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Final Drainage Report Affordable Housing Project 104th Ave and
Colorado Blvd City of Thornton, Colorado November 20th, 2015
Prepared For: Adams County Housing Authority 7190 Colorado Blvd,
6th Floor Commerce City, Colorado 80022
Prepared By:
EES Entitlement and Engineering Solutions, Inc. 518 17th Street,
Suite 1575 Denver, CO 80202 Phone: (303) 572-7997 Contact: Jay
Peters, PE Email: [email protected]
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Certification Adams County Housing Authority hereby certifies
that the drainage facilities for ‘Affordable Housing at 104th and
Colorado’ will be constructed according to the design presented in
this report. I understand that the City of Thornton does not and
shall not assume liability for the drainage facilities designed
and/or certified by my engineer. I understand that the City of
Thornton reviews drainage plans but cannot, or behalf ‘Affordable
Housing at 104th and Colorado’ guarantee that final drainage design
review will absolve Adams County Housing Authority and/or their
successors and/or assigns of future liability for improper design.
I further understand that approval of the Plat and/or Development
Permit does not imply approval of my engineer’s drainage deign.
Attest: ___________________________________ Name of Responsible
Party ____________________________
___________________________________ Notary Public Authorized
Signature I hereby certify that this report (plan) for the final
drainage design of ‘Affordable Housing at 104th and Colorado’ was
prepared by me (or under my direct supervision) in accordance with
the provisions of the City of Thornton Standards and Specifications
for the Design and Construction of Public and Private Improvements
for the Responsible Parties thereof. I understand that the City of
Thornton does not and shall not assume liability for drainage
facilities designed by others Jay S. Peters P.E. Registered
Professional Engineer State of Colorado No. 35068
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104th and Colorado, Final Drainage Report
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TABLE OF CONTENTS
1.0 GENERAL LOCATION AND DESCRIPTION
...................................................... 2 2.0
DRAINAGE BASINS AND SUB-BASINS
............................................................ 3 3.0
DRAINAGE DESIGN CRITERIA
..........................................................................
4 4.0 DRAINAGE FACILITY DESIGN
...........................................................................
5 5.0 CONCLUSIONS
...................................................................................................
7 6.0 REFERENCES
.....................................................................................................
7 TABLES
1. Detention Basin Volume Summary
APPENDIX
Location map Hydrology Calculations Detention Pond EURV
Calculations Pond Stage-Storage Table Hydraulic Calculations Inlet
Capacity Calculations NRCS Soils Information Geotechnical Soils
Tables Drainage Map
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1.0 GENERAL LOCATION AND DESCRIPTION 1.1 LOCATION 1.1.1 City,
County, State Highway, and Local Streets The 104th and Colorado
project is located in the City of Thornton at the intersection of
104th Avenue and Colorado Blvd (see Location Map). It is bounded by
open space on the South, commercial development and Colorado Blvd.
on the west, 104th Avenue on the north, and open space on the east.
1.1.2 Township, Range, Section The project lies within the NW ¼ of
Section 18, Township 2 South, Range 67 West of the 6th Principal
Meridian in the City and County of Denver, Colorado. 1.1.3
Surrounding Developments The site is bounded by the commercial
development to the west and north, and open space to the east and
south. 1.2 DESCRIPTION OF PROPERTY 1.2.1 General Project
Description 104th and Colorado is an affordable housing project
consisting mostly of residential townhomes and apartments buildings
with some retail in the north building. There will be 3
multi-family residential buildings on the site. 1.2.2 Area The area
of the site is 5.02 acres. 1.2.3 Ground Cover The project site is
currently undeveloped. The site is primarily open space covered
with short grasses. The site generally slopes to the east at around
1% to 5%. The NRCS soil survey lists the soils on the site as
Platner and Ulm Loam, that are in Hydrologic Soil Group C. A
geotechnical study for the Phase I improvements at Aria found lean
clays on the site, indicating the soils are Group D. 1.2.4 Major
Drainage-ways and Facilities
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No major drainage-ways or facilities exist on the project site.
The site is located within the Grange Hall Creek watershed. 1.2.5
Existing Major Irrigation Facilities No major irrigation facilities
exist within the site. 1.2.6 History of Flooding There are no
reported flooding problems on the site. 1.2.7 Easements within and
Adjacent to the Site There are no easements on the site. 2.0
DRAINAGE BASINS AND SUB-BASINS 2.1 MAJOR BASIN DESCRIPTION 2.1.1
Major Drainage-way Studies There is one previous major drainage-way
study that included the project site, which is the Grange Hall
Creek Major Drainage-way Planning Study completed in 1997. This
Master Plan is currently being updated by UDFCD and the Project
Sponsors. 2.1.2 Major Basin Characteristics The site is within the
Grange Hall Creek watershed, specifically the Riverdale Tributary.
The stream channel is about 400 feet to the south of the project
site. The site is within sub-basins 8 and 54 of the planning study.
The north portion of the site is within Sub-basin 8 and flows east
to the creek. The south portion of the site is within sub-basin 54
and flows southeast to the creek. Runoff from the site is conveyed
overland to the stream channel, there are no storm sewers or other
types of formal conveyance systems between the site and the Creek.
