HomeMy WebLinkAbout1.0 Revision of Final Drainage Report - Phase II, III, IVCIVIL ENGINEERING
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1517 Blake Avenue, Suite 101
Glenwood Springs, CO 81601
970.945.8676 phone
970.945.2555 fax
An Employee -Owned Company
LAND SURVEYING
REVISION OF FINAL DRAINAGE REPORT
FOR
IRONBRIDGE P. U.D.
PHASES 2, 3, and 4
GARFIELD COUNTY, COLORADO
PREPARED FOR:
LB Rose Ranch, LLC
410 Ironbridge Rd
Glenwood Springs, CO 81601
PREPARED BY:
High Country Engineering, Inc.
1517 Blake Avenue, Suite 101
Glenwood Springs, CO 81601
(970) 945-8676
Original Report Date: April 3, 2004
Revision Date: July 15, 2005
HCE JOB NUMBER: 2051019.00-0417
www.hceng.com
14 Inverness Drive East, Suite F-120
Englewood, CO 80112
303.925.0544 phone
303.925.0547 fax
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TABLE OF CONTENTS
SECTION PAGE
I. LOCATION AND DESCRIPTION OF PROPERTY
A. Property Location
B. Description of Property
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II. DRAINAGE BASINS AND SUB -BASINS LOCATION AND EVALUATION
A. Major Basin Description 4
B. Sub -Basin Description 5
C. Irrigation Facilities 6
D. Design Point Description 6
III. DRAINAGE BASIN CRITERIA
A. Regulations 20
B. Development Criteria Reference and Constraints 20
C. Hydrological Criteria 21
IV. DRAINAGE FACILITY DESIGN
A. General Concept
B. Specific Details
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V. CONCLUSIONS 23
VI. REFERENCES 24
VII APPENDIX
Exhibits
1. Vicinity Map (8.5 x 11)
2. Existing Basin Maps (24x36) — two @ 100 scale
3. Proposed Basin Maps (24x36) — five @ 50 scale
4. SCS Soils Map
5. FEMA Map (11 x 17)
6. Colorado Water Conservation Board Map (11 x 17)
7. NOAA Maps (11 x 17) x3
8. Phasing Map
Hydrologic Computations
Hydraulic Computations
Details
1. Trash Rack
2. Outlet Structure (five — 8x11)
3. Orifice Plate (On outlet structure sheets)
4. Inlet
5. Cross Pan
6. Run Down to Pond
7. Curb Cut
8. Typical Spillway Detail (2 sheets)
10. Typical Underdrain Detail
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Engineers Certification
I hereby certify that the report entitled "Revision of Final Drainage Report for Ironbridge P.U.D.
Phases 2,3, and 4, Garfield County, Colorado" dated July 15, 2005 was prepared by me or under
my direct supervision for LB Rose Ranch, LLC.
Ronald E. Weidler Jr., P.E.
Registration Number 35617
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I. LOCATION AND DESCRIPTION OF PROPERTY
A. Property Location
The proposed development, Ironbridge P.U.D., Phases 2, 3, and 4, is located in parts of Section
1, 12, and 2, Township 7 South, Range 89 West, and parts of Section 35, Township 8 South,
Range 89 West of the 6th Principal Meridian, Garfield County, Colorado. The development is
located east of County Road 109, west of the Roaring Fork River, approximately 3.5 miles
southeasterly of Glenwood Springs. A vicinity map can be seen in the Exhibit 1. The proposed
development is part of the larger Rose Ranch P.U.D.
B. Description of Property
Ironbridge P.U.D. Phases 2, 3 and 4 consist of approximately 68.5 acres. The proposed site
contains 173 single-family homes. The Robertson Irrigation Ditch flows through the site and
will not be altered during construction. An existing golf course that was constructed during the
larger Rose Ranch P.U.D. is intermixed with the proposed development. The Roaring Fork
River is located on the eastern property boundary and flows north. The site drains from west to
east and has slopes ranging from 2% to 15%.
II. DRAINAGE BASINS AND SUB -BASINS LOCATION AND EVALUATION
A. Major Basin Description
Ironbridge P.U.D. has some major contributing onsite and offsite basins that were accounted for
in the original filing. The drainage structures for these basins have been constructed. There are
no proposed changes to the basins contributing to these structures; therefore, the basins and
structures will not be discussed as part of this report. The hydrology and hydraulics are described
in `Drainage Report for Rose Ranch P.U.D.' dated April 3, 2003. Some minor contributing
basins are located west of and along County Road 109. These contributing basins are from golf
course holes #11 and #12 and surrounding areas and have been analyzed as offsite drainage
basins. These offsite drainage basins have been safely conveyed through the proposed site. The
golf course within the proposed development (hole # 14) also contributes runoff and has been
analyzed for this report. Golf course hole #10 conveys runoff to the existing major channel
running southeast then east through the site. Along the south side of the proposed development
is the existing golf course hole #13. The runoff from this area will be conveyed by the golf
course drainage system, which conveys the runoff to an existing culvert located on the existing
road and then to the Roaring Fork River.
Ironbridge P.U.D. has an existing drainage study for the proposed Affordable Housing and
Activity Center that was completed by High Country Engineering and is dated November 19,
2003. This report no longer applies to the proposed storm drainage system since it has been
redesigned in this revision. The Affordable Housing, proposed Area A, has been redesigned with
this report. The future Activity Center has been reevaluated in this report since it has also been
reconfigured. This proposed drainage report does include the future build -out of the Activity
Center to tie into the storm drain system that drains to water quality pond C.
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Roaring Fork River
The floodplain of the Roaring Fork River adjacent to the project is shown on the Garfield County
Flood Insurance Study Rate Map prepared by the Federal Emergency Management Agency
(Community Number 080205, Panel Number 1465, dated January 3, 1986). The Floodplain Map
(Exhibit #5) is a copy of a portion of the Flood Insurance Rate Map from that study which shows
the project area. The Floodplain Worksheets are a copy of the "worksheets" for the FEMA study
prepared by Simons, Li & Associates in 1983, which more clearly show the expected floodplain
and floodway. The 100 -year floodplain (water surface) elevations are shown on the Floodplain
Worksheets as wavy lines across the floodplain.
All of the building envelopes are outside of the limits for the 100 -year floodplain for the Roaring
Fork River. The minimum finished floor elevations will be shown on the final plat for the lots
that have the 100 -year floodplain on or immediately adjacent to the rear lot lines.
The Northeast Dry Park Drainage
Hydrology. The Northeast Dry Park drainage basin varies from an elevation of 7,440 feet at its
upper end to an elevation of 6,020 feet at its mouth. Stream gauge record analyses in western
Colorado' indicate that elevation 7,500 feet is approximately the dividing elevation between
rainfall derived critical flood events (below 7,500 feet) and snowmelt derived events (above
7,500 feet). This characteristic is also indicated in the Simons, Li & Associates hydrology report.
Based on these reports, the basins should be considered as governed by rainfall runoff, so the
basic hydrology of the site was performed using the SCS method.
