Grannd Water Remediatin Levels

Transcription

1 TO: Marcus C. Devine, Directr FROM: Ellen Carpenter, Legal Divisin Chief DATE: July 12, 2005 SUBJECT: Grund Water Remediatin Level Interim Plicy and Technical Guidance The Plicy Review Cmmittee (PRC) have reviewed the tw dcuments referenced abve and attached t this mem. The PRC recmmends adptin f these dcuments n an Interim basis with a request that the Media Divisins implementing the dcuments cllect certain infrmatin (identified belw) in rder t evaluate the Interim Plicy ver the next year. Each Media Divisin will cllect this infrmatin ver the twelve (12) mnths, beginning August 1, 2005, and then submit a summary f the infrmatin t the Chairpersn f the Plicy Review Cmmittee. We feel that the Interim Plicy and assciated Technical Guidance will prvide the means t establish mre cnsistent grund waster remediatin levels acrss the Divisins and establish strng defensible criteria in the event the remediatin levels are challenged. Evaluatin Infrmatin # f suspected & actual GW cntaminatin events (prjects) identified) # suspected events psitively cnfirmed vs # suspected events negatively cnfirmed average length f time GW investigatin (start t Plume identificatin cmplete) # GW Strategies Prpsed # using MCLs as remediatin gal # using TI # using institutinal r engineering cntrls # using risk management t establish remediatin gals # with identified surface water interface Summary f prblems encuntered using Interim Plicy & / r Guidelines & hw they were reslved Suggestins fr imprvement Training needs identified Apprved : /s/ July 13, 2005 Date Attachments: Interim Grund Water Remediatin Levels Technical Guidance, Develpment f Grund Water Remediatin Levels 1 f 8

2 ARKANSAS DEPARTMENT OF ENVIRONMENTAL QUALITY INTERIM POLICY GROUND WATER REMEDIATION LEVELS Backgrund The Divisins respnsible fr versight f grund water remediatin activities within the Department shuld use cnsistent methds fr establishing grund water remediatin levels regardless f the media Divisin having principal respnsibility fr the actin. Plicy (INTERIM) This plicy shall apply t grund water remediatin cnducted under the jurisdictin f ADEQ. The gal shall be t prtect, enhance, and restre grund water cnditins t the maximum beneficial use t the extent technically and ecnmically feasible while maintaining cnditins that are prtective f human health and the envirnment. Until final regulatins are prmulgated by the Arkansas Pllutin Cntrl and Eclgy Cmmissin that are specific t the establishment f grund water remediatin levels, such levels will be established n a case-by-case basis. The technical guidance fr Develpment f Grund Water Remediatin Levels, attached heret, shall be utilized as the implementatin tl t guide the develpment f grund water levels in a cnsistent manner. The levels r gals fr grund water remediatin shall be established fllwing: 1. Plume characterizatin, 2. Determinatin f surce cntrl measures / best management practices t be emplyed, and 3. Evaluatin f risk t human health and the envirnment. Cnsideratin will be given t the current and reasnably anticipated future land use (grund water usage). A prpsed site remediatin plan (including grund water levels / gals) shall be made available fr a thirty (30) day public review and cmment perid. The prpsed site remediatin plan may be incrprated as part f a permit decisin, enfrcement agreement, r similar dcument. The cntent f the prpsed remediatin plan shall include the results f the site investigatin, including the grund water plume characterizatin, identificatin and summary f surce cntrl measures, and the basis fr the establishment f the prpsed grund water remediatin levels. In additin t the public ntice typically required (publicatin in the newspaper f largest circulatin in the cunty) fr permitting decisins pursuant t APC&EC Reg. N. 8, a gd faith effrt shall be made t prvide a direct ntice t all land wners and tenants that wn r lease prperty that is impacted by the grundwater cntaminatin plume. Divisins will require that the party respnsible fr the grund water cntaminatin bear the respnsibility and csts f all investigatin, remedial feasibility studies, public participatin, and remedial implementatin when such parties can be identified. 2 f 8

