HomeMy WebLinkAbout10ai CB55 COUNCIL COMMUNICATION
TO: Mayor and Council
FROM: Tyler Gelles, Victor Rachael
DEPARTMENT: Public Works, Utilities
DATE: October 6, 2025
SUBJECT:
CB 55 - Updated Englewood Storm Drainage Criteria Manual and
City Code Section 12-5-9
DESCRIPTION:
Updated Englewood Storm Drainage Criteria Manual and City Code Section 12-5-9.
RECOMMENDATION:
Staff recommends that Council approve an ordinance adopting the updated Englewood Storm
Drainage Criteria Manual and updated Code Section 12-5-9.
PREVIOUS COUNCIL ACTION:
July 11th, 2011 - The City Council Approved Ordinance No. 28, Series of 2005
authorizing the adoption of the Englewood Storm Drainage Criteria Manual as a
requirement and regulation for the City of Englewood.
September 23, 2019 - Study Session held to allow staff to review the proposed updated
document with the City Council.
January 27, 2020 - Study Session held to allow staff to review the proposed updated
document with the City Council.
March 2, 2020 - City Council approved the 1st reading of CB#8, an ordinance adopting
the updated storm drainage criteria manual.
March 23, 2020 - City Council approved the 2nd reading of CB#8, an ordinance adopting
the updated storm drainage criteria manual.
September 15, 2025 - Study Session held to allow staff to review the proposed updated
manual and code with City Council.
SUMMARY:
The City of Englewood Storm Drainage Criteria Manual (ESDCM) is the governing document
that determines what stormwater criteria projects must follow, both during and after
construction, and is adopted into City Code via section 12-5-10. The current ESDCM was
adopted in 2020, in response to the 2018 storm events. Due to recent development trends and
permit compliance requirements, an update to the ESDCM was required and staff worked with
Merrick & Company to provide review services for the proposed update. In addition, staff
proposes to modify City Code Section 12-5-9, Prohibited Discharges, to allow discharges in
accordance with CDPHE low risk discharge policy guidance documents.
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ANALYSIS:
Staff recommends approval of the proposed revisions to the Englewood Storm Drainage
Criteria Manual and City Code Section 12-5-9 to include discharges in accordance with
Colorado Department of Health and Environment (CDPHE) low risk discharge policy guidance
documents. These updates are required to maintain compliance with the City’s Municipal
Separate Storm Sewer System (MS4) permit and expand on the positive the work the City has
undertaken with regards to stormwater management and infrastructure.
Most of the revisions within the proposed update resolve grammatical errors and provide
additional clarity on permitting processes and stormwater criteria. Staff have proposed changes
to stormwater requirements that will affect development and redevelopment projects which are
summarized in the table below:
Section Current Proposed
2.3: Submittals
Drainage report and permanent
stormwater quality plans are
required before a grading permit can
be issued.
Modify to allow that if a project is
demolition only, applicant may
proceed with acquiring a grading
permit without a drainage report or
permanent stormwater quality plan.
2.3: Submittals N/A 30-day staff review window for
plans.
2.10: Stormwater
Management Plan
(SWMP) - Construction
SWMP required for 10,000 sq. ft. of
land disturbance or when soil is
exposed for more than 60-days
Lower SWMP requirement to 5,000
sq. ft. of land disturbance.
A grading permit is required.
2.11: Permanent
Stormwater Quality
Plan (Post-
Construction)
N/A Adopts exclusions in accordance
with MS4 Permit requirements.
2.11: Permanent
Stormwater Quality
Plan (Post
Construction)
Record drawing (As-built) required
before Certificate of Occupancy.
Added requirements for submission
before grading permit can be
terminated.
Require GIS and AutoCad files to be
submitted with record drawing.
3.6: Detention and
Stormwater Quality
Establishes thresholds for detention
and stormwater quality
requirements for development and
redevelopments.
Added projects meeting exclusions in
Section 2.11 are exempt.
CDPHE low risk discharge policy documents involve certain discharge activities that the state
has determined have a low environmental risk if discharged into the storm sewer system. Low
risk discharge policy documents are regularly developed or updated.
COUNCIL ACTION REQUESTED:
Staff requests that Council consider approval of an ordinance adopting the updated Englewood
Storm Drainage Criteria Manual and updated Code Section 12-5-9.
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FINANCIAL IMPLICATIONS:
To assist in the update of the manual and city code, staff worked with the consulting firm Merrick
& Company via an on-call contract total of $33,350, funded from the stormwater enterprise fund.
There are no additional financial implications associated with the proposed revisions to the
ESDCM or City Code Section 12-5-9.
CONNECTION TO STRATEGIC PLAN:
The proposed amendments address the following strategic plan goals:
Infrastructure
Enhance and continue to updated planning, processes and projects to reduce the risk of
flooding.
Community Wellbeing
Promote and encourage beautification, cleanliness, and code compliance in the
neighborhoods.
Sustainability
Protection of water resources, including rivers and streams.
Infrastructure that is build and/or operates in ways that eliminate or minimize harm to the
environment and increase the health and well-being of its occupants.
Protection of our natural environment.
OUTREACH/COMMUNICATIONS:
Water and Sewer Board approved motion to recommend that City Council approve, by
Ordinance, the proposed revisions (July 8, 2025).
The proposed revisions were presented to attendees of the Stormwater Open House (August
28, 2025).
ATTACHMENTS:
Power Point Presentation
Revised City of Englewood Storm Drainage Criteria Manual
Revised City Code Section 12-5-9
Ordinance
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ORDINANCE COUNCIL BILL NO. 55
NO. INTRODUCED BY COUNCIL
SERIES OF 2025 MEMBER
A BILL FOR
AN ORDINANCE AMENDING TITLE 12, CHAPTER 5, SECTION 9 OF
THE ENGLEWOOD MUNICIPAL CODE TO ALLOW CERTAIN LOW-
RISK DISCHARGES, AND ADOPTING THE 2025 ENGLEWOOD STORM
DRAINAGE CRITERIA MANUAL.
WHEREAS, the Federal Clean Water Act requires that stormwater discharges be
authorized under stormwater discharge permits; and
WHEREAS, the City of Englewood operates under a Municipal Separate Storm
Sewer System (MS4) permit issued by the Colorado Department of Public Health and
Environment (CDPHE), Water Quality Control Division; and
WHEREAS, the City adopted the Englewood Storm Drainage Criteria Manual
(ESDCM) in 2020 in response to significant storm events in 2018, establishing the
governing standards for stormwater design, construction, and post-construction
management within the City; and
WHEREAS, recent development trends and MS4 permit compliance requirements
necessitate updates to the ESDCM to reflect current engineering practices, state and federal
regulations, and permit standards; and
WHEREAS, staff engaged Merrick & Company to provide professional review
services in support of the 2025 ESDCM update; and
WHEREAS, staff also recommends modifying EMC §12-5-9 (“Prohibited
Discharges”) to align with CDPHE low-risk discharge policy guidance documents, which
identify activities determined by the State to have a low environmental risk when
discharged into the storm sewer system; and
WHEREAS, the Water and Sewer Board reviewed and recommended approval of
the 2025 ESDCM the proposed EMC revisions at its meeting on July 8, 2025; and
WHEREAS, the City Council finds that adoption of the 2025 ESDCM and
amendment of EMC §12-5-9 are necessary to protect public health and safety, ensure
compliance with the City’s MS4 permit, and advance the City’s strategic goals relating to
infrastructure, community wellbeing, and sustainability.
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NOW, THEREFORE, BE IT ORDAINED BY THE CITY COUNCIL OF
THE CITY OF ENGLEWOOD, COLORADO, AS FOLLOWS:
Section 1. Amendment of Title 12, Chapter 5 Regarding Prohibited
Discharges. Englewood Municipal Code is hereby amended to read as follows (new
provisions underlined; repealed provisions crossed-through):
12-5-9: - Prohibited Discharges.
A. It shall be unlawful for any person to discharge or cause to be discharged to
the storm drainage system any polluting material or any other material which is not
composed entirely of storm water.
B. It shall be complete defense to the application of this section that such discharge
was made pursuant to an "NPDES" storm water discharge permit or resulted from
firefighting activities.
C. Except as such may be identified by the City as sources of polluting materials, this
section shall not apply to the following categories of non-storm-water discharges:
1. Water line and fire hydrant flushing;
2. Water-based fire suppression system testing;
3. Landscape irrigation;
4. Diverted stream flows;
5. Rising ground waters;
6. Uncontaminated ground water infiltration into the storm drainage system;
7. Uncontaminated pumped ground water;
8. Discharges from potable water sources;
9. Foundation drains;
10. Air conditioning condensation;
11. Irrigation water;
12.Springs;
13.Water from crawl space pumps;
14.Footing drains;
15.Lawn watering;
16.Individual residential car washing;
17.Flows from riparian habitats and wetlands;
18.Dechlorinated swimming pool discharges; and
19.Street washwater.; and
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20. Discharges in accordance with the CDPHE low risk discharge policy guidance
documents or other policy and guidance documents of the State.
D. Any person who violates any provision of this section shall be subject to a civil
penalty of not more that nine hundred ninety-nine dollars ($999.00) per day during
which such violation occurs or continues, or, upon conviction, a criminal penalty
punishable by a fine of not more than nine hundred ninety-nine dollars ($999.00)
per day during which such violation occurs or continues or by imprisonment for not
more than three (3) months or by both.
Section 2. The City hereby adopts the “2025 Storm Drainage Criteria Manual”
as the official stormwater design and technical criteria manual for the City as authorized
under EMC § 12-5-10. This manual shall govern the design, construction, and maintenance
of stormwater facilities within the City, unless otherwise provided by ordinance.
Section 3. At least one copy of the adopted manual is on file and available for
public inspection at the office of the City Clerk and shall remain so available while this
ordinance is in effect.
Section 4. Any future amendments or revisions to the “2025 Storm Drainage
Criteria Manual” shall not become effective within the City unless adopted by ordinance
following notice and public hearing as required by law. No future version of the manual shall
be deemed incorporated by reference unless explicitly adopted by the City Council.
Section 5. The Director of Utilities or designee may issue administrative
guidance or technical interpretations of the adopted manual, provided such interpretations do
not materially alter the standards set forth in the adopted edition. Any substantial
modifications or updates shall be presented to City Council for formal adoption.
Section 6. General Provisions Applicable to this Ordinance. The following
general provisions and findings are applicable to the interpretation and application of this
Ordinance:
A. Severability. If any clause, sentence, paragraph, or part of this Ordinance
or the application thereof to any person or circumstances shall for any reason be adjudged
by a court of competent jurisdiction invalid, such judgment shall not affect, impair or
invalidate the remainder of this Ordinance or its application to other persons or
circumstances.
B. Inconsistent Ordinances. All other Ordinances or portions thereof
inconsistent or conflicting with this Ordinance or any portion hereof are hereby repealed
to the extent of such inconsistency or conflict.
C. Effect of repeal or modification. The repeal or modification of any
provision of the Code of the City of Englewood by this Ordinance shall not release,
extinguish, alter, modify, or change in whole or in part any penalty, forfeiture, or liability,
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4
either civil or criminal, which shall have been incurred under such provision, and each
provision shall be treated and held as still remaining in force for the purposes of sustaining
any and all proper actions, suits, proceedings, and prosecutions for the enforcement of the
penalty, forfeiture, or liability, as well as for the purpose of sustaining any judgment,
decree, or order which can or may be rendered, entered, or made in such actions, suits,
proceedings, or prosecutions.
D. Safety Clauses. The City Council hereby finds, determines, and declares
that this Ordinance is promulgated under the general police power of the City of
Englewood, that it is promulgated for the health, safety, and welfare of the public, and that
this Ordinance is necessary for the preservation of health and safety and for the protection
of public convenience and welfare. The City Council further determines that the Ordinance
bears a rational relation to the proper legislative object sought to be obtained. This Safety
Clause is not intended to affect a Citizen right to challenge this Ordinance through
referendum pursuant to City of Englewood Charter 47.
E. Publication. Publication of this Ordinance may be in the City’s official
newspaper, the City’s official website, or both. Publication shall be effective upon the first
publication by either authorized method.
F. Actions Authorized to Effectuate this Ordinance. The Mayor is hereby
authorized and directed to execute all documents necessary to effectuate the approval
authorized by this Ordinance, and the City Clerk is hereby authorized and directed to attest
to such execution by the Mayor where necessary. In the absence of the Mayor, the Mayor
Pro Tem is hereby authorized to execute the above-referenced documents. The execution
of any documents by said officials shall be conclusive evidence of the approval by the City
of such documents in accordance with the terms thereof and this Ordinance. City staff is
further authorized to take additional actions as may be necessary to implement the
provisions of this Ordinance, and has authority to correct formatting and/or typographical
errors discovered during codification.
G. Enforcement. To the extent this ordinance establishes a required or
prohibited action punishable by law, unless otherwise specifically provided in Englewood
Municipal Code or applicable law, violations shall be subject to the General Penalty
provisions contained within EMC § 1-4-1.
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Storm Drainage Criteria
Manual and Code Updates
Presented By
Tyler Gelles, Stormwater Program Manager
October 6, 2025
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History of Storm Drainage Criteria Manual
•Current manual was drafted in 2020
•Response to 2018 storm events.
•City requirements are more stringent than the minimum
required by state.
•Governing document determining what stormwater criteria
projects must follow in the City, both during and after
construction.
•Adopted by City Code section 12-5-10
•Staff worked with Merrick & Company to provide review
services and complete 2025 manual update.
•Motion approved by Water and Sewer Board on 7/8/2025
•Presenting to public at Stormwater Open House on 8/28/25
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Why were revisions needed?
•Improve user experience and correct errors/omissions
•Incorrect or missing references.
•Revised definitions for clarity and consistency.
•Improved readability.
•Allow electronic submittals in lieu of requiring hard copies.
•Compliance with MS4 permit*
•Defining permitting and compliance requirements for projects.
•Establish thresholds and clarify stormwater processes*
•Subdivides lots, variance requests, etc.
•Adopt exemptions*
•Exemptions allowed by state MS4 permit but must be adopted into City code.