The major contributing basins were analyzed in the previous report using a bulking factor since
they have characteristics of debris flows. These contributing basins are conveyed through
attenuation structures and settling ponds upstream of County Road 109. Since the debris flow
hazard has been dealt with, the golf course basins affecting the proposed site have been designed
for the 100 -year storm event.
B. Sub -Basin Description
The previous drainage report divided the site into basins with roadside drainage ditches and
drainage structures. These drainage ditches were utilized as water quality features as they were
routed east to the Roaring Fork River. The roadside drainage ditch design has been changed to a
curb and gutter system. The curb and gutter system does not allow for treatment like the grass -
lined ditch, so water quality ponds will treat the stormwater before discharging into the Roaring
Fork River. A summary of the existing and proposed basin characteristics can be seen in the
"Basin Hydrology" section of the appendices. The curve numbers shown in the spreadsheet were
determined using UDFCD's tables based upon building size per lot. For area's B and C, the TR -
55 Tabular Method Curve Number table was utilized.
The proposed storm drain system also utilizes an underdrain system. The underdrain system is
needed to keep all water away from the buildings to eliminate the potential for sinkholes
'"Magnitude and Frequency of Floods in the Western United States, Part 9, Colorado River Basin," U.S.
Geological Survey, 1966.
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resulting from saturation of the collapsible soils located throughout the project. The underdrain
system will be utilized on all the lots except the 28 river lots. Each lot's system will collect
water from the roofs, and back and sides of the lot. The stormwater will be conveyed to the front
of the each lot where it will tie into a lateral connected to the main storm drain system. Each lot
will have a cleanout installed along the lateral with an eight -foot stub capped for the
homeowner's tie-in. This system will be sized for each lateral with a 1% pipe slope and can be
seen in the appendix. The calculations indicated that six-inch diameter underdrain pipes should
be utilized for four 8,000 square -feet lots or less, and eight -inch diameter underdrain pipe for five
to six lots, and a ten -inch diameter underdrain pipe should be utilized for more than six lots.
Exhibit 9 shows the typical layout of the underdrain system.
The runoff from the proposed development will be conveyed by the proposed storm -drain system
to five water quality ponds before being release to the Roaring Fork River. The site does direct
release stormwater in a few locations. These include the back half of the river lots, which will
not contain road runoff River Bend Way releases stormwater to existing grass -lined swales
located at the phase line with Phase 2. The runoff from basins PR -D15 and PR -D45 is minimal
since the storm runoff above these basins will be captured by street inlets. The runoff at these
locations will be routed from the curb and gutter to the existing roadside ditch. The existing
roadside ditch will then convey the stormwater to the existing culvert. The existing culvert was
previously designed and will be sufficient to convey this flow since the contributing area is less.
The streets and curb and gutter will be designed to carry both the minor and major storm runoff
from the proposed development. The minor storm has been analyzed so that the crown of the
road will not be overtopped. The major storm has been analyzed with the water depth to be 1 -
foot above the flowline of the curb and gutter. The proposed development has two different road
cross sections; one with a 10 -foot wide lane and the other with a 12 -foot wide lane. The curb and
gutter sections are the same for each street. The street flow calculations determined by using
Flow Master can be seen in the "Routing Calculations" section of the appendices.
C. Irrigation Facilities
The existing and proposed development is located adjacent to the Robertson Irrigation Ditch.
This irrigation ditch will not affect the proposed site and the proposed site will not affect the
ditch. This can be seen in the Proposed Basin Map, Exhibit #3.
D. Design Point Descriptions (Exhibit 3)
The proposed storm drain system has two design points; pipe flow and surface runoff. The pipe
flow is needed since most of the lots will have an underdrain system, which will be piped directly
to the main storm drain system. These design points will be utilized for pipe sizing and will be
identified as the pipe name (i.e. SD -A2). The surface runoff will be analyzed at the design points
for inlet sizing and will be used to assure that the street capacity is not exceeded. These design
points will be identified with a letter and number within a rectangle. The affordable housing area
is identified as PR -A. The villas located on the northeast part of the site are identified as PR -B.
The villas located south of Ironbridge Drive are identified as PR -C, and the rest of the site is
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identified as PR -D. A design point map and a list of storm pipe sizing have been included in the
• "Storm Pipe Routing" section of the appendices.
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EXISTING CONDITIONS
EXISTING AREA BASINS (EX -A, EX -B, EX -C, EX -D1, EX -D2)
The existing basins for each pond were determined by adding all of the sub basin areas that drain
to the pond together. The basins were determined to calculate the existing 2 -year, 25 -year, and
100 -year flows for each pond area. The runoff flow rates were then used to determine the 2 -year
water surface elevation for the ponds.
DESIGN POINT A2: BASIN EX-OS1 (0.36 acres)
The basin collects runoff from the open space located along the west side of the affordable
housing area, just north of the existing clubhouse parking lot, and sheet flows to basin PR -A1.
PR -AI collects the flow and conveys it to SD -A2 through the underdrain system. The runoff
from this basin is Q25 = 0.34 cfs Qtoo = 0.80 cfs.
DESIGN POINT 0S2: BASIN EX -0S2 (0.39 acres), BASIN EX -0S3 (1.61 acres)
Basin EX -0S2 collects runoff from the open space and the golf cart path above the existing
clubhouse. The runoff flows northeast to DP-OS2 where it will be captured by proposed inlet
Inlet-OS2. The proposed inlet will convey the stormwater to SD-OS2, where it will be routed to
the main stormwater drainage system. The runoff from this basin is Q25 = 0.09 cfs Qioo = 0.19
cfs.
The basin, EX -0S3, collects runoff from the offsite buildings, clubhouse parking area and open
space. The runoff flows northeast to proposed inlet, Inlet-OS2, then to dp-M2 via a storm pipe,
where it will be routed by a proposed manhole along with EX -0S2. The proposed inlet will
convey the stormwater to SD-OS2. The runoff from this basin is Q25 = 0.60 cfs Qioo = 0.97 cfs.
The total routed flow contributing to this design point is Q25 = 0.63 cfs. This flow will be used
for the inlet design and for the SD-OS2 pipe design.
DESIGN POINT 4: BASIN EX -0S4 (1.45 acres)
The basin collects runoff from County Road 109, Ironbridge Drive, clubhouse parking area and
open space. The runoff flows northeast to DP -4, where it will be conveyed onsite to PR -A6. The
proposed inlet will convey the stormwater to SD -A6. The runoff from this basin is Q25 = 3.21 cfs
Qioo = 4.06 cfs.
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DESIGN POINT 5: BASIN EX -0S5 (0.38 acres)
The basin collects runoff from County Road 109, and Ironbridge Drive. The runoff flows
northeast to DP -5, where it will be conveyed onsite to PR -C8. The proposed inlet, Inlet -C8, will
convey the stormwater to SD -C8. The runoff from this basin is Q25 = 0.35 cfs Q1oo = 0.51 cfs.
