2e. South Lotus Lake boat access site and drainage study C I TY 0 F --
1 ii
690 COULTER DRIVE • P.O. BOX 147 • CHANHASSEN, MINNESOTA 55317
(612) 937-1900 • FAX (612) 937-5739
E" a/
IMEMORANDUM
</S/ It
TO: Park and Recreation Commission
1 FROM: Todd Hoffman, Park and Recreation Coordinator _ /, 22-'91
DATE: January 15, 1991 _-- elf -91 .__
SUBJ: South Lotus Lake Boat Access - Site and Drainage Study
Y
IIThe attached study was initiated by the City Engineering Department
in a response to citizen and staff concerns over the appearance of
II the South Lotus Lake Boat Access site. As noted in the background
section of this study, the problems at the site are a direct result
of site revisions to an adjacent development, the disastrous storm
of 1987 and the drought years that followed. Simply put, South
1 Lotus Lake Park has never developed into the beautiful facility it
should be.
1 The study outlines specific improvements which are proposed to
correct the situation. The purpose of these proposed improvements
are two fold, to upgrade the drainage and runoff systems and to
I remedy the park's unsightly appearance. This being the case, a
variety of funding sources are available for this improvement
project. These include a $5, 177.80 soil correction service grant,
$24, 000 from the environmental trust fund and a targeted amount of
I
up to $20, 000 from the Park Acquisition and Development Fund. As
the estimated project cost is $40,587.00, the Park Acquisition and
Development Fund portion of the cost would start at $11,409.20.
I Increases in this amount may occur as a result of project
additions, cost over-runs, etc.
1 This project was not addressed as part of the 1991 budgeting
process. It would therefore, be necessary to amend the 1991
Capital Improvements Program to include a transfer out of $20,000
establish a CIP Fund from which to draw from in paying the
Ito
"parks" portion of this project. I apologize for not addressing
this item as part of the 1991 budget discussions. I was aware of
the proposed improvements prior to budget work sessions but as a
1 result of my late involvement in the project was naive in regards
to the proposed funding sources. However, considering the
importance of these improvements, coupled with the availability of
I
1
11
South Lotus Lake Boat Access
January 15, 1991
Page 2
$29, 177. 80 of funding outside the "parks" budget, amending the 1991
CIP to cover these costs is recommended.
tScott Harri of VanDoren, Hazard, Stallings, Inc. will be present at
the January 22nd meeting if you have specific questions concerning
this study.
' It is recommended that the Park and Recreation Commission approve
the South Lotus Lake Boat Access site and drainage study and
' recommend that the City Council amend the Park Acquisition and
Development 1991 Capital Improvement Program to include
expenditures of up to $20, 000 as the "parks" share of this
improvement program.
' Park and Recreation Commission Action (1-22-91) : The Commission
unanimously approved the study with minor amendments (Attachment 2)
and recommended the City Council amend the 1991 Park Acquisition
and Development CIP to include expenditures of up to $20, 000 as the
"park's" share of these improvements (see attached minutes) .
Recommendation: It is recommended that the City Council approve
the South Lotus Lake Boat Access Site and Drainage Study with the
noted changes, amend the 1991 Park Acquisition and Development Fund
to include expenditures of up to $20,000 for this project and
' authorize the preparation of plans and specifications.
Park and Rec Commission Meeting 11
January 22 , 1991 - Page 31
Lash: Yeah but should that be separate from the hockey? The shingling and
then whatever is left over goes to the hockey? '
Andrews: I would consider that a friendly amendment .
Schroers: Okay , is there a second? '
Lash: Second .
Andrews moved, Lash seconded to recommend that the following improvements I
for the City Center .Park receive priority in the order listed: preparation
of master park plan, installation of play equipment, repair of tennis
courts, shingling of warming house and work on the hockey rinks. All voted'
in favor and the motion carried unanimously.
Lash: When do you feel that you 'll be coming back? '
Hoffman: Next meeting .
