HomeMy WebLinkAbout1982/05/03 - Agenda Packet ..
� J .
/All
IL
r
v ♦ -
• O
vie,
CJi OF
RANCHO CUCANIONGA
C P.L,ANNING GOTN ' ION
t
4, AGENDA
1977 MONDAY MAY 3, 1982 7-10 F.M.
LIONS PARK C014MUNITY CENTER
9t61 EASE LINE,. RANCHO CUCAMONGA, CALIFORNIA
t
PUBLIC HEARING FOR:
TERRA VISTA PLANNED COMMUNITY AND RELATED ENVIRONMENTAL
IMPACT REPORT
I. -Pledge of Allegiance
II_ Roll Cali
Commissioner King Commissioner Sceranka
Co:mnssiouer Rempel_ Commissioner Tolstoy
III. Staff Report No. 4
A. Greenway Concepts
B. Park Concepts
C. Flood Control
D. Drainage
IV. Adjournment
,s.
CITY OF RANCHO CUCAMONGA
STAFF REPORT. ' , '
� r
`o
F
z
19777
DATE: May 3, 1982
TO: Members of the Planning Ccmwtmission
FROM: Rick Gomez, City Planner
BY: Michael Vairin, Senior Planner
SUBJECT: TERRA VISTA PLANNED COMMUNITY
STAFF REPORT NO. 4
SUMMARY: This is the fourth in a series of reports analyzing the
Terra Vista Planned Community Text and draft Environmental Impact
Report (EIR). The following analysis covers discussion on the
greenway design and concept; park locations, sizes and development;
and flood control and drainage. The greenway concept and design is
generally satisfactory, staff has made some ;uggestions and recom-
mendations. The park locations and sizes require some revision;
particularly with regards to the amount of parkland proposed and ,
the implementation for their development. The flood control and
drainage concepts present sore nr++ ideas regarding joint usage with
parks. The analysis on the parks has been provided by Bill Holley,
Director of Community Services, which is attached. The flood control
and drainage analysis was compiled by the Engineering Division and
is attached for your review.
Tonight's discussion should provide staff, applicant and consul�;ant
with enough direction on these issues that will enable the apply
cant to begin the completion of the final draft. We anticipate tc
conclude Corm ssir�n review of the text during June and July and
forward recommendations to the City Council in July or August.
TOPIC NO. 1 : GREENWAY CONCEPT AND DESIGN
One of the main elementc of Terra Vista are the greenways
throughout the Corry:-:;Ly. They are intended to be linear
parks containing wal,cways and trails which connect the
various activity centers. The greenways are classified in
two categories; (1 ) Vajor Greenways, and (2) Secondary
Greenways.
Terra Vista Planned Coimnity
Staff Report No. 4
May 3, 1982
Page 2
1 . Major Greenway: The major greenway consists of a 40' -80'
wide linear park. It.is intended to be designed to accom-
modate pedestrian paths, bicycle trails, and jogging paths.
A full conceptual plan and design of this greenway has not
been provided at this time. It is recommended that more
detailed conceptual plans are prepared and approved by the
City's Design Review Committee prior to development of the
first phase of the project. The conceptual plan should
address pathway material , plant types, lighting, design
features and recreational areas. In addition, any fencing
along the greenway should be consistent in material and
design. Details should be included in final conceptual
plan. For consistency purposes, it is recommended that
all .fencing along the greenway be installed by the devel-
oper.
2. Secondary Greenway: The plan proposes two sizes for second-
ary greenway; a 30'-40' greenway with separate pedestrian
and bicycle paths and a 12'-20' greenway with a single path.
The greenway system map does not differentiate the difference
between these two types. A precise trail plan indicating
sizes and conceptual designs _hould be prepared and approved
by the City's Design ReviEA Committee prior to construction
of first phase development. Again, all fencing along these - -
greenways should be consistent and installed by the developer.
The small greenway proposed, as small as 12 feet, is too
narrow. The concept is to provide a 6 foot path which would
leave only 3 feet on either side for landscape. This narrow-
ness does not allow for much flexability in the final design.
It is recommended that the greenways be no narrower than 20'
wide.
