Suggested Input Values for Oakland, CA Risk Assessments

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1 Suggested Input Vlues for Oklnd, CA Risk Assessments Presented elow re suggested input vlues for modeling risk from contmintion t sites in Oklnd. These vlues devite from the defult vlues employed in mny risk models; however, they re pproprite for most sites in Oklnd nd there is significnt precedence for their use. AERIAL DISPERSION PARAMETERS Tle 1 presents suggested Oklnd vlues for residentil nd commercil lnd use scenrios for three prmeters relting to the eril dispersion of contminnts. Tle 1. Suggested Oklnd Vlues Relting to Aeril Dispersion Input Prmeter Residentil Commercil Building ir volume/floor re (cm 3 /cm 2 ) Indoor ir exchnge rte (s -1 ) 5.6E E-03 Wind speed in outdoor ir mixing zone (cm/s) The following susections discuss the justifiction for ech of these vlues. Building Air Volume/Floor Are The uilding ir volume divided y the floor re is the height of the ceiling. Lrger rooms llow for greter reduction in the concentrtion of chemicl in the ir. Tle 2 presents the suggested Oklnd vlues for this prmeter. Tle 2. Suggested Oklnd Vlues for Building Air Volume/Floor Are (cm 3 /cm 2 ) Lnd Use Scenrio Suggested Oklnd Vlue Residentil 229 Commercil 305 Cliforni Building Code (1998) sed on U.S. EPA (1997) delinetion of typicl ceiling heights The vlue for the residentil lnd use scenrio is sed on the minimum Cliforni Building Code (1998) requirement of seven feet, six inches for residentil structures. The vlue for the commercil lnd use scenrio ssumes n verge ceiling height of 10 feet. This vlue reflects the verge of the vlues defined y U.S. EPA (1997) s typicl for residentil (eight feet) nd commercil (12 feet), nd ccounts for commercil enterprises operting on the ground floor of older, mixed-use structures.

2 Indoor Air Exchnge Rte The indoor ir exchnge rte determines how much fresh ir from outside is exchnged with indoor ir in uildings. Tle 3 presents the suggested Oklnd vlues for this prmeter. Tle 3. Suggested Oklnd Vlues for Indoor Air Exchnge Rte (s -1 ) Lnd Use Scenrio Suggested Oklnd Vlue Residentil 5.6E-04 Commercil 1.4E-03 Shermn (1997); equls 2 ir chnges per hour Hydemn (1996); equls 5 ir chnges per hour Oklnd hs n extremely temperte climte. For residentil lnd use scenrio in Cliforni, vlue of two ir chnges per hour (ACH) is considered resonle (Shermn 1997). For commercil lnd use scenrio, vlue of five ACH is employed ecuse, when the outside temperture is etween 60 o F nd 70 o F, it is most efficient to use 100 percent fresh ir for uilding ventiltion (Hydemn 1996). Oklnd tempertures re etween 60 o F nd 70 o F during the dy for out six months of the yer (Ntionl Climtic Dt Center 1982). Wind Speed in Outdoor Air Mixing Zone Wind speed cn ffect the concentrtion of chemicl of concern in the outdoor ir through dispersion. Averge nnul wind speeds for different res of Oklnd were extrpolted from wind rose dt provided y the By Are Air Qulity Mngement District (BAAQMD, 1996). Tle 4. Loction-specific Wind Speeds in Oklnd (cm/s) West Oklnd (Sewge Tretment Plnt) Est Oklnd (Oklnd Interntionl Airport) Oklnd-Berkeley Hills (Vollmer Pek) c mesured from 4/1/92 through 3/31/93 mesured from 1/1/60 through 12/31/64 c mesured from 1/1/90 through 12/4/90 SOIL PARAMETERS There re three predominnt soil types in Oklnd: Merritt snds, sndy silts nd clyey silts. Merritt snds re mostly locted in the fltlnds re to the west of Lke Merritt. They re finegrined, silty snd with lenses of sndy cly nd cly (Rdruch 1957). Merritt snds hve low moisture content nd high permeility. Sndy silts re found throughout Oklnd. They re mde up of unconsolidted, modertely-sorted snd, silt, nd cly sediments, with oth fine-grined nd course-grined mterils. Sndy silts hve medium moisture content nd moderte permeility. Clyey silts re primrily found long the By nd estury, nd in lnd fills from those res. They my contin orgnic mterils, pety lyers nd smll lenses of snd. Clyey silts hve high moisture content nd low permeility.

