A gas station $($underground storage tank; UST$)$ was detected to have a leak of BTEX $($benzene$,$ toluene, ethylbenzene, and xylenes$).$ Benzene is the contaminant of concern $($COC$)$ and its concentration in groundwater was $35$ mg$/$L $($dissolved aqueous phase$).$ The BTEX plume moves downgradient into a commercial fishery pond. The average linear velocity of groundwater is $0\mathrm{.}12$ m$/$day and the aquifer porosity is $0\mathrm{.}32.$ The aquifer has a saturated thickness of $5\mathrm{.}1$ m and the flow path into the pond $($receptor$)$ is $125$ m wide.

a$)$ Estimate the mass flux$/$loading $($kg$/$s$)$ of benzene into the pond?

b$)$ An engineering firm recommends pump$-$and$-$treat mothed as the main potential remedial approach. $($you can make reasonable assumptions if needed$)$

i$.$ Look up for EPA MCL for BTEX $($dissolved aqueous phase$)$ and mark down BTEX MCLs$.$

ii$.$ How long will it take to reach benzene MCL goal with only $1$ well is suggested $($assuming pumping at $30$ GPM$)?$

iii. If the city council requests to reach benzene MCL goal within $10$ days, how many wells should be installed?