OU procedures and values as they appear in this document does not imply that the

Offpost procedures and values set precedent for use at other sites and locations.

5.1 SITE CHARACTERIZATION

5.1.1 Studv Area Definition

The offpost area is defined as the triangular region north of RMA that is bounded by the

South Platte River on the west and Second Creek on the east, including the waters of Barr Lake

(Figure 2.4.1-2). Sampling areas for biota in the off post area are in Figure 5. 1.1 -1 (HLA, 1992).

Two major natural ecosystems occur in the Offpost OU: terrestrial and aquatic. The area is also

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extensively used for agricultural purposes. Regional topography is represented by stream-valley

lowlands and gently rolling uplands. A result of the topographic relief is apparent in well-defined

surface-water drainage areas, wetland features, and large expanses of temperate grasslands. The

Offpost OU supports many of the same wildlife species found on RMA; however, because biotic

resources differ and because of the occurrence of intense agricultural land management practices

in the Offpost OU, biota samples were primarily restricted to zones 3 and 4. The major ecological

habitats are presented in Figure 5.1.1-2 (HLA, 1992).

5.1.1.1 Terrestrial Systems

A detailed analysis of aerial photography of the Offpost OU was conducted to identify site

usage patterns and to delineate accurate boundaries of land use from aerial photographs taken in

1950, 1969, and 1983 (Bionetics Corporation, 1984). Since 1950, the majority of the Offpost OU

has been dominated by agricultural lands, primarily supporting grain crops and pasture, with some

fallow or idle fields.

During 1990, a visual characterization of the Offpost OU was conducted by ESE. The

primary field crops grown in the Offpost OU include Winter wheat, hay, barley, corn for grain,

corn for silage, sugar beets, and oats. Other crops in this area include a variety of vegetables,

sorghum, dry beans, and Spring wheat. Of the field crops listed, Winter and Spring wheat, barley,

sugar beets, and dry beans are produced for human consumption, and corn, hay crops, sorghum,

and oats are produced for animal feed.

In general, areas of the Offpost OU located north of O'Brian Canal are irrigated, whereas

areas south of the canal rely on dryland farming. Pasture is a significant resource within the

Offpost OU but accounts for much less acreage than croplands. Intense grazing was observed

along the First Creek corridor and in the First Creek Impoundment vicinity (HLA, 1992). Other

land uses include confined livestock feeding operations, residential, industrial, transportation, and

mineral extraction.

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5.1.1.2 Aauatic Systems

Because of the degree of natural surface-water drainage and water resource management

(waterways, lakes, ponds, reservoirs), limited, but important, wetland resources occur in the

Offpost OU. Aquatic systems include Barr Lake, O'Brian Canal, Burlington Ditch, South Platte

River, First Creek, Second Creek, and several ponds and reservoirs, as shown in Figure 1.2-5.

First Creek Impoundment and First Creek were studied during the Offpost RI for habitat

characterization, contamination, and species occurrence because these aquatic ecosystems contain

the highest concentration and/or frequency of detection of chemical residues attributed to COCs

originating from RMA sources. In addition to First Creek and First Creek Impoundment,

surface-water and sediment samples were also collected from O'Brian Canal, Burlington Ditch,

and Barr Lake (HLA, 1992).

As intermittent streams, First Creek and Second Creek do not support economically or

environmentally important fish populations. O'Brian Canal is a manmade channel principally used

for irrigation that can be expected to support fish species characteristic of the South Platte River.

Fathead minnows, white suckers, and green sunfish are the most frequently observed species in

these water bodies (Environmental Research and Technology [ERT], 1985).

Barr Lake is the largest lentic aquatic habitat of the Offpost OU. The Colorado Division of

Wildlife stocks Barr Lake with channel catfish, smallmouth and largemouth bass, Sacramento and

yellow perch, rainbow trout, crappie, and bluegill. Barr Lake provides important nesting and

foraging habitat for a variety of birds, including white pelicans, great blue herons, cormorants,

mallard ducks, grebes, gulls, and bald eagles. In addition to hosting a large heron rookery, Barr

Lake has been the site where a pair of bald eagles has nested since 1986. Recreational fishing and

waterfowl hunting are permitted at Barr Lake State Park. Angler effort and fish catch statistics

for Barr Lake indicate that in 1980, 5000 fish were harvested, including carp, bass, and catfish,

representing 24,000 angler hours. Barr Lake has received industrial and sewage effluent and

runoff from urban and agricultural land since the lake was constructed more than 80 years ago

(DRCOG, 1989).

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5.1.2 Ecological Characterization of the Offoost Onerable Unit

Habitat mapping of the First Creek portion of the Offpost OU (HLA, 1992) identified

intensive human land use, including dryland farming, cattle grazing, private dumps, and

residences (Figure 5.1.1-2). Small vacant lots, fallow fields, wetlands along First Creek, and

prairie dog colonies comprise the balance of habitat types in the immediate offpost study area.

Undisturbed habitats were not identified in the Offpost OU. Wildlife species found in habitats in

the offpost area (Table 5.1.2- 1) were also common on RMA. However, wildlife species diversity

in the Offpost OU is limited by the lack of variety in habitats and degree of human disturbance.

There are no federally designated critical habitats in or near the Offpost OU (USFWS, 1990).

The weedy forbs (WF) and grasses and weedy forbs (GWF) habitats were described in the

Biota RI (ESE, 1989b). The predominant species in the WF habitat type include summer cypress

(Kochia iranica), prickly lettuce (Lactuca serriola), thistle (Cirsium arvensis and Carduus nulans),

Russian thistle (Salsola iberica), field bindweed (Convolvulus arvense), various sunflowers

(Helianthus spp.), and tumble mustard (Sisymbrium allissimum). The GWF habitat type is similar

to the WF habitat type but with an increased abundance of cheatgrass (Bromus lectorum), western

wheatgrass (Agropyron smiihii), and bluegrass (Poa spp.) in addition to the forb species. WF and

GWF habitat types support cattle and horse grazing in the offpost area, particularly along the

channelized portion of First Creek below the First Creek Impoundment.

The offpost prairie dog (PD) colony habitat resembled the onpost RMA prairie dog habitat,

with slightly less vegetative cover (field bindweed and bunchgrasses). The horse and cattle range

appeared overgrazed, with only a few interspersed forbs and grasses (HLA, 1992). Plowed and

unplowed fallow fields (PFF and FF) were lightly vegetated with remnant crops and grasses. The

unplowed corners of the fallow fields were covered with WF-type vegetation, including the

common Russian thistle. Shelter belt cottonwood trees and ornamental plants surround the

residences and buildings in the mapped area, as shown in Figure 5.1.1-2.

Approximately 250 acres of wetlands occur along First Creek from the northern RMA

boundary (North Bog) to the First Creek Impoundment. These wetlands have been delineated by

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the U.S. Fish and Wildlife Service (Feasibility Study, Appendix B). These tall grass wetlands

(TG-W) contain quackgrass (Agropyron repens), intermediate wheatgrass (Agropyron intermediatuni), and cheatgrass. Many forbs found in the WF and GWF habitat types were also found

in or adjacent to the wetlands. Cattail (Ti,pha angustifolia) marshes (CTM) and areas dominated

by sedges (Carex spp.) and rushes (Scirpus spp.) are interspersed in the First Creek drainage.

Below the First Creek Impoundment, the wetland vegetation was limited to the banks of the river

course, which has been channelized and grazed back to a GWF habitat type. No immersed

wetlands occur below the First Creek Impoundment until the creek empties into O'Brian Canal.

The wetlands habitat, along with WF and GWF habitat, support most of the wildlife species

observed in the offpost area.

5.1.3 Contamination Pertaininp, to Offr)ost Biota

Data from the chemical analyses of cow milk and body fat, chicken tissues and a composite

egg sample, and aquatic and terrestrial wildlife species are presented in the RI Addendum (HLA,

1992). Volume 11, Section 1.0 of this EA summarizes the contamination in the various media.

Biota sampling locations are shown in Figure 5.1.1-1. Although dieldrin was the contaminant most often detected among offpost biota (bovine fat, chicken tissues [fat and skin, liver, and

eggs], fish, earthworms, deer mice, prairie dogs, and pheasant liver samples), the concentrations

detected were low and/or infrequent (HLA, 1992). Arsenic concentrations were detected in algal

mats and a composite sample of crayfish from the First Creek Impoundment, earthworms, and one

of four prairie dog samples (HLA, 1992). Mercury was detected in fathead minnows and carp

collected from the First Creek Impoundment and in three of five earthworm samples. The

mercury levels were determined to be within the expected range for background, as determined

by data from McKay Lake in western Adams County and reported in the Biota RI (ESE, 1989b).

DDE was detected in the fat and skin portion of a chicken collected from a farm north of RMA

(site HA 104213P). Aldrin and DDT were not detected in any biological sample collected in the

Offpost OU.

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The impact of groundwater on offpost ecological receptors was limited to areas where

livestock and crops may be exposed to contaminated groundwater via agricultural wells. Exposure

to these receptors may occur if contaminated wells are still in use; therefore, chemical concentrations in groundwater were evaluated for potential toxicity to agricultural receptors.

5.1.4 Selection of Chemicals of Concern for Biota

COCs for the ecological assessment were selected in a manner consistent with the approach

used in the human health risk assessment (Section 1.0). COCs were considered to be those

chemicals in abiotic media with concentrations significantly elevated with respect to background.

In addition, for the ecological assessment, the selection of COCs was refined further by

considering appropriate exposure media by food web (e.g., terrestrial or aquatic). For example,

target analytes elevated in groundwater would be considered as groundwater COCs, but only

livestock with access to agricultural wells would be exposed.

All biota could be exposed to COCs directly from abiotic media, and biota at higher trophic

levels could receive additional exposure via bioaccumulation in food chains. Potential COCs for

terrestrial and aquatic wildlife receptors were limited to site-related chemicals found in surface

soil, surface water, and sediment. Groundwater COCs were used in the evaluation of agricultural

receptors only. Tissue analytical data for ecological receptors were also evaluated with respect to

the COCs in ablotic media. COCs in tissue (TCOCs) were selected by evaluating the biota data for

the seven target analytes (aldrin, dieldrin, endrin, DDT, DDE, arsenic, and mercury) in tissue

from the Offpost RI Addendum (HLA, 1992). Six of these seven analytes in tissue (aldrin, dieldrin, endrin, DDT, DDE, and arsenic) were also COCs in abiotic media and are thus considered

TCOCs. Mercury was not elevated in offpost abiotic media (Volume 11, Section 1.0). In addition,

arsenic concentrations in earthworms from the Offpost OU were similar to the RMA onpost

control samples (ESE, 1989b). Because arsenic in soil is considered to be within the range of

background, arsenic was not evaluated further as a COC in a terrestrial ecosystems in the Offpost

Ou.

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TCOCs were evaluated using a food web approach (dietary ingestion); other COCs were

evaluated for direct toxicity (surface water, soil, and prey ingestion). The list of COCs to be

evaluated for the ecological assessment is presented in Table 5.1.4- 1.

5.2 EXPOSURE ASSESSMENT

This section describes the potential biological receptors and exposure pathways in the offpost

area. It also describes how exposure point concentrations were used in the exposure assessment.

Ecological assessment ýndpoints, residue concentrations, and associated procedures used to

quantify exposure for the endpoints are also described.

5.2.1 Potential Biolopical Receptors and Sensitive Subpopulations

EPA guidance indicates that biological receptors (ecosystem components expected to reflect

adverse effects of pollutant stress) be selected to represent an), potential adverse effects to all

ecosystem components (EPA, 1989f). Several site-related criteria were considered in screening for

potential biological receptors. Initial screening was performed to identify receptors as potentially

present and important in the Offpost OU. The numbers representing the following criteria

correspond to numbers on the matrix presented in Table 5.2.1 - 1.

I . Species observed or collected offpost during RI activities, which confirms their presence

offpost

2. Species presence at RMA, which implies their presence offpost

3. Species observed offpost or potentially within the study area, as noted by other studies

or agencies

4. Species presence confirmed and an important component of offpost food chains (this

may result in a source of exposure to higher trophic levels if species is an important

forage component; ecosystem stability may alter if population is adversely affected)

EPA guidance states that special consideration be given to rare, threatened, and endangered

species; birds listed in the Migratory Bird Treaty Act; and to species of commercial or sport value

(EPA, 1989f). Representative receptor species and sensitive subpopulations for the Offpost OU

were selected from the list of potential biological receptors using suggested EPA criteria and

additional information:

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5. Rare, threatened, or endangered species known to occur onpost and inferred also to

occur offpost, and birds protected under the Migratory Bird Treaty Act

6. Potentially affected commercial or sport species

7. Species of high public interest

8. Behavior, life history, or physiological aspects of organism that may increase exposure

or uptake or decrease threshold for toxic effects

9. Availability of ecotoxicity data for receptor species or related taxa

The representative biological receptors include major trophic levels (e.g., primary producer,

predators) of the offpo9t ecosystem. In most cases, one or two organisms were used to represent

adverse effects to other related taxa; for example, the bald eagle and great horned owl represent

other large raptors.

Focusing the ecological risk assessment on the selected receptors served two purposes. First,

the receptors were arranged into food webs to model bioaccumulation of contaminants. Food web

modeling was used to predict contaminant exposure to trophic levels for which samples were

unavailable from the RI (HLA, 1992). Second, selecting the most important and sensitive

organisms helped ensure that if these species are protected in the risk assessment, other less

sensitive or important organisms will be also protected.