3 Tle 5 presents the suggested Oklnd vlues for prmeters relted to these soil types. Tle 5. Suggested Oklnd Vlues for Soil Prmeters Input Prmeter Merritt Snds Sndy Silts Clyey Silts Cpillry fringe ir content (cm 3 /cm 3 ) Cpillry fringe wter content (cm 3 /cm 3 ) Cpillry fringe thickness (cm) F oc in soil (g/g) Groundwter mixing zone thickness (cm) ,524 Infiltrtion rte of wter through the vdose zone (cm/yr) Soil ulk density (g/cm 3 ) Soil to skin dherence fctor (mg/cm 2 ) Totl soil porosity (cm 3 /cm 3 ) Vdose zone ir content (cm 3 /cm 3 ) Vdose zone wter content (cm 3 /cm 3 ) Vdose zone thickness (cm) The following susections discuss the justifiction for ech of these vlues. Cpillry Fringe Prmeters: Air Content, Wter Content nd Thickness The cpillry fringe is the region ove the wter tle tht is completely sturted (Freeze nd Cherry 1979; Knox et l. 1993). Tle 6 presents the suggested Oklnd vlues for cpillry fringe ir content, cpillry fringe wter content nd cpillry fringe thickness. Tle 6. Suggested Oklnd Vlues for Cpillry Fringe Thickness, Wter Content nd Air Content Merritt Snds Sndy Silts Clyey Silts Input Prmeter Cpillry fringe ir content (cm 3 /cm 3 ) Cpillry fringe wter content (cm 3 /cm 3 ) Cpillry fringe thickness (cm) selected y Technicl Advisory Committee (1996) These vlues represent n verge of vlues recommended y environmentl experts with Oklnd field experience (Technicl Advisory Committee 1996). The finer the soil prticles, the less ir nd more wter is ssumed to e present in the cpillry fringe. The cpillry fringe is lso ssumed to e thicker in finer-grined soils. These ssumptions re supported y stndrd literture on the suject. Tle 7 compres the cpillry rise vlues reported y Guymon (1994) with the suggested Oklnd vlues for cpillry fringe thickness.

4 Tle 7. Comprison of Stndrd Cpillry Rise Vlues with Suggested Oklnd Vlues for Cpillry Fringe Thickness Guymon (1994) Suggested Oklnd Vlue Unconsolidted Mteril Grin size (mm) Cpillry Rise* (cm) Cpillry Thickness (cm) Medium snd Fine snd Silt (smple #1) ; 152 c Silt (smple #2) d *cpillry rise mesured fter 72 dys; ll smples were pproximtely 41% porous input vlue for Merritt snds input vlue for sndy silts c input vlue for clyey silts d still rising fter 72 dys The Oklnd vlues re conservtive ecuse they ssume tht ir is trpped in the cpillry fringe, mking it more permele to chemicls voltilizing from the groundwter. Frction Orgnic Cron in Soil Frction orgnic cron in soil plys mjor role in the ility of chemicls to sor to soil. The suggested Oklnd vlue for this prmeter ccounts for the fct tht minerl surfces, such s cly, nd electromgnetic moleculr forces lso cuse chemicls to sor, even if no orgnic cron is present (Lymn et l. 1992; Knox et l. 1993). Tle 8 presents the suggested Oklnd vlues for frction orgnic cron in soil with the ASTM (1995) defult. Tle 8. Suggested Oklnd Vlues for Frction Orgnic Cron in Soil (g/g) Merritt Snds Sndy Silts Clyey Silts Spence nd Gomez (1999) (Spence nd Gomez 1999). The soils chrcteriztion study ws performed to more ccurtely predict sorption of orgnic chemicls to soil y tking into ccount fctors other thn orgnic cron. Although F oc is known to e n importnt contriutor to sorption, it is only prtil predictor of the totl sorption tht occurs. To ddress this shortcoming, the soils chrcteriztion study mesured the prtitioning (or sorption) of dissolved-phse enzene onto the three Oklnd soil types. Once the ctul prtitioning ws mesured for enzene, n input vlue for the prmeter F oc * ws clculted for ech of the three soil types. The F oc * vlue is used to predict the vriility in the level of sorption, from one soil type to nother, for ll orgnic chemicls.