•Revise appendences and attachments
•Incorrectly numbered
•Outdated information
•Improved functionality *= Focus areas of presentation
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Summary of Changes
ReasonProposedCurrentSection
Demolition phase does not have
plans developed and separate
contractors. Still requires drainage
report and permanent stormwater
quality plan before building.
Modify to allow that if a
project is demolition only,
applicant may proceed with
acquiring a grading permit
without a drainage report or
permanent stormwater quality
plan.
Drainage report and
permanent stormwater quality
plans are required before a
grading permit can be issued.
2.3: Submittals
No timeframe in current manual. 30-day staff review window
for plans.
N/A2.3: Submittals
Code Clean up. Matches post-
construction and submittal
requirements in Section 2.3.
Added grading permit
requirements.
Lower SWMP requirement to
5,000 sq. ft. of land
disturbance.
A grading permit is required.
SWMP required for 10,000 sq.
ft. of land disturbance or when
soil is exposed for more than
60-days
2.10: Stormwater
Management Plan
(Construction)
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Summary of Changes
ReasonProposedCurrentSection
Code clean up. Exclusions must
be adopted to apply to applicable
developments
Adopts exclusions in
accordance with MS4 Permit
requirements.
N/A2.11: Permanent Stormwater
Quality Plan (Post-
Construction)
Extra safeguard to make sure
record drawing is provided and
can be digitally referenced.
Added requirements for
submission before grading
permit can be terminated.
Require GIS and AutoCad files
to be submitted with record
drawing.
Record drawing (As-built)
required before Certificate of
Occupancy.
2.11: Permanent Stormwater
Quality Plan (Post
Construction)
Code Clean up. Requirements of
Section 3.6 do not apply to
projects that meet exclusions
referenced in Section 2.11
Added projects meeting
exclusions in Section 2.11 are
exempt.
Establishes thresholds for
detention and stormwater
quality requirements for
development and
redevelopments.
3.6: Detention and Stormwater
Quality
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Exclusions and Code Revisions
•Section 2.11: Permanent Stormwater Quality Plan (Post-Construction)
•MS4 Exclusions:
Pavement management sites.
Excluded roadway redevelopment.
Excluded existing roadway areas.
Aboveground and underground utilities.
Large lot single family sites.
Non-residential and non-commercial infiltration conditions.
Sites with land disturbance to undeveloped land that will remain undeveloped.
Stream stabilization sites.
Trails.
Oil and gas exploration.
County growth areas
City Code Section 12-5-9:
Update to allow discharges in accordance with CDPHE low risk discharge policy guidance documents.
Surface cosmetic pressure washing operations to land.
Impervious trail building.
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Questions?
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Thank you
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Draft February, 2020June 2024.
ENGLEWOOD
STORM DRAINAGE
CRITERIA MANUAL
City of Englewood, Colorado
1000 Englewood Parkway
Englewood, CO 80110
303.762.2500
www.ENGLEWOODCO.GOV
September 25,
2025June 23, 2025
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DRAFT ( 2024June 2025)
TABLE OF CONTENTS LIST
SECTION 1.0 INTRODUCTION
1.1 TITLE……………………………………………………………. .......................................
1.2 PURPOSE .........................................................................................................
1.3 AMENDMENTS ..............................................................................................
1.4 AUTHORITY ...................................................................................................
1.5 DRAINAGE LAW ...........................................................................................
1.6 PERMITS ..........................................................................................................
1.7 DEFINITIONS AND ABBREVIATIONS ......................................................
1.8 REFERENCES .................................................................................................
1.9 DRAINAGE PUBLICATIONS FOR ENGLEWOOD ......................................
SECTION 2.0 STORM DRAINAGE PLANNING & SUBMITTAL REQUIREMENTS
2.1. GENERAL .........................................................................................................
2.2. REVIEW PROCESS…………………………………………………………. .
2.3 SUBMITTALS ..................................................................................................
2.4 SUBMITTAL REQUIREMENTS .................................................................... .
1) Format ......................................................................................................... .
2) Drainage Plan Sheets ................................................................................... .
3) Stormwater Management Plans (Construction BMPs) ................................ .
4) Permanent Stormwater Management Plan (Post-Construction BMPs)
2.5 LETTER REPORT ............................................................................................
2.6 PRELIMINARY REPORT ................................................................................
2.7 FINAL DRAINAGE REPORT……………………………………………… ..
2.8 FLOOD HAZARD STUDY .............................................................................
2.9 WETLANDS ………………………………………………………………… .
2.10 STORMWATER MANAGEMENT PLAN (CONSTRUCTION) ....................
2.11 PERMANENT STORMWATER QUALITY PLAN (POST-CONSTRUCTION)
Introduction ………………………………………………………… ........
Water Quality……………. .........................................................................
Designing for Maintenance ………………………………………. ...........
2.12 INSPECTION AND RECORD DRAWINGS .................................................. .
SECTION 3.0 DRAINAGE POLICY
3.1 GENERAL……………………………………………………………………. .
3.2 JURISDICTION BOUNDARIES………………………………………………
3.3 BASIN TRANSFERS…………………………………………………………...
3.4 DRAINAGE IMPROVEMENT COSTS...……………………… .................... .
3.5 DETENTION (STORAGE AND STORMWATER QUALITY) ………………
3.6 ROOFTOP DETENTION…………………………………………………… .. .
3.7 IRRIGATION FACILITIES………………………………………………… .. .
3.8 OFFSITE FLOWS…………………………………………………………… . .
3.9 EASEMENTS AND RIGHTS-OF-WAY ........................................................ .
3.10 OPERATIONS AND MAINTENANCE ………………………………………
Formatted: Not Highlight
Formatted: Not Highlight
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SECTION 4.0 TECHNICAL DESIGN CRITERIA
4.1 GENERAL .........................................................................................................
4.2 RESPONSIBILTY .............................................................................................
4.3 SOIL TYPES .....................................................................................................
4.4 HYDROLOGY .................................................................................................
1) Storm Frequency .........................................................................................
2) Rainfall Intensity ........................................................................................
3) Runoff Computations .................................................................................
a) Rational Method ..................................................................................
b) CUHP and SWMM ........................................................................
SECTION 5.0 OPEN CHANNELS AND HYDRAULIC STRUCTURES
5.1 GENERAL ……………………………………………………………………
5.2 OPEN CHANNELS ..........................................................................................
5.3 STREETS, INLETS, AND STORM DRAINS ..................................................
5.4 CULVERTS AND BRIDGES………………………………………………. ..
SECTION 6.0 STORAGE
6.1 GENERAL…………………………………………………………………… .
6.2 DETENTION CRITERIA ................................................................................
APPENDICES
Appendix
No.
Appendix Name
A STORM DRAINAGE CRITERIA MANUAL ORDINANCE
B PRELIMINARY REVIEW CHECKLIST
C FINAL DRAINAGE REPORT CHECKLIST
D SMALL LOT DEVELOPMENT FORM
E DRAINAGE CONSTRUCTION PLAN CHECKLIST
F SWMP PLAN CHECKLIST
FG PERMANENT STORMWATER QUALITY PLAN (POST CONSTRUCTION)
CHECKLIST
GH FORM SF-1 TIME OF CONCENTRATION
HI FORM SF-2 STANDARD STORM SYSTEM DESIGN
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LIST OF FIGURES
Figure
No.
Figure Name
1 ENGLEWOOD DRAINAGE BASIN MAP
2 RAINFALL INTENSITY – DURATION CURVES
3 ENGLEWOOD SOILS CLASSIFICATIONS MAP
4 GROUND COVER VELOCITIES
5 CHANNEL OR CONDUIT FLOW TIME NOMOGRAPH
6 STREET FLOWS – ALLOWABLE CAPACITIES
7 REDUCTION FACTORS FOR ALLOWABLE GUTTER CAPACITY
8 EO IN FHWA EQUATION FOR COMPOSITE CROSS SLOPES
9 (1-Eo) VALUES FROM FHWA EQUATION
DETAILS
Detail No. Detail Name
D-1 TYPE 16 INLET GRATE AND FRAME DETAILS
D-2 SINGLE TYPE 16 OPEN THROAT INLET ADJUSTABLE CURB BOX
D-3 DOUBLE TYPE 16 OPEN THROAT INLET ADJUSTABLE CURB BOX
D-4 TRIPLE TYPE 16 OPEN THROAT INLET ADJUSTABLE CURB BOX
D-5 TYPE 13 GRATE AND FRAME DETAILS
D-6 SINGLE TYPE 13 INLET
D-7 DOUBLE TYPE 13 INLET
D-8 TRIPLE TYPE 13 INLET
D-9 TYPE R CURB INLET
D-10 TYPE C INLET
D-11 T-BASE MANHOLES
D-12 MANHOLES
D-13 BOX BASE MANHOLES
D-14 MANHOLE DETAILS
D-15 INTERMEDIATE MANHOLE PLATFORM AND MANHOLE STEP DETAIL
D-16 CONCRETE ENCASEMENT CLOSURE OF RIGID CONDUITS
D-17 CHASE SECTION
All details are contained in the Design and Construction Standards and Specifications.
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FINAL DRAFT February 2020November 2024 ESDCM 1
SECTION 1.0
INTRODUCTION
1.1 TITLE
This Manual together with all future amendments shall be known as the City of Englewood Storm
Drainage Criteria Manual, hereinafter called the Manual.
1.2 PURPOSE
The purpose of the Manual is to provide minimum standards to safeguard the health, property and
public welfare through the proper control and handling of storm drainage flows and discharge.
This Manual is intended to establish similarity and consistency for the design, presentation, and
review of storm drainage improvements within the City of Englewood, Colorado. The design
guidelines contained in this Manual are intended for use as engineering guides in the solution of
drainage problems. Following the principles and practices, stated within, should facilitate the design,
submittal, and review process. The standards and specifications contained within are intended to
provide a consistent, adequate, and coordinated approach for dealing with drainage issues in order to
serve and protect the people who benefit from these facilities.
The criteria contained in this document provide adopted standards for the more frequent construction
and development issues. It is impossible to provide standards for every issue, so good engineering
judgment will be required when issues arise that are not addressed in this Manual.
The questions to be considered by the designer and the reviewer when encountering these situations
shall be:
❑ Will the safety of the affected property owners adjacent to and downstream from the
proposed facilities be enhanced or maintained?
❑ Will the safety of the property owners or occupants be affected by the proposed facility?
❑ Will the intended purposes for the proposed improvements be met?
❑ Will the operating and maintenance costs be kept at reasonable levels?
❑ Will the installation costs be kept at reasonable levels?
❑ Will the proposed construction be compatible with surrounding existing and proposed
improvements?
1.3 AMENDMENTS
The policies and criteria presented herein are basic guidelines which may be amended in the future as
new technology is developed, or as new regulations are adopted, and/or as experience gained in the use
of this document indicate a need for revision. Amendments will be applicable to all drainage studies
submitted after the effective date of amendment. However, final drainage reports which are submitted
for approval within sixty days after the effective date of amendment and which have prior approval of
a preliminary drainage report are exempt from the amendments.
1.4 AUTHORITY
1) General
A municipality’s inherent police powers enable it to enact ordinances that serve the public’s health
safety, and general welfare. These regulations together with future amendments have been adopted
as the Englewood Storm Drainage Criteria Manual pursuant to the City of Englewood Municipal
Code, Title §12 – Chapter -5, titled “The-10, entitled “City of Englewood Storm Water Utility and
Enterprise FundDrainage Criteria Manual”.
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FINAL DRAFT February 2020November 2024 ESDCM 2
2) Failure to Comply
It shall be deemed a nuisance to fail to comply with any provision of the Englewood Drainage
Criteria Manual. Any person, corporation, partnership, or other entity violating any provision of
the Manual shall be subject to Title 15 of the Englewood Municipal Code.
3) Stop Work Orders
Whenever any work is being performed contrary to any provision of the Manual, the Public
WorksUtilities Director or designee may order the work stopped by notice in writing served on any
person engaged in doing or causing such work. Any person shall forthwith stop such work until
authorized by the Director of Public WorksUtilities or designee in writing to proceed with the work.
It is unlawful to do or perform any work in violation of such stop order.
4) MHFD
It is recognized that certain projects financed wholly or in part with county, state, Mile High Flood
District (MHFD), or federal funds may be subject to standards prescribed by those agencies. Such
standards may be greater or less than the City of Englewood standards.
5) Variances
Variances will be considered on a case-by-case basis. Whenever there are practical difficulties
involved in carrying out the provisions of the Manual, the Public WorksUtilities Director may grant
variances for individual cases, provided that the Public WorksUtilities Director shall first find that
special circumstances make these procedures impractical and that the variance is in conformance
with the intent and purpose of the Manual, and providing that such variance does not lessen the
intent of the design requirement or the level of safety, service and quality intended by the Manual.
If a variance is granted by the Director of Utilities, that variance does not create precedent for future
variance requests. Each variance request shall be considered on the individual merits of the request.
The Public WorksUtilities Director shall require that sufficient evidence or proof be submitted to
substantiate any variance request. To qualify for a variance, it must be demonstrated that all options
to meet stormwater management requirements, as established in this manual, have been explored
and are not possible. Cost or self-inflicted hardships cannot be solely used as criteria to qualify for
a variance.
If upon review and denial of any variance request, the Developer or Design Engineer may appeal
to City of Englewood Water and Sewer Board.1
1.5 DRAINAGE LAW
Drainage engineering and design revolves around drainage law as well as the physical laws of gravity
and nature. A summary of the general principles of Colorado drainage law made by the courts as well
as the legislature have been summarized in the current UDSCMMile High Flood District (MHFD)
Urban Storm Drainage Criteria Manual (USDCM) (Volume 1 – Drainage Law).
1.6 PERMITS
Depending on the type of construction, type of improvement, and location of work, different permits
will be required to complete the project. The following is a list of possible (but not necessarily a
complete list of) permits required by concerned organizations:
City of Englewood:
❑ Building and Safety DivisionCommunity Development
o Building Permit
o Demolition Permit
1 All appeals regarding floodplain or floodway issues must be made to the Planning and Zoning Commission.
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❑ Department of Community DevelopmentUtilities
o Floodplain Zoning Permit
o Floodplain Development Permit
o Grading, Erosion, Sediment Control Permit
o
❑ Department of Public Works
o Right-of-Way Permits
▪ Public ROW Excavation Permit
▪ Public ROW Concrete Permit
o Grading, Erosion, Sediment Control Permit
State of Colorado:
❑ Colorado Department of Transportation
o Utility Permit
❑ Colorado Department of Health and Environment
o Construction Stormwater Discharge Permit
United States:
❑ Army Corp of Engineers
o 404 Permit to Disturb Wetlands
1.7 DEFINITIONS AND ABBREVIATIONS
The following list contains some of the technical terms and abbreviations used in this Manual:
404 Permit – A permit under Section 404 of the Federal Clean Water Act that is required for any
activities impacting “waters of the United States and jurisdictional wetlands” from the U.S. Army
Corps of Engineers.
