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CR 97-212 Feasibility Report 6th Ave N~ Y p G ,c y ~~ \ 5 November 17, 1997 ~ P K ` N Council Report 97-212 Consider Feasibility Report Sixth Avenue North/Third Street North Storm Sewer Project Progosed Action. Tlris agenda item is informational. Staff and the City's consultant, RCM Associates, Inc., are still putting together information needed for the final feasibility report. Staffwill update City Council on storm sewer improvement alternatives and on the additional information needed, some of which was requested at the Nov 12'~ Council Worksession. Staff anticipates having the feasibility report ready for City Council consideration at the December Zna meeting. Overview. Several feasible alternative project designs were presented at a October 23~a public information meeting. These alternatives included: installing a 36" or 42" pipe under 6a` Avenue from 3'a Street North to 1~` Street North, lowering the street grade of 6`~ Avenue south of 3ra Street North, and any of the above options coupled with diverting storm water runoff to Eisenhower pond from an additional 59 acres of subwatershed above TH 7. Each of these alternatives have different impacts to the two local low areas - 6~' Avenue Nortb/3'a Street North and 1~ Street North/6-7~' Avenue North azea. These impacts are shown on the attached exhibits 6, 7, and 8. As mentioned above, additional information is being assembled. This information includes: • 10-year storm event impacts • The impacts of the "do-nothing" alternative • More detailed information on the impact of three additional, smaller ponding options • The irnpact at the 1~ Street North azea from current situation to any of the above improvement project alternatives • Field verification of critical elevations in the two local low areas • No~mber 7 RCM Associates letter with exhibits Steven J. Stadler, Public Works Duector November 7, 1997 ~~'~~ rieke carrolt muller ssociates, inc. ~n sneers architects land surveyors equal opportunity employer 10901 red circle dr. ost office box 130 innetonka, mn 55343-0130 (612) 935-6901 fax (612) 935-8814 w,nrvv.rcm-assoc.com Mr. Steven Stadler Public Works Director City of Hopkins 1010 First St. South Hopkins, MN 55343 Re: November 12, 1997 City Council Workshop 6th Avenue North and 3rd Avenue Street North Storm Sewer System Analysis RCM File No. 10425.01 Dear Mr. Stadler: At the October 23, 1997 inforntational meeting with the residents effected by the flooding of the 3rd Street North intersection with 6th Avenue North, six alternatives were presented to the residents as possible alternatives/solutions to the flooding problems they have been experiencing. These alternatives aze as follows: • Alternative 1 - 36" storm sewer pipe along 6th Avenue between 3rd Street and 1st Street. • Alternative 2 - 42" storm sewer pipe along 6th Avenue between 3rd Street and 1st Street. • Alternative 3 - Regrade 6tir Avenue to provide an emergency storm water overflow route from the 3rd Street intersection. • Altemative la -Alternative 1 and the construction of increased ponding capacity upstream in Eisenhower Pond. • Alternative 2a -Alternative 2 and the construction of increased ponding capacity upstream in Eisenhower Pond. • Alternative 3a -Alternative 3 and the construction of increased ponding capacity upstream in Eisenhower Pond. Enclosed aze draft exhibits which aze planned to be used in the feasibility study for your use to forward onto the City Council for their information prior to the workshop discussion. They are identified as follows: • Exhibit 1 -Existing storm sewer system and tributary drainage areas • Exhibit 2 -Proposed storm sewer pipe alternative • Exhibit 3 -Proposed 6th Street regrading alternative • Exhibit 4 -Storm water ponding study azeas • Exhibit 5 -Eisenhower Pond high water impacts • Exhibit 6 - 25 year and 100 year storm impacts at 3rd Street - Altemative 1- 36" pipe • Exhibit 7 - 25 year and 100 year storm impacts at 1st Street - Altemative 1 - 36" pipe • Exhibit 8 -Storm Sewer Analysis Summary Mr. Steven Stadler November 7, 1997 Page 2 Exhibit 1 shows the existing storm sewer system and the tributary stone water drainage azea which impacts the 6th Avenue/3rd Street/lst Street intersections during a rainfall event. Exhibit 2 identifies the location of the storm sewer pipe necessary to relieve the storm water flooding of the 3rd Street intersection. Alternatives 1 and 2 show the installation of 