circle c landfill 2009 annual report for ... c landfill 2009 annual report for groundwater and...

CIRCLE C LANDFILL

2009 ANNUAL REPORT FOR

GROUNDWATER AND SURFACE WATER MONITORING

Prepared for

Circle C Corporation

February 16, 2009

Prepared by

Bright Fields Groundwater, Inc.

3800 NE 399th Street La Center, Washington 98629

Phone: (360) 263-6307 Internet: [email protected]

C:\BF Groundwater\Circle C\Documents\Annual Report\1996 to 2013\Circle C Ann 2009-Report.doc 3/1/2017

i Bright Fields Groundwater, Inc.

CONTENTS

1 INTRODUCTION 1-1

2 GROUNDWATER LEVELS AND FLOW DIRECTIONS 2-1

3 GROUNDWATER QUALITY 3-1 3.1 Evaluation Methodology 3-1 3.2 Findings 3-3

4 SURFACE WATER QUALITY 4-1

5 UNDERDRAIN IRRIGATION AREA 5-1 5.1 Soil Moisture 5-1 5.2 Soil Quality 5-2

6 LANDFILL GAS MONITORING 6-1

7 SUMMARY AND DISCUSSION 7-1

LIMITATIONS

REFERENCES

APPENDIX A WATER LEVEL DATA AND CONTOUR PLOT

APPENDIX B GROUNDWATER QUALITY DATA, STATISTICAL ANALYSES, AND TREND PLOTS

APPENDIX C SURFACE WATER QUALITY DATA AND TREND PLOTS

APPENDIX D UNDERDRAIN IRRIGATION AREA FIGURE, SOIL MOISTURE QUALITY, AND SOIL QUALITY

APPENDIX E LANDFILL GAS MONITORING LOCATION MAP AND MEASUREMENTS

APPENDIX F MARCH SAMPLING AND DATA VALIDATION MEMORANDA AND LABORATORY ANALYTICAL REPORT

APPENDIX G SEPTEMBER SAMPLING AND DATA VALIDATION MEMORANDA AND LABORATORY ANALYTICAL REPORT


ii Bright Fields Groundwater, Inc.

TABLES AND ILLUSTRATION Following Text

Tables

1 Parameters Exceeding Prediction Limits in 2003 to 2009

Figures

1 Site Location Map Appendix A - Water Table Contour Plot Appendix D - Underdrain Irrigation Area Schematic Appendix E - Gas Monitoring Location Map


1-1 Bright Fields Groundwater, Inc.

1 INTRODUCTION

This report constitutes the 2009 Annual Report for groundwater and surface water monitoring at the Circle C Landfill. Sampling in the underdrain irrigation area and landfill gas monitoring are also described. This report is submitted in compliance with the Washington Minimum Functional Standards for Solid Waste Handling (MFS). The groundwater monitoring requirements are specified in WAC 173-304-490, as amended by the jurisdictional health department. In this case, the monitoring program has been amended by the addition of surface water sampling, monitoring of the underdrain irrigation area and use of a nonstandard analytical program. The monitoring frequency has also been reduced to semi-annual from quarterly. In this report, the groundwater flow rate and direction in the shallow aquifer are estimated and statistical analyses of the analytical data are presented.

This report is divided into seven sections as follows:

Section 1: Introduction Section 2: Groundwater Levels and Flow Direction Section 3: Groundwater Quality Section 4: Surface Water Quality Section 5: Underdrain Irrigation Area Section 6: Landfill Gas Monitoring Section 7: Summary and Discussion

The Circle C Landfill is located at 31313 Paradise Park Road, Ridgefield, Washington (Figure 1). Groundwater and surface water have been monitored since 1990. Sampling of soil moisture and soil in the underdrain irrigation area were added in 1993. Monitoring of landfill gas was added to the sampling program in September 1995.