A – Area
Ac – Acres
Base Flood – The flood caused by a 100-year storm event.
BFE - Base Flood Elevation—the water surface elevation for the 100-year flood.
BMPs – Best Management Practices – physical, structural, nonstructural, and/or managerial practices
that are intended to prevent, mitigate, or reduce pollution of stormwater. Also referred to as
Stormwater Control Measures (SCMs)
C – Coefficient of runoff that is a factor of the percentage of the impervious area and antecedent moisture
conditions as used in the rational equation.
CCR – Colorado Code of Regulations
CRS – Colorado Revised Statues
cfs – Flow rate of water measured in cubic feet per second.
Ci – Percent of impervious area
City – City of Englewood, Colorado, and its agents, representatives, and employees acting on its behalf.
CDOT – Colorado Department of Transportation
CDPHE – Colorado Department of Public Health and Environment.
CDPS – Colorado Discharge Permit System – Colorado’s version of the NPDES program.
CLOMR – Conditional Letter of Map Revision
COE – US Army Corp of Engineers
Formatted: No bullets or numbering, Tab stops: Not
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Common Plan of Development or Sale – A contiguous area where separate construction activities,
even if occurring at different times or by different entities, are considered part of a larger unified
project.
Construction Activity-Applicable construction activities include the land disturbing activity and all
activities and materials associated with construction site and located at, or contiguous to, the land
disturbing activities. Refers to ground surface disturbing and associated activities (land
disturbance), which include, but are not limited to, clearing, grading, excavation, demolition,
installation of new or improved haul roads and access roads, staging areas, stockpiling of fill
materials, and borrow areas. Construction does not include routine maintenance to maintain the
original line and grade, hydraulic capacity, or original purpose of the facility. Repaving activities
where underlying and/or surrounding soil is cleared, graded, or excavated as part of the repaving
operation are considered construction activities, Construction activity is from initial ground
breaking to final stabilization regardless of ownership of the construction activities. The WQCD
has determined that “contagious” means construction activities located in close proximity otto
each other (within ¼ mile).
Contractor – A person, partnership, corporation, or other legal entity who undertakes to construct,
install, alter, move, remove, trim, demolish, repair, replace, excavate, or add to any improvements
covered by this Manual, or any utility, or any other facility that requires work, workers, and/or
equipment in the process of performing the above named operations.
CMP – Corrugated Metal Pipe
CMPA – Corrugated Metal Pipe Arch
CUHP – Colorado Urban Hydrograph Procedure
CWB – Constructed Wetlands Basin
CWC – Constructed Wetlands Channel
CWCB – Colorado Water Conservation Board
CWQCD – Colorado Department of Health and Environment, Colorado Water Quality Control Division
D – Depth (measured in feet)
d – Diameter of pipe (measured in inches)
d50 – Mean particle or stone size (identified by diameter or dimension), where the mean is
determined by weight.
Design Engineer or Engineer – The engineer or corporation developing the engineering studies and
designs that are covered by this Manual for a proposed development or improvement of property.
Developer – The person, partnership, corporation, or other legal entity who is proposing changes to a
parcel of land within the City and who is legally responsible for the construction of the
improvements.
Development – Any manmade change to an improved or unimproved parcel of land, including but not
limited to buildings, other structures, dredging, filling, grading, paving, or excavations.
dh – Hydraulic Depth = (area/top width), as used in channel flow analysis
DRCOG – Denver Regional Council of Governments
EC – Elevation Certificate
EDB – Extended Detention Basin
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EGL – Energy Grade Line—The total energy level of the water. It is the sum of the velocity head,
pressure head and the elevation of the water surface.
E.M.C. – City of Englewood Municipal Code
Eo – Ratio of the flow in the depressed gutter section to the total flow.
EPA – Environmental Protection Agency
Erodibility – The susceptibility of a particular soil type to erosion by water or wind.
Erosion – The wearing away of soil or rock fragments by water, wind, or other geological agents.
Erosion Control Measures – Practices that slow or stop erosion.
ET – Evapotranspiration
Excess Urban Runoff Volume (EURV) – The difference between the developed condition and pre-
development runoff volumes. The runoff volume that results from approximately a 10% chance rainfall
event. This volume includes the WQCV.
FEMA – Federal Emergency Management Agency
FHBM – Flood Hazard Boundary Map
FHAD – Flood Hazard Area Delineation
Final Stabilization – Completion of all land disturbing activities, removal of all temporary sediment
controls, establishment of vegetative cover on exposed soil areas, and installation of permanent
improvements and stormwater BMPs.
FIRM – Federal Insurance Rate Map – The official map on which FEMA delineates flood hazard areas
and risk zones.
Flood – A general and temporary condition of partial or complete inundation of normally dry land areas
from the unusual and rapid accumulation of runoff of surface water from upstream areas.
Floodplain – The lowland area which may be temporarily covered by floodwaters attributed to the
accumulation of storm runoff from adjoining or upstream areas in major storm events where
special regulations have been adopted in order to protect the public, minimize flood damage and
the need for rescue and relief efforts.
Floodplain Administrator – Director of Community Development or authorized representative
Floodway – The channel of a river or watercourse and the adjacent land area that must be reserved in
order to discharge the Base Flood. Encroachments into the floodway area are prohibited.
ft – Feet
fps – Velocity measurement (feet per second)
Freeboard – A factor of safety usually expressed in feet above a certain water-surface elevation.
Froude Number – A ratio used to determine whether the flow in an open channel or covered conduit
with a free water surface is at critical velocity or equal to 1.0. Flow at or near the critical state
(1.0) is not stable and must be avoided.
Full Spectrum Detention - A stormwater detention facility design that provides water quality and
flood control benefits and reduces impacts on downstream channels by detaining the Excess
Urban Runoff Volume (EURV) and releasing it over a 72-hour period.
g – Rate of gravitational acceleration (32.2 fps/s)
GB – Grass Buffer
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General Permit – A permit issued by the State Department of Public Health and Environment, Water
Quality Control Division that authorizes discharges in compliance with the Clean Water Act, and
authorizes activities and programs designed to reduce or prevent pollution of State Waters.
GIS – Geographical Information System
GS – Grass Swale
HERCP – Horizontal Elliptical Reinforced Concrete Pipe
Historic – May mean “existing conditions” prior to redevelopment or change in use, when adequate
capacity in the existing drainage stormwater system exists; otherwise it shall mean the conditions
that existed prior to any development or improvements made to the property.
HGL – Hydraulic Grade Line—The profile of the hydrostatic pressure of water as it flows through pipes;
it represents the sum of the depth of flow and the pressure head.
Hydraulic Radius – Flow in channels are affected by the boundary roughness. To calculate - the actual
perimeter of channel in contact with the fluid is divided into the area of the flowing fluid gives
the hydraulic radius which is a major component in using Manning’s Equations to solve for
uniform flow in open channels.
I – Rainfall intensity expressed in inches per hour.
in. – Inches
Inspector – The authorized representative of the Public WorksUtilities Director assigned to make
detailed inspection of construction work to assure compliance with this Manual and the approved
plans. approved by the City.
iph – Soil infiltration rate expressed in (inches per hour).
Levee – A manmade structure designed and constructed in accordance with sound engineering practices
to contain, control, or divert the flow of water so as to provide protection from temporary
flooding.
Land Disturbing Activity – Any activity that results in a change in the existing land surface (both
vegetative and non-vegetative). Land disturbing activities include, but are not limited to clearing,
grading, excavation, demolition, installation of new or improved haul roads and access roads,
staging areas, stockpiling of fill materials, and borrow areas. Compaction that is associated with
stabilization of structures and road construction shall also be considered a land disturbing
activity.
Lowest Floor – The lowest enclosed habitable area of a building.
LOMA – Letter of Map Amendment
LOMR – Letter of Map Revision
Major Channel – Any channel or drainageway with 100 cfs or greater flow.
Manual – City of Englewood Drainage Criteria Manual
²/³ ½
Manning’s Equation – Q= 1.49*a*Rh *S𝑄=(1.49 ∗𝐴∗𝑅ℎ2 3⁄∗𝑅1 2⁄)
𝑛
n
may – To be interpreted as can or able, or more permissive than the use of “shall” in this Manual.
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MBP – Modular Block Porous Pavement
MDCIA – Minimizing Directly Connected Impervious Areas. The practice of routing concentrated
flows from impervious areas over grassy areas to promote infiltration and slow down runoff.
MEP – Maximum Extent Practicable – the standard for evaluating permit compliance.
Minor Development – Developments that involve little change to existing drainage patterns. By
definition therefore they must exhibit the following properties:
o Minor amount of grading work,
o Insignificant increase in runoff generated,
o Development actually improves drainage conditions,
o No additional runoff will be directed to adjacent private properties,
o Stormwater pollution is not currently a problem,
o And Development will not increase the potential for stormwater
pollution.
MH – Manhole
MHFD – Mile High Flood District (formerly known as the Urban Drainage and Flood Control District)
MS4 – Municipal Separate Storm Sewer System
n – Manning’s n, which is a friction factor, assigned to the surface that the liquid is traveling over or
through.
Nf – Froude Number = v / 𝑣
√𝑔∗𝑑ℎ
NFIP – National Flood Insurance Program
NOAA – National Oceanic & Atmospheric Administration
Nonstructural BMPs – Policies and practices and improvements designed to prevent or minimize the
migration of pollutants into receiving waters.
NPDES – National Pollutant Discharge Elimination System – Section 402 of the Federal Clean Water
Act.
NRCS – Natural Resource Conservation Service
Owner or Property Owner – Any individual, corporation, partnership, or other legal entity holding
controlling title on property which is in some way impacted or involved by development or
improving the property.
P – wetted perimeter used in finding the hydraulic radius.
PE – Professional Engineer licensed in the State of Colorado
PLD – Porous Landscape Detention
PLS – Professional Land Surveyor licensed in the State of Colorado
PPD – Porous Pavement Detention
Public Improvements – Improvements in the public way or in easements that are either in the control
of (or ownership by) the City.
Public WorksUtilities Director – The City of Englewood Public WorksUtilities Director or authorized
representative.
Q – Flow in cfs
_________
(g * dh )
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Rh – Hydraulic Radius = aA/P
RCBC – Reinforced Concrete Box Culvert
RCP – Reinforced Concrete Pipe
Record Drawings – The as-constructed drawings for all drainage improvements certified by a PE.
Redevelopment – Includes a site that is already substantially developed and has 35% or more of existing
hard surface coverage, the creation or addition of hard surfaces; the expansion of a building
footprint or addition or replacement of a structure; structural development including construction,
installation or expansion of a building or other structure, replacement of hard surface that is not
part of a routine maintenance activity; and land disturbing activities.
Regulation 61 – Colorado Discharge Permit System Regulations – includes stormwater regulations,
(5 CCR 1002-61).
Responsible Party – Any individual, corporation, partnership, or other legal entity involved in
developing improvements or maintaining BMPs covered by this Manual. Includes
subcontractors, contractors, developers, and owners, as applicable in the development process.
ROW – Right-of-Way – The total surface area, and the area above and below the surface that is
dedicated, deeded, reserved by, plat or otherwise owned or controlled by the City, for public use
for: infrastructure improvements, pedestrians, vehicular movement, parks, utilities, or storm
drainage and runoff.
RP – Retention Pond
S – Slope of the ground or conveyance element in ft/ft or percent.
SCS – Soil Conservation Service, now it is an agency of the United States Department of Agriculture
and called Natural Resources Conservation Service.
SFB – Sand Filter Extended Detention Basin
shall – An obligation or necessity to be interpreted as mandatory.
should – Advisory or recommendation, but not mandatory.
Specifications – Applicable specifications of agencies or organizations identified and shall mean the
latest edition or as revised.
SPP - Structural Plate Pipe
SPPA - Structural Plate Pipe Arch
Standards and Specifications – The “Engineering and Construction Standards and Specifications” of
the City of Englewood.
State Waters – Any and all surface and subsurface waters which are contained in or flow through the
state of Colorado, except for waters in sewage systems or waters in potable water distribution
systems.
Structural BMP – Facilities constructed to passively treat urban stormwater runoff before it enters the
receiving waters. These facilities serve as stormwater quality treatment devices. Also referred to
as Stormwater Control Measures (SCMs)
SCMs – Stormwater Control Measures - physical, structural, nonstructural, and/or managerial
practices that are intended to prevent, mitigate, or reduce pollution of stormwater. Also referred
to as Best Management Practices (BMPs)
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Substantial Conformance – No variation from the approved plans, other than minor changes as
determined by the City of Englewood.
SWMP – Stormwater Management Plan, for the purposes of this Manual SWMPs are the Construction
BMPs that deal with erosion control, sediment control, and drainageway protection.
T – Total spread of the water in the gutter and street in feet.
TMDL – Total Maximum Daily Load – the amount of a specific pollutant that a listed water body can
assimilate without violating applicable water quality standards.
UBC – Uniform Building Code
UDFCD – Urban Drainage and Flood Control District, now Mile High Flood District
USBR – United States Bureau of Reclamation
USDA – United States Department of Agriculture
USDCM – Urban Storm Drainage Criteria Manual
USGS – United States Geological Survey
v – Average velocity of flow in fps
Wetlands – Those areas that are inundated or saturated by surface or groundwater at a frequency and
duration sufficient to support vegetation typically adapted for life in saturated soil conditions.
WIR – Watershed Inches of Runoff
WQCV – Water Quality Capture Volume
1.8 REFERENCES
The primary references for this document are the “Urban Storm Drainage Criteria Manual” (USDCM)
by the Mile High Flood District, the City and County of Denver, “Storm Drainage Design & Technical
Criteria Manual, the City of Lakewood, “Storm Drainage Criteria Manual”, and the Greenwood
Village, “Drainage Criteria Manual.” Where specifically referenced, the guidelines and criteria of the
referenced manuals shall become a part of this Manual. All manuals and criteria referenced in this
Manual shall pertain to the most recent edition.
