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2.0 Groundwater Supplies <br />This section discusses the availability of groundwater supplies in the 81k River area. Groundwater <br />supplies are discussed in the context of the regional setting. Groundwater flows through bedrock and <br />through surficial sand and gravel deposits. Therefore, we have included a description of the geology <br />of the area in this section. <br />2.1 Regional Geologic Setting <br />The Twin Cities metro area is situated above a relatively thick sequence of permeable bedrock units <br />that extend south into Iowa and east into Wisconsin.'Chese bedrock units were formed by the <br /> ~~, y.l. Fem.. <br />I •- _ /'uk.K~.r~f:~rr m EXFLANA710[V <br /> wro~rscn.~ ~-^. ._ •._.~-'Ll' <br /> ~~ <br />-~ .~.~''~' <br />,~~'• t; %=_I <br />p` <br />r: <br /> <br />~_--. <br />LGCatlon o{ northern <br />IT`~I. Wk' <br />j~ fk'(~:f}Pt <br />S~ <br /> , <br />~ . <br />. <br /> <br /> ~~~~~1 ~ <br /> '• I' ~ <br />~ ~ <br />.. - -L.9CJtlUA oS at~a i11 k:547.1.6. <br /> 1 <br />~a ~ <br />~• <br />~. ~ ~ ~' atu)y area <br /> ~ <br />r v <br />its ~}` ~ ' ~~ ,' <br />'; <br />~ <br />(Holland,ile Embayment) <br /> `, ,, l~ <br />~r1 <br />, <br /> ,., <br />.\.,..,. ,-f-lS .~ <br />. ~. - <br />~= ~ -' <br />~ r <br />1 I _, ~ ` __~...a ~. ~.._ r <br />9-~ Y l rCj i q~,pl <br />~~_.> t <br />0 fC h.llf;'v_ !h <br />Figure 1 Location of the Hollandale Embayment <br />from I?.c~uu and «'oad~-•ard, 19Ra ', <br />__ _ _~ <br />deposition of marine sediments in a shallow sea about 450 [0 600 million years ago. This sea covered <br />what is now Iowa, Illinois, Missouri, Indiana, lower Michigan, and southern Wisconsin. A bay of [his <br />sea, called the Hollandale 8mbayment, extended up into southeastern and east-central Minnesota. <br />Within this bay, sea level periodically rose and Cell in response to changes in climate. During periods <br />p:AMpls~23 bINVlA2371105 Water Supply Alternative SLUdyV~inalUcliver'abler'AAtlema[ivu_Repon finel.doc 4 <br />