In February 1992, groundwater monitoring was reduced to monitoring of the shallow aquifer only, except measurement of water levels in four deep aquifer wells. On March 15, 1993, the Southwest Washington Health District (SWHD) approved the reduction of the frequency of groundwater and surface water sampling to semiannual. The Washington Department of Ecology (Ecology) concurred with SWHD's approval. The first sampling event of this schedule was conducted in December 1993. Subsequent sampling has been conducted during March and September. In 2003 the Clark County Health Department (CCHD, successor to the SWHD), with the concurrence of Ecology, approved the focusing of the



analytical program on parameters identified from the more than 10 years of site specific data as most indicative of potential landfill impacts. The modified analytical program is described in Sections 3, 4, and 5. The reporting requirement was also modified to consolidate the transmittal of the data with the annual report. Significant changes in water quality parameters or gas migration detected by the sampling events are to be reported to CCHD as soon as practical.

The water level data, water quality data, statistical analyses, water quality trend plots, underdrain irrigation area data, landfill gas monitoring data, sampling memoranda, and the data validation memoranda with the laboratory data reports are included in appendices. Appendix A includes water level measurements and elevations, groundwater level hydrographs, and the water level contour plot. Appendix B includes groundwater quality data and trend plots. Appendix C includes the surface water quality data and trend plots. Appendix D includes soil moisture quality and soil quality data for the underdrain irrigation area. Appendix E includes landfill gas monitoring data. Appendix F includes the March sampling and data validation memoranda and laboratory analytical report. Appendix G includes the September sampling and data validation memoranda and laboratory analytical report.



2 GROUNDWATER LEVELS AND FLOW DIRECTIONS

Shallow Aquifer

The shallow aquifer monitored at the site was described as a water table aquifer in the 1990 Annual Report prepared by Russ Fetrow Engineering, Inc. (RFEI). The water table contour was shown to be a subdued representation of the ground surface topography in the 1990 Annual Report using a greater number of monitoring points than are currently available. The currently available monitoring points (designated MW-1, MW-2, MW-4, and MW-8) do not provide adequate data to prepare contour plots.

A contour plot of the shallow aquifer for September 16, 1991 (included in Appendix A) was prepared using measurements in the monitoring wells and an assumed similarity to the ground surface topography. Water levels measured in the shallow aquifer during 2009 are in a generally similar pattern to those used to prepare this plot. Water levels rose between 1996 and 1999 and fell between 2000 and 2003, stabilized or rose slightly from 2004 through 2007, but appear to have resumed a decline in late 2008 and 2009. The rise in water levels was likely due to the higher rainfall experienced during that period and the fall of water levels was likely due to the relatively dry conditions experienced over that period. The dry conditions also muted the typical seasonal fluctuation of water levels. The seasonal fluctuations of groundwater levels at MW-2 are typically much greater than at the other wells, except during dry winters when little or no fluctuation can be observed. This is likely caused by the shallower groundwater levels at this location which tend to show a larger response to seasonal changes in recharge.

Although the groundwater flow pattern appears to be generally similar to that shown on the contour plot, the March water levels at MW-4 and MW-8 suggest a slight westward component to flow in the winter. This is similar to conditions observed in previous years. A hydrograph of the shallow aquifer water level data is included in Appendix A.

The water level contours presented on the September 16, 1991 plot indicate that well MW-2 is downgradient from the irrigation area and MW-4 is downgradient of the landfill. MW-1 and MW-8 are up- or cross-gradient from the landfill and represent background conditions.

The hydraulic gradient in the shallow aquifer cannot be estimated directly from the measured data. Using the assumption that the water table is a subdued reflection of the surface topography (Freeze and Cherry, 1979), a conservative gradient (i.e., high) is



estimated to be the same as the topography. The gradient down slope from MW-2 is estimated to be 0.2 ft/ft and from MW-4 is estimated at 0.031 ft/ft. Using the hydraulic conductivity of 1x10-4 cm/sec and porosity of 0.35 included in the 1990 Annual Report, the linear groundwater velocity is estimated to be 59 ft/year downgradient of MW-2 and 9.2 ft/year from MW-4.