•
Andrews: Todd I wanted to mention , I mentioned to Wendy that last year we '
had quite, a delay between the time of ordering equipment to receiving it .
I hope we can do better this year . We ordered it , I think it was in March
and didn't get it until mid-summer and hopefully we won 't have that . . . 1
Lash: That is the standard delivery time though , 6 to 8 weeks. _
Hoffman: It depends on when your order goes in . Obviously February , '
March , April gets to be their busiest time . About a month and a half turn
around is standard on playground equipment . So we do need to get that
pu-shed forward.
SOUTH LOTUS LAKE BOAT ACCESS - SITE AND DRAINAGE STUDY.
Hoffman: Along with the report , you did have the attached study itself
that was prepared by Van Doren-Hazard-Stallings. This study was initiated
originally sometime last spring by the engineering department dealing with
the drainage issues that were occurring down at South Lotus Lake Park . How/
to correct those problems . The park never initially developed into the
facility that it should be . The grass never grew properly. The storm of
'87 or '88, whatever it was , came in and wiped out the retaining structure
at the bottom of the park itself there and then the drought years never let
the vegetation establish so the engineering department took a look at this .
Started working with Scott Harri from Van Doren-Hazard-Stallings in getting'
a plan initiated . At that time it was anticipated that the funding
sources , the outside funding sources available there to do the soil
correction , service grant and then the environmental trust fund would be
sufficient dollars to complete this project . But taking a look at the
extent of the measures which were necessary to correct the problems which
were taking place there with the additional runoff coming from the adjacent"
developments and those types of things , and the drainage structure , the
flow rate not being correct , the dollar amount started to build and as the
study indicated , their total was $40 ,587 .00 is projected to correct the
problems which currently exist and then to get that park looking into the II
state that we all wish it would be . As stated, this park was not addressed
as part of the 1991 budgeting. We did not talk about an additional
11 Park and Rec Commission Meeting
January 22 , 1991 - Page 32
$20 ,000 .00 being spent at South Lotus Lake Park for this project . I was
aware of the project prior to the budget discussions but again at that time
the project was fully in the hands of the engineering department and I was
not kept abreast of the funding situation with the transfer of my position
' and then as well the leaving of Gary Warren . Scott then called me one day
and said , you know we need to move forward and talk about how this project
is going to progress . We met with the City Manager and discussed the
funding options so it is my recommendation that we go ahead and approve the
' alteration of our 1991 budget to include a maximum $20,000.00 for this
project . The initial budget figure of $40 ,587 .00 only necessitates that we
spend $11 ,409 .00 initially but would be such a project if there 's any add
' on 's or additions as we get into the project , it could be necessary to
spend additional dollars so we just need to have those available for that
type of project . Scott is here and can address any specific questions you
' have on the study itself or how it has progressed over the past 6 or 7
months .
Schroers: Well , it just so happens that I recently attended a Clean Water
' seminar and there was a ponding section and it was maintained that most of
the ponding that goes on in municipalities , it 's basically just a hole dug
out for water retention . It 's the feeling of the people who were putting
' on the seminar that the configuration of the pondings were changed somewhat
to represent more of a funnel shape , the actual hole for the water . If it
was deeper in the center but then coming up and expanding out a little bit
more and be more gradual so as to promote more water vegetation . Plant
life which would help to purify the water and also it tends to make the
area more aesthetic and develop a small area for wildlife around the
ponding and it 's also kind of a safety factor in that cattails on marshy
' areas are kind of a deterrent for children and also that they shallowness
around the edges which promotes the plant life and the growth is also safer
from the aspect of a kid falling in to a deeper , steeper area that he
' wouldn 't be able to climb out of . Are any of those considerations in your
current plan to redo it?
