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�'. � _ �'. �•M \- } ft' „y i � 4 .,\ :_ , y4.f
<br /> Mr, t�jqhnO6
<br /> qh
<br /> Project 113-2644 D_ecem!bei 16;1993
<br /> r Page 6 .
<br /> HL Conclusions and Reconunendations,
<br /> �•
<br /> Groundwater at Cheaperl Store #37 has demonstrated si cant amounts of
<br /> petroleum hydrocarbons at MW-4 for the entire monitoring year. Detectable levels
<br /> have also been found at MW-1.•The apparent source of the petroleum hydrocarbons
<br /> is the former location of the underground .-9 asoline tanks. However, an .'a• '
<br /> investigation described in an April, 20, 1993, report by Parker Environmental-,
<br /> f Services indicated high TPH-g concentrations west (upgradieri#)-of the former.tank . -
<br /> location. This could indicate an off-site source.
<br /> I# does not appear that.the petrol eum,hydrocarbanllevels 1n thesgroundwater are .
<br /> 's: y+p,,;�4yr r aa`P ..f'•n z. '� i v'`,rt , f� =n a •$
<br /> ciiminishutg::at a significant rate ydrbcarbons Increase jrthlugher.groxtincwer � n£
<br /> levels, an .� +"c",d 4 ' 4' v 4 r -7. . � �F
<br /> d ecrease with lower levels,indr tin a;contuuecset �f�:�asoe �
<br /> .y, '�4x !"f^:!moi°hdcy` rA'e�-,•.°t'v 4""S7� Fq' f r y tp
<br /> in the soils above the )-o d`whter�ttea�FMN�-�.�� U-2 �� �° � � � ���;t`"����1
<br /> V c - . 1 -� i� ^fit- �-r a; *, �'�� �:
<br /> . yt;'.r - xYii �• s ,,, a b.. a p;.`3,� t ,Hy
<br /> It Is uncertain iven the=curren#.wetl corifQ' atidn�f peirbl y i Y 'd--- `��t
<br /> `^ 0`?' - ^w. Yi.l�,rh� i VcLLL Yv1HaF
<br /> •
<br /> remaining on site or'movin o �`'} "x "� '
<br /> g . ;F,,, , ; , g off site,3 As shoe in the gasolix►e to centrahon� 4,
<br /> r�
<br /> .� ,$. 3
<br /> 3 i T,r 'e�-'f
<br /> f' f °z figure
<br /> -,,M. S dowr<gcadie�n�t:#rom they ormer_tanl�llop.? 0 1 t phi hest Y'�
<br /> I `lekq F x%h f `rF.7Y i 1Mw �}h .1j i, h.S' F'_'Y53eFty �Y r'� cYF 6"Ii
<br /> cbncenfixahon�bf 1PTi�g Thei P Co 6h
<br /> t attars north Qf VY,4 c �on y b � r ��
<br /> estimated with#he.'exist ng we n—I- --tents.ce
<br /> The Regional Water Quality Control Board and county regulators .will not allow
<br /> closure for this site ggiven the past year's sampling results. Closure rs Icall
<br /> P y� P. g tyP�..:. Y :-
<br /> f granted when-one to two years of'quarterly monitoring results are non=detect. T i
<br /> t k- Two alternative strategies for site closure"are available fox,this site. First, you can
<br /> remove the apparent source of the petroleum hydrocarbons, file sail around
<br /> t former underground gasoline tank location This would eliminate the apparent
<br /> continued release of hydrocarbons to the groundwater. Regulatory_agenries would
<br /> r .,
<br /> also require the existing hydrocarbons be removed from-the groundwater.to
<br /> minimum levels, probably requiring additional"wells and a pump=and-treat_system.
<br /> Second, a groundwater treatment system with a percolation gallery to flush the' .
<br /> E contaminated soils can be installed to remove both soil and-groundwater
<br /> contamination.
<br /> Parker Environmental Services recommends that two additional monitoring wells
<br /> be installed, one northeast of MW4, and one west of the existing tanks near Holly
<br /> Drive. This would help define any-possible on-site or off-site.petroleum
<br /> I hydrocarbon migration.
<br /> Parker Environmental Services, 190 East 7th Street, Pittsburg, CA 94565-2317
<br /> Phone (510) 439-1024 Fax (510) 439-2566
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