2.1.3 Irrigation Facilities No irrigation facilities are located
within the site. 2.2 SUB-BASIN DESCRIPTION 2.2.1 Historic Drainage
Patterns
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The site generally conveys runoff overland to the east and
southeast. Runoff flows overland to the creek through the open
space. 2.2.2 On-Site and Off-Site Sub-basin Characteristics There
is a portion of a small retail development to the west of the site
that convey runoff overland onto the site. The north portion of the
site flows east to the creek. The southern portion of the site
flows southeast to the creek. 3.0 DRAINAGE DESIGN CRITERIA 3.1
REGULATIONS The 104th and Colorado Project design criteria were
developed using regulations, standards, and criteria found within
the City of Thornton’s Storm Drainage Design, Grading, and Water
Quality Technical Criteria, CDOT’s Drainage Manual, and the Urban
Drainage and Flood Control District’s Drainage Criteria Manual,
Volumes I, II, and III. 3.2 DEVELOPMENT CRITERIA REFERENCE AND
CONSTRAINTS 3.2.1 Previous Drainage Studies for the Site There are
no known drainage studies specifically for the project site. 3.2.2
Relationship to and Implication of Adjacent Drainage Studies No
adjacent drainage studies are available for this site. 3.2.3 Site
Drainage Impact The site will not adversely impact surrounding
drainage systems. 3.3 HYDROLOGIC CRITERIA Design Rainfall: 1-hour
point rainfall depths of 1.38 and 2.69 for the 10- and 100-year
storm
events, respectively. Depths were obtained from Table 400-1 of
the City of Thornton’s Criteria.
Hydrologic Soil Group: NRCS hydrologic soil group C. Runoff
Calculation Method: Rational Formula. Conveyance System Design
Storm Recurrence Intervals: 5-year & 100-year Detention Release
Rates: 0.30 cfs/acre for 10-year, 1.0 cfs/acre for 100-year Size
detention ponds using the Excess Urban Runoff Volume Method
(EURV).
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3.4 HYDRAULIC CRITERIA Size storm sewers for the 5-event. Size
inlets for the 5-year event. Size major system for the 100-year
event. Hydraulic Calculation Method: Standard Step Backwater. Do
not adversely impact existing storm systems for surrounding
developments. 3.5 WATER QUALITY CRITERIA Provide permanent BMPs in
accordance with V3 of the UDFCD USDCM. 3.6 VARIANCES FROM
CRITERIA
No waivers are requested for this portion of the project. 4.0
DRAINAGE FACILITY DESIGN 4.1 GENERAL CONCEPT The overall storm
improvements at Aria will consist of: Inlets and storm sewers that
convey runoff from the site to the NW Pond; Regional detention and
water quality treatment pond to the south of the site. The project
will implement new storm sewers and inlets within the on the site,
and convey runoff to the regional pond to the south of the site.
Storm sewers are sized for a minimum capacity of a 5-year storm
event, with the 100-year storm event conveyed in the streets. Storm
sewers in several locations are sized to convey the 100-year storm
event to prevent runoff from entering property adjacent to the
site, or where grades do not allow surface conveyance on the
streets. 4.2 SPECIFIC DETAILS 4.2.1 Conveyance System The storm
infrastructure improvements will consist of storm sewers, chases,
and inlets. The new conveyance system for the site will consist of
the following: Chases in parking lot medians. Type C and Type R
inlets at low points on the site. 18- to 30-inch diameter storm
sewer along the east side of the site. Several short 18-inch storm
sewer laterals. Relocation of the inlets in 104th Avenue at the new
drive access.
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Concrete pan above the retaining wall along the west site
boundary. Chases will be installed within parking lot medians to
allow runoff to be conveyed overland to the storm system on the
east side of the site. There will be an 18- to 30- inch primary
storm sewer with numerous inlets along the east boundary of the
site. The storm sewer and inlets are sized to capture and convey
the 100-year storm event to the regional detention pond. There is a
new 18-inch storm sewer at the low point of the south access drive
that captures runoff from the open space to the north, and runoff
from the roadway. The storm sewer will connect to the new family
dollar storm sewer. The storm sewer and inlets will capture and
convey the 100-year storm event to the regional detention pond.
Existing inlets within 104th Avenue will need to be removed and
reconstructed to accommodate the deceleration lane to the project
site. A concrete pan will be constructed immediately above the
proposed retaining wall along the west boundary of the site. The
pan will convey off-site runoff to the north around the planned
development, and is sized for the 100-year event. 4.2.2 Water
Quality Treatment Facilities and BMPs An extended detention basin
(EDB) permanent BMP will be installed in the regional pond. The EDB
is sized to capture and treat runoff from the entire site, in
addition to the RTD light rail station and Colorado Marketplace
retail center. Volumes and water surface elevations are provided in
Section 4.2.3. 4.2.3 Detention Facilities The Regional pond will
detain and treat runoff from the site, as well as the off-site
watershed areas from the 104th Light Rail Station, and the retail
center, for a total watershed area of 32.48 acres. Overall
imperviousness for the watershed contributing to the detention pond
is estimated to be 69%. The required volumes for the Northwest
Detention Pond are summarized in Table 2 below.
Table 1 Detention Pond Summary
Pond Area, acres %
imperviousness EURV,
AF 100-year
Volume, AF Release Rate, cfs
Previous RTD 60% Design 27.48 64 1.75 3.40 27.48
Expanded for ADCHA Project 32.48 69 2.24 3.92 32.48
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4.2.4 Drainage Easements and Tracts An easement will be provided
for the storm sewer that crosses through the public open space. No
drainage easements are planned for the site, as the storm sewer
will be private, and serving only one owner. 4.2.5 Maintenance The
stormwater improvements on the project site are private
improvements, and will be maintained by ADCHA. 4.2.6 Groundwater
and Bedrock The storm sewers for the site are above the estimated
groundwater and bedrock levels on the site. Pickering, Cole, and
Hivner, LLC prepared a preliminary geotechnical investigation
report for the Site in October 2014. The boring logs from the
report are included in the appendix. 4.2.7 Wetland Mitigation and
Preservation There are no wetlands on the site. 5.0 CONCLUSIONS 5.1
COMPLIANCE WITH STANDARDS This drainage report presents the
drainage analysis for 104th and Colorado, and complies with the
criteria and standards of the City of Thornton’s Storm Drainage
Design, Grading, and Water Quality Technical Criteria. 5.2 DRAINAGE
CONCEPT The drainage system provides a 100-year level of protection
for the site. The conveyance system is designed to safely convey
the 100-year storm. 5.3 WATER QUALITY Water quality treatment is
provided for the site in accordance with the UDFCD Volume 3 USDCM.