DESIGN POINT M2: BASIN EX -0S6 (0.66 acres)
The basin collects runoff from the parking area and open space east of the clubhouse. The runoff
flows to one of two inlets located within the basin. The two inlets are piped to the north part of
the basin. The existing storm drain system will connect to the proposed system via the storm
pipe SD-OS6 that will drain to SDMH-M2. The runoff from this basin is Q25 = 0.91 cfs Qioo =-
1.20
1.20 cfs.
BASIN EX -0S7 (14.33 acres)
The basin is located west of County Road 109 and collects runoff from existing open space, golf
course and County Road 109. Golf course as -built information could not be obtained, so the
basin was delineated from the golf course storm drain design. The runoff flows to a low point
along County Road 109 where existing inlets are located on both sides of the road. The runoff is
collected and routed in existing pipes to the onsite major drainage channel within golf course
hole #10. This basin does not influence any proposed development.
DESIGN POINT 0S8: BASIN EX -0S8 (32.40 acres)
The basin is located west of County Road 109 and collects runoff from existing open space, golf
course and County Road 109. Golf course as -built information could not be obtained, so the
basin was delineated from the golf course storm drain design. The runoff flows to a low point
along County Road 109 where existing inlets are located on both sides of the road. The runoff is
collected and routed in existing pipes east to the proposed development. The proposed storm
drainage system will collect this offsite flow and route it to a proposed water quality pond via the
storm pipe, SD-OS8 where it will drain to design point SD -40. The 100 -year runoff from this
offsite basin is used to size the proposed onsite storm drain system. The runoff from this basin is
Q25 = 24.94 cfs Q1oo = 36.01 cfs.
DESIGN POINT 0S9: BASIN EX -0S9 (15.45 acres)
The basin is located west of County Road 109 and collects runoff from existing open space, golf
course and County Road 109. Golf course as -built information could not be obtained, so the
basin was delineated from the golf course storm drain design. The runoff flows to a low point
along County Road 109 where existing inlets are located on both sides of the road. The runoff is
collected and routed in existing pipes east to the proposed development. The proposed storm
drainage system will collect this offsite flow and route it to a proposed water quality pond. The
drainage is routed from SD-OS9 to design point D-40. The 100 -year runoff from this offsite
basin is used to size the proposed onsite storm drain system. The runoff from this basin is Q25 =
10.13 cfs Qioo = 15.00 cfs.
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• PROPOSED CONDITIONS
DESIGN POINT A2: BASIN PR -Al (0.78 acres)
The basin collects runoff from the proposed roofs and back of lots in the affordable housing area
into the underdrain system, UD -Al and conveys it northeast along Fox Run Court to SD -A2.
The runoff from this basin is Q25 = 0.58 cfs Q100= 0.87 cfs.
DESIGN POINT A2: BASIN PR -A2 (0.73 acres)
The basin collects runoff from the front building envelope to the centerline of the road and
conveys it to the low point along the northeast part of Fox Run Court. The inlet, Inlet -A2, will
collect the flow and convey it to SD -A2, where is will be routed to WQ Pond A. The runoff
from this basin is Q25 = 0.18 cfs Q1oo = 0.34 cfs.
DESIGN POINT A3: BASIN PR -A3 (0.27 acres)
The basin collects runoff from the front building envelope to the centerline of the road and
conveys it to the low point along the east side of Fox Run Court. The inlet, Inlet -A3, will collect
the flow and convey it to SD -A3. The runoff from this basin is Q25 = 0.38 cfs Q1oo = 0.52 cfs.
DESIGN POINT A3: BASIN PR -A4 (0.28 acres)
The basin collects runoff from the proposed roofs and back of lots in the underdrain system, UD -
A4 and conveys it north along Fox Run Court to Inlet -A3. The runoff from this basin is Q25 =
0.26 cfs Qioo = 0.37 cfs.
DESIGN POINT A5: BASIN PR -A5 (0.11 acres)
The basin collects runoff from the road and conveys it to the low point near the entrance of Fox
Run Court. The inlet will collect the flow and convey it to SD -A5, where it will then be routed
through the proposed storm drain system to WQ Pond A. The runoff from this basin is Q25 =
0.33 cfs Qioo = 0.40 cfs.
DESIGN POINT A6: BASIN PR -A6 (0.46 acres)
The basin collects runoff from the road and landscape area and conveys it to the low point near
the entrance of Fox Run Court. The inlet will collect the flow and convey it to SD -A6 where it
will be routed north to WQ Pond A. The runoff from this basin is Q25 = 0.07 cfs Qloo = 0.15 cfs.
DESIGN POINT M7: BASIN PR -A7 (2.13 acres)
The basin collects runoff from the future activity center that will be located just north of
• Ironbridge Drive. The hydrology and hydraulics have been designed for future build -out. At the
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time of the activity center construction, it will be able to tie directly into SDMH-7. The
stormwater will then be routed through the main drainage pipe system to WQ Pond C. The
runoff from this basin is Q25 = 1.51 cfs Qloo = 2.21 cfs.
DESIGN POINT A2: BASIN PR -A9 (0.50 acres)
The basin collects runoff from the proposed roofs and back of lots in the underdrain system and
conveys it southeast along Fox Run Court to SD -A2. The runoff from this basin is Q25 = 0.66 cfs
Qioo = 0.91 cfs.
DESIGN POINT A3: BASIN PR -A10 (0.27 acres)
The basin collects runoff from the proposed roofs and back of lots in the underdrain system and
conveys it northeast along Fox Run Court to SD -A3. The runoff from this basin is Q25 = 0.25 cfs
No = 0.37 cfs.
DESIGN POINT B1: BASIN PR -B1 (2.31 acres)
The basin collects runoff from the proposed streets in the north villas, River Bend Way,
Ironbridge Drive, and open space. The runoff is routed east to River Bend Way and then north to
Inlet -B 1. The inlet then routes the drainage east to WQ Pond B via SD -B 1. The runoff from this
basin is Q25 = 2.01 cfs Qioo = 2.78 cfs.
DESIGN POINT B2: BASIN PR -B2 (0.52 acres)
The basin collects runoff from the proposed roofs and rear lots located in the north villas. The
runoff is routed through the proposed underdrain system to SD-MB6. The runoff is then routed
to the main storm drain system. The main storm drain system will be routed to proposed water
quality pond B. The runoff from this basin is Q25 = 0.90 cfs Qtoo = 1.19 cfs.
DESIGN POINT B2: BASIN PR -B3 (0.70 acres)
The basin collects runoff from the proposed roofs and rear lots. The runoff is routed through the
proposed underdrain system to SD-MB6 and then to the main storm drain system. The main
storm drain system will be routed to proposed water quality pond B. The runoff from this basin
is Q25 = 0.76 cfs Q 1 oo = 1.07 cfs.
DESIGN POINT B4: BASIN PR -B4 (0.35 acres)
The basin collects runoff from the proposed roofs and rear lots. The runoff is routed through the
proposed underdrain system to SDMH-B3 where it will routed to the main storm drain system.
The main storm drain system will be routed to proposed water quality pond B. The runoff from
this basin is Q25 = 0.44 cfs QIoo = 0.60 cfs.