The following references were used in developing this Manual:
City of Englewood, “. “Design and Construction Standards and Concrete Specifications”..”
Englewood, Colorado, revised April 19972020.
City of Englewood, “Wastewater Collection Systems, Design and Construction”. Englewood,
Colorado.
City of Greenwood Village, “Storm Drainage Criteria Manual”. Greenwood Village, Colorado,
April 1999 and February 2019October 2022
City of Lakewood, “Storm Drainage Criteria Manual”. Lakewood, Colorado, August 1982.
City of Littleton, “Storm Drainage Design and Technical Criteria Manual”. Littleton, Colorado,
July 2019January 2022.
City and County of Denver, “Storm Drainage and Technical Criteria”. Denver, Colorado,
November 2013April 2024.
Code of Colorado Regulations, Colorado Discharge Permit System, (5 CCR 1002-61)
Colorado Department of Transportation, “Drainage Design Manual”, Draft. July 1994”. 2019.
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Sellards & Grigg, Inc., “Storm Drainage Plan”. Englewood, Colorado, January 1971.
Urban Drainage &Mile High Flood Control District, “Urban Storm Drainage Criteria Manual,
Volumes 1, 2, & 3”. Denver, Colorado, Volume 1, August 2018March 2024; Volume 2,
January 20172016; Volume 3, October 2019March 2024.
WRC Engineering and Urban Drainage & Flood Control District, “Storm Drainage Design and
Technical Criteria”. Arapahoe County, Colorado, 1987.
1.9 DRAINAGE PUBLICATIONS FOR ENGLEWOOD
The following publications are documents that pertain to the City of Englewood’s drainage systems
known at the time of publishing.
FHAD Studies:
❑ Big Dry Creek (Arapahoe County) and Tributaries, WRC Engineering, 11-1996
❑ Big Dry Creek, Downstream of County Line Road, RESPEC, Inc., 02-2018
❑ Harvard Gulch and Dry Gulch, Matrix Design Group Inc., 02-2017
Harvard Gulch, West Harvard Gulch and Dry Gulch, Gingery Associates, 12-1979
Master Plans:
❑ Big Dry Creek (Arapahoe County) and Tributaries Master Drainage Planning, Phase B,
Preliminary Design Report, WRC Engineering, 4-1998
❑ Big Dry Creek (Arapahoe County) and Tributaries Master Drainage Planning, Phase A,
Evaluation of Alternatives Report, WRC Engineering, 7-1996
❑ Big Dry Creek, Volume I, Major Drainageway Master Plan Report, VTN, Inc., 6-1975
❑ Big Dry Creek Major Drainageway Master Plan, VTN, Inc., 12-1974
❑ Big Dry Creek Major Drainageway Master Plan, Ayers Associates, 6-2015 Harvard Gulch and
Dry Gulch Major Drainageway Plan, Matrix Design Group Inc., 12-2016.
❑ Little Dry Creek, Volume I – Major Drainageway Planning Report, McCall-Ellingson and
Morrill, Inc., 2-1974
❑ Little Dry Creek Major Drainageway Planning, Volume 2 Drawing Report, McCall-Ellingson and
Morrill, Inc., 2-1974
❑ South Platte River – Chatfield Dam to Baseline Road, Phase B, Volume I Major Drainageway
Planning Report, Wright Water Engineers, Inc., 11-1985
❑ South Platte River – Chatfield Dam to Baseline Road, Phase B Volume II Recreation Plan, Major
Drainageway Planning Report, Wright Water Engineers, Inc., 11-1985
Outfall Studies:
❑ Englewood Outfall Systems Planning, Preliminary Design Report, Turner Collie and Braden,
Inc., 9-99
❑ Englewood Outfall Systems Planning Alternative Evaluation Report, Turner Collie and Braden,
Inc., 2-98
❑ Englewood Outfall Systems Plan update, Draft, Calibre Engineering Inc., XX-2019
Special Reports:
❑ City of Englewood Probable Areas Affected by Flooding from the 100-Year Storm, Turner Collie
and Braden, Inc., 3/98
❑ Little Dry Creek, City of Englewood, Cherry Hills Village, Greenwood Village, Arapahoe
County Hydrologic Evaluation, McLaughlin Water Engineers, 7-86
❑ South Platte River – A Plan For The Future – Chatfield to Brighton, a Friend, A Foe, MHFD, 12-
85
❑ South Platte River – Chatfield Reservoir to Brighton – Planning for the Future Brochure, 11-83
❑ South Platte River – Chatfield Dam to Baseline Road Stream Stability Investigation Final Report,
Michael A. Stevens, Consultant, 12-83
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❑ South Platte River Hydrologic Study – Chatfield to Sand Creek, Merrick and Company, 5-83
❑ City of Englewood Storm Drainage Plan, Sellards & Grigg, Inc. 1-71
❑ Floodproofing Study and Outfall System Plan update, DRAFT, Calibre Engineering Inc., XX-
2019
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SECTION 2.0
STORM DRAINAGE PLANNING & SUBMITTAL
REQUIREMENTS
2.1 GENERAL
The Public WorksUtilities Department has established, and the City Council has adopted construction
standards and engineering regulations for Development. All subdivision plats, planned unit
developments, or any other proposed construction submitted for approval shall include an adequate
drainage system analysis, BMP analysis, stormwater management analysis and appropriate storm
drainage system design. Plans, engineering analysis and calculations, diagrams, drainage reports and
other data shall be submitted, as required by the Public WorksUtilities Director, with each development
proposal or application for permit. The Developer is encouraged to have histheir Engineer meet with the
Public WorksUtilities Department so that the technical aspects of the project can be discussed prior to
submitting plans and reports.
The UtilitiesPublic Works Department in conjunction with City staff in other departments review these
submittals to insure conformance with City Standards. The City of Englewood is not responsible for the
correctness of design, dimensions, details, or quantities. All submittals are to be prepared by a registered
professional engineer licensed in the State of Colorado.
2.2 REVIEW PROCESS
Adequate time must be allocated in development planning to permit a complete review. The intent of
this Manual is to more clearly define the City’s criteria and reduce the time and effort required to develop
an acceptable drainage study. To improve the review process, all reports will receive an initial review
using the checklist in Appendix B to determine if all essential information is present. Engineering review
of the drainage plan will not be started until all essential information is present., and will be returned
within approximately 30 days. Design Engineers are encouraged to refer to the Final Drainage Report
Submittal OutlineReview Checklist (Appendix C) and to substantiate that all the needed information has
been provided or explain why items were not provided.
2.3 SUBMITTALS
Two copies of plansPlans and two copies of reports are required to be submitted electronically for each
initial submittal. If additional copies are required for agency referrals, including hard copy submittals,
the applicant will be notified.
Drainage reports are required and must be submitted in accordance with the requirements stated in this
Manual. Any comments made by the Utilities Public Works Department must be addressed and the
documents resubmitted until an approval is given.
Checklists2 have been developed in order to identify the information that needs to be provided in
drainage report submittals. The checklists may be used to determine the adequacy of the submittal.
Incomplete or key information omitted from the report may result in the report being rejected for review,
which could result in a significant delay in the development process.
An important part of the design and analysis of any hydraulic facility is the documentation. Drainage
reports are required and must be submitted in accordance with the requirements stated in this Manual.
2 Appendix B – Initial Review Checklist, Appendix C – Final Drainage Report Submittal OutlineReview Checklist,
Appendix E contains the checklist for drainage construction plans, and Appendix G contains the Best Management
Practices Plan Requirements.
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Drainage Reports and Plans shall include, as a minimum, the information in Appendix C – Final
Drainage Report Submittal Outline.Review Checklist. The required submittal items for the different
types of development are shown in Table 1.
If a development wishes to proceed with demolition of an existing structure prior to construction, and
there are no changes to grade, drainage, or negative impacts on adjacent properties, the applicant may
proceed with acquiring a grading, erosion, and sediment control permit without submitting a preliminary
or final drainage report and no permanent stormwater quality plan will be required. Please note, a
stormwater management plan will be required for erosion and sediment control as well as pollution
prevention practices. No construction or on-site improvements shall occur until the required submittal
items in Table 1 are submitted for the applicable development and a grading, erosion, and sediment
control permit, and all other applicable permits, have been issued.
Table 1 – Document Submittal Requirements
Development
Size
Preliminary
Report
Requirements
Final Report
Requirements
Stormwater
Management
Plan3
Requirements
(Construction)
Permanent
Stormwater
Quality4 Plan
(Post-
Construction)
5,000 sf to
0.5 Ac
Letter Report5 Final Report6 SWMP
Required
BMP Required
0.5 AC or
Greater
Preliminary
Report7
Final Report SWMP
Required
BMP Required
2.4 SUBMITTAL REQUIREMENTS
1) Format
Drainage reports shall be prepared onformatted as standard size paperdocument (8½ x 11). The
full reports shall be suitably bound including cover, tabs, etc., but a letter report may be stapled if
less than ten (10) pages.submitted electronically. Every copy of the report shall include a “Drainage
Plan Sheet”, which may be either folded and bound with the report, or folded and placed in a pocket,
which has been bound within the report.”.
2) Drainage Plan Sheets
The “Drainage Plan Sheets” shall consist of a be formatted as 22-inch x 34-inch or 24-inch x 36-
inch paper copies that aredocument and included with the reports. Any revisions to the drainage
plan sheets shall be noted on the plans together with revision dates. Once deemed acceptable, two
copies of the drainage plan(s), electronically signed and sealed by the PE, shall be submitted.
3 For the purposes of this Manual SWMPs are the Construction BMPs that deal with erosion control, sediment control,
and drainageway protection.
4 Stormwater Quality Management Practices – physical, structural, nonstructural, and/or managerial practices that
are intended to prevent, mitigate, or reduce pollution of stormwater and improve water quality.
5 If Letter Report indicates that all flows are going to be directed to a Public ROW and no flows are exiting the site
onto adjoining private properties and there are no floodplain or drainage problems associated with the site, then no
additional reports will be required unless a more detailed analysis is requested by the Director of UtilitiesPublic
Works.
6 Only required in cases where runoff must be directed onto adjoining private properties or floodplain or drainage
problems are associated with the developing the site or a more detailed analysis is requested by the Director of
Public Works
7 Required if parcel in question must go through the preliminary platting process, otherwise at the PE’s discretion
either a preliminary report can be submitted or PE may elect to proceed to final.
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The approved Drainage Plan Sheet shall be a part of the construction documents, plans and
specifications for the proposed development. NoNo grading, erosion, and sediment control or
building permit will be issued unless the approved Drainage Plan Sheet is included among the
construction documents.
3) Stormwater Management Plans (Construction BMPs)
The Stormwater Management Plan must be included with the final report, but is not required for a
preliminary report. USDCM (Volume 3 – Construction BMPs) shall be followed for developing
construction BMP measures for the project site and the associated standard details and their map
symbols shall be used on SWMP submittals. SWMPs shall be formatted as 22-inch x 34-inch or
24-inch x 36-inch paper copiesdocument and included with the report.
Within reason, the SWMP may be included on the Drainage Plan Sheets. The details of both
erosion control methods and drainage design must be legible and clear. If they are not clear when
drawn together, or if the UtilitiesPublic Works Department requests it, the plans shall be drawn
separately.
NoNo grading, erosion, and sediment control or building permit will be issued unless the approved
SWMP is included among the construction documents and is signed and sealed by a professional
engineer. In select cases, the Utilities Department may waive the requirement of the SWMP for a
minor development to be signed and sealed by a professional engineer for the purpose of acquiring
a grading, erosion, and sediment control permit.
4) Permanent Stormwater Quality Management Plan (Post-Construction BMPs)
All submittals shall include a section that describes the Post-Construction BMPs that prevent or
minimize water quality impacts. See Section 2.11
5) MHFD Design Spreadsheets
The MHFD maintains a library of Hydrologic and Hydraulic Software, Design Tools and BMP
Sizing tools that may be used as a part of the submittal. All calculations submitted shall be complete
and presented in a logical format that is easily read. Time of Concentration calculations and
Rational Method runoff calculations shall use the forms SF-2provided in Appendices G and SF-3H
(or a reasonable facsimile).
2.5 LETTER REPORT
1) General Provisions
A letter report replaces a preliminary report for development sites less than 0.5 acre; although, the
UtilitiesPublic Works Director has the right to require a drainage report, or any part of, if it is
deemed necessary. The letter report shall include a letter written to the UtilitiesPublic Works
Department briefly summarizing the proposed development and include a completed “Small Lot
Development Form”, found in the Appendix D of this Manual, and a site plan with the necessary
information provided. The letter report will be submitted to the UtilitiesPublic Works Department
for review and comment or approval.
A letter report may also be submitted for a development or redevelopment that will not increase the
historic runoff from the site, or in certain cases where the increased runoff will not exceed the
allowable limits from the master plan studies as listed in Section 1.9, or when the increase in runoff
is minor and it is obviousUtilities Department staff has determined that the developed flows will
not cause any hardship to downstream property owners, or overburden existing municipal systems.
The letter report shall provide all necessary documentation in order to substantiate that the
requirements for a letter report are met. The UtilitiesPublic Works Department may approve the
letter report if all the issues have been satisfactorily addressed. Letter report approvals are strictly
at the discretion of the UtilitiesPublic Works Director. If the UtilitiesPublic Works Director
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determines that the flows from a development do not meet the criteria established for a letter report,
then the applicant must provide a final drainage report that meets the criteria of the City.
2) Procedure
Two (2) copies of theThe letter report willshall be submitted electronically for preliminary review.
The UtilitiesPublic Works Department will review and make any comments deemed necessary on
the submitted drainage report and may return an annotated review copy to the submitter in cases
where it would help to clarify the City’s comments or concerns.
If corrections are needed, the UtilitiesPublic Works Department shall request the letter report be
resubmitted with corrections. A resubmittal, if requested by the UtilitiesPublic Works Department,
must be accompanied with the annotated review copy containing the City’s comments. All
resubmittals shall include a cover letter summarizing how the City comments were addressed.
