# Na **tur al A** 

**tte nua**  **tion in Fr actur**  **ed Ro**  **ck Aquif** **er s** 

**USEP A**  **- USGS**  **Fr actur**  **ed Ro**  **ck W orkshop**  **EP A R**  **egion 2**  **14 January**  **2014** 

# Allen M. Shapir **o, USGS** **Natur al A**  **tte nuation in Fr** **actured Ro**  **ck 2**  

# The Import **ance of Natur**  **al At**  **te nuation**  **in the Gr**  **oundw ater**  **Manag ement at Sites of**  **Con ta**  **mination in Fr**  **actur ed**  **Ro ck Aquif** **er s**   **Monitored Natur**  **al A**

**tte nuation (MNA) is curr**  **ently evaluated as a gr oundwater**  **re mediation s**  **tr ategy** 

**, lik e**  **other gr oundwater**  **re mediation s**  **tr ategies (e.g.,**  **Pump -**  **and -**  **Tr eat,**  **Thermal T re**  **atments, In Situ Chemical Oxidation, etc.)**  **If the R emedial Action Objective is to r**  **es tore**  **gr oundwater**  **, re**  **mediation st**  **ra te**  **gies ar e evaluated on achieving ARARS**  **( A**  **pplicable or R**  **elevant and A**  **ppr opriate**  **R equir**  **ements )**  **in a “Reasonable Time Fr**  **ame”**  **MNA has been successfully applied at a lar** **ge number of sit**  **es of gr oundwater**  **contamination over the pas**  **t 15 y ear**  **s, including some sit es in fr**  **actur ed r**  **ock**  **Ther e ar**  **e man y (**  **fe der**  **al, indus trial,**  **and s tate)**  **sites, wher e achieving ARARs in**  **a “R**  **easonable Time**  **Fr ame”**  **is unlik** **ely in fr actur**  **ed r ock**  Difficulties in char acterizing comple x distribution of contaminants (e.g., sour ce zo ne, flow paths, contaminant mass in flow - limited re gions of the aquifer)  Long - re sidence times of contaminants in flow - limited r egions of the aquifer  Challenges to r emedial technologies in tr ansforming /destr oying contaminant mass in sour ce zo ne and dissolved - phase plume in flow - limited re gions of the aquifer

Na val Air W arfare Center

, W est Trenton, NJ Weathered rock
Unweathered rock Estimate of T CE Mass

in Fr actur es and R ock Matrix

**Natur al A**  **tte nuation in Fr** **actured Ro**  **ck** 

# Te **chnical Challeng**  **es to**  **R emediation**  **in Fr**  **actur ed**  **Ro ck in a R**  **easonable Time Fr**  **ame Pr** **ogram/Agency Number of**  **Contaminated Fa**  **cilities Number of Sites**  **Estimated Cost**  **Complete ($B)** DoD 4,329 $12.8 CERCLA 1,364 $16 - $23 RCRA 2,844 $32.4 UST 87,983 $11 DOE 3,650 $17.3 - $20.9 Other F ederal Sites >3,000 $15 - $22 State Sites >23,000 $5 **TOT AL**  **>126,000 $110**  **- $127**  

# The Magnitude **of the Pr oblem** 

National R esearch Council, 2013 **Natur al A**  **tte nuation in Fr** **actured Ro**  **ck Natur** **al A tte**  **nuation in Fr actured**  **Ro ck**  National R esearch Council, 2013 

# The Magnitude **of the Pr oblem**   

### >126,000 **sit es ha**  **ve residual gr oundw**  **ate r contamination**  **tha t pr**  **events “c**  **losur e” . . . l**  **ik ely an**  **under estima**  **te. . .e.**  **g., counting of “f** **acilities” and “s**  **ites” diff er between pr**  **ogr ams, does not include**  **DoD fa**  **cilities with Remedy in Place (RIP) or Response**  **Complete (RC), etc.**   

### Cost of r **emedia tion $110**  **- $127**  **Billion. .**  **.lik ely**  **an under estima**  **te given technical**  **limita tions**  **of achieving Unlimit**  **ed Use/Unr**  **estricted Exposur**  **e (UU/UE).**  **. .**  

