HomeMy WebLinkAboutKING SOOPERS #146 MIDTOWN GARDENS MARKETPLACE - PDP200012 - - DRAINAGE REPORTPREPARED FOR:
Dillon Companies/King Soopers, Inc.
55 Tejon Street
Denver, Colorado 80223
Phone: (303) 778-3053
PREPARED BY:
Galloway & Company, Inc.
6162 S. Willow Drive, Suite 320
Greenwood Village, CO 80111
DATE:
July 28, 2020
REVISED:
October 7, 2020
MIDTOWN GARDENS MARKETPLACE
KING SOOPERS STORE #146
Fort Collins, Colorado
PRELIMINARY DRAINAGE REPORT
FC Water Utilities Comments
Matt Simpson
10/29/2020
masimpson@fcgov.com
Galloway Comment Responses
Galloway & Company, Inc.Page 2 of 20
6162 S. Willow Drive, Suite 320
Greenwood Village, CO 80111
303.770.8884 •GallowayUS.com
Galloway & Company, Inc.Page 3 of 20
6162 S. Willow Drive, Suite 320
Greenwood Village, CO 80111
303.770.8884 •GallowayUS.com
PRELIMINARY DRAINAGE REPORT
Midtown Gardens Marketplace
King Soopers Store #146
Legal Description
Lots 1,2, and 4 of K-Mart Plaza, and all of Lot 2 of the extension of K-Mart Plaza, situated in the
Southeast 1/4 of Section 23, Township 7 North, Range 69 West, of the 6th Principle Meridian, City
of Fort Collins, County of Larimar, State of Colorado.
Preparation Date
July 28, 2020
Revised Date
October 7, 2020
Prepared for
Dillon Companies/King Soopers, Inc.
55 Tejon Street
Denver, Colorado 80223
Phone: (303) 778-3053Client
Address
City, State, Zip
Prepared by:Reviewed by:
________________________________________ ____________________________
Name Name
Galloway & Company, Inc.Page 4 of 20
6162 S. Willow Drive, Suite 320
Greenwood Village, CO 80111
303.770.8884 •GallowayUS.com
Midtown Gardens Marketplace
10/7/2020
Galloway & Company, Inc.Page 5 of 20
ENGINEER’S STATEMENT
I hereby attest that this report and plan for the preliminary drainage design for Midtown Gardens
Marketplace was prepared by me or under my direct supervision, in accordance with the provisions of the
Fort Collins Stormwater Criteria Manual. I understand that the City of Fort Collins does not and will not
assume liability for drainage facilities designed by others.
Phil Dalrymple, PE # 41171 Date
For and on behalf of Galloway & Company, Inc.
DEVELOPER’S CERTIFICATION
“King Soopers, Inc. hereby certifies that the drainage facilities for Midtown Gardens Marketplace shall be
constructed according to the design presented in this report. I understand that the City of Fort Collins
does not and will not assume liability for the drainage facilities designed and/or certified by my engineer
and that the City of Fort Collins review))s drainage plans pursuant to the Municipal Code; but cannot, on
behalf of Midtown Gardens Marketplace, guarantee that final drainage design review will absolve King
Soopers, Inc. and/or their successors and/or assigns of future liability for improper design.”
Authorized Signature Date
King Soopers, Inc.
Midtown Gardens Marketplace
10/7/2020
Galloway & Company, Inc.Page 6 of 20
I. General Location and Existing Information ............................................................................................ 7
Location ...................................................................................................................................... 7
Description of Property ................................................................................................................ 7
II. Master Drainage Basin Description ...................................................................................................... 7
Major Basin Description .............................................................................................................. 7
Sub- Basin Description ................................................................................................................ 8
III. Floodplain Information ........................................................................................................................ 8
IV. Project Description ............................................................................................................................. 8
V. Drainage Design Criteria ..................................................................................................................... 8
Regulations ................................................................................................................................. 8
The Four Step Process (Low Impact Development) ..................................................................... 9
Development Criteria Reference and Constraints ........................................................................ 9
Hydrologic Criteria .................................................................................................................... 10
Hydraulic Criteria ...................................................................................................................... 10
VI. Proposed Drainage Facilities ............................................................................................................ 11
General Concept ....................................................................................................................... 11
Specific Details ......................................................................................................................... 11
VII. Variance Requests .......................................................................................................................... 13
VIII. Erosion Control .............................................................................................................................. 13
Construction Material & Equipment ........................................................................................... 14
Maintenance ............................................................................................................................. 14
IX. Conclusions ..................................................................................................................................... 14
Compliance with Standards ....................................................................................................... 14
Variances .................................................................................................................................. 14
Drainage Concept ..................................................................................................................... 14
VI. References....................................................................................................................................... 15
VII. Appendices ..................................................................................................................................... 16
A.Exhibits & Figures ........................................................................................................... 16
B.Hydrologic Computations ................................................................................................ 16
C.Hydraulic Computations .................................................................................................. 16
D.Drainage Maps ............................................................................................................... 16
TABLE OF CONTENTS
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I. General Location and Existing Information
Location
Midtown Gardens Marketplace (hereafter referred to as “the site” or “project site”) will be located at
the northwest corner of South College Avenue and West Drake Road. It is bounded on north by an
existing commercial development; on the south by West Drake Road (including a Jiffy Lube and Loaf
‘N Jug to remain); on the east by College Avenue; and on the west by the MAX-BRT Bus Line.
Spring Creek is located north of the site. More specifically, the site is located in the Southeast Quarter
of Section 23, Township 7 North, Range 69 West in the City of Fort Collins, County of Larimer and
State of Colorado. Refer to Appendix A for a Vicinity Map.
Description of Property
The project site is approximately 11.34 acres, and consists of a currently vacant Kmart store, a small
retail building at the northeast corner of the site, and an existing Loaf N’ Jug fueling station. Existing
grades on the site range from one to four percent, with historic runoff generally draining to the north
and east across the site. There are no major drainage ways passing through the project site.
According to the USDA NRCS Web Soil Survey, ‘Nunn Clay loam, 0 to 1 percent slopes’ covers the
entire project site. This soil is associated with Hydrologic Soil Group (HSG) ‘C’. HSG ‘C’ soils have a
slow infiltration rate when thoroughly wet and consist chiefly of soils having a layer that impedes the
downward movement of water or soils of moderately fine texture or fine texture. These soils have a
slow rate of water transmission. Refer to Appendix A for additional soils information.
The Midtown Gardens Marketplace will be developed in one phase and is approximately 11.34 acres.
The existing vacant Kmart building along with the vacant retail building at the northeast corner of the
site will be removed. A new King Soopers Marketplace will replace the Kmart, while a new King
Soopers fueling station will replace the vacant retail building. The existing parking lot will be
reconstructed to accommodate the new structures. The lot containing the Loaf N’ Jug will remain
vacant for future development but is included in this report in its developed condition.