Deep Aquifer

Water levels were measured in the four deep aquifer monitoring wells (monitoring wells MW-3, MW-5, MW-6, and MW-7) in March and September 2009. Water levels have declined 5 to 6 feet since 1997. The steady decline in water level elevations was interrupted by a slight recovery in late 2003 and early 2004 but resumed in 2005 albeit at a slower rate. The March 2009 measurements show a larger drop from the recent trend although the September data shows a slight recovery from this drop. This decline is likely the result of groundwater pumping in the area and not related to the landfill. Additionally, water levels at MW-3 continued the trend that began in 1996 of being about a foot higher than water levels at MW-5 and MW-6. Prior to 1996, water levels, when reliably measured, were generally within one half of a foot at these wells. A hydrograph of the deep aquifer data is provided in Appendix A.

The previously reported northwesterly flow direction in the deep aquifer is not contradicted by the 2009 data, although the higher water levels at MW-3 suggest the direction may have shifted somewhat to the west.



3 GROUNDWATER QUALITY

Groundwater samples were collected and analyzed from four monitoring wells in the shallow aquifer (MW-1, MW-2, MW-4, and MW-8) in March and September 2009. The locations of the monitoring wells are shown on the water table contour plot included in Appendix A. Tables showing the groundwater analytical data and statistics are included in Appendix B. The analytical program was modified in 2003 to focus on parameters considered to be of concern based on the more than ten years of site specific data. The groundwater samples were analyzed for chloride, sulfate, nitrate, manganese, TOC, and COD. The sample collected from MW-4 in September was also analyzed for arsenic, chromium, selenium, and mercury. A sample was collected in September from the underdrain and analyzed for the same parameters as for the MW-4 sample. A sampling procedure memorandum was prepared following each sampling and the water quality data summary tables were updated following validation of the data. The sampling and data validation memoranda and the laboratory analytical report for March are included in Appendix F and for September in Appendix G.

3.1 Evaluation Methodology

The procedures used to evaluate the data include four major steps. The first step is to establish the locations that define background groundwater conditions. The second step is to calculate statistical parameters for analytical parameter at each location. The third step is to determine, define procedures for, and implement a statistical method to compare downgradient groundwater quality conditions with background. The fourth step is to compare the detected concentrations with appropriate promulgated criteria and historic data.

Background groundwater quality is represented by samples from wells MW-1 and MW-8. The background locations were determined as described in Section 2.

The following statistical parameters were calculated for the groundwater quality data collected from 1991 to 2009:

Maximum Minimum Average Standard deviation Variance Coefficient of variation



Standard error These statistics are shown on the data tables included in Appendix B.

The following criteria were used to guide selection of the statistical method used to compare background with downgradient conditions:

A sound technical basis that considered the hydrogeology and distribution of lithologies at the site

A desire to keep false positives and negatives to a minimum The ease of implementation of the detection monitoring program The ease of the review of the results Applicability of the method to each constituent at each well

A non-parametric prediction limit was selected as the statistical procedure used to evaluate the groundwater quality results. The non-parametric prediction limit method relies on the assumption that the data for each constituent at the background locations is distributed the same as at the downgradient locations (i.e. represents the natural variability of groundwater conditions). The potential for false positives or negatives was reduced by evaluating trends in the data to determine if a data point is representative (i.e., within the normal range of values or part of a trend). If a data point was clearly not representative (i.e., an outlier), it was not used in the analysis. The highest concentration in the reduced background data set for each parameter was selected as the prediction limit. The selected prediction limits are shown on Table 1.

Prediction limits were established for eleven parameters. In 2003 iron, zinc, ammonia, and nitrite were dropped from the analytical program and therefore are no longer compared to the established prediction limit. The manganese prediction limit was revised in 2003 to the maximum value detected at the background locations between 1997 and 2003. Prior to 1997 the manganese data shows significant variability which may have elevated the prediction limit relative to the more stable results determined after 1996. Manganese concentrations in the database did not exceed the new manganese prediction limit.

The data generated in 2009 were compared to the prediction limits for the following parameters:

manganese chloride chemical oxygen demand nitrate sulfate total organic carbon specific conductance

Downgradient data for each parameter were compared point by point to the prediction limit. A datum above a prediction limit was confirmed by a check for representativeness of that



data point. A data point that was clearly an outlier was not considered to represent downgradient conditions. The downgradient concentrations that exceeded the prediction limit between 2003 and 2009 are shown on Table 1.