3 TECHNICAL GUIDANCE DEVELOPMENT OF GROUND WATER REMEDIATION LEVELS I. Statement f Purpse This dcument prvides fr the applicatin f a cnsistent prcess fr the establishment f grund water remediatin levels r gals. ADEQ will utilize this prcess unless mdified by the Directr based n the best interest f the citizens f Arkansas. This dcument utlines the basic cmpnents ADEQ will require during the investigatin and remediatin f grund water cntaminatin regardless f the surce f the cntaminatin. II. Definitins Best Management Practices (BMPs) Schedules f activities, prhibited activities, maintenance prcedures and management practices that prevent r reduce pllutin f waters f the state. Eclgical Hazard Qutient A qutient used t assess risk in which prtective assumptins are used. Generally, the numeratr is the reasnable wrst-case cnstituent cncentratin at the pint f expsure (e.g., Expsure Estimate), and the denminatr is the n-adverse effects-based txicity reference value (e.g., Effects Benchmark). Engineering Cntrls Engineered structures, such as a clay cap, French drain, r slurry wall that is designed and installed t cntain r minimize cntaminated grund water migratin. Extent f Cntaminatin The maximum hrizntal and vertical limits f grund water pllutin as defined by the cncentratin f chemical cnstituents abve backgrund cncentratins. Grund Water Cntaminatin Pllutin [as defined at A.C.A (6)] f any waters f the state belw the surface f the grund. Hazard Index (HI) The sum f hazard qutients used in the evaluatin f nn-cancer human health risk. Hazard Qutient (HQ) Nn-cancer human health risk expressin based n the calculated expsure f a single cntaminant in a single medium divided by the reference dse. Institutinal Cntrls (IC) Nn-engineered instruments, such as administrative and/r legal cntrls that minimize the ptential fr human expsures t cntaminatin by limiting land r resurce use. Maximum Beneficial Grund Water Use The maximum (r highest) beneficial grund water, within the range f reasnably expected uses. Maximum Cntaminant Levels (MCLs) Federally prmulgated and enfrceable standards that set frth the maximum permissible level f a cntaminant in water which delivered t any user f a public water system. Maximum Cntaminant Level Gals (MCLGs) Nn-enfrceable public health gals which establish the maximum level f a cntaminant in drinking water at which n knwn r anticipated adverse human health effect wuld ccur, and which allws fr an adequate margin f safety. Pint f Cmpliance The pint r bundary at which grund water shuld be mnitred fr quality and where grund water remediatin levels are t be achieved. The vertical surface, extending dwnward t the 3 f 8

4 uppermst aquifer, lcated hrizntally and, hydraulically dwn gradient f the cntaminant surce. (Nte: Multiple pints f cmpliance may be established when respnding t cmplex r extensive grund water cntaminatin events, e.g. when shrt-term prtectin gals r interim measures are incrprated int a remediatin plan.) Remediatin Criteria All site specific respnse bjectives including details f remediatin, e.g. sil cleanup levels, institutinal cntrls, engineering cntrls, surface water discharge requirements, grund water cleanup levels, etc. Surce Cntrl Any remedial actin, interim measure, r institutinal cntrl designed t prevent, eliminate, r cntain the migratin f pllutin frm its initial pint f dispsal r entry int the envirnment. III. Prcess 1) The gal fr the use f this guidance shall be t prtect, enhance, and restre grund water cnditins t the maximum beneficial use t the extent technically and ecnmically feasible while maintaining cnditins that are prtective f human health and the envirnment. It is the plicy f ADEQ that, until final regulatins are prmulgated by the Arkansas Pllutin Cntrl and Eclgy Cmmissin that are specific t the establishment f grund water cleanup standards, the cleanup levels r gals will be established n a case-by-case basis in a cnsistent manner. T this end, the prcess set frth belw shall be utilized by ADEQ: (a) Plume characterizatin The grund water pllutin (cntaminatin) plume shall be fully characterized as t: 1. The extent f cntaminatin, 2. The cntaminatin surce(s), 3. Grund water flw directin, 4. Grund water gradient, 5. Grund water velcities, 6. Hydrgelgic units r frmatins impacted, and 7. Hydrlgic cnnectivity between units. (b) Surce Cntrl Measures / Best Management Practices Technlgical, chemical, r bilgical methds (r cmbinatins theref) must be implemented t cntrl the cntinued migratin f pllutin frm the surce. The fllwing hierarchy shall be utilized, t the extent practicable, when selecting apprpriate surce cntrl measures / practices: 1. Remval (excavatin), 2. Physical barriers 3. In situ treatment (Nte: All surce cntrl measures / best management practices must be implemented with apprpriate and adequate fllw-n mnitring t determine the effectiveness f the measures.) (c) Grund Water Cleanup Strategy The grund water remediatin levels shall be established fllwing: 1. Plume characterizatin, 2. Determinatin f surce cntrl measures / BMPs t be emplyed, and 3. Evaluatin f risk t human health and the envirnment. Cnsideratin will be given t the current and reasnably anticipated future land use (including grund water usage). The party implementing the respnse t a grund water cntaminatin event shall prepare a prpsed site remediatin plan fr ADEQ review. Fllwing determinatin f technical adequacy by ADEQ, a prpsed site remediatin plan (including all remediatin criteria t be applied t the site) shall be made available fr public review and cmment. Cntent f the prpsed remediatin plan shall include: 4 f 8