6.0 REFERENCES
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104th and Colorado, Final Drainage Report
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1. Pickering, Cole, and Hivner, LLC. October 2014. Preliminary
Geotechnical Engineering Report.
2. City of Thornton. October 2012. Standards and Specifications.
3. Colorado Dept. of Transportation. 2004. Drainage Design
Manual.
4. Merrick and Company. August 2015. Thornton Family Dollar
Construction Documents.
5. Regional Transportation District. May 2015. 104th Station 60%
Preliminary Design
Documents. 6. Urban Drainage and Flood Control District.
February 1997. Grange Hall Creek Major
Drainage-way Planning Study, Preliminary Design Report.
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104th and Colorado, Final Drainage Report
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APPENDIX
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VICINITY MAP
SITE
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104th and Colorado Proposed Hydrology.xls Summary
Design Point Contributing Basins
Area (acres)
5-Year (cfs)
100-Year (cfs)
1 SB50,SB70 0.82 2.0 4.42 SB10,SB20,SB30,SB40,SB50,SB60,SB70
2.37 6.1 13.2
3SB10,SB20,SB30,SB40,SB50,SB60,SB70, SB80,SB90 4.03 10.1
22.0
4SB10,SB20,SB30,SB40,SB50,SB60,SB70, SB80,SB90,SB125 4.20 10.3
22.6
5SB10,SB20,SB30,SB40,SB50,SB60,SB70,
SB80,SB90,SB100,SB110,SB120,SB125 5.08 11.3 24.5
6 OS20,OS30,SB130 2.87 4.3 12.4
Table A-1Summary of Site Hydrology
104th and ColoradoThornton, Colorado
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% Imp. C2 C5 C10035 0.25 0.33 0.5750 0.34 0.40 0.6080 0.60 0.63
0.742 0.04 0.15 0.5090 0.71 0.73 0.81
Area (acres) % Area (acres) % Area (acres) % Area (acres) % Area
(acres) %SB10 0.19 0 0.0% 0.00 0.0% 0.00 0.0% 0.00 0.0% 0.19 100.0%
100.00% 90% 0.71 0.73 0.81SB20 0.33 0 0.0% 0.00 0.0% 0.00 0.0% 0.00
0.0% 0.33 100.0% 100.00% 90% 0.71 0.73 0.81SB30 0.32 0 0.0% 0.00
0.0% 0.00 0.0% 0.00 0.0% 0.32 100.0% 100.00% 90% 0.71 0.73 0.81SB40
0.33 0 0.0% 0.00 0.0% 0.00 0.0% 0.00 0.0% 0.33 100.0% 100.00% 90%
0.71 0.73 0.81SB45 0.38 0 0.0% 0.00 0.0% 0.00 0.0% 0.00 0.0% 0.38
100.0% 100.00% 90% 0.71 0.73 0.81SB50 0.58 0 0.0% 0.00 0.0% 0.58
100.0% 0.00 0.0% 0.00 0.0% 100.00% 80% 0.60 0.63 0.74SB60 0.38 0
0.0% 0.00 0.0% 0.00 0.0% 0.00 0.0% 0.38 100.0% 100.00% 90% 0.71
0.73 0.81SB70 0.24 0 0.0% 0.00 0.0% 0.00 0.0% 0.00 0.0% 0.24 100.0%
100.00% 90% 0.71 0.73 0.81SB80 0.26 0 0.0% 0.00 0.0% 0.00 0.0% 0.00
0.0% 0.26 100.0% 100.00% 90% 0.71 0.73 0.81SB90 1.40 0 0.0% 0.00
0.0% 1.40 100.0% 0.00 0.0% 0.00 0.0% 100.00% 80% 0.60 0.63
0.74SB100 0.21 0 0.0% 0.00 0.0% 0.00 0.0% 0.00 0.0% 0.21 100.0%
100.00% 90% 0.71 0.73 0.81SB110 0.33 0 0.0% 0.00 0.0% 0.00 0.0%
0.00 0.0% 0.33 100.0% 100.00% 90% 0.71 0.73 0.81SB120 0.34 0 0.0%
0.00 0.0% 0.00 0.0% 0.00 0.0% 0.34 100.0% 100.00% 90% 0.71 0.73
0.81SB125 0.17 0 0.0% 0.00 0.0% 0.00 0.0% 0.00 0.0% 0.17 100.0%
100.00% 90% 0.71 0.73 0.81SB130 0.41 0 0.0% 0.00 0.0% 0 0.0% 0.00
0.0% 0.41 100.0% 100.00% 90% 0.71 0.73 0.81OS10 1.80 0 0.0% 0.00
0.0% 0 0.0% 0.00 0.0% 1.80 100.0% 100.00% 90% 0.71 0.73 0.81OS20
0.98 0 0.0% 0.00 0.0% 0 0.0% 0.00 0.0% 0.98 100.0% 100.00% 90% 0.71
0.73 0.81OS30 1.48 0 0.0% 0.00 0.0% 0 0.0% 1.48 100.0% 0.00 0.0%
100.00% 2% 0.04 0.15 0.50
Total 10.13 0.00 0.0% 0.00 0.0% 1.98 19.6% 1.48 14.6% 6.67 65.8%
100.00% 75% 0.59 0.63 0.75
1. From Table RO-3 and RO-5 in the UDFCD USDCM2. C coefficients
calculated by weighting global C values based on percentage of land
use type.
Commercial/Parking Lot
Subbasin Total Area (acres)
C Coefficient2Composite Imperviousness 5-year
Land Use Area per Sub-BasinResidential Parks/Open Space
100-yearLow Density Medium Density Apartments
2-yearCommercial/Parking Lot % Check
Global Parameters1
ApartmentsParks/Open Space
Table A-2C Value Calculations
Aria Stormwater Master planDenver, Colorado
Medium Density Residential
Land UseLow Density Residential
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104th and Colorado Proposed Hydrology.xls Q Peak 3 of 5
Tc Final Tc
Des
ign
Pt.