### Estima **ted ~10 %**  **of sit es (~12,000**  **sit es) are “** **comple x”**  **. . . r**  **estor at**  **ion unlik** **ely f or decades or centuries. . . ~10% of all sites will account f** **or ~70% of total cleanup costs**  **[Ehlers and Ka**  **vanaugh ,**  **2013] . . .** Analysis of 80 Delisted NPL Groundwater Sites

14
4

19 14 2 4 12 6 5 

# MCL Char act eriz ation **MCLs Achieved: Active Remedy: No L**  **TM MCLs Achieved: Active**  **Remedy: LT**  **M**

**MCLs Not Achieved: LT**  **M MCLs Not Achieved:**  **Deleted Based**  **on Risk Assessment: No L**  **TM MCLs Not Achieved:**  **Deleted Based**  **on Risk Assessment: LT**  **M Remedial**  **Objective O**  **ther Than**  **Meeting M**  **CLs MCL Achievement**  **Unknown Not a Groundw**  **ater Site** 

**MCLs Achieved: No Active Remedy:**  **No L**

**TM**

**Natur al A**  **tte nuation in Fr** **actured Ro**  **ck** National R esearch Council, 2013 

# Ar **e “Closed” Sit es “Closed” ?** Schofield Barracks (U.S. Army), Oahu, Hawaii 17,000 acre facility Land fill, sewage, industrial and vehicle waste, explosives Water supply well impacted by TCE (100 ppb)
• Basaltic rock

• Thin, horizontal lava flows (hydraulic conductivity 100’s to 1,000’s ft

/day)

• Intrusive dikes compartmentalize groundwater

• Groundwater 500 - 600 ft below land surface

• U.S. Army applied for upfront TI Waiver as part of ROD, 1996 • Air strippers on drinking water wells, 1986 • Monitoring wells • Delisted from NPL, 2000 • 5 - year reviews 

# ARARs W**aiv er**  **– Te**  **chnical Impr actic**  **ability**

**Natur al A**  **tte nuation in Fr** **actured Ro**  **ck**Letterk enn y Arm y Depot, Chambersburg, PA

• Testing, storage, overhaul of track vehicles • Storage, transportation of industrial chemicals, petroleum • Storage, modification of ammunition

• Groundwater contaminated with TCE, PCBs • Soils contaminated with heavy metals, VOCs • Facility divided into 7 Operable Units (OUs)

• In Situ Chemical Oxidation (ISCO) applied to VOC contamination in groundwater without success • Facility overlies limestone and dolomite • Structural faulting in the area • Karstic features (sink holes, caverns, springs)

Letterkenny Army Depot

• U.S. Army has been unable to obtain a TI waiver for selected OUs 

# ARARs W**aiv er**  **– Te**  **chnical Impr actic**  **ability (?)** 

**Natur al A**  **tte nuation in Fr** **actured Ro**  **ck**77 TI waivers (up through November 2010)

~3/4 of TI waivers attributed to h ydrogeology or nature of contamination
Deeb et al., 2011 Hydrogeologic Setting

Ty pe of Contaminant 

# ARARs W**aiv er**  **– Te**  **chnical Impr actic**  **ability**

**Natur al A**  **tte nuation in Fr** **actured Ro**  **ck**77 TI waivers (up through November 2010)

Distribution of TI W aivers by EP A Regions

Appr oximately 1⁄2 of states have not had a TI waiver Distribution of CERCLA sites is not evenly distributed over EP A regions Hydrogeologic conditions differ fr om region to region TI W aivers Granted Over Time

**Natur al A**  **tte nuation in Fr** **actured Ro**  **ck** 

# ARARs W**aiv er**  **– Te**  **chnical Impr actic**  **ability**

Deeb et al., 2011**Natur al A**  **tte nuation in Fr** **actured Ro**  **ck 11**  

# The Import **ance of Natur**  **al At**  **te nuation**  **in the Gr**  **oundw ater**  **Manag ement at Sites of**  **Con ta**  **mination in Fr**  **actur ed**  **Ro ck Aquif** **er s**   

### Lar**ge number**  **of sites ar e char** **acteriz ed as “** **comple x”** **. . .ARARs unlik** **ely to be achieved in decades to centuries. . .**   