During the water quality storm event, surface runoff will flow into one of several stormwater quality
features located on the site. The stormwater quality features include the use of an underground
storage system. During the minor (i.e., 2-year) and major (i.e., 100-year) storm events, runoff volume
in excess of the water quality event will bypass the WQ system and enter the existing storm sewer
system.
II. Master Drainage Basin Description
Major Basin Description
The project site is located in the Spring Creek drainage basin. According to the City of Fort Collins
website (http://www.fcgov.com/utilities/what-we-do/stormwater/drainage-basins/spring-creek-basin),
this basin “is a major watercourse that flow from Spring Canyon Dam at Horsetooth Reservoir to its
confluence with the Poudre River. The basin is dominated by residential development, but also
includes open space, parks, and isolated areas of commercial and industrial development.”
On-site detention storage is not required for the site because the site is mostly impervious and the
proposed development does not trigger detention requirements. While detention is not required, the
applicant has coordinated with the City to provide 100-year detention for the proposed development
and small retail on SE corner
of site (Lark Burger building)
please update
based on design
with detention.
Corrected as noted
Corrected as
noted
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Galloway & Company, Inc.Page 8 of 20
to alleviate the impact to the downstream system. The Impervious Area Exhibit in Appendix D, which
shows a net decrease in total impervious area form the existing to proposed condition. Water quality
for the site has been provided in accordance with the City of Fort Collins LID requirements for the
redeveloped portions of the site. A Water Quality and detention structure has been sized for the
redeveloped portions of the site in the form of an underground extended detention basin, herein
referred to as Pond A. Preliminary calculations for underground basin have been provided, and can
be found in Appendix C.
Sub- Basin Description
The site historically drains north and east towards the adjacent commercial development and College
Avenue. There are several storm inlets along the northern property line and throughout the site which
collect runoff. These storm sewer mains ultimately drain to Spring Creek. At the request of Fort
Collins Stormwater Master Planning, The historic drainage pattern will be modified to convey flows
from the site to the existing storm drain system at the southeast corner of the site in College Ave and
flowing east along Princeton Road, rather than to the existing storm drain system on the adjacent
property to the north. Minor flows will be conveyed off-site at the site boundaries, which is consistent
with the historic drainage pattern.
At the sub-basin level, no offsite runoff is anticipated to enter the site, with the exception of a small
amount of runoff at the southwest corner or the site coming from the MAX/BRT bus station, which is
currently tributary to the site. A portion of the site along W Drake Rd. and S College Ave. will drain
offsite, which is consistent with the current drainage pattern. The site has been broken into four
basins, each with their own set of sub-basins. A description of each basin and their characteristics
can be found later in the report.
There are no irrigation, reservoir, or other facilities that influence, or are influenced by, the local
drainage.
III. Floodplain Information
The project site is shown on FEMA Map Number 08069C0987G (refer to Appendix A for FEMA
Firmette). This map shows that the project is not impacted by an existing floodplain/floodway. Refer to
Appendix A for a copy of the Firmette.
IV. Project Description
The Midtown Gardens Marketplace will be developed in one phase and is approximately 11.34 acres.
The existing vacant Kmart building along with the vacant retail building at the northeast corner of the
site will be removed. A new King Soopers Marketplace will replace the Kmart, while a new King
Soopers fueling station will replace the vacant retail building. The existing parking lot will be
reconstructed to accommodate the new structures. The lot containing the Loaf N’ Jug will remain
vacant for future development but is included in this report in its developed condition.
V. Drainage Design Criteria
Regulations
This preliminary drainage design presented herein is prepared in accordance with the Fort Collins
Stormwater Criteria Manual, November 2017 (FCSCM), the Mile High Flood District (MHFD) Urban
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Galloway & Company, Inc.Page 9 of 20
Storm Drainage Criteria Manual, January 2016 (USDCM), and Chapter 10, Flood Prevention and
Protection, of the Fort Collins City Code. No other drainage reports could be provided for the site by
the City of Fort Collins.
The Four Step Process (Low Impact Development)
At this preliminary stage of the design process, we developed a commensurate implementation of the
‘The Four-Step Process’ for stormwater quality management. Ordinance No. 007, 2016 requires that
no less than seventy-five percent (75%) of any newly developed or redeveloped area be treated using
one or a combination of LID techniques. As previously mentioned, the developer proposes to replace
the existing Kmart with a new King Soopers Marketplace. The runoff for the modified areas collected
onsite will be treated using and underground LID water quality system. This LID system will address
100% of the captured volume rather than using a combination of LID and standard methods.
Appropriate spill containment will be provided in the area of the proposed fuel station.
Step 1 - Employ runoff reduction practices
The attached drainage map (see Appendix D) delineates the proposed drainage basins, each of
which drains to a proposed underground water quality system, Pond A. Underground systems are an
accepted LID method when surface BMPs are infeasible, which consist of an underground chamber
that provide stormwater quality treatment via sedimentation, screening, filtration, and other physical
and chemical processes.
Step 2 - Implement BMPs that provide a Water Quality Capture Volume (WQCV)
Due to site constraints, and underground storage system will provide the necessary Water Quality
Capture Volume (WQCV).
Step 3 - Stabilize drainageways
The developed runoff generated by the proposed redevelopment will drain to an existing storm drain
system located along the west side of South College Avenue. This system drains north and outfalls
into Spring Creek. Our work assumes that an appropriate level of stabilization exists at the outfall into
Spring Creek.
Step 4 - Implement site specific and other source control BMPs
Site specific considerations such as material handling/storage and other site operations will be
addressed in the Stormwater Management Plan (SWMP).
Development Criteria Reference and Constraints
This preliminary drainage design presented herein is prepared in accordance with the Fort Collins
Stormwater Criteria Manual, November 2017 (FCSCM) and the Mile High Flood District (MHFD)
Urban Storm Drainage Criteria Manual, January 2016 (USDCM). No other drainage reports could be
provided for the site by the City of Fort Collins.
Existing runoff for the proposed site generally drains to the north and east across the site. The
majority of the on-site runoff is captured by an existing storm sewer system which has three
connections to the offsite system downstream. The site drains into an existing 24” storm pipe just
north of the site (2 connections), and a 15” storm pipe along College Avenue. Capacity calculations
for the proposed and existing portions of the storm sewer system have been provided in Appendix C.
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Galloway & Company, Inc.Page 10 of 20
Hydrologic Criteria
For urban catchments that are not complex and are generally 160 acres or less in size, it is
acceptable that the design storm runoff be analyzed using the Rational Method. The Rational Method
is often used when only the peak flow rate or total volume of runoff is needed (e.g., storm sewer
sizing or simple detention basin sizing). The Rational Method was used to estimate the peak flow at
each design point. Routing calculations (i.e., time attenuation) that aggregate the basins draining to a
specific design point are include in the Rational Method calculations in Appendix B.