Scott Harri : I guess I can concur whole heartedly I guess with your
perception and the information you received regarding what might be the
best way to design these types of storage facilities that both , I guess
clarify the water to a certain degree and also provide for a buffering of
' the rate of flow and so we don't impact downstream properties . Most of the
time in urban settings , just the physical constraints of the property and
the space involved , you know people design these ponds with I guess the
' maximum . . .you can put on things just due to the constraints of land and the
developable property . In regards to specifically your question, the lower
pond provides I guess for the best opportunity to achieve the cattail
growth . The slower and flatter sloping areas and what exists right now as
' part of our proposal is the north half of the pond from where the inlet
comes in from the upper pond and the storm sewer system toward the lake , we
propose on providing a boulder type wall along there to improve the
' aesthetics and to reduce the amount of maintenance required of weed cutting
and things . And as far as the bottom , we 're not really changing any of the
flatter areas . The area to the south or toward the hill , that area right
now has a lot of cattails growing in it . We propose really not on dredging
' or taking any of that sediment material that 's built up there . It 's got
some good nutrient and it does remove effectively a certain portion of the
nutrient loading that does come down with your smaller rainstorm washings
Park and Rec Commission Meeting
January 22 , 1991 - Page 33
so it is kind of providing for both but it doesn 't provide it entirely
around the perimeter of the pond itself . So we 're going to get some water I
quality improvement and they perhaps pointed out at the seminar that the
most harmful storm water event is when you have the light drizzle . The
first little flushes of stuff that cleans the street and gets in the storm
sewer . That 's where the most heavy nutrient from fertilizers and other
things , road salts and stuff get in there . It 's not your real gully
washers that tend to cause water quality problems . Okay . Because even the
smallest rainstorm collects the sediment and brings it down to your pond ,
and those happen quite frequently so it's the frequency of these events and
having these shallower or flatter slopes makes a lot of sense . And this
information is evolving just every year . There 's more studies done on
urban ponds . Should they be deeper? Wider? How much time you want the
water to sit in there so you can settle out the sediments so it 's something
that 's not a science . It 's kind of imperically developed over time but I I
would agree wholeheartedly and I guess half of the pond is going to serve
the purposes that at least we 're finding out in the seminar you went to .
Andrews : I just had a general comment about the ramp . I use it a lot
myself . I 'm a sailor and I go over there probably average almost once a
week and have a good idea of the kind of traffic you get . In the diagram ,
in the parking area near where it says Area #4 , that 's the area where II people when they come out off the ramp with their boat , they usually tend
to pull off to the side , tie their boats down , put covers down and so
forth . I think you need to expand an area and also curb it to keep people
off the grass there . That particular grassy area gets completed destroyed I
and I think you have to make sure that people know first of all where they
are limited to with their vehicles and secondly , to make sure they are
provided enough space so that one person can pull off and secure his boat
to take up the road while another person would tend to back in there so
maybe you 've already allowed some additional room in there from previous
but it is tight .
Scott Harri : I 'll just put a little thing on the overhead here. I think
you bring up a very good point . Our specific proposal would be in this ,
we 're talking about this queuing area where people tend to tie up once they"
pull out and right now people are driving on top of this grass island area
and it 's becoming pretty thread bare if you will from lack of any better
term . Not a lot of vegetation there and what we're proposing is to curb I
this area in front of this island and put a berm in here . A planting berm
along with putting some of the salvaged rip rap from this berm area down in
this island area here .
Andrews: There are actually people going like this, pulling off to the
right . What people tend to normally do is pull off over here .
Scott Harri : Right here? '
Andrews: Yep . Going off in the grass there and it doesn't survive very
well .
Schroers: Why are they doing that Jim? Just so other people can get
around them? ,
1
Park and Rec Commission Meeting
January 22 , 1991 - Page 34
Andrews: Yeah . I think a person's natural instinct is to pull to the
right to get out of the way and let somebody else pull in .
Schroers: Versus going up the hill and putting their stuff together up on
top?
Andrews: Well some boats , you know outboard motor boats or inboard/outdoor
boats or heavier sailboats , it 's dangerous to even take them up that little
' hill until they 're secure on the trailor . You can lose a boat off of a
trailer even up a trip that small so , and most people tend to probably do
900 of their tie down right there on the ramp and they do tend to pull off
' to the right and I think we have to provide either enough room for them to
do it adequately or to make sure they know they shouldn 't do it there and
provide another space for them to do so .