5 1. The results f the site investigatin, including the grund water plume characterizatin, 2. Identificatin, and summary f surce cntrl measures / BMPs, 3. The basis fr the establishment f the prpsed remediatin criteria, and 4. The minimum frequency fr ADEQ mnitring f the prgress and effectiveness f the remediatin. The prpsed site remediatin plan may be incrprated as a part f a permit decisin, enfrcement agreement, r ther similar dcument. The public ntice f the prpsed site remediatin plan shall fllw the prcedures typically required fr ADEQ permitting actins (publicatin in the newspaper f largest circulatin in the cunty). In additin, a gd faith effrt shall be made t prvide a direct ntice t all land wners and tenants that wn r lease prperty that is impacted by the grund water cntaminatin plume. ADEQ shall cnsider all relevant cmments submitted during the cmment perid, revise the remediatin plan as apprpriate, prepare a Respnse t Cmments, and issue a final decisin regarding the site remediatin plan. 2) Grund Water Remediatin Criteria Establishment Remediatin criteria fr prtectin f human health shuld use existing regulatry standards (e.g., drinking water standards) when such are available and necessary t prtect a current r reasnably anticipated future grund water use. Other factrs that must be cnsidered when develping site-specific grund water remediatin criteria include: Backgrund Grund Water Quality the quality f the grund water in prximity t the site that is unaffected by the release. Maximum Beneficial Grund Water Use within the range f reasnably expected uses, the maximum (r highest) beneficial grund water use warrants the mst stringent grund water cleanup levels. Grund Water Use Designatin use designatin as established by the Arkansas Sil and Water Cnservatin Cmmissin and / r the APC&EC. Actual Grund Water Use use(s) f grund water being emplyed in the immediate vicinity f the site r study area. Maximum Cntaminate Levels (MCLs) / Maximum Cntaminate Level Gals (MCLGs) Grund Water Discharge t Surface Water Best Management Practices Technical Feasibility achievement f the prpsed cleanup levels / gals practicable frm an engineering perspective. Human Health and Envirnmental Risk actual and ptential relative risk t human health and ecsystems based n expsure pathway(s) and cnstituents available fr expsure. Pint f Cmpliance 3) Acceptable Risk Range This guidance des nt require the use f a specific risk assessment methdlgy. Hwever, any risk assessment apprach that is utilized must: 1. Identify the Cnstituents f Cncern (CCs); 5 f 8

