HomeMy WebLinkAboutDrainage ReportDrainage Report
Cooper Subdivision - Lot 2, Building A
Garfield County, CO
Prepared for:
Building Permit
Prepared by:
$opris Englneerlng, LLC
502 Main Street Suite A3
Carbondale, Colorado 81623
0n Behalf of:
CltadelGlenwood LLC
SE Project Number; 30017.04
March 5,2024
for
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Vl. Detain and Treat runoff (7-204.C.3)............
Vll. Hydraulic Analysis Methods & Assumptions
Appendix
A. 05.0 - Drainage Exhibit
ADS Banacuda Water Quality
Purpose of Drainage Study.......... ...,..,....2
General0verview & Site Description,........... ..............2
Erosion and $edimentation (7-204.A1 .........................2
3
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SE #30017 Cooper Subdivision - Lot 2, Bldg A Drainage Report March 5, 2024
Page 2
l. Purpose of Drainage Study
The purpose of this Drainage Study is to:o Provide Best Management Practice (BMP) recommendations to minimize sediment transport offsite
,D Estimate the post development peak runoff rates in support of sizing of stormwater mitigation
infrastructure.o Provide detention volumes such that post development runoff rates do not exceed the developed peak
runoff rates for the 5-year storm events. Note as detailed in the Minor Subdivision Engineering
Report, this project's dqsign is site specific in compliance with lhe agreement with the Mall property to
the south. The existing stormwater drainage infrastructure has been sized from this site and the mall
site to convey the developed 5 year stormwater runoff directly to Mitchell Creek / Colorado River
,D Provide for storm water quality treatment for the stormwater runoff from streets and parking areas
onsite (As detailed in the Minor Subdivision Engineering Report).
This drainage report provides the final Lot 2 calculations for building permit submittals as preliminarily outlined
in the Minor Subdivision Engineering Report.
ll. General Overview & Site Description
This memo provides the final drainage calculations for Building A and for the Lot 2 street improvements.
Building B & C improvements will be final confirmed fortheir respective building permit submittal.
The subject property is located directly north of the West Glenwood Mall, north of State Highway 6, east of
Storm King Road, south of County Road (130) Donegan Road, and west of the residential units along the west
side of County Road 133 (Mel Ray Road), Lot 2 is 7.879 acres. Building A is in the northwest corner of the
site. Center Drive will be extended to the east and a new road called Chapparal Drive will connect to County
Road 130 (Donegan Road) at the intersection with Chapparal Circle.
The Garlield County code requirements are covered in section 7-204: Drainage & Erosion. The report sections
are divided following the respective Garfield County code section.
lll. Erosion and Sedimentation (7-2O4,A)
The project will disturb more than one acre and thus will apply for and receive a state storm water permit from
the Colorado Department of Public Health and Environments (CDPHE) National Pollutant Discharge
Elimination System prior to construction. The contractor will need to prepare a detailed stormwater
management plan {SWMP) for the site. This detailed plan will be updated during construction as necessary to
properly manage erosion and sedimentation.
Standard erosion and sedimentation best management practices (BMP's) will be applied to this site. These
BMP's are primarily grouped for two stages of the development; the temporary construction phase and the
permanent post development phase. The main emphasis for both stages is on soil erosion and sediment
transport controls.
Temporary Erosion Control: During the construction phase for the proposed improvements, there will be
potential for soil erosion and offsite sediment transport, triggered by surface runoff during rain events. The
conlractor must at a minimum install and maintain the following BMPs during the construction phase:
r' An embedded silt fence around the disturbed soils and especially in the low receiving ends of the
slopes.
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SE #30017 Cooper Subdivision - Lot 2, Blds A Drainase Reoort March 5. 2024
Page 3
,/ Prior to any clearing and grubbing, lot grading, and prior to any construction work, the contractor must
construct temporary sediment basins in strategically located areas in order to collect runoff sediment
and stop sediment from traveling offsite.{ The site must be inspected at the end of every 14-day period during construction, and silt deposits
from behind the silt fencing and from the sediment pits must be removed regularly to ensure full
functioning of this erosion control system. These activities must be logged in a logbook available at the
site for inspection at all times./ Vehicle tracking pads (mud racks) at the site entrance(s) must be installed to avoid mud tracking into
public right of way.,/ Seed & mulch must be placed over disturbed cut and fill slopes,.and watered as necessary, to
establish temporary vegetative ground cover until paving, gravel surface and/or landscaping is done.