Letter reports and the plan sheets shall be signed and sealed by the professional engineer that
provided guidance, supervision, and is responsible for the design.
After the report is approved, then the construction plans submitted for grading, erosion, and
sediment control and building permit approval must contain sufficient information to document the
assumptions and recommendations contained in the letter report.
2.6 PRELIMINARY REPORT
1) Purpose
The purpose of the preliminary report is to identify and define drainage problems associated with
the proposed development, and to define conceptual solutions. For a detailed list of the submittal
requirements, see Appendix C – Drainage Report Submittal Outline.B – Preliminary Review
Checklist.
2) Rezoning Proposals
When a rezoning application and approval is conditional upon site plan approval, a preliminary
report is required.
3) Procedure
Two (2) copies of theThe preliminary drainage report willshall be submitted electronically for
review. The UtilitiesPublic Works Department will review and make any comments deemed
necessary on the submitted drainage report and may return an annotated review copy to the
submitter in cases where it would help to clarify the City’s comments or concerns.
If major corrections are needed the UtilitiesPublic Works Department may request the preliminary
report be resubmitted with corrections. A resubmittal, if requested by the City, must be
accompanied with the annotated review copy containing the City’s comments. All resubmittals
shall include a cover letter summarizing how the City comments were addressed.
In most cases the UtilitiesPublic Works Department will request that the City’s review comments
or concerns be addressed with the final drainage report. This can be accomplished by the City
attaching a conditional approval letter to the preliminary report that will list the items that need to
be addressed in the final drainage report. Approved preliminary reports and the plan sheets shall
be signed and sealed by the PE that provided guidance, supervision, and is responsible for the
design.
2.7 FINAL DRAINAGE REPORT
1) Purpose
The purpose of the final report is to transform the preliminary plans or conceptual plans to
construction plans. Final drainage reports are normally prepared and submitted with any documents
that will result in easements and rights-of-way to be recorded, or permanent structures being built,
such as the final plat, planned development, site plan, or building permit. The final drainage report
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shall contain all calculations and information identified in Appendix C—Final Drainage Report
Submittal OutlineReview Checklist.
2) Procedure
Three (3) copies of theThe final report willshall be submitted electronically for Utilities Public
Works Department approval. The Utilities Public Works Department will review and make any
comments deemed necessary on the submitted drainage report and may return an annotated review
copy to the submitter in cases where it might help to clarify the City’s comments or concerns. All
City review comments must be addressed. in a resubmittal package. All resubmittals shall include
a cover letter summarizing howincluding the City comments were addressedwith a response, and
in cases where annotated plans were provided, the annotated review copy containing the City
review comments should be included with the resubmittal. The final report will be resubmitted
until all comments and correction requests are satisfactorily addressed.
When the UtilitiesPublic Works Department deems the final drainage report acceptable, three (3)
copies of the drainage report and the “Drainage Plan Sheet” must be submitted for approval. The
reports and the plan sheets shall be signed and sealed by the professional engineer that provided
guidance, supervision, and is responsible for the design.
After the report is approved, then the construction plans are submitted for grading, erosion, and
sediment control as well as building permit approval and must contain sufficient information to
document the assumptions and recommendations contained in the final drainage report and plan.
TheBoth the grading, erosion, and sediment control permit and building permit submittal
packagepackages must include the SWMP and the approved drainage report and plans.
2.8 FLOOD HAZARD STUDY
1) General Provisions
Proposed development or improvements in the flood hazard zone shall meet the requirements of
Title 16 of the Englewood Municipal Code – Unified Development Code. EMC Title 16-410:
Floodplain Overlay District can be found in Appendix H. The flood hazard study shall be in the
form of a final drainage report and shall include all such computations necessary to show that the
requirements of Title 16 are met.
Copies of the City of Englewood Flood Hazard Boundary Map or the Arapahoe County FIRM
maps may be obtained through the City Floodplain Administrator.
2) Floodplain Zoning Permit
A Floodplain Zoning Permit and a Development Permit must be obtained from the Floodplain
Administrator before any major drainageway can be altered or relocated. Whenever a Development
proposes to alter a major drainageway, the Developer is responsible for submitting construction
plans and calculations that meet MHFD criteria, and then to build the necessary improvements in
accordance with MHFD requirements so that the improvements will be eligible for MHFD
maintenance. In addition, the CLOMR, and LOMR, and all other costs related to revising
Floodplain or Floodway locations and limits, shall be borne by the Developer and shall be done in
accordance with FEMA criteria. A CLOMR must be issued by FEMA prior to the City issuing a
building permit for any structure where Floodplain modifications are necessary, and when
construction is completed, the Developer is required to prepare and submit all required documents
for FEMA approval and issuance of a LOMR. A certificate of occupancy shall not be issued until
a FEMA approved LOMR is received.
3) Floodplain Development Permits
A Development Permit must be obtained from the Floodplain Administrator prior to the use of any
fill, construction of structures, or storage of materials in any portion of a floodplain.
4) Floodways
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Because Floodways are extremely hazardous due to the velocity of floodwaters, which carry debris,
and because the drainage conveyance capacity of the drainageway must be protected and
maintained, all encroachments, fill, new construction, substantial improvements and all other
development are prohibited in any area designated as a Floodway except for:
a) New improvements that are intended to increase the capacity or the storage capability of the
Floodway.
b) New improvements that are intended to increase flood protection, decrease erosion, and
improve channel hydraulics, or to provide stormwater quality benefits.
c) Utilities that are designed, located, and installed such that:
(i) They are anchored and armored to withstand hydrostatic and hydrodynamic forces,
and the effects of buoyancy.
(ii) Equipment and appurtenances installed are resistant to flood damage.
(iii) The utilities will not permit infiltration of floodwaters into the system and/or will
not discharge from the system into the Floodway.
5) Disclaimer
The degree of flood protection required by Title 16 of the City of Englewood Municipal Code is
considered reasonable for regulatory purposes and is based on scientific and engineering
considerations. Larger floods than the 100-year design storm can occur. Conformance to the
requirements in Title 16, or this Manual, does not imply that areas will be free from flooding or
flood damage.
2.9 WETLANDS AND STATE WATERS
Wetlands and State Waters provide multiple important functions in an urban drainage system. A
wetlandWetlands and State Waters can reduce the peak flow discharge, provide park and aesthetic
benefits, as well as improve the water quality of storm runoff.
Existing Wetlands are protected by federal regulations. Disturbing or cutting wetland vegetation
withwithin designated wetland areas is prohibited except for the following:
▫ Hand cutting or removal by hand of noxious weeds;
▫ Thinning wetland vegetation to minimize mosquito habitat in accordance with a plan
prepared by an environmental specialist, and approved by the City.
▫ Work performed to protect the public health, safety, and welfare.
State Waters are protected by federal and state regulations. Disturbing streams, including the discharge
of any fill or dredge material, is prohibited.
The applicant shall identify existing wetland stateareasand state water areas that potentially could be
impacted by the proposed Development. Care should be taken not to encroach into a wetland or state
water, and to avoid causing changes that will affect the water sources to a wetland or state waters.
To the extent possible, no utility lines shall be located in wetlands. Prior to any disturbance to a wetland
or state water, the U.S. Army Corps of Engineers shall be contacted to determine if there are any 404
Permit requirements.
2.10 STORMWATER MANAGEMENT PLAN (CONSTRUCTION)
1) General
The Federal Clean Water Act requires that stormwater discharges be authorized under stormwater
discharge permits. A General Permit issued by the Colorado Department of Health and
Environment, Water Quality Control Division covers stormwater discharges from the City of
Englewood. Construction site stormwater runoff control is one of the minimum measures that
Englewood must address in order to be in conformance with the Colorado Discharge Permit
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System, or CDPS, under Regulation 61. Disturbed lands are subject to Erosion and can be a source
of significant discharges of sediment and other pollutants to receiving waters downstream.
Disturbed lands include all property from which vegetation has been or is to be temporarily or
permanently removed. A SWMP for the site is required if the disturbed area island disturbance
activities are greater than 10,0005,000 square feet, or if the soil area is to be exposed for more than
sixty (60) days (Englewood Municipal Code 16-6-8. A SWMP for the site must be developed and
submitted to the Department of UtilitiesPublic Works to obtain a building, construction, or site-
grading, paving, or development permit. This plan will identify the site -specific control measures
necessary to prevent and control soil erosion, sedimentation, and water pollution that may degrade
receiving waters downstream.
2) Permitting
If a SWMP is required for the construction activity, a grading, erosion, and sediment control permit
must be acquired from the Department of Utilities. The grading, erosion, and sediment control
permit must be approved prior to the start of any construction activity and remain active until the
construction activity is complete and the site has been permanently stabilized in accordance with
the approved SWMP. If the disturbed area exceeds one (1) acre, a Colorado Department of Public
Health and Environment (CDPHE) general Permit COR400000 must also be acquired from the
state prior to the start of the construction activity.
2)3) Contractor Responsibility
The contractor shall provide control measures to prevent or minimize the impact to receiving waters
as required by the plans and/or as directed by the Engineer in writing. The Contractor shall
effectively prevent and control erosion and sedimentation on construction sites at the earliest
practicable time. In general controlControl measures willshall be implemented prior to the
commencement of each construction operation or immediately after the area has been disturbed
unless an alternative construction phasing plan has been approved in writing by the Stormwater
Manager or designee.
Construction staging areas and vehicle maintenance activities shall be managed and controlled so
as to minimize the runoff of pollutants.
Disturbance of vegetation shall be minimized and limited to only what is shown on the construction
plans or as directed by the Design Engineer in writing. Prior to the start of construction activities,
a pre-construction meeting shall occur on-site with the Stormwater Manager or designee. At a
minimum, any persons responsible for compliance with the SWMP shall be in attendance. Any
persons deemed responsible for compliance of the SWMP, at any point during the duration of the
construction activity, shall be competent and knowledgeable in stormwater management and
pollution prevention practices.
All erosion, sediment and water pollution controls will be maintained in good working order. for
the duration of the construction activity in accordance with the approved SWMP. Sediment will be
removed, and devices repaired as soon as practicable but not later than 7 days after the surrounding
ground has dried sufficiently to prevent further damage from equipment needed for repair of control
measures On all projects where the disturbed area is equal to or greater than an acre, a rain gauge
shall be provided by the Contractor and located on the project site. Within 24 hours of a rainfall
event of 0.2 inches or more as measured at the project rain gauge, the Contractor will inspect the
entire project to determine the condition of the control measures. Sediment will be removed and
devices repaired as soon as practicable but not later than 7 days after the surrounding ground has
dried sufficiently to prevent further damage from equipment needed for repair of control measures.
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3)4) Owner Responsibility
AllPermit approvals are conditioned upon the use of the construction stormwater best management
practices (BMPs) developed are the documents that permit approvals are conditioned upon)
included in the approved SWMP. The Owners and Developers of the real property are ultimately
responsible for the proper installation and maintenance of all construction stormwater BMPs. If
the Contractor/Developer fails in this responsibility the City shall provide a verbal warning to the
Responsible Party, if the situation is not remedied, then a notice of violation shall be issued as well
as. In addition a stop work order for anymay be issued wherein all work at the sitemust cease,
except for work necessary for bringing the site into compliance with the SWMP. Failure to respond
to the notice of violation will result in a municipal summons.the property being declared a nuisance
and a municipal summons issued in accordance with Title 15 of the Englewood Municipal Code.
In some instances, the property may be declared a nuisance and a municipal summons issued
without a notice of violation being issued. If necessary, the City has the right to enter the property,
perform maintenance on the BMPs, and require reimbursement for the costs that may be incurred.
The control measures identified on the plan shall be installed and maintained throughout
construction and these efforts shall be coordinated with the permanent pollution control features
specified for the project’s post construction period. The Owner’s Representative shall inspect the
construction BMP control measures after each storm event in excess of 0.2 inches. All deficiencies
shall be noted and any necessary changes or maintenance will be completed within 24 hours.
Modifications to the SWMP shall be submitted to the Utilities Public Works Department within
seven days of implementation.
The responsible party or any individual deemed responsible for stormwater control measures
associated with the development shall be a qualified individual, as determined by the Stormwater
Manager or designee, who has undergone training and is knowledgeable in proper installation and
maintenance of stormwater control measures and pollution prevention practices.
5) Inspections and Enforcement
To ensure compliance with the approved SWMP, inspections will be conducted by the Utilities
Department throughout the duration of the construction activity. Inspection frequencies will be
determined based on project size, phase of construction activities, and/or environmental risk. If
non-compliance with the approved SWMP is observed during the inspection, a detailed report
identifying any instances of non-compliance, as well as any recommended corrective actions, will
be provided to the Responsible Party. The report will include a time frame that the Responsible
Party must correct any instances of non-compliance and will serve as a verbal warning. The
inspection report may be provided to the Responsible Party via electronic mail. Failure to comply
will result in enforcement actions in accordance with section 2.10.3 of this manual.
If multiple warnings or notice of violations are issued throughout the duration of the construction
activity, the City may require the responsible party and/or contractor to complete training, or other
steps deemed necessary by the Director of Utilities or designee, to assure compliance and protect
the environment.
4)6) Owner Acknowledgement
All SWMPs and BMPs shall include an “Owner Acknowledgement” block for the Property
Owner’s signature. If the document containing the owner acknowledgement statement is provided
under separate cover, it shall clearly state the owner’s name, mailing address, contact information,
and associated project address or identifier and be on official letterhead. The format for the Owner
Acknowledgement shall be:
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Left
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Project Address or Name:
Owner’s Name:
Mailing Address:
Phone:
Email:
All stormwater best management practices (BMPs) developed and included in the
development approval process are legally binding documents whereby the Owners of
the real property associated with the BMPs are held ultimately responsible for the proper
maintenance of all stormwater BMPs. If the Property Owner fails in this responsibility,
the City has the right
1. To enter the property, perform maintenance on the BMPs, and require
reimbursement for the costs that may be incurred, or
2. To declare the existence of a nuisance and issue Nuisance Abatement Notice to
the responsible party. Failure to comply with the Nuisance Abatement Notice
shall cause the person, corporation, partnership, or other entity violating the
stormwater management provisions of the Manual to be subject to Title 15 of
the Englewood Municipal Code.