### Unlik**ely tha t stak** **eholder s will accept wide spr**  **ead applica tion**  **of ARARs Wa**  **ivers (T**

**echnical Impr acticability)**  **at fr** **actur ed r**  **ock sites**  

### Need to consider longer time fr**ames of r emedia**  **tion and r emedial**  **str ate**  **gies tha t ma**  **y evolve over time, recognizing tha t some active**  **re medies ma**  **y r each a point**  **of diminishing returns. . .Na**  **tur al A**  **ttenuation will lik** **ely be a component in the manag**  **ement of a lar ge**  **number of fr** **actur ed r**  **ock sites. . .**  

### Ther **e is a need to document the e xistence of Na**  **tur al A**  **ttenuation and**  **under stand the long**  **- term prospects**  **fo r continued**  **Na tur** **al A ttenuation** **12**

 

### MNA **– encompasses**  **all na tur** **al a ttenuation**  **pr ocesses (not just**  **biological) –**  **pr eference f** **or those pr ocesses tha**  **t degr ade or destr**  **oy contaminants**   

### Conditions **at each site ar**  **e unique, but common fr** **amework is applied in documenting**  **na tur** **al a ttenuation** 

**Natur al A**  **tte nuation in Fr** **actured Ro**  **ck** 

# Monit **or ed Natur**  **al At**  **te nuation**  **EP A Pr**  **ot ocol**  **(1999)**

 

### Lines of evidence (1999)  

### Historical chemical data indicating **decr ease in contaminants**  **of concern along**  **flowpa ths**   

### Hydrogeological and geochemical da **ta to**  **demonstr ate**  **(indir ectly) types of**  **na tur** **al a ttenuation processes and r** **ate s**   

### Field or micr **ocosm studies** **Natur al A**  **tte nuation in Fr** **actured Ro**  **ck 13**  

# Monit **or ed Natur**  **al At**  **te nuation**  **Re cen**  **t Adv ances**   **Development of micr obiological tools.**  **. P olymer**  **ase Chain R eaction (PCR) . .**  **.explicitly identify pr esence**  **of Dehaloc** **coides (**  **Dhc ) species in gr**  **oundwater known to carry out r**  **eductive dechlorination**   **Compound Specific Isot ope**  **Analysis (CSIA) . . .r atio of carbon isotopes.**  **. .**  **dechlorination pr**  **ef er**  **entially metaboliz es**  **12 C**  **in comparison 13**  **C, changing the**  **isotope ra**  **tio of T CE,**  **cis -**  **DCE, V C, and**  **ethene as r**  **eductive dechlorination**  **continues. . .clearly identifies that decr**  **eases in concentr**  **ations of chlorinated**  **ethenes ar**  **e a pr oduct**  **of dechlorination**  **ra ther dilution. . .**   **St atistical model corr**  **elating pr esence**  **of Dhc**  **with g eochemical par**  **ameters . .**  **.o xidation**  **- re**  **duction potential (ORP), methane, and nitr** **ate + nitrite**  **Re cent advances**  **pr ovide quantitative (lines of**  **) evidence fo**  **r reductive dechlorination** 
Wilson 2010**Natur al A**  **tte nuation in Fr** **actured Ro**  **ck 14**  

# Monit **or ed Natur**  **al At**  **te nuation**  **At tribut**  **es tha t**  **Lead to**  **Success**
 **Detailed under standing**  **of flowpaths**  **fr om sour**  **ce t o r**  **eceptors –**  **design of monit**  **oring well network –**  **a challeng e in fr**  **actur ed r**  **ock**  **Sour ce z**  **one contr ol**  **– to**  **pr event further**  **downgr adient**  **contamination –**  **re mediation or containment**   **Monitoring that demons**  **tr ates**  **substantial re**  **duction in contaminant**  **concentr ation**  **over a decade or mor**  **e –**  **re ductions**  **in concentr ations**  **by or der**  **of magnitude**  **Monitoring includes g**  **eochemical and micr**  **obial par ameters**  **that document gr**  **oundwater is an appr**  **opriate habitat for attenuation**   **Quantitative evaluation of spatial distribution of contaminants**  **and their degr**  **adation pr oducts**  **(usually thr ough**  **mathematical modeling tools) Natur** **al A tte**  **nuation in Fr actured**  **Ro ck**  **15** 