6 2. Establish the txicity f each CC; 3. Identify and evaluate all ptential and actual Expsure Pathways; 4. Identify all ptential and actual Receptrs (human health and eclgical); and 5. Evaluate the ptential and actual effects r CC expsures n each receptr. Remediatin levels fr prtectin f human health shuld use existing regulatry standards (e.g., drinking water standards) when such are available and necessary t prtect a current r reasnably anticipated future grund water use. If prmulgated standards are nt utilized fr establishing the remediatin criteria, a risk assessment will be cnducted r utilized t evaluate and establish acceptable risk management-based remediatin criteria. In the absence f existing, prmulgated standards r in cases where the designated use differs frm the actual r reasnably anticipated use; the remediatin standard may be based n an acceptable risk range. The acceptable risk range shall be based n prtectin f human health and the envirnment. Remediatin levels established fr human health prtectin will be based n cncentratins that represent an excess upper bund lifetime risk (fr knwn r suspected carcingens) between 10-4 and In additin, nn-cancer risk shall be based n levels f cntaminants that are equal t r belw a HQ f 1; r, fr sites with multiple cntaminants, a HI equal t r belw 1. Remediatin levels established fr eclgical prtectin will be based n cncentratins that represent an eclgical risk characterizatin abve an eclgical HQ rati. Typically, a HQ r HI shuld be less than This level is cnservatively chsen t accunt fr expsures due t backgrund cnditins (i.e., naturally ccurring substances like metals and surces f reginal pllutin). If the HQ r HI is greater than 0.25, a mre detailed eclgical risk assessment may be needed t better define the ptential risk, if any. IV. Tracking and Mnitring All remedies that establish grund water levels r gals abve backgrund quality shall be reviewed by the ADEQ Divisin verseeing the grund water remediatin (at a minimum) nce every five (5) years frm the date f remedy implementatin. The purpse f these reviews is t determine if remedy / grund water cleanup levels remain prtective f human health and the envirnment. The review will als dcument the status f any IC required by the remedy selectin. All ICs that are implemented as part f a remedy selectin will be recrded in a data base (t be established r identified). Until such time as an IC Tracking data base is established, each Divisin cnducting r verseeing grund water remediatin shall dcument, at a minimum, the fllwing infrmatin: Site r Prject Name Legal Descriptin (including latitude / lngitude crdinates) AFIN Cnstituents f Cncern Type f IC Required Party respnsible fr maintaining the IC V. Inter- / Intra-Agency Crdinatin The establishment f grund water remediatin levels r gals is a prcess that must be highly crdinated due t the layers f authrities and jurisdictinal issues. All ADEQ Divisins charged with the versight and / r respnse t issues f grund water cntaminatin shall cmmunicate and crdinate with the apprpriate 6 f 8

7 ADEQ Divisin(s) and / r ther State Agencies t insure that apprpriate and legally defensible levels are established. Belw is a summary t be used as a guide fr prper crdinatin n grund water remediatin levels issues: Arkansas Sil and Water Cmmissin Grund water use designatin, nn-pint surce issues. Arkansas Department f Health Human-health expsures. ADEQ Water Divisin Water quality, discharge criteria. ADEQ Hazardus Waste Divisin Hazardus substance / hazardus waste issues, risk assessment / risk management assistance. ADEQ Regulated Strage Tank Divisin Petrleum nly grund water cntaminatin issues. ADEQ Envirnmental Preservatin Divisin Review f all envirnmental prjects (including remedy decisins). 7 f 8

8 GROUND WATER CONTAMINATION IDENTIFIED INVESTIGATION PHASE / PLUME IDENTIFICATION Surce identificatin Chemical characterizatin Rate & extent GW flw directin, gradient, velcities Hydrgelgic units id Hydrlgic cnnectivity Drinking water well impacts Surface water interface id Backgrund gw quality Existing gw use id Pathway / receptr id SOURCE CONTROLS / BMPsDETERMINED & IMPLEMENTED SITE REMEDIATION PLAN / GW STRATEGY PROPOSED Reg 2 / TMDL interface MCLs / MCLGs id Establish pint(s) f cmpliance Reasnably anticipated future gw use id Risk assessment / risk management TI evaluatin ICs id Cleanup ptins / BMPs evaluated PUBLIC PARTICIPATION Ntice t land wner / tenant Legal ntice Respnse t cmments Incrprate revisins t remediatin plan 8 f 8 FINAL DECISION / IMPLEMENTATION