I have reviewed the stormwater best management practices that are proposed and I
understand that the effective performance of BMP measures hinge upon proper
maintenance of the BMPs used, and I will commit to provide the required maintenance
and employee training program, in order to accomplish the goal of preventing or
reducing pollutant runoff from this property. Required maintenance of all structural
and non-structural BMPs and employee training will be conducted in accordance with
the approved drainage report prepared by [insert], titled [insert], dated [insert] and
approved stormwater management plan prepared by [insert], titled [insert], dated
[insert].
Owner Owner’s Signature
Date:
5)7) Project Management Principles
Careful project management and adherence to the following principles can achieve improved
erosion and sediment control:
❑ Fit the Development to the existing topography, soils, and vegetation as much as possible.
❑ Schedule construction operations in orderwith an objective to minimize soil exposure.
❑ Minimize disturbance and soil exposure by retaining natural vegetation, adopting phased
construction techniques, and using temporary cover.
❑ Vegetate and mulch all denuded areas to protect the soil from precipitation in order to minimize
the raindrop impact on bare soil.
❑ Minimize the steepness of slopes and control lengths of slopes by utilizing benches, terraces,
contour furrows, or diversion ditches.
❑ Utilize riprap, channel linings, or temporary structures in channels to slow runoff velocities
and allow drainageways to handle increased runoff from developed areas.
❑ Keep sediment on-site by utilizing sediment basins, traps, or sediment barriers.
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❑ Monitor and inspect sites frequently to assureensure the measures are functioning properly and
correct problems promptly.
The Construction BMP chapter in USDCM (Volume 3) shall be followed for implementing erosion control
measures on the project site. The objectives and requirements for the Stormwater Management Plan are
identified in Appendix GF – Stormwater Quality Best Management Practices Plan Submittal Requirements.
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2.11 PERMANENT STORMWATER QUALITY PLAN (POST-CONSTRUCTION)
Introduction
Englewood’s National Pollution Discharge Elimination System (NPDES) Municipal Separate Storm
Sewer System (MS4) General Permit issued by the Colorado Department of Health and Environment
mandates that adequate pollution control measures for both the construction and post construction
periods are provided and maintained. All commercial and industrial developments, regardless of size
and type, must provide an evaluation of the possible pollution sources that are common for the proposed
uses and identify the Structural and Nonstructural controls that are going to be provided to mitigate
adverse impacts to State Waters. The requirements for the Stormwater Quality Management Plan are
outlined in Appendix GF. BMP Owners are responsible for performing the required maintenance to
ensure the long-term operation and viability of stormwater quality facilities (structural and
nonstructural).
Water Quality
Water quality is an important part of site planning and design. A four-step process for stormwater
quality management is described in the Stormwater Management and Planning chapter in the
USDCM (Volume 3) and should be employed on all sites during the planning and design process.
The four steps are listed below.
❑ Step 1. Employ Runoff Reduction Practices
❑ Step 2. Implement BMPs that provide a Water Quality Capture Volume (WQCV) with slow
release
❑ Step 3. Stabilize drainageways
❑ Step 4. Implement site specific and other Source Control BMPs
With the NPDES regulations, it is essential that the City, the Design Engineer, the Property Owner,
and Contractors work together to design and implement Best Management Practices (BMPs) to clean
and/or prevent the pollution of stormwater. Pollutants come from stormwater runoff (rain) or non-
stormwater runoff (such as sprinklers, hoses, or cleaning devices). Refer to the BMP Selection
chapter in the USDCM (Volume 3) for guidance in selecting the appropriate structural BMPs for a
project site. Water quality treatment can occur with a standalone facility, in combination with
detention facilities or as part of a targeted source of pollution or planning effort...
1) Water Quality Control Measures
When developing a site, water quality control measures, or BMPs, are designed to improve water
quality and reduce hydromodification and the associated impact on receiving waters as described
in the UDSCMUSDCM (Volume 3). Englewood has adopted the approach for calculating the
WQCV found in the USCDMUSDCM (Volume 3).
Water quality facilities in Englewood shall be designed to capture and treat runoff from the 80th
percentile event which is equal to a rainfall depth of 0.6 inches. Calculation of the WQCV is
dependent on proposed site imperviousness and the type of BMP selected. See the Calculating
the WQCV and Volume Reduction chapter in the UDSCMUSDCM (Volume 3) for equations and
guidance in calculating the WQCV. The Treatment BMPs chapter in the USDCM (Volume 3)
provides a listing of treatment BMPs and design criteria for post construction urban runoff control
measures. Alternate designs may be considered, but they must meet the functional requirements
of the BMPs identified by MHFD.
2) WQCV and Full Spectrum Detention
WQCV functions are incorporated into Full Spectrum Detention. Guidance for incorporating five
types of WQCV treatment BMPs into detention facilities is provided in the USDCM Volume 2
(Storage Chapter).
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3) Industrial and Commercial BMPs
Special consideration should be given to industrial and commercial impacts to a site. If
developing an industrial site the Source Control chapter USDCM (Volume 3 – Source Control
BMPs) should be followed.
Designing for Maintenance
During design, consideration must be given to the short and long-term maintenance of all BMPs.
Long term success dictates that each BMP must perform its intended function. All stormwater quality
management plans developed and included in the development approval process are legally binding
documents whereby the Owners of the real property associated with the BMPs are held ultimately
responsible for the proper maintenance of all stormwater BMPs, if. If the Property Owner fails in this
responsibility the City has the right to enter the property, perform maintenance on the BMPs, and
require reimbursement for the costs that may be incurred.
Because the effective performance of BMP measures hinge upon proper maintenance of the BMPs
used, signed acknowledgements by the Property Owner must be given to the Utilities Public Works
Department. The signed acknowledgements shall reference the approved plan and/or documents that
show the Structural and Nonstructural controls, the required maintenance and employee training
program, and their commitment to the goal of preventing or reducing pollutant runoff from their
property. If the signed acknowledgements are provided under separate cover, it is recommended that
the Structural and Nonstructural controls, the required maintenance and employee training program
are included as attachments within the document.
All Permanent Stormwater Quality Plans shall include the Owner’s Acknowledgement Statement in
section 2.10.
Exclusions
As defined in the Municipal Separate Storm Sewer System (MS4) General Permit issued by the
Colorado Department of Health and Environment, the following types of sites may be excluded from
providing post-construction stormwater management:
• Pavement management sites.
• Excluded roadway redevelopment.
• Excluded existing roadway areas.
• Aboveground and underground utilities.
• Large lot single family sites.
• Non-residential and non-commercial infiltration conditions.
• Sites with land disturbance to undeveloped land that will remain undeveloped.
• Stream stabilization sites.
• Trails.
• Oil and gas exploration.
• County growth areas
2.12 INSPECTION AND RECORD DRAWINGS
A professional engineer retained by the Developer, preferably the Design Engineer, shall inspect the
construction of the improvements for the purpose of determining conformance with the approved
drainage plan. This inspection shall include verification that the following conform reasonably to the
drainage plan:
❑ Finished floor elevations
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❑ Sizes, grades, locations, and elevations of drainage structures, channels, pipes, etc.
❑ Drainage facilities are located within the dedicated drainage easements.
❑ Location of basin boundaries
❑ Detention pond volumes
❑ Facilities appear to be constructed in a workmanlike manner
❑ Facilities and onsite grading function as intended in accordance with the approved drainage
report and plans.
❑ Stormwater Management control measures implemented or constructed.
❑ Best Management Plan measures implemented or constructed.
❑ Wetland mitigation measures implemented
❑ Floodplain boundaries certified
❑ Permanent field benchmark verified and certified
Any significant deviations from the approved drainage plan shall be annotated on the Record Drawings.
Redline or cloud mark-ups of the approved construction drawings are the preferred method for
indicating significant deviations. Significant deviations are those that exceed the following tolerances:
❑ Elevations................. ± 0.2 ft.
❑ Slopes …………… .. ± 10.0% deviation from specified slope or grade,
(i.e. 0.2% deviation for a 2% design grade)
❑ Distances .................. ± 1.0%
❑ Volumes ................... ± 5.0%
The Engineer will note any significant deviations on the approved drainage plan sheet and place the
certification and notations required for the “as-built” drainage plan. When the Design Engineer is
satisfied with the work that was done, then the Engineer shall include the following statement on the
Record Drawings:
I hereby declare that: I have performed a field review of the constructed
drainage facilities on this plan. The facilities are in substantial conformance
to the approved drainage plan, they appear to have been constructed in a
workmanlike manner, and the as-built improvements will function and
perform in accordance with the intended purposes of the approved drawings
and specifications.
(Seal and Date)
Registered P.E., State of Colorado
No.
The document will then be returned to the UtilitiesPublic Works Department for filing as the Drainage
Plan Record Drawing. The Record Drawings must be on file before the grading, erosion, and sediment
control permit can be terminated or a Certificate of Occupancy will be issued. . The document submittal
shall include a Shapefile and DWG file of the Drainage Plan Record Drawing compatible with ArcGIS
and AutoCAD. Drainage Plan Record Drawing should include all drainage facilities, infrastructure,
easements, or other information deemed necessary by the Utilities Department.
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SECTION 3.0
DRAINAGE POLICY
3.1 GENERAL
Providing for adequate drainage in Englewood is necessary in order to preserve and promote the
general health, welfare and economic well being of the city and the surrounding area. Drainage is a
regional issue that affects all governmental jurisdictions. As a result, any successful drainage system
will require an integrated approach to drainage that involves public and private concerns working
together.
3.2 JURISDICTION BOUNDARIES
Since drainage considerations and problems do not respect jurisdictional boundaries, the policy of the
City shall be to cooperate fully with neighboring jurisdictions and make every effort to address their
issues and concerns. Drainage referrals will be sent out to MHFD and neighboring jurisdictions when
a Development is located in proximity toimpacts a major drainageway or crosses a city boundary.
3.3 BASIN TRANSFERS
The diversion of storm runoff from one basin to another shall be avoided unless specific and prudent
reasons justify and dictate such a transfer. In general, in which case a variance must be requested and
approved by the Department of Utilities staff. In general, inter-basin transfer must be prevented since
it violates a basic principal of drainage law that upstream properties have a natural easement to
discharge onto downstream properties so long as it is not sent down in a manner or quantity that
causes more harm than formerly.
3.4 DRAINAGE IMPROVEMENT COSTS
Where drainage improvements are identified by site-specific drainage reports or by drainage master
plans as needed in order to facilitate development or redevelopment then the costs to design and build
the required drainage improvements shall be borne by the Developer. In other words, because the
development is creating the need for the drainage improvements in order to facilitate development, then
the costs for the improvements should be borne by the Development and not the citizens of the City of
Englewood. Examples where developments should bear all the costs of drainage improvements are:
❑ All curbs, gutters, channels, detention areas, inlets, storm sewers, culverts, bridges, swales
and other drainage facilities that are required to facilitate development of the site.
❑ All minor channel improvements required that must be built in order to maximize the use
of the site.
❑ All major channel improvements in cases where the Developer chooses to maximize the
use of the site and/or encroach into an official Floodplain as identified in Title 16 of the
EMC. The Developer is creating the need for these improvements since filling in the
Floodplain reduces valuable channel storage capacity and therefore increases downstream
flow peaks.
❑ All extensions of the existing storm drainage system through or around the Development
where pipe size is 24-inch diameter or smaller.
❑ Any changes or modifications to the existing storm drainage system that must be done to
facilitate development.
The exceptions to this general policy are when the City requires that the new Development or
redevelopment to install larger or additional drainage improvements than what is necessary to facilitate
development. Examples where City participation should be provided are:
❑ Where detention areas are increased in order to require the Development to provide
regional detention for offsite areas.
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❑ Where pipe sizes are greater than 24-inch diameter in order to accommodate offsite
drainage.
❑ Where pipe or channel sizes are increased to handle future developed flows from upstream
areas, then the differential costs for increasing the pipe or channel size should be subject
to City participation.
❑ In cases where City exactions of drainage improvements are not proportional to the impacts
caused by the Development.
3.65 DETENTION (STORAGE) AND STORMWATER QUALITY
Development along with the increase in impervious area increases peak flows and stormwater runoff
from a site and can alter the duration of storm runoff. Temporarily detaining stormwater runoff can
significantly reduce downstream flood hazards as well as reduce pipe and channel improvement
requirements and provide water quality treatment. Full spectrum detention facilities are required as
described in the USDCM because they. These facilities provide stormwater peak flow control for a
range of flow events and reduce flooding, stream degradation and water quality impacts related to
increased peak flows, duration and frequency the additional stormwater runoff originating from
increased impervious surface area. However, the benefits can only occur with consistent
administration of detention requirements and proper maintenance of the facilities.
Construction activities considered a common plan of development or sale should be considered a
development or redevelopment project for detention criteria and stormwater requirements outlined in
this section. The burden of proof in determining pre-developed rates, for the purpose of detention
criteria, shall be the responsibly of the Development or Redevelopment.
All New Developments and Redevelopments andshall meet the following detention and stormwater
quality requirements;
Development/Redevelopment
Characteristics
Detention Criteria
Sites 0.5 acres or greater with
disturbance of 10,000 sf or greater
All Planned Unit Developments
Permanent Stormwater Quality (Post Construction)
Full Spectrum Detention
Sites 0.5 acres or greater, but less
than 1.0 acre with disturbance less
than 10,000 sf
Permanent Stormwater Quality (Post Construction) for
disturbed area
Provide stormwater detention to reduce the peak flow to
pre-developed rates.
Sites from 5,000 s.f. to 0.5 acre
where the weighted imperviousness
is increased by a factor of 1.5 or
more
Permanent Stormwater Quality (Post Construction) for
disturbed area
Provide stormwater detention to reduce the peak flow to
pre-developed rates.
Building or parking/drive expansion
of 500 s.f. or less
Exempt
Detached Single Family Residence
on a minimum lot size of 6,000 s.f.
Exempt
Activities as defined in Section 2.11
Exclusions:
Exempt
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The maximum allowable 100-year release rate for a full spectrum detention facility for new
development is equal to 90 percent of the predevelopment discharge100-year peak flow rate for the
upstream watershed as described in the Storage chapter of the USDCM (Volume 2).