The Rational Method is based on the Rational Formula:
Q = CiA
Where:
Q = the maximum rate of runoff, cfs
C = a runoff coefficient that is the ratio between the runoff volume from an area and the average
rate of rainfall depth over a given duration for that area
i = average intensity of rainfall in inches per hour for a duration equal to the Time of
Concentration (Tc)
A = area, acres
Runoff Coefficients were determined based on Tables 3.2-1, 3.2-2, and 3.2-3 of the the FCSCM. The
one-hour rainfall Intensity-Duration-Frequency tables for use with the Rational Method of runoff
analysis are provided in Table 3.4-1 of the FCSCM.
The 2-year and 100-year storm events serve as the basis for the drainage system design. The 2-year
storm is considered the minor storm event. It has a fifty percent probability of exceedance during any
given year. The 100-year storm is considered the major storm event. It has a one percent probability
of exceedance during any given year.
The 2-year drainage system, at a minimum, must be designed to transport runoff from the 2-year
recurrence interval storm event with minimal disruption to the urban environment. The 100-year
drainage system, as a minimum, must be designed to convey runoff from the 100-year recurrence
interval flood to minimize life hazards and health, damage to structures, and interruption to traffic and
services.
Hydraulic Criteria
There are three on-site basins which drain to the proposed storm sewer system, which are identified
in the proposed drainage map (Appendix D) as Basins A, B, and C. Runoff from each basin will be
collected by storm sewer inlets and pipes and conveyed offsite to the existing storm drain system in
College Ave at the southeast corner of the site. Basin A is collected by a storm sewer system on the
west, south, and east sides of the proposed building. Basins B & C are collected by storm sewers on
the east side of the building. Each of these three systems convey flows to a proposed underground
detention system at the southeast corner of the site for water quality, detention, and attenuation,
which then releases the detained flows into the existing storm drain system in College Ave.
Additional areas for the site not collected by the proposed storm drain system are designated as Off-
Site Basins (OS) and will drain offsite to existing storm drain infrastructure, consistent with the
existing drainage pattern. Runoff from these offsite basins will be released undetained toward W
Drake Rd, S College Ave, and existing inlets north of the site.
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Inlet Capacity Analysis
Inlet calculations are not required to be included with this preliminary report and will provided with the
Final Drainage Report.
Storm Drain Capacity Analysis
The preliminary storm drain system is typically sized to convey the sum of the 100-year developed
runoff at each design point draining into the system. The pipes are sized to convey this runoff without
surcharging (full-flow capacity). This method should provide a conservative estimate of total runoff
and pipe sizes. It appears that the 100-year developed runoff for the site will not be able to be
conveyed in the existing storm sewer system at the north end of the site, per the existing drainage
pattern. Therefore, the City has granted that the proposed storm sewer system can be re-routed
such that it will be detained and treated for water quality on site, then released at a controlled 2-year
historic rate into the existing storm drain system in College Ave at the southeast corner of the site.
The preliminary design of the storm sewer system for the site has been sized to handle the 100-year
storm event. For this preliminary Drainage Study, Flowmaster was used to size the proposed
system, and provide capacity calculations, using a minimum slope of 0.5%. The Flowmaster
summaries in Appendix C show the max flows for the proposed storm drains at the minimum slope.
VI. Proposed Drainage Facilities
General Concept
This final design presents the detailed design of the proposed system for collecting and conveying
developed runoff from current and proposed development at the Midtown Gardens Marketplace site
to the Stormwater quality and detention features and offsite systems. The existing site runoff drains to
existing storm sewer inlets within the parking lot. The proposed design matches this existing
drainage pattern and includes the implementation of and underground StormTech system to provide
water quality and detention for the site.
Specific Details
The site has been broken into three basins, each with their own set of sub-basins. A description of
each basin and their characteristics can be found below. The intent of the drainage design is to have
the runoff from the majority of the site collected and drain through a water quality and detention
facility prior to entering the existing storm sewer system offsite. Pond A has been sized based on the
City of Fort Collins LID requirements for the necessary portions of the site, which will be located at the
downstream connection point to the existing storm drain system at the southeast corner of the site in
College Ave. The released stormwater from the site will travel in the existing storm sewer system,
and ultimately reach Spring Creek.
Basin A
Basin A consists of the west, south, and southeast portions of the site and is comprised of 13 sub-
basins. The basin includes the proposed building, the south and southeast parking lots, the areas to
the west of the proposed building, and the existing Loaf N’ Jug site (which will remain vacant as part
of this project but is included in the drainage calculations in its future developed condition). Runoff
from Basin A will be collected by the proposed storm sewer system and conveyed to the southeast
corner of the site to the proposed underground detention facility, and ultimately discharge into the
existing storm sewer system in College Ave.
Basin B
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Basin B consists of the northeastern portion of the site between the building and the fuel center and is
comprised of 3 sub-basins. The basin includes the portion of the east parking lot at the building entry
and the access drive to College Ave. Runoff from Basin B will be collected by the proposed storm
sewer system and conveyed south to the southeast corner of the site to the proposed underground
detention facility, and ultimately discharge into the existing storm sewer system in College Ave.
Basin C
Basin C consists of the northeast corner of the site and is comprised of 5 sub-basins. The basin
includes the proposed fuel center and the northeast portion of the main parking lot. Runoff from
Basin B will be collected by the proposed storm sewer system and conveyed south to the southeast
corner of the site to the proposed underground detention facility, and ultimately discharge into the
existing storm sewer system in College Ave.
Offsite Basins
The remainder of the site consists of basins that flow offsite, as is current with the existing drainage
pattern. These basins are located along W Drake Rd, S College Ave, and the northern portion of the
site between the building and the adjacent property. These basins include sidewalk, tree lawn, and
landscape areas between the sidewalk and the parking lot, and access drives off of S College Ave
and W Drake Rd, as well as paved areas joining the site with the adjacent property. Flows from these
areas historically sheet flow to either the existing roadways adjacent to the site or to existing inlets on
the adjacent property north of the site, and ultimately drain to an existing inlet located in College
Avenue near the northeast corner of the site and an existing inlet at the northwest corner of College
and Drake. The characteristics of the tributary areas draining to these inlets will remain virtually the
same, so anticipated flow rates generated should be the same and not negatively impact the existing
storm sewer system. Once in the existing storm sewer inlets, the stormwater from this basin is
conveyed through the existing storm sewer system and ultimately reaches Spring Creek.
Water Quality Enhancement
The site has been divided into multiple drainage basins as described above. Runoff from each basin
will be collected and conveyed to Pond A, which provides water quality treatment in the form of and
underground LID system. The LID Summary Table provided in Appendix B identifies and compares
the on-site impervious area of the existing and proposed conditions.
