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February 18, 2003
I ~lm Susan Regional Pond Reconstruction (File # SWMP 12-X)
BACKGROUND
The Lake Susan Regional Pond was identified in ~ 1994 Surface Water
Mm~lggment Phm ($W2VlP) a~ an i ~n~ortant ws~' ~ pond t~ provide
Izcatment for storm water before it ente~ Lake Such. P~t l~-oject~ f-or Lake
fish removal and a lakescaping project to ~ the lakeshorc. This project
will focus on i .m!m~ving the water quality of the water cnteaing the laim by
upgrading an existing storm water pond.
The Ixmd is located on City tgope~ in Lake Susan Park east of Powers
Boulevard and south of T_~. DfiY¢, just upstxcam of Lake Susan. The pond is
identified in thc SWMP as Pond I~P3.34 (Attachment 1). This is the final
pond to provide w~tey quality txcatment for appmxim~ly 782 acres of land
POWERS Olq~I~ BUR~ING
In lieu of providing on-site stem w~t~ pondinl~ the deveJope~ of the Powers
Office Building (in the ~azthea~ corner of Tnmk Highway 5 ami Powem
Boulevard) proposed tl~ the storm wamr from that ~ite be routed m the L~ke
$20,~00 for construction coets and $16280 for the land mqu.h'cd to expand the
Powers Office Building site and the Lake Susan Regional Pond was in place
prior to the development of the site, so storm water runoff is currently routed
to the regional pond. Because the regional pond was not built to the capaci~
pmpmed in the SWMP, the pond mu~t be mc. oared-ted in order t~ properly
treat runoff from ti~ Powers Office Building ~i~
The City d Caa01msma · A oroak~ can~ wflh dean ia~ qmilty acl~ a d~ d0mdm~ hlvino Ix~ ein~ t~ and ~ ~ A Om p~ ~ ~ ~ ~ ~
Todd Gerhardt
ps? 2 of 4
~IdRFACE WATER MANA~ PLAN
The pond was enviaioned in the SWMP as a two-ceil wm~' quality pond (two pond~
separated by a submerged berm). Its current configuration is as a one-cell pond (aingle
pond). The ~ project would create a second cell, thus brin~-g the pond into
~ with ~ SWMP (Attac~ 2).
Two-celled ponds ~mploy ~ suff-~e ~ and volum~ to _acco,~. 'hsh th~ same
level of treatment ~ one-celled ponds ~ walrr goes fi'om a completely mi,xxi
si~,,~ion in a 1-celled pond to a plug-flow si~_ ,talon in a 2-celled pond. The submerged
tire scUfing of sediment in the fi_rst cell. Thc second cell then ~ settles out scditmnt.
Scdim~t alone is consickncd a pollutant, but ntmient~ also combine with the suspended
seditmat. Allowing sediments to settle also rcmoves nutrients prior to reaching Lake
Susan.
This pond is responsible for removing 40~ of thc phosphorous contributed fi'om thc
walrmhed. 'I'ne pond, as constnLeted in 1990, is very close to nvecting the proposed
conditions for the second cell of the planned design, but thc propotu~ first ocli of the
pond was never consUuct~ This project wiI1 add the fn~ cell to thc poud. In addition,
the pond has been in operation for over 10 yea~. In that time, sediment ~ to have
filled approximstely 4.2 ac're-feel of the w_sh~- quality storage volume (polld depth)
originally provided, nearly a 23% decrease from thc volume constructed in 1990.
The reduction in water quality volume (pond depth) results in reduced phosph~
ren~val efficiencies. ~'n¢ pond removes 43.4 ton/ye, ar less total phoq~horous thnn when
it wns constructed, and 107 lbs/year le~s thnn what was ~ in the 1994 SWMP.
This mpreseots and increased loading to ~ Susan that is over 11% higher than
int~ad~ in thc 1994 SWMP. 'I'nis project will restore the treatment requirements
proposed in thc SWMP by:. 1. Removing accumulamd sediment within the existing cell;
2. Expanding the existing pond; and 3. ConsI:n~ing a submm'gr, d berm to ct'~ate a two-
ccllcd pond. Thc ~ pond design is project~ to remove an additional 99.7 lbs/year
total phosphorous when ~ to its existing condition. This should help to meet the
goals of reducing the hype~-eutrophic (extnm~ nlgae) conditions and thus ~nlly
increase the water clarity of Lake Susan.