5 Groundwter Mixing Zone Thickness The thickness of the mixing zone in groundwter is used to clculte the chemicl concentrtion in groundwter t the down-grdient edge of the soil source. Tle 9 presents the suggested Oklnd vlues for groundwter mixing zone thickness. Tle 9. Suggested Oklnd Vlues for Groundwter Mixing Zone Thickness (cm) Merritt Snds Sndy Silts Clyey Silts ,524 selected y Technicl Advisory Committee (1998) The input vlue for groundwter mixing zone thickness is used to estimte the concentrtion of chemicl in groundwter extrcted from well t the down-grdient edge of the soil source. Vrying hydrulic conductivity in the three different soil types is ssumed to influence the well screen length required to extrct the sme mount of groundwter. The lower the hydrulic conductivity is, the longer the well screen length tht is required. Infiltrtion Rte of Wter through the Vdose Zone The infiltrtion rte is the mount of wter tht trvels through the vdose zone nd reches groundwter. Tle 10 presents the suggested Oklnd vlues for infiltrtion rte of wter through the vdose zone. Tle 10. Suggested Oklnd Vlues for Infiltrtion Rte (cm/yr) Merritt Snds Sndy Silts Clyey Silts 9 6 c 3 Technicl Advisory Committee (1998); equls 5 percent of verge Oklnd rinfll Technicl Advisory Committee (1998); equls 15 percent of verge Oklnd rinfll c Technicl Advisory Committee (1998); equls 10 percent of verge Oklnd rinfll The suggested Oklnd vlues, which re clculted from the verge Oklnd rinfll of 24 inches per yer (Ntionl Wether Service 1998), ssume tht infiltrtion rte is influenced y soil grin size nd permeility. Stndrd literture indictes tht these vlues re conservtive. Tle 11 compres the rnge of "rechrge" rtes reported y Wlton (1988) for res geologiclly similr to Oklnd with the

6 suggested Oklnd rtes. Tle 11. Comprison of Stndrd Rechrge Rtes with Suggested Oklnd Vlues for Infiltrtion Rte (in/yr) Wlton (1988) (Originlly sed on Heth 1982) Suggested Oklnd Vlues Region Rechrge Rte Infiltrtion Rte Western Mountin Rnges Alluvil Bsins ; 2.4 ; 1.2 c input vlue for Merritt snds (converted to inches per yer) input vlue for sndy silts (converted to inches per yer) c input vlue for clyey silts (converted to inches per yer) Soil Bulk Density The following eqution is used to clculte soil ulk density: Eqution 1. Soil Bulk Density soil ulk density = (1 totl porosity) (2.65 g/cm 3 ) Tle 12 presents the suggested Oklnd vlues for soil ulk density. Tle 12. Suggested Oklnd Vlues for Soil Bulk Density Vlues (g soil/cm 3 soil) Merritt Snds Sndy Silts Clyey Silts sed on totl soil porosity vlues selected y Technicl Advisory Committee (1996) These vlues were clculted using the totl soil porosity vlues selected y the Technicl Advisory Committee (1996). Soil Adherence Fctor The soil dherence fctor determines the mount of soil tht will stick to n individul s skin upon contct. Tle 13 presents the suggested Oklnd vlues for soil to skin dherence fctor. Tle 13. Suggested Oklnd Vlues for Soil Adherence Fctor (mg soil/cm 2 soil) Merritt Snds Sndy Silts Clyey Silts ASTM (1995) U.S. EPA (1992)