In the existing condition, there is approximately 10.59 acres of impervious area within the limits of
disturbance. Of that area, 8.69 acres of impervious area flow to the on-site storm drain system. The
remaining 1.91 acres flow offsite and does not contribute to the on-site storm system. In the
proposed condition, there is approximately 10.54 acres or impervious area within the limits of
disturbance. Of that area, 9.74 acres of impervious area flow to the on-site storm drain system. The
remaining 0.80 acres flow offsite and does not contribute to the on-site storm system. Therefore, the
proposed site will increase the total amount of treated impervious area while reducing the overall
impervious area. In conformance with the requirement identified under the Four Step Process to treat
at least 75% of impervious areas through LID methods, 100% of the on-site proposed impervious
areas will be treated through the proposed underground detention system. A summary of the
Impervious areas can be found in Appendix B, and a delineation of the on-site area boundaries for
the existing and proposed conditions can be found in the Impervious Area Exhibit in Appendix D.
More information for the calculation and sizing of the water quality system is provide in Appendix B.
I think 10.54 acres of Imp. Area is your required treatment area.
How much of this 10.54 is on-property? Off-property areas do not
count into WQ/LID for a redeveloping site.
Please discuss with me if this does not make sense.
This sounds like you are short 0.8 acres of treated
impervious area. (10.54 - 9.74 = 0.80)
I am unclear if the project is providing the required water quality treatment area.
Please move the WQ and LID table to the report body here. I have made more
comments on this table in the appendix.
Onsite impervious areas (new or modified) require WQ
treatment. It doesn't matter where they flow to.
This paragraph
has been updated
to address these
based on discus-
sions with Matt
Simpson
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Water Quality treatment will be provided in the isolator rows of the StormTech detention system. The
total volume of water quality has been calculated based on a release rate of 0.35 gpm/sf of storage
area. Structures within the StormTech system will divert flows in excess of the water quality event to
the remainder of the detention system. A summary of the water quality system calculations can be
found in Appendix B.
Storm Water Detention
The City has requested that the underground systems mentioned above be utilized to provide
additional detention storage to alleviate flooding issues downstream of the site. The proposed
underground StormTech system, Pond A, will be designed as an Extended Detention Basin for the
site, including Water Quality treatment and 100-year detention with a controlled 2-year historic
release rate of 0.50 cfs/acre. Required volumes were determined using the Modified FAA Method.
Below is a summary of the total storage proposed for each system. A tabulation of the stage storage
volume for Pond A can be found in Appendix C.
StormTech Detention Facility Summary
Facility I.D.
WQCV
Provided
(cf)
Additional
Storage Volume
Provided
(cf)
Total Volume
Required
(cf)
Total Volume
Provided
(cf)
Pond A 14,796 72,581 86,940 87,377
VII. Variance Requests
No variances are being requested with the proposed improvements described herein.
VIII. Erosion Control
A General Permit for Stormwater Discharge Associated with Construction Activities issued by the
Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division
(WQCD), will be acquired for the site. A Stormwater Management Plan (SWMP) should be prepared
to identity the Best Management Practices (BMPs) which, when implemented, will meet the
requirements of said General Permit. Below is a summary of SWMP requirements which may be
implemented on-site.
The following temporary BMPs may be installed and maintained to control on-site erosion and
prevent sediment from traveling off-site during construction:
· Silt Fence – a woven synthetic fabric that filters runoff. The silt fence is a temporary barrier that is
placed at the base of a disturbed area.
· Vehicle Tracking Control – a stabilized stone pad located at points of ingress and egress on a
construction site. The stone pad is designed to reduce the amount of mud transported onto public
roads by construction traffic.
· Straw Wattles – wattles act as a sediment filter. They are a temporary BMP and require proper
installation and maintenance to ensure their performance.
· Inlet protection – Inlet protection will be used on all existing and proposed storm inlets to help
prevent debris from entering the storm sewer system. Inlet protection generally consists of straw
wattles or block and gravel filters.
Add
-tributary area
-imperviousness
-release rate
updated table
as requested
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Compliance with Erosion Control Criteria and all Erosion Control Materials in greater detail will be
provided with the Final Drainage Report
Construction Material & Equipment
The contractor shall store all construction materials and equipment and shall provide maintenance
and fueling of equipment in confined areas on-site from which runoff will be contained and filtered.
Maintenance
The temporary BMPs will be inspected by the contractor at a minimum of once every two weeks and
after each significant storm event. The property owner will be responsible for routine and non-routine
maintenance of the temporary BMPs. Routine maintenance includes:
· Remove sediment from the bottom of the temporary sediment basin when accumulated sediment
occupies about 20% of the design volume or when sediment accumulation results in poor
drainage.
· Debris and litter removal-remove debris and litter to minimize outlet clogging and improve
aesthetics as necessary.
· Inspection of the facility-inspect the facility annually to ensure that it functions as initially intended.
· Cleaning and repair of BMP’s is required when sediment has built up or the BMP is not working
properly.
IX. Conclusions
Compliance with Standards
The design presented in this final drainage report for the Midtown Gardens Marketplace has been
prepared in accordance with the design standards and guidelines presented in the Fort Collins
Stormwater Criteria Manual and the MHFD Urban Storm Drainage Criteria Manual.
Variances
No variances are being requested with the proposed improvements described herein.
Drainage Concept
The proposed Midtown Gardens Marketplace storm drainage improvements should provide adequate
collection and Water Quality protection for the developed site. The proposed drainage design will
sufficiently drain the proposed development and should not negatively impact the existing condition of
the overall storm drainage system.
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VI. References
1. Fort Collins Stormwater Criteria Manual, November 2017
2. Urban Storm Drainage Criteria Manual, Mile High Flood District, January 2016 (with current
revisions).
3. Flood Insurance Rate Map – Larimer County, Colorado and Incorporated Areas Community
Panel No. 08069C0987G, Effective May 2, 2012.
4. Soil Map – Larimer County Area, Colorado as available through the Natural Resources
Conservation Service National Cooperative Soil Survey web site via Web Soil Survey 2.0.