The complete plans and specifications for this project are avnilabl¢ for review at City
I-Inll,
Todd Gerhardt
Lake Susan Regional Park Pond Reconmuc'fion
Febru~ 18,2003
1:~? 3 of 4
An area t~ the southwest of the proposed pond is jurisdictional wetland.- The City
comxacted with Aqnntic EcoSolufions, Inc. to perform a wetland delineation of the
project area. The proposed pond expansion will i .ml~ct 0.36 ncre~ of Type 2 (wet
meadow) wetlnnds. Tim t .m1~'t will be replnced at tl~ ~ 2:1 rntio thwugh a
withdrawal of 0.72 ncre~ from the City's wetlnnd break. This will meet the ~
of the Minnesota Wetland Conservation A~t (l~inrt~ota Ru~ 8420).
JURISDICTIONS
The R/ley-Pmgamry-Bluff Creek Walmxhed District requit~ a permit for all projects
disturbing 1 acre or mare. TheC/tyappliedfora~distdcttna'mit. Theft
was grnnted by the watm'shed district board at their February 5, 2003 meeting
(Attachment 3). One of the conditions of the permit/a that the City contact the
Minneagga Pollution Control Agency (MtK]A) rega~ling ~ testing. The City is
~y working with the MPCA in this re'ea.
FUNDING
PROPOSED TIMELINE
At this time, the project schedule is anticipated to be as follows:
Februar~ 24
February 27
March 6
Mm'ch 20
Maxch 24
March 26
Council approval of Plans and Specs
Submit advertisengat to paper
Ad~ published
Op~ Bids
Council Awards Project
Contractor given notice W ~
Todd Gerha~
February 18,2003
P~4of4
(~[Ty COUNCIL ACTION
Staff r~,om~ that City C_,ouncfl adopt th~ following motion:
1. Project location map
2. surface water M~sg~m~ Plan M~
3. SheetC1.01 of PlansforS'umnPondLSP3.34Imp~~
4. Riley-Put? _tory_ -Bluff Creek Watershed District Penn/t
Lake Susan
Storm Pond LS-P3.34
February 2003
Project SWMP-12X
lOP
Riley
Purgatory
Bluff Creek
Watershed District
Web Site: http//www, dleypuqtatorybluffcreek.~
Kn~3~tlcb & I-Idk
701 44h Av~x~ ~ ~Jlte 500
612 333-740O ~ 612 333-6958
City o~ f~mnhnga~l
7700 Maflcet Boulevard
P.O. Box 147
Chanhassen, MN 55317
crrY oF ch, ,. .,, . ..... ... :,.~
The Board of Manag~ of the RUey-~-Bluff Creek Wamrshed District 1~ mview~ the ~
taxi gnuiing ami land alt~ation Ix~mit s~plic~on u submitted to thc ]::)~zict for the ~
and ~ of at a cert/fied ~
ffyou hsve any qocn~ions reganflng the cond~cns of the District's pen~t, plemm call usst
952-832-2600.
~CO.
R~-PUROA~3~ RY-BLUFF Cl~ WA~ DISTRI~
c: Paul I-/aik
Howard Petersan
J'ohn Smyth Bom~J of Man,ng~B~a
Howard Pel:ei~ Perry Fc)ml:er Corlmd b Phi~ Wr~ht Su~m Scribner
General Provisions
w
At the entryway Ohm the sim, a rock filmr dike being a minlmnm of 2 feet in hdght and htvlng
maxinatm side slopes of4:l nmstbeconstmct~ This wckfilter dike will e~mble constm~m tra.ffic
RJLEY-PURGATORY~LUFF CREEK WATERSH~ DI~rRICT
GRADING AND EARTHMOVING PERMIT
ProJe~ gm-~ ~ 10 ecr~ & .Le~__ then 40 ecr~:
Fee:
F~mR ~ ~md by ~e Dl~k* on ~he 31st d~yor J='"'"~'7_ .2o. Q3~.
2O03
C.~WI~17.DOC