DESIGN POINT B5: BASIN PR -B5 (0.43 acres)
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The basin collects runoff from the proposed roofs and rear lots. The runoff is routed through the
proposed underdrain system to SDMH-B2 and then to the main storm drain system. The main
storm drain system will be routed to proposed water quality pond B. The runoff from this basin
is Q25 = 0.57 cfs Q1oo = 0.79 cfs.
DESIGN POINT B5: BASIN PR -B6 (0.25 acres)
The basin collects runoff from the proposed roofs and rear lots. The runoff is routed through the
proposed underdrain system to SDMH-B2 and then to the main storm drain system. The main
storm drain system will be routed to proposed water quality pond B. The runoff from this basin
is Q25 = 0.34 cfs Qioo = 0.46 cfs.
DESIGN POINT SD -POND B: BASIN PR -B7 (2.26 acres)
The basin collects runoff from the proposed building fronts, roadway and open space. The runoff
is routed west to the curb and gutter on the east side of River Bend Way and then north offsite to
proposed water quality pond B. The runoff from this basin is Q25 = 0.22 cfs Qum = 0.49 cfs.
BASIN PR -B8 (4.09 acres)
The basin collects runoff from the proposed back half of the river lots located on the east side of
River Bend Way. The runoff will sheet flow east to the Roaring Fork River. The runoff from
this basin is Q25 = 0.11 cfs Qioo = 0.24 cfs.
DESIGN POINT Cl: BASIN PR -C1 (0.72 acres)
The basin collects runoff from the proposed street and buildings along the south side of
Ironbridge Drive and conveys it along the south side of Ironbridge Drive to Inlet -CI . The inlet
will collect the flow and convey it to SDMH-MC6. The runoff from this basin is Q25 = 0.30 cfs
Qioo = 0.54 cfs.
DESIGN POINT C3: BASIN PR -C2 (0.35 acres)
The basin collects runoff from the proposed buildings, open space and roadway. The runoff is
routed to Ironbridge Drive via sheet flow. The flow draining from the back of the buildings and
the lots will be captured in an underdrain system that will be routed through Inlet -C3 to SD -C3.
The sheet flow will be captured in the curb and gutter system along Ironbridge drive to Inlet -C8,
where it will then be routed to proposed water quality pond C along with the runoff captured in
the underdrain system. The runoff from this basin is Q25 = 0.11 cfs Qioo = 0.20 cfs.
DESIGN POINT C3: BASIN PR -C3 (0.58 acres)
The basin collects runoff from the proposed buildings, rear lots and the driveway. The runoff is
routed through a proposed underdrain system that ties into the main storm drain system at Inlet -
C3. The main storm drain system will be routed to the proposed water quality pond C. The
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runoff from this basin is Q25 = 0.09 cfs Q100= 0.18 cfs.
DESIGN POINT C4: BASIN PR -C4 (0.93 acres)
The basin collects runoff from the proposed buildings, rear lots, and roadway. The runoff from
the rear lots and roofs is routed through the proposed underdrain system to Inlet -C4 and Inlet -C6.
The drainage from the roadway and front of the buildings will be captured in curb and gutter
systems and be conveyed into the main storm drainage system via Inlet -C4 and Inlet -C6. The
main storm drain system will be routed to the proposed water quality pond C. The runoff from
this basin is Q25 = 0.17 cfs Qioo = 0.34 cfs.
DESIGN POINT C5: BASIN PR -05 (0.66 acres)
The basin collects runoff from the proposed buildings, rear lots, and roadway. The runoff from
the rear lots and roofs is routed through the proposed underdrain system to the SDMH-MC5 and
Inlet -C1. The drainage from the roadway and front of the buildings will be captured in curb and
gutter systems and be conveyed into the main storm drainage system from Inlet -C4. The main
storm drain system will be routed to the proposed water quality pond C. The runoff from this
basin is Q25 = 0.15 cfs Qioo = 0.29 cfs.
DESIGN POINT C8: BASIN PR -C8 (0.18 acres)
The basin collects runoff from the road and center median along Ironbridge Drive and conveys it
to sump inlet, Inlet -C8. The inlet will collect the flow and convey it to SD -C8. The runoff from
this basin is Q25 = 0.30 cfs Q100= 0.40 cfs.
DESIGN POINT C9: BASIN PR -C9 (0.41 acres)
The basin collects runoff from the road center median to the curb and gutter and conveys it to the
curb cut along Ironbridge Drive. The runoff from this basin is Q25 = 0.15 cfs Q1oo = 0.28 cfs.
DESIGN POINT D3: BASIN PR -D1 (2.83 acres)
The basin collects runoff from proposed lots to the proposed road center and conveys it south
along River Bend Way to Inlet -D3. The runoff will then be routed through SD -D3 to water
quality pond D1. The runoff from this basin is Q25 = 0.18 cfs Q1oo = 0.42 cfs.
DESIGN POINT D2: BASIN PR -D2 (1.99 acres)
The basin collects runoff from proposed lots to the proposed road center and conveys it south
along River Bend Way to Inlet -D2. The runoff will then be routed through SD -D2 to water
quality pond D1. The runoff from this basin is Q25 = 0.07 cfs Q1oo = 0.14 cfs.
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DESIGN POINT D3: BASIN PR -D3 (1.79 acres)
The basin collects runoff from proposed lots to the proposed road center and conveys it north
along River Bend Way to Inlet -D3. The runoff will then be routed through SD -D3 to water
quality pond Di. The runoff from this basin is Q25 = 0.08 cfs Q1oo = 0.20 cfs.
DESIGN POINT D2: BASIN PR -D4 (0.81 acres)
The basin collects runoff from proposed lots to the proposed road center and conveys it north
along River Bend Way to Inlet -D2. The runoff will then be routed through SD -D2 to water
quality pond D1. The runoff from this basin is Q25 = 0.04 cfs Qioo = 0.07 cfs.
DESIGN POINT D3: BASIN PR -D5 (3.52 acres)
The basin collects runoff from proposed lots to the proposed road center and conveys it north
along River Bend Way to Inlet -D3. The runoff will then be routed through SD -D3 to water
quality pond D1. The runoff from this basin is Q25 = 0.24 cfs Q1oo = 0.55 cfs.
DESIGN POINT D6: BASIN PR -D6 (1.11 acres)
The basin collects runoff from proposed lots to the proposed road center and conveys it south
along River Bank Lane to Inlet -D6. The runoff will then be routed through SD -D6 to water
quality pond D2. The runoff from this basin is Q25 = 0.15 cfs Qioo = 0.31 cfs.
DESIGN POINT D7: BASIN PR -D7 (1.45 acres)
The basin collects runoff from proposed lots to the proposed road center and conveys it south
along River Bank Lane to Inlet -D7. The runoff will then be routed through SD -D7 to water
quality pond D2. The runoff from this basin is Q25 = 0.11 cfs Q1o0 = 0.27 cfs.
