W912DR18R0055_-_Attachment_AT_-_DLA-Richmond_OU-8_S_Lobe_Long_Term_Pump_Test_Tech_Memo_2015-12-01_Draft.pdf

TECHNICAL MEMORANDUM

OU 8 SOUTHERN AREA OF PLUME LONG TERM PUMPING TEST

SUMMARY OF METHODS AND PROCEDURES

DEFENSE SUPPLY CENTER RICHMOND, VIRGINIA

DECEMBER 2015

INTRODUCTION

This document summarizes the methods and procedures proposed for a long term pumping test in the southern area of the dissolved phase contaminant plume at Operable Unit (OU) 8 at the Defense Supply Center Richmond (Figure 1). A Work Plan providing additional detail on design and execution of the long term pumping test will be provided following concurrence on the overall approach described in this Technical Memorandum. The purpose of this effort is to perform a one-well long term pumping test at the southern end of the OU 8 dissolved phase contaminant plume to verify pumping rates in discrete strata, radius of influence, contaminant migration and hydraulic control. The southern area long term pumping test is an extension of the long term pumping test currently under operation in the northern portion of the plume. The southern area pumping test will closely follow the design and operation of the northern area pumping test. The field activities involved with this effort include installation of a pumping well and observation well, well pump with controls, and means to treat extracted groundwater as required. Groundwater samples will be analyzed by an off-site laboratory.

FACILITY INFORMATION

Defense Supply Center Richmond (the installation) is an approximately 650-acre installation located near Richmond, Virginia and is the Defense Logistics Agency’s (DLA) aviation demand and supply chain manager. OU 8 is located in the northeast portion of the installation.

The field activities presented herein will be performed by Arcadis under the direction of the United States Army Corps of Engineers (USACE) Baltimore District. The following sections present a brief background of OU 8 and the proposed field activities.

OU 8 BACKGROUND

OU 8 is defined as the groundwater beneath and downgradient of the Acid Neutralization Pits (ANPs), located in the northern portion of the installation. The ANPs are referred to as OU 5.

Based on previous investigations and evaluations, DLA and United States Environmental Protection Agency (US EPA), with concurrence from Virginia Department of Environmental Quality (VDEQ), selected institutional controls and monitored natural attenuation (MNA) with a contingency including, but not limited to, in-situ bioremediation to be the preferred remedy to address chlorinated solvent-impacted groundwater in the Upper Water Bearing Unit (UWBU) at OU 8. This remedy is outlined in the OU 8 Record of Decision (ROD) (Defense Supply Center Richmond, 2007). The Contaminants of Concern (COCs) identified in the ROD were

11787000

11787000

11787500

11787500

11788000

11788000

11788500

11788500

Data Sources: AECOM, GIS Data;

ESRI, ArcGIS Online, StreetMap Data Coordinate System: VA State Plane, South Datum: NAD 83 Units: Feet

0 200 400

Feet

Legend Other Wells

Extraction Well Location Injection Well location Vapor Monitoring Point MiHPT Sample Location Monitoring Well Location Piezometer Soil Boring Location

Figure 1 OU8 Long Term Pumping Test

Study Areas

Operable Unit 8 Defense Supply Center Richmond

Richmond, VA

Northern Area of Plume Long Term Pumping Test Study Area

Southern Area of Plume Long Term Pumping Test Study Area trichloroethylene (TCE) and vinyl chloride (VC). A two-tiered approach was outlined in the ROD to confirm MNA. In Tier 1, natural attenuation processes would be confirmed and attenuation rates determined during a three-year period (semi-annual monitoring events). Annual monitoring would begin in Tier 2 (beginning in Year 4). A Contingency Work Plan was proposed at the onset of Tier 2 if trigger criteria outlined in the ROD were met (i.e., MNA was not progressing as expected).

In accordance with the ROD and the follow-on Remedial Design (Earth Tech, 2008), semi-annual groundwater monitoring activities were initiated in September 2008. Semi-annual groundwater monitoring activities include collection of groundwater samples for laboratory and field analyses of COCs, daughter products and MNA parameters in the OU 8 monitoring wells.

MNA evaluations (recommended in the ROD) were performed in 2010 after 2 years of monitoring (AECOM, 2011). Results of these evaluations are summarized below:

MNA parameters indicated that groundwater geochemical conditions are not conducive to biodegradation. In addition, absence of daughter products in a majority of the OU 8 groundwater plume did not support the occurrence of biodegradation throughout the plume.