A construction site can be a very dynamic area; because of this the contractor is responsible for the final
location and selection of construction BMPs. The criteria outlined within the state storm water permit must be
adhered to unti! permanent BMPs are established and the permit has been closed.
Permanent BMPs shall consist of complete landscaping and ground covering to permanently re-vegetate and
cover bare grounds that will remain open space to avoid long-term soil erosion. This effort will reduce the risk
of unnecessary degradation and failure of the drainage system. Temporary erosion control structures installed
during construction shall be left in place as necessary and shall be maintained until new vegetation has been
reestablished ata70o/o level. Upon reaching a satisfactory level of soil stabilization from the new vegetation all
erosion conhol structures shall be removed.
lV. Drainage (7-2O4.Bl
The site grading and drainage has been developed to provide positive drainage away from all structures in
coordination with the area storm drainage patterns. The drainage patterns and preliminary design are
described in detail in the Minor Subdivision Engineering report. This report details the final drainage and water
quality design for the building permit submittal
The existing site is directly connected to the exisling storm sewer main lines on the mall property. These
storm sewer lines flow down to State Highway 6 and then flow west to daylight in the Mitchell Creek culvert
under Highway 6. This pipe termination is approximately 400 feet upsheam of the Mitchell creek confluence
with the Colorado River. The Glenwood Business Center has agreements with the mall site that indicates the
existing storm sewer system was designed for and will accept the developed 5 year storm event from onsite.
At a minimum the site storm water runoff will be detained to the 5 year developed storm.
Ofbite Drainaqe
SE walked the drainage areas above and below the site, researched storm water as-builts and reviewed old
drainage reports. The majority of the offsite storm water runoff flows around the site in Storm King Road and
Mel Ray Road. The small drainage basins directly north of the site will be routed in storm sewer pipes through
the site.
Onsite drainaqe:
The methodology for estimating the proposed storm water runoff rates and volumes are discussed in $ection V
below and the results are summarized on civil sheet C5.0.
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Page 4
V. Stormwater Run-Off (7-2O4-Cl
The drainage basins were analyzed using the Rational Method (Equation 1), as the cumulative total of tributary
offsite and onsite basins are less than 90 acres.
Equationl:Q=C*l*A
Q = Runoff Flow Rate (cfs); C = Runoff Coefficient
| = Rainfall lntensity (in/hr); A= Area of Basin {acres)
The runoff coefficient (G) is a variable that represents the ratio of runoff to rainfall volumes during a storm
event. The determination of C mainly depends on the soil type, watershed impervious and storm event
frequency.
The soil type was determined from the soil survey provided by the National Resource Conservation Service
(NRCS). The onsite soils consist of Type 'C' Hydrologic Soils. Type 'C' soils have a dow infiltration rates with
modOrately fine or fine textured soils.
Each drainage basin was studied to determine the percent of impervious area. The Mile High Flood District
(MHFD)(formerly UDFCD) out of Denver, CO has developed runoff coefficient tables in Chapter 6 of Volume 1
of their Urban Storm Drainage Criteria Manual. Table 6-5 was used to determine the conesponding weighted
average runoff coefficients based on the storm event and a Type C hydrologic soil classification.
The design rainfall duration used in the Rational Method is referred to as the time of concentration. The time
of concentration is the cumulative travel time, including overland flow and channelized flow, for runoff to get
from the furthest point upstream of a basin to a designated design point. The existing basins'time of
concentration was calculated using the TR-55 method. A minimum time of concentration of 10 minutes was
used for all developed basins given the size of the basins, the percent impervious, and the relatively short
travel distances.
The rainfall intensity was derived from the NOAA 14 lntensity Duration Frequency (lDF) Curve for Glenwood
Springs, CO.
The site has been analyzed for the existing and developed peak rainfall runoff for storm water system sizing.
As mentioned above the mall site has storm sewer infrastructure that can accept the 5 year developed storm
from this site. The rate of runoff for the 25 year event will be restricted to the 5 year developed rate by an
orifice or smaller pipe outflow. The runoff rates are summarized on civil sheet C5.0.