The text should also include some provisions for implementation
' and installation of the parks. The secondary greenways are
probably going to be installed with the development in the
immediate area. However, the major greenway is a major compo-
nent of the plan and it isn't clear when it will be installed.
The installation of the greenway and parks and the phasing
of the cveraU plan need to be adequately addressed in the
plan, Commission ideas should be made known at this time on
this issue.
c.
-7
K }
y L
Terra Vista Planned- Corviunity
Staff Report No. 4
May 3, 1982
Page 3
RECOMMENDATIONS: The following are recommended revisions to
the plan, io be incorporated into the final text.
1. A comprehensive conceptual plan for the major and secondary
greenways addressing pathway design and material , plant types,
lighting, design features, fencing, and recreational areas
shall be prepared by the developer and approved by the Design
Review Committee prior to construction of the first phase of
development.
2. Secondary greenways should be a minimum of 20 feet wide.
3. Fencinc along all greenways shall be consistent in design
and shall be installed by the developer.
4. A phasing and implementation plan for the installation of
the greenways shall be developed and contained in the final
text.
COKMISSION ACTION:
TOPIC NO. 2: THE PARK PLAN (See attached memo from Bili Holley)
COWISSION ACTION:
yt..;
y� 1
ill i�t r � � 5". _ .. ` r✓ ...!?.r
Terra Vista Planned Coatmunity
Staff Report No. 4—
May 3, 1982
Page 4
�n., CONTROL tta. Ied F Engineering)
TUPIL IYV. 3: rLVVL' vuN1ROL ZSe2 Q44Ct.�ICV .. '� crrrn
COMMISSION ACTION:
TOPIC NO. 4: DRAINAGE (See attached memo from Engineering)
COMMISSION ACTION:
CITY TOFF TR�A{{N'��CHO�� CUCAMONGA c�c
1Wl�s l!'lllRl'1ND 1. M
O
O A
F �� Z
Date: April 28, 1982
:7 19
To: Planning Commission
From: Bill Holley, Director, nSe'
ces Department
Subject: Terra Vista: The Park Plan
PREFACE
Terra Vista has progressed a long way in both tine and Positive
content since it was presented to the Municipal Advisory Council in
1977 as the "Highlands".
The purpose of this memorandum will be to discuss the current
pro.posal of the Lewis Develcpaent Company in relation to meeting
City park dedication standards, the Recreation Element of the
General P1;=, and appropriateness of location.
THE PAFK STANDARD
The Municipal Code for Rancho Cucamonga, via Ordinance 105, directs
that new residential subdivisions provide 5 acres of dedicated and
developed parkland, or an equal value of in lieu fees, or an
equivalent combination thereof, for each 1000 residents generated by
the project.
City Council, by Resolution, has established that for purposes of
implementing the park dedication and development ordinance, the
population for a dwelling shall be 3.1 persons per .alit.
The items which are the subject of the two preceding paragraphs, the
Ordinance and the Resolution, have been in the past and remain to
date, controversial and unpopular with development interests.
However, for the purpose at hand, review of the Terra Vista project
with relation to the park standards, the controversy and
unpopularity are irrelevant and nct a proper topic for discussion
within the scope of our task. It is the law and provisions must be
complied with prior to project_ approval.
The Planning Commission recently set a ceiling limit of 8,000 units
for Terra Vista, with the possibility of a density bonus for
affordable housing. This report will assume that it is the 8,000
unit count that will serve as the basis for park planning.
Increases above this base level may be handled at the individual
tract stage through directed modification and/or payment of in lieu
fees to achieve compliance.
Having now completed the necessary preamble of background
information, this s what the park requirement for Terra Vista is
established at:
"N'. "Pn "S.0
8000 x 3.1 x 5 124 acres parkland
The proponents propose 83.3 acres of public parkland and trails
within Terra Vista.
This is in deficit by 40.7 acres and the overall plan cannot be
approved until ccupliance is achieved.
The Terra Vista Plan must include a written and specific
methodology, within its text, by which 124 acres of parkland
requireirents are to be met, be it through straight dedication,
dedication and development, in lieu fees, credit for private open
space, or any combination thereof considered acceptable by the
Planninc Ccam-ission.