# Monit **or ed Natur**  **al At**  **te nuation**  **Application to**  **Fr actur**  **ed R ock**   **Successful applications of MNA in dissolved phase plume in fr** **actur ed r**  **ock document**  **fo r selected**  **ar eally**  **extensive plumes . . .1000’ s**  **of f eet. . . see, e.g.,**  **Tw in Cities Arm**  **y Ammunition Plant (MN) -**  **sands tone,**  **Bell Aer**  **ospace Te**  **xtr on**  **Wheatfield Plant (NY) -**  **dolomite**  **Plumes over 1000’ s of meter**  **s –**  **monit oring wells**  **interpreted as if along a single flow path**   **Curr ent s**  **truggle t o interpr**  **et MNA in fr actur**  **ed ro**  **ck over dimensions wher**  **e flowpaths**  **ar e**  **convoluted (10’**  **s -**  **100’ s of meter**  **s)**  **“ Flowpath**  **- independent**  **” interpretation of MNA**  **(see, e.g., Br adley et al., 2009)**  **- an attempt**  **to address this issue at discr**  **ete monitoring locations** 

# Monit **or ed Natur**  **al At**  **te nuation**  **in Fr actur**  **ed Ro**  **ck**

**Obser va**  **tions**

**16** 

###  **Natural attenuation (biotic**  **and abiotic processes) will likely become an**  **issue at some point in the life span of remedial activities**  **at fractured rock sites**   **Estimates of attenuation**  **will to change over time. . .one cannot expect degradation rates to remain constant.**  **. .for long time frames, one will need to document**  **the processes and conditions that will maintain**  **natural attenuation**   **Over dimensions of 10’s**  **– 100’s**  **of meters, monitoring wells may not**  **characterize representative flowpaths**  **. . .under such conditions in**  **fractured rock, it is difficult to infer if attenuation**  **will reduce (spatially distributed)**  **concentrations and contaminant**  **mass Natur** **al A tte**  **nuation in Fr actured**  **Ro ck** **Natur al A**  **tte nuation in Fr** **actured Ro**  **ck 17**  

# Sug **ge ste**  **d R ef** **er ences**  Bradley , P. M. , Lacombe, P

. J. , Imbrigiotta , T. E. , Chapelle , F. H. , and Goode, D. J. , 2009, Flowpath independent monitoring of reductive dechlorination potential in a fractured rock aquifer , Ground W

ater Monitoring and R

emediation, v. 29, no. 4. P . 46 - 55 . Chapelle , F. H. , Lacombe, P . J. , and Bradley

, P. M. , 2012, Estimated trichloroethene transformation rates due to naturally occurring biodegradation in a fractured rock aquifer , R emediation, doi : 10.1002/rem.21307 . Chartrand , M. M. G. , Morrill P . L. , Lacrampe - Couloume , G. , and Sherwood - Lollar , B. , 2005, Stable isotope evidence of biodegradation of chlorinated ethenes at a fractured bedrock site, Environmental Science and T echnology

, v. 39, p. 4848 - 4856 . Lacombe, P

. J. , 2011, Mass of chlorinated volatile organic compounds removed by pump - and - treat, naval Air W arfare Center

, We st T renton, NJ, 1996 - 2010, U.S. Geological Survey Scientific Investigations R eport 2011 - 5003, 48 p . Wilson, J. T

., 2010, Monitored natural attenuation of chlorinated solvent plumes, in Stroo , H. F ., and W ard, C. H. , eds. , In Situ Re mediation of Chlorinated Solvents, Springer , New Y ork, p. 325 - 355 . Wilson, J. T

., Kampbell , D . H. , Fe rrey , M. , Estuesta , P. , 2001, Evaluation of the protocol for natural attenuation of chlorinated solvents: Case study at the T win Cities Army Ammunition Plant, EP A/600/R - 01/025, U.S. Environmental Protection Agency , Wa shington, DC . Ya ger , R. M. , 2000, Simulated transport and biodegradation of chlorinated ethenes in a fractured dolomite aquifer near Niagara F

alls, New Y

ork, U. S. Geological survey W ater - Re sources Investigations R eport 00 - 4275, 55 p . Ya ger , R. M. , Bilotta , S. E. , Mann, C. L. , and Madsen, E. L. , 1997, Metabolic adaptation and in situ attenuation of chlorinated ethenes by naturally occurring microogranisms in a fractured dolomite aquifer near Niagara F alls, New Y

ork, Environmental Science and T

echnology

, v. 31, p. 3138 - 3147 .