Evaluation of the groundwater monitoring data indicates that COC concentrations were increasing in a majority of pre-sentinel wells and COCs could migrate off-installation at concentrations exceeding US EPA Safe Drinking Water Act Maximum Contaminant Levels (MCLs) in the future.

Based on the above results, an Explanation of Significant Differences (ESD) to the OU 8 ROD was finalized in August 2011 (Defense Supply Center Richmond, 2011) to allow for implementation of the contingency remedy at OU 8. Additional evaluations conducted in 2011 indicated that the OU 8 Upper WBU groundwater contamination had migrated towards the Dervishian ARC (located off-site to the northeast of OU 8) and may be migrating further off-installation.

Additional monitoring wells have been added to the well network at OU 8 since 2011 to further delineate the COC plumes. Additionally, groundwater samples collected from temporary well points (direct-push groundwater samples) have provided further delineation on the edges of the COC plumes. The COC plumes at OU 8 are well defined with the southern boundary addressed during the December 2014 and March 2015 Direct Push Investigations.

A long term pumping test was initiated in the northern portion of the plume in 2015. The long term pumping test consists of two wells, one well pumping at a constant rate of approximately 4 gallons-per-minute (gpm) and the second well pumping at a rate of less than 0.5 gpm.

Groundwater from the pumping test is treated through inline venturi aerators to levels that allow discharge to a storm drain in accordance with the VDEQ General Stormwater Permit conditions.

Groundwater quality samples are routinely collected and groundwater response measured through pressure transducers installed in the pumping wells and three nearby monitoring wells.

Monthly samples will be collected from the discharge to the storm drain to demonstrate compliance with the VDEQ Stormwater Permit.

PUMPING TEST ACTIVITIES

The purpose of this effort is to perform a single well long term pumping test for a period of three to nine months at the northern end of the OU 8 dissolved phase contaminant plume to verify pumping rates in discrete strata, radius of influence, contaminant migration and hydraulic control. The length of time will depend on stabilization of groundwater levels and VOCs in the test well and observation well. The activities of this effort include:

Design and install a well for a long term pumping test located east of Warehouse 66 at the southern end of the OU 8 dissolved phase contaminant plume.

Treat extracted groundwater as required to meet the VDEQ general discharge permit requirements.

Maintain long term pumping and discharge treatment throughout a three to nine-month monitoring period.

Monitor dissolved phase chlorinated solvent contaminants, pumping rates, geochemical parameters, and water levels. Over a three to nine-month period document the performance and efficacy of this effort, and prepare a letter report detailing the findings.

Selection of Well Location:

Selection of the southern plume long term pumping test well location was determined by its location within the OU 8 contaminant plume and by using the radius of influence from the former dual phase extraction system.

Well Design:

For the purpose of this effort, a location bounded by OU8-MiHPT-38 approximately 50 feet to the north, OU8-MW102 approximately 60 feet to the south, and OU8-MW103 approximately 65 feet to the southeast (Figure 2) was selected for the proposed long term pumping test. Depth to groundwater in this area is typically between 12 feet and 16 feet below ground surface (BGS).

These three locations were sampled in March and April 2015 with tetrachloroethylene (PCE) concentrations of 41 micrograms per liter (µg/L), 86 µg/L, and 57.2 µg/L respectively. TCE concentrations from the same samples were 43.3 µg/L, 417 µg/L, and 238 µg/L. Based on results of the membrane interface probe profile completed at OU8-MiHPT-38 approximately 50 feet to the north, the highest concentrations of volatile organic compounds (VOCs) occur in the lower foot of the Upper WBU between 23 feet and 24 feet BGS at the base of the gravelly sand.

To minimize disturbance of the formation material and eliminate the need for drilling mud, the well will be installed using rotosonic drilling. A continuous rotosonic core will be obtained at the well location. This core will be used to set the final screen interval for the pumping well. The well will be constructed of 4-inch inside diameter (I.D.) schedule 40 polyvinyl chloride (PVC) casing and 4-inch ID stainless steel screen. The casing and screen will be joined using flush threaded joints. To eliminate any issue with placement of the gravel pack and to facilitate development of the well, the screen will consist of 5-foot long Johnson wire wrap stainless steel