Scott Harri : There 's about room for 2 cars and trailers to pull off on the
right hand side . About . You know you get somebody real long that doesn 't
pull up far enough , then it creates some problems but in general terms
there 's almost space for 2 cars to tie down which is just enough for that
one person 's tie down . . .somebody else is pulling out . And I 've been there
when it 's been real busy and it 's a zoo down there . You know people are
trying to launch while people are coming out at the same time . But you 're
right .
Schroers: Is there a boat launch that isn 't a zoo when it 's busy?
' Koubsky: What 's the south area on Number 4 used for? Is that just green?
' Scott Harri : Yeah . Right now it was intended as a secondary collection
for storm water runoff and it was hoped at one time to provide for some
additional ponding and storage in that area and it really didn 't work out
' feasible from how fast the water kind of comes down that hill . It 's more
of a nuisance and a maintenance hassle down there . Maintenance , when we
met with them in conjunction with developing our recommendations , was in
favor of paving that area down there . Just blacktopping it right across
and we felt that maybe a middle ground of using the salvaged rip rap from
the berm . . .
' ( There was a tape change at this point in the discussion . )
Lash: So we wouldn 't have any recourse back to the developer who 's
' essentially caused a fair share of the problems isn't it?
Scott Harri : Well yeah . I think it might be that you can only look
forward but I think it would behoove us to look at the development contract
' that came about in it's final form to see if there was some provision in
there for some cost sharings or for some rehabitation. The fact that
there 's problems , the biggest challenge was . . .by the fact that just as a
' natural course of the design and development of that upper pond where the
parking lot was , that we were able to store most all of the additional
runoff that came through the Bloomberg development by just the physical
size of that existing pond and putting in a smaller say outlet pipe from
that pond . So the impact to the City was in the destruction caused during
some of these heavier rain storms in '87 and '88 , '89 , '90 type of thing
and the erosion and that kind of stuff . Now with this improvement , there 's
Park and Rec Commission Meeting
January 22 , 1991 - Page 35
11
a minimum cost to go ahead and make these improvements and their impact now
is being mitigated . So on the one hand they added a lot to the . . . '
Lash: But if they had to pay the $20 ,000 .00 instead of us , that would be
even better?
Scott Harri : That would be better , yes. Exactly.
Schroers: It would be quite difficult to put language into a contract like,
that and get a reasonable contractor to bid on it if he had to assume the
cost of something that he couldn 't control like a major rain storm causing
the erosion . I mean if you 're going to throw that back on the contractor ,
you probably wouldn 't get people submitting bids on something like that .
Hoffman: The arrangement to initially acquire the land for South Lotus
Lake Park did include a swap with that developer . Swapping the piece from I
north of North Lotus Lake Park , which we owned, for the piece for the boat
access as well so there was some cooperation on the part of the developer
to meet the City 's needs and request so there 's that aspect to look at as II
well .
Lash: The other thing I 'd be interested in is , you have an estimated time '
line that begins saying if everything went just great and I guess I 'd be
somewhat interested in us taking the direction of trying to set some kind
of realistic time lines of completion because I tend to get frustrated
when I see projects dragging on . I now some things are out of people 's
control . If it doesn 't rain and seed doesn 't take and all that kind of
stuff but I had some frustration with the completion at Lake Ann. It
seemed like it took a long time and there were a lot of delays.
Hoffman: You 're speaking specifically on the contract for the construction
job itself , the time line? Okay .
Lash: Just so we have a little more accountability . We know there is an
end and just to kind of keep everybody on track . And then I looked at the
landscaping plan and I think it looks fine but I 'm not a landscaper and I II
guess I 'm a little gun shy about putting in lots of trees and shurbs so I
just want to make sure it 's not over kill and done tastefully .
