Phytoremediation at a Petroleum Phytoremediation at a Petroleum Phytoremediation at a Petroleum Release Site

Phytoremediation at a Petroleum Release Site

Mill Creek Environmental Services, Inc.1818 Perimeter RoadDawsonville, Georgia 30534

Dan Centofanti, PGDan Centofanti, PG Geologist, Technical Director

Project ContributorsProject ContributorsProject ContributorsProject ContributorsThanks to:

Debbie Fallen PGDebbie Fallen, PG

Valentine Nzengung, PhDValentine Nzengung, PhD

Claude Terry, PhD, REM, DABTy, , ,

Site InformationSite InformationSite InformationSite Information 30,000 gallons of gasoline was released from a , g g

petroleum facility in the Piedmont of Georgia. Fuel flowed across a mild slope and into a large

i d h l d d i h iravine and then traveled downstream in the ravine for approximately 1000-feet.

The ravine is an erosional feature that ranges from The ravine is an erosional feature that ranges from 10-15 feet deep and 8-40 feet wide.

The erosional ravine was generally dry, but e e os o v e w s ge e y d y, bucontained several small springheads and pools during wet seasons.

Spring-WetSpring-WetSpring WetSpring Wet

Spring-DrySpring-DrySpring DrySpring Dry

Site PlanSite PlanSite PlanSite Plan

Site GeologySite Geology

Lithologies below the release site are varying mixtures of sand, silt, and clay found as saprolite weathered from crystalline bedrock. Groundwater is relatively deep (15-30 feet) in the immediate area of the releasearea of the release.

Lithologies in the ravine are generally sandy alluvial deposits and fill materials underlain byalluvial deposits and fill materials underlain by saprolite. Groundwater is relatively shallow (1-7 feet) in the ravine.ee ) e v e.

Initial Response ActionsInitial Response ActionsInitial Response ActionsInitial Response ActionsThe following actions were completed immediatelyThe following actions were completed immediately

following the release:Seventeen (17) free-product recovery trenches/ sumps

and thirteen (13) boreholes were installed in the ravine by hand. Skimmer pumps and collection systems were installed to recover free-productinstalled to recover free product.Two (2) underflow dams were constructed in the ravine

to contain/collect free-product in the event of heavy rainfall.

Initial Response Actions (cont )Initial Response Actions (cont )Initial Response Actions (cont.)Initial Response Actions (cont.) Heavily impacted soil from the immediate area of Heavily impacted soil from the immediate area of

the release was excavated and stockpiled for off-site disposal.

Within 4-months following the release approximately 15,000 gallons of free-product had been recovered from the recovery trenches.

Extent of and Magnitude of Extent of and Magnitude of ContaminationContamination

Assessment activities were completed and the extent of contamination was determined to be limited to the immediate area of the release and thelimited to the immediate area of the release and the bottom of the ravine.

Worst Case Soil Analytical Results:Worst Case Soil Analytical Results: B – 150 mg/kg T – 1,100 mg/kg, g g E – 320 mg/kg X – 1,600 mg/kg, g g TPH GRO – 44,000 mg/kg

Corrective Action PlanCorrective Action Plan

Groundwater:Groundwater modeling indicated that the groundwater plume would stabilize prior to impacting any potentialplume would stabilize prior to impacting any potential receptors. Monitored natural attenuation was approved as the remedial action for groundwater.

Soils:Soil vapor extraction was approved as a remedial action

for source area soils in the immediate area of thefor source area soils in the immediate area of the release.Phytoremediation was evaluated and approved as the

remedial action for impacted soils in the ravineremedial action for impacted soils in the ravine.

PhytoremediationPhytoremediation

Phytoremediation is the use of plants to remove, degrade, and/or stabilize , g ,contaminants in soils or sediments.

Phytoremediation is particularly useful Phytoremediation is particularly useful where the contamination is shallow and roots can penetrate the impacted arearoots can penetrate the impacted area.