Trend plots were prepared and reviewed to evaluate whether concentrations above the prediction limits represent degrading water quality. Trend plots are included in Appendix B.

3.2 Findings

General. The number of parameters with results at levels exceeding a respective prediction limit in 2009 is small, just 3 of 28. This includes COD in both samples and TOC in the sample collected at MW-4 in March. This is the same as last year and a similar or lower number to previous years. The September 2009 COD concentration at MW-4 was a typical value indicating that the unusually high September 2007 result is likely an outlier data point and has been identified as such in the database.

It should be noted that in 2003 the prediction limit evaluation was reduced along with the analytical program to focus on parameters that are most likely to indicate impacts to groundwater quality caused by the Circle C landfill therefore the prediction limit evaluation would show a higher proportion of exceeding values than in the past when more parameters were evaluated. Trend plots of the data do not show a clear overall trend in water quality. This supports the conclusion that landfill impacts on groundwater quality, if present, are small. Trend plots are included in Appendix B.

Comparison with Promulgated Criteria. Concentrations detected in 2009 do not exceed Washington primary contaminant levels for groundwater quality (WAC 173-200-040) except the very low arsenic standard at MW-4. The arsenic concentration at MW-4 was lower than the federal drinking water standard of 10 ug/l and concentrations commonly detected in this region. Mercury was not detected at or above the standard of 0.002 mg/l in the September 2009 MW-4 sample or in the underdrain sample.

The secondary contaminant level for groundwater quality was exceeded for manganese which is common in the site area. Iron, which was previous detected above a secondary contaminant level, was dropped from the analytical program in 2003.

The concentrations that have exceeded primary and secondary contaminant levels are common in the site area and do not appear to be related to the landfill.

Comparison with Past Data. The data generated in 2009 were generally similar to past data. The manganese data appear to have stabilized at low levels near or below those detected at the background well.

Chloride concentrations in 2009 appear to have stable trends at MW-4 and MW-8 after following a slightly declining trend from 2004 to 2008, although concentrations are quite low. Sulfate concentrations at MW-8 appear to have stabilized after following a slightly



declining trend that began in 1995. At MW-4, sulfate concentrations experienced somewhat less variability than in previous years.

COD concentrations at MW-4 were at concentrations similar to those measured since 2001. The high concentration reported in September 2007 was not repeated and may be an outlier data point. This datum has been identified as an outlier in the database. Without the September 2007 datum, COD concentrations at this well appear to fluctuate seasonally at similar levels since 2003. The TOC data shows generally low or non-detected concentrations at wells MW-1, MW-2 and MW-8 and slightly lower than typical concentrations at MW-4. The high concentration in March 2008 at MW-4 appears to have been an outlier datum and has been identified as such in the database. Most of the similar spikes in 2003, 2006 and 2007 have been identified as outliers. Nitrate concentrations appear to be relatively stable and low with background concentrations generally higher than downgradient concentrations.

pH was above 6 in 2009 at all wells continuing a slight rise that began in September 2008. The specific conductance appears to have declined in recent years although the trend is obscured by a meter failure several years ago and a replacement meter that may be less accurate in this portion of the calibration range.

Volatile Organic Compounds. VOCs were dropped from the analytical program in 2003.



4 SURFACE WATER QUALITY

Surface water samples were collected and analyzed in March and September 2009. Samples were collected at established locations on McCormick Creek upstream and downstream of the landfill. The analytical program was modified in 2003 to focus on parameters considered to be of concern based on the more than ten years of site specific data. The surface water samples were analyzed for chloride, sulfate, nitrate, manganese, TOC, COD and turbidity. Tables showing the groundwater analytical data and statistics are included in Appendix C. Trend plots for selected parameters were generated and are also included in Appendix C. A sampling procedure memorandum was prepared following each sampling and the water quality data summary tables were updated following validation of the data. The sampling and data validation memoranda and the laboratory analytical report for March are included in Appendix F and for September in Appendix G.

As in previous years, concentrations of individual parameters were generally lower in the downstream samples, indicating that the landfill has not affected surface water quality.

Sampling of the pretreated leachate was suspended in 1999 after the City of Vancouver dropped the requirement.