Andrews: As far as the landscaping goes , right down on the lake frontage
near the boat ramp we 've put a couple of picnic tables down and when people
are pulling their boats up on the sand . You know when they 're not taking
them out of the water but when they 're coming in for a break or whatever ,
there 's not enough room down there for that really . What I use is a
sailboard down there and there 's only room for like two guys to pull a
sailboard up on the sand and then there 's the bush and the trees are right II
there . I guess I 'd say that maybe we ought to look at less landscaping
right on the water rather than more . Especially toward , to the northwest
side of the ramp there . It 's heavily brushed and not very useable and
that 's where the picnic table was at least .
Hoffman: Scott 's comment is that the area to the west has been kind of
extended over time . Brushed it out a little bit so we can move the dock
down and gain a little bit more space over time but keeping the shurbs out
of that area and not planting a tree right onto that waterfront area is
Park and Rec Commission Meeting
January 22 , 1991 - Page 36
very adviseable . It 's just such a tight location and there 's a lot of
activity there .
' Schroers: In terms of landscaping and shurbs and planting and islands and
parking lots , isn 't some of that even Code? I know that in the City of
' Plymouth , if you 're going to build a parking lot , you have to have so much
islands per so many square foot of parking and there has to be some kind of
planting in it .
Scott Harri : The size of the islands and percentage of green space within'
the parking area is , at the time the upper parking lot was developed met
• the City ordinance and was only through the budgetary constraints that a
full landscaping package that you 're seeing in your packet right now was
originally proposed but was cut back to a minimum to satisfy the bare
minimums at the time the project was initially constructed . What this
' proposal does is it restores back to what this commission originally
approved back in 1985 .
Schroers: Is there anything in here that anyone sees that they 're not
happy with?
Andrews: One more thing . I know it 's getting late tonight but on the
upper parking lot it shows the Norway Maples and the two islands in the
parking area there . I would suggest those be removed . There 's so much
pressure up there for trailer parking space now , I guess if those were over
hanging and created any impediment to parking , you 're just reducing
available space to park and it typically is full by noon on Saturday as it
is . So if a person were to be concerned about a tree over hanging even 2
or 3 feet , that would probably eliminate one spot .
' Scott Harri : Sap and all that stuff .
Andrews: Yeah , sap too on cars or boats .
Scott Harri : A quick landscaping observation. On the lower bottom you 've
' got 6 Seedless Green Ash that evidentally the City has in their nursery . I
don 't know if the City has any pine trees. I was just wondering. There 's
two houses up on top to the south there that have to look down on this and
I 'notice they have decks and what not . Is there one reason other than the
cost that pine trees weren't considered because eventually that would block
this whole boat access off from their view off their decks . I don 't know
if they ever had any input on the aesthetics of this park or not .
' Hoffman: Sure . Yeah they have in the past . Those were put in there as a
cost saving measure . They are available . The pine trees which we have in
' our nursery are about this tall and so that 's the reasoning for it . If we
would plop it a 4 or 6 foot spruce tree , we 'd be looking at additional
couple thousand dollars at least in there .
Schroers: There 's been a lot of concerns and a lot of questions and I
think that that 's really good but it also sounds like most of them have
been answered sufficiently and it appears to me that a good amount of
' effort and good planning has gone into this and I don 't see a reason not to
approve this . Is anyone willing to make a motion?
•
Park and Rec Commission Meeting
January 22 , 1991 - Page 37
I
Lash: Do we want to , I 'm assuming that some of Jim's concerns were put
down and they 'll be added?
Hoffman: Yep . Added or subtracted from the final plan.
Andrews: I would imagine that if that steep slope on the upper lot had to II
be changed , that would be extremely expensive . If that were to be thought
necessary , I guess I would like to see this come back to us . Other than
that I think most of the other items are fairly minor in nature. '
Hoffman: If we can take a look at that and if that could be incorporated
• with part of the 1 to 2 year grading project on the lower level which is I
going to be to decrease that slope, if this potential problem could be
solved in that same vein.