Basi
n ID
Area
C CA
C CA
C CA
Leng
th (3
00' m
ax)
Slop
e
ti Leng
th
Slop
e
Velo
city
tt tc=t
i+tt
Tota
l len
gth
Tc =
(l/1
80+1
0)
Fina
l Tc
2-ye
ar
5-ye
ar
100-
year
2-ye
ar
5-ye
ar
100-
year
acres ft % min. ft % fps min min ft min min in/hr cfs1 2 3 4 5 6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
SB50 0.58 0.60 0.35 0.63 0.37 0.74 0.43 200 2.0% 9.7 0 2.0% 3.0
0.0 9.7 200 11.1 9.7 2.60 3.67 7.04 0.9 1.3 3.0SB70 0.24 0.71 0.17
0.73 0.18 0.81 0.19 40 2.0% 3.4 0 0.8% 3.0 0.0 3.4 40 10.2 3.4 3.52
4.96 9.52 0.6 0.9 1.9
1 0.82 0.63 0.52 0.66 0.54 0.76 0.62 9.7 2.60 3.67 7.04 1.4 2.0
4.4
SB10 0.19 0.71 0.13 0.73 0.14 0.81 0.15 130 2.0% 6.1 330 2.0%
3.0 1.8 8.0 460 12.6 8.0 2.80 3.94 7.56 0.4 0.5 1.2SB20 0.33 0.71
0.23 0.73 0.24 0.81 0.27 100 2.0% 5.4 120 2.0% 3.0 0.7 6.1 220 11.2
6.1 3.06 4.31 8.27 0.7 1.0 2.2SB30 0.32 0.71 0.23 0.73 0.23 0.81
0.26 60 2.0% 4.2 100 2.0% 3.0 0.6 4.7 160 10.9 4.7 3.27 4.61 8.84
0.7 1.1 2.3SB40 0.33 0.71 0.23 0.73 0.24 0.81 0.27 100 2.0% 5.4 220
3.0% 3.0 1.2 6.6 320 11.8 6.6 2.97 4.20 8.05 0.7 1.0 2.2SB50 0.58
0.60 0.35 0.63 0.37 0.74 0.43 200 2.0% 9.7 0 2.0% 3.0 0.0 9.7 200
11.1 9.7 2.60 3.67 7.04 0.9 1.3 3.0SB60 0.38 0.71 0.27 0.73 0.28
0.81 0.31 300 2.0% 9.3 0 0.8% 3.0 0.0 9.3 300 11.7 9.3 2.64 3.72
7.14 0.7 1.0 2.2SB70 0.24 0.71 0.17 0.73 0.18 0.81 0.19 40 2.0% 3.4
0 0.8% 3.0 0.0 3.4 40 10.2 3.4 3.52 4.96 9.52 0.6 0.9 1.9
2 2.37 0.68 1.62 0.71 1.67 0.79 1.88 9.7 2.60 3.67 7.04 4.2 6.1
13.2
SB10 0.19 0.71 0.13 0.73 0.14 0.81 0.15 130 2.0% 6.1 520 2.0%
3.0 2.9 9.0 650 13.6 9.0 2.67 3.77 7.23 0.4 0.5 1.1SB20 0.33 0.71
0.23 0.73 0.24 0.81 0.27 100 2.0% 5.4 120 2.0% 3.0 0.7 6.1 220 11.2
6.1 3.06 4.31 8.27 0.7 1.0 2.2SB30 0.32 0.71 0.23 0.73 0.23 0.81
0.26 60 2.0% 4.2 100 2.0% 3.0 0.6 4.7 160 10.9 4.7 3.27 4.61 8.84
0.7 1.1 2.3SB40 0.33 0.71 0.23 0.73 0.24 0.81 0.27 100 2.0% 5.4 220
3.0% 3.0 1.2 6.6 320 11.8 6.6 2.97 4.20 8.05 0.7 1.0 2.2SB50 0.58
0.60 0.35 0.63 0.37 0.74 0.43 200 2.0% 9.7 0 2.0% 3.0 0.0 9.7 200
11.1 9.7 2.60 3.67 7.04 0.9 1.3 3.0SB60 0.38 0.71 0.27 0.73 0.28
0.81 0.31 300 2.0% 9.3 0 0.8% 3.0 0.0 9.3 300 11.7 9.3 2.64 3.72
7.14 0.7 1.0 2.2SB70 0.24 0.71 0.17 0.73 0.18 0.81 0.19 40 2.0% 3.4
0 0.8% 3.0 0.0 3.4 40 10.2 3.4 3.52 4.96 9.52 0.6 0.9 1.9SB80 0.26
0.71 0.18 0.73 0.19 0.81 0.21 40 2.0% 3.4 240 0.8% 2.0 2.0 5.4 280
11.6 5.4 3.16 4.45 8.54 0.6 0.8 1.8SB90 1.40 0.60 0.84 0.63 0.88
0.74 1.04 200 2.0% 9.7 0 2.0% 2.0 0.0 9.7 200 11.1 9.7 2.60 3.67
7.04 2.2 3.2 7.3
3 4.03 0.66 2.64 0.68 2.74 0.78 3.13 9.7 2.60 3.67 7.04 6.9 10.1
22.0
SB10 0.19 0.71 0.13 0.73 0.14 0.81 0.15 130 2.0% 6.1 720 2.0%
3.0 4.0 10.1 850 14.7 10.1 2.56 3.61 6.92 0.3 0.5 1.1SB20 0.33 0.71