5 UNDERDRAIN IRRIGATION AREA

Circle C installed an irrigation system in 1993 on a field southeast of the landfill. Water collected in the underdrain is spray-irrigated by this system. Irrigation began in February 1993. Soil moisture and soil in the irrigation area were sampled during 2009 to monitor irrigation activities.

5.1 Soil Moisture

Four soil moisture lysimeters were installed in and near the irrigation field by Brown and Caldwell in 1993. A figure provided by Brown and Caldwell is presented in Appendix D and shows the locations of the lysimeters. The lysimeters are designated L-1 through L-4 with L-4 representing background conditions. The samples were analyzed for parameters established by Brown and Caldwell depending on the sufficiency of the amount of sample collected. In 2003 the analytical program was revised to include chloride, nitrate, total manganese, pH, and specific conductance. Iron was dropped from the program.

Quarterly sampling of the lysimeters was initiated in June 1993 (second quarter). This was reduced to semiannual sampling after the March 1994 event. Dry conditions during September sampling events have consistently prevented sampling of several lysimeters. During the September 2009 event, only one partial sample could be collected from the lysimeters. Appendix D includes the soil moisture quality data for the lysimeters.

The concentrations detected in 2009 were generally within the historically measured range of values. In March concentrations of chloride at L-1, L-2 and L-3 were somewhat higher than at the background location, although concentrations were low. Chloride was not detected in the only September sample collected (L-2). Chloride concentrations at each lysimeter show substantial variability in the data. Nitrate at L-2 was high in September relative to most results in the database, although the September 2009 concentration was lower than in 2008.

Managanese in the L-1 March sample was the highest recorded at this location and also higher than in the background sample.



5.2 Soil Quality

The irrigation area soil monitoring program was modified in 2003. The analytical program was reduced to arsenic, chromium, selenium, mercury, pH, nitrate, phosphorus, cation exchange capacity and organic matter. The metals analyses were revised to focus on metals detected in the underdrain and to determine total metals concentrations rather than DTPA extractable metals concentrations which were previously analyzed. The change in metals analyses necessitated collection of a background sample to determine local background total metals concentrations. A composite background sample was collected west of the irrigation area in 2003 using procedures similar to those used to collect the irrigation area sample. This area was selected as representative of background conditions because it is contiguous with the irrigation area, has similar vegetation, and is unlikely to have been affected by the irrigation. The detected background metals concentrations are generally consistent with the natural background soil metals concentrations in Clark County determined by Ecology (San Juan, 1994).

The 2009 composite soil sample from the irrigation area was collected from six locations in the irrigation field in September 2009. The irrigation area sample was analyzed for the parameters listed above. Appendix D includes analytical soil data for an initial sampling by Brown and Caldwell in February 1993, the new total metals background sample, and the annual sampling events conducted in September of each year.

The analytical results in 2009 were generally similar to previous years and the background levels. pH was at a somewhat higher level in the past although at a similar level to the last several years. Organic matter was similar to the last several years and continues to be somewhat higher than the background measurement. Cation exchange capacity, although somewhat variable, appears to measure within a moderate range that is similar to the background level.

Metals concentrations in the irrigation area soil were generally somewhat lower than the background data or not detected. The differences are considered to be within typical soil variability and will be evaluated annually. Arsenic and chromium were detected below the background concentrations and show a declining trend over the last several years. Mercury and selenium were not detected in 2009.



6 LANDFILL GAS MONITORING

In September 1995, semi-annual monitoring of landfill gas was added to the monitoring program. This monitoring was added in compliance with WAC 173-304-460. According to Circle C’s Closure/Post-Closure Plan for the landfill “sites will be monitored for explosive gases and oxygen levels using portable gas detection equipment such as Gas-Tech Model 1939 OX or equivalent.” The Closure/Post-Closure Plan further states that monitoring of landfill gas is to occur at 16 locations including a mobile trailer located north of the landfill which was removed in 1997. The job trailer located near the office was added to the monitoring program after it was installed. Additionally, both ends of the culverts identified in the Plan are monitored for completeness. Currently, the following locations are monitored:

Eight gas monitoring probes located along the perimeter of the landfill The leachate manhole Both ends of the drainage culverts which enter and exit the pond south of the

landfill property The Circle C office The Circle C shop The job trailer located near the office

The monitoring probes were installed by RFEI in October 1990.