DESIGN POINT D8: BASIN PR -D8 (0.77 acres)
The basin collects runoff from golf course and open space. The runoff will then sheet flow to
water quality pond D2. The runoff from this basin is Q25 = 0.03 cfs Qtoo = 0.06 cfs.
DESIGN POINT D7: BASIN PR -D9 (0.21 acres)
The basin collects runoff from the golf course, open space to the proposed road center along
River Bank Lane and conveys it north to Inlet -D7. The runoff will then be routed through SD -
D7 to water quality pond D2. The runoff from this basin is Q25 = 0.14 cfs Qloo = 0.21 cfs.
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DESIGN POINT D6: BASIN PR -D10 (0.29 acres)
The basin collects runoff from proposed lots to the proposed road center along River Bank Lane
and conveys it north to Inlet -D6. The runoff will then be routed through SD -D6 to water quality
pond D2. The runoff from this basin is Q25 = 0.09 cfs Q10o = 0.16 cfs.
DESIGN POINT D-11: BASIN PR-Dll (0.78 acres)
The basin collects runoff from the golf course, open space to the proposed road center along
River Bank Lane and conveys it to Inlet -D11. The runoff will then be routed through SD -D11
where it will be conveyed to water quality pond D2 via the main storm drain pipe. The runoff
from this basin is Q25 = 0.07 cfs Q1oo = 0.18 cfs.
DESIGN POINT D12: BASIN PR -D12 (0.73 acres)
The basin collects runoff from proposed units to the proposed road center along River Bank Lane
and conveys it to Inlet -D12. The runoff will then be routed through SD-MD12 where it will be
conveyed to water quality pond D2 via the main storm drain pipe. The runoff from this basin is
Q25 = 0.05 cfs Qioo = 0.11 cfs.
DESIGN POINT D13: BASIN PR -D13 (1.33 acres)
The basin collects runoff from the gold course, open space to the proposed road center along
River Bank Lane and conveys it to Inlet -D13. The runoff will then be routed through SD -D13
where it will be conveyed to water quality pond D2 via the main storm drain pipe. The runoff
from this basin is Q25 = 0.10 cfs Qioo = 0.24 cfs.
DESIGN POINT D14: BASIN PR -D14 (1.43 acres)
The basin collects runoff from proposed units to the proposed road center along River Bank Lane
and conveys it to Inlet -D14. The runoff will then be routed through SD -D14 where it will be
conveyed to water quality pond D2 via the main storm drain pipe. The runoff from this basin is
Q25 = 0.14 cfs Qioo = 0.31 cfs.
DESIGN POINT D15: BASIN PR -D15 (0.14 acres)
The basin collects runoff from open space to the proposed road center along Red Bluff Vista and
conveys it to an existing offsite roadway ditch previously constructed during Phase 1. The routed
runoff will receive water quality treatment as it travels along the roadside ditch. The treated
runoff will then be routed offsite through the existing drainage system. The runoff from this
basin is Q25 = 0.15 cfs Qioo = 0.20 cfs.
DESIGN POINT D16: BASIN PR -D16 (1.16 acres)
The basin collects runoff from proposed front lots to the proposed road center along River Bend
Way and routes it to Inlet -D 16. The runoff will then be routed through SD -D 16 where it will be
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conveyed to water quality pond D2 via the main storm drain pipe. The runoff from this basin is
Q25 = 0.23 cfs Qioo = 0.46 cfs.
DESIGN POINT D 16: BASIN PR -D17 (1.67 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to Inlet -D16. The runoff will then be routed through SD -D16 where it will be
conveyed to water quality pond D2 via the main storm drain pipe. The runoff from this basin is
Q25 = 0.70 cfs Q100= 1.26 cfs.
DESIGN POINT D18: BASIN PR -D18 (0.96 acres)
The basin collects runoff from proposed front lots to the proposed road center along River Bend
Way and routes it to Inlet -D18. The runoff will then be routed through SD -D18 where it will be
conveyed to water quality pond D2 via the main storm drain pipe. The runoff from this basin is
Q25 = 0.25 cfs Q100= 0.48 cfs.
DESIGN POINT D18: BASIN PR -D19 (1.04 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to Inlet -D18. The runoff will then be routed through SD -D18 where it will be
conveyed to water quality pond D2 via the main storm drain pipe. The runoff from this basin is
Q25 = 0.47 cfs Qioo = 0.75 cfs.
DESIGN POINT D25: BASIN PR -D20 (1.35 acres)
The basin collects runoff from proposed roofs and rear lots to and underdrain system, where it
will be routed to Inlet -D-25. The runoff will then be routed through SD -D25 where it will be
routed to water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25
= 0.22 cfs Q100= 0.47 cfs.
DESIGN POINT D25: BASIN PR -D21 (0.33 acres)
The basin collects runoff from proposed lot fronts to the Pinyon Court centerline. The runoff
collects in the curb and gutter and is routed to the Inlet -D25. The runoff will then be routed
through SD -D25 where it will be conveyed to water quality pond D2 via the main storm drain
pipe. The runoff from this basin is Q25 = 0.20 cfs Qioo = 0.32 cfs.
DESIGN POINT D18: BASIN PR -D22 (0.52 acres)
The basin collects runoff from proposed front lots and Red Bluff Vista to the centerline. The
runoff flows along the curb and gutter to Inlet -D 18. The runoff will then be routed through SD -
D 18 where it will be conveyed to water quality pond D2 via the main storm drain pipe. The
runoff from this basin is Q25 = 0.31 cfs Q100= 0.47 cfs.
Page 15
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DESIGN POINT D18: BASIN PR -D23 (0.58 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to Inlet -D18. The runoff will then be routed through SD -D18 where it will be
conveyed to water quality pond D2 via the main storm drain pipe. The runoff from this basin is
Q25 = 0.31 cfs Qloo = 0.52 cfs.
DESIGN POINT D25: BASIN PR -D24 (1.40 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to Inlet -D25. The runoff will then be routed through SD -D25 where it will be
conveyed to water quality pond D2 via the main storm drain pipe. The runoff from this basin is
Q25 = 0.27 cfs Q1oo = 0.55 cfs.
DESIGN POINT D25: BASIN PR -D25 (0.30 acres)
The basin collects runoff from the proposed lot fronts to the Pinyon Court centerline. The runoff
collects in curb and gutter and is routed to the Inlet -D25. The runoff will then be routed through
SD -D25 to water quality pond D2 via the main storm drain pipe. The runoff from this basin is
Q25 = 0.21 cfs QIoo = 0.31 cfs.
DESIGN POINT D29: BASIN PR -D26 (0.65 acres)
The basin collects runoff from proposed front lots and Pinyon Court to the centerline. The runoff
flows along the curb and gutter to Inlet -D29. The runoff will then be routed through SD -D29 to
water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.23 cfs
Qioo = 0.40 cfs.
DESIGN POINT D29: BASIN PR -D27 (0.45 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to Inlet -D29. The runoff will then be routed through SD -D29 to water quality
pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.36 cfs Qioo = 0.54
cfs.
DESIGN POINT D29: BASIN PR -D28 (0.24 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to Inlet -D29. The runoff will then be routed through SD -D29 to water quality
pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.18 cfs Qloo = 0.27
cfs.