THE PAMfi LCCATT_ONS AND THE GENERAL PLAN
The responsibility for determining and approving the location of
public park sites rests with the City.
It is the City that is the guardian of the public trust and
interest. While special interest concerns are generally compatible
with that public interest, and those special interests can share in
meeting that public interest . the City cannot share the
"responsiL.�lity" for the decisions made in behalf of the public
interest. In locating parks, judgement must be made on what best
serves the public interest . . . if they also and coincidentally
serve the special interest, so much the better.
Toward understanding what those responsibilities are, a Park and
Recreation Element was a%icpted as an integral part of the. General
Plan, outlining Goal: and Objectives, 'implementation, and general
site locations.
It is this General Plan that serves as our guide toward developing
the City's --ecreation facilities.
Prcposed development mast react and be responsive to the General
Plan . . , and not the other way around. With that in mind, how
well does Terra Vista respond to the General Plan?
_2_
,:fyY
.rig ... .._.
SECTION 1. 11jE PARK/SCHOOL JOINT USE CONCEPT
As proposed, Terra Vista fails to fully maXi-Mize opportunities for
joint use between parks and schools as specifically called for in
the General Plan.
Elementary schools, for example, are typically shown as 10 acre
sites and parks for discussion purposes, average 5 acres. While
they may in most cases show some degree of proximity or adjacency to
one another, they are not generally configured to permit the
functional integration of design, cons*-nuct'on, public utilization,
or, maintenance.
Further, the present design fails to permit recognition of the key
feature of joint utilization . . . that is, cost reduction while
simultaneously improving joint opportunity.
For example, under the current proposal, a 10 acre school site will
have to be purchased, developed and maintained by the School
District. Of that 10 acres, approximately 7 acres will be available
for outdoor education and recess. A 5 acre park separate and apart
from the school will provide 5 acres of recreational opportunities
at a cost of maintenance for the 5 acres.
® on the other han,"., prcperly matching a 6 acre park site with a 6
acre school site, as is the case with the Etiwanda District, will
result in lowered site accrjisition, development and ongoing
maintenance costs for the District while increasing available
playfield area from 7 to 9 acres. The public recreation space will
increase from 5 acres to 9 acres with a maintenance cost for 6
acres. -- -
Similarly, the Central School District coupling a 7 acme school site
with a 6 acre park will show an increase from 7 acres of playfield
to 10 acres. Public recreation space will increase from 5 acres to
10 acres with a 6 acre maintenance factor.
As for Junior High Schools, Etiwanda awns a twenty acre site on
Rochester which may potentially have use as a Junior High. Locating
a five acre park site adjacent to that site would lend itself to the
benefits of joint use also. The current proposal conforms with that
i<Iea, and little change is required.
The Junior High School in the Central District, to the western side
of the project, does not however present this same opportunity. The
park is shown on the west side of the loop and the school on the
east. The park should be located adjacent to the school in a 5 acre
park, 15 acre school configuration.
a�
-3-
Specific Recormwnda`:Exon on Joint Use
1. Elementary school/park sites within the Etiwanda School
District shmsld be designated in a 6 acre school and 6
acre park configuration, without separation by roadway,
greenway, or trail to facilitate economy of resources,
improved design potential and increased public opportunity.
o This requires that the most northerly Elementary School
site in the Etiwanda District be reduced from 9.2 acres
by 3.2 acres and the adjacent 5.0 acre park be increased
by 1.0 acre, and reconfigured as a single use 12.0 acre
site.
o This requires that the ziost southerly elementary school
site be reduced from 10.0 acres by 4.0 acres and the
greenway park located on the north side of greenway be
shi-=ed to the south side adjacent to the school, and
reconfigured as a single use 12.0 acre site.
o The park site adjacent to the 20 acre Rochester parcel
owned currently by the Etiwanda District, is located.
and configured properly, however is to be reduced from
6.5 acres to 5.0 acres.