Vl. Detain and Treat runoff (7-2O4.C.31
This site will detain the slormwater runoff to the 5 year developed peak rate and then will be safely conveyed
directly to Mitchell Creek just upstream of the confluence with the Colorado River. The storm water runoff from
the Lot 2 street and parking areas will be treated for water quality before leaving the site.
The Mile High Flood District (MHFD) has extensive literature, research, and calculation methods for water
quality treatment. SE has reviewed the Criteria Manual Volume 3 which calculates water quality treatment
based on total rainfall depth from a storm event in the Denver Area. SE also analyzed the Water quality
treatment criteria in lhe City of Aspen's Urban Runoff Management Plan (URMP). This also considers rainfall
depth, but with storm pattems closer to the West Glenwood Springs. The URMP storage depth is 0.26 inches
from a 100% impervious area.
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SE #30017 Cooper Subdivision - Lot 2. Blde A Drainaee Reoort March 5. 2024
Page 5
ln order to establish a sizing method that is based on a florll rate, SE calculated the rainfall from the high
intensity, short duration slonn events to establish a water quality storm. The 2 year 10 minute storm intensity
is 1.55 inches, so for the 10 minute duration the total rainfall depth would be 0.26 inches. For lower intensity,
longer duration storms the rainfall depth that is heated will be higher. The 25 year t hour storm event for
example has an intensity and depth of rainfall of 1.05 inches, but the peak flow rates would be similar to the 2
year 10 minute peak. This demonstrates the benefit of water quality treatment based on flow rate; larger
volume runoff rates will also be lreated, and the treatment happens in line with the storm sewer runoff.
Water Quality $wales:
For Building A, the street and parking will sheet flow direct to the site drainage swales. These swales have
long sections of 1-2o/o slopes which will slow down the storm water runoff and allow for infiltration of the first
flush for water quality lreatrnent. This approach provides a simple water quality with minimal maintenance or
clogging potential.
Water Treatment Manholes:
For Center Drive and Chapparal Road, the storm water runoff will flow through water quality treatment
manholes. Our civil plans specify ADS Banacuda manholes which are described as a vortex hydrodynamic
separator designed to remove at least 80 percent of Total Suspended Solids (TSS) while capable of carrying
100 percent of the design peak flow. The manhole allows for surface inspection and maintenance using a
vacuum truck. The water quality treatment for the Center Drive extension and Chapparal Road is described
below, and the Barracuda sizing documentation is induded in the report Appendix. Appropriate details are
included on the civil construction plans.
Note the treated storm water runoff then flows to site detention basins which have conholled release pipes.
This will allow for additional settling of solids prior to release.
Vll. Hydraulic Analysis Methods & Assumptions
Storm water runoff is routed on the surface via sheet flow and in drainage swales, and is then routed in storm
sewer pipes which daylight into drywells. The hydraulic capacity calculations have been separated by standard
pipe sizes for site storm water drainage with a minimum 2% slope. The pipes onsite have been sized
according to the design flows. Supporting hydraulic data for all of the calculations has been provided within
Appendix B. Each of the gravity storm channels were sized using Manning's Equation (Equation 2).
Equation 2:Q= 1.49/n. R28 *A *$io'o
Q= Runoff Flow Rate (cfsl; n = Manning's Roughness Coefficient
R= Hydraulic Radius (t0; n= How Area (sfl, S = Channel Slope (ffi
The hydraulic capacity calculations have been separated by standard pipe sizes for site storm water drainage
with a minimum 2% slope. ln general the pipes onsite collect storm water from small subareas within the
larger drainage basins. The onsite pipes will be sized according to the contributing flow area and peak runoff
rate. Table 1 below summarizes the approximate 80% full pipe capacity.
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SE #30017 Cooper Subdivision - Lot 2, Blds A Drainaqe Report March 5, 2024
Page 5
Vlll. Maintenance
lnspection of inlets and swales should occur and clean out of storm inlet sump basins be performed to keep
the itorm sewer pipe clear of debris. The water quality manholes have specilic maintenance procedures with
outlined schedules. This maintenance should be incorporated into site maintenance schedules and be
performed by property management.
lX. Gonclusions
The results of this drainage study support the drainage calculations and direction provided in the Minor
Subdivision Engineering Report^ The offsite drainage primarily flows around the site. Offsite storm water runoff
that enters the site will be rouled around and through the site. Lot 2 will provide for water quality as well as
detention to the 5 year developed rate. The storm water runoff will then connect to the offsite storm sewer
pipes that daylights at Mitchell Creek just upstream of the Colorado River. Best Management Practices
(BMPs) will be detailed in the contractor's SWMP and will be implemented during the construction of the
improvements. Permanent vegetated cover will be installed as soon as construction allows.