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VII. Appendices
A. Exhibits & Figures
· Vicinity Map
· USGS Soil Survey Data
· FEMA Flood Insurance Rate Map
B. Hydrologic Computations
· Existing Condition Basin Summary
· Existing Condition Rational Method Computations
· Existing Minor and Major Storm Runoff Computations
· Proposed Condition Basin Summary
· Proposed Condition Rational Method Computations
· Proposed Minor and Major Storm Runoff Computations
· Modified FAA Calculations - Water Quality
· Modified FAA Calculations – 100-Year Storage
· Water Quality System Calculation Summary
· LID Summary Table
C. Hydraulic Computations
· Flowmaster Pipe Capacity Calculations
· ADS StormTech Specifications
· ADS StormTech Stage Storage Summary
D. Drainage Maps
· Impervious Area Exhibit
· Existing Drainage Map
· Proposed Drainage Map
Subdivision:Midtown Gardens Marketplace Project Name:King Soopers Store #146
Location:CO, Fort Collins Project No.:
Calculated By:E. Mowinckel
Checked By:P. Dalrymple
Date:10/5/20
1
BASIN D.A.Hydrologic C2 C5 C100 L S Ti | 2-Year Ti | 100-Year L S Cv VEL.Tt COMP. Tc | 2-Year COMP. Tc | 100-Year TOTAL Urbanized Tc Tc | 2-Year Tc | 100-Year
ID (AC)Soils Group Cf=1.00 Cf=1.00 Cf=1.25 (FT)(%)(MIN)(MIN)(FT)(%)(FPS)(MIN)(MIN)(MIN)LENGTH(FT)(MIN)(MIN)(MIN)
EX01 1.11 C 0.92 0.92 1.00 239 1.87 4.2 2.3 0 1.00 20 2.0 0.0 4.2 2.3 239 11.3 5.0 5.0
EX02 0.14 C 0.92 0.92 1.00 85 2.60 2.3 1.3 0 1.00 20 2.0 0.0 2.3 1.3 85 10.5 5.0 5.0
EX03 1.02 C 1.03 1.03 1.00 390 1.60 2.2 3.2 0 1.00 20 2.0 0.0 2.2 3.2 390 12.2 5.0 5.0
EX04 0.33 C 0.95 0.95 1.00 190 1.61 3.3 2.2 0 1.00 20 2.0 0.0 3.3 2.2 190 11.1 5.0 5.0
EX05 0.53 C 0.95 0.95 1.00 350 1.91 4.4 2.8 0 1.00 20 2.0 0.0 4.4 2.8 350 11.9 5.0 5.0
EX06 1.22 C 0.85 0.85 1.00 340 1.00 8.5 3.4 75 0.64 20 1.6 0.8 9.3 4.2 415 12.3 9.3 5.0
EX07 2.44 C 0.92 0.92 1.00 355 1.30 5.7 3.2 285 0.41 20 1.3 3.7 9.4 6.9 640 13.6 9.4 6.9
EX08 0.44 C 0.89 0.89 1.00 140 2.39 3.5 1.7 0 1.00 20 2.0 0.0 3.5 1.7 140 10.8 5.0 5.0
EX09 0.61 C 0.72 0.72 0.90 200 1.00 10.0 5.3 0 1.00 20 2.0 0.0 10.0 5.3 200 11.1 10.0 5.3
EX10 0.34 C 0.71 0.71 0.89 90 2.62 5.0 2.7 0 1.00 20 2.0 0.0 5.0 2.7 90 10.5 5.0 5.0
EX11 0.61 C 0.83 0.83 1.00 250 2.54 5.9 2.2 0 1.00 20 2.0 0.0 5.9 2.2 250 11.4 5.9 5.0
EX12 1.05 C 0.91 0.91 1.00 160 3.08 3.0 1.6 0 1.00 20 2.0 0.0 3.0 1.6 160 10.9 5.0 5.0
EX13 0.25 C 0.95 0.95 1.00 150 2.00 2.7 1.8 0 1.00 20 2.0 0.0 2.7 1.8 150 10.8 5.0 5.0
EX14 0.11 C 0.95 0.95 1.00 100 2.00 2.2 1.5 0 1.00 20 2.0 0.0 2.2 1.5 100 10.6 5.0 5.0
EX15 0.12 C 0.95 0.95 1.00 105 2.00 2.3 1.5 0 1.00 20 2.0 0.0 2.3 1.5 105 10.6 5.0 5.0
EX16 0.59 C 0.95 0.95 1.00 240 2.00 3.4 2.3 0 1.00 20 2.0 0.0 3.4 2.3 240 11.3 5.0 5.0
EX17 0.48 C 0.95 0.95 1.00 230 2.00 3.4 2.3 0 1.00 20 2.0 0.0 3.4 2.3 230 11.3 5.0 5.0
EX18 0.53 C 0.95 0.95 1.00 235 2.00 3.4 2.3 0 1.00 20 2.0 0.0 3.4 2.3 235 11.3 5.0 5.0
EX19 0.33 C 0.95 0.95 1.00 220 2.00 3.3 2.2 0 1.00 20 2.0 0.0 3.3 2.2 220 11.2 5.0 5.0
EX20 0.15 C 0.82 0.82 1.00 460 1.17 10.7 3.8 0 1.00 20 2.0 0.0 10.7 3.8 460 12.6 10.7 5.0
EX21 0.23 C 0.83 0.83 1.00 125 0.80 6.1 2.3 0 1.00 20 2.0 0.0 6.1 2.3 125 10.7 6.1 5.0
NOTES:
Ti = (1.87*(1.1 - CCf)*(L)^0.5)/((S)^0.33), S in %Cv
Tt=L/60V (Velocity From Fig. 501)2.5
Velocity V=Cv*S^0.5, S in ft/ft 5
Tc Check = 10+L/180 7
For Urbanized basins a minimum Tc of 5.0 minutes is required.10
For non-urbanized basins a minimum Tc of 10.0 minutes is required 15
20
STANDARD FORM SF-2
TIME OF CONCENTRATION - EXISTING
SUB-BASIN Tc CHECK
KSS000018.02
DATA (URBANIZED BASINS)(Tt)FINALINITIAL/OVERLAND
(Ti)
TRAVEL TIME
Paved areas and shallow paved swales
Type of Land Surface
Heavy Meadow
Tillage/field
Short pasture and lawns
Nearly bare ground
Grassed waterway
H:\King Soopers - City Market\CO, Fort Collins - KSS000146 -#18 College Drake\3.04 Grading-Drainage Studies\3.04.2 Proposed Drainage Reports-Info\Hydrology\KSS 146_Rational_Routing - Ex.xls Page 1 of 1 10/5/2020
You need to use the Fort Collins Stormwater Criteria Manual (FCSCM) method
for the Tc calcs. This is the "manning velocity method", for this method, you will
need to simple assume a flow depth to compete the Tc calculation.
Please see chapter 5, section 3.3 of the FCSCM.
Feel free to contact me if you have questions.