PhytoremediationPhytoremediation

Phytoremediation was chosen for this site for the following reasons:

Li i d i d f d ill iLimited to no access to contaminated areas for drill rig and heavy equipment.Shallow groundwater and periodic flooding of ravine.g p gLimited extent of contamination.Pilot tests and initial site evaluation indicated the potential for Phytoremediation to be successfulpotential for Phytoremediation to be successful.

Phytoremediation ProcessesPhytoremediation Processes

The removal, degradation, and/or stabilization of contaminants occurs through the following processes:Phytodegradation (Phytotransformation)Rhi d d iRhizodegradationRhizofiltrationPhytostabilizationPhytostabilizationPhytoextractionOther Processes

Phytodegradation Phytodegradation Phytodegradation (Phytotransformation)Phytodegradation (Phytotransformation) The breakdown of contaminants taken up

by plants through metabolic processes y p g pwithin the plant, or the breakdown of contaminants external to the plant through p gthe effect of compounds (such as enzymes) produced by the plants.p y p

RhizodegradationRhizodegradation

Also known as enhanced rhizosphere biodegradation, is the breakdown of an g ,organic contaminant in soil through microbial activity that is enhanced by the y ynatural substances released by plant roots.

RhizofiltrationRhizofiltration

The adsorption, concentration, or precipitation of contaminants on to plantprecipitation of contaminants on to plant roots due to biotic or abiotic processes. This process involves the filtering of waterprocess involves the filtering of water through root mass to remove contaminants.

PhytostabilizationPhytostabilization

The immobilization of a contaminant in soil through absorption and accumulation bythrough absorption and accumulation by roots, adsorption on to roots, or precipitation within the root zone of plantsprecipitation within the root zone of plants. Occurs because of changes in the chemistry of the contaminants which becomeof the contaminants which become insoluble and/or immobilized on soil components.components.

PhytoextractionPhytoextraction

The uptake and accumulation of contaminants into the aboveground portion g pof the plant. This process mostly applies to metals and radionuclides.

Other ProcessesOther Processes

VolatilizationAdsorptionAdsorptionAbsorption

E h d Bi di i Enhanced Bioremediation

1999 Site Preparation1999 Site Preparation Product recovery sumps installed in the floor of

the ravine were removed and filled.U d b h d d f h fl Underbrush and trees were removed from the floor of the ravine. Native hydrophytic plants were left.

A t i h l f l h k d i t th t A two inch layer of mulch was worked into the top one foot of the soils to add organic material and to improve soil nutrientsimprove soil nutrients.

Trees were removed from the top of the ravine to provide adequate sunlight to the planting terraces.provide adequate sunlight to the planting terraces.

Site Preparation Cont.Site Preparation Cont.

Numerous structures were built across the floor of the ravine to construct terraces for planting:• Terrace Overflow Dams were built at theTerrace Overflow Dams were built at the

downstream end of each terrace. These were designed to trap water and sediment behind the dam.

Site Preparation Cont.Site Preparation Cont.• Flood Control Structures were built either of

stacked riprap rock or stacked logs. These p p gwere placed between plots and across side drainage areas into the ravine to reduce flow grates and erosional damage caused by flash flooding.g

1999 Site Evaluation and Pilot Testing1999 Site Evaluation and Pilot Testing1999 Site Evaluation and Pilot Testing1999 Site Evaluation and Pilot TestingPhytoremediation pilot testing was conducted over

two consecutive growing seasons The objective oftwo consecutive growing seasons. The objective of pilot testing was to screen local plant species for their tolerance to survive in gasoline contaminatedtheir tolerance to survive in gasoline contaminated soils.

Woody plant species screened include:y p pBlack Willow (Salix nigra)Cottonwood (Populus deltoides)

These trees were chosen for their fast growth and transpiration rates, their deep rooting ability, and their ability to flourish in shaded wet soils.

Site Evaluation and Pilot Testing Site Evaluation and Pilot Testing (cont.)(cont.)