2. Elementary school/park sites within the Central School District
should be designated in a 7 acre school and 6 acrp park con-
figuration without separation by roa& ay, greenway, or trail,
to facilitate economy of resources, improved design potential
and increased public opportunity.
o 11"nis reauires that the most northerly elementary school
site in the Central District be reduced from 9.8 acres
by 2.8 acres and the 5.0 acre park on the north side of
the loop be relocated to the south side of the loop
adjacent to the school and increased by 1.0 acre. The
site shold then be reconfigured as a single use 13 acre
site.
o This requires that the most southerly elementary school
site be reduced from 10. 1 acres by 3.1 acres, and the
greenway park located on the north side of oreenway
be shifted to the south side adjacent to the school,
and that the noncontiguous park site located approxi-
mately 500 feet to the south of the school be shifted
north to to included in the joint use system. The
site should then be reconfigured as a single use 13
acre site.
o This requires that the Junior High school site be
reduced from 20.0 acres by 5.0 acres and the 9.8 acre
park site located on the west side of the loop road
be shifted to the east side adjacent to the school
1! -4-
and reduced £resn 9.8 acres to 5.0 acres. The .site
should then be reconfigured as a single use 20 acre
site.
Sunzrary of Joint Use Acreage
School Sites, Etiwanda. . . . . . . . . . . . . ..32 acres
Park Sites, Etiwanda. . . . . . . . . . .. . . . . .17 acres
School Sites, Central. . . . .. ..29 acres
Park Sites, Central. . . . . . . . . . . . . . . . . .17 acres
Total School. . . . . . . . . . . . . . . . . . . . . . . . .6' acres
Total Park in Joint Use. . . . . . . . . . . . . .34 acres
i
s`
SECTION 2. PARK/P.ETENTION BASINS
The Terra Vista Plan proposes to utilize park facilities as
retention/detention basins. This prectice is questionable from
several aspects. Let us examine the statements in the E.I.R.
prepared by Phillips Brandt Reddick, Inc. about Park
Retention/Detention Basins.
Page 3-29 - . .These basins create a potential maintenance and
liability problem for the City of Rancho Cucamonga.
After use of these park areas, there can be debris
left on site. Further, the retained water provides
an attractive nuisance for children in which they
can harm themselves. . ."
Maintenance problems and user safety. ..can these negative factors be
mitigated? P.B.R., Inc., offer these mitigation measures:
Page 3-35 - (The above may be mitigated by) ". . .During the
periods (1 to 10 hours) when water is in the park/
retention basins, the public should be kept away.
Two standard measures used in other areas to
accomplish this are: Post a guard at each basin
when more than two feet of water is present or
fence the park/retention basin area and lock it
when water is present. . ."
The mitigation measures as proposed, and after choosing my words
carefully, are "somewhat less than satisfactory."
To elaborate on the problems in developing parks within
retention/detention basins, you encounter: --` -
1. Desicr. Problems. Basin must be sloped toward a central
drainage relief point for expeditious evacuation of accu-
mulated water. This does not, as the plan illustrates,
lend itself to implementation as a ball diamond. It can
be done, yes, but why do that when you have a joint use
school/park complex with ball diamonds and soccer fields
within 600 feet? In other words, why create design pro-
blems which are not necessary to create?
2. Maintenance Problems. When you have water flowing or
bubbling into a tur ed park area you will receive some
siltace and sedimentation deposit. You will also receive
scm. e degree of percolation. Together, these two factors
will create a soggy, mushy surface which will be easily
subject to damage long after the basis has cleared a.ne
the users return. Consider how much wear and tear occurs
on a "healthy" park or school site from: day long soccer
usage. Then consider the impact of that same usage on a
soggy mushy surface.
-b-
Ongoing repair and maintenance will be heavier in this
situation than-would be nc -► i. '�Nhy create additional
maintenance problems when c' ,e1' are not necessary to create?
3. Safety Problem. Self explanatory.
The -rents insist that the-se prebl%=.s listed above are not
. sed on their research, We do not agree.
The .cents maintain that the occurrencas in which water would
enter the basin are irft-equent. Perhaps. ..but why invite such
.rsecessazy expos•,-e at all, %d ether it occurs only cmce every two
years, twenty years or 100 years?