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DESIGN POINT D-29: BASIN PR -D29 (0.35 acres)
The basin collects runoff from proposed front lots and River Bend Way to the centerline. The
runoff flows along the curb and gutter to Inlet -D29. The runoff will then be routed through SD -
D29 to water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 =-
0.12
0.12 cfs Qioo = 0.21 cfs.
DESIGN POINT D-30: BASIN PR -D30 (0.38 acres)
The basin collects runoff from proposed front lots and River Bend Way to the centerline. The
runoff flows along the curb and gutter to Inlet -D30. The runoff will then be routed through SD -
D30 to water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 =
0.10 cfs Qioo = 0.19 cfs.
DESIGN POINT D30: BASIN PR -D31 (0.55 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to Inlet -D30. The runoff will then be routed through SD -D30 to water quality
pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.59 cfs Q1oo = 0.84
cfs.
DESIGN POINT D-32: BASIN PR -D32 (0.15 acres)
The basin collects runoff from open space and River Bend Way to the centerline. The runoff
flows along the curb and gutter to Inlet -D32. The runoff will then be routed through SD -D32 to
water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.19 cfs
Qioo = 0.26 cfs.
DESIGN POINT D33: BASIN PR -D33 (0.35 acres)
The basin collects runoff from open space and River Bend Way to the centerline. The runoff
flows along the curb and gutter to Inlet -D33. The runoff will then be routed through SD -D33 to
water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.09 cfs
Qioo = 0.17 cfs.
DESIGN POINT D40: BASIN PR -D34 (0.54 acres)
The basin collects runoff from open space and two lots. The runoff will be captured in a
proposed underdrain and routed to SDMH-D36. The runoff will then be routed through SD -D36
to water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.12
cfs Q100= 0.26 cfs.
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DESIGN POINT D40: BASIN PR -D35 (0.47 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed through SD -D36 to Inlet -D40. The runoff will then be routed through SD -D40 to
water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.35 cfs
Qioo = 0.52 cfs.
DESIGN POINT D40: BASIN PR -D36 (0.41 acres)
The basin collects runoff from proposed front lots and River Bend Way to the centerline. The
runoff flows along the curb and gutter to Inlet -D40. The runoff will then be routed through SD -
D40 to water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 =
0.08 cfs Q1oo = 0.17 cfs.
DESIGN POINT D41: BASIN PR -D37 (0.27 acres)
The basin collects runoff from proposed front lots and River Bend Way to the centerline. The
runoff flows along the curb and gutter to Inlet -D41. The runoff will then be routed through SD -
D41 to water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 =
0.07 cfs Qioo = 0.13 cfs.
DESIGN POINT D43: BASIN PR -D38 (0.35 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to Inlet -D41. The runoff will then be routed through SD -D41 to water quality
pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.38 cfs Qio0 = 0.53
cfs.
DESIGN POINT D40: BASIN PR -D39 (1.62 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to Inlet -D40. The runoff will then be routed through SD -D40 to water quality
pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.49 cfs Qioo = 0.91
cfs.
DESIGN POINT D40: BASIN PR -D40 (0.42 acres)
The basin collects runoff from proposed front lots and River Bend Way to the centerline. The
runoff flows along the curb and gutter to Inlet -D40. The runoff will then be routed through SD -
D40 to water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 =
0.08 cfs Qioo = 0.15 cfs.
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DESIGN POINT D-41: BASIN PR -D41 (0.42 acres)
The basin collects runoff from proposed front lots and River Bend Way to the centerline. The
runoff flows along the curb and gutter to Inlet -D41. The runoff will then be routed through SD -
D41 to water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 =
0.08 cfs Qloo = 0.15 cfs.
DESIGN POINT D43: BASIN PR -D42 (0.56 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to Inlet -D41. The runoff will then be routed through SD -D41 to water quality
pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.70 cfs Qioo = 0.97
cfs.
DESIGN POINT D43: BASIN PR -D43 (1.00 acres)
The basin collects runoff from proposed front lots and River Bend Way to the centerline. The
runoff flows along the curb and gutter to Inlet -D4. The runoff will then be routed through SD -
D4 to water quality pond D2 via the main storm drain pipe. The runoff from this basin is Q25 --
0.25
0.25 cfs Q1oo = 0.46 cfs.
DESIGN POINT D43: BASIN PR -D44 (1.14 acres)
The basin collects runoff from proposed roofs and rear lots to a proposed underdrain, where it
will be routed to SDMH-D43. The runoff will then be routed through SD -D43 to water quality
pond D2 via the main storm drain pipe. The runoff from this basin is Q25 = 0.69 cfs Qioo = 1.03
cfs.
BASIN PR -D45 (0.04 acres)
The basin collects runoff from open space to the proposed road center along Red Bluff Vista and
conveys it to an existing offsite roadway ditch previously constructed during Phase 1. The routed
runoff will receive water quality treatment as it travels along the roadside ditch. The treated
runoff will then be routed offsite through the existing drainage system. The runoff from this
basin is Q25 = 0.11 cfs Qioo = 0.13 cfs.
BASIN PR -D46 (1.71 acres)
The basin collects runoff from open space behind the proposed lots along River Bend Way, and
the existing golf course and then routes it to the existing Robertson Ditch. The proposed
underdrain system along River Bend way will reduce the amount of runoff into the Robertson
Ditch. No proposed or existing roads are located within the proposed basin. The runoff is then
routed offsite along the existing ditch system. The runoff from this basin is Q25 = 0.03 cfs Q1oo =
0.08 cfs.
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DESIGN POINT D8: BASIN PR -D47 (7.86 acres)
The basin collects runoff from open space behind the proposed lots along River Bend Way, and
the existing golf course and then routes it to the existing Robertson Ditch. The proposed
underdrain system along River Bend way will reduce the amount of runoff into the Robertson
Ditch. No proposed or existing roads are located within the proposed basin. The runoff is then
routed offsite along the existing ditch system. The runoff on the east side of the ditch sheet flows
down to the proposed water quality pond D2. The runoff from this basin is Q25 = 0.14 cfs Qloo =
0.35 cfs.
III. DRAINAGE BASIN CRITERIA
A. Regulations
The drainage facilities and conveyance methods were designed per UDFCD and Garfield County
drainage requirements 9:42 and 9:43. The TR -55 Method was used to compute flows for the
proposed development. The street capacity was determined using the two proposed roadway
cross-sections for the proposed development with the curb and gutter and street being inundated
to the centerline of the road during the 100 -year storm event. The computer program, Flow
Master was used to determine flow capacity for the proposed street section. The inlet
calculations have been performed for an inlet in sump condition using the Urban Drainage and
Flood Control District's (UDFCD) Street and Inlet Hydraulics Version 2.04a. A range of flows
was used for inlet sizing rather than computing inlet calculations for each inlet. The water
quality pond sizes were determined using AutoCAD's hydrology program. The AutoCAD
program was also used to determine the pipe sizes for the 25 -year storm per the Garfield County
drainage regulations. The UDFCD excel spreadsheet program for Extended Detention Basin
(EDB) was used to size the orifice plates and outlet structures.