3.76 ROOFTOP DETENTION
Rooftop detention is prohibited. Rooftop detention does not provide the water quality benefits;
ponding water on roofs lead to premature failure of roofing systems; and the City cannot readily
monitor changes and alterations to roof detention facilities.
3.87 IRRIGATION FACILITIES
Irrigation ditches are designed with flat slopes and limited carrying capacity, which decreases in the
downstream direction. As urbanization occurs, ditch rights are sold and irrigation ditches are
abandoned. Developed stormwater runoff flows must be directed away from irrigation ditches. If the
developed flows cannot be directed away from the ditch, then the ditch will either need to be piped or
diversion structures installed downstream to remove excess storm flows from the ditch once the
design capacity of the ditch is exceeded. In such a situation a variance must be requested and
approved by the Department of Utilities staff.
3.98 OFFSITE FLOWS
One of the precepts of drainage law is that upstream properties own a natural easement on
downstream properties for surface waters flowing in its natural course. Therefore it is incumbent on
downstream properties to analyze offsite areas that may contribute flows onto their property and
mitigate the impacts of those flows. The offsite storm runoff shall be determined and included in the
drainage system design. Available drainage reports for developed offsite areas affecting the property
shall be reviewed and considered in the drainage system planning and design.
Runoff entering the site from offsite areas shall be computed using runoff coefficients found in the
Runoff chapter of USDCM (Volume 1).), or reference previously approved drainage reports for
upstream property.
3.9 EASEMENTS AND RIGHTS-OF-WAY
In the event that any watercourse, channel, stream, creek, or other natural drainage channel traverses
part or all of a proposed development, the subdivider shall dedicate adequate easements for storm
drainage and maintenance access purposes.
1) Public Drainage Easements
There are Public Drainage Easements that are provided to convey public drainage that are deeded
for the purposes of operation, repair, alteration, and maintenance of the storm water management
system where the City has accepted maintenance and operation responsibilities. These easements
shall be adequate in order to provide access for construction and maintenance and shall also cover
the outlet structure, storm water pipes, detention area berms, and other parts of the storm water
management system that the City deems necessary to be granted to the City. Public Drainage
Easements shall provide covenants running with the land stating that no buildings, fills,
excavations, structures, fences, or other alterations shall be constructed within the easement without
the express written consent of the UtilitiesPublic Works Department.
2) Drainage Conveyance Easements
There are also Drainage Conveyance Easements that are provided for storm drainage flows from
upstream lots onto downstream lots in order for the flows to be conveyed to the public drainage
system. Drainage Conveyance Easements are also provided to cover permanent drainage
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improvements that are a condition of development such as the detention pond, outlet structure,
storm water pipes, channels, pipes, inlets, detention area berms, and other parts of the storm water
management system built to benefit the site, or upstream or downstream properties. The
maintenance and operation of these drainage improvements are the responsibility of the Property
Owner. Drainage Conveyance Easements shall provide covenants running with the land stating
that no buildings, fills, excavations, structures, fences, or other alterations shall be constructed
within the easement without the express written consent of the Utilities Public Works Department.
The drainage conveyance easements and associated covenants should cover the entire stormwater
management system.
If for some reason the property owner fails to provide adequate maintenance or impedes storm
drainage flows, the City may enter the property in order to maintain and or re-establish the
drainage capacity, and perform any necessary work, the cost of which shall be the responsibility of
the property owner.
3.10 OPERATIONS AND MAINTENANCE
An important part of all storm drainage facilities is continued maintenance so that the system will
continue to function as designed. Maintenance and access requirements shall be considered
during the planning and design of all stormwater and detention facilities. Sediment and debris
must be periodically removed from detention basins, channels and storm sewers. Trash racks,
sidewalk chase drains, and inlets must be regularly cleared of debris to maintain system capacity.
Channel bank erosion damage must be repaired to avoid progressive deterioration, reduced
conveyance capacity, unsightliness, and structural failure. All sites will be designed to provide
access for vehicles and the construction equipment necessary to provide continued minor and
major maintenance.
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SECTION 4.0
TECHNICAL DESIGN CRITERIA
4.1 GENERAL
The City of Englewood was incorporated in 1903. Englewood is a southern suburb of Denver and is
surrounded by the cities of Denver, Littleton, Cherry Hills Village and, Sheridan and Greenwood
Village. The City of Englewood encompasses approximately 7 square miles. The City lies within the
South Platte River watershed at the eastern foot of the Rocky Mountains and is exposed to the
sudden, high intensity rainstorms typical of this region. A number of large drainage basins tributary
to the South Platte River cut through the City (see Figure 1 –Figures 1A and 1B – City of Englewood
Storm Drainage Basin MapBasins). Because the City is mostly developed, there are existing storm
drainage systems that are being used. There are also master plan studies that have been completed
that evaluate the existing storm drainage systems and identify areas of need and recommended
improvements. A list of the available master plans and studies can be found in Section 1.9—
Drainage Publications for Englewood, of this Manual.
4.2 RESPONSIBLITY
The Design Engineer is responsible for the design produced. The calculations must follow the
guidelines in the Manual, but the accuracy and applicability of the calculations are the responsibility of
the Design Engineer.
4.3 SOIL TYPES
The predominant soil types in the City of Englewood fall into NCRS Hydrologic Soil Groups B and C.
These primarily consist of sands, loams, and clays. Large portions of the city have loamy foothill
material in the Nunn association in the “C” hydrologic soil group. The Floodplain areas for the South
Platte River, Little Dry Creek and Big Dry Creek are alluvial lands also of the Nunn association. There
are also large portions of the city that consist of well-drained soils of the Bresser association that are in
the “B” hydrologic soil group. There are also pockets of gravelly areas along the Platte River. For “B”
hydrologic soil groups, anSee the table below for initial infiltration rate of 4.5 inches per hour (iph) and
the final infiltration rate of 0.6 iph can be used. For “C”based on hydrologic soilsoils groups, the initial
infiltration rate is 3.0 iph. Figures 3A and the final rate is 0.5 iph. Figure 3 – 3B – City of Englewood
Soils Classification MapSoil Classifications identifies locations and soil classifications for the
Englewood area. If the Design Engineer has site-specific soil test data available, then the site-specific
data should be used.
NRCS HYDROLOGIC
SOIL GROUP
INFILTRATION (INCHES PER HOUR) DECAY
COEFFICIENT – a INITIAL – fi FINAL - fo
A 5.0 1.0 0.0007
B 4.5 0.6 0.0018
C 3.0 0.5 0.0018
D 3.0 0.5 0.0018
4.4 HYDROLOGY
The MHFD has concluded that NOAA Atlas rainfall information provides reasonable rainfall
information that should be used to develop design rainstorms. Rainfall depths for Englewood are listed
in Table 5. – Englewood Rainfall Depths for 1- and 6-hour storms (NOAA Atlas 14, Volume 8, Version
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2). The Intensity-Duration Curves found in Figure 2 – Rainfall Intensity-Duration Curves are derived
from the Rainfall chapter of USDCM (Volume 1) and included as a reference. The most recent NOAA
Atlas rainfall information shall be used to develop design rainstorms. The preliminary and final
drainage reports shall take into consideration three separate storms eventsstorm frequencies: water
quality, the initial storm, and the major storm. Historic and developed runoff shall be determined for
both storms for the site, including the entire basin tributary to the site.
1) Storm Frequency
The storm frequency to be used in drainage system design will be the storm frequency applicable
for the facility being designed as described in a), b), and c) of this section.
a. Water Quality: Refer to the Calculating the WQCV and Volume Reduction chapter of
USCDM (Volume 3) for guidance in sizing WQCV facilities.
b. Initial Storm: The initial storm occurs at frequent intervals. Drainage systems for the initial
storm are to be designed to minimize inconvenience, protect against minor damage, and
reduce maintenance costs.
The design frequency interval for the initial storm is the two (2) year storm for analyzing
storm runoff in streets, private driveway culverts, and for self-cleaning velocity checks in
storm sewer designs and culvert designs.
c. Major Storm: The design frequency interval for the major storm is the 100-year storm. The
drainage system for the major storm is to be designed to protect against loss of life,
substantial property damage, and maintain critical or emergency services.
2) Rainfall Intensity
Runoff for both the initial and major storm shall be based on the Rainfall Intensity – Duration
CurvesNOAA Atlas 14, Volume 8, Version 2. Access NOAA Atlas 14 at
https://hdsc.nws.noaa.gov/pfds/. Sample rainfall data for Englewood, Colorado shownthe region is
provided in Figure 2. the table below. City Staff reserves the right to provide revised rainfall if
needed.
Table 5 – Englewood Rainfall Depths for 1 and 6-Hour Storms (NOAA Atlas 14, Volume 8,
Version 2)
Storm Event Rainfall Depth in Inches
1-Hour Storm 6-Hour Storm
2-Year 0.82 1.27
5-Year 1.08 1.65
10-Year 1.31 1.99
25-Year 1.66 2.51
50-Year 1.95 2.94
100- Year 2.25 3.41
According to MHFD analysis, the most intense rainstorms in the Denver area typically begin and
end in the first hour of the storm. It is these short-duration, intense rainstorms that appear to cause
the most flooding problems. Therefore, it is the short duration1-hour, convective type storm, which
is used to provide the design storms used in this manual.
3) Runoff Computations
FiveFour methods of hydrologic analysis are described in the Runoff chapter of USDCM (Volume
1) and listed below
• The Rational Method; based on the Rational Formula: Q=CIA. Refer to the Runoff chapter
of UDSCMUSDCM (Volume 1) for the general procedure for Rational Method
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calculations, assumptions, limitations, time of concentration calculations, and runoff
coefficient selection guidance.
• The Colorado Urban Hydrograph Procedure (CUHP) for generating hydrographs from
watersheds, and
• The EPA’s Storm Water Management Model (SWMM), primarily for combining and
routing the hydrographs generated from CUHP.
• Use of published runoff information, and
• Statistical analyses.
Watershed size dictates whether the Rational Method or CUHP is applicable. The Rational Method
may be used for watersheds that are less than 90 acres. CUHP is applicable for watershed sizes from
0 to greater than 3,000 acres with basins above 160 acres requiring further subcatchment
division.See the table below for applicability of hydrologic methods by watershed area. Please refer
to the Runoff chapter of USDCM (Volume 1) for additional information on the applicability of
hydrologic methods by watershed size.
CATCHMENT
SIZE(ACRES)
IS THE RATIONAL
METHOD APPLICABLE?
IS CUHP APPLICABLE?
0 to 90 Yes Yes
90 to 160 No Yes
160 to 3000 No Yes1
Greater than 3000 No Yes (subdividing into smaller
catchments required)1
1 Subdividing into smaller subcatchments and routing the resultant hydrographs using SWMM may be needed
to accurately model a catchment with areas of different soil types or percentages of imperviousness.
CUHP and SWMM: CUHP is a method of hydrologic analysis based upon the unit hydrograph
principle. Refer to the Runoff chapter of UDSCMUSDCM (Volume 1) for background and guidance
in using CUHP. The Environmental Protection Agency’s (EPA’s) Stormwater Management Model
(SWMM) 5 is a computer model that is used to generate surface runoff hydrographs from
subcatchments and then route and combine these hydrographs. The procedure, described in the
Runoff chapter of UDSCMUSDCM (Volume 1) is limited to the routing of hydrographs generated
using CUHP software in SWMM.
MHFD has published macro-enabled Microsoft Excel spreadsheets to assist with Rational Method
(UD-Rational) and CUHP calculations. The spreadsheets are available at the MHFD website
(www.udfcd.org).www.mhfd.org).
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SECTION 5.0
OPEN CHANNELS AND HYDRAULIC STRUCTURES
5.1 GENERAL
The preliminary and final designs of open channels and hydraulic structures shall be as specified in this
section and in accordance with USDCM (Volumes 1 and 2).
5.2 OPEN CHANNELS
The preservation, enhancement, and restoration of stream corridors in the City as well as the design of
constructed channels and swales using natural concepts shall be in accordance with the Open Channels
chapter of USDCM (Volume 1). The USDCM guidance on open channel design is based on the
systematic application of key geomorphic and hydraulic principles and is encouraged to be undertaken
by a qualified design team representing a broad range of expertise such as engineering, geomorphology,
ecology, and landscape architecture.
Criteria referred to in this section appears in a number of chapters in USDCM (Volumes 1 and 2). Open
channel design, the use of riprap and boulders, methods of hydraulic analyses, and design parameters
for grass or rock-lined swales are all covered in the Open Channel chapter of USDCM (Volume 1).
The hydraulic analysis and design of grade controls structures are covered in the Hydraulic Structures
chapter of USDCM (Volume 2). Planning and design criteria for trails and access along channels are
covered in the Stream Access and Recreational Channels chapter of USDCM (Volume 2).
Revegetation along open channels is covered in the Revegetation chapter of USDCM (Volume 2).
Major channels include all streams, drainageways and channels that convey major storm discharges
greater than 100 cfs, or any channel that has a designated floodplain on the City’s Official Flood Hazard
Map. Any major channel constructed must meet the “Maintenance Eligibility Guidelines” established
by the MHFD.
5.3 STREETS, INLETS, AND STORM DRAINS
Design of streets, inlets, and storm drains for the purpose of conveying runoff shall be in accordance
with the Streets, Inlets, and Storm Drains chapter of USDCM (Volume 1) except as specified in this
section. In addition to design guidance in USDCM (Volume 1), MHFD has computer software design
aids related to streets, inlets, and storm drains on their web site at http://www.udfcdmhfd.org/
1) StreetsTheStreets The allowable gutter flow in streets shall not exceed the values given in
Figure 6 – Street Flows – Allowable Capacities.
The allowable flows shown in Figure 6 were obtained using the Modified Manning’s Formula,
limiting the depth of flow for in the streets for storm runoff by the criteria in Table 11 – Allowable
Street Inundation, and then applying the reduction factors shown in Figure 7 – Reduction Factors
for Allowable Gutter Capacity; these factors limit flow velocities and account for reductions due
to parked and moving vehicles that obstruct flows.
If the Design Engineer encounters street cross slopes that are not 2 percent, then allowable flow
can be calculated using the methods in the USDCM (Volume 1).
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Table 11 – Allowable Street Inundation
Initial Storm Runoff – 2- Year Storm
Street Classification Maximum Encroachment
Local
Collector
Arterial
No curb overtopping. Flow may spread to crown of street.