A figure showing the gas monitoring locations is included in Appendix E. Appendix E also includes a summary of monitoring data from 2000 through 2009. The data show that the requirements of Chapter 173-304 WAC have been met at the landfill.

Landfill gas was not detected in the buildings or most of the gas probes during 2009. Gas was detected at low LEL concentrations at one end of each culvert in March and at the pond culvert outlet in September. Gas was not detected at the leachate manhole in March but at greater than 100% LEL in September. Gas was detected at 28% LEL at Gas Probe 7 in March but not in September. Gas has occasionally been detected at lower concentrations at this location. Gas detections and concentrations are below the requirements of Chapter 173-304 WAC.



7 SUMMARY AND DISCUSSION

This report has been prepared to comply with the annual reporting requirements for water quality set forth in the MFS for landfills in Washington. The post-closure analytical and reporting requirements for the Circle C Landfill were modified in 2003 with the concurrence of the CCHD and Ecology. The analytical program was reduced to focus on parameters considered to be site specific indicators of potential impacts from the landfill. The parameters were selected based on the more than 10 years of available data. Groundwater, surface water, and the underdrain irrigation area analytical programs were reduced. The irrigation area soil analytical program was also modified to change the metals analysis from DTPA extractable metals to total metals. This necessitated collection of a background sample which was analyzed for the selected metals.

The reporting requirements were modified in 2003 to consolidate the transmittal of sampling and data validation memoranda and the laboratory analytical reports with the annual report. Therefore data transmittals are not submitted separately after each sampling event. However, the analytical data are validated and entered into the database as soon as practical after sample analysis. A preliminary review of the data is conducted after each sampling event. The CCHD will be notified if a significant increase in groundwater or surface water concentrations or gas migration is observed in the semiannual data.

The focusing of the analytical program on the parameters considered to be the most likely to show impacts from the Circle C Landfill could cause the appearance of an increase in the impacts from the landfill when none has occurred. For example the number of data evaluated against prediction limits was reduced from 44 to 28 with all the parameters most likely to exceed a prediction limit retained in the program. Therefore the proportion of parameters exceeding a prediction limit may be higher than in the past when the actually number may be lower. This must be considered when evaluating the data. In 2009 only three data exceeded a prediction limit which is the same as the previous year and appears to continue the trend of fewer parameters exceeding prediction limits downgradient of the landfill (see Table 1). No parameters were detected above a prediction limit downgradient of the irrigation area.

Groundwater Levels and Flow

Groundwater in the shallow aquifer appears to flow north from the landfill at approximately 9.2 feet/year. This flow rate was estimated based on the available data



and hydrogeologic assumptions in 1991. Current data appears to be similar but is not adequate to reevaluate these parameters. The downgradient wells are located north of the landfill (MW-4) and east of the irrigation area (MW-2).

Groundwater Quality

In groundwater, the data support the conclusion that landfill impacts, if present, are small and generally stable or declining. Concentrations above a parameter prediction limit were determined for COD during both sampling events and for TOC only during the March event at the location downgradient of the landfill (MW-4). This includes only 3 of the 28 data points evaluated and is less than or similar to previous years (see Table 1).

Trend plots indicate that manganese continues to have concentrations near or below those detected at the background well. Chloride concentrations in all wells in 2009 were consistent with the long term typical concentrations. The declining trend that began in 2004 at MW-4 and MW-8 appears to have stabilized in 2009 at low concentrations. Sulfate at MW-8 appears to have stabilized after following a declining trend that began in 1995. Sulfate at MW-4 continued to fluctuate in 2009 although with somewhat lower amplitude.