B. Development Criteria Reference and Constraints
High Country Engineering, Inc previously prepared an overall site Preliminary Drainage Report
for the Rose Ranch P.U.D. on April 3, 2003. The report discusses drainage for the entire site,
including Phases 2-4. The information contained in the previous report was used to determine
existing and proposed site conditions for the above referenced phases. The previous
development design utilized roadside drainage ditches for water quality control before releasing
the water to the Roaring Fork River. Since detention facilities were not required for the
previously accepted development do to its proximity to the Roaring Fork River, Ironbridge
P.U.D. is proposing to provide the 2 -year water quality capture volume in the five proposed
ponds in lieu of the previously used form of water quality control. Each water quality pond has
an emergency spillway that was designed to carry the 100 -year storm event for added protection.
The drainage patterns described herein this report will not affect the existing Phase 1
development.
Page 20
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C. Hydrological Criteria
The proposed development was designed for the (2 -year) storm, (25 -year), and (100 -year) storm
events. The TR -55 Method Runoff Coefficients are from the TR -55 Manual using type B soils.
Existing conditions used cultivated area agricultural area and pavement. The proposed
development was broken down to landscape areas, pavement areas, and roofs. The storage
volumes will be per UDFCD's Modified FAA procedure. All storm pipes and inlet structures
were designed for the 25 -year storm event. The water quality ponds were sized for the 2 -year
storm event and the emergency spillways were designed for the 100 -year storm. The 100 -year
storm event from the two offsite basins, EX -0S8 and EX -0S9 were used to size the storm drain
pipe going north on River Bend Way and water quality pond D2's volume. The 100 -year storm
event was used since there is no existing information regarding the drainage patterns and existing
runoff rates from the two areas.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
The typical drainage patterns are not similar to the existing conditions. The five proposed water
quality ponds release storm water to the Roaring Fork River. The proposed site does allow some
direct discharge from the back of some lots throughout the site to its historic location. Please see
the attached appendix for a list of summary tables and drawings.
The inlets and pipes were designed for the 25 -year storm. The water quality pond facilities were
designed for the 2 -year storm event. The emergency spillway and the outlet structure pipes were
designed for the proposed 100 -year storm inflow. Orifice plates were sized for the 40 -hour water
quality capture volume for ponds A, B, C, and D2. The required water quality storage volume
for pond D1 was minimal, so the orifice plate and the outlet structure were designed for the 25 -
year storm event.
The water quality ponds have been designed per the Urban Drainage and Flood Control District
(UDFCD) regulations. The five proposed water quality ponds all discharge to the Roaring Fork
River.
Proposed water quality pond A is located at the central north part of the Phase 2 development.
The proposed pond will be sized for the water quality capture volume (WQCV), which is based
on the 2 -year storm event. The orifice plate and outlet structure was also sized to drain the
WQCV over a 40 -hour period. The outlet pipe and emergency spillway was also sized for the
proposed 100 -year inflow. The existing allowable release rate is Q2 = 0.05 cfs. The required
WQCV is 1,812 cu. ft and the water surface elevation (WSEL) is 5939.07. The orifice for the
WQCV will have three columns and six rows of 0.335 -inch diameter circular openings along the
steel plate. There will also be a grate over the outlet structure box to control the amount of large
refuge entering the outlet structure. The outlet structure will be a 2.07 -feet tall, 3 -feet wide and
4 -feet long box. The outlet structure detail and calculation can be seen in the appendix.
Page 21
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Proposed water quality pond B is located in the northeast corner of the development. The
proposed pond will be sized for the water quality capture volume (WQCV), which is based on
the 2 -year storm event. The orifice plate and outlet structure was also sized to drain the WQCV
over a 40 -hour period. The outlet pipe and emergency spillway will be sized for the proposed
100 -year inflow. The proposed release rate is Q2 = 0.23 cfs and the required detention volume
for the 2 -year storm event is 1,916 cu. ft. The water surface elevation (WSEL) is 5927.99. The
orifice plate for the WQCV will have two columns and seven rows of 0.375 -inch diameter
circular openings along the steel plate. There will also be a grate over the outlet structure box to
control the amount of large refuge entering the outlet structure. The outlet structure will be a
2.39 -feet tall, 3 -feet wide and 4 -feet long box. The outlet structure detail and calculation can be
seen in the appendix.
Proposed water quality pond C is located at the east portion of Phase 3 development. The
proposed pond will be sized for the water quality capture volume (WQCV), which is based on
the 2 -year storm event. The orifice plate and outlet structure was also sized to drain the WQCV
over a 40 -hour period. The outlet pipe and emergency spillway will be sized for the proposed
100 -year inflow. The allowable proposed release rate is Q2 = 0.04 cfs. The required detention
volume for the 2 -year storm event is 895 cu. ft. and the water surface elevation (WSEL) is
5941.69 ft. The orifice plate for the WQCV will have three columns and five rows of 0.3311 -
inch diameter circular openings along the pipe. The outlet structure will have a storm grate over
the outlet structure box. The outlet structure will be a 2 -feet tall, 3 -feet wide and 4 -feet long box.
The outlet structure detail and calculation can be seen in the appendix.
Proposed water quality pond D1 is located in the east central part of the development. The
proposed pond will be sized for the water quality capture volume (WQCV), which is based on
the 2 -year storm event, and the 25 -year storm event. The orifice plate and outlet structure was
also sized to drain the WQCV over a 40 -hour period. The outlet pipe and emergency spillway
was sized for the proposed 100 -year inflow. The proposed release rates are Q2 = 0.04 cfs and Q25
= 0.02 cfs. The required detention volume for the WQCV is 10 cu. ft. and the 25 -year storm
event is 3,161 cu. ft. The water surface elevation (WSEL) is 5936.45 ft and 5939.97 ft
respectively. The required storage volume for the WQCV is very small, so the orifice plate will
be sized for the 25 -year storm event. The 25 -year storm will have a storm grate over the outlet
structure box and an orifice plate will be placed at the end of the box, in front of the outlet pipe.
The orifice plate will have one column and eleven rows of 0.313 -inch diameter circular openings
along the steel pipe. The outlet structure will be a 3.67 -foot tall, 3 -feet wide and 4 -feet long box.
The outlet structure detail and calculation can be seen in the appendix.
Proposed water quality pond D2 is located in the southeast part of the development. The
proposed pond will be sized for the water quality capture volume (WQCV), which is based on
the 2 -year storm event. The orifice plate and outlet structure was also sized to drain the WQCV
over a 40 -hour period. The outlet pipe and emergency spillway will be sized for the proposed
100 -year inflow. The proposed release rate is Q2 = 0.63 cfs. The required detention volume for
the 2 -year storm event is 12,202 cu. ft. and the water surface elevation (WSEL) is 5937.20 ft.