0.23 0.73 0.24 0.81 0.27 100 2.0% 5.4 120 2.0% 3.0 0.7 6.1 220 11.2
6.1 3.06 4.31 8.27 0.7 1.0 2.2SB30 0.32 0.71 0.23 0.73 0.23 0.81
0.26 60 2.0% 4.2 100 2.0% 3.0 0.6 4.7 160 10.9 4.7 3.27 4.61 8.84
0.7 1.1 2.3SB40 0.33 0.71 0.23 0.73 0.24 0.81 0.27 100 2.0% 5.4 220
3.0% 3.0 1.2 6.6 320 11.8 6.6 2.97 4.20 8.05 0.7 1.0 2.2SB50 0.58
0.60 0.35 0.63 0.37 0.74 0.43 200 2.0% 9.7 0 2.0% 3.0 0.0 9.7 200
11.1 9.7 2.60 3.67 7.04 0.9 1.3 3.0SB60 0.38 0.71 0.27 0.73 0.28
0.81 0.31 300 2.0% 9.3 0 0.8% 3.0 0.0 9.3 300 11.7 9.3 2.64 3.72
7.14 0.7 1.0 2.2SB70 0.24 0.71 0.17 0.73 0.18 0.81 0.19 40 2.0% 3.4
0 0.8% 3.0 0.0 3.4 40 10.2 3.4 3.52 4.96 9.52 0.6 0.9 1.9SB80 0.26
0.71 0.18 0.73 0.19 0.81 0.21 40 2.0% 3.4 240 0.8% 2.0 2.0 5.4 280
11.6 5.4 3.16 4.45 8.54 0.6 0.8 1.8SB90 1.40 0.60 0.84 0.63 0.88
0.74 1.04 200 2.0% 9.7 0 2.0% 2.0 0.0 9.7 200 11.1 9.7 2.60 3.67
7.04 2.2 3.2 7.3
SB125 0.17 0.71 0.12 0.73 0.12 0.81 0.14 120 2.0% 5.9 150 3.0%
3.0 0.8 6.7 270 11.5 6.7 2.96 4.17 8.00 0.4 0.5 1.14 4.20 0.66 2.76
0.68 2.87 0.78 3.26 10.1 2.56 3.61 6.92 7.1 10.3 22.6
SB10 0.19 0.71 0.13 0.73 0.14 0.81 0.15 130 2.0% 6.1 800 2.0%
3.0 4.4 10.6 930 15.2 10.6 2.51 3.54 6.80 0.3 0.5 1.0SB20 0.33 0.71
0.23 0.73 0.24 0.81 0.27 100 2.0% 5.4 120 2.0% 3.0 0.7 6.1 220 11.2
6.1 3.06 4.31 8.27 0.7 1.0 2.2SB30 0.32 0.71 0.23 0.73 0.23 0.81
0.26 60 2.0% 4.2 100 2.0% 3.0 0.6 4.7 160 10.9 4.7 3.27 4.61 8.84
0.7 1.1 2.3SB40 0.33 0.71 0.23 0.73 0.24 0.81 0.27 100 2.0% 5.4 220
3.0% 3.0 1.2 6.6 320 11.8 6.6 2.97 4.20 8.05 0.7 1.0 2.2SB50 0.58
0.60 0.35 0.63 0.37 0.74 0.43 200 2.0% 9.7 650 2.0% 3.0 3.6 13.3
850 14.7 13.3 2.28 3.22 6.17 0.8 1.2 2.6SB60 0.38 0.71 0.27 0.73
0.28 0.81 0.31 300 2.0% 9.3 0 0.8% 3.0 0.0 9.3 300 11.7 9.3 2.64
3.72 7.14 0.7 1.0 2.2SB70 0.24 0.71 0.17 0.73 0.18 0.81 0.19 40
2.0% 3.4 0 0.8% 3.0 0.0 3.4 40 10.2 3.4 3.52 4.96 9.52 0.6 0.9
1.9SB80 0.26 0.71 0.18 0.73 0.19 0.81 0.21 40 2.0% 3.4 240 0.8% 2.0
2.0 5.4 280 11.6 5.4 3.16 4.45 8.54 0.6 0.8 1.8SB90 1.40 0.60 0.84
0.63 0.88 0.74 1.04 200 2.0% 9.7 0 2.0% 2.0 0.0 9.7 200 11.1 9.7
2.60 3.67 7.04 2.2 3.2 7.3
SB100 0.21 0.71 0.15 0.73 0.15 0.81 0.17 60 2.0% 4.2 140 0.8%
2.0 1.2 5.3 200 11.1 5.3 3.17 4.47 8.57 0.5 0.7 1.5SB110 0.33 0.71
0.23 0.73 0.24 0.81 0.27 110 2.0% 5.6 160 3.0% 3.0 0.9 6.5 270 11.5
6.5 2.98 4.21 8.07 0.7 1.0 2.1
Table A-3Rational Method Hydrologic Calculations
Aria Stormwater Master PlanDenver, Colorado
Sub-Basin DataOverland Time (ti) Travel Time (tt) Tc Check
Time of Concentration, Tc2-year 5-year 100-year
C Values Intensity, I Peak Discharge, Q
-
104th and Colorado Proposed Hydrology.xls Q Peak 4 of 5
Tc Final Tc
Des
ign
Pt.