36" and 42" size storm sewer pipes respectively. Exhibit 3 illustrates the amount of street regrading necessary Yo relieve the 3rd Street flooding problems. Exhibit 4 shows the three azeas located upstream of the 3rd Street intersection which were reviewed for potential ponding. You will recall they included the following: • Eisenhower pond area • School yard azea in the SE quadrant of Minnetonka Mills Road and TH 7 • Pazking lot azea of Chapel View Care nursing home Exhibit 5 shows the high water impact of directing 59 additional acres of the CA watershed to the Eisenhower ponding azea. Exhibit 6 conceptually depicts the water elevation at the 3rd Street intersection with the installation of a 36" storm sewer pipe for the 25 and 100 yeaz storms. The high water determination is based on the contour information contained on the 1988 contour/physical feature maps prepared for the City by Horizons, Inc. Exhibit 7 conceptually depicts the same information as Exhibit 6 but for the lst Street. These two alternatives approximate the storm water flood elevation for the 25 and 100 yeaz storm without the Eisenhower Pond. Exhibit 8 simply summarizes the costs for the six alternatives studied and the estimated water depth at the intersections of 3rd and 1st Streets for the six alternatives. As we discussed, this information will be presented in detail to the City Council at a workshop scheduled for Wednesday, November 12, 1997. The workshop discussion will provide the City Council with the background information necessary for them to determine what information they would like to present to the public for final deternnation of the desired improvements for the problems identified by the residents of 6th Avenue. S e ely, `'~-~'~ hael PvFo P.E./L S. Manager, Municipal Department RIEKE CARROLL HULLER ASSOCIATES, INC. MPF/ka Enclosures rieke Carroll muller associates, inc. EXHIBIT - 1 EXISTING STORM SEWER SYSTEM engineers • architects. Iand surveyors I~ HOPKINS, MINNESOTA REVISIONS SHEET N0. 7 GATE FILE N0. NOV. 1997 t042S.Ot GA :r. Y, ~~ti i ..~.~~, r~11 1 ~`~ !N Z ~`1l , d 4'. N ~ ~ CFB C Kq~ Ii wi Q~ "'..^: ;f <'3 .<.3" 0 i ~1K Z1.~ G~ QI', _ .1-- ,,, _ -- _L i L c O Q ~ ~ n ~» SR ` ~~ , ~~ ~V '• `~ ~r ~0~ Q 2J W W, ~i G ;1 C `` a ~ ST~ It y ~ Ist ~2" 1 ~ gpnT r A p Pork ~~ ^~-, ~~~ 8 ~A i QI,, N , E ~ .~ a ';J ay) 1 ~rl /,. n~ ~ SNEET NC r ~, ~~ REVlS10N`~ ~ 1A EXFiIB~T _ 1 A ~' GE AREAS FILE NC Y pRA1NA PATE 1042` TRIBUTAR NOV. 1997 ~gPKltsS, MIN1`~E.SOTA rieke EXHIBIT - 2 REVISIONS SHEET N0. Carroll '~~ muller PROPOSED STORM SEWER 2 associates, inc. PIPE ALTERNATIVE engineers .architects • land surveyors HOPKNS, MINNESOTA DATE FILE N0. NOV. 1997 10425.01 rieke EXHIBIT - 3 REVISIONS SHEET N0. carrot l ", mutter PROPOSED 6th STREET s assodctes, inc. REGRADING ALTERNATIVE engineers • architects • land surveyors HOPKINS, MINNESOTA DATE FILE N0. NOV. 1997 10425.01 ~' ~~11~ fieke EXHIBIT - 4 REVISIONS SHEEP NO. Carroll muller STORM WATER PONDING 4 °ss°°'°tes, '"°~ STUDY AREAS engineers • architects • land surveyors HOPKINS MINNESOTA DATE FILE N0. ~ NOV. 1997 10425.01 w w o 0 o ~ o h ~\ o X 951.9 X 950.6 C 949 X 946 `950 ~~948.3~1 '~~ X X -947 4 X 948.1 (947.2 X 948.1 - rieke ca rroll Muller associates, inc. engineers • architects • land surveyors 13 948.3 24 EXHIBIT - 5 REVISIONS SHEEP N0. 5 EISENHOWER POND HIGH WATER IMPACTS DATE FILE N0. HOPKINS, MINNESOTA Nov.lss~ 10425.01 iii ~~ i ~ ~ `~ Z ~~ ~ Y, 929.8 3rd STREET ORTH X 923.8 w Q f~ rrrrma ~Ea~I~~~~~~~~ 925.6 X ~\~ "~ ~ ~ u~Ld -x 6~' ~,Y 924.7 X I~ ~-- 930.2 0 X 926.5 w z w peke EXHIBIT 6 - 36" STORM SEWER REVISIONS SHEEP NO. Carroll '~~ mu~~er - 25 YEAR WATER LEVEL 6 associates, inc. - 100 YEAR WATER LEVEL engineers • architects• land surveyors HOPKNS, MINNESOTA DATE FILE N0. NOV. 1997 10425.01 ~~ III ~ III ~~I 92 8 X illy- /} . ~ ~l I _.I 93C 4.9 (ll~ X X s !1111 `y~l ~ 1?~~~ II~ ~II I \ I I ~~~\ rieke EXHIBIT 7 - 36" STORM SEWER REVISIONS SHEET NO. Carroll '~~ sslociotes, inc. - 25 YEAR WATER LEVEL 7 - 100 YEAR WATER LEVEL engineers • architects. land surveyors HOPKNS, MINNESOTA DATE FILE N0. NOV. 1997 10425.01 ~ ~ ~' ~, ~ ~ •~ S .~ ~ ~ ~' A w 3 ~ °' v ~ ~ °~ ~ v ' o ~ ~ ~ ,~ ~ ~ ~ ~ v v+ N y 0 ~ O p^ .f ^ n ~!' M .f~ d w, ~ .n t., m ~ ~' ~ ~ ~ . `a3 ~, '.i^„ ~ d ~ 6 ~ s o h . ~ ~ O ~~ O a ~ ~ ~ v a . s ~ '`~ 6 ~ °' x d ~, o. a ~ ~' w , P+ ~ y ~ ~' ~i ui N CG ~` Gh ~O C ~ M ~ ~ M ~~ t~1 ~ a z ~ N ~ M y~ GG y ~, ~ r •~^ ~ ~ S a .o vi ~ ~ : ~o y G : ~ • ~ w ~ ., Y~ ~~ d m