The orifice plate for the WQCV will have three columns and sixteen rows of 0.34 -inch diameter
circular openings along the steel plate. A storm grate will be over the outlet structure box to
Page 22
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reduce refuge intake into the structure. The outlet structure will be a 5.2 -feet tall, 3 -feet wide and
4 -feet long box. The outlet structure detail and calculation can be seen in the appendix.
V. CONCLUSIONS
This drainage report has been designed per SWMM and the Garfield County Standards. The
proposed storm drain facility has been designed to accommodate the runoff from this
development. Storm water flows leaving the proposed development improvements will have no
downstream impacts on adjacent properties.
Page 23
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V. References
"Preliminary Drainage Report for Rose Ranch P.U.D." April 3, 2003, High Country Engineering,
Inc.
"Urban Storm Drainage Criteria Manual" 2001 Edition, Urban Drainage and Flood Control
District, 2480 West 26th Avenue, Suite 156-B, Denver, CO 80211.
"Garfield County Zoning Resolution of 1978" Board of County Commissioners, Garfield
County, CO 81602.
Page 24
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PHONE (303) 925-0544 FAX (303) 9250547
1517 BLAKE AVENUE, STE 101, GLENWOOD SPRINGS, CO 81601
PHONE (970) 945-8676 FAX (970) 945-2555
W W W.HCENG.COM
IRONBRIDGE HOMES
' GARFIELD COUNTY. CO
IRONBRIDGE P.U.D.
EXHIBIT #1
VICINITY MAP
DRAWN BY:
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SCALE:
1 " = 2000'
CHECKED BY:
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PROJECT NO:
2051019 00
DATE: PAGE:
6-17-05 1
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hallow and moderately dep soils; on eroded hills, mountainsides, and breaks.
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1517 BLAKE AVENUE, STE 101, GLENWOOD SPRINGS, C091801
PHONE (970) 9458878 FAX (970) 945-2556
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IRONBRIDGE P.U.D. I--IC/E PHONE (30918250544 FAX (3031925-0547
EXHIBIT #5 m p`l� 1817 BLAKE AVENUE, STE 101, GLENWOOD SPRINGS, CO 81801
Y/f2 (' PHONE (97019458878 FAX (870) 8462555
FEMA C✓NEE R` W W W.HCING.COM
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NO.
DATE
REVISION
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BY
CALL UT1Lm NOTIFICATION
CENTER OF COLORADO
1$04922-1 987
OR 5S4-06700IN METRO DENVER
CALL2 2 -BUSINESS DAYS IN ADVANCE
BEFORE YOU DIG GRADE OR
EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTIUTIES
cRECKED av:
REW
DATE:
6 17-05
FILE:
FEMA. DWG
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EXHIBIT #6
COLORADO WATER CONSERVATION BOARD
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1517 BLAKE AVENUE, STE 101, GLENWOOD SPRINGS, CO 81801
PHONE (970) 9458676 FAX (970) 9452555
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1-806922.1987
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CALL 20USINE55 DAYS IN ADVANCE
BEFORE YOU DIG, GRADE, p0p9p
UNDERVGROUND MEMBER UUTT)LmES
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IRONBRIDGE HOMES
GARFIELD COUNTY, COLORADO
IRONBRIDGE
EXHIBIT #7
NOAA, 2 YR - 24 HOUR
HIGH COUNTRY ENGINEERING, INC.
14 INVERNESS DRIVE EAST, STE F-120, ENGLEWOOD, CO 80112
PHONE (303) 925.0544 FAX (303) 915.0847
1817 BLAKE AVENUE, STE 101, GLENWOOD SPRINGS, CO 81601
PHONE (970) 945-8878 FAX (970) 9462855
W W W.HCENO.COM
CHECKED BY:
REW
DATE:
6.) 7-05
FILE:
NOAA-2YR
NO. DATE
REVISION
BY
CALL UTILITY
CENTER OF COLORADOON
1-800-922-1 987
OR 534.05700IN METRO DENVER
CALL 2 -BUSINESS DAYS IN ADVANCE
BEFORE YOU DIG, GRADE. OR
EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTIUTIES
3:\S05KPROJ\205\1019 Docs \NOAH-25YR.dwg, 7/18/2005 2:08:13 PM
•
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IRONBRIDGE HOMES
GARFIELD COUNTY. COLORADO
IRONBRIDGE
EXHIBIT #7
NOAA, 25 YR - 24 HOUR
HIGH COUNTRY ENGINEERING, INC. —wHao,D
14 INVERNESS DRIVE EAST, STE F.120, ENGLEWOOD, CO 80112
PHONE (3031925-0544 FAX (303) 925-0547
1517 BLAKE AVENUE, STE 101, GLENWOOD SPRINGS. CO 81001
PHONE (970) 9458678 FAX (970) 945-2555
W W W.HCGNd.COM
CHECKED BY:
REW
FILE:
NO. DATE
REVISION
BY
6.17-05
NOAA.2YR
CALL UTILITY NOTIFICATION
CENTER OF COLORADO
1-800-922-1987
OR 534.09700 IN METRO DENVER
CALL 2 -BUSINESS DAYS IN ADVANCE
BEFORE YOU DIG y GRADE. OR
EXCAVATE FOR THC MARKING OF
UNDERGROUND MEMBER UTLITIES
J:\SDSKPRO3\205\101Docs\NOAH-100YR.dwg, 7/18/2005 2:08:52 PM
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IRONBRIDGE HOMES
GARFIELD COUNTY, COLORADO
IRONBRIDGE
EXHIBIT #7
NOAA, 1OOYR-24HOUR
HIGH COUNTRY ENGINEERING, INC. D—DDJD
14 INVERNESS DRIVE EAST, STE F-120, ENGLEWOOD, CO 80112
PHONE (303) 925.0544 FAX (303) 9250547
1517 BLAKE AVENUE, STE 101, GLENWOOD SPRINGS. CO 81601
PHONE (970) 9458676 FAX (970) 945-2555
WW W.NCENG.COM
CHECKED BY:
REW
DATE:
FILE.
NOAA-2YR
NO. DATE
REVISION
BY
6-17-05
CALL UTILITY NOTIFICATION
CENTER OF COLORADO
1-800-922-1987
OR 534.06700 IN METRO DENVER
CALL 28USINESS DAYS IN ADVANCE
BEFOREYOU DIG GRADE.OR
UNDERGROUND
TE 609 MEMBER KING OF
UNDERGROUND MEMBER UTILITIES
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LB ROSE RANCH, LLC
GARFIELD COUNT', COLORADO
IRONBRIDGE
EXHIBIT #8
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PHONE (303) 9250544 FAX (303) 9250547
1517 BLAKE AVENUE, STE 101, GLENWOOD SPRINGS, CO 81601
PHONE (970) 9454878 FAX (970) 9452555
W W W.HCENG.COM
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DATE:
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NO. DATE
REVISION
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BY
CALL UTILITY NOTIFICATION
CENTER OF COLORADO
1.800-922-1987
OR 53.4.06700 IN METRO DENVER
CALL 2-19USINESS DAYS IN ADVANCE
BEFORE YOU DIG. GRADE. OR
EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES