HomeMy WebLinkAbout8703RESOLUTION NO. 8703
A RESOLUTION ADOPTING AND APPROVING SANITARY SEWER DESIGN CRITERIA AND POLICIES
FOR THE CITY OF PUEBLO DATED MAY 12, 1999 AND REPEALING RESOLUTION NO. 7379
BE IT RESOLVED BY THE CITY COUNCIL OF PUEBLO, COLORADO, that:
SECTION 1.
Pursuant to and in furtherance of sections 4- 2 -2(i), 12- 4 -2(7), 12 -4 -5, 12- 4- 6(b)(3)b. and 12-4-
70)(5)b. of the Pueblo Municipal Code and upon recommendation by the Wastewater Engineer, the Council
does hereby adopt and approve as minimum sanitary sewer standards the Sanitary Sewer Design Criteria
and Policies for City of Pueblo, Colorado, published May 12, 1999 by the Department of Wastewater, 211
East "D" Street, Pueblo, Colorado, a true copy of which is attached hereto and made a part hereof by
reference (hereinafter referred to as the "Sanitary Sewer Criteria "). The Council declares that the design
and construction of sanitary sewer facilities within the City for all subdivisions ( and resubdivisions)
approved by the City Council after date of approval of this Resolution shall be performed and installed in
conformance with said Sanitary Sewer Criteria and all other provisions of Title 12 of the Pueblo Municipal
Code.
SECTION 2.
Except as modified by this Resolution, all minimum sanitary sewer design standards heretofore
adopted shall remain in full force and effect and be applicable to all subdivisions approved prior to the date
of approval of this Resolution.
SECTION 3.
After adoption of this Resolution, a true copy of the Sanitary Sewer Criteriashall be maintained on
file in the office of the City Clerk for public inspection. Copies of the Sanitary Sewer Criteria shall be made
available through the City's Department of Wastewater for purchase by the public at a moderate price.
SECTION 4.
Resolution No. 7379 is hereby repealed.
INTRODUCED May 24, 1999
BY Cathy A. Garcia
Councilperson
APPROVED: I D6ll�—
President of the Council
ATTEST:
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Title: A RESOLUTION ADOPTING AND APPROVING Agenda Item #
SANITARY SEWER DESIGN CRITERIA AND
POLICIES FOR THE CITY OF PUEBLO DATED
MAY 12, 1999 AND REPEALING RESOLUTION
NO. 7379
Department: WASTEWATER DEPARTMENT Date: MAY 24, 1999
ISSUE
Should the City Council approve a Resolution adopting and approving Sanitary Sewer
Design Criteria and Policies for the City of Pueblo dated May 12, 1999 and repeal
Resolution No. 7379.
RECOMMENDATION
Approval of the Resolution.
BACKGROUND
Over the years the City of Pueblo - Wastewater Department has developed design
criteria and general policies related to sanitary sewers. The criteria and policies have
been in the form of letters, guidance documents and resolutions. The proposed
Sanitary Sewer Design Criteria and Policies manual consolidates all of the sanitary
sewer information into one manual. The manual is the result of existing information as
well as input from the City's legal staff, the Homebuilders Association, developers and
private consulting engineers doing work within the City.
Also, In 1994 City Council adopted Sanitary Sewer - General Policies (Resolution No.
7379) in conjunction with the then newly adopted sanitary sewer connection fees. The
resolution laid out policies and guidelines for the development of the sanitary sewer
collection system. The proposed Criteria Manual incorporates the policies in the
resolution with some minor modifications. Therefore, the resolution needs to be
repealed.