Specific Recommendation on Park Retention/Detentin Basins
1. That park retention/detention basin con=ep't n^t be employed
in any park/school joint use project.
2. That the MillikeniChurch Street park retention/detention
basir. be reduced in size from 14.9 to 8.9 acres, and that
it be passive in design, and that it receive 50% credit
towards meeting project park requirements. or. . .
That the Milliken/Church Street park be eliminated entirely
and replaced by a standard retention basin.
i
J I
•rya ..
SECTION 3. TEP.RA VISTA GREENWAY AND TRAIL SYSTEM.
The Greenway and Trail as proposed is a definite asset to Terra
Vista and Une future residents of the project. Several adjustments
need to be made for improved community viability and implementation
of the preceding area covered within this report.
Specific Reccm , ndations on Greenway and Trails.
I. That approximately 6 acres of the 22.6 aces claimed along
the riajo: greenway for parks be removed from the total.
This is due to location shirting and incorporation of the
parks into the joint use concept. In reality, the green-
way will still enjoy the passive benefits of rhese areas
as proposed, only in a different location.
2. That a pedestrian bridge be constructed across Deer Creek
Channel as a continuation of the trail into the triangular
section south of Baseline. This would tie the "out" sec-
tion to the balance of the project, mitigating addition:
need for parks and eliminate the need for school busing.
3. That a pedestrian bridge be constructed across Deer Creek
Channel from the section north of Baseline into Deer.
Creek Park, mitigating need for a larger park in that
section.
Summary of Greenwav and Trail Acreage:
Greenway. . . . . . . . . . . . . .16.6 acres
Trails. . .. . . . . . . . . . . . .13.9 acres
Total. . . . . . .. . . . . . . . . .30.5 acres
i
I
1
SECTION 4, TERRA VISTA AND DEER CREEK PARK j
Deer Creek Park, is called out as a site specif .c location within the
General Plan. This park will well serve the fature pcpu=lation of
Terra Vista.
SPeci£i^_ Recommendation on Deer Creek Park
1. That Terra Vista be required to dedicate land within
Jeer Creek Park in an undeveloped state tc the City
of Ra.nch� Cucamonga in girder to fulfill its park
dedication requirements as outlined in Or< .inan. e 105.
The dedication of this land in an andevelvVed state
nets one half the requirement of Oxdinano! 105 per
acre. As you recall, the Ordinance requi -es that
the value for the requirement is establisxed at a
level for a dedicated and developed acre Df land.
The price of land on tFis piece is directLy equivalent
to park development costs. Therefore, tha park
development credit for the dedication is Listed at
35.75 acres of compliance for dedication :)f 71.5 acres
of undeveloped la.-:
1
i
I
I
I
SECTION 5. PRIVATE OPEN SPACE
Lewis Development Company can apply for up to 50% credit on private
open space, per Ordinance 105, toward meeting their park
requirements. They indicate it is their intent to do so. The figure
they propose is 36 acres of private open space, netting a credit oZ
1S acres toward their requirement.
I frankly am uncomfortable with this. Not with the credit being
available, that's the law, but with being unable to see when_ and
where it's qoina to be implemented. For example, is it going to be
applied evenly over appropriate land uses, or is it going to be held
till t2:e end for application? This seems like a "trust me"
situation without specifics to delineate the program more clearly.
Unfortunately, because the project is of such a long time duration,
and the cost of characters now involved is very likely to change
before the last improvement is finalized, "trust me" situations are
very undesirable.
Specific Recommendations on Private Open Space
I. That through the Planning Cosmission, up to 50% credit for
private open :pace be available based upon the specific
private recreational amenities proposed and calculated
upon. the standards in Ordinance 105.
For example, when a higher density development occurs which
gerarates, say, 250 individual residents, this indicates
Chat an equivalent value of 1.25 acres of developed park-
land be available for their use. One recre?tion hail
with a pool table does not meet that requi_e:rent and
therefore would not qualif;, for the full 50% credit.
2 . That the Terra Vista text show a method for implementing
the private cpcn space plan, be it a percentage, a unit
cc�_nt triggering device, or whatever manner which would
be acceptable to the Planting Cormissior..