V=1.4/n * R^2/3 * S^1/2
Tc Calc has been up-
dated
Subdivision:Midtown Gardens Marketplace Project Name:King Soopers Store #146
Location:CO, Fort Collins Project No.:
Calculated By:E. Mowinckel
Checked By:P. Dalrymple
Date:10/5/20
1
BASIN D.A.Hydrologic C2 C5 C100 L S Ti | 2-Year Ti | 100-Year L S Cv VEL.Tt COMP. Tc | 2-Year COMP. Tc | 100-Year TOTAL Urbanized Tc Tc | 2-Year Tc | 100-Year
ID (AC)Soils Group Cf=1.00 Cf=1.00 Cf=1.25 (FT)(%)(MIN)(MIN)(FT)(%)(FPS)(MIN)(MIN)(MIN)LENGTH(FT)(MIN)(MIN)(MIN)
A-1 0.83 C 0.92 0.92 1.00 250 1.75 4.5 2.5 100 2.00 20 2.8 0.6 5.1 3.0 350 11.9 5.1 5.0
A-2 0.50 C 0.91 0.91 1.00 200 3.00 3.5 1.8 0 1.00 20 2.0 0.0 3.5 1.8 200 11.1 5.0 5.0
A-3 0.90 C 0.82 0.82 1.00 175 1.75 5.7 2.1 0 1.00 20 2.0 0.0 5.7 2.1 175 11.0 5.7 5.0
A-4 0.23 C 0.87 0.87 1.00 125 1.50 4.2 1.8 0 1.00 20 2.0 0.0 4.2 1.8 125 10.7 5.0 5.0
A-5 1.21 C 0.89 0.89 1.00 200 2.00 4.4 2.1 0 1.00 20 2.0 0.0 4.4 2.1 200 11.1 5.0 5.0
A-6 1.08 C 0.85 0.85 1.00 280 1.90 6.4 2.5 0 1.00 20 2.0 0.0 6.4 2.5 280 11.6 6.4 5.0
A-7 0.15 C 0.95 0.95 1.00 80 7.00 1.3 0.9 0 1.00 20 2.0 0.0 1.3 0.9 80 10.4 5.0 5.0
A-8 0.28 C 0.88 0.88 1.00 60 2.00 2.5 1.1 40 0.80 20 1.8 0.4 2.9 1.5 100 10.6 5.0 5.0
A-9 0.25 C 0.72 0.72 0.91 60 2.00 4.3 2.2 60 1.00 20 2.0 0.5 4.8 2.7 120 10.7 5.0 5.0
A-10 0.11 C 0.95 0.95 1.00 20 2.00 1.0 0.7 0 1.00 20 2.0 0.0 1.0 0.7 20 10.1 5.0 5.0
A-11 0.55 C 0.95 0.95 1.00 230 2.00 3.4 2.3 0 1.00 20 2.0 0.0 3.4 2.3 230 11.3 5.0 5.0
A-12 0.65 C 0.95 0.95 1.00 230 2.00 3.4 2.3 0 1.00 20 2.0 0.0 3.4 2.3 230 11.3 5.0 5.0
A-13 1.56 C 0.95 0.95 1.00 230 2.00 3.4 2.3 0 1.00 20 2.0 0.0 3.4 2.3 230 11.3 5.0 5.0
B-1 0.77 C 0.92 0.92 1.00 250 1.80 4.4 2.4 40 1.00 20 2.0 0.3 4.7 2.8 290 11.6 5.0 5.0
B-2 0.09 C 0.72 0.72 0.91 40 2.50 3.3 1.7 90 2.00 20 2.8 0.5 3.8 2.2 130 10.7 5.0 5.0
B-3 0.08 C 0.65 0.65 0.82 40 3.00 3.7 2.3 90 2.00 20 2.8 0.5 4.2 2.9 130 10.7 5.0 5.0
C-1 0.11 C 0.95 0.95 1.00 45 1.50 1.6 1.1 75 1.00 20 2.0 0.6 2.3 1.7 120 10.7 5.0 5.0
C-2 0.12 C 0.95 0.95 1.00 20 2.00 1.0 0.7 0 1.00 20 2.0 0.0 1.0 0.7 20 10.1 5.0 5.0
C-3 0.65 C 0.93 0.93 1.00 190 2.50 3.3 1.9 0 1.00 20 2.0 0.0 3.3 1.9 190 11.1 5.0 5.0
C-4 0.34 C 0.90 0.90 1.00 160 2.20 3.7 1.8 0 1.00 20 2.0 0.0 3.7 1.8 160 10.9 5.0 5.0
C-5 0.01 C 0.95 0.95 1.00 15 2.00 0.9 0.6 0 1.00 20 2.0 0.0 0.9 0.6 15 10.1 5.0 5.0
OS-1 0.51 C 0.54 0.54 0.68 50 1.75 6.1 4.6 600 0.20 20 0.9 11.2 17.3 15.8 650 13.6 13.6 13.6
OS-2 0.32 C 0.73 0.73 0.91 40 2.00 3.5 1.8 450 1.00 20 2.0 3.8 7.2 5.5 490 12.7 7.2 5.5
OS-3 0.13 C 0.92 0.92 1.00 85 4.00 2.0 1.1 0 1.00 20 2.0 0.0 2.0 1.1 85 10.5 5.0 5.0
OS-4 0.32 C 0.93 0.93 1.00 150 2.50 2.9 1.7 0 1.00 20 2.0 0.0 2.9 1.7 150 10.8 5.0 5.0
OS-5 0.71 C 0.87 0.87 1.00 170 2.00 4.5 1.9 0 1.00 20 2.0 0.0 4.5 1.9 170 10.9 5.0 5.0
OS-6 0.15 C 0.95 0.95 1.00 124 3.00 2.2 1.4 0 1.00 20 2.0 0.0 2.2 1.4 124 10.7 5.0 5.0
NOTES:
Ti = (1.87*(1.1 - CCf)*(L)^0.5)/((S)^0.33), S in %Cv
Tt=L/60V (Velocity From Fig. 501)2.5
Velocity V=Cv*S^0.5, S in ft/ft 5
Tc Check = 10+L/180 7
For Urbanized basins a minimum Tc of 5.0 minutes is required.10
For non-urbanized basins a minimum Tc of 10.0 minutes is required 15
20
STANDARD FORM SF-2
TIME OF CONCENTRATION - PROPOSED
Paved areas and shallow paved swales
Type of Land Surface
Heavy Meadow
Tillage/field
Short pasture and lawns
Nearly bare ground
Grassed waterway
DATA (URBANIZED BASINS)(Tt)FINALINITIAL/OVERLAND
(Ti)
TRAVEL TIMESUB-BASIN Tc CHECK
KSS000018.02
H:\King Soopers - City Market\CO, Fort Collins - KSS000146 -#18 College Drake\3.04 Grading-Drainage Studies\3.04.2 Proposed Drainage Reports-Info\Hydrology\KSS 146_Rational_Routing.xls Page 1 of 1 10/5/2020
You need to use the Fort Collins Stormwater Criteria Manual (FCSCM) method
for the Tc calcs. This is the "manning velocity method", for this method, you will
need to simple assume a flow depth to compete the Tc calculation.
Please see chapter 5, section 3.3 of the FCSCM.
Feel free to contact me if you have questions.