Andrews: Maybe it needs nothing at all . I 'm not an expert but if it would'
need to be changed , then it would be probably add a considerable amount to
this project . I would be willing to move that we amend our budget for the
project as it 's suggested with the minor modifications but I guess I would I
feel that if the additional cost of a retaining wall system is needed on
the upper parking lot , I think I would prefer to have that come back for
further budgetary consideration.
Lash: That would almost have to wouldn't it? It 'd be a whole different .
Hoffman: Project . '
Schroers: Okay Jim , is that your motion then?
Andrews: Yes . '
Schroers: Okay . Can I ask for a second on that?
Pemrick: I 'll second it .
Andrews moved, Pemrick seconded to recommend approval of the South Lotus I
Lake Boat Access Site and Drainage study with the noted changes and to
amend the 1991 Capital Improvement Program to include expenditures up to
$20,000.00 as the Park and Recreation Department's share of the project.
All voted in favor and the motion carried unanimously.
LAKE ANN PARK COMMUNITY PARK SHELTER.
Hoffman: Again another Capital Improvement item which has been floating '
around for a number of years and has been discussed and plans have been
taken a look at and those types of things . It is a project which was
discussed as part of the CIP. City Council approved it and now we must
move forward with the plans and the design work which needs to- be completed
prior to the construction sometime in the summer of 1991 . The attachments
you have available to you are the initial sketch plans which were done as
part of discussion approximately 3 years ago . 2 years ago. 2 to 3 years
ago and then as well a site location map which showed a proposed picnic
shelter location inbetween the lower parking lot to turn around and then
down to the beach area . Minutes from the March 27 , 1990 Park and
Recreation Commission meeting are also attached . That is the last time the
1
I
ATTACHMENT 2
t Amendments to the South Lotus Lake Boat Access Site and Drainage
Study as recommended by the City Council.
1. Ensure a completion date is included as a condition of the
construction contract.
2 . Minimize landscaping near the lake's edge to allow for
unobstructed launching and landing.
3 . No additional tree planting in the upper parking lot islands.
1
1
CITY OF CHANHASSEN,MINNESOTA
SOUTH LOTUS LAKE BOAT ACCESS
SITE & DRAINAGE STUDY
A
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tii VAN DOREN-HAZARD-STALLINGS, INC.
JANUARY 1991
1 VanDoren
Hazard
IStallings,Inc.
Architects • Engineers • Planners
1
January 10, 1991
1
1
Mr. Todd Hoffman
' Park & Recreation Coordinator
City of Chanhassen
690 Coulter Drive
I P. 0. Box 147
Chanhassen, MN 55317
II Ref: South Lotus Lake Boat Access
Site and Drainage Study
VHS Project No. 90-312
1 Dear Todd:
We are pleased to present to you the results of our study concerning
I storm water collection and detention, erosion protection and
landscaping enhancements to the area. The study was prepared in
accordance with our proposal.
I BACKGROUND
II The boat access site is a steeply sloped area with a ramp and access
on the steep grade. A parking area was constructed adjacent to the
access on top of the hill. Two storm water detention ponds were
designed into the project to control runoff and sedimentation. The
I disastrous storm during the summer of 1987 caused extensive erosion
damage to the ponds and slopes of the recently completed project.
Then the drought years followed which prevented a satisfactory ground
II cover to establish itself on the steep sloped areas resulting in
continued erosion and unsightly conditions. As a consequence the City
has been faced with abnormally high maintenance costs and area
II resident complaints. The rainfall amounts of this past summer has
allowed a satisfactory ground cover to establish itself in most areas
but some erosion still persists.
I The storm water collection and detention system was initially designed
to handle the runoff from a 5.8 acre area. Review of current
topographic information shows an area of 8.9 acres now drains through
I the system. Revisions to development plans on the Bloomberg site
added 2 .0 acres with 1. 1 acres of area added to the site on the east
side of the access road. This additional area has caused the
detention ponds to frequently overflow causing erosion and sediment
I depositions throughout the project area.
patterns are shown on Drawing No. 1. The present drainage
I3030 Harbor Lane North, Bldg. II, Suite 104, Minneapolis Minnesota 55447-2175 (612) 553-1950
' One additional item of background information needs to be pointed out.
