ARCHIVED REPORTS XR0000247 - Laserfiche WebLink

Home Browse Search

• T5 ESTIMATED MASS OF TPH-g A BENZENE IN GROUNDWATER CALTRANS-STOCKTON YARD MAINTENANCE STATION,STOCKTON,CALIFORNIA FEBRUARY 2000 AREA,VOLUME,AND MASS OF CONTAMINANTS BASED ON ISOCONCENTRATION CONTOURS-GROUNDWATER Maxlnlurrl Mass Rased Qn Masa Based ori rls000rtcerl"tign Observed Areal Impacted Isoconcentrat)on Maximum LOV411 Average Contour Concentration Extent(Ar} Volume tVj contour(MI) Observed(MJ Mass Reference Contaminant Depth Interval(j M ma (rn*) ((-) (kg) (kg) (kg) Figure TPH-g 19 60 m sat thickness >100 pg/l. 420 1237 4 2E+06 042 17 1 1 5-7 9 60 m sat thickness I >1 000 pg1L 1 4 300 1 382 1 1 3E+06 j 128 55 34 VTo„9 Total I Total Total Mp"Dotal 54418031 17 73 1 45 Benzene 9 60 m sat thickness >1 0 pg1L 1 10 1 916 3 1E+06 00031 00031 00031 5-7 9 60 m sat thickness >10 0 pglL 29 1 745 2 5E+06 025 007 0`16 9 60 m sat thickness >1 000 l.,glL 1 270 194 6 5E+05 065 083 074 Vs„,,,,,,Total Total Total M8__.Total 6 2E+06 091 090 091 Assumptions Isoconcentration contours presented in Figure 5 7 used as basis for calculation of volume and mass of impacted groundwater Areal extent-calculated using function within Autocad Impacted Volume-Assumed a 9 60-meter(31 5 0)saturated thickness used to calculate volume from area(i e Z=9 60 m for all cases) Mass Based on Isoconcentration Contour-The mass was calculated based on the assumption that all the groundwater within a given isoconcentration contour was impacted at that given concentration(i a the groundwater volume within the 1 000 pg1L contour is all impacted at 1 000 pg1L) Mass Based on Maximum Level Observed The mass was calculated based on the assumption that all the groundwater within a given isoconcentration contour was impacted at the highest concentration observed within the said isoconcentration contour (i a the groundwater volume within the 1 000 pg1L is all impacted at 4 300 pgll_) Arithmetic Mean of Mass-Total mass based on arithmetic mean of mass estimated by isoconcentration contour and mass estimated by maximum detected concentration for the respective isoconcentration interval(I a 10 0 mg/t.to 1 000 moll- and>1 000 mg/L) Key Equatlons and Constants Volume=(Area)(Saturated Thickness)_(A,)(Z) Mass of contaminant=m,=V,=A,`Z`0,Z=9 60 m A,=Estimated areal extent of contaminant in groundwater(e) Z=Saturated thickness=9 60 meters V,=volume of groundwater impacted with a given contaminant within a given isoconcentration contour(L) C,=concentration of contaminant(pglL) 0=porosity (Human Health Risk Assessment Shop 10,February 1999) m,=mass of contaminant in groundwater(kg) Total mass=Lm, Example(TPH-G>100 1491L) Ac=1 237 m' Z=9 60 m V,=1237 m''960 m'035=4200 m' Mass TPH G=(4,200 m')(1 000 1.1m)(1 00 pglL)(10°kglpg)=0 42 kg TPH-G Ml,",Total= EM,=0 42 kg+1 28 kg=17 kg Page 1 of 1