FINANCIAL IMPACT
None
NIXON Im . I I I
DEPARTMENT OF WASTEWATER
211 E AST "D" STRE
PUE COLORADO 81003
TELEPHONE: (7119) 544-3453
FAX NO. o f719) 542 -6244
MAY 112, 1999
TABLE OF CONTENTS
CITY OF PUEBLO, COLORADO
SANITARY SEWER DESIGN CRITERIA
AND POLICIES
CHAPTER 1. GENERAL PROVISIONS
1.1 Jurisdiction
1.2 Purpose and Intent
1.3 Definitions
1.4 Modifications
1.5 Relationship to Other Standards
1.6 Permits and Other Requirements
1.7 Liability
1.8 Private Sewers and Private Pump Stations
CHAPTER 2. SANITARY SEWER PLANNING CRITERIA
2.1 General Policies
2.2 Design /Planning Period
2.3 Population and Land Use Projections
2.4 Sanitary Sewer Flow Computation Criteria
2.5 Wastewater Pumping Stations
CHAPTER 3. PROCEDURES /SUBMITTALS FOR SUBDIVISIONS AND
MASTER DEVELOPMENT PLANS
3.1 Subdivisions
3.2 Master Development Plans
CHAPTER 4. DESIGN CRITERIA
4.1
Datum
4.2
Bench Marks
4.3
Depth of Sewers
4.4
Location and Alignment
4.5
Multiple Pipes in a Single Trench
4.6
Pipe Materials
4.7
Hydraulic Design
4.8 Manholes, Junction Structures, and Cleanouts
4.9 Pump Stations and Force Mains
4.10 Inverted Siphons
4.11 Stub -Ends of Lines
4.12 Stream and Drainage Crossings
4.13 Railway and Highway Crossings
4.14 Hydrogen Sulfide Production
CHAPTER 5. OPERATION & MAINTENANCE OF SEWERS
5.1 Public Sewers
5.2 Private Sewers
LIST OF REFERENCES
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SANITARY SEWER DESIGN CRITERIA
AND POLICIES MANUAL
FOR THE
CITY OF PUEBLO
CHAPTER 1. GENERAL PROVISIONS
1.1 JURISDICTION
All of the policies and design criteria set forth in this manual are adopted pursuant to the
authority of Sections 4- 2 -2(i), 12- 4 -2(7), 12 -4 -5, 12- 4- 6(b)(3)(b) of the Pueblo Municipal
Code, as amended, and shall apply to all land within the incorporated areas of the City, and
all facilities constructed on City right -of -way (ROW), easements dedicated for public use, and
to all privately owned and maintained sanitary sewer facilities.
1.2 PURPOSE AND INTENT
These regulations are adopted for the purposes of assuring safe, efficient operation of the
wastewater system and are intended to prevent wastewater discharges to the system in
concentrations or quantities which have the potential to harm or adversely affect the
wastewater system, wastewater treatment process or equipment, or any receiving water.
These regulations are adopted generally for the purpose of promoting public health and safety
and preventing the occurrence of nuisance conditions. These regulations are not intended, nor
should they be construed, to create any new rights, remedies, or benefits for any person, firm,
corporation or entity.
All Master Development Plans, Subdivisions, Resubdivisions, Planned Unit Developments,
Special Area Plans, or other proposed construction submitted for approval under the
provisions of Title 12, Chapter 4 of the Pueblo Municipal Code shall include provisions for
connection of such development to the City's sanitary sewer system, provisions to ensure
adequate sewerage collection, and also, shall comply with the sanitary sewer design criteria
and policies set forth in this manual. All designs, analyses, and reports shall be prepared
under the supervision of a Professional Engineer (Engineer), licensed as such in the State of
Colorado.
1.3 DEFINITIONS
"Backbone System" means that system of major wastewater collection interceptor sewer
mains, typically including those greater than 12 inches in diameter (unless otherwise identified
by the City), in addition to the wastewater treatment facilities.
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"Branch Sewer" means a sewer that receives wastewater from a relatively small area and
discharges into a trunk sewer serving more than one branch -sewer area.
"Building Drain" means that part of the lowest piping of a drainage system which receives the
discharge from soil, waste, and other drainage pipes inside the walls of the building and
conveys it to the building sewer beginning two (2) feet outside the building wall.
"Building Sewer" or "Service Line" means that part of the horizontal piping of a drainage
system which extends from the end of the building drain and which receives the discharge of
the building drain and conveys it to a public sewer, private sewer, individual sewage disposal
system, or other point of disposal.
"Collector Sewer" means a sewer located in the public way which collects the wastewater
discharged through building sewers and conducts such flows into larger interceptor sewers and
pumping and treatment works.
"Concrete Arch" is a bedding method as follows: The pipe is embedded in a compacted
granular material having a minimum thickness of 1 /4 the outside diameter or 4 inches minimum
between barrel and bottom of trench excavation and extending half way up the sides of the
pipe. The top half of the pipe is covered with reinforced concrete arch having a minimum
thickness of 1 /a of the outside diameter or 4 inches minimum measured at the crown of the pipe
and having a minimum width equal to the outside pipe diameter plus 8 inches.
"Depth of Sewer" means the vertical distance from the ground surface over the sewer to the
top of the sewer pipe.
"Developer" means an owner or owners of one or more parcels of property intending to
undertake a development of same.
"Development" means the entire development within the Property Master Plan (PMP)
Individual subdivisions within the PMP are considered phasing of the development.
"Director of Public Works" is the manager of the Department of Public Works, or a
designated representative.
"Infiltration" is groundwater flow entering the sewer system, seeping in through defective pipe
joints and cracks in manholes and sewer pipe. Infiltration does not include, and is
distinguished from, inflow.
"Inflow" is flow entering the sewer system in the form of direct connections such as roof and
area drains. Inflow does not include, and is distinguished from, infiltration.
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"Intercepting Sewer" means a sewer that receives flow from a number of transverse sewers
or outlets and conducts such waters to a point for treatment or disposal.
"Inverted siphon" is a depressed sewer that drops below the hydraulic gradient to avoid an
obstruction such as a stream or drainage way.
"I &I" means any combination of infiltration and inflow, without regard to the source(s).
"Master Development Plan" means a plan prepared in accordance with the requirements of
Section 12- 4 -6(a) of the Pueblo Municipal Code.
"Non uniform flow" means a flow regime where the water surface varies non - uniformly over
a horizontal distance due to a change in pipe size or grade.
"Off -site sewer collection system improvements" means sewer collection system
improvements required to be constructed outside the boundaries of the property which is the
subject of the development, and which, in addition to serving all foreseeable needs of the
property which is the subject of the development, is also specifically intended and designed
to be capable of providing sewer service to property other than the subject of the development.
"Outfall Sewer" means a sewer that receives wastewater from a collection systems or from
a treatment plant and carries it to a point of final discharge.
"Peak flow" is the peak hourly flow.
"PMP" means a Property Master Plan which consists of Land Use Plan, Drainage Plan,
Sanitary Sewer Master Plan, and Transportation Plan as required by the City of Pueblo
Annexation Master Plan.
"Private Sewer" means a building sewer which receives the discharge from more than one (1)
building drain and conveys it to a public sewer, private sewage disposal system or other point
of disposal.
"Public or Public Use" means all buildings or structures that are not defined as private or
private use.
"Public Sewer" means a common sewer directly controlled by the City of Pueblo.
"Pueblo Municipal Code" means Charter and Code of the City of Pueblo, Colorado.
"Relief Sewer" means (a) a sewer built to carry the flows in excess of the capacity of an
existing sewer, (b) a sewer intended to carry a portion of the flow from a district in which the
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existing sewers are of insufficient capacity, and thus prevent overtaxing the latter, or (c)
replacement of the existing sewer in place with a larger sewer main.
"Sanitary Sewer" means a sewer that carries liquid and water - carried wastes from residences,
commercial buildings, industrial plants, and institutions, together with minor quantities of
storm, surface, and groundwaters that are not admitted intentionally.
"Sanitary Sewer System" means the collective public sewer system and treatment facilities.
"Service Stub" means a portion of a future building sewer running from the sewer main to
approximately the property line.
"Sewer" means a pipe or conduit that carries wastewater or drainage water.
"Sewer Main" or "Collection Line" means any portion of the wastewater treatment system
which collects and transmits wastewater from the outfall of building sewers to the wastewater
treatment plant, excluding service lines.
"Shallow Sanitary Sewer Service" means any sewer service too shallow to accommodate a
basement by means of gravity flow.
"Standard Construction Specifications and Standard Details for the City of Pueblo, Colorado"
means the manual developed by the City of Pueblo's Department of Public Works related to
construction specifications and standard details, dated June 9, 1997 and as same may be
amended.
"Trunk Sewer" means the principal sewer to which branch sewers are tributary. In plumbing,
the public sewer to which a building sewer is connected.
"Wastewater" means the spent water of a community. From the standpoint of source, it may
be a combination of the liquid and water - carried waste from residences, commercial buildings,
industrial plants, and institutions, together with any groundwater, surface water, and
stormwater that may be present. Formerly referred to as sewage.
1.4 MODIFICATIONS
To the extent applicable, requests for modifications to the design standards and criteria set
forth herein shall be submitted in accordance with Section 12 -4 -10 of the Pueblo Municipal
Code, or as same may be amended. .
1.5 RELATIONSHIP TO OTHER STANDARDS
Included in this manual are approved design methods, charts and tables, which when used will
enable the City to perform its review in a more efficient and expeditious manner. If the
Developer and /or land owner prefers to use other methods, charts or tables, prior approval
shall be obtained from the Director of Public Works before submittal.
1.6 PERMITS AND OTHER REQUIREMENTS
The Developer and /or land owner shall be required to obtain all permits required by Federal,
State, or Local Agencies in conjunction with work covered under this manual, and shall be
required to comply with requirements which may be imposed directly by such agencies or
which may be indirectly necessitated in order for the City to comply with any permit which
may be issued to the City.
1.7 LIABILITY
The adoption of this manual shall not create any duty to any person, firm, corporation, or
other entity with regard to the application, enforcement or nonenforcement of this manual.
No person, firm, corporation, or other entity shall have a private right of action, claim or civil
liability remedy against the City of Pueblo, or its officers, employees or agents, for any
damage arising out of or in any way connected with the adoption, application, enforcement,
or nonenforcement of this manual. Nothing in this manual shall be construed to create any
liability under, or to waive any of the immunities, limitations on liability, or other provisions
of, the Governmental Immunity Act, C.R.S. 24 -10 -101 et. seq., or to waive any immunities
or limitations on liability otherwise available to the City of Pueblo or its officers, employees
or agents.
Review and approval by the City of sanitary sewer improvements proposed in submittals does
not relieve the engineer who designed such improvements from his professional
responsibilities for the adequacy of the design of said improvements.
1.8 PRIVATE SEWERS AND PRIVATE PUMP STATIONS
Any sanitary sewer system that is extended into private roads or private property shall be
considered private unless otherwise approved by the City. Private sewers and pump stations
are intended to serve only site specific developments, (i.e., shopping centers, special area
plans, etc.) and shall not serve any area beyond the development or become part of the
Sanitary Sewer System.
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CHAPTER 2. SANITARY SEWER PLANNING CRITERIA
2.1 GENERAL POLICIES
General policies and guidelines will be followed in order to develop a Sanitary Sewer System
that will accommodate current and future needs of the City. The following addresses the
major issues related to the development of the City's Sanitary Sewer System.
The purpose of the provisions contained herein are to provide sound engineering and long -
range planning in the extension of the City's Sanitary Sewer System and promote the orderly
development of the City's Sanitary Sewer System.
2. 1.1 Development Policy
A. All Development within the City shall require connection to the City's Sanitary
Sewer System.
B. Developer is responsible for the cost and construction of the Sanitary Sewer
System required to serve the entire development in accordance with the
Property Master Plan (PMP). The Sanitary Sewer System shall include, but is
not limited to: manholes, sewer mains, service lines, pumping stations, force
mains, and all necessary appurtenances.
C. The Sanitary Sewer System within the development is required to be sized to
the ultimate capacity of that portion of the sub -basin area which will discharge
through the development, and to include a reasonable portion of sub -basin area
upstream of the development, as determined by the City based upon present and
future development of property within the sub -basin area.
D. If a larger sanitary sewer system (including pumping systems) is required to
serve a sub -basin area as described in 2.1. LB. than is required to serve a
particular development, the Developer will be responsible for installing the
larger system. In such event, the Developer may be eligible for reimbursement
for a portion of the larger system within the developed area.
Any reimbursement to the Developer for oversizing the Sanitary Sewer System
not required to serve the Development will be based on the following:
1. Reimbursement related to oversizing the collection system shall only be
considered for sewer mains larger than twelve (12) inches.
Reimbursement costs shall be the difference in the cost of pipe between
twelve (12) inches and the actual size installed, if the size required to
serve the development is twelve (12) inches or smaller. If the size of the
Sanitary Sewer System that is required to serve the development is larger
than twelve (12) inches, the reimbursement will be the difference
between the cost of pipe between the size of pipe needed to serve the
development and the actual size installed.
2. Reimbursement related to oversizing pumping systems shall be the cost
of oversizing, based upon information and data submitted by the
Developer and approved by the City of Pueblo.
E. Branch lines (typically 8" - 10 ") and Trunk lines (typically 10" - 12 ") are not
part of the Backbone System. Proposed developments will not be allowed to
connect to the existing Branch or Trunk lines unless adequate capacity is
available to accommodate the proposed development. If capacity is available,
connection to a Branch or Trunk Line shall be approved by the Director of
Public Works. If there is insufficient capacity in the Branch Line or Trunk
Line, the Developer shall extend the sanitary system in accordance with Section
2.1.2. As an option, the Developer may upgrade the existing Branch or Trunk
Lines as approved by the Director of Public Works and consistent with the
intent of the City's Master Sewer Plan.
F. Developments shall discharge to the Sanitary Sewer System(s) within the basin
and at a point or points as identified in the City's Master Sewer Plan. In no
case will proposed development(s) be allowed to discharge outside of its
identified basin boundary unless otherwise approved by the City. However,
Master Sewer Plans can be revised upon approval by the City.
2.1.2 Main Extension Policy
The main extension policy addresses the responsibility of extending the Sanitary Sewer System
and allows for equitable reimbursement for said extensions.
A. The Developer shall be responsible for extending the Sanitary Sewer System
from its connection to the Public Sewer to the exterior boundaries of the
development including oversizing the sewer main extension, in accordance with
the approved Sanitary Sewer Master Plan. If a Sanitary Sewer Master Plan has
not been approved for the area, such extension shall be in accordance with the
preliminary Sanitary Sewer Master Plan developed by the City.
B. The Sanitary Sewer System shall be sized to the ultimate capacity as described
in Section 2.1.1.13 and extended to the exterior boundaries of each subdivision
within the development.
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C. If the Developer has cause to extend the sanitary sewer main(s) or related
facilities from outside the proposed development, (off -site sewer collection
system improvements) the Developer is eligible for recovery of some of the
costs for said off -site improvements and oversizing in accordance with Chapter
5, Title XVI of the Pueblo Municipal Code, or as same may be amended.
2.1.3 Relief Sewer Policy
If a proposed development cannot be served by the Backbone System (interceptors and
outfalls) existing within the area, a new relief sewer shall be constructed in accordance with
the approved Sanitary Sewer Master Plan. If a Sanitary Sewer Master Plan has not been
approved for the area, such relief sewer shall be constructed in accordance with the
preliminary Sanitary Sewer Master Plan developed by the City. It is the intention of the City
to install or have installed, necessary and required relief sewers to mitigate impacts on the
City's existing backbone Sanitary Sewer System, to the extent City funds therefore are made
available by resolution of the City Council pursuant to Section 16 -11 -4 of the Pueblo
Municipal Code, or as same may be amended.
