2006-11-21_REVISION - M1982015

• Permit No: M1982015
• IBM Index Class Name: Revision
• Doc Date: 11/21/2006
• Doc Name: Request
• From: Applegate Group, Inc.
• To: DRMS
• Type & Sequence: TR2
• Media Type: D
• Archive: No

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November 21, 2006. ~ ' ~ ~ ;
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Mr. Carl"Mount ~~~ 2 ~ ~C~ L~_ .,
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Senior Environmental Protection Specialist -
~ ` ` Colarado Division of Reclamaflon Minerals and Geolo Divis:cn r o,
1313 Sherman Street,"Room"2T5 ~ ~ - ~-" Ni ' - -" ~ v_
Deader, CO 80203
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13E:. Technical Revision for Carma Ba shore;"LLC '/ ~~ / " It
~ DMG Permit No. M-1982-015; AflM~- /(
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"Dear Carl,,, "
On behalf of our client; Carma Bayshore, LLC (Carma), please accept the following`"technical revision" " "
information"for. reclamation perinit'number Ivt-1982-015.: As. amended, the reclamation permit allows
Carma to oonstivct a slung wall liner around the existing groundwater lakes at the.site, . This technical
' revision only affects the construction of a drain and monitoring" wells on the west and northwest portion ' '
~ of the site to preventae mounding of'graundwater between the Lakes and existing road structures.
We originally proposed to monitor groundwater Jevels prior to and after construction of the slurry wall,
and -implement mitigation measures -namely, a perimeter drain - if and when groundwater levels reaohed
an elevation of 4821 based on the monitoring data. The 4821-trigger elevation was based on the known"
water surface elevation of the existing western-most lake. (4818), and a 3=foot increase in groundwater
levels:
By letter-dated September 18; 2006 we.committed to the installation of a"drain and monitoring wells
,concurrent .with construction of the slurry wall. The purpose of this was to alleviate questions .and . "
Concerns raised by the Division. of Reclamation, IvIinetals and Geology, regarding the potential for
mounding of groundwater, and adverse'effects therefrom on surrounding structures,'
-The- specific items addressed by this technical revision are. (I) final construction plens'for the perimeter
drain; and (2) revised.irigger elevations for the purpose of evaluatitlg the effectiveness .of"the, drain as . ~
.installed. 'T'hese are described below;"
1. 'Perimeter. Drain Construction Plans - Across-section and plan view oFthe perimeter '
drain are shown on the .attached drawings: As shown:on.the drawings, the perimeter
drain will'begin along the northerti edge of the'western-most lake, continue.along.the
western side ofthe lake and daylightat the.Sr. Vraia River. ,
The drain-will begin'at an elevation of 4826; and the invert elevation at the St. Vrain
River will be 4820: The drain will be a minimum of approximately 10 feet below the
..existing grade of the highway to the west of the site"(interstate 25). This "will ensure that
"groundwater mounding will not affect the stability of the~roadway.
2. Revised.Trigger.Points - In addition to the"installation of the perimeter drain, Carma will.
`"monitor"groundwater elevations"as we originally committed o doing., I~oweder, the
" ~-1499.Wes1420th Avenue, Suite 200 ~" ~ - - : ~ ~ -- (303)452-667]•-Fax [phone]
Denver, Colorado 80234-2Zb9'" www-applegategroup.com ",