Slope Capacity {CFS)Pioe Size (lN)Pipe Material Manning's n
0.012 2.OO%1.006Solid PVC
o.aLz 2.OO%2.188Solid PVC
0.012 2.OO%6.35t2ADS N12
17.15o.o12 2.OO%18 ADS N12
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ENGINEERING LLC
BUILDING PERMIT
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GLENWOOD BUSINESS CENTER:
LOT 2, BUILDING A
GARFIELD COUNTY, COLORADO
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ADS'Barracuda'" Max
The Barracuda Max ls market-changing stormwater quality technology. This high-performance vortex
hydrodynamic separator is designed to remove total suspended solids in order to protect our precious receiving
waters. The Barracuda Max is also an outstanding value that offers multlple pipe configurations, and quick
installation. The "Max" version of the Barracuda is built on the base platform of the original ADS Barracuda with
i mproved removal efflciencles and insta llation components.
Features
. Single manhole design
. No elevation loss between the inlet and outlet
. Variable inlet/outlet angle configurations (not just
1 80 degree orientation)
. Internal bypass for inline installation (where
applicable)
' Revolutionary, patent-pending "teeth" mitigate
turbulence in the sump area to prevent re-
suspension of captured contamlnants and an added
deflector plate and bowl extension enhance the
unit's removal capabilities
Beneflts
r Internal components are in stock for quick delivery
. The 53, 54, 56, and SB can be lnstalled in a standard
36" (900 mm),48" (1200 m),72" (1800 m), and
96" (2400 m) precast manhole, respectively
. The 53 & 54 can be provided factory installed
within a 36" (900 mm) and 48" (1200 mm)RoS
HP manhole and delivered to the jobsite
. The Barracuda Max "teeth" and deflector
plate apparatus are fabricated and designed
for qulck and easy field assembly. Designed for easy maintenance using a
vacuum truck or similar equipment.
. Inspection and maintenance are performed
from the surface with no confined space entry
Barrucuda Specification
Materials and Design
. Concrete Structures: Designed for H-20 traffic loading and applicable soil loads or
as otherwise determined by a Licensed Professional Engineer. The materials and
structural design ofthe devices shall be per ASTM C857 and ASTM C858.
. 36" {900 mm) and 48" (1200 mm) He Manhole Structures: Made from an impact modified
copolymer polypropylene meeting the material requlrements of ASTM F2764. The eccentric
cone reducer shall be manufactured from polyethylene material meeting ASTM D3350 cell class
213320C. Gaskets shall be made of material meeting the requirements of ASTM F477.
. Separator internals shall be substantially consffucted of stainless steel, polyethylene
or other thermoplastic material approved by the manufacturer,
Performance
. Thestormwatertreatmentunitshallbeaninlineunitcapableofconveyingl00%ofthedesignpeak
flow. If peak flow rates exceed maximum hydraulic rate, the unit shall be installed offline.
. The Barracuda Max unit shall be designed to remove at least 80oa of the suspended solids on an annual
aggregate removal basis. Said removal shall be based on full-scale third party testing using OK-l10
media gradation or equivalent and 300 mg/t influent concentration, Said full scale testing shall have
included sediment capture based on actual total mass collected by the stormwater treatment unit.
-oR-
The Barracuda Max unit shall be designed to remove at least 50% of TSS using a media mix with dro=75 micron
and 200 mg/t influent concentration.
- oR-
The Barracuda Max unit shall be designed to remove at least 50% of TSS per current NJDEP/NJCAT
HDS protocol.
' The stormwater treatment unit internals shall consist of (1) separator cone assembly, and (1) sump assembly,
which includes the "teeth".