7 These vlues re conservtive nd re sed on studies reported y U.S. EPA (1992) tht show soil dherence to skin to e function of grin size. Bsed on these studies, U.S. EPA (1992) concluded tht 0.2 [mg/cm 2 ] my e the est vlue to represent n verge nd 1 [mg/cm 2 ] my e resonle upper vlue. Totl Soil Porosity, Vdose Zone Air Content nd Vdose Zone Wter Content Totl soil porosity, vdose zone ir content nd vdose zone wter content re interrelted nd re discussed here s group. Totl soil porosity is the sum of ir content nd wter content. Tle 14 presents the suggested Oklnd vlues for totl soil porosity, vdose zone wter content nd vdose zone ir content. Tle 14. Suggested Oklnd Vlues for Totl Soil Porosity, Vdose Zone Wter Content, Vdose Zone Air Content (cm 3 /cm 3 ) Merritt Snds Sndy Silts Clyey Silts Input Prmeter Totl soil porosity Vdose zone wter content Vdose zone ir content selected y Technicl Advisory Committee (1996) ASTM (1995) These vlues represent n verge of vlues recommended y environmentl experts with Oklnd field experience (Technicl Advisory Committee 1996). The vlues selected for ech soil type reflect the following considertions: (1) The totl soil porosity vlue ought to e reflective of the vdose zone in etween the source nd the uilding or the source nd the ground surfce. Low-permeility (i.e., higher-wter-content) lenses will e the limiting lyer for diffusion, nd the ir content nd wter content vlues should ccount for their presence. (2) Totl soil porosity in snd is diminished if the snd is dirty or not well-sorted ecuse the lrger pore spces fill up with smll prticles. (3) Totl soil porosity in clys increses s the cly prticle sizes decrese, resulting in greter percent volumetric wter content, nd n solute volumetric ir content tht is the sme s or lower thn tht found in clys with lrger prticle sizes. (4) Soils my e wetter in the winter nd drier in the summer. The input vlues should reflect n nnul verge. (5) Totl soil porosity is not the criticl prmeter, per se; rther, the model is driven y the vlues selected for vdose zone ir content nd vdose zone wter content. The suggested Oklnd vlues for totl soil porosity re supported y stndrd groundwter nd soils texts. Tle 15 compres the rnges of totl soil porosity vlues reported y Freeze nd Cherry (1979) with the suggested Oklnd vlues.

8 Tle 15. Comprison of Stndrd Totl Porosity Vlue Rnges for Vrious Soil Types with Suggested Oklnd Vlues (cm 3 voids/cm 3 soil) Freeze nd Cherry (1979) Suggested Oklnd Vlues Snd Silt Cly c input vlue for Merritt snds input vlue for sndy silts c input vlue for clyey silts Texts do not typiclly report stndrd vlues for ir content nd wter content in the vdose zone. Heth (1989) defines specific yield s the mount of wter in storge in the vdose zone tht drins under the influence of grvity, nd specific retention s the mount of wter tht is retined in the pore spces under the influence of grvity. Specific yield my e considered conservtive ir content vlue nd specific retention conservtive wter content vlue. Tle 16 compres the Heth (1989) vlues for specific yield nd retention with the suggested Oklnd vlues for vdose zone ir content nd vdose zone wter content, respectively. Tle 16. Comprison of Stndrd Specific Retention nd Specific Yield Vlues with Suggested Oklnd Vlues for Vdose Zone Air Content nd Vdose Zone Wter Content (cm 3 /cm 3 ) Heth (1989) Suggested Oklnd Vlues Mteril Specific Yield Specific Retention Air Content Wter Content Snd Soil Cly c 0.40 c input vlue for Merritt snds input vlue for sndy silts c input vlue for clyey silts The suggested Oklnd vlues for vdose zone ir content nd vdose zone wter content tke into considertion tht clys hold more wter nd snds less. The Oklnd vlues re conservtive ecuse the vdose zone ir content is ssumed to e on the high end of potentil vlues, which renders the vdose zone more permele to chemicls voltilizing from the soil nd groundwter.