Warehouse 66

MIHPT38

PCE = 41 ug/L TCE = 43.3 ug/L

MW102

PCE = 86 ug/L TCE = 417 ug/L

MW103

PCE = 57.2 ug/L TCE = 238 ug/L

MWANP17

PZ101

PZ107

SB597

SB667

SB668

11788000

11788000

Groundwater Quality Samples Collected March/April 2015 Data Sources: AECOM, GIS Data;

ESRI, ArcGIS Online, StreetMap Data Coordinate System: VA State Plane, South Datum: NAD 83 Units: Feet

0 20 40

Feet

Legend Pumping Test Wells

Test Well

Observation Well Buried Discharge Line Buried Electrical Well House

Utilities Storm Drain Manhole Power Pole Overhead Power Line

Other Wells MiHPT Sample Location Monitoring Well Location Piezometer Soil Boring Location

Figure 2 OU8 Southern Area of VOC Plume

Proposed Long Term Pumping Test Location

Operable Unit 8 Defense Supply Center Richmond

Richmond, VA

Muni-Pak pre-packed 20-slot screen with a 5-foot schedule 40 PVC tail pipe (Figure 3). At an anticipated maximum pumping rate of 5 gpm, the screen entrance velocity will be less than 0.01 feet/sec, which in combination with the use of the pre-packed screen will be sufficient to reduce mobility of fines from the formation material. To fully capture the vertical extent of the VOCs at the well location, the bottom of the screen interval will be placed approximately 1-foot below the base of the UWBU at an estimated depth of 25-feet BGS. Total depth of the well, including the tail pipe, will be approximately 30-feet BGS.

An observation well will be constructed approximately 15 feet south of the pumping well using the same methods and materials as the pumping well. Constructing the observation well to the same specifications as the pumping well provides flexibility to expand the test to include two pumping wells if dictated by field conditions.

Pumping Test Operation:

A 3-inch Grundfos 5SQE05-140 single phase 230 Volt (V) pump or equivalent with dry run protection capable of achieving the desired flow rates in the range of 2 to 5 gpm will be installed.

The pump will be placed below the screen, in a five foot sump, to increase the overall available drawdown and to reduce the impact that pumping will have on the entrance velocity of groundwater entering through the screened interval. A pump shroud will be utilized to help ensure the life of the well pump by continuously moving water over the pump motor, and cooling it.

An initial 48-hour pre-test will be completed with the pumping well operating at the intended discharge rate. Drawdown will be measured using pressure transducers in the pumping well and observation well for the duration of the test. The system will be initially equipped with inline venturi aerators similar to the aerators used for the northern area test. Groundwater will be pumped to a 21,000 gallon Baker Tank for holding prior to discharge to the storm drain. Four sets of groundwater samples will be collected from the sample port at the well head prior to the inline aerators and at the point of discharge to the Baker Tank at approximate 12-hour intervals and analyzed for VOCs and geochemical parameters. At the end of the 48-hour test an additional sample will be collected from the Baker Tank. If necessary, the pre-test water from the Baker Tank will be treated through a portable granular activated carbon (GAC) unit or a skid style air stripper prior to discharge to the storm drain.

Results of the pre-test sampling will be used to determine if treatment in addition to the inline aerators is necessary. Technologies that will be considered include:

Air entrainment and volatilization through an air stripper, Oxidation using ultraviolet/hydrogen peroxide, or Adsorption using GAC.

The treatment method selected will be tailored to meet the VDEQ general discharge permit requirements as efficiently as possible.

Following the pre-test, the long term pumping test and appropriate discharge treatment will begin normal operation with discharge into the nearby storm drain as allowed by the VDEQ general discharge permit.

Monthly checks will be done on the treatment efficiency by collecting water samples of the influent and effluent and tested in accordance with USEPA SW-846 Method 8260B for VOCs.

The pumping and treatment system will be checked weekly to ensure that all parts are operating properly and repaired as necessary. The treatment will be checked to ensure that fouling has not occurred and is not affecting the treatment efficiency. If fouling has occurred the treatment will be bypassed, and discharge will be containerized while the treatment in use is cleaned or replaced.