2.1.4 Street or Allev Vacations
Streets or alleys that have active sanitary sewer mains in them will not be considered for
vacation unless the sewer can be abandoned as a public sewer and it will not be used to serve
future development or expansions upstream of the abandoned sewer. At such time a public
right -of -way is vacated and a public sewer abandoned but continues to function as a private
sewer main, provisions shall be made for the maintenance and repair of the private sewer (i.e.
covenants and /or agreements).
2.2 DESIGN /PLANNING PERIOD
All improvements to the sanitary system shall be planned, designed, and constructed to
provide adequate service for a useful life of 50 years unless a longer or shorter useful life
period is stipulated or allowed by the Director of Public Works.
When allowed or stipulated by the Director of Public Works, construction of proposed
improvements may be phased over a period of time (e.g., the pumping capacity of a lift station
may be phased to match development rather than initially set at the future rate).
2.3 POPULATION AND LAND USE PROJECTIONS
All improvements to the Sanitary Sewer System shall be planned and designed to provide
adequate service as specified by the following:
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2.3. 1. Planning Criteria for Sanitary Sewers
A. The area dedicated to each separate land use, calculated in acres, (such as
single - family, multi- family, commercial, and industrial) shall be determined
based upon the Master Development Plan.
B. Sanitary sewer impact shall be computed for the entire sewer drainage basin
including the proposed development. Mains shall be designed to adequately
accommodate the area as per criteria contained herein.
C. Additional information is included in the City of Pueblo Annexation Master
Plan, (City of Pueblo Department of Planning and Development).
2.4 SANITARY SEWER FLOW COMPUTATION CRITERIA
2.4.1 Flow Factors
A summary of average and peak flow factors are summarized in the following table:
TABLE 2.1— SANITARY SEWER FLOW COMPUTATION CRITERIA FLOW FACTORS
Land Use
Average Flow
"Per Acre" (1)
Peak
Factor
Peak Flow
"Per Acre" (1)
CFS
MGD
CFS
MGD
Single- Family Residential
0.0016
0.0010
2.6
0.0042
0.0027
Multiple- Family Residential
0.0003
per unit
0.0002
per unit
2.6
0.0009
per unit
0.0006
per unit
Commercial
0.0015
0.0010
2.6
0.0040
0.0026
Industrial
0.0020
0.0013
2.6
0.0051
0.0033
High -Water Consuming
Industries
Special Study Required
Institutional Use
Special Study Required
Areas Outside The
Development Plan(Unplanned)
0.0017
0.0011
2.6
0.0044
0.0028
(1) Unless otherwise stated
2.4.2 Infiltration and Inflow
Identify and design for areas with a high potential for groundwater infiltration. Maximum
allowable infiltration/ inflow (1 /I) shall be in accordance with Article 12- Specifications for
Sanitary Sewers. Use 0.0003 cfs per acre for newly developed basins with low potential for
infiltration problems due to groundwater. Areas with high potential for groundwater
infiltration shall be determined by the City or by studies done for the area.
2.5 WASTEWATER PUMPING STATIONS
Wastewater pumping stations will only be employed when gravity flow is not feasible;
otherwise, pump stations will not be afforded planning consideration. The Engineer shall meet
with the City prior to preparing the Engineering Report for a pumping station.
2.5.1 Engineering Report
If a pumping station is to be considered, a detailed engineering report shall be submitted to
the Department of Public Works and shall include the following:
A. A brief description of the project and purpose.
B. A pumping station "feasibility study" which provides justification.
C. The engineering report shall elaborate on the following for both present and
future conditions:
1. Design period
2. Population densities per acre and total population
3. Acres of area(s) served (including a map of the area(s) to be served)
4. Per capita wastewater contribution - average and maximum, (per Table
2.1)
5. Infiltration
6. Commercial and Industrial waste contributions
7. Design flow rates - average and maximum
8. Strength (BOD and TSS) of wastewater and industrial waste
characteristics
D. The report shall also address the following for both initial and future conditions:
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1. Number, type, capacity, motor horsepower, phasing, voltage, and net
positive suction head (NPSH) requirements of proposed pumping units.