, 53 36" (900 mm)
54 48'(1200 mm)
s6 72" (1800 mm)
s8 96" (2400 mm)
* Peak bypass tlows are dependent on final design
0.8s cFs (24.1Llsl 0.86 cFs (24.1 L/s)
1.s2 cFs (43.0 L/s) 1.s2 cFs (43.0 L/s)
3.40 cFs (96.3 L/s) 3.42 cFs (96.s L/s)
6.08 cFs (172.2 L/s) 6.08 CFS (172.2 L/s)
Installation
Installation of the stormwater treatment unit(s) shall be performed per manufacturer's
installation instructions. Such instructions can be obtained by calling Advanced
Drainage Systems at 800-821-6710 or by logging on to www.adspipe.com.
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adspipe.rom
800-821-6710
Barracuda Max
Model
Manhcle
Diameter
NJDEP
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{80oro rsmoval}
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Maintenance Guide
July 2017BaySaver BarracudarM
One of the advantages of the BaySaver Barracuda is the ease of maintenance. Like any system that collects
pollutants, the BaySaver Barracuda must be maintained for continued effectiveness. Maintenance is a simple
procedure performed using a vacuum truck or similar equipment. The systems were designed to minimize the
volume of water removed during routine maintenance, reducing disposal costs.
Contractors can access the pollutants stored in the manhole through the manhole cover. This allows them to gain
vacuum hose access to the bottom of the manhole to remove sediment and trash. There is no conlined space
entry necessary for inspection or maintenance.
The entire maintenance procedure typically takes from 2 to 4 hours, depending on the size of the system, the
captured material, and the capacity of the vacuum truck.
Local regulations may apply to the maintenance procedure. Safe and legal dlsposal of pollutants is the
responsibility of the maintenance contractor. Maintenance should be performed only by a qualified contractor.
lnspection and Gleaning Gycle
Periodic inspection is needed to determine the need for and frequency of maintenance. You should begin
inspecting as soon as construction is complete and thereafter on an annual basis. Typically, the system needs to
be cleaned every 1-3 years.
Excessive oils, fuels or sediments may reduce the maintenance cycle. Periodic inspection is important.
Determining When to Glean
To determine the sediment depth, the maintenance contractor should lower a stadia rod into the manhole until it
contacts the top of the captured sediment and mark that spot on the rod. Then push the probe through to the
bottom of the sump and mark thal spot to determine sediment depth.
Maintenance should occur when the sediment has reached the levels indicated in the Storage Capacity Chart.
BaySaver Barracuda Storage Gapacities
Model Manhole Diameter Tr€atmont Chamber
Capacity
Standard Sediment
Capacity {20" depth}
NJDEP Sediment Capacity
(50% of standard dopth)
s3 36"212 gallons 0.44 cubic yards O.22 cubic yards
s4 48"564 gallons 0.78 cubic yards 0.39 cubic yards
S5 60'881 gallone 1.21 cubic yards 0.61 cubic yards
S6 72"1289 gallons 1.75 cubic yards 0.88 cubic yards
S8 96"3835 gallons 3.10 cubic yards 1.55 cubic yards
s10 120'7496 gallons 4.85 cubic yards 2.43 cubic yards
Maintenance I nstructions
1. Repove the manhole cover to provide access to the pollutant storage. Pollutants are stored in the sump,
below the bowl assembly visible from the surface. You'll access this area through the 10" diameter
access cylinder.
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2.
3.
4.
5.
6.
Use a vacuum truck or other similsr equipment to remove
all water, debris, oils and sediment. See figure 1.
Use a high pressure hose to clean the manhole of all the
remaining sediment and debris, Then, use the vacuum
truck to remove the water.
Fill the cleaned manhole with water until the level reaches
the invert of the outlet pipe.
Replace the manhole cover.
Dispose of the polluted water, oils, sediment and trash at
an approved facility.
Local regulations prohibit the discharge of solid material
into the sanitary system. Check with the local sewer
authority for authority to discharge the liquid.
Some localities treat the pollutants as leachate. Check with
local regulators about disposal requirements,
Additional local regulations may apply to the maintenance
procedure.
Figure I
vAc TRUCK
HOSE
SUMP
SEDIMENT
BOWL
CYLINDER
ACCESS
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2 4640TRUEMANBLVD. H|LL|ARD,OH43026 (800)821-6710 www.ads4ipe.com
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