Budget constraints at the time of construction for the initial work
resulted in minimal landscaping improvements. We have included
recommendations for some landscaping to enhance the appearance of the
boat access and related parking areas for both users and area
residences consistent with related improvements at other park
facilities in the City.
ANALYSIS & RECOMMENDATIONS
Visual site observations were made in conjunction with the study of
present topographic plans and the original drainage design. The
visual observations showed the following:
1. Site vegetation is satisfactory in most locations. Some small
areas have bare ground with erosion channels. Unsightly weeds
exist around the perimeter of the lower pond next to well
maintained private property.
2 . Surface runoff on or adjoining paved areas shows erosion where
bituminous curbs have been reduced by snow removal equipment.
3. Vehicular movements have strayed off pavements causing
Ivegetation kill and subsequent erosion.
4 . The outlet structures in the storm sewer ponds are battered and
essentially non functional due to excessive storms and the fact
' that the outlet structures weren't designed to handle the larger
drainage area flows.
' 5. Appears that some runoff is bypassing catch basins on the steep
drive area during high intensity storms and causing erosion
downstream.
' Our review of the present topography of the watershed compared to the
original watershed showed an increase of 3. 1 acres of area flowing
through the watershed as explained in the background section. To
' accommodate the additional flow and meet the sedimentation and storage
requirements for a 10 year and 100 year storm respectfully, we propose
to reduce the upper pond outflow rate to lessen the impact of inflow
' to the lower pond by the lake. This seems to be a feasible solution
to the problem of the lack of storage in the lower pond. By reducing
the outflow rate of the upper pond, a greater storage capacity is
' needed. The additional storage capacity for the upper pond can be met
within this ponds present geometry. An orifice is proposed in the
existing outlet pipe to restrict the flow and a new baffle weir
structure needs to be constructed. The new weir is necessary due to
' the 10 year storm detention elevation being higher and the poor
condition of the present weir structure. A small portion of the
existing parking lot will be flooded to a depth of six (6) inches
' during the 100 year storm. Any additional inflow occurring at high
water elevation will overflow to the north down the boat access drive.
See Drawing No. 2 - Area #1 for location.
A new outlet structure is proposed for the lower pond due to the
increased area contributing flow to this pond. The structure will
consist of a 24 inch RCP riser with a 12 inch RCP outlet. A hooded
baffle structure will sit atop the riser to provide debris and
sediment control for the 10 year storm. Adequate storage capacity
exists with the present geometry of the pond. General cleanup and
reshaping of the north one-half is required. We recommend that the
sides of the regraded pond be constructed of field stone boulder wall
for three reasons, 1) the steep side slopes make vegetation nearly
impossible to grow thus the sides are continually eroding, 2 ) to
reduced maintenance and maintenance costs and 3) visually more
' pleasing than grouted rip rap or similar materials. The pond would
have an emergency spillway for storm events exceeding a 100 year
frequency. Location shown as Area #3 on Drawing No. 2.
' The east slope adjoining the boat access is extremely steep and
exceeds the practical limits for maintenance equipment currently owned
by the City. We recommend additional fill material be placed at this
1 location to soften the steepness and allow the slope to be maintained.
The additional fill could come from surplus excavated materials
generated on various roadway or other development projects occurring
1 in the vicinity of the site. This work can proceed independent from
the work described in the following recommendations. A master grading
plan is needed to guide future fill placement.
' Although the study focus was centered upon the two ponds a number of
lessor items were also evaluated. Our recommendations for these are
as follows: (Refer to Drawing No. 2 for locations)
' 1. Top dress bare spots and seed with erosion mats. Area #5 and
#6.
2. Construct high capacity inlets along the steep access drive to
collect surface runoff into the pipe system. This will reduce
11 downstream erosion. Area #2.