5.2.1.1 Terrestrial Recewors

Wildlife species that can be considered potential receptors (Table 5.2.1 -1) include several

species that also occur on RMA as described in the Biota RI (ESE, 1989b), or which are listed as

being observed offpost in Table 5.1.2-1 (HLA, 1992). Receptors of concern include rodents,

especially mice (Peromyscus spp.) and prairie dogs (Cynomys ludovicianus), which fit site-related

criteria 1, 2, and 4. Additional small mammals that are inferred to occur in the Offpost OU, but

were not collected during the RI, include shrews, voles, and ground squirrels. Mice and prairie

dogs are both burrowing animals, and thus potentially contact contaminated soil during burrowing

activities, as well as during feeding and grooming. Mice have varied feeding habits that could

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increase the overall contaminant exposure rate as compared to prairie dogs, which are primarily

vegetarian.

Lagomorphs (rabbits) and deer also occur in the Offpost OU but were not collected for the

Offpost Rl. Neither species observed onpost contained elevated tissue residues on a regular basis

(ESE, 1989b); therefore, they were determined to be less highly exposed than some other species.

Skunks, raccoons, bobcats, fox, and coyotes are other mammals that were inferred to occur

or were observed in the offpost area (Table 5.1.2-1). However, because of inherent sampling

problems., these animals were not collected for sample analyses during the Offpost Rl.

Species selected as representative biological receptors are highlighted in bold type on

Tables 5.2'. 1 -1 and 5.2. 1 - 12. It was assumed that the selection criteria ensured that these species

would be representative of all ecological disturbance.

Avian species that are inferred to occur or were observed in the Offpost OU include a

variety of upland species. Pheasants (Phasianus colchicus) fit site-specific criteria 1, 2, and 4.

Bald eagles. golden eagles, hawks, falcons, and owls are inferred to occur or have been observed

in the Offpost OU (Table 5.1.2-1 ). Bald eagles have nested at nearby Barr Lake since 1986. In

addition, bald eagles fit the criterion for sensitive subpopulations because they are endangered and

are potentially more highly exposed because of their feeding behavior. In addition, other raptors

also fit the criteria of high public interest, migratory birds, and/or potential high exposure

because of their feeding behavior. Avian predators are also sensitive to the effects of organochlorine pesticides (ESE, 1989b) and are thus represented more heavily as receptors than other

predators. Raptors have large home ranges and may feed extensively outside the immediate First

Creek drainage (U.S. Fish and Wildlife Service [USFWS], 1989a).

All soil invertebrates observed on RMA were presumed also to inhabit the Offpost OU.

Earthworms were collected for the RI Addendum (HLA, 1992). These species are important prey

items in terrestrial food chains for both mammalian and avian wildlife. Other invertebrates

collected included grasshoppers, which also serve as important food items for both mammalian

and avian species.

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Upland vegetation, reptiles, and amphibians were inferred or were observed in the offpost

area but were not collected as part of the RI Addendum (HLA, 1992).

The terrestrial species selected as representative indicators of COC effects included

earthworms, grasshoppers, mice, prairie dogs, pheasants, great horned owls, American kestrels,

and bald eagles. These species fit many of the selection criteria shown in Table 5.2.1 - 1. Adverse

effects in bald eagles and great horned owls were considered representative of effects in other

large raptors.

Terrestrial agricultural receptors selected include crops, chicken, and cattle because of their

role in the human food chain. Crops represent all terrestrial plants because of a lack of specific

data for most noncultivated plant species.

5.2.1.2 Aouatic Recevtors

Potential freshwater aquatic receptors (Table 5.2.1-2) have been observed or are believed to

be present in a variety of aquatic habitats, as described in the RI Addendum (HLA, 1992).

Wetland resources were limited in the offpost area to riparian/floodplain areas adjacent to the

creeks, rivers, and impoundments. First Creek and Second Creek are intermittent streams that do

not support economically important fish populations.

Specimens collected from the First Creek Impoundment included macrophytes and algae,

aquatic insects, crayfish, and fathead minnows (HLA, 1992). Fathead minnows are expected to

provide food items for omnivorous wading birds. Fathead minnow tissue body burden data from

the offpost area are reported in the RI Addendum (HLA, 1992).

Carp and bullhead catfish are expected to occur in the O'Brian Canal and other water bodies

linked to the South Platte River. Despite seining of the entire First Creek Impoundment from

bank to bank, only fathead minnows were collected (HLA, 1992). The pond is shallow, and

Winter kill due to ice is expected to occur; thus, permanent populations of large fish are not

anticipated. Previous reports of carp in this waterbody may be attributable to stocking the

impoundment with fish collected from other areas. The freshwater aquatic species selected as

representative for evaluation of contaminant effects and the predominant criteria for their

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inclusion are summarized in Table 5.2.1-2. Larger fish (carp and bullhead) were not included in

the food web because they were not found during the ecological characterization prepared for the

RI Addendum (HLA, 1992).

Fathead minnows (Pimephales promelas) were observed in the First Creek Impoundment.

This organism may have contact with sediments, thus increasing chemical exposure. This species

may be an important prey item for higher trophic level biota such as great blue herons.

Crayfish (Orconectes sp.), a scavenging invertebrate, were also found in the First Creek

Impoundment. Ecotoxicity data specific to this taxa are more limited, but invertebrate data for

other species present at the site may be substituted with consideration of the resultant uncertainty

inherent with extrapolation among taxa. Other aquatic invertebrates are expected to occur in the

Offpost OU but were not collected during the RI Addendum (HLA, 1992).

Green algae were present in aquatic habitats of the Offpost OU and were collected as algal

mats for analysis in the RI Addendum (HLA, 1992). Algae represent primary producers in the

aquatic ecosystem.

Various waterfowl and shorebird species are common to the aquatic habitats in the offpost

area. These birds have a variety of different feeding habits and are potential pathways to higher

trophic level species, including humans. Toxicity data are available for different waterfowl

species, but most data pertain to the mallard duck (Anas platyrhynchos). The bald eagle, mallard

duck, and great blue heron were selected as representative avian species associated with aquatic or

wetland systems to evaluate the potential adverse effects of the COCs.

5.2.2 Potential Ext)osure Pathways

The ecological conceptual site model, as shown in Figure 5.2.2- 1, depicts the sources and

pathways of exposure to the potential receptors. Essentially, the conceptual site model summarizes

the exposure scenarios that were considered for each major receptor component of the ecological

risk assessment. The model also indicates whether a specific pathway considered for evaluation

was quantified.

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Potential exposure pathways in relation to each media source are summarized in

Table 5.2.2- 1. It was difficult to evaluate some exposure scenarios with respect to biological

receptors because of the lack of applicable exposure factors. For example, evaluating dermal

contact toxicity data for mammals and wildlife species is not similar to the types of dermal

exposure studied under experimental conditions. Under experimental (laboratory) conditions, the

animal's hair is usually shaved, and the test compound applied directly to the skin. Under field

conditions, only the foot pads or nose directly contact contaminated media. The dermal exposure

pathway is expected to,be minor compared to soil, water, or contaminated prey ingestion.

Inhalation of vapors or fugitive dusts is also expected to be a minor exposure pathway for

wildlife species and agricultural receptors compared to ingestion. Most of the Cocs in surface

water, sediment, and surface soil are not volatile. Although the offpost area is expected to be

dusty, especially during agricultural activities, the relatively low levels of COCs in surface soil

(Mg/kg or ppb) were expected to minimize risk via inhalation because of low exposure point

concentrations.

Ingestion exposure pathways were evaluated because wildlife may ingest surface water or

soil as part of burrowing, feeding, or grooming activities. Wildlife may also be exposed by

ingestion of contaminated food items. Direct contact and ingestion of contaminated food items

were considered for aquatic life. Exposure pathways are listed in Table 5.2.2-1 and are described

below for each of the receptor species.

For earthworms, direct (i.e., dermal) contact is the most important exposure pathway. As

with aquatic organisms, separating ingestion from dermal absorption from the surrounding media

is difficult. Therefore, toxicity and bioaccumulation were evaluated in relation to direct contact

with soil.

Grasshoppers may be exposed by direct contact with soil and ingestion of contaminated

plants and soil. Quantifying the exposure by direct contact through soil ingestion is difficult

because of limited information regarding this exposure route. Therefore, toxicity and bioaccumulation were considered in relation to ingestion of plants.

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Mice and prairie dogs may be exposed by ingestion of contaminated soil with dietary items.

Exposure by dermal contact is difficult to quantify because of limited information regarding this

exposure route for wildlife. Because these species are very effective in conserving body water and

receive most of their hydration via dietary intake, they consume little or no surface water .

Contact with groundwater by these species is unlikely. Toxicity and bioaccumulation were

considered in relation to ingestion of surface water, soil, invertebrates, and plants.

Pheasants may be exposed by direct or dermal contact with soil or surface water, dietary

ingestion. and soil ingestion. Quantifying exposure by dermal contact is difficult because of

limited information regarding this exposure route in avian species, but it is unlikely to be a major

exposure pathway compared to ingestion. Surface water is consumed by pheasants; however,

contact with groundwater is unlikely. Soil is ingested during feeding activities, but the actual

exposure rates are uncertain. Toxicity and residue bioaccumulation were considered in relation to

ingestion of soil, surface water, invertebrates, and plants.

Great horned owls, American kestrels, and bald eagles may be exposed by dermal contact,

dietary ingestion, and soil and surface-water ingestion. As stated above, dermal contact is not

like]v to be a significant pathway compared to ingestion. Surface water is consumed by these

species. but contact with groundwater is unlikely to occur. Limited quantities of soil may be

ingested during feeding activities, but the actual exposure rate to soil is likely to be much less than

for ground-feeding birds such as the pheasant. Ecological receptor soil ingestion rates determined

for the Onpost EA (Ebasco, 1992 [Appendix H]) were used in this ecological risk assessment for

consistency with the onpost ecological risk characterization. Toxicity and bioaccumulation were

also considered in relation to surface-water, soil, and dietary (prey species) ingestion.

The lower trophic level freshwater aquatic receptors (green algae, crayfish, and fathead

minnows) mav be exposed by direct contact with their environment and, for some, via dietary

ingestion. The higher trophic level organisms in the aquatic food web (mallard, bald eagle, and

great blue heron) may be exposed by dermal contact, surface-water and sediment ingestion, and

dietary ingestion of contaminated prey. Quantifying the exposure to higher trophic level

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receptors by dermal contact is difficult because of limited information regarding this exposure

route for wildlife. These species consume surface water; however, contact with groundwater is

unlikely to occur. Limited quantities of sediment may be ingested during feeding activities.

Toxicity and bioaccumulation were considered in relation to ingestion of surface water, sediment,

and pre), species.

Species in the agricultural food web may be exposed by dietary intake, surface-water intake,

soil intake, and intake of contaminated groundwater via ingestion from agricultural wells.

Toxicity and bioaccumulation for these species were considered in relation to each of these

potential exposure pathways.

5.2.3 Exposure Point Concentrations

The groundwater exposure point concentrations developed for the human health assessment

and presented in Section 2.4 (Table 2.4.2.5) were applied for agricultural biota. However, for

wildlife receptors, the soil exposure point concentration for zone 3 was based on the geometric

mean of the soil concentration rather than the UCL95 of the arithmetic mean used for the human

health assessment. Additionally, a re-evaluation of the sediment and surface-water data indicated

that the most reasonable exposure point concentration would be a geometric mean of useable data

points because the data are not normally distributed. The data were evaluated in a manner similar

to that used for the selection of appropriate data points for the groundwater exposure point

calculations for the human health assessment described in Volume 11, Section 2.0 of the EA.

Geometric means were calculated for COCs, using all single value data points. In cases where

duplicate samples were analyzed by two different methods, data for the method with the higher

detection limit were eliminated if the following conditions occurred: (I) the eliminated value was

a nondetection, (2) a duplicate sample was analyzed using a method with a lower detection limit,

and (3) one-half the detection limit of the removed value is greater than the highest detected

concentration for that analyte in zones 3 or 4. The exposure point concentrations for surface

water, soil. and sediment are listed in Table 5.2.3- 1. Terrestrial species are exposed to soil; some

species may also contact surface water via ingestion. Lower trophic level aquatic species are

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exposed to surface water continually by immersion in their environment. Toxicity to aquatic life

resulting from contact with sediments was evaluated with the surface-water assessment. Livestock

and crops may contact soil, surface water, or groundwater from agricultural wells.

5.2.4 Ecological Assessment Endpoints

Ecological assessment endpoints are expressions of values or characteristics that are to be

protected. If these endpoints are determined to be significantly or adversely affected, remedial

action is indicated (EPA, 1989f). The assessment endpoints for the Offpost EA were direct

toxicity and bioaccumulation, which are indicated as potentially useful by EPA (1989f), and ones

that can be addressed with the Offpost RI data and the food web models. EPA indicates that its

list is not all inclusive and that other assessments endpoints are possible.

A measurement endpoint corresponds to or is predictive of assessment endpoints and can

include data or models. The assessment endpoints were evaluated with the measurement endpoints

of observed tissue concentrations and observed abiotic media concentrations, both of which can be

correlated with mortality or sublethal toxic effects by use of data found in the toxicity

assessments.

5.2.4.1 Terrestrial

Differences in species composition and/or distribution between RMA and the Offpost OU

are influenced by land use and management, and thus comparison of population stability or

diversity (as measured by species diversity, abundance, and productivity) or ecosystems

productive capability (as measured by biomass or productivity) in relation to RMA is difficult, if

not impossible. One assessment endpoint considered applicable for the ecological risk assessment

was the link between TCOC residues and adverse effects. This assessment endpoint was evaluated

by predicting TCOC levels, using food web modeling and comparing these levels to MATCs. The

MATCs (described in Section 3.4 of Volume II) are tissue concentrations that correspond to no

effect or minimal adverse effect in a few members of a population. Tissue residues may be

indicative of impacts to sensitive individuals and populations.

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Another ecological endpoint evaluated in this assessment was direct toxicity. Soil, water,

and food intakes were evaluated for contaminant levels that could be correlated with direct

toxicity. These intakes were compared with the TRVs contained in Section 3.3 of Volume Il.

This approach was relied upon, in part, because some COCs do not bioaccumulate in food webs

and also to address exposure directly to abiotic media. TRVs are equivalent in concept to RfDs

developed for human health. TRVs are a daily intake level that should not result in an adverse

health effect to a population or an endangered species. The ratio of chemical intakes to TRVs is

defined as a hazard quotient (HQ) for the purposes of this EA.

Although other environmental assessment endpoints may exist (EPA, 1988; EPA, 1989f),

these endpoints may be subject to confounding exposures not associated with RMA. The use of

registered insecticides and herbicides in the Offpost OU, the discharge of sewage effluent to Barr

Lake (DRCOG, 1989), and the possible presence of contaminants in the South Platte River makes

assessing the ecological risk attributable to chemicals from RMA sources difficult to separate from

the risk from other sources.

5.2.4.2 Aouatic

Wetlands and habitats critical for survival of endangered species are generally considered

sensitive habitats (EPA, 1989f). Barr Lake is an important migratory bird habitat and recreational

area, but intense management activities, historical input of effluents and runoff (DRCOG, 1989),

and human use make quantitative evaluation of RMA contaminant effects uncertain. Because of

the level of habitat disturbance caused by land use practices in the Offpost OU, the assessment

endpoints considered most applicable for the aquatic assessment were measured using the

following criteria: (1) TCOC concentrations in biota using food web modeling and MATCs and

(2) direct toxicity using TRVs. Other criteria include the AWQC that were used to determine risk

to aquatic life. These measurement endpoints provide the best indication of potential adverse

impacts in wetlands and aquatic systems resulting from site-related contamination.

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5.2.5 Bioaccumulation ExL)osure

This section describes the procedures used for modeling the bioaccumulation of TCOCs in

terrestrial and aquatic food webs. Predicted tissue concentrations are compared to MATCs in

Sections 5.3.1 and 5.3.2.

5.2.5.1 Terrestrial Food Web Ingestion Pathways

Dietary and soil ingestion exposure pathways were evaluated for TCOCs, using food web

modeling (ESE, 1989b; Fordham and Reagan, 1991) and analytical data. The food webs were

made site-specific by including the offpost terrestrial and aquatic receptors. The food webs also

outlined critical exposure pathways for each of the receptor species.

The terrestrial food web is presented in Figure 5.2.5.1 - 1. The indicator species that were

sampled for chemical analysis consisted of all lower trophic animals. Bioaccumulation factors

(BAFs) for each species were developed from the open literature on the basis of a scientific

consensus and are presented in Appendix H (Table H2-1). A BAF is the ratio of a chemical

concentration between tissue and intake, e.g., Cbi.t.,/Cdi.t- By definition, BAF includes uptake

from both water and dietary intake. Because soil is frequently ingested along with diet, residues

resulting from soil ingestion are considered as well. For the terrestrial species in the Offpost OU,

many of which do not consume surface water as a drinking water source, the bulk of the chemical

body burden is expected to be derived from soil and food ingestion. Residues resulting from

surface-water ingestion are considered in Section 5.2.6.1.

The BAFs were developed through literature research and are contained in Appendix H.

The BAFs for the species are intended to represent bioaccumulation by all members of the

specific trophic compartment. A medium-sized bird BAF was not provided in the Onpost EA

data; therefore, the BAF for the small birds was used to represent the pheasant ( Table H2-1 of

Appendix H). Prairie dogs were considered as medium-sized mammals.

The food chains in the terrestrial food web (Figure 5.2.5.1 - 1) are presented in Table H2-1 of

Appendix H, using producer/consumer notation as indicated by arrow symbols (e.g., earthworm -

> mouse). The total BAF (product of all BAFs in the food chain) for each food chain pathway for

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each COC is also reported in Table H2-1 of Appendix H. The total BAF values for each food

chain pathway were obtained by multiplying each of the individual BAFs in each pathway (Table H2-1). For example, the calculation of the total BAF for aldrin for a soil pathway is

illustrated below.

BAFs Total BAF

6 x 3 x 19 342

Soil Earthworm Deer Mouse Owl

Dietary fractions for each food chain pathway, as shown in Table 5.2.5.1-1, were multiplied

to obtain an overall dietary importance value for the food chain for the target organism. The

results are shown in the column labeled percent organism in Table 1-12-1 of Appendix H. For

example, food habits data indicate the owl feeds primarily (66.5 percent of diet) on deer mice, a

small mammal (Table 5.2.5.1 - 1), and that deer mice eat a mixed diet, of which 48 percent is

grasshoppers, an insect; therefore, this food chain contributes 32 percent of the owl's dietary

intake:

Soil Plants Grasshoppers Deer Mouse Owl

1.0 x 1.0 x 0.48 x 0.665 0.32

In general, dietary fractions were estimated from data used for the Onpost EA (Eba-sco, 1992

[Appendix H]). Because the bald eagle's diet in the offpost area also includes a small fraction

(0.031) derived from the aquatic food web, the bald eagle dietary fraction does not add up to 1.0

in the terrestrial food web.

By definition, a biomagnification factor (BMF) is a more general term that implies food

chain transfer of residues. BMF is used to define the uptake by higher trophic level organisms

caused by feeding in an entire food web.

The total BMF for a higher trophic level target organism is the sum of the products of the

total BAF multiplied by fraction of pathway in the diet of the higher trophic level target species

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(Table H2-1 of Appendix H). This adjusts the total BMF to reflect the contribution of the

respective pathways (n) for the target organism (Table 5.2.5.1 -1).

E (total BAF1 x dietary fraction,) = total BMF (5-1)

n=1

To summarize, the dietary fraction of the pathway was multiplied by the total BAF for the

pathway, and these values were summed for each species (Table H2-1 of Appendix H). The sum

of the food chain pathways as depicted in Table H2-1 in Appendix H, for each target organism

(i.e., bald eagle or owl) was labeled the total BMF. The total BMF represents the overall

biomagnification predicted from soil and all the food chains leading to the target organism. The

major species group (Table H2-1 of Appendix H) is presented to provide consistency with the

onpost ecological risk characterization.

Soil was considered part of the dietary intake because soil intake data are frequently

expressed as a percent in relation to diet. Contaminant uptake caused by surface-water ingestion

was considered separately because surface-water intake rates for birds may exceed feed intake on

a weight or volume basis (Sax, 1984) and are not usually expressed as a percent of the dietary

intake. Absorption factors for uptake from water or soil were conservatively assumed to be

equivalent to those for diet.

5.2.5.2 Terrestrial Food Web Predicted Tissue Concentrations

The predicted tissue concentrations of the five OCPs for the terrestrial food web species are

depicted in Table 5.2.5.2- 1. The predicted tissue concentrations were calculated by multiplying

the geometric mean soil concentration of each OCP for zone 3 by the species- and chemicalspecific total BMF developed from literature BAF values (Appendix H); also, a spatial adjustment

factor was applied for the bald eagle, American kestrel, and great horned owl. For example, to

determine the predicted tissue concentration of dieldrin for the American kestrel, the following

equation was applied:

(0.043 mg/kg x 13) x 0.2 = 0.11 mg/kg

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where:

0.043 mg/kg = soil dieldrin concentration

13 - total BMF for dieldrin for the American Kestrel

0.2 = spatial adjustment factor

Literature BAF values were used because offpost data were insufficient to determine site-specific

values, and onpost data and values, which may have been appropriate for use, were unavailable.

For those species occupying the upper trophic boxes and having a known home range (i.e., bald

eagles, American kestrels, and great horned owls), the predicted tissue concentrations were

spatially adjusted based on the home range for that particular species (Appendix H). The home

range adjustment was deemed appropriate because these animals are mobile and will only obtain a

fraction of their prey items within zone 3. The spatial adjustment factor is based on a ratio of the

known home ranges of the species and the area of zone 3.

5.2.5.3 Aguatic Food Web Ingestion Pathways

The aquatic food web is presented in Figure 5.2.5.3-1. The shaded boxes indicate samples collected as part of the RI sampling program. Large fish (carp, bullhead) do not appear on

the food web (reflecting current conditions). Thus, large fish were not evaluated as part of the

food web model. Herons are assumed to feed primarily in the aquatic food web.

Dieldrin and arsenic were the only TCOCs observed in the species collected in the aquatic

food web (HLA, 1992). Aquatic biota samples were collected from the First Creek Impoundment

only because First Creek, an intermittent stream, was not found to support fish during the

ecological characterization. For small aquatic species such as invertebrates, it is assumed that the

surface area to volume ratio as well as the exchange of water across the gills causes sufficient

absorption of chemical from water to outweigh uptake from diet. Species higher up the aquatic

food chains obtain chemicals through dietary intake as well as from direct uptake from water.

Bioconcentration factors (BCFs), the ratio of chemical concentration in tissue to chemical

concentration in water, were obtained from the open literature (Table H2-2 of Appendix H).

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5.2.5.4 Aguatic Food Web Predicted Tissue Concentrations

The predicted tissue concentrations of the five OCPs and arsenic for the aquatic food web

species are depicted in Table 5.2.5.4-1. The predicted tissue concentrations were calculated by

multiplying the exposure point concentration of each chemical in surface water by the speciesand chemical -specific total BMF developed from literature BCF values (Appendix H) for the

major receptor species in only the BCF values for algae and invertebrates. Literature BCF values

were used because offpost data were insufficient to determine site-specific values. A spatial

adjustment was applied in a similar manner to that described previously for the terrestrial food

web for bald eagles and the great blue heron. The spatial adjustment factor included feeding in

zones 3 and 4. A spatial adjustment factor was not derived for the mallard duck because home

range data were not available for consideration; therefore, the predicted tissue concentrations for

the mallard duck are likely overestimated based on dietary intake from a single area. The

predicted tissue concentrations based on the direct ingestion of sediment were also calculated in a

similar manner (Table 5.2.5.4-2).

5.2.6 Direct Exr)osure to Chemicals of Concern

Procedures used to calculate the species' intake from surface-water ingestion, soil ingestion,

dietary ingestion, and direct contact are discussed in this section. However, the intake values are

presented in Tables 5.3.1 -1 through 5.3.1-5 where these intakes are evaluated with respect to

TRVs in Section 5.3.

5.2.6.1 Surface-Water Ineestion Pathway

Species that do not rely on surface water as a primary drinking water source (e.g., prairie

dogs) are less likely to be exposed to potentially contaminated surface water. Birds, however,

often drink surface water. Birds with limited home ranges that overlap a contaminated water

source may conceivably obtain all their drinking water from the contaminated source. Large

mammals and raptors with a relatively larger home range may not have as high an exposure rate

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because of the opportunities to obtain water from uncontaminated sources. Surface-water

ingestion was evaluated for the following species:

Water Intake

Sipecies O/ke-bw/day)

Ring-necked pheasant 0.25

Great horned owl 0.25

American kestrel 0.25

Bald eagle 0.25

Mallard duck 0.25

Great blue heron 0.25

Water intake rates for terrestrial avian species were estimated from chicken data (Sax, 1984),

because similar data were not available for offpost area species. Water intake is expected to vary

among species, locations, and seasons, when different dietary components may supply more water

or when different energy expenditures require more water intake. Although mallards were

reported to consume 0.2 1/kg-bw/day, in exposure intakes, they were conservatively modeled as

ingesting 0.25 1/kg-bw/day to account for water intake during feeding and bathing activities.

Great blue herons were also assumed to ingest 0.25 1/kg-bw/day.

The other components of the terrestrial food web (earthworms, grasshoppers, mice, and

prairie dogs) either do not consume surface water as a drinking water source, or they are fairly

immobile and cannot access surface water. However, all surface-water intakes were based on

avian water intake rates, and these intake rates were assumed to be protective of other species

(e.g., small mammals) in the terrestrial food web. In general, water intake per unit body weight

for various mammalian species varies between approximately 0.05 to 0.2 1/kg-bw/day (Sax, 1984).

Therefore, the use of avian intake rates would provide conservative (high) exposure estimates for

mammals because deer mice and prairie dogs in the terrestrial food web do not ingest surface

water as a drinking water source.

Direct ingestion is considered to be exposure to surface water caused by consumption, and

direct toxicity is the adverse effect resulting from such exposure. The exposure point COC

concentrations in surface water are presented in Table H3-1 of Appendix H with the estimated

chemical intakes by avian species (raptors, heron, mallard, or pheasant). Chemical intake was

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calculated by multiplying the exposure point concentration in surface water (,ug/1) by the daily

water intake for birds (0.25 1/kg bw/day). Total chemical intakes via all appropriate routes of

exposure were compared to the TRVs presented in Section 3.0 to calculate an HQ to estimate

potential hazards (Section 5.3).

5.2.6.2 Direct Contact with Surface Water or Sediment

Aquatic life (fish and macroinvertebrates) has direct contact with surface water and

sediment in the environment; however, toxicity data with respect to contact with or ingestion of

contaminated sediments are lacking for many of the COCs for the species of interest. Toxicity to

aquatic life was estimated from direct contact with surface water and ingestion of sediment.

TRVs for aquatic life were compared to the surface water, sediment, and dietary intakes and are

addressed in Section 5.3, Risk Characterization.