Herbaceous groundcover plant species screened include:l l d (C i )local sedge (Carex stricta)local rush (Juncus effusus)local burreed (Sparganium eurycarpum)local burreed (Sparganium eurycarpum)local cattail (Typha latifolia)local arrowhead (Sagittaria latifalia and Peltandra

i i i )virginica)These species were transplanted from a local wetland and

were chosen for their ability to tolerate standing water.

Black Willow (Salix nigra)Black Willow (Salix nigra)Black Willow (Salix nigra)Black Willow (Salix nigra)

Rush (Juncus effusus)Rush (Juncus effusus)Rush (Juncus effusus)Rush (Juncus effusus)

Eastern Cottonwood (Populus deltoides)Eastern Cottonwood (Populus deltoides)Eastern Cottonwood (Populus deltoides)Eastern Cottonwood (Populus deltoides)

Cattail (Typha latifalia )Cattail (Typha latifalia )Cattail (Typha latifalia )Cattail (Typha latifalia )

Arrowhead (Sagittaria latifalia )Arrowhead (Sagittaria latifalia )Arrowhead (Sagittaria latifalia )Arrowhead (Sagittaria latifalia )

Pilot Testing ResultsPilot Testing Results1999-2000 Growing Seasons1999-2000 Growing Seasons

Cottonwood, burreed, and cattail exhibited minimal success.

Black willow, rush, sedge, and arrowhead were successful in most plotswere successful in most plots.

Full Scale ImplementationFull Scale Implementation2001 Growing Season2001 Growing Season

A total of 290 bare root white willow (Salix alba) trees (4-6 ft tall) were planted four feet apart throughout the ravinethroughout the ravine.

The trees were deep root planted to increase rhizodegradation in the contaminated soils andrhizodegradation in the contaminated soils and shallow aquifer.

A power auger and post hole diggers were used to plant the trees four feet below the ground surface.

An aged compost consisting of nitrogenous peanut h ll d l d i h h lshells and cow manure was placed in each hole.

Bare root willowsBare root willows

Deep Root PlantingDeep Root Planting

Transplanting Wetland SpeciesTransplanting Wetland Species

Planting TerracesPlanting TerracesPlanting TerracesPlanting Terraces

CompostingCompostingCompostingComposting

Full Scale Implementation (cont.)Full Scale Implementation (cont.)

The terrace surface was covered with additional compost after planting. p p g

Irrigation was provided to the site by pumping from a nearby creek into thepumping from a nearby creek into the ravine.

Phytoremediation MonitoringPhytoremediation Monitoring

Soil samples were collected from each terrace at three depths: 1ft and 3 ft at all locations and 5 ft at locations within the ravine where groundwater was >5ft below ground surface.

ll il li i hi h i d d All soil sampling within the ravine was conducted with a hand auger semiannually/annually. G d t li l d t d Groundwater sampling was also conducted quarterly/semiannually.

Soil SamplingSoil SamplingSoil SamplingSoil Sampling

Phytoremediation Monitoring Phytoremediation Monitoring (cont.)(cont.)

Growth rates of the willow trees and wetland plants were monitored to ensure vegetation was healthy throughout the growing season.

Leaves were inspected to determine infestations f di dfrom disease and pests.

Plant tissues were collected to evaluate gasoline t i th t l d b hcomponents in the roots, leaves and branches.

Phytoremediation 2001 Growing Phytoremediation 2001 Growing Season ResultsSeason Results

Bare root willows grew by more than 10 feet.

A mortality rate of 10% was observed for the trees in areas with the highest gasoline concentrations.

Sycamore, sweet gum, and tulip trees seeded during the first growing season and produced volunteers throughout the ravine.

2001 Growing Season2001 Growing Season

Phytoremediation 2001 Season Phytoremediation 2001 Season Results (cont.)Results (cont.)