2. System head curve (including head computations) for the pumping
system
3. System head calculations shall include the size and length of force main
and assumed C (Friction) factor.
4. Wastewater detention time in the wet well and force main.
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CHAPTER 3. PROCEDURES /SUBMITTALS FOR
SUBDIVISIONS AND MASTER DEVELOPMENT PLANS
3.1 SUBDIVISIONS
3.1.1 General
Procedures and submittals for subdivisions shall be in accordance with all City of Pueblo
Ordinances, policies, and as same may hereafter be amended.
3.1.2 Initial Subdivision Submittal
This applies to subdivision plats for "conditional" plat approval which allows for the deferral
of certain plans and other documents for up to one year from the date of "conditional" plat
approval. Sanitary sewer information required for this submittal consists of a preliminary
utility plan showing the proposed utility layout for the subdivision. This plan must show the
sanitary sewer along with storm sewer and water lines in plan view only. Design details such
as manhole locations and pipe sizes are not required on the preliminary utility plan. Sanitary
sewer and water service lines for each lot must also be shown either individually or by a
typical detail.
Care should be taken by the Engineer in regard to the topography of the site to ensure that the
utility plan is feasible. Changes to the utility plan may cause plat changes that require re-
submittal.
3.1.3 Final Subdivision Submittal
Sanitary sewer information required for this submittal shall include:
1. Complete construction plans of all sanitary sewer facilities along with all other
improvements required to serve the subdivision. The construction plans shall
include all required on -site and off -site improvements. A profile of the Private
Sewer Main may not be required if adequate information is provided on a
"Utility Plan." The plan shall include sufficient information to confirm
compliance with the design criteria and applicable City Ordinances.
2. Subdivision Improvements Agreement with exhibits "A" and "B" and
addendums (if any). All sanitary sewer facilities, public or private, which are
required to provide service to each lot within the subdivision shall be included
in exhibit "B ".
3. Covenants, on City approved forms, addressing maintenance responsibilities of
private sanitary sewers that serve more than one lot (to be recorded).
4. Easements, on City approved forms, for off -site sanitary sewer facilities.
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5. Easements for access to City maintained sanitary sewer facilities which are
outside of the public right -of -way, and design of access road, (if applicable).
6. Notice of shallow sanitary sewer service lines (if any) which identifies specific
lots affected (to be recorded).
3.2 MASTER DEVELOPMENT PLANS
3.2.1 Sanitary Sewer Report
The Petitioner shall prepare a Sanitary Sewer Report in accordance with criteria as follows:
The Report shall identify on a United States Geological Survey (USGS) Map - -Scale 1 to
24,000 - -the gravity drainage basin or basins incorporating the proposed site and the service
area boundary for the City's wastewater treatment plant.
The Report shall address the needs of the entire sewer drainage basin. This basin will be
designated by the Director of Public Works. The Report shall discuss and analyze areas
upstream of the site, within the gravity drainage basin, that would impact a trunk line or
interceptor within the site. The existing wastewater system and the impact on that system by
the proposed development shall also be addressed. The Sanitary Sewer Report shall provide
a plan for anticipated improvements.
All sanitary sewer reports shall be typed on 8.5" x 11" paper and neatly bound in a folder
which clearly identifies the development. A copy of the general location map and a master
sanitary sewer plan shall be included in a folder pocket at the back of the report.
The Report shall be transmitted with a cover letter prepared by the Professional Engineer
responsible for the preparation of the report, describing the project, noting any special
conditions or problems encountered on the site, certifying that the sanitary sewer report was
completed under his /her supervision in accordance with the City of Pueblo's sanitary sewer
design criteria and policies, and that the design is in conformance with the City approved
master plan for the basin, if one exists. The cover letter shall identify any modification to the
criteria that may be requested. The final report shall be signed and stamped by the
Professional Engineer responsible for the preparation of the report.