-10-
S'_rrW-RY AND CONCLUSION
The Terra Vista Plan presents a fire "opportunity" for a quality
development in the heart of our City.
What we have presented in the preceding pages are c=cept-s on
several areas relating to ,ark and recreation amenities and our
judgement as to how those i•nprovements could be best addressed. A
recap would show the following:
PUBLIC PARK SPACE CREDIT SUMMARY
Deer Creek Park. . . . . . . . . . . . . .. . . . . . . . . .35.75 acres
Greenway. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..16.6 a :res
Trails. . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . .13.p acres
Joint Use Parks. . . . . . . . . . . . . . . . . . . . . . . .34.0 acres
Park Retentic-i/Detention Basin. . . .. . . . , 4.45 acres
Private Open Space*. . . . . . . . . . . . . . .. . .. .18.0 acres
Other. . . . . . . . . . . . . . . . .. . . . . . . . . . . .. . . . .1.3 acres
TOTAL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124.0 acres
*Lewis Development indicates it will provide 35 acres of private
open space which may be credited up to 50% per Crdinance 105.
® The 124.0 acres shown above meets Terr.- Vistas legal requirements.
What we have not discussed durinc, this concept presentation, as it
would be premature, are details on implementation. Past experience
has shown us that this must be addressed in the text for a clear
understanding by all parties involved of what, when, how and *y —
whom, the features of Terra Vista will become reality. Once the
Planning Commission has approved a "concept plan", but prior to
final approval of the entire plan, direction should be given to
staff to prepare implementation details.
If I can answer any questions left unanswered, please feel free to
give me a call at your convenience.
-li- ,
CL
3 {yam} = O U U a c.) O+ lui
ip�p!Y t
JIL
e — -
� e {, � 1 li
J
J '
1. m
o
{y
} v.
- uj
4=F�< C
e13
i
2 {
I' a '
g O 1!
21
o
m
E4 10
Ls
AIo }
nV a
J
J — O
i r r d
M-
-� 0i
OCL
co
o
rl J J I $
CITY OF RANCHO CUCAMONGA A
STAFF REPORT
DATE: May 3, 1482 Z
Z
TO: Members of the Planning Commission i977
FROM: Lloyd B. Hubbs, City Engineer
BY: Shir;tu Bose, Associate Civil Engineer
I
SUBJECT: Terra Vista Project - _Flood Control and Drainage Analysis
TOPIC: Flooa Control
Terra Vista project site is located along the divide of two major drainage
systems - Deer Creek, which traverses the northwest portion of the project and
Day Creek, which is situated approximately 1200 feet east of the project. The
site is in a flood zone and during the 1969 major storm, the site was flooded
from the overflow of Deer Creek and from the failure of the Day C-reek levee.
An exhibit to show the 1969 flood overflow area in relation to the project site
is shown below for your review.
1969 FLOOD OVERFLOW MAP p '
Since that time, the Day creek levee has been strengthened and as a part of Army
Corps of Engineer's Cucamonga Creek Pr-oject, the construction of Deer Creek
Channel improvements from Cucamonga Creek to the foothills of the aountains and
strengtheng of the west side of the levee is scheduled to be complete, by the
end of this year. With the completion of these improvement:, the principal
source of flooding to the site will be eliminated.
In the E.I.F, analysis for flood protection mitigation measures , it is stated
that some protection may be needed for the development to the eastern area of
the site due to the absence of improvement in Day creek channel . In our cpinion,
any flood hazard to the easterly area will not originate from the Day Creek
channel . Any further breakage of the levee may create some flood hazard to the
T ® continued.. .
'r
i
Planning Commission Staff Report
Terra Vista - Flood Control/Drainage Anaiysis
Page 2
easterly portion which is very unlikely after the strergthing of the levee.
However, as stated in the E.I.R. , flood protection needs will be further
reviewed at the time of the development plan preparation.
RECOMMENDATION:
Since the Army Corps of Engineers ' project to improve the Deer Creek Channel
and the portion of the Day Creek levee will eliminate the major source of
flood hazard to the site, Staff's only recommendation relative to flood
protection is that no occupancy permit to any building in the project shall
be issued until such time as the aforementioned improvements are compelted.