9 Vdose Zone Thickness The thickness of the vdose zone is determined y the thickness of the cpillry fringe nd the depth to groundwter. Tle 17 presents the suggested Oklnd vlues for vdose zone thickness. Tle 17. Suggested Oklnd Vlues for Vdose Zone Thickness (cm) Merritt Snds Sndy Silts Clyey Silts clculted from vlues for cpillry fringe thickness nd depth to groundwter selected y Technicl Advisory Committee (1996) TARGET RISK LEVELS Tle 18 presents the suggested Oklnd vlue for Individul Excess Lifetime Cncer Risk. Tle 18. Suggested Oklnd Trget Risk Levels Individul Excess Lifetime Cncer Risk (IELCR) 10-5 The following susections discuss in detil the selection of, nd justifiction for, ech of the trget risk levels. Individul Excess Lifetime Cncer Risk The Oklnd Tier 2 IELCR devites from the ASTM (1995) defult ut flls within the rnge of trget risks recommended y ASTM (1995). There is considerle nd diverse support for the use of 10-5 IELCR trget level: Locl representtives of the gencies chrged with enforcing environmentl regultions in Oklnd greed unnimously to 10-5 t meeting of the ULR Progrm Technicl Advisory Committee (1996). The ULR Progrm Community Review Pnel pproved 10-5 y consensus. The Pnel consisted of Oklnd residents representing cross-section of the Oklnd community. The Pnel included individuls from: Africn Americn Development Assocition, GEI Consultnts, People United for Better Oklnd, Northern Cliforni Minority Business Opportunity Committee, Sierr Clu, Urn Hitt nd Urie & Assocites Environmentl Consulting Services. Their dditionl experience included prticiption with: Almed Nvl Air Sttion Restortion Advisory Bord, Chevron USA Refinery Community Advisory Pnel, City of Oklnd Plnning Commission, Community Assistnce Pnel for Verdese Crter Prk, Regionl Brownfields Working Group, Oklnd Army Bse Restortion Advisory Bord, Oklnd Shring the Vision, Oklnd Generl Pln Congress nd United Prents Aginst Led. The Pnel met twelve times etween Septemer 1996 nd August 1997 to review the ULR Progrm (now known s the RNUL Progrm ). In its report, Consensus Recommendtions for Implementing the Oklnd Urn Lnd Redevelopment Progrm (1997), the Pnel recommended tht: [] cncer risk level not to exceed 10-5 should e employed to clculte clenup levels, provided tht the following conditions re met: (1) the chemicls of concern t the site in question re well-known nd well-chrcterized; (2) the conservtism of the ssumptions tht re proposed for use in the ULR clenup

10 clcultions (such s those for exposure durtion, soil ingestion nd drinking wter consumption) re mintined, therey effectively reducing the risk further; (3) whenever possile, engineering controls (such s vpor rriers or sphlt cps) re considered to eliminte exposure through certin pthwys; nd (4) comprehensive nd effective pln for protecting the pulic from ny remining concentrtions of contminnts is prepred, implemented nd enforced. Stte Proposition 65 enforcement is sed on The Sfe Drinking Wter nd Toxic Enforcement Act of 1986 (Proposition 65) requires the Governor of Cliforni to pulish nnully list of chemicls known to the Stte to cuse cncer or reproductive toxicity. All persons who operte usiness tht might expose individuls to listed chemicl must give cler nd resonle wrning to such individuls, unless there is no significnt risk posed y the crcinogen(s) in question. The Stte hs defined no significnt risk s less thn one excess cse of cncer per 100,000 individuls.