Basi
n ID
Area
C CA
C CA
C CA
Leng
th (3
00' m
ax)
Slop
e
ti Leng
th
Slop
e
Velo
city
tt tc=t
i+tt
Tota
l len
gth
Tc =
(l/1
80+1
0)
Fina
l Tc
2-ye
ar
5-ye
ar
100-
year
2-ye
ar
5-ye
ar
100-
year
acres ft % min. ft % fps min min ft min min in/hr cfs1 2 3 4 5 6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Table A-3Rational Method Hydrologic Calculations
Aria Stormwater Master PlanDenver, Colorado
Sub-Basin DataOverland Time (ti) Travel Time (tt) Tc Check
Time of Concentration, Tc2-year 5-year 100-year
C Values Intensity, I Peak Discharge, Q
SB120 0.34 0.71 0.24 0.73 0.25 0.81 0.28 100 2.0% 5.4 160 3.0%
3.0 0.9 6.3 260 11.4 6.3 3.02 4.26 8.18 0.7 1.1 2.3SB125 0.17 0.71
0.12 0.73 0.12 0.81 0.14 120 2.0% 5.9 150 3.0% 3.0 0.8 6.7 270 11.5
6.7 2.96 4.17 8.00 0.4 0.5 1.1
5 5.08 0.67 3.39 0.69 3.51 0.78 3.97 13.3 2.28 3.22 6.17 7.7
11.3 24.5
OS20 0.98 0.71 0.70 0.73 0.72 0.81 0.79 100 2.0% 5.4 120 2.0%
3.0 0.7 6.1 220 11.2 6.1 3.06 4.31 8.27 2.1 3.1 6.6OS30 1.48 0.04
0.06 0.15 0.22 0.50 0.74 100 2.0% 13.8 120 2.0% 3.0 0.7 14.5 220
11.2 11.2 2.45 3.46 6.64 0.1 0.8 4.9SB130 0.41 0.71 0.29 0.73 0.30
0.81 0.33 60 2.0% 4.2 100 2.0% 3.0 0.6 4.7 160 10.9 4.7 3.27 4.61
8.84 1.0 1.4 2.9
6 2.87 0.36 1.05 0.43 1.24 0.65 1.87 11.2 2.45 3.46 6.64 2.6 4.3
12.4
Notes:
2. I = 28.5P1/(10+Tc)0.786
3. Ti = 0.395(1.1-C5)(L)0.5/S0.33
4. Minimun Tc is 5.0 minutes for urban areas.
1. Flows calculated using the rational method, based on the
methods provided in chapter 4 section 4 (rainfall), and Chapter 5
Section 2 (runoff) of the USDCM by UDFCD (2008).
-
104th and Colorado Proposed Hydrology.xls Rainfall
Recurrence Interval (yrs) 1-hr Rainfall Depth (in)
2 0.955 1.3410 1.5525 2.0050 2.25100 2.57
Note: From TOCR Criteria Manual
Table A-4Rainfall Data
Denver, Colorado
-
Steam UD-Detention_v2.35.xls 11/22/2015, 10:31 PM
Project:Basin ID:
32.48
69.0%
0
69.0%
Percentage of Area Area (acres)0.00.0
100.0% 32.5
Initial--f i Final--fo3 0.5 0.0018
(watershed inches) (acre-feet)
0.83 2.24 Design Oulet to Empty EURV in 72 Hours
100-year Detention Volume Including WQCV 5 1.45 3.92 32.48
Notes:
Hydrologic Soil TypeType AType B
Excess Urban Runoff Volume4
Infiltration (inches per hour)
Maximum Allowable Release Rate, cfs3
4) EURV approximates the difference between developed and
pre-developed runoff volume.5) 100-yr detention volume includes
EURV. No need to add more volume for WQCV or EURV
Detention Volumes 2,5
DETENTION VOLUME BY THE FULL SPECTRUM METHOD
104th and ColoradoRegional Detention Pond
1) Effective imperviousness is based on Figure ND-1 of the Urban
Storm Drainage Criteria Manual (USDCM).
Area of Watershed (acres)
Subwatershed ImperviousnessLevel of Minimizing Directly
Connected
Impervious Area (MDCIA)
* User input data shown in blue.
2) Results shown reflect runoff reduction from Level 1 or 2
MDCIA and are plotted at the watershed's total imperviousness
value; the impact of MDCIA is reflected by the results being below
the curves.3) Maximum allowable release rates for 100-year event
are based on Table SO-1. Outlet for the Excess Urban Runoff Volume
(EURV) to be designed to empty out the EURV in 72 hours. Outlet
design is similar to one for the WQCV outlet of an extended
detention basin (i.e., perforated plate with a micro-pool) and
extends to top of EURV water surface elevation.
Recommended Horton's Equation Parameters for CUHP
Effective Imperviousness1
Type C or D
Decay Coefficient--a
0.00
0.50
1.00
1.50
2.00
2.50
0 20 40 60 80 100
Runo
ff Vo
ume
- Inc
hes
Percent Total Imperviousness
100-yr Vol Type A Soil
100-yr Vol Type B, C & D Soils
EURV Type A Soil
EURV Type B Soil
EURV Type C/D Soil
100-yr Storage Volume
EURV Storage Volume
-
Incremental Total Incremental Total5163.0 Pond Bottom 0 0 75 0 0
0.005164.0 1 1 75 75 75 0.005165.0 1 2 2,000 821 896 0.025166.0 1 3
7,037 4,263 5,159 0.125167.0 1 4 13,461 10,077 15,236 0.355168.0 1
5 20,229 16,731 31,966 0.735169.0 1 6 24,513 22,337 54,303
1.255170.0 EURV 1 7 28,883 26,668 80,971 1.865171.0 1 8 33,308
31,069 112,040 2.575172.0 100-year 1 9 37,845 35,552 147,593
3.39
1. Calculated using the Conical method.
Table 1Stage, Storage Data
60% RTD Pond
Elevation (ft., NAVD88) Description Depth (ft.) Area (sf) Volume
(cubic-feet)1
Volume AF
104th and Colorado
-
Incremental Total Incremental Total5163.0 Pond Bottom 0 0 75 0 0
0.005164.0 1 1 75 75 75 0.005165.0 1 2 2,000 821 896 0.025166.0 1 3
7,037 4,263 5,159 0.125167.0 1 4 16,880 11,605 16,764 0.385168.0 1
5 26,010 21,281 38,045 0.875169.0 1 6 31,100 28,517 66,562
1.535170.0 EURV 1 7 35,592 33,321 99,883 2.295171.0 1 8 41,380
38,450 138,333 3.185172.0 100-year 1 9 46,180 43,758 182,091
4.18
1. Calculated using the Conical method.
Table 1Stage, Storage Data
Expanded Pond to Include 104th Site104th and Colorado
Elevation (ft., NAVD88) Description Depth (ft.) Area (sf) Volume
(cubic-feet)1
Volume AF
-
Project Description
Friction Method Manning Formula
Solve For Full Flow Capacity
Input Data
Roughness Coefficient 0.013
Channel Slope 0.00400 ft/ft
Normal Depth 2.50 ft
Diameter 2.50 ft
Discharge 25.94 ft³/s
Rating Curve Plot
Rating Curve for Circular Pipe - 1
11/22/2015 8:36:11 PMBentley Systems, Inc. Haestad Methods
Solution CenterBentley FlowMaster V8i (SELECTseries 1)
[08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA
+1-203-755-1666 1of1Page
-
ResultsOpening
Area (sq.ft.) C
% Blockage H (ft)
Weir length (ft.)