5.2.6.3 Soil Inpaestion

Soil ingestion by terrestrial biota for residue calculations was addressed previously via the

terrestrial food web model. Soil ingestion rates are often presented as a fraction of the diet;

however, as with surface water, direct toxicity as well as residue accumulation should be

considered. Direct toxicity as a result of soil ingestion was predicted using the exposure point

concentrations presented in Section 2.4. Up to 2 to 3 percent of the daily food intake may be

composed of soil (Palmer and Fowler, 1975) (Table 5.2.5.1-1). Total daily food intake was

determined to be a percentage of total body weight (Ebasco, 1992). Intakes were calculated on

these values. In addition, aquatic birds (e.g., mallard or heron) may also ingest soil during nesting

or feeding activities. The chemical intakes from sediment are assumed to represent soil intake by

these species. The species -specific soil and sediment dietary fractions are listed in Appendix H.

Potential exposure to the terrestrial plant species (crops) in the Offpost OU could result from

direct uptake of chemicals in soil, groundwater, and surface water in the affected areas. Exposure

point concentrations of the COCs identified are presented in Section 2.4.2. Hazard to plants is

addressed in Section 5.3.

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5.2.6.4 Dietary Ingestion for Wildlife

Dietary intakes were derived by multiplying the estimated tissue concentrations in prey

items (next lower trophic level) for both terrestrial or aquatic life (Tables 5.2.5.2-1 and 5.2.5.4-1

by the dietary fraction (Table 5.2.5.1 -1) to obtain mg chemical/kg diet. Estimated concentrations

in prey were obtained by use of the food web model. Assuming daily dietary ingestion rates listed

in Appendix H (Ebasco, 1992), the following equation was derived.

Prey residue x f x r I x SAF = Chemical intake

(mg/kg diet) (mg/kg-bw/day)

n= 1 (5-2)

where:

f = dietary fraction of prey item (unitless)

r = daily dietary ingestion (feed) rate (kg prey/kg-bw)

SAF = spatial adjustment fraction (unitless)

The chemical intake from each component of the food chain is additive (due to the dietary

fraction term); thus the total dietary intake is the sum of the amount of chemical in relation to

each of n prey items. For example, in the terrestrial food web, the bald eagle consumes prairie

dogs (91.5 percent), deer mice (0.5 percent), and pheasants (1.9 percent); therefore, the dietary

DDE intake for the eagle is [[(0.03 x 0.915) + (0.54 x 0.005) + (0.27 x 0.019)] x 0.09] x 0.0009 or

2.8 x 10-6 mg/kg-bw/day. The value 0.09 represents the feeding rate, and the value 0.0009 is the

spatial adjustment factor for the bald eagle.

5.2.6.5 Dietarv and Soil Inpestion Pathways for Livestock

The dietary and soil ingestion pathways were evaluated for chickens and cattle. Only

zones 1, 2. and 6, classified as the rural residential scenario, were evaluated for potential COC

effects on chickens and cattle. The agricultural food web (Figure 5.2.6.5-1) indicates the potential

exposure pathways.

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Chickens may be exposed to COCs through direct soil consumption. The chicken intake for

soil ingestion was calculated as follows:

Chicken soil intake = CS x IS (5-3)

BW

where:

CS = concentration in soil (mg/kg)

is = soil ingestion rate = 200 mg/day

BW = body weight of chicken = 2.5 kg

Cattle may be exposed to COCs from the soil through incidental soil ingestion while feeding.

Exposure to the COCs in the groundwater and surface water could occur from direct water

consumption. Cattle forage may bioaccumulate COCs from soil or irrigation water. Explanation

of the classification of the groundwater and surface-water use patterns is in Section 2.2.2.4.

The intake from contaminated media was calculated by a procedure designed to be consistent with the estimates of concentrations in meat used in the human health assessment

(Section 2.4.2). The procedure was as follows:

Cattle plant intake (mg/kg/dav) = CFM x lp (5-4)

KPM x BWM

where:

CFM = concentration of the chemical in beef (mg/kg, fresh weight)

IP = ingestion rate of feed (kg/day, fresh weight)

B Wm = body weight of the cattle (kg)

KPM = equilibrium partition coefficient relating chemical concentration in aboveground

plant part to concentration in the soil aqueous phase (1/kg)

By substituting equation 2.4.2-4 for CFM into equation 5-4 and rearranging terms, it can be

shown that equation 5-4 is equivalent to the following:

Intake = CPIP + CWIW + Cals (5-5)

BWM

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M

where:

Iw = ingestion rate of water by cattle

is = ingestion rate of soil by cattle

CID = concentration of chemical in plant

IP = ingestion rate of feed

Cw = concentration of chemical in water

C., = concentration of chemical in soil

BWm = body weight of cattle (kg)

Equation 5-4 was applied using a zone-specific estimated concentration in meat

and IP = 37.7 kg/day, BWM = 450 kg. The CFM values are provided in Table H4-1 of Appendix H. The KPM values are included in Table 2.1-10.

5.3 RISK CHARACTERIZATION

Potential hazards to the different ecological components of the Offpost OU were addressed

by considering the risk to terrestrial, aquatic, and agricultural life separately. Bioaccumulation

and direct toxicity endpoints were evaluated for terrestrial and aquatic life; only direct toxicity

was evaluated for underwater aquatic life and agricultural life.

5.3.1 Terrestrial Food Web Ecolopical Risk

The toxicity of TCOC residues was evaluated when data were available. This type of

toxicity is applicable only to those contaminants that bioaccumulate; therefore, residue toxicity

was addressed only for the terrestrial food web for higher trophic level organisms. Residue

toxicity was estimated by using MATC values that were developed during extensive literature

searches (Volume IV, Appendix H). The MATC is based on soil and dietary intake and is also a

function of the residue assimilated by the top predator species, whereas the TRV considers intake

from all media, particularly for noribioaccumulative COCs. The MATC is specific for toxicity

relative to an organism's residue body burden, whereas the TRV accounts for any toxicologic

response to dose. The MATC's strength is that it allows comparison of observed biota data to

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tissue concentrations that, if exceeded, predict possible effects for species not included in the

sampling program (such as endangered species). The MATCs are in Appendix H.

MATCs were developed after reviewing literature describing tissue concentrations for avian

and mammalian species dosed in toxicity studies. In the food web models, multiple food chains

lead to a target organism, or sink species. Chemicals that bioaccumulate tend to concentrate

within each level of the food chain such that the sink species are exposed to higher concentrations

than the lower trophic level species. Because avian species are considered the sink species for the

offpost food webs (see receptor identification), soil criteria that are developed with the MATCs

and BMF for the sink species are assumed to be protective of lower trophic level organisms as

well. However, to validate this assumption, a comparison of estimated intakes for lower trophic

levels to their respective TRVs is necessary.

Tissue concentrations were predicted in the higher trophic level organisms in the terrestrial

and aquatic food webs that were not sampled as part of the offpost RI (HLA, 1992) (Table H2-1

and Table H2-2 of Appendix H). The predicted tissue residues for the avian species were

compared to the MATCs listed in Appendix H. The predicted tissue residues in birds feeding in

zone 3 exceed the endrin MATC for the great horned owl and American kestrel. A summary of

the ratio of predicted tissue concentrations to MATCs by birds feeding in the terrestrial web

follows:

Ratio of Predicted Tissue Concentrations to MATC

Terrestrial

Bald Great horned American Ring-necked

TCOC Eaple Owl Kestrel Pheasant

Aldrin <1 <1 <1 <1

Dieldrin <1 <1 <1 <1

Endrin <1 4 4 <1

DDE <1 <1 <1 <1

DDT <1 <1 <1 <1

Endrin is indicated as a potential concern to the great horned owl and American kestrel;

however, it should be noted that actual site data do not support the predicted tissues concentrations of endrin in lower trophic level organisms. Endrin was reported as BCRL (<0.036 mg/kg)

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in each of the biota samples analyzed (HLA, 1992). Samples were analyzed from members of the

following species, domestic cattle, domestic fowl, fathead minnows, carp, crayfish, algae,

grasshoppers, earthworms, deer mice, prairie dogs, and pheasants. A detailed presentation of the

various sample types collected from each species is in the RI Addendum (HLA, 1992).

Direct toxicity endpoints were also evaluated for the higher trophic level terrestrial species

by adding soil, surface water, and dietary intakes to derive a total intake. Total intake was

compared to TRVs (Volume 11, Section 3.0 and Table 3.3.3-1), and an HQ value was calculated

(Tables 5.3.1 -1 through 5.3.1-3). Menzie and others (1992) describe a similar HQ approach to

estimate potential health effects on birds. Their approach calculates an HQ ratio by comparing

the dose of contaminant received in diet to a dietary dose as a concentration of contaminant in the

diet associated with the LOAEL or NOAEL for a particular biological endpoint. The HQs were

modified by the application of a home range or spatial adjustment factor to adjust for partial

dietarv intake from the areas within the Offpost OU potentially having the greatest impact

(zones 3 and 4) relative to a particular species' home range. HQ ratios greater than I indicate a

potential for an effect but do not indicate the magnitude (i.e., severity) or provide a measure of

potential population level effects. Also, HQs do not represent the probability of an adverse effect

occurring. The HQ ratio simply compares estimated doses to benchmarks. This comparison is

very similar to the use of RfDs in the human health risk assessment and to the manner by which

water quality criteria are applied (water concentrations compared to benchmarks, the criteria).

The estimated chemical intakes did not exceed the TRVs for bald eagles, based on the

geometric mean soil concentration data for zone 3 and the surface-water data for both zone 3 and

zone 4. HQs for the American kestrel and great horned owl were only exceeded for sulfate (HQ

equals 2). The American kestrel HQ for dieldrin equaled 1. All remaining HQs for both species

were less than 1. Home range or spatial adjustment factors were also applied to the calculations

for these two species. Additional home range information on the principal receptors is in

Appendix H.

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Exposure estimates for deer mice (Table 5.3.1-4) and prairie dogs (Table 5.3.1-5) exceeded

fluoride and sulfate TRVs. The mammal exposure estimates include surface-water and soil

ingestion as well as dietary intake. These estimates are highly conservative because the small

mammals are unlikely to ingest surface water; however, intake estimates would be protective of

mammals not included as receptors in the food web that may ingest surface water (e.g., fox,

coyote, skunks, raccoons). The fluoride and sulfate exceedances are probably the result of

uncertainties in the TRV derivation process, as presented in Section 5.3.5.3. Only the zone 3 and

zone 4 data were evaluated for potential adverse effects on wildlife because exposure concentrations are less for soil in other zones and no COC-contaminated surface water or sediment

occurs in other zones.

5.3.2 Aquatic Food Web Ecolopical Risk

The bald eagle and great blue heron occupy the top trophic level of the aquatic food web.

Predicted tissue concentrations (Table 5.2.5.4- 1 ) were based on exposure point concentrations in

surface water. Predicted tissue concentrations were then compared to MATCs to determine

potential health effects to bald eagles, great blue heron, and mallard ducks feeding in the aquatic

food web. The direct ingestion of sediment does not contribute significantly to the predicted

tissue concentrations (Table 5.2.5.4-2).

MATCs for dieldrin, DDT, and DDE were not exceeded for bald eagles, great blue herons,

and for the mallard duck. Aldrin and endrin were not evaluated because they were not detected

in surface water.

Ratio of Predicted Tissue Concentrations to MATC

Aguatic

Bald Great Blue Mallard

TCOC Eagle Heron Duck

Dieldrin <1 <1 <1

DDE <1 I <1

DDT <1 <1 <1

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The combined intakes from soil, water, and diet (Tables 5.3.2-1 and 5.3.2-2) for great blue

herons and mallard ducks were compared to TRVs (Table 3.3.3- 1) and an HQ calculated. The HQ

for sulfate exceeded I for the mallard ducks. The great blue heron had no exceedances.

The. HQ for bald eagles, including dietary uptake from both the aquatic and terrestrial food

webs, is reported in Table 5.3.1 - 1. As described previously, the intake of the COCs did not

exceed the TRVs; therefore, the resulting HQs were all less than one. Essentially, the aquatic food

web pathway did not result in any predicted tissue concentrations for the COCs in the bald eagle,

thus, only predicted tissue concentrations via the terrestrial food web can be compared to the

MATC values. The intakes for most of the COCs from soil or water ingestion were minimal.

5.3.3 Underwater Aauatic Life

Risk to aquatic life was also evaluated by use of aquatic reference concentrations

(Table 3.3-1). The observed concentration in surface water was compared to AWQC, LOAEL, or

NOEL from the literature (Table 3.3- 1). Residue toxicity was not evaluated for aquatic life

because data regarding the toxicity of residues in tissue are largely lacking for these species. In

addition, because aquatic life are continually surrounded in their exposure medium, it is likely

that water concentrations are a better predictor of toxic effects than tissue levels. Chlordane,

dieldrin, fluoride, and DDT appear to present a potential for an adverse effect to aquatic life in

First Creek, based on a comparison of exposure point concentrations in surface water to TRVs

(chronic AWQC values) for aquatic life. Background information for the aquatic reference

concentrations was reviewed to determine whether any AWQC values were hardness dependent to

make the criteria more site-specific. The EPA AWQC for the surface-water COCs are not

dependent on water hardness.

5.3.4 Agricultural Life

Groundwater and soil exposure point concentrations for COCs (Tables 2.4.2.6-1 through

2.4.2.6-9) were compared to reference media concentrations for plants (Table 3.3- 1). Reference

media concentrations of the COCs in soil did not indicate any exceedances except for chloride as

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applied in irrigation water. The total dissolved salts (free ions) in the irrigation water were

elevated in the Offpost OU. An evaluation of whether exceedances of Colorado groundwater and

surface-water standards occur is included in the ARARs portion of the Offpost OU FS.