3. Restore island area at north end of boat access to include
gravel shoulder material, concrete curb and rip rap. This area
' is eroding severely and the eroded soil is draining into the
lower pond. Area #4.
4 . Widen the boat access 2 feet in the area adjoining the concrete
ramp. This will eliminate erosion caused by vehicles driving
off the pavement.
5. Place concrete barrier curb at upper island radius and add berm
to west side to control storm runoff and unauthorized parking.
Area #4 .
' 6. Add landscape materials to selected locations around the parking
lot, access drive and detention ponds to improve the visual
' image consistent with parks at other locations in the City and
provide screening and buffering to the neighboring properties.
See Drawing No. 3 and 4. Green Ash deciduous trees from the
City tree farm are proposed as a means of cost savings. We
assume the City will plant the trees.
I
I
II ESTIMATE OF PROBABLE COST
I Estimated Unit Estimated
Item
Quantity Cost Cost
II 1. Remove and reconstruct upper
pond baffle and outlet control. Lump Sum =$ 2,000.00
1 2 . Regrade and clean upper pond. 20 CY @ 7.00/CY = 140.00
3. Sod with 4 inches topsoil at
upper pond. 400 SY @ 3.25/SY = 1,300.00
I4 . Catch basins. 2 EA @ 1,500/EA = 3,000.00
II5. 12" RCP. 20 LF @ 20.00/LF = 400.00
6. Connect to existing CB's. 2 EA @ 700/EA = 1,400.00
II7. Top dress, seed & mulch. 1850 SY @ 0.20/SY = 370.00
8. Wood fiber blankets. 1180 SY @ 1.05/SY = 1,240.00
II9. Restore Boat Access Island
with rip rap and concrete curb. Lump Sum = 1,950.00
II10. Dredge and regrade pond bottom
and slopes of lower pond. 120 CY @ 7 .00/CY = 840.00
II11. Field Stone Boulder Wall. 9455 SF @ 10.00/SF = 9,455.00
12 . Outlet Structure-Lower Pond Lump Sum = 4 ,000.00
11 13. Sod with 4 inches topsoil at
lower pond 300 SY @ 3.25/SY 975.00
II14 . Landscaping Lump Sum = 2,700.00
TOTAL ESTIMATED CONSTRUCTION COST =$29,770.00
IIContingency ( 10%) = 2,977 .00
Plans, Specifications
IIBidding, Staking and Inspection = 7,840.00
TOTAL ESTIMATED PROJECT COST $40,587.00
II
I
II
II
I
' FINANCING
The proposed project can be funded from the following sources:
1. Soil Conservation Service Grant $ 5, 177.80
2. Environmental Trust Fund 24,000.00
' 3. Park Acquisition and Development Fund (up to) 20,000.00
TOTAL SOURCES OF FUNDS $49, 177 .80
Compared to the estimated project cost of $40,587 .00, there appears
to be a surplus of funds which could be used at this park site or for
' other park purposes.
SCHEDULE
The preliminary project schedule is proposed as follows:
Item Date
Park & Recreation Commission Meeting January 22 , 1991
City Council - Authorize Plans & Specs February 11, 1991
City Council - Accept Plans and Authorize
Ad for Bids March 11, 1991
City Council - Award Bids April 8, 1991
Begin Construction May 6, 1991
Complete Construction June 14, 1991
' The schedule illustrates the earliest construction period feasible.
We recommend proceeding with this schedule to allow the longest
growing time possible for turf establishment.
11 We appreciate the opportunity to prepare this study for the South
Lotus Lake boat access. We will be available to meet with you, the
Park and Recreation Commission and City Council to discuss our
findings and recommendations at your convenience.
Sincerely,
11 VAN DOREN-HAZARD-STALLINGS, INC.
R. Scott Harri, P.E.
' RSH/ev
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Job No. 90-312
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Date: 8-10-90
5.`
/ /// // / / Job No. 90-312
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/ / / South Lotus Lake Drainage Study
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