Groundwater Sampling:

A total of four groundwater sampling events will be completed at the site to monitor COCs and water levels. The groundwater sampling will assess the initial conditions, and then at quarterly events: 1) at start-up, 2) end of first quarter, 3) end of second quarter, and 4) end of third quarter (end of test). Samples will be analyzed for VOCs by USEPA SW-846 Method 8260B. In addition to the VOCs, the following field measurements will be completed for all sampling events and the following laboratory geochemical parameters will be analyzed from samples collected at start-up and at the end of the test:

Field Measurements:

pH Temperature Dissolved oxygen Specific conductance Oxidation reduction potential Turbidity

Laboratory measurements:

Major cations (total and dissolved): iron, manganese, calcium, magnesium, potassium Major anions: alkalinity (carbonate and bicarbonate), chloride, sulfate Silica, boron Nitrogen: nitrate+nitrite and total Kjeldahl nitrogen Total organic carbon and dissolved organic carbon Total dissolved solids Total suspended solids Dissolved gasses (methane, ethane, ethane, and carbon dioxide) Microbial (Dehalobacter DCM, chloroform reductase, sulfate reducing bacteria, methanogen)

The quarterly sampling events for the Long Term Pump Well will be conducted in concurrence with the “QUARTERLY NORTHERN PLUME GROUNDWATER MONITORING” program.

Groundwater samples will be collected using low-flow sampling techniques during the prescribed sampling events. The wells included in the sampling network are presented on Figure 4 and Table 1. Wells will be purged until stabilization of geochemical parameters and water level is achieved. Groundwater samples will be collected in laboratory supplied and certified bottles and shipped via overnight courier to an off-site laboratory for VOCs analysis

Warehouse 66

MW102

MW103

MW123

MW92

MWANP17

MWANP26

MWANP27

MWANP3

OS72MW1

11788000

11788000

Groundwater Quality Samples Collected March/April 2015 Data Sources: AECOM, GIS Data;

ESRI, ArcGIS Online, StreetMap Data Coordinate System: VA State Plane, South Datum: NAD 83 Units: Feet

0 50 100 150

Feet

Legend Quarterly Monitoring Locations

Test Well

Observation Well Monitoring Well Location

Utilities Storm Drain Manhole Power Pole Well House Overhead Power Line Buried Discharge Line Buried Electrical

Figure 4 OU8 Southern Area of VOC Plume

Proposed Long Term Pumping Test

Quarterly Monitoring Locations

Operable Unit 8 Defense Supply Center Richmond

Richmond, VA using SW-846 EPA Method 8260B. Appropriate quality assurance/quality control (QA/QC) samples (one duplicate sample, one matrix spike/matrix spike duplicate sample, one equipment blank and one trip blank) will also be collected for each sampling event.

Table 1 : Quarterly Sampled Wells

Southern Area of Plume

OU8‐MWANP3

OU8‐MW92

OU8‐OS72MW1

OU8‐MWANP26

OU8‐MW102

OU8‐MW123

OU8‐MWANP17

OU8‐MW103

OU8‐MWANP27

Southern Area Pumping Test Well

Southern Area Pumping Test Observation Well *Additional new wells installed will be added to this sampling list during the quarterly sampling events.

Pressure transducers will also be installed in the long term pumping well, the new observation well, and in three existing monitoring wells (MWs 102, 103 & ANP17) to monitor groundwater levels. Data will be collected from transducers on a monthly basis during the monthly influent and effluent checks.

REPORTING

A summary of the data collected and analysis of the performance and efficacy of this effort will be prepared. Data collected as part of the operations and maintenance monitoring and groundwater sampling will be reported during the planning team meetings, and made available RAB presentations. A letter report detailing the findings will be prepared and submitted approximately 45 days after discontinuation of the long term pumping test.

REFERENCES

AECOM, 2014. Final Quality Assurance Project Plan, Defense Supply Center, Richmond, Richmond, Contract No. W912BV-10-D-2006, Task Order 0014 August 2014.

AECOM, 2011. Final Remedial Action Monitoring Report (Sept 2009 and March 2010)

Operable Unit 8, Defense Supply Center Richmond, March 2011.

Defense Supply Center Richmond, 2007. Final Record of Decision Operable Unit 8 Acid

Neutralization Pits Groundwater Defense Supply Center Richmond, Virginia. February 2007.

Defense Supply Center Richmond, 2011. Final Explanation of Significant Differences Operable

Unit 8 Acid Neutralization Pits Groundwater Defense Supply Center Richmond, Virginia.

August 2011.

Defense Supply Center Richmond, May 2015. Technical Memorandum – OU 8 Long Term Pumping Test Work Plan, Defense Supply Center Richmond, Virginia.

Earth Tech, 2008. Final Remedial Design/Remedial Action Work Plan for Operable Unit 8, Defense Supply Center Richmond, Virginia. September 2008.