The potential impact of contaminants in soil on poultry was evaluated by calculating the HQ

as a ratio between the dose to the chicken from soil and the TRVs (Table 3.3.3-1). The HQs for

chickens based on the zones 1, 2, and 6 (rural residential) soil concentration data sets, did not

indicate a potential contamination impact on chickens (Table 5.3.4-1).

A hazard evaluation was performed to determine whether cattle maintained in the

Offpost OU could potentially be affected as a result of exposure to COCs in soil and irrigation

water through dietary consumption. The indirect exposure pathway includes consumption of

plants grown in contaminated soil and irrigation water. HQs calculated for cattle for the different

chemical compounds identified at the Offpost OU for zones 1, 2, and 6 are presented in

Table H4-1 of Appendix H. No exceedances above I occurred; therefore, the potential for

adverse health effects occurring to cattle is not indicated.

5.3.5 Ecoloeical Risk Assessment Uncertainty

This section of the ecological risk assessment addresses the uncertainty associated with each

element of the risk assessment and the overall impact on the risk assessment's conclusions. The

elements of uncertainty include those associated with particular analyses, methods, and techniques.

The discussion is limited to a qualitative presentation of uncertainty.

5.3.5.1 Site Characterization

Very little uncertainty is associated with the site characterization because onsite investigations were conducted and supplemented with historical data and aerial photographs. The

ecological risk assessment site characterization was conducted in conjunction with the

RI Addendum (HLA, 1992).

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5.3.5.2 Exposure Assessment

The matrix used to select potential receptor organisms relied on site-specific and EPA

guidance criteria, thus minimizing the uncertainty associated with this aspect of the ecological risk

assessment. Receptors were selected from all pertinent trophic boxes to ensure a complete

evaluation of the food web. The Offpost OU conceptual site model, as shown in Figure 5.2.2-1,

indicates that all possible sources and exposure pathways were considered, thus reducing

uncertainty.

The uncertaintv associated with the food web models, dietary intake calculations, and the

predicted tissue concentrations determined by the food web models may be high for reasons

discussed below.

The sediment intake rate provided for small fish is difficult to validate because of the

paucity of available information. Tissue residues predicted for the great blue heron can be

influenced significantly by the sediment intake of small fish because the small fish constitutes

37 percent of the heron's diet. Because the great blue heron and mallard duck predicted tissue

concentrations of COCs found in aquatic ecosystem appear to overestimate the observed data, a

large degree of uncertainty is associated with aquatic food web model and input parameters. The

sediment exposure point concentrations used in this assessment are based on a geometric mean of

the chemical residues contained in the sediment matrix. Although the geometric mean value is

less than the UCL95 of the arithmetic mean values used for the human health assessment, the use

of total sediment concentrations may not be the most appropriate value to use to measure

exposure. Recent reports indicate the free or bioavailable fraction of the total chemical present is

the most important factor in potential aquatic toxicity (DiToro and others, 1991; Adams and

others, 1992). Because the bioavailable fraction is not known for the Offpost OU sediment

samples. it is difficult to determine whether the evaluations overestimated or underestimated the

actual hazard to the aquatic receptors. Additional uncertainty exists for the hazard evaluation for

the bald eagle and great blue heron through the application of the spatial adjustment based on

home range information obtained from the open literature. Again, it is difficult to determine

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whether the spatial adjustment resulted in an overestimation or underestimation of the potential

hazards to these aquatic receptors.

The dietary intakes assume that the animal's intake is year round and from a very limited

area in the Offpost OU. Although these assumptions may be valid for small mammals that have a

limited home range and foraging area, the assumptions are not valid for more mobile species such

as the avian receptors; thus, more uncertainty is associated with avian dietary intakes. The

application of the spatial adjustment factor may reduce the uncertainty associated with Taptor

mobility relative to prey located in contaminated areas; however, no adjustment was made to

account for temporal influences. Bald eagles, with few exceptions (e.g., the Barr Lake pair),

winter at or near RMA for only a few months each year (November- March). During this time of

year, the most likely offpost aquatic foraging sites for the bald eagle are either intermittent Or

frozen, thus reducing intake from the aquatic ecosystem (USFWS, 1989a and 1989b). Likewise,

mallard ducks and the great blue heron are migratory. The USFWS report (1989a) indicates that

only a fraction of the wintering bald eagles may return to RMA on an annual basis, indicating a

fairly substantial turnover of the bald eagle population at the RMA roost. The report states that

possibly 100 or more eagles visited the RMA roost during the 1988- 1989 wintering season and that

casual observation of the eagles in early November suggests that up to seven of the eagles may

have returned from the previous year. Perhaps with more data, the probability of an individual

eagle wintering in the Offpost OU during its lifetime could be determined to evaluate the

temporal aspect of exposure to contaminated media more accurately. Similar data are also

desirable for the other avian species. More definitive temporal and spatial data on the foraging

habits of the receptors are required to reduce the uncertainty.

The exposure assessment for the agricultural receptors (i.e., chickens, cattle, and crops) has

less uncertainty because the database on exposure, absorption factors, uptake models, and toxicity

is more complete.

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5.3.5.3 Risk Characterization

Inherent uncertainty is associated with the comparisons between the predicted tissue

concentrations (food web models) and the MATCs and the dietary intakes compared to the TRVs

(HQs) because the MATCs and TRVs are based on the extrapolation of field and/or experimental

data from the open literature. The uncertainties pertaining to these comparisons is a combination

of the uncertainty contained in the MATC and TRV derivation procedures in addition to uncertainty associated with the food web models and intake parameters. The uncertainties related to

TRVs are presented in Section 3.5.

Some of the HQ exceedances (e.g., sulfate exceedances) may be an artifact of the TRV

derivation process. The TRV derivation process, by necessity, is rather structured, with minimal

opportunity for subjective scientific input. This approach was deemed most desirable because it

allows a derivation process that can be easily applied by anyone once the critical toxicity study has

been identified. A modifying factor addressing the quality of the toxicity study and its relevancy

to an ecological receptor would reduce the uncertainty associated with the TRVs and their

subsequent application to calculate HQs. However, because of the complexity of wildlife toxicity

issues and to reduce criticism, such a modifying factor should only be developed by a consensus of

scientific opinion from qualified individuals (a similar process as applied to RfDs).

The overall uncertainty with the ecological risk characterization could be reduced if sitespecific documented temporal and spatial home range data were available as well as more refined

MATCs and TRVs. The result of such adjustments would result in outcomes similar to RMEs

used in the human health assessment.

5.4 SUMMARY

A quantitative assessment of important exposure pathways was performed for nonhuman

receptors in the Offpost OU food webs. The results of the exposure assessment were expressed as

tissue residues or as estimated chemical intakes from water, sediment, soil, and diet.

The tissue residues were compared to MATCs. The intakes were compared to TRVs as part

of the risk characterization to obtain an HQ for each higher trophic level receptor and each COC.

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Significance is only attached to those comparisons that exceeded MATC or TRV criteria.

Uncertainties associated with the quantitative ecological risk assessment are related to

assumptions, some conservative and others not, made during the calculation of exposure point

concentrations, intakes, and adverse health effects. These assumptions are presented in the text

but are summarized below for clarity. The assumptions are qualitatively assigned in order of

impact on the risk characterization results.

I . The use of BAF and BCF values obtained from the open literature rather than sitespecific values introduced uncertainty because biological, chemical, and physical

characteristics unique to the Offpost OU may be very different from those present in the

studies reviewed from the literature.

The application of the spatial adjustment factor based on literature home range

information is another source of uncertainty. Although it is difficult to determine if the

approach presented in this assessment over- or underestimated the potential hazards, it is

generally known that the home ranges, per se, are not reflective of potential exposure, and

for animals that have a wide home range, such as the bald eagle, the foraging area may

only be a fraction of the total home range area.

3. Use of conservative soil, sediment, and surface-water intakes.

4. The equilibrium and steady-state assumptions for modeling are probably high (i.e.,

conservative), thus resulting in higher exposure estimates than the higher trophic level

species will experience because they can move in and out of the ecosystem.

5. The use of uncertainty factors, LOAELs, and NOELs in developing health effects levels

for TRVs is conservative.

6. The use of geometric mean exposure point concentrations for soil, sediment, and surface

water probably represents a more realistic scenario than the UCL95 values used for the

human health risk assessment; therefore, less uncertainty may be associated with this

aspect of the hazard evaluation.

The results of the risk characterization indicate that minimal potential for adverse effects to

receptor species in the aquatic and terrestrial food webs may exist. The available analytical data

on likely prey for the bald eagles (prairie dogs and pheasants) exhibited fairly low and infrequent

detections of the COCs (HLA, 1992). Other raptor species feeding in the terrestrial food web are

also not likely to be at high concern for risk as predicted body burdens were less than or within an

order of magnitude of the MATCs.

20000,317.10(3) - OEA

0815111892 111 - 5-35
Species in the agricultural food web are not expected to be at risk because of exposure to the

COCs. Plant life, cattle, and chickens will be relatively unaffected, based on the results of the

risk characterization.

20000,317.10(3) - OEA

0815111892 111 - 5-36
6.0 CONCLUSIONS

As indicated in the Preface to the EA, one of the objectives of the EA was to provide an

analysis of risks in the absence of additional remediation (baseline risks) and to provide a basis for

determining the need for remedial action at a site. The EA for the Offpost OU has determined

the cumulative hypothetical carcinogenic risk is a maximum of 3 x 10-4 on the basis of the RME

risks. The maximum risk is within the acceptable risk range as defined by EPA in the revised

National Contingency Plan (EPA, 1990a) and in the Role of the Baseline Risk Assessment in

Superfund Remedy Section Decisions (EPA, 1991c).

The calculated hazard indices presented in the EA and below 1.0, with the exception of

zones 2, 3,and 4, where the HIs slightly exceed 1.0.

Although the need for Offpost OU remedial action is not warranted because the Offpost OU

cumulative risk is 3 x 10-4, the Army recognizes that there are several site-specific factors, when

considered in totality, suggest remediation of groundwater is preferable to no action in the

Offpost OU. Accordingly, a Feasibility Studý; has been prepared as a companion document to the

EA for the Offpost OU.

20000,317.10 - (M)- 0EA

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20000,317.10 - (III) OEA

0306110992 111 - 7-26
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20000,317.10 - (III) OEA

0306110992 111 - 7-27
Table 4.0- 1: Target Organ- or System-specific Chemicals of Concern

Taraet Orean or System Chemical of Concern

Blood Benzene

Toluene

Cardiovascular 1,2-Dichloroethane

Atrazine

Central Nervous System DIMP'

1,4-Dithiane

Malathion

Manganese

Oxathiane

Toluene

Xylenes, total

Gastrointestinal Hexachlorocyclopentadiene

Liver Aldrin

Carbon tetrachloride

Chloroform

Chlorobenzene

Chlordane, total

CPMS

CPMSO

CPMS02

Dibromochloropropane

Dicyclopentadiene

Dichlorobenzenes, total

DDE

DDT

Dieldrin

1,4-Dithiane

Endrin

Ethylbenzene

Isodrin

Tetrachloroethene

Trichloroethene

Ocular Toluene

Renal Chlorobenzene

Dibromochloropropane

Ethylbenzene

Respiratory 1,2-Dichloroethane

Toluene

Xylenes, total

Skin Arsenic, total

Based on acute effects (EPA, 1989b).

20000,317.10 - OEA

0306111092
Table 4. 1.1 - 1: Summary of Residential Hypothetical Future Carcinogenic Risks:

Reasonable Maximum Exposure

Combined

Zone Cancer Risk' Maior Chemicals of Concern

]A <1 X 10-4 Arsenic, atrazine, dieldrin

IB <1 X 10-4 Arsenic, atrazine, dieldrin

1C <1 X 10-4 Arsenic, atrazine, dieldrin

2 <2 x 10-4 Aldrin, arsenic, atrazine, chloroform, dibro10-4 mochloropropane, dieldrin, tetrachloroethene

3 <3 x Aldrin, atrazine, dieldrin, tetrachloroethene

4 <2 x 10-4 Aldrin, arsenic, atrazine, chlordane,

1,2-dichloroethane, dieldrin

6 7 x 10-1 Aldrin, arsenic, dieldrin

I

Risks are rounded to one significant figure (EPA, 1989a).

Includes all chemicals, all pathways, RME intakes, and 95 percent upper confidence limit. (The

actual risk at the RME intake may be three-fold less, based on the uncertainty analysis.) The

"less than" symbol (<) indicates risk is upper-bound risk and that the true RME risk is less than

the risk indicated.