V=1.4/n * R^2/3 * S^1/2 Tc Calc has been up-
dated
Project Number:King Soopers Store #146 Date:10/5/2020
Project Location:CO, Fort Collins
Calculations By:E. Mowinckel
Checked By:P. Dalrymple
Pond Description:Pond A Water Quality
User Input Cell:Blue Text
1/2 2-year 5137
0.90 0.12
10.47
3.30
minutes seconds in/hr cubic feet cubic feet cubic feet acre-feet
5 300 1.43 4022 990.6 3031 0.07
10 600 1.11 6237 1981.2 4256 0.10
15 900 0.94 7917 2971.8 4945 0.11
20 1200 0.81 9088 3962.4 5125 0.12
25 1500 0.72 10090 4953 5137 0.12
30 1800 0.65 11007 5943.6 5063 0.12
35 2100 0.59 11557 6934.2 4623 0.11
40 2400 0.54 12079 7924.8 4155 0.10
45 2700 0.50 12573 8915.4 3658 0.08
50 3000 0.46 12983 9906 3077 0.07
55 3300 0.44 13505 10896.6 2608 0.06
60 3600 0.41 13886 11887.2 1998 0.05
65 3900 0.39 14309 12877.8 1431 0.03
70 4200 0.37 14422 13868.4 553 0.01
75 4500 0.35 14817 14859 -42 0.00
80 4800 0.33 14902 15849.6 -948 -0.02
85 5100 0.32 15353 16840.2 -1487 -0.03
90 5400 0.31 15494 17830.8 -2336 -0.05
95 5700 0.29 15551 18821.4 -3271 -0.08
100 6000 0.28 15805 19812 -4007 -0.09
105 6300 0.27 16002 20802.6 -4800 -0.11
110 6600 0.26 16143 21793.2 -5650 -0.13
115 6900 0.26 16553 22783.8 -6231 -0.14
120 7200 0.25 16595 23774.4 -7179 -0.16
Modified FAA Method - WQ Storage Volume Calculations
Inputs | Tributary Area Output | Detention Volume
Return Period for Detention Control:Required Storage, cubic feet:
Catchment 'C':Required Storage, ac-ft:
Average
Outflow
Storage
Volume
Storage
Volume
Catchment Drainage Area, ac:
Release Rate, cfs:
Storm
Duration Time Rainfall
Intensity Inflow Volume
H:\King Soopers - City Market\CO, Fort Collins - KSS000146 -#18 College Drake\3.04 Grading-Drainage Studies\3.04.2 Proposed Drainage Reports-
Info\Hydrology\KSS 146_Rational_Routing.xls Page 1 of 2 10/5/2020
does not match WQ Calc
summary page - 2.4 cfs
based on 91 chambers.
Corrected as
noted
Project Number:King Soopers Store #146 Date:10/5/2020
Project Location:CO, Fort Collins
Calculations By:E. Mowinckel
Checked By:P. Dalrymple
Pond Description:Pond A 100-Year Detention
User Input Cell:Blue Text
100-year 86940
0.90 2.00
10.47
5.24
minutes seconds in/hr cubic feet cubic feet cubic feet acre-feet
5 300 9.95 28082 1570.5 26511 0.61
10 600 7.72 43576 3141 40435 0.93
15 900 6.52 55204 4711.5 50492 1.16
20 1200 5.60 63219 6282 56937 1.31
25 1500 4.98 70275 7852.5 62422 1.43
30 1800 4.52 76540 9423 67117 1.54
35 2100 4.08 80605 10993.5 69611 1.60
40 2400 3.74 84443 12564 71879 1.65
45 2700 3.46 87886 14134.5 73752 1.69
50 3000 3.23 91160 15705 75455 1.73
55 3300 3.03 94067 17275.5 76791 1.76
60 3600 2.83 95845 18846 76999 1.77
65 3900 2.71 99429 20416.5 79013 1.81
70 4200 2.59 102336 21987 80349 1.84
75 4500 2.48 104989 23557.5 81432 1.87
80 4800 2.38 107473 25128 82345 1.89
85 5100 2.29 109872 26698.5 83173 1.91
90 5400 2.21 112271 28269 84002 1.93
95 5700 2.13 114218 29839.5 84378 1.94
100 6000 2.06 116278 31410 84868 1.95
105 6300 2.00 118536 32980.5 85556 1.96
110 6600 1.94 120455 34551 85904 1.97
115 6900 1.88 122036 36121.5 85914 1.97
120 7200 1.84 124632 37692 86940 2.00
Average
Outflow
Storage
Volume
Storage
Volume
Catchment Drainage Area, ac:
Release Rate, cfs:
Storm
Duration Time Rainfall
Intensity Inflow Volume
Modified FAA Method - 100-Year Storage Volume Calculations
Inputs | Tributary Area Output | Detention Volume
Return Period for Detention Control:Required Storage, cubic feet:
Catchment 'C':Required Storage, ac-ft:
H:\King Soopers - City Market\CO, Fort Collins - KSS000146 -#18 College Drake\3.04 Grading-Drainage Studies\3.04.2 Proposed Drainage Reports-
Info\Hydrology\KSS 146_Rational_Routing.xls Page 1 of 2 10/5/2020
FYI:
Per criteria, this should be C x Cf
(1.25). or a max of 1.00.
However, since this is a detention
retrofit, not as big of a deal. I am
okay proceeding with the C = 0.9 in
this situation.
Noted, thank you
(i)(ii)(iii)(iv)(v)(vi)(vii)(viii)(ix)(x)(xi)(xii)
Vault ID
Total
Required WQ
Volume (cf)
Flow, WQ
(cfs)
Chamber
Type
Chamber Unit
Release Rate
(cfs)
Chamber Unit
Volume (cf)
Installed
Chamber Unit
Volume with
Aggregate
(cf)
Minimum No.
of Chambers
Total Release
Rate
(cfs)
Required
Storage
Volume by
FAA Method
(cf)
Minimum No.
of Chambers
Storage
Provided
within the
Chambers
(cf)
Total
Installed
System
Volume (cf)
A 14,649 13.40 MC-4500 0.026 106.5 162.6 91 2.366 5,137 49 9,691 14,796
(i) Calculated WQCV (Eq. 7-1 & 7-2)
(ii) 1/2 of the 2-year developed flow rate for the basin being sized (use half of the 2-year intensity for the time of concentration used in the calc - i.e. for 5 min Tc, use 1.425)
(iii) Per ADS, these equate to different chamber sizes they have available.
(iv) Flow rate thru the bottom of the Isolator Row chamber which is equal to the area of the bottom of the chamber multiplied by the flow rate per unit area (.35 gpm/sf).
(v) Volume within chamber only, not accounting for void spaces in surrounding aggregate.
(vi) Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit.
(vii) Number of chambers required to provide full WQCV within total installed system, including aggregate. (i) / (vi)
(viii) Release rate per chamber times number of chambers. (iv) * (vii)
(ix) FAA calc based on Flow, WQ and Total Release Rate.