% Blockage C H (ft)
100-Yr Ponding
Depth (ft.)
1 S-63 1 R 4.4 2.5 0.67 10% 0.13 5 10% 3.0 0.47 0.472 S-73 1 C
9.0 6 0.67 50% 0.31 12 50% 3.0 0.63 0.633 S-66 1 C 1.8 6 0.67 50%
0.01 12 50% 3.0 0.22 0.224 S-82 1 C 7.3 6 0.67 50% 0.20 12 50% 3.0
0.55 0.555 S-76 1 R 1.1 2.5 0.67 10% 0.01 5 10% 3.0 0.19 0.196 S-79
1 R 3.6 2.5 0.67 10% 0.09 5 10% 3.0 0.41 0.417 S-77 1 R 2.2 2.5
0.67 10% 0.03 5 10% 3.0 0.30 0.308 S-86 1 C 3.2 6 0.67 50% 0.04 12
50% 3.0 0.32 0.329 S-85 1 R 2.9 2.5 0.67 10% 0.06 5 10% 3.0 0.36
0.36
1. Orifice Equation: Q = (1-%blockage) CA (2gH)0.5
2. Weir Equation: Q = (1-%blockage) CLH1.5
No. of Inlets
Table 3Inlet Ponding Depth Calculations
100-year Design EventInlets in a Sag
Inlet ID Description Inlet Type 100-yr Q (cfs)
Orifice Calcs1 Weir Calcs2
-
Hydrologic Soil Group—Adams County Area, Parts of Adams and
Denver Counties, Colorado(104th and Colorado)
Natural ResourcesConservation Service
Web Soil SurveyNational Cooperative Soil Survey
11/22/2015Page 1 of 4
4414
700
4414
740
4414
780
4414
820
4414
860
4414
900
4414
940
4414
980
4414
700
4414
740
4414
780
4414
820
4414
860
4414
900
4414
940
4414
980
505160 505200 505240 505280 505320 505360 505400
505160 505200 505240 505280 505320 505360 505400
39° 53' 6'' N10
4° 5
6' 2
2'' W
39° 53' 6'' N
104°
56'
12'
' W
39° 52' 55'' N
104°
56'
22'
' W
39° 52' 55'' N
104°
56'
12'
' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge
tics: UTM Zone 13N WGS840 50 100 200 300
Feet0 20 40 80 120
MetersMap Scale: 1:1,590 if printed on A portrait (8.5" x 11")
sheet.
-
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)Area of Interest (AOI)
SoilsSoil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating LinesA
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating PointsA
A/D
B
B/D
C
C/D
D
Not rated or not available
Water FeaturesStreams and Canals
TransportationRails
Interstate Highways
US Routes
Major Roads
Local Roads
BackgroundAerial Photography
The soil surveys that comprise your AOI were mapped at
1:20,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can
causemisunderstanding of the detail of mapping and accuracy of soil
lineplacement. The maps do not show the small areas of
contrastingsoils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for
mapmeasurements.
Source of Map: Natural Resources Conservation ServiceWeb Soil
Survey URL: http://websoilsurvey.nrcs.usda.govCoordinate System:
Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web
Mercatorprojection, which preserves direction and shape but
distortsdistance and area. A projection that preserves area, such
as theAlbers equal-area conic projection, should be used if more
accuratecalculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
ofthe version date(s) listed below.
Soil Survey Area: Adams County Area, Parts of Adams andDenver
Counties, ColoradoSurvey Area Data: Version 12, Sep 22, 2015
Soil map units are labeled (as space allows) for map scales
1:50,000or larger.
Date(s) aerial images were photographed: Aug 30, 2014—Sep18,
2014
The orthophoto or other base map on which the soil lines
werecompiled and digitized probably differs from the
backgroundimagery displayed on these maps. As a result, some minor
shiftingof map unit boundaries may be evident.
Hydrologic Soil Group—Adams County Area, Parts of Adams and
Denver Counties, Colorado(104th and Colorado)
Natural ResourcesConservation Service
Web Soil SurveyNational Cooperative Soil Survey
11/22/2015Page 2 of 4
-
Hydrologic Soil Group
Hydrologic Soil Group— Summary by Map Unit — Adams County Area,
Parts of Adams and Denver Counties, Colorado(CO001)
Map unit symbol Map unit name Rating Acres in AOI Percent of
AOI
PlB Platner loam, 0 to 3percent slopes
C 5.8 62.9%
ReD Renohill loam, 3 to 9percent slopes
D 0.2 1.7%
UlC Ulm loam, 3 to 5 percentslopes
C 3.3 35.3%
Totals for Area of Interest 9.3 100.0%
Description
Hydrologic soil groups are based on estimates of runoff
potential. Soils areassigned to one of four groups according to the
rate of water infiltration when thesoils are not protected by
vegetation, are thoroughly wet, and receive precipitationfrom
long-duration storms.