2 These Chemicals of Concern account for more than 90 percent of risk.

RME = reasonable maximum exposure

20000,317.10 - OEA

0306111092
Table 4.1.1-2: Summary of Residential Child Chronic Combined Noncarcinogenic

Hazard Indices (HIs >1)

Target Hazard

Zone Organ/System Indexi Chemicals of Concern 2

2 Liver 2 Chloroform, dieldrin

CNS 1.3 Manganese

3 Liver 2 Dicyclopentadiene, dieldrin

4 Liver 1.4 Chlordane

CNS 4 DIMp3

1 All chemicals in target system category, all pathways, RME intakes.

2 Elimination of these Chemicals of Concern would reduce HI <1.

3 CNS effects based on acute effects (EPA, 1989b).

CNS = central nervous system

RME = reaasonable maximum exposure

20000,317.10 - OEA

0306111092
Table 4.1.1-3: Contribution of Dieldrin and Other Chemicals to the

Child Acute Hepatic Hazard Index

Hazard Index by Contamination Zone

Chemical ]A IB IC 2 3 4 6

Dieldrin 0.76 0.96 0.76 1.0 3.8 1.5 0.76

Other 005 006 005 02 02 L2 2M

Total 0.81 1.02 0.81 1.2 4.0 1.7 0.81

20000,317.10 - OEA

0306111092
Table 4.1.1-4: Summary of Residential Hypothetical Future Reasonable Maximum Exposure

Subchronic Hazard Indices: Children

RME Subchronic Hepatic Total

Chemical Hazard Index Hazard Index

Zone Target System (Possible Range)' (Poss ble Ranpe)l

113 Dieldrin (H)

Chloroform (H) 2 - 4 4 - 7

Dieldrin (H)' i.i - 3

Manganese (CNS) 0.9 - 2

3 Chlordane (H) 0.8 - 2 5 - 14

Dieldrin (H) 4 - 10

4 Chlordane (H) 3 - 5 6- 13

Dieldrin (H) 3 - 7

Manganese (CNS) i.i - 2

5 Dieldrin (H) 1.3 -4 2 - 4

6 Dieldrin (H) i - 3 1.2 - 3

Low end of range is RME chronic intake divided by subchronic reference dose. High end of

range is RME acute intake divided by subchronic reference dose.

CNS = central nervous system

H = hepatic (liver)

RME = reasonable maximum exposure

S = skin

20000,317.10 - OEA

0306111892
Table 4.1.1-5: Summary of Residential Hypothetical Future Reasonable Maximum Exposure

Subchronic Hazard Indices: Adult Females

RME Subchronic Hepatic Total

Chemical Hazard Index Hazard Index

Zone Tareet System (Possible Ranjae)l (Possible Range)'

3 Dieldrin (H) 0.5 - 1.5 0.8 -2

4 Dieldrin (H) 0.2 - 0.6 0.6 - 1.3

Manganese (CNS) 0.7 - 1.1

Low end of range is RME chronic intake divided by subchronic reference dose. High end of

range is RME acute intake by subchronic reference dose.

CNS = central nervous system

H = hepatic (liver)

RME = reasonable maximum exposure

20000,317.10 - OEA

0306111092
Table 4.1.1-6: Comparison of Residential Reasonable Maximum Exposure and

Most Likely Exposure Hypothetical Future

Carcinogenic Risks by Zone

Zone RME MLE RME: MLE

IA I X 10-4 1 x 10-1 8:1

IB I X 10-4 1 X 10-1 9:1

IC I X 10-4 1 X 10-1 8:1

2 2 x 10-4 2 x 10-1 12:1

3 3 x 10-4 2 x 10-1 12:1

4 2 x 10-4 3 x 10-1 8:1

6 7 x 10-1 6 x 10-6 12:1

Risks include all chemicals and all pathways at the upper 95 percent confidence level RME intake.

RME risks may be overstated by three-fold, based on the uncertainty analysis.

MLE = most likely exposure

RME = reasonable maximum exposure

20000,317(6) - OEA

0306111092
Table 5.1.2- 1: Wildlife Species Observed in Offpost Operable Unit:

Winter 1989-90

Mammals

Coyote Canis latrans

Striped (Common) skunk Mephitis mephitis

Red fox Vulpes vulpes

Black-tailed jackrabbit Lepus californicus

Eastern cottontail Sylvilagus floridanus

Desert cottontail Sylvilagus auduboni

Black-tailed prairie dog Cynomys ludovicianus

Deer mouse Peromyscus maniculatus

House mouse Mus musculus

Meadow vole Microtus pennsylvanicus

Northern pocket gopher Thomomys talpoides

Mule deer Odocoileus hemionus

Ramors

Northern harrier Circus cyaneus

Ferruginous hawk Buteo regalis

Golden eagle Aguila chrysaelos

Other Bird Svecies

Ring-necked pheasant Phasianus colchicus

Mallard Anas platyrhynchos

Killdeer Charadrius vociferus

American white pelican Pelecanus erythrorhynchos

Great blue heron Ardea herodias

Western meadowlark Sturnella neglecia

Red-winged blackbird Agelaius phoeniceus

20000,317.10 - OEA

0306111092
Table 5.1.4- 1: Chemicals of Concern and Tissue Chemicals of Concern for the

Offpost Ecological Risk Assessment

Media

Ground- Surface

Analyte water Water Soil Sediment Biota

Ald rin x x x

Arsenic x x x x

Atrazine x

Benzene x

Carbon tetrachloride x

Chlorobenzene x

Chlordane x x x

Chloride x x

Chloroform x

CPMS x

CPMSO x

CPMS02 x

Dibromochloropropane x

Dichlorobenzene x

1,2-Dichloroethane x

Dicyclopentadiene x

DDEI x x x x x

DDT' x x x x x

Dieldrin x x x x x

DIMP x x

Dithiane x

Endrini x x x x

Ethylbenzene x

Fluoride x x

Hexachlorocyclopentadiene x

Isodrin x

Manganese x

Malathion x

Oxathiane x

Sulfate x x

Tetrachloroethene x

Toluene x

Trichloroethene x

Xylene x

1 Also a tissue chemical of concern.

20000,317.10 - OEA

0816110792
Table 5.2.1 - 1: Terrestrial Species Selected as Indicators of Ecological Impacts

Svecies Relation to Selection Criteria 2

Species' 1 2 3 4 5 6 7 8 9

Earthworm (sp.) x x x x x

Grasshopper (sp.) x x X X X

Deer mouse (sp.) X x X X x

Prairie dog x x x X X x

Shrew X x

Vole A x x x

Ground squirrel x x X

Skunk x x

Raccoon X

Fox X X

Coyote x X

Mule deer x x x X

White-tail deer x x X

Bald eagle X X X X x x x

Golden eagle X X X x x x

Ferruginous hawk x X x x x

Burrowing owl x X x X

Prairie falcon X X x x

Red-tailed hawk x X X x

Swainson's hawk x x x X

Northern harrier x x X x x

Great-horned owl X X x X

American kestrel X x X x x x

Peregrine falcon x X x X

Pheasant x X X X x X

1 Species in bold were selected as representative nonhuman terrestrial wildlife receptors or

indicators.

2 Selection criteria identified in Section 5.2, Exposure Assessment, of this report.

20000,317.10 - OEA

0816110792
Table 5.2.1-2: Aquatic/Wetland Species in Relation to Indicator Species Selection Criteria

St)ecies Relation to Selection Criteria

Species' 1 2 3 4 5 6 7 8 9

Green algae x x x x x

Vascular plants x x

Crayfish x x x

Fathead minnow x x x

Centrarchid fish x x x x

Mallard x x x x x x x

Pelican x x x x x

Great blue heron x x x x x

Bald eagle x x x x x x

Other waterfowl x x x x x

Other shorebirds x x x x

Other raptors x x x x x

1 Species in bold were selected as representative nonhuman aquatic wildlife receptors.

20000,317.10 - OEA

0816110792
Table 5.2.2- 1: Potential Exposure Pathways for Biota

Contaminated Route of

Media Exposure Exposure Point Recemor

Soil Ingestion Areas near the north boundary where Terrestrial

soil has elevated concentrations with mammals or birds

respect to background

Surface water Ingestion From First Creek, First Creek Aquatic,

Impoundment, or other surface-water terrestrial, avian,

bodies or mammalian

species

Surface water Direct contact From First Creek, First Creek Aquatic life

Impoundment, or other surface-water

by aquatic life

Sediment Ingestion From First Creek, First Creek Aquatic life

Direct contact Impoundment, or other surface-water

by aquatic life

Groundwater Ingestion From shallow wells in the offpost area Livestock

Groundwater Direct contact From shallow wells in the offpost area Crops

Biota (plant) Plant uptake From contaminated soil and irrigation Crops

water

Biota (animal) Ingestion of From any area with contaminated Aquatic or

biota biota in the offpost area terrestrial

consumers

1 Refers to receptors from Tables 5.2.1 -1 and 5.2.1-2.

20000,317.10 - OEA

0306110792
Table 5.2.3-1: Exposure Point Concentrations for Soil, Surface Water, and

Sediment Used for the Offpost Ecological Assessment

Soil, Surface Waterl Sediment'

COC (iua/kg) (URA) (uelkg)

Aldrin 5.08 NA 17

Arsenic NA 3.5 NA

Chlordane 17.90 0.18 ND

DDE 4.12 0.05 3

DDT 9.49 0.05 5

DIMP NA 11.9 NA

Dieldrin 43.45 0.12 18

Endrin 8.55 NA 6

Fluoride NA 1706 NA

Sulfate NA 282,840 NA

Geometric mean.

pg/kg = micrograms per kilogram

jug/l micrograms per liter

COC chemical of concern

DDE 2,2-Bis(p-chlorophenyl)-1,1-dichloroethene

DDT 2,2-Bis(p-chlorophenyl)- 1, 1, 1 -trichloroethane

DIMP = diisopropy1methylphosphonate

NA = not applicable

ND = not detected

200000,317.10(8) - OEA

0820111092
Table 5.2.5.1-1: Dietary Fractions for Each of the Species in the Terrestrial Food Web

Species Diet Fractioni Maior Species

Earthworms Soil 0.99 Worm

Plants Soil 1.0 Plant

Insects Plants 1.0 Insect

Deer mice Plants 0.47 Small mammal

Earthworms 0.03

Insects 0.48

Soil 0.02

Prairie dogs Plants 0.88 Medium mammal

Soil 0.08

Insects 0.04

Pheasants Plants 0.17 Small bird

Insects 0.72

Soil 0.06

Earthworm 0.05

Owls Small mammals 0.665 Raptor

Medium mammals 0.25

Small bird 0.055

Soil 0.03

Kestrels Small mammals 0.093 Raptor

Insects 0.86

Small bird 0.017

Soil 0.03

Eagles Medium mammals 0.915 Raptor

Small bird 0.019

Small mammal 0.005

Soil 0.03

1 Source: Ebasco, 1992 (See Appendix H7).

20000,317.10 - OEA

0816110792
Table 5.2.5.2- 1: Predicted Tissue Concentrations (mg/kg) for the

Terrestrial Food Web Ecological Receptors

Receptor Aldrin Dieldrin Endrin DDE DDT

American kestrel 0.01 0.11 0.04 1.33 3.60

Great horned owl 0.01 0.10 0.04 0.72 1.66

Bald eagle 0.00 0.00 0.00 0.00 0.00

Prairie dog 0.01 0.06 0.01 0.03 0.07

Deer mouse 0.01 0.11 0.12 0.54 1.24

Pheasant 0.01 0.07 0.09 0.27 0.62

Insect 0.00 0.04 0.01 0.18 0.43

Worm 0.03 0.26 0.25 0.01 0.03

Plant 0.00 0.02 0.00 0.01 0.01

DDT = 2,2-Bis(p-chlorophenyl)-1,1-dichloroethene

DDT - 2,2-Bis(p-chlorophenyl)-1,1,1-trichloroethane

mg/kg - milligrams per kilogram

200000,317.10(8) - OEA

0820110392
Table 5.2.5.4-1: Predicted Tissue Concentrations (mg/kg) for the

Aquatic Food Web Ecological Receptors on the Basis of

Surface-Water Concentrations

Receptor Aldrin Dieldrin Endrin DDE DDT Arsenic

Bald eagle 0.0 0.0 0.0 0.0 0.0 0.0

Great blue heron 0.0 0.2 0.0 1.1 1.1 0.0

Mallard duck 0.0 0.6 0.0 0.4 0.2 4.2

Small fish 0.0 2.0 0.0 3.5 3.5 0.1

Invertebrates 0.0 1.1 0.0 0.5 0.5 0.1

Algae 0.0 0.0 0.0 0.1 0.1 1.5

DDE = 2,2-Bis(p-chlorophenyl)-1,1-dichloroethene

DDT = 2,2-Bis(p-chlorophenyl)-1,1,1-trichloroethane

mg/kg = milligrams per kilogram

200000,317.10(8) - OEA

0820111092
Table 5.2.5.4-2: Predicted Tissue Concentrations (mg/kg) for the

Aquatic Food Web Ecological Receptors on the Basis of

Sediment Concentrations

Receptor Aldrin Dieldrin Endrin DDE DDT Arsenic

Bald eagle 0.000 0.000 0.000 0.000 0.000 0.000

Great blue heron 0.000 0.000 0.000 0.000 0.000 0.000

Mallard duck 0.004 0.004 0.000 0.002 0.003 0.000

Small fish 0.000 0.000 0.000 0.001 0.001 0.000

DDE = 2,2-Bis(p-chlorophenyl)-1,1-dichloroethene

DDT - 2,2-Bis(p-chlorophenyl)-1,1,1-trichloroethane

mg/kg - milligrams per kilogram

200000,317.10(8) - OEA

0820110392
Table 5.3.1-1: Summary of Intakes From Zone 3 Soil, Surface Water, and Diet for the Bald Eagle

Terrestrial

Soil and Water Aquatic Dietary Total

Intake Dietary Intake Intake Intake TRV

COC (mjr/kK-bw1daY) (mjz/kx-bw/daY) (mjz/kjz-bw/day) fmK/kjz-bw/daY) (mg/kg-bw1daY) HQ

Aldrin IAE-07 NA 7.5E-07 8.9E-07 2.8E-03 <1

Arsenic 8.8E-04 7.6E-06 NA 8.8E-04 3.OE-02 <1

Chlordane 5.2E-07 NA NA 6.2E-07 4AE-03 <1

DDE 1.2E-07 7.2E-07 2.8E-06 3.7E-06 2.7E-02 <1

DDT 2.7E-07 3.6E-07 6.6E-06 7.2E-06 2.7E-02 <1

DIMP 2.7E-06 NA NA 2.7E-06 3.8E-01 <1

Dieldrin 1.2E-06 IJE-06 4.5E-06 6.8E-06 2.8E-03 <1

Endrin 2.3E-07 NA 9.2E-07 1.1E-06 9AE-03 <1

Fluoridel 3.8E-04 NA NA S.SE-04 6.6E-01 <1

Sulfatel 6AE-02 NA NA 6AE-02 4.7E+00 <1

TRVs reported in Table 3.3.3-1. Other raptors represented by bald eagle TRV.