ACTION:
TOPIC: Drainage
The present drainage runoff of the site is tributary to both the Deer Creek and
Day Creek channels, proposed Milliken Avenue being the drainage divide between
those twu creeks.
The Developer's Engineer has prepared a :Waster plan of drainage for the project
site in consultation with the Staff, Army Corps of Engineers and the San Bernardino
County Flood Control District. A copy of the master plan is attached for your
review.
The master plan provides for draining the site by means of the internal street
systems, underground pipes and a series of detention basins. Due to the
limited capacity of Day Creek and potential flooding problem at the downstream
End in Riverside County, the master plan proposes to drain all of the project
runoff to Deer Creek except for 126 acres located east of future Milliken Avenue.
Deer Creek channel has been designed to accept runoff from Terra Vista area on
the assumption that the site will remain undeveloped and the Army Corps of
Engineers is limiting the inflow to the channel and is ailoting a flow of 430 cfs
from Terra Vista site. With the improvements and diversion of drainage area from
Day Creek, maximum peak flow that will be generated from Terra Vista for a 100 year
frequency storm is calculated to be 575 cfs, and will necessitate the need to
detain the excess runoff. The engineer is proposing to utilize the proposed
three parksites as detension basins to reduce the peak flow to Deer Creek. A
conceptual pian for the park/detention basin is attached for your review.
The concept design utilizes an underground flow through pipe across the parksite
with a bubbler structure located at a corner. When the peak inflow from the site
will exceed the alioted outflow to Deer Creek, basin inflow will occur through the
bubbler structure. As the peakflow in Deer Creek subsides, outflow from the basin
continued. . .
Planning Commission Staff Report
Terra Vista - Flood Control/Drainage Analysis
Page 3
will occur. For a smaller storm and for nuisance water, detention in the
parksite will not be required, but will ba required in severe high intensity
R storms. With proper grading, small retention of storm water may be localized
to a certain area. Maximum storage that may be required on the site will have
a depth of 4 feet for a duration of 10 hn:rs. Percolation of water in the
basin is not considered in calcuiating the duration of storage on the site.
Utilization of the parksite for detention basin is a policy decision that
needs to be addressed by the Commissioners in conjunction with the recommendation
and analysis by the Community Services Department.
The concept of utilizing parksites for stormwater detention is being used in
several municipalities. However, this system has certain disadvantages in
relation to maintenance cost and public safety. Collection of sedimentation
and debris, especially during the development stages will limit the use of the
parksite, will damage landscaping, thereby increasing the cost of maintenance
and restoration of the parksite.
To provide for public safety during the time water is present in the basin, the
E.I.R. has stated that a guard be posted at each basin or fences be installed.
Desirability of fencing will be addressed by the Community Services Department.
Cost and the feasibility of posting guards is the factor the Commissioners need
to consider in evaluating the merit of using parksite for detention purposes.
RECOMMENDATION:
Since the design of the storm drainage utilizes the park area for its proper
function, we recommend that in the event of a change in the location and/or the
size of the parksites , additional detention basins be provided, whether ir a
park or not.
ACTION:
Respectfully submitted,
Lloyd B. Hubbs
s City Engineer
By: Shintu Bose
Associate Civil Engineer
TAC3
OI m PrY
r_
p m '
9
-rm.K-- III/CIt11E11lIHttttltlllrlllllgillllir�i IIEgiC11r111itClrltl2i 1 Itf111CIL
10
_ m
mroerrm'Jar
Mr
S �+
_ P
na v I
m= 21,
9F CO
umnnln�iutcm _
•�trIIIIIl1t1,2jturM .
.1 �t _ P \ � r I •' '
V ..........
:n
lumilf
rn
i
I
O 3
r-
y m0 00
Sm 00 Z
= as 00 �
X
m
+' � 2 9
s y c
t: 3 OR
z 0
u
ca
96
NVI-MW -
jO O O O O
Uj
v
f o z C2LLJ
h z � z ! O
e O I
Adilk 3Atl t�)aT ;
1