11 REFERENCES Americn Industril Helth Council Exposure Fctors Sourceook. (Aville from Updte Coordintor, Americn Industril Helth Council, Suite 760, 2001 Pennsylvni Avenue, NW, Wshington, DC ) Americn Society for Testing nd Mterils Stndrd Guide to Risk-Bsed Corrective Action Applied t Petroleum Relese Sites. ASTM E Americn Society of Heting, Refrigerting, nd Air Conditioning Engineering ASHRAE Hndook: 1981 Fundmentls. By Are Air Qulity Mngement District Oklnd wind rose dt. Fcsimile to Mrk Gomez, Decemer 11. Bureu of Lor Sttistics Lor Force Sttistics Derived from the Current Popultion Survey, Wshington, D.C.: U.S. Deprtment of Lor. Clrese, E.J. nd E.J. Stnek, III A guide to interpreting soil ingestion studies II: qulittive nd quntittive evidence of soil ingestion. Regultory Toxicology nd Phrmcology (13: ). Cliforni Building Code Scrmento, CA: Cliforni Building Stndrds Commission. Cliforni Deprtment of Helth Mximum Contminnt Levels. Cliforni Environmentl Protection Agency Cliforni Cncer Potency Fctors. Office of Environmentl Helth Hzrd Assessment, Deprtment of Pesticide Regultion (DPR) nd Deprtment of Toxic Sustnces Control. City of Oklnd Oklnd Redevelopment of Neglected Urn Lnds Progrm: Guidnce (Version 2.0). Pulic Works Agency, Environmentl Services Division. Community Review Pnel, Oklnd Urn Lnd Redevelopment Progrm Consensus Recommendtions for Implementing the Oklnd Urn Lnd Redevelopment Progrm. (Aville from the City of Oklnd Environmentl Services Division.) Freeze, R.A. nd Cherry, J.A Groundwter. New Jersey: Prentice-Hll, Inc. Gomez, M.M Review of Phse II environmentl site ssessments ville in City of Oklnd Environmentl Services Division lirry. Guymon, G. L Unsturted Zone Hydrology. New Jersey: Prentice-Hll, Inc. Heth, R.C Clssifiction of Ground-wter Systems of the United Sttes. Ground Wter. Vol. 20: Bsic Ground-Wter Hydrology. Third Edition. United Sttes Government Printing Office for the USGS. (Aville from U.S. Geologicl Survey Federl Center, Box Denver, CO ) Hitt, Gerry. 199?. Howrd, P. H Hndook of Fte nd Exposure Dt for Orgnic Chemicls. Volumes I, II, nd III. Michign: Lewis Pulishers. nd W.M. Meyln Hndook of Physicl Properties of Orgnic Chemicls. Boc Rton, FL: CRC Press.

12 Hydemn, M. PG&E Energy Center Sn Frncisco Telephone converstion with Lynn Spence, Decemer. Knox, R.C., Stini, D.A., nd Cnter, L.W Susurfce Trnsport nd Fte Processes. Michign: Lewis Pulishers. Lymn, W.J., Reidy, P.J., nd Levy, B Moility nd Degrdtion of Orgnic Contminnts in Susurfce Environments. Prepred for the U.S. EPA. Michign: C. K. Smoley, Inc. Ntionl Climctic Dt Center Dily Normls of Temperture, Heting nd Cooling Degree Dys nd Precipittion Wshington: United Sttes Deprtment of Commerce. Ntionl Wether Service, Sn Frncisco By Are Oklnd Museum, Cliforni, Temperture nd Precipittion Rdruch, D Arel nd Engineering Geology of the Oklnd West Qudrngle, Cliforni. United Sttes Geologicl Survey. Regionl Wter Qulity Control Bord, Sn Frncisco By. Letter to Shermn, M. Lwrence Berkeley Lortories E-mil messge to Lynn Spence, Jnury 3. Spence, L.R. nd M.M. Gomez Oklnd Benzene Prtitioning Study: Synopsis. Aville from the City of Oklnd Environmentl Services Division. Stte of Cliforni Sfe Drinking Wter nd Toxic Enforcement Act (Cliforni Stte Proposition 65). Technicl Advisory Committee, Oklnd Urn Lnd Redevelopment Progrm Meeting, Ferury Meeting, My Meeting, Ferury 11. U.S. Environmentl Protection Agency Hzrdous Wste Tretment, Storge nd Disposl Fcilities (TSDF) Air Emission Models. EPA Office of Air nd Rdition. EPA-540/ Risk Assessment Guidnce for Superfund. Vol. I. Humn Helth Evlution Mnul (Prt A). Office of Emergency nd Remedil Response. EPA/540/1-89/ Exposure Fctors Hndook. Office of Helth nd Environmentl Assessment. EPA/600/8-89/ Derml Exposure Assessment: Principles nd Applictions. Interim Report. Office of Reserch nd Development. EPA/600/8-91/011B Hzrdous Wste Mngement System Toxicity Chrcteristics Revisions. Wshington, D.C.: US EPA. 55 FR Soil Screening Guidnce: Technicl Bckground Document. Office of Solid Wste nd Emergency Response. EPA/540/R-95/ Exposure Fctors Hndook. Office of Reserch nd Development. EPA/600/P- 95/002Fc. Wlton, W.C Prcticl Aspects of Groundwter Modeling Third Edition. Reprint: originlly pulished y Ntionl Wter Well Assocition.