Low COD concentrations at MW-4, although somewhat elevated from background, appear to be generally declining or stable. The September 2007 datum, which was significantly higher than is typical, has been designated an outlier. The TOC data shows generally low or non-detected concentrations at wells MW-1, MW-2 and MW-8 and slightly lower than typical concentrations at MW-4. The high concentration detected in March 2008 at MW-4 was not repeated in 2009 but appears to be similar to spikes in 2003, 2006 and 2007 and appears to be an outlier. pH was above 6 at each well in 2009 continuing a slight rise that began in September 2008. This reverses a declining trend observed since 2003 at all wells. The specific conductance appears to have declined in recent years although the trend is obscured by a meter failure several years ago and a replacement meter that may be less accurate in this portion of the calibration range.

Concentrations of the parameters evaluated in the groundwater samples are low and well below applicable primary groundwater quality criteria, except for arsenic. Arsenic was detected at MW-4 at a concentration similar to previous detections and well below the federal drinking water standard, although above the Washington health based drinking water standard. Naturally occurring arsenic is common in this area. Manganese exceeded a Washington secondary drinking water standard. Mercury was not detected in 2009 but chromium was detected in groundwater at a concentration below the standard.

Surface Water Quality

In surface water, concentrations of individual constituents were generally lower in the downstream samples when compared to the upstream samples. Trend plots indicate



seasonal fluctuations in surface water quality. Because concentrations are generally lower in the downstream samples, the landfill does not appear to affect surface water quality.

Underdrain Irrigation Area

The 2009 monitoring of the underdrain irrigation area indicates that the area is functioning as designed. Significant concentrations of the parameters monitored do not appear to be passing the root zone in soil moisture or accumulating in the soil. Chloride was somewhat above background in March but not detected in the limited September data. The March chloride concentrations were low and within the range of variability. Manganese in one March sample was elevated and will be reviewed in 2010. The analytical results show that the soil metals in the irrigation area are comparable to the background location and the natural background concentrations as determined by Ecology (San Juan, 1994).

Landfill Gas

Monitoring of landfill gas was initiated in September 1995. Eight on-site gas probes and eight other locations were monitored during 2009. The results demonstrate that the landfill met the applicable landfill gas criteria. Gas was detected in the leachate manhole, one gas probe, and at one end of each monitored culvert at levels below the standards.



LIMITATIONS

The services described in this report were performed consistent with generally accepted professional consulting principles and practices. No other warranty, express or implied, is made. These services were performed consistent with our agreement with our client. This report is solely for the use and information of our client unless otherwise noted. Any reliance on this report by a third party is at such party's sole risk.

Opinions and recommendations contained in this report apply to conditions existing when services were performed and are intended only for the client, purposes, locations, time frames, and project parameters indicated. We are not responsible for the impacts of any changes in environmental standards, practices, or regulations subsequent to performance of services. We do not warrant the accuracy of information supplied by others, nor the use of segregated portions of this report.



REFERENCES

EMCON, 1991. Circle C Landfill 1991 Annual Report for Ground and Surface Water Monitoring. March 1, 1991.




Fetrow Engineering, Inc., 1990. 1990 Annual Report on Groundwater and Surface Water Monitoring at the Circle C Landfill Clark County, Washington. February 1991

Freeze,R.A. and J.A. Cherry. 1979. Groundwater. Prentice-Hall, New Jersey.

Fuchs, M.R. 1990. Groundwater Monitoring Guidance for Solid Waste Facilities. Washington Department of Ecology. March 1990

San Juan, Charles. 1994. Natural Background Soil Metals Concentrations In Washington State. Publication No. 94-115. Washington Department of Ecology. October 1994



APPENDIX A

WATER LEVEL DATA AND CONTOUR PLOT



APPENDIX B

GROUNDWATER QUALITY DATA, STATISTICAL ANALYSES, AND TREND PLOTS



APPENDIX C

SURFACE WATER QUALITY DATA, STATISTICAL ANALYSES AND TREND PLOTS



APPENDIX D

UNDERDRAIN IRRIGATION AREA FIGURE, SOIL MOISTURE QUALITY, AND SOIL QUALITY



APPENDIX E

GAS MONITORING MEASUREMENTS



APPENDIX F

MARCH SAMPLING AND DATA VALIDATION MEMORANDA AND LABORATORY ANALYTICAL REPORT



APPENDIX G

SEPTEMBER SAMPLING AND DATA VALIDATION MEMORANDA AND LABORATORY ANALYTICAL REPORTS