No curb overtopping. Flow must leave at least one 10’
wide lane free of water.
No curb overtopping. Flow spread must leave at least one
10’ wide lane free of water in each direction.
Major Storm Runoff – 100 Year Storm
Street Classification Maximum Encroachment
Local and Collectors with
Mountable Curbs
Local and Collectors with
Vertical Curbs
Arterials
The depth of water over the gutter flowline shall not exceed
7.5 inches.*
The depth of water over the gutter flowline shall not exceed
9.5 inches.*
Depth of water shall not exceed 6 inches at the street
crown, in order to allow operation of emergency vehicles,
and not exceed 9.5 inches at the gutter flowline, whichever
is more restrictive.*
*Residential, public, commercial, and industrial development occurred prior to street
improvements in most areas of Englewood. Streets were built to best-fit existing improvements.
Therefore finish floor elevations are not necessarily elevated above the back of walk.
2) Inlets
The standard inlets permitted for use in the City are:
Table 12 – Standard Inlets Permitted
Inlet Type Standard Detail Permitted Use
Curb Opening Type R Curb Inlet D-9 All Street Types
Grated Type C Inlet D10 Medians and Detention Ponds
where vehicle and pedestrian
traffic is not permitted.
Grated Type 16 Inlet Grate and Frame
Detail
D-1 Alleys and Private Drives and
Streets
Grated Type 13 InletGrate and Frame
Details
D-5 Landscaped Areas and Detention
Ponds
Single Type 13 Inlet D-6 Landscaped Areas and Detention
Ponds
CombinationSingle Type 16 Open
Throat Inlet Adjustable Curb Box
D-2 All Street Types
3) Storm Drains
The hydraulic analysis of storm sewer systems shall be in accordance with the criteria presented in
the USDCM, Volume 1 – Streets, Inlets, and Storm Sewers. Final grades, street geometries, types
of construction, and all other street details relative to the design, construction, or operation of the
storm sewer system must be approved by the UtilitiesPublic Works Director.
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The design of the storm sewer system shall include hydraulic analysis of both the minor and the
major storm events. The hydraulic grade line (HGL) shall be calculated by accounting for pipe
friction losses, expansion, contraction, bend, and junction losses. The methods for estimating these
losses are provided in USDCM (Volume 1 – Storm SewersDrain Systems). The HGL shall be
plotted for all storm sewers. The HGL shall not be higher than 6-inches below the gutter flowline.
When the hydraulic grade line cannot meet the 6-inch criteria then the capacity of the storm sewer
will need to be improved by increasing pipe sizes.
Storm drain velocities shall be as shown in Table 15.
Table 15 – Storm Drain Velocity Criteria
Initial Storm Major Storm
Minimum Velocity
Maximum Velocity
3.0 fps
16.0 fps
N/A
20.0 fps
a) Construction Materials: Storm drains shall be constructed of reinforced concrete
(Class III is the required minimum) meeting current CDOT Specifications. The
systems shall be designed to handle anticipated loads. Other types of pipe material
and sizes may be acceptable on private property, but the owner will be responsible for
it. The Utilities Public Works Department may allow alternative pipe materials, if
justified. In such a situation a variance must be requested and approved by the
Department of Utilities staff
b) Minimum Pipe Diameter: The minimum pipe diameter of storm drains shall be 15
inches.
c) Horizontal Alignment: Storm drains shall usually be straight between manholes.
Long radius curves are permitted for pipe diameters equal or larger than 24 inches.
The radius of curvature shall be no less than the radius associated with the maximum
permissible joint deflection specified by the manufacturer and no less than 100 feet.
Storm drains shall be no closer than 5 feet, measured horizontally from the outside of
parallel sanitary sewer or water line to the outside of the storm drain. Storm drains
shall be no closer than 18 inches vertically from any crossing utility lines.
Spacing of manholes shall conform to Table 16. Manholes shall conform to Figure
14 –M-604-20 of the CDOT Standard Manhole Details.
Table 16– Manhole Spacing
Pipe Size Maximum Spacing
15 inches to 36 inches
42 inches or greater
400 feet
500 feet
500 e
t
The minimum width of easement for installation of a storm drain shall be the pipe
diameter plus 15 feet with the pipe normally centered in the easement.
d) Vertical Alignment: Whenever possible, the crowns of the inlet and exit pipe should
be aligned when the downstream pipe is larger than the upstream pipe within a
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manhole, in order to minimize backwater effects. The elevation drop through a
manhole shall be no less than 0.2 feet. Refer to USDCM (Volume 1) for guidelines
about shaping manhole bottoms and other details.
Storm drain grades shall be such that a minimum 18 inches cover over the crown of
the RCP is maintained. If less cover is shown, the Engineer shall submit the pipe
structural design to the Utilities Public Works Director for approval. Uniform slopes
shall be maintained between manholes. Final grades shall be set with full
consideration to capacity required, sedimentation problems, and other design
parameters. The minimum slope shall be capable of producing a velocity of 3 feet
per second when the drain is conveying initial storm flows.
When an existing culvert is to be extended and the grade changes, a concrete collar as
shown in Figure 15Detail D-16 – Concrete Pipe Collar Detail of the City Design and
Construction Standards and Specifications shall be used.
e) Storm Drain Outlets: Erosion protection shall be provided at the outlet in accordance
with the criteria presented in the Hydraulic Structures chapter of the USDCM
(Volume 2). All storm drain outlets into open channels shall be constructed with a
headwall and wing walls or a flared end section and toewall.
5.4 CULVERTS AND BRIDGES
The hydraulic design of culverts bridges in Englewood shall be in accordance with the Culverts and
Bridges chapter of the USDCM (Volume 2). Culverts are to be sized so that in the 2-year storm a
minimum cleansing velocity of 3 fps is provided. The major storm design criteria are governed by the
allowable street inundation as provided in Table 11. Culverts at a minimum shall be sized to convey
the 5-year storm without overtopping and convey the difference between the 100-year storm and the
allowable street overtopping, whichever is larger. Private driveway crossings over roadside ditches are
required at a minimum to convey the 2-year storm.
All culverts shall be designed with headwalls and wing walls, or with flared end sections and toewalls
at the inlet and outlet.
Conduit materials acceptable for use in culvert construction shall be in accordance with the criteria for
storm drains, except for driveway culverts, which also allow corrugated metal pipe, and or HDPE pipe.
Driveway culverts shall be designed and installed to be resistant to damage from mowing equipment
and errant vehicles.
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SECTION 6.0
STORAGE
6.1 GENERAL
Detention basins constructed in the City shall be full spectrum detention facilities designed in
accordance with the Storage chapter of USDCD (Volume 2). The first stage of these facilities,
capturing and treating the water quality capture volume (WQCV), shall consist of extended detention
basins, retention ponds, constructed wetland ponds, bioretention, or sand filter basins designed in
accordance with USDCM (Volume 3).
Open detention basins are preferred over underground detention basins. However, underground
detention may be allowed on a case-by-case basis upon approval of the department through a variance
request procedure. The use of underground detention will be evaluated based on; land use and site
characteristics, operation and maintenance requirements and responsibilities, and other factors deemed
appropriate by City.
6.2 DETENTION CRITERIA
1) Landscaping Requirements
All detention basins shall be covered with a minimum of 6 inches topsoil and landscaped and/or
revegetated. Detention basins when properly landscaped can be an attractive part of a development.
2) Maintenance
The Owner and subsequent owners, heirs, successors, and assigns shall maintain Stormwater
detention ponds. in accordance with the approved plan. In the event that the maintenance is not
performed by said owner, the City of Englewood shall have the right to enter such area(s) and
perform the necessary work, the cost of which said owner, heirs, successors, will be responsible for
paying upon billing. Detention facilities shall be designed so that they are accessible to
maintenance equipment as well as for removal of silt and debris and for repairs that may need to
occur.
3) Drainage Plan Detention Facility Notes
The following notes shall be included on the “Drainage Plan Sheets” for detention facilities.
a) Detention basin embankment shall have a minimum relative compaction of 95% at optimum
moisture content of standard proctor. or as recommended by a geotechnical engineer,
whichever is more restrictive. Provisions shall be made for watering of all native seeded areas
until it is established to 80% coverage.
b) The detention basin embankment top and spillway crest shall be stakedsurveyed by the
Developer to confirm that design grades are achieved prior to topsoil placement and
landscaping.
c) The detention facility volumes and all related drainage appurtenances (including basin
boundaries) shall be determined and confirmed by a registered professional engineer prior to
issuance of the certificate of occupancy for any structure on the site or in the Development.
d) No building or structure will be constructed in the detention areas and no changes or alterations
affecting the hydraulic characteristics of the detention areas will be made without the approval
of the Utilities Public Works Director.
e) Maintenance and operation of the detention areas will remain the responsibility of the property
owner, if the property owner fails in this responsibility the City has the right to enter the
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property, maintain the detention areas, and require reimbursement for the costs that may be
incurred.
4) Plat Detention Facility Notes
a) The following notes shall be included on plats when stormwater detention basin areas are
required:
i. The storm water detention area(s) shown hereon shall be constructed and maintained by
the owner and subsequent owners, heirs, successors, and assigns. In the event that said
construction and maintenance is not performed by said owner, the City of Englewood shall
have the right to enter such area(s) and perform the necessary work, the cost of which said
owner, heirs, successors, and assigns agrees to pay upon billing.
ii. No building or structure will be constructed in the detention area(s) and no changes or
alterations affecting the hydraulic characteristics of the detention area(s) will be made
without the approval of the Utilities Public Works Director.
b) For public stormwater detention or drainage easements, the following notes shall be included
on the face of the plat:
i. The storm water detention / (drainage easement(s)) shown hereon are hereby granted to the
City. This (these) easement(s) is (are) being conveyed for the purposes of operation, repair,
alteration, and maintenance of the storm water management system. The maintenance and
operation of the said facility (facilities) shall be the responsibility of the City providing the
design, construction, and maintenance criteria of the City are followed and the said facility
(facilities) has (have) been accepted. The City has the right to enter the property for the
purposes for which this (these) easement(s) has (have) been granted.
ii. No buildings, fills, excavations, structures, fences, or other alterations shall be constructed
within a storm water detention (retention) / (drainage easement(s)) without the express
written consent of the Utilities Public Works Director.
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Appendix D
February 2025
Firm:Engineer:
Phone:e-mail:
This form shall be used for the development and/or redevelopment of
infill lots that are less than 0.5 acre in size. Attach any additional
information as required.
SMALL LOT DEVELOPMENT FORM
Existing Drainage Pattern: Address flows, direction of flows, concentrated vs. sheet flows, where do flows go,
any offsite flows, irrigation ditches, existing drainage structures, and flood plain or flood hazard issues.
Proposed Drainage Pattern: Describe any proposed changes to the existing pattern or drainage system.
City of Englewood
Department of Utilities
1000 Englewood Parkway
Englewood, CO 80110
303.762.2635
www.englewoodco.gov
Site Description: Address existing conditions such as topography, present land use, existing structures, and
pavement areas.
Proposed Project Description: Address any and all proposed changes and land use.
Preparer:
Project Identification:
Subdivision Name:
Site Address:
Cover Page
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Appendix D
February 2025
Weighted Impervious Calculations
Existing Site
Impervious Areas
Roof Areas 90%
Paved Areas 100%
Other:
Pervious Areas
Gravel Areas 40%
Native Areas 5%
Grass Landscape Areas 25%
Other:
Sum B Sum C
Existing Imperviousness (Sum C/Sum B)
Developed Site
Impervious Areas
Roof Areas 90%
Paved Areas 100%
Other:
Pervious Areas
Gravel Areas 40%
Native Areas 5%
Grass Landscape Areas 25%
Others:
Sum B Sum C
Developed Imperviousness (Sum C/Sum B)
Site Plan Provided:
Scale North Arrow Proposed Site Improvements
Easements Ex Utilities Benchmark
Drainage Flow Arrows Property Lines
Ex & Proposed Contours Adjacent Streets
Best Management Practices Plan: Evaluate the possible pollution sources that are common for the proposed type of
development and indicate the controls recommended to mitigate adverse impacts.
Development Impact Analysis: Address the beneficial and detrimental impacts that the proposed
development/redevelopment will have.
A
Percent Impervious (%)
B
Existing Area (sf)
C = A x B
Existing Imperviousness
A
Percent Impervious (%)
B
Developed Area (sf)
C = A x B
Developed Imperv
Calculations Sheet
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Created: 2023-12-03 12:44:20 [EST]
(Supp. No. 60)
Page 1 of 2
12-5-9: Prohibited Discharges.
A. It shall be unlawful for any person to discharge or cause to be discharged to the storm drainage
system any polluting material or any other material which is not composed entirely of storm water.
B. It shall be complete defense to the application of this section that such discharge was made
pursuant to an "NPDES" storm water discharge permit or resulted from firefighting activities.
C. Except as such may be identified by the City as sources of polluting materials, this section shall not
apply to the following categories of non-storm-water discharges:
1. Water line and fire hydrant flushing;
2. Water-based fire suppression system testing;
3. Landscape irrigation;
4. Diverted stream flows;
5. Rising ground waters;
6. Uncontaminated ground water infiltration into the storm drainage system;
7. Uncontaminated pumped ground water;
8. Discharges from potable water sources;
9. Foundation drains;
10. Air conditioning condensation;
11. Irrigation water;
12. Springs;
13. Water from crawl space pumps;
14. Footing drains;
15. Lawn watering;
16. Individual residential car washing;
17. Flows from riparian habitats and wetlands;
18. Dechlorinated swimming pool discharges; and
19. Street washwater.
20. Discharges in accordance with the CDPHE low risk discharge policy guidance documents or
other policy and guidance documents of the State.
D. Any person who violates any provision of this section shall be subject to a civil penalty of not more
that nine hundred ninety-nine dollars ($999.00) per day during which such violation occurs or
continues, or, upon conviction, a criminal penalty punishable by a fine of not more than nine
hundred ninety-nine dollars ($999.00) per day during which such violation occurs or continues or
by imprisonment for not more than three (3) months or by both.
(Code 1985, § 12-5-9; Ord. 66-12, § 1)
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(Supp. No. 60)
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