The soils in the United States are assigned to four groups (A,
B, C, and D) andthree dual classes (A/D, B/D, and C/D). The groups
are defined as follows:
Group A. Soils having a high infiltration rate (low runoff
potential) when thoroughlywet. These consist mainly of deep, well
drained to excessively drained sands orgravelly sands. These soils
have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when
thoroughly wet. Theseconsist chiefly of moderately deep or deep,
moderately well drained or well drainedsoils that have moderately
fine texture to moderately coarse texture. These soilshave a
moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly
wet. These consistchiefly of soils having a layer that impedes the
downward movement of water orsoils of moderately fine texture or
fine texture. These soils have a slow rate of
watertransmission.
Group D. Soils having a very slow infiltration rate (high runoff
potential) whenthoroughly wet. These consist chiefly of clays that
have a high shrink-swellpotential, soils that have a high water
table, soils that have a claypan or clay layerat or near the
surface, and soils that are shallow over nearly impervious
material.These soils have a very slow rate of water
transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or
C/D), the first letter isfor drained areas and the second is for
undrained areas. Only the soils that in theirnatural condition are
in group D are assigned to dual classes.
Hydrologic Soil Group—Adams County Area, Parts of Adams and
Denver Counties, Colorado 104th and Colorado
Natural ResourcesConservation Service
Web Soil SurveyNational Cooperative Soil Survey
11/22/2015Page 3 of 4
-
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Adams County Area, Parts of Adams and
Denver Counties, Colorado 104th and Colorado
Natural ResourcesConservation Service
Web Soil SurveyNational Cooperative Soil Survey
11/22/2015Page 4 of 4
-
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Proposed Apartment DevelopmentSE of East 104th Avenue and
Colorado Boulevard - Thornton, COPCH Project No. 12.431.14
SUMMARY OF LABORATORY TEST RESULTS
Pickering, Cole and Hivner, LLC 1070 W. 124th Ave., Suite 300 •
Westminster, Colorado 80234
LL PL PI
1 4 Sandy Lean Clay 7.3% 130 +5.2 500
1 9 Sandy Lean Clay 11.2% 120 51 31 20 11
1 14 Sandstone Bedrock 15.9% 108
1 19 Sandstone Bedrock 19.2% 107
1 24 Sandstone Bedrock 18.5% 107
2 4 Clayey Sand 8.3% 128 49 27 21 6
2 9 Sandstone Bedrock 3.7% 111
2 14 Claystone Bedrock 20.2% 108 +2.4 1,000
2 19 Claystone Bedrock 17.0% 114
2 24 Claystone Bedrock 13.9% 116
2 34 Claystone Bedrock 12.7% 119
3 2 Lean Clay with Sand 11.7% 113 75 45 18 27
3 4 Lean Clay with Sand 15.8% 105 +6.8 500 6,900
3 9 Lean Clay with Sand 17.8% 112 +5.4 500 5,800
3 14 Claystone/Sandstone Bedrock 15.0% 105
4 4 Silty Sand 7.2% 119 30
4 9 Silty Sand 7.7% 121 26
4 14 Claystone/Sandstone Bedrock 13.9% 122 +1.8 1,000
5 4 Sandy Lean Clay 14.4% 120 +6.0 500
5 9 Sandy Lean Clay 14.9% 115 51 29 21 8
5 14 Sandy Lean Clay 20.9% 105
5 19 Sandy Lean Clay 18.2% 116
5 24 Claystone Bedrock 18.1% 112
5 34 Claystone Bedrock 16.4% 116
6 4 Sandy Lean Clay 10.4% 118 66 37 19 18
6 9 Sandy Lean Clay 14.0% 1066 14 Sandy Lean Clay 19.8% 108 -1.2
1,000
Non-plastic
Non-plastic
Surcharge Pressure (psf)
Passing #200 Sieve (%)
Atterberg LimitsSwell (+) or Consolidation (-)
(%)
Water Soluble Sulfates (ppm)
Test Boring
Depth (ft) Soil Description
Dry Density
(pcf)
Moisture Content
(%)
-
N
1 INCH = FT.
0 50 100
50
BASIN RUNOFF SUMMARY
LEGEND
EASEMENT (BY SEPARATE DOCUMENT)
PROPERTY LINE
EXISTING FENCE
EXISTING CURB AND GUTTER
EXISTING WATER LINE
EXISTING UNDERGROUND COMM
EXISTING STORM SEWER
EXISTING SANITARY SEWER
EXISTING GAS LINE
EXISTING UNDERGROUND ELECTRIC
EXISTING STORM MANHOLE
EXISTING INLET
EXISTING SANITARY MANHOLE
EXISTING FIRE HYDRANT
BUILDING
6" CURB AND GUTTER
STORM SEWER
SANITARY SEWER
WATER LINE
STORM SEWER MANHOLE
INLET
SANITARY SEWER MANHOLE
FIRE HYDRANT
WATER METER
DRAINAGE FLOW PATTERN DIRECTION
BASIN AREA/C5/C100
DESIGNATOR
DATE:
DESIGNED BY:
PROJECT NO:
DRAWN BY:
11
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Know what's
R
CALL UTILITY NOTIFICATION
CENTER OF COLORADO
CALL 3-BUSINESS DAYS (NOT INCLUDING INITIAL
DAY OF CONTACT) IN ADVANCE BEFORE YOU DIG,
GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
0-104th and Colorado Drainage Report 11-04-20151.0 GENERAL
LOCATION AND DESCRIPTION2.0 DRAINAGE BASINS AND SUB-BASINS3.0
DRAINAGE DESIGN CRITERIA4.0 DRAINAGE FACILITY DESIGN5.0
CONCLUSIONS6.0 REFERENCES
1 vicinity map2 104th and Colorado Proposed HydrologySummaryC
CoeffQ PeakRainfall
3 104th EURV UD-Detention_v2.35Full-Spectrum
4 104th Pond Volumes60% RTD PondExpanded Pond
5 Hydraulic calcs6 inletsSag Inlets
7 NRCS Soils Info8 Geotech Report Excerpts9 drainage map