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2.0 Groundwater Supplies <br />"Phis section discusses the availability of groundwater supplies in the Elk River area. Groundwater <br />supplies are discussed in the context of the regional setting. Groundwater t7ows 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. These bedrock units were formed by the <br />95' <br />~t <br />l1Af~'Glti~)T.1 <br />€4 <br />t <br />~~~ , <br />,~ <br />~ • r:-"~ <br />`+-,., <br />~- .; <br />~xPt,~Nar~c~M <br />• 1 '« ~ R <br />•' ,' ; Location of northern <br />tt~lt~urc_?SI r+?<,~:onaE <br />`..'`r~~`±'~1 ,~ ~c~tatf~+r atuc:y a><rea <br />,a, w <br />~l~f~' <br />~'• .. t <br />Lo.catcon _ca._.'~it~.«srslnt <br />r <br />i;•~Jv'R~~J, I~..~, f+lt+ ~ ~ ~ - <br />tir ~4 1 <br />111 <br />8 <br />~ <br />. <br />~ ! <br />• X44 ~ '~~~~~ area <br />~ <br />. <br />~ <br />... <br />s <br />~ <br />•. vs ..¢ ! . R ~IIII <br />~ _ _ <br />• <br />~ <br />~ - s <br />{Hollandale Emb~i~°~nent) <br />~~ <br />/ <br />~~~ <br />• ~ i V , 1 • s **j~~1C ~ ~ <br /> <br />,-~.s ~ ~ ,"~i..-rr~ ~~,rR 1~..i If aR ~laar~l~~f; <br />,`{/'~~M '~ R'I ~F#~e•~~{wit <br />~y,~, • a <br />M'fi,yA~#1.~P~~ ~l~ t <br />----1~~~~~~ ` ,t ` <br />''~II'1 Z.g~flllt~'' <br />HD~ t~~~,rt7 t ` 4 4; <br />~l '[r`- -t~ ~. <br />~- ,r---r __f <br />Q 'CC 1~:IEC'v _ ~~~ <br />Figure 1 Location of the Hollandale Embayment <br />fram J,~p, and ~~~o~xhjard, 19$-t <br />deposition of marine sediments in a shallow sea about 450 to 600 million years ago. This sea covered <br />what is now Iowa, Illinois, Missouri, Indiana, lower Michigan, and southern Wisconsin. A bay of this <br />sea, called the Hollandale Embayment, extended up into southeastern and east-central Minnesota. <br />Within this bay, sea level periodically rose and fell in response to changes in climate. During periods <br />P:\Mpls\23 MN\71\23%1105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 4 <br />