Benzene – 1-foot depth – 44% decrease. Total BTEX – 2-3-foot depth – 55% decrease.p BTEX detected in plant tissue samples confirmed

that the trees were removing contaminants. BTEX concentrations in the plant branches and leaves suggested that the hydrocarbons taken up into the

l t t l ti i th l t tiplants were not accumulating in the plant tissues.

Phytoremediation 2002 Growing Phytoremediation 2002 Growing Season ResultsSeason Results

Willow trees grew an additional 2-8 feet. Sycamore, sweet gum, and tulip poplar trees y , g , p p p

continue to show vigorous growth. Benzene – 2-3-foot interval depth – 80% decrease. Total BTEX – 2-3-foot depth – 81% decrease. Groundwater continued to show an overall

decrease in BTEX concentrations.

2006 Growing Season2006 Growing Season2006 Growing Season2006 Growing Season

2009 Phytoremediation Results 2009 Phytoremediation Results

The planted willows continue to show growth, but in many of the terraces the g , ynative sycamore, sweet gum, and tulip poplar trees have shown the most vigorous p p ggrowth. The average height of native trees within the ravine reached 25-35 feet. Average height of remaining willows are 15-25 feet.

2009 Growth2009 Growth

Sycamore (Platanus occidentalis)Sycamore (Platanus occidentalis)Sycamore (Platanus occidentalis)Sycamore (Platanus occidentalis)

Black willow (Salix nigra)Black willow (Salix nigra)

Phytoremediation Results (cont.)Phytoremediation Results (cont.)

An overall decrease of 99% in the concentration of benzene and total BTEX in soils has been shown at the site since planting began in 1999.p g g

Groundwater concentrations have shown a significant decrease in areas surrounding thesignificant decrease in areas surrounding the ravine.

Ravine Soil Sample Results Ravine Soil Sample Results Ravine Soil Sample Results Figure 2a: Terrace #1

BTEX Concentrations 2001 and 2009

Ravine Soil Sample Results Figure 2a: Terrace #1

BTEX Concentrations 2001 and 2009BTEX Concentrations 2001 and 20091-foot depth.

BTEX Concentrations 2001 and 20091-foot depth.

Ravine Soil Sample Results Ravine Soil Sample Results Ravine Soil Sample Results Figure 2b: Terrace #1

BTEX Concentrations 2001 and 20093 f t d th

Ravine Soil Sample Results Figure 2b: Terrace #1

BTEX Concentrations 2001 and 20093 f t d th3-foot depth.3-foot depth.

Ravine Soil Sample Results Ravine Soil Sample Results S S pFigure 3a: Terrace #2 and #3

BTEX Concentrations 2001 and 20091 foot depth

S S pFigure 3a: Terrace #2 and #3

BTEX Concentrations 2001 and 20091 foot depth1-foot depth.1-foot depth.

Ravine Soil Sample Results Ravine Soil Sample Results Figure 3b: Terrace #2 and #3

BTEX Concentrations 2001 and 20093-foot depth

Figure 3b: Terrace #2 and #3BTEX Concentrations 2001 and 2009

3-foot depth3 foot depth.3 foot depth.

ConclusionsConclusions

Phytoremediation has proven successful at this site over the 11 year implementation period.

The 99% decrease in total BTEX concentrations has demonstrated that phytoremediation is a viable

h d f f h ll il i hmethod for treatment of shallow soils in the inaccessible areas where other technologies were not feasiblenot feasible.

No Further Action for the ravine area soils was approved on May 19 2011approved on May 19, 2011.

Before and AfterBefore and After

Groundwater Concentrations 2001Groundwater Concentrations 2001

Groundwater Concentrations 2013Groundwater Concentrations 2013

Phytoremediation at a Petroleum Phytoremediation at a Petroleum Phytoremediation at a Petroleum Release Site

Phytoremediation at a Petroleum Release Site

Mill Creek Environmental Services, Inc.1818 Perimeter RoadDawsonville, Georgia 30534

Dan Centofanti, PGDan Centofanti, PG Geologist, Technical Director