1 Cannot be addressed for dietary intake because (1) chemical is a naturally occurring component of diet or (2) cannot be

modeled because of a lack of data.

COC = chemical of concern

DDE = 2,2-Bis(p-chlorophenyl)-1,1-dichloroethene

DDT = 2,2-Bia(p-chlorophenyl)-1,1,1-trichloroethane

DIMP = diisopropy1methylphosphonate

HQ = hazard quotient

mg/kg-bw/day = milligrams per kilogram of body weight per day

NA = not applicable

TRV = toxicity reference value

20000,317.10 - OEA

0309111092
Table 5.3.1-2: Summary of Intakes From Zone 3 Soil, Surface Water, and Diet

for the American Kestrel

Soil and Terrestrial Total

Water Intake Dietary Intake Intake TRV

COC (mg/kp-bw/day) (mp/kp-bw/day) (mg/kja-bw/day) (mg/kg-bw/day) HO

Aldrin 3.OE-05 1.7E-04 2.OE-04 ME-03 <1

Arsenic 1.8E-04 NA 1.8E-04 2AE-02 <1

Chlordane 1.2E-04 NA 1.2E-04 8.8E-03 <1

DDE 2.7E-05 3.7E-03 ME-03 3. 1 E-02 < I

DDT 5.9E-05 8.8E-03 8.9E-03 3.1 E-02 < I

DIMP 6.OE-04 NA 6.OE-04 7.5E-01 < I

Dieldrin 2.7E-04 8.2E-04 LIE-03 ME-03 < I

Endrin 5. 1 E-05 3.8E-04 4.3E-04 3.8E-04 I

Fluoridel 8.5E-02 NA 8.5E-02 1.8E+00 < I

Sulfatel 1.4E+01 NA 1.4E+O I 9.4E+00 2

TRVs reported in Table 3.3.3-1.

Cannot be addressed for dietary intake because (1) chemical is a naturally occurring component

of diet or (2) cannot be modeled because of a lack of data.

COC = chemical of concern

DDE = 2,2-Bis(p-chlorophenyl)-I,I-dichloroethene

DDT = 2,2-Bis(p-chlorophenyl)-1,1,1-trichloroethane

DIMP = diisopropy1methylphosphonate

HQ = hazard quotient

mg/kg-bw/day = milligrams per kilogram - body weight per day

NA = not applicable

TRV = toxicity reference value

20000,317.10 - OEA

0311111092
Table 5.3.1-3: Summary of Intakes From Zone 3 Soil, Surface Water, and

Diet for the Great Horned Owl

Soil and Terrestrial Total

Water Intake Dietary Intake Intake TRV

COC (msx/kP,-bw/dav) (mP/kjz-bw/daY) (mp,/kp-bw/day) (mP,/kR-bw/dav) HO

Aldrin 9.1 E-06 5.2E-05 6AE-05 2.5E-02 < I

Arsenic 5.3E-05 NA 5.3E-05 2AE-02 <1

Chlordane ME-05 NA 3.5E-05 8.8E-03 < I

DDE 8.2E-06 2.OE-03 2.OE-03 3.OE-02 < I

DDT 1.8E-05 4.7E-03 4.7E-03 3.OE-02 < I

DIMP 1.8E-04 NA 1.8E-04 7.5E-01 < I

Dieldrin 8.OE-05 4.9E-04 5.7E-04 2.5E-02 < I

Endrin 1.5E-05 4.7E-04 4.8E-04 3.OE-03 < I

Fluoridel 2.6E-02 NA 2.6E-02 1.8E+00 <1

Sulfatel 4.2E+00 NA 4.2E+00 9.4E+00 <1

TRVs reported in Table 3.3.3-1.

Cannot be addressed for dietary intake because (1) chemical is a naturally occurring component

of diet or (2) cannot be modeled because of a lack of data.

COC = chemical of concern

DDE = 2,2-Bis(p-chlorophenyl)-I,I-dichloroethene

DDT = 2,2-Bis(p-chlorophenyl)- 1, 1, 1 -trichloroethane

DIMP = diisopropy1methylphosphonate

HQ = hazard quotient

mg/kg-bw/day = milligrams per kilogram - body weight per day

NA = not applicable

TRV = toxicity reference value

20000,317.10 - OEA

0311111092
Table 5.3.1-4: Summary of Intakes From Zone 3 Soil, Surface Water, and

Diet for the Deer Mouse

Soil and Total

Water Intake Dietary Intake Intake TRV

COC (mg/ke-bw/day) (mg/kg-bw/day) (mp,/ka-bw/day) (mg/kp,-bw/day) HO

Aldrin LOE-04 9.OE-05 1.9E-04 2.7E-02 <1

Arsenic 8.8E-04 NA 8.8E-04 9AE-02 <1

Chlordane 4.OE-04 NA 4.OE-04 7.5E-02 <1

DDE 9.5E-05 8.7E-03 8.8E-03 LIE-01 <1

DDT 2.OE-04 2.1 E-02 2AE-02 LIE-01 < I

DIMP 3.OE-03 NA 3.OE-03 1.9E+01 < I

Dieldrin 9.OE-04 2.7E-03 3.6E-03 2.7E-02 < I

Endrin L7E-04 1.2E-03 IAE-03 1.8E-03 < I

Fluoridel 4.3E-01 NA 4.3E-0 I 1.6E-01 3

Sulfatel 7.]E+01 NA 7.1 E+O I 9.4E+00 7

Mammals were conservatively assumed to ingest the same amount of water per unit body weight

as avian species.

Cannot be addressed for dietary intake because (1) chemical is a naturally occurring component

of diet or (2) cannot be modeled because of a lack of data.

< = less than

BAF = bioaccumulation factor

COC = chemical of concern

DDE = 2,2-Bis(p-chlorophenyl)-I,I-dichloroethene

DDT = 2,2-Bis(p-chlorophenyl)-1,1,1-trichloroethane

DIMP = diisopropy1methylphosphonate

HQ = hazard quotient

mg/kg-bw/day = milligrams per kilogram - body weight per day

NA = not applicable

TRV = toxicity reference value

20000,317.10 - OEA

0311111092
Table 5.3.1-5: Summary of Intakes From Zone 3 Soil, Surface Water, and Diet for the Prairie Dog

Soil and Total

Water Intake' Dietary Intake Intake TRV

COC (mR/kR-bw/day) (me/kg-bw/day) (mg/kg-bw/day) (mg/kg-bw/day) HO

Aldrin 4.IE-04 O.OE+00 4AE-04 2.7E-02 <1

Arsenic 8.8E-04 NA 8.8E-04 9AE-02 <1

Chlordane 1.5E-03 NA 1.5E-03 7.5E-02 <1

DDE 3AE-04 1.6E-03 1.9E-03 3.8E-02 <1

DDT 7.7E-04 2.6E-03 3AE-03 3.8E-02 <1

DIMP 3.OE-03 NA 3.OE-03 9.4E+00 <1

Dieldrin 3.5E-03 1.9E-03 5AE-03 2.7E-02 <1

Endrin 6.8E-04 4.OE-05 7.2E-04 1.8E-03 <1

Fluoride2 43E-01 NA 4.3E-01 1.6E-01 3

Sulfate2 7. 1 E+O I NA 7AE+01 9.4E+00 7

Mammals were conservatively assumed to ingest the same amount of water per unit body weight

as avian species.

2 Cannot be addressed for dietary intake because (1) chemical is a naturally occurring component

of diet or (2) cannot be modeled because of a lack of data.

< = less than

BAF = bioaccumulation factor

COC = chemical of concern

DDE = 2,2-Bis(p-chlorophenyl)-I,I-dichloroethene

DDT = 2,2-Bis(p-chlorophenyl)-1,1,1-trichloroethane

DIMP = diisopropy1methylphosphonate

HQ = hazard quotient

mg/kg-bw/day = milligrams per kilogram - body weight per day

NA = not applicable

TRV = toxicity reference value

20000,317.10(4) - OEA

0309111092
Table 6.3.2-1: Summary of Intakes From Zone 3 Sediment, Surface Water, and

Diet for the Great Blue Heron

Terrestrial

Sediment and Aquatic Dietary Total

Water Intake Dietary Intake Intake Intake TRV2

COC fmg/kjz-bw/dayj. (mg/kg-bw/day) fmir/kiz-bw/day) fmg/kjg-bw/daY) fmjz/kjr-bw/daY) HQ

Aldrin 6.8E-04 NA ME-05 7.2E-04 6.OE-02 <1

Arsenic 3.5E-05 3.OE-04 NA 3.3E-04 5.9E-02 <1

Chlordane 1.8E-06 NA NA 1.8E-06 8.8E-03 <1

DDE 5.3E-06 4.9E-03 1.9E-03 6.8E-03 5.5E-02 <1

DDT 8.5E-06 4.9E-03 4.3E-04 5.SE-03 5.5E-02 <1

DIMP 1.2E-04 NA NA 1.2E-04 ME-01 <1

Dieldrin 3.OE-06 3.3E-03 3.9E-04 3.7E-03 6.OE-02 <1

Endrin 9.6E-06 NA 4.3E-04 4AE-04 1.9E-02 <1

Fluoridel 1.7E-02 NA NA 1.7E-02 1.3E+00 <1

Sulfatel 2.8E+00 NA NA 2.8E+00 9.4E+00 <1

Cannot be addressed for dietary intake because (1) chemical is a naturally occurring component of diet or (2) cannot be

modeled because of a lack of data.

2 TRVs from Table 3.3.3- 1.

< = less than

BCF = bioconcentration factor

COC = chemical of concern

DDE = 2,2-Bis(p-chlorophenyl)-1,1-dichloroethene

DDT = 2,2-Bis(p-chlorophenyl)-1,1,1-trichloroethane

DIMP = diisopropy1methylphosphonate

HQ = hazard quotient

NA = not applicable

TRV = toxicity reference value

20000,317.10 - OEA

0309111092
Table 5.3.2-2: Summary of Intakes From Zone 3 Sediment, Surface Water, and

Diet for the Mallard Duck

Sediment and Total

Water Intake' Dietary Intake Intake TRV2

COC (mg/ka-bw/day) (mg/ka-bw/dav) (m9/kR-bwJdav) (me/kg-bw/day) HO

Aldrin 6.8E-04 O.OE+00 6.8E-04 4.OE-02 <1

Arsenic 8.8E-04 9.7E-02 9.7E-02 4.7E-01 <1

Chlordane 4.5E-05 NA 4.5E-05 6.3E+00 <1

DDE 1.3E-04 LOE-02 LOE-02 LOE-01 <1

DDT 2. 1 E-04 LOE-02 LOE-02 LOE-01 < I

DIMP 3.OE-03 NA 3.OE-03 LOE+O I < I

Dieldrin 7.5E-04 BAE-03 9.1E-03 4.OE-02 < I

Endrin 2AE-04 NA 2AE-04 1.5E-01 < I

Fluoridel 4.3E-01 NA 4.3E-0 I LIE+01 < I

Sulfatel 7.IE+01 NA 7.IE+01 9.4E+00 7

Cannot be addressed for dietary intake because (1) chemical is a naturally occurring component

of diet or (2) cannot be modeled because of a lack of data.

2 TRVs from Table 3.3.3-1.

< = less than

BCF bioconcentration factor

COC chemical of concern

DDE 2,2-Bis(p-chlorophenyl)-I,I-dichloroethene

DDT 2,2-Bis(p-chlorophenyl)- 1, 1, 1 -trichloroethane

DIMP = diisopropy1methylphosphonate

HQ = hazard quotient

NA = not applicable

TRV = toxicity reference value

20000,317.10(4) - OEA

0309111092
Table 5.3.4- 1: Summary of Chicken Hazard Quotient by Zone,

Offpost Operable Unit

Intake TRV

COC (mg/kg/day) (mg/kg/day) Hazard Ouotient

Soil Zones 1, 2, and 6

Aldrin/dieldrin 1.6 E-06 2.6 E-03 < I

DDE/DDT 3.6 E-06 5.5 E-02 < I

Endrin 3.3 E-07 5.2 E-03 < I

Indicates the ratio of intakes to TRVs for chickens.

< = less than

COC = chemical of concern

DDE = 2,2-Bis(p-chlorophenyl)-I,I-dichloroethene

DDT = 2,2-Bis(p-chlorophenyl)- 1, 1, 1 -trichloroethane

mg/kg/day = milligrams per kilogram per day

20000,317.10 - OEA

0306111092
RMAG 1041.21

2.OE-4 -

Dieldrin

1.8E-4 -

1.6E-4 - .... . . .