(x) Number of chambers required to provide required FAA storage volume stored within the chamber only (no aggregate storage). (ix) / (v)
(xi) Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume. Greater of (vii) or (x) * (v)
(xii) System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required WQCV. Greater of (vi) or (x) * (vi)
(xiii) Total number of Water Quality System Chambers to be installed.
(i)(ii)(iii)(iv)(v)(vi)(vii)(viii)(ix)(x)(xi)
Vault ID
Chamber
Type
No. of Water
Quality
Chambers
Provided
Total No. of
Chambers
Provided
No. of End
Caps
Provided
Chamber
Volume (cf)
Installed
Chamber
Volume with
Aggregate
(cf)
Installed End
Cap Volume
with
Aggregate
(cf)
Water Quality
Volume
Provided (cf)
Total
Chamber
Volume
Provided (cf)
Total End
Cap Volume
Provided (cf)
Total
Installed
System
Volume (cf)
A MC-4500 91 463 46 106.5 162.6 115.3 14,796 75,283 5,303 80,586
(i) ADS chamber size provided in system.
(ii) Number of WQ chambers provided.
(ii) Number of chamber provided (including WQ).
(iv) Number of end caps provided.
(v) Volume within chamber only, not accounting for void spaces in surrounding aggregate.
(vi) Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit.
(vii) Volume includes end cap and void spaces (40%) in surrounding aggregate, per chamber unit.
(viii) Total Volume provided in WQ chambers. (ii) * (vi)
(ix) Total Volume provided in chambers, including WQ chambers. Excludes end caps. (iii) * (vi)
(x) Total Volume provided in end caps. (iv) * (vi)
(xi) System volume includes total number of chambers & end caps, excludes surrounding aggregate. (ix) + (x)
See additional Stage Storage tabulation for total system volume including surrounding aggregate.
WQ System Calculation Summary
Detention System Summary
H:\King Soopers - City Market\CO, Fort Collins - KSS000146 -#18 College Drake\3.04 Grading-Drainage Studies\3.04.2 Proposed Drainage Reports-Info\Hydrology\KSS 146_Rational_Routing.xls Page 2 of 3 10/7/2020
the FAA calc for stormtec calc has 3.6
cfs. These need to match. Suggest
FAA calc is not correct.
The total volume should be detention
+ water quality 86940 + 14649CF =
101,589 CF
corrected this value in FAA calc
modified table to include total vol-
ume
Project Name:King Soopers Store #146
Project No.:
Calculated By:E. Mowinckel
Checked By:P. Dalrymple
Date:10/5/20
(sf)(ac)
On-Site 378,401 8.69
Off-site 83,009 1.91
Total 461,410 10.59
On-Site 424,443 9.74
Off-site 34,651 0.80
Total 459,094 10.54
New Impervious Area 46,042 1.06
Modified Impervious Area 378,401 8.69
Required Minimum Impervious Area to be Treated 424,443 9.74
Total Impervious Area Treated 424,443 9.74
Portion of New and Modified Impervious Area 100%>75%
Notes:
1) Refer to Impervious Area Exhibit, Appendix D
Existing Impervious Area
Proposed Impervious Area
75% On-Site Treatment by LID Requirement (without Pavers)
KSS000018.02
LID SUMMARY TABLE
H:\King Soopers - City Market\CO, Fort Collins - KSS000146 -#18 College Drake\3.04 Grading-Drainage Studies\3.04.2 Proposed Drainage Reports-Info\Hydrology\KSS 146_Rational_Routing.xls
I am unclear if the project is providing the required water quality treatment area.
Please do the following things:
-Move this table to the report body in the water quality (WQ) discussion section.
-For a redevelopment project, the off-property areas are not subject to WQ/LID
requirements. Please remove the off-site (off-property) impervious area from this
tabulation.
- For clarification: All areas that are within your property (on-site) need to be in this
tabulation, even if they "drain off-site".
-It may help to add landscape areas to this tabulation.
-Moved to the report body
-revised calcs to only address on-site areas
- per discussions with the City, on-site impervi-
ous areas infeasible to be captured on-site are
acceptable
-table has been simplified and summarizes the
impervious areas more clearly without needing
to include pervious area
RxPICKUP21
CO
CO
E
EVT
ECB
GM
E
E
E
E
TL
TL
E
TL
GM
IR
TL
CO
CO
E
E
IR
IR
IR
EVT
ECB
GM
IR
CO
IR
E
E
E
E
TL
TL
RI
CO
EM
WM
GM
DYHDYHE
IR
GM ECB
ECB
DYH
DYH
ECB
EME
TL
GM
WM
IR
CO
TL
CO
CO
-
-
-
-
-
-
-
-
-
-
-
-
-
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STAMP
H:\King Soopers - City Market\CO, Fort Collins - KSS000146 -#18 College & Drake\CADD\Exhibits\KSS146_Impervious Areas.dwg - Erland Mowinckel - 10/5/2020Init.#Issue / DescriptionDate
THESE PLANS ARE AN INSTRUMENT OF SERVICE
AND ARE THE PROPERTY OF GALLOWAY, AND MAY
NOT BE DUPLICATED, DISCLOSED, OR REPRODUCED
WITHOUT THE WRITTEN CONSENT OF GALLOWAY.
COPYRIGHTS AND INFRINGEMENTS WILL BE
ENFORCED AND PROSECUTED.
COPYRIGHT
6162 S. Willow Drive, Suite 320
Greenwood Village, CO 80111
303.770.8884
Planning. Architecture. Engineering.
O
www.gallowayUS.com
C 2016. Galloway & Company, Inc. All Rights Reserved
PRELIMINARYNOT FOR BIDDINGNOT FOR CONSTRUCTIONDate:
Drawn By:
Project No:
Checked By:
KSS000146
OF 1EXHIBIT FORMIDTOWN GARDENS MARKETPLACEKING SOOPERS MARKETPLACE #146S. COLLEGE AVE. & DRAKE RD.FORT COLLINS, COLORADOEKM
PJD
10/07/2020
IMPERVIOUS AREA EXHIBIT
1SCALE: 1"=40'
0 20 40
This area should have WQ treatment
provided or explain why it is not
necessary
Please draw a boundary around "new and
modified" impervious areas on the property
and report this are - this is the required
water quality treatment area.
This area should have WQ treatment
provided or explain why not necessary
Per discussions with the City, this area is infeasible to capture to
the constraint of matching existing grades along the north edge of
pavement. creating a low point here would crease unacceptable
cross-slopes
Per discussions with the City, this area is infeasible to capture to
the constraint of matching existing grades along the north edge of
pavement. creating a low point here would crease unacceptable
cross-slopes. However, an inlet has been provided to capture a
portion of this area and reduce the amount of runoff flowing offsite
the boundary delineations have been updated per the comments
regarding WQ & LID