DBCP

-le 1.4E-4 -

cr 1.2E-4 - El Chloroform

(D 1.0E-4 -

0

.S 8.OE-5 Arsenic

6.OE-5 - 0 ........ ... ....... .. ..... ....... .... ..... . ..... 4.OE-5 - ....... .. ....... .. ....... .. Aldrin

2.OE-5 - ........ .. ....... .... ....... .. ....... ........ ....... .. .. .... .... ......

kittw O.OE+O

Zone I A Zone I B Zone I C Zone 2 Zone 3 Zone 4 Zone 6

Prepared for: Figure 4.1.1-1

Program Manager for OFFPOST OPERABLE UNIT COMBINED CARCINOGENIC RISKS (ALL Rocky Mountain Arsenal PATHWAYS) BY GROUNDWATER ZONE - RESIDENTIAL SCENARIOS

Commerce City, Colorado
RMAG 1041.19

2.0E_1

O.OE.O.0

00 otý

Prepared for: Figure 4.1.1-2

Program Manager for OFFPOST OPERABLE UNIT CHILD RESIDENT HAZARD INDICES Rocky Mountain Arsenal DESCRIBED FOR TOXIC CHEMICALS AND EXPOSURE PATHWAYS -

Commerce City, Colorado RESIDENTIAL SCENARIOS
RMAG 1041.17

1-8E-4

,.BE.4 1-6F--4

1.60 1-4E-4

1-2E-4

1 -OF--4

oo! 8.0F.6

0 6.OF.S

4.0p.5 6.0t

2.0p.S

O.OE.ýo

2.0E.5

0.

091

Prepared for: Figure 4.1.1-3

Program Manager for OFFPOST OPERABLE UNIT CONTRIBUTORS TO CARCINOGENIC RISKS - Rocky Mountain Arsenal RESIDENTIAL SCENARIO

Commerce Cky, Colorado
RMAG 1041.6

4.0E_5

gh 2.SE-5

2.0E-5 0

J.gh 1.5E.5 bo

0

0

5.0E.6 ... ..

-+0

Prepared for: Figure 4.1.1-4

Program Manager for CARCINOGENIC RISKS DESCRIBED BY CHEMICAL, MEDIUM, AND Rocky Mountain Arsenal EXPOSURE PATHWAY-ZONE 1 A, LIFETIME RURAL RESIDENT, RME

Commerce Chy, Colorado
RMAG 1041.4

4.0E-5

3.5e-5

.... . ... .. 3.OE.5

........ ... 2 .5E -5

dV ..... ..

0) 0 2.OE.5

'0 1.5e-5

0

5.()E.6

0-040

Prepared for: Figure 4.1.1-5

Program Manager for

Rocky Mountain Arsenal CARCINOGENIC RISKS DESCRIBED BY CHEMICAL, MEDIUM, AND

EXPOSURE PATHWAY-ZONE 1 B, LIFETIME RURAL RESIDENT, RME

Commerce City, Colorado
RMAG 1041.8

N

N 4.SE-S

N 4.OE N -S

N

N

\ I., '- ' 3.SE-S

N

N 3.0E-5

N

N

N 2.SE-S

d) ..... 2.OE-S

0 I.SE-S

... .... ...

-0'()E4-0

Prepared for: Figure 4.1.1-6

Program Manager for CARCINOGENIC RISKS DESCRIBED BY CHEMICAL, MEDIUM, AND Rocky Mountain Arsenal EXPOSURE PATHWAY-ZONE I C, LIFETIME RURAL RESIDENT, RME

Commerce City, Colorado
RMAG 104 1.10

0 .....

2.0 2,OE_S

0

06

.'CAP

05ý'- 'Coll

Prepared for: Figure 4.1.1-7

Program Manager for CARCINOGENIC RISKS DESCRIBED BY CHEMICAL, MEDIUM, AND Rocky Mountain Arsenal EXPOSRUE PATHWAY-ZONE 2, LIFETIME RURAL RESIDENT, RME

Commerce Chy, Colorado
RMAG 1041.12

I-2E-4

'OE-4

................ . .......

6.0E-5

4.0E-5

2.oE.5

0-0E+0

'egoASPzeý

Prepared for: Figure 4.1.1-8

Program Manager for

Rocky Mountain Arsenal CARCINOGENIC RISKS DESCRIBED BY CHEMICAL, MEDIUM, AND

EXPOSURE PATHWAY-ZONE 3, LIFETIME URBAN RESIDENT, RME

Commerce City, Colorado
RMAG 1041.14

4.0e.5

3* 3.0t.5

2.0E's

....... ...

Prepared for: Figure 4.1.1-9

Program Manager for CARCINOGENIC RISKS DESCRIBED BY CHEMICAL, MEDIUM, AND Rocky Mountain Arsenal EXPOSURE PATHEWAY-ZONE 4, LIFETIME URBAN RESIDENT, RME

Commerce City, Colorado
RMAG 1041

1.1f.5

0

0 

4.0E-6

2.oee

Prepared for: Figure 4.1.1-10

Program Manager for CARCINOGENIC RISKS DESCRIBED BY CHEMICAL, MEDIUM, AND Rocky Mountain Arsenal EXPOSURE PATHWAY-ZONE 5, COMMERCIAIJINDUSTRIAL, RME

Commerce City, Colorado
RMAG 1041.16

N

N 

4.0e.6

Prepared for: Figure 4.1.1-11

Program Manager for CARCINOGENIC RISKS DESCRIBED BY CHEMICAL, MEDIUM, AND Rocky Mountain Arsenal EXPOSURE PATHWAY-ZONE 6, LIFETIME RURAL RESIDENT, RME

Commerce Cfty, Colorado
RMAG 1041.22

4-

3-

X

"2C(% 2

..........

0

1A 1B 1C 2 3 4 6

Zone

Explanation

Other

Dieldrin

Prepared for: Figure 4.1.1-12

Program Manager for CHILD ACUTE LIVER HAZARD INDICES Rocky Mountain Arsenal

Commerce City, Colorado
RMAG 1041.23

5 - ...................

.............. .. ................. .............. .. ................. .............. .. .................

.............. .. .................

.............. .. ................. .............. .. .............. .................

................... .............. .. X ................. .............. .. (D 4- .................

.............. .. ............. ... S .............. ................... .............. .. .............. ................. .. ............ ........... cd .............. ................. ................... .............. .. 3 - .............. ................. ............ .. .............. ............. ............. ... ... .. ... .............. ............. ... .. .............. .. .............. .. .............. ................ .. .............. ............. ... .. (D ................. ............. ... > ............ ............ .............. .. .............. .. ............. ............. .............. ............. ... ..

2 - ................. ............. .. .............. 

................. ............. ... .. ..... .... . ............... .............. ............. .. .. ........ ............. . ............. ... .. ......... .. ........... .. .............. ......... .. . ......... .............. ......... .. ............ ............ X . ......... ......... ..... ....... .............. ............. .. .. ........ -------- ............. .. .............. .. CO ............. ..

.............

0-10 1 1 1

1B 2 3 4

Zone Explanation

Ej maximum

ES minimum

Prepared for: Figure 4.1.1-13

Program Manager for SUBCHRONIC CHILD LIVER HAZARD INDICES, MAXIMUM AND MINIMUM Rocky Mountain Arsenal OFRANGE

Commerce Chy, Colorado
RMAG 1041.2

9.OE-2

B.OE-2

7.OE-2 10.2

6.OE-2

5.0E.2

d)

$0 4.OE.2

3.OE.2

2.OE.2

0-040

O.OE40

Prepared for: Figure 4.2.1 -1

Program Manager for NONCARCINOGENIC HAZARD INDICES ZONE 5; ADULT Rocky Mountain Arsenal COMMERCIAIJINDUSTRIAL; CHRONIC RME

Commerce City, Colorado
RMAI 1007.1

HAI"

HA10648 EXPLANATION HAI

HAI0W8

104th Ave HA12546 Terrestrial Biota Sampling Locations ................ ................................. ......................... ................................................ ..... ... ...................................... Field Mice

Prarle Dogs

Grasshoppers

Earthworms

Chicken Sampling Locations

Chicken Egg

Chicken Liver

Chicken FatfSkin

0 Chicken Muscle

14 Aquatic Biota Sampling Locations

L3 + Fish

0: W Crayfish

Algae

ighway 0 650 Cow Sampling Locations

OHA10498 Cow Milk Scale in feet 0 Cow Fat

Cow Brain

Cow Muscle HAI OW + HA10619 HA12508 MAII0629 Cow Liver HAI 2518 HA 25M ....................... .............. 9 C ow Kidney

Pheasant Sampling Locations ý First Creek Creelc Pheasant Liver !Impoundment HA1050"'. +HAO048A Pheasant Flesh HAIMN

HA125M +iVM936A Sample is a Duplicate

13 Section Number

A HAI2558L

A HA1255BF 0 KA100AM

A (HA12558FO) 0 HAI0106kk 12

0 HAI 01 2BF

13 HA1013BF

HAI0366 .. ..

HA10378:

In HA103M

HA,03913:

woma

JHAI0W8

HAI 0518

HA12468

HA OUR OHA10178P AR412568L undary HAI ýA 96t -h Ave A.HAI2578L.

........... ý HAII= ............... 0 9 4M R ......... .......... A M 12W F ..... ....... ..................... HA12496 WNW 23 111 20

H A I246B ......................

ý/WEr-S

NDEX

Prepared for: Figure 5.1.1-1

Program Manager for OFFPOST OPERABLE UNIT BIOTA SAMPLING LOCATIONS Rocky Mountain Arsenal

Commerce City, Colorado
RMAI 1007.3

EXPLANATION

B Buildings, fences. parking

areas

100 so 0 100

Scale in feet '000.. 

T Trash dumps, small

abandoned dumps

r= FF Fallow Field; Not planted for at

FF

0.- least a season

B

PD Prairie dog colonies

. .. .. . ... (forbs and short grasses)

104th Avenue .. .. . .. . .. M SB Shelterbelts, ornamental

pants/treesaroun res ences

17777771 WF Weedy forbs

FU A

PPF Planted, plowed field; winter ;%;% ED grain crop % . . .

1 *6 GWF Grasses, weedy forbs, R. ..........

. . .PPF. R. PFF Plowed, fallow field

........... . .......................... ...... ....... 2 '

ý.-W F: ...........................

.......................... . HCR Horse and cattle range

..... ......... ............ ....... ........... CTM Cattail marsh .. . ............. .. .. . .... .. ........... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ----- ýý.RRRRM 0 K:ý:: .. . .. . .. . .. . .. ..r. TG-W Tall grasses, forbs (wetlands) . .. . .. . .. . ...... UUMUUUUM . .%. E ] .:.:::GWF ..... . . . . . . . . . . . . . ..

. . . PPF ..... . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . 3%4`1 . . . .

......

.............. CTM . . . . . . . . . . . . . . . . . . . . . :dWF: %

Rocky Mountain Amenal

Prepared for: Figure 5.1.1-2

Program Manager for HABITAT MAP FOR FIRST CREEK PORTION OF Rocky Mountain Arsenal OFFPOST OPERABLE UNIT

Commerce City, Colorado
HMA1 1191

Secondary Secondary Secondary Exposure Exposure Receptors Quantified?

Source Release Transport Media Routes

Mechanism Process

From Offsite Groundwater Pumpin Ingestion Livestock Yes,

Onpost Groundwater to Flow, Surface Discharge Water Sorption9 Groun dwater E R Plant Uptake Crops Yes

Fugitive -Ingestion Livestock Yes From Offsite DustDeposition Soil Dermal Crops No Onpost Soils tr m H Inhalation Terrestrial Wildlife No

Y Ingestion m* Livestock Yes

From Offsite Deposition Plant Uptake --)o Crops Yes

Onpost -30 Surface Water Runoff Sorption Surface Water Direct Contact Aquatic Life Yes Sediment Ingestion Terrestrial Wildlife Yes

Ingestion Aquatic Life Yes

),P Sediment

Dermal Terrestrial Wildlife Yes

iota Terrestrial Wildlife Yes

" Plants Ingestion

" Animals Aquatic Life Yes

Prepared for: Figure 5.2.2-1

Program Manager for ECOLOGICAL SITE CONCEPTUAL MODEL OFFPOST OPERABLE UNIT Rocky Mountain Arsenal

Commerce City, Colorado
RMA1 1105

Great Horned Owls -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -

American Kestrels

)o Bald Eagles .K -- - -- -

... ............................ A

.......... .........

Plants

rm rass oDo#.

Surface Wate .r

EXPLANATION

a

I, oud web pathway

Surface water ingestion pathway

-- - - - - Soil ingestion pathway

Residue data frorn RI addendum

Prepared for: Figure 5.2.5.1 -1

Program Manager for OFFPOST OPERABLE UNIT TERRESTRIAL FOOD WEB Rocky Mountain Arsenal

Commerce Chy, Colorado
RMA1 1106

r -- -- -- - Great Blue Bald Eagles

Herons

Mallards

Ex, IBM A,

nt.

.......... ....... , "T .. .. ...... ............. ...... . ...... ...

.. (-hp

17 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

-- -- -- -- -- -- -- -- -- -- -- -- -

- -- -- -- - -- -- -- -- -- - - -- -- -- -- -- -- -- -- -

EXPLANATION

Food web pathway

-- - - - - Surface water ingestion pathway

Sediment ingestion pathway

Residue data from RI addendum

Prepared for: Figure 5.2.5.3-1

Program Manager for

Rocky Mountain Arsenal OFFPOST OPERABLE UNIT AQUATIC FOOD WEB

Commerce City, Colorado
RMAI 110'

-< --- - ------- - - - - - ------- - ------------

*:--'M V f : 

..............

.......... ....

..... .....

Crops

... .... ........... .......

XX2. M ..........

EXPLANATION

Food wi-b pathway

Sur-face water ingestion pathway

- - - - - - Soi! ingestion pathway

..................... Groundwater ingestion pathway

Residue data from RI addendum

Prepared for: Figure 5.2.6.5-1

Program Manager for

Rocky Mountain Arsenal OFFPOST OPERABLE UNIT AGRICULTURAL FOOD WEB

Commerce City, Colorado