Two copies of the report are required upon submittal, one of which will be returned to the
Engineer with comments or approval. If corrections or changes are required for approval by
the City, two revised copies of the report, with all corrections or changes made, shall be
submitted to the City for approval. Incomplete reports will not be accepted for review.
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The Report shall include but not limited to:
1. Master Development Plan (Land Use Plan)
2. Tabulation of peak flows and preliminary pipe sizes.
3. Locations of all points on the City's existing sewer system where the new
system will connect.
4. Identification of hydraulic deficiencies in the system caused by the Development
(these deficiencies will have been identified by the City during an initial
meeting with the Developer).
5. A discussion of any pumping stations, force mains, packaged treatment plants,
and other special equipment as needed.
6. Any agreements that may be proposed.
3.2.2 Sanitary Sewer Report Criteria
The planning criteria presented in Chapter 2 and the design criteria presented in Chapter 4 will
provide guidelines for the planning and design of sanitary sewers. In unusual circumstances
or where special conditions dictate, certain deviations from the standard criteria may be
directed or approved by the Director of Public Works.
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CHAPTER 4. DESIGN CRITERIA
Design of both public and private sanitary sewers shall be in accordance with the following
minimum design standards and specifications (Article 12- Specifications for Sanitary Sewers)
of the City of Pueblo, Colorado:
4.1 DATUM
All vertical survey control for sewer design shall be based upon established City of Pueblo
bench marks.
4.2 BENCH MARKS
Each sewer project shall have its own vertical control circuit, and each bench mark in the
circuit shall be assigned the correct elevation in relation to all other bench marks in the circuit.
The closest bench mark to the proposed work shall be shown on each sewer profile sheet and
on each sewer plan sheet on which elevations are shown.
4.3 DEPTH OF SEWERS
In general, sewers shall be designed deep enough to drain basements and to prevent freezing.
No public mains shall be less than four (4) feet deep measured from the top of pipe unless
special protection is provided, (i.e. reinforced concrete encasement, reinforced concrete arch,
ductile iron pipe, etc.).
No building sewer /service line shall be less than four (4y feet deep in traffic areas without
similar special protection listed above except that concrete driveways may be substituted for
protection of service lines.
4.3.1 Service connections
In designing the minimum depth of public sewers, allowance must be made for the additional
depth required to accommodate gravity flows from building sewers and to accept the rise of
the service connection. Plat and construction plan notification, along with a separate
notice /document (to be recorded) is required for shallow sanitary sewer service lines.
4.4 LOCATION AND ALIGNMENT
All public sanitary sewer mains shall be placed within the paved portion of the street when
possible. Standard position for locating public sewers, unless some major interference
prevents such location, is five (5) feet off of the street centerline and along the centerline of
17
any sewer easement. The alignment in streets less than standard width shall be approved by
the Director of Public Works. Whenever a sanitary sewer is placed within an easement, the
sanitary sewer easement shall be a minimum of ten (10) feet wide on each side of the sewer
main. If the sanitary sewer is to share an easement with another utility additional width may
be required. If the sewer is deeper than normal, 12 feet or greater to the top of pipe, a wider
easement may be required. A wider easement may also be required due to unfavorable
subsurface conditions (i.e. sand, groundwater, etc.).
Manholes shall be located so as to prevent entry of storm water. Proposed sewer lines which
may conflict with the placement of other underground facilities will require prior approval of
the sewer placement location by the controlling agencies whose facilities are affected.
Locations other than those specified will also require specific approval of the Director of
Public Works.
Installation of curvilinear sewer mains in sizes 8 inches through 15 inches in diameter are
acceptable and may be necessary to obtain the standard location of sewer mains. Curvilinear
sewers must be designed and constructed using a uniform slope between manholes and the
curve of the pipe shall have a radius in accordance with the manufacturer's recommendations
or the minimum radius of curvature indicated in the table below. The necessary curvature
shall be attained by deflection at joints not to exceed the applicable manufacturers'
recommendations or by approved preformed joints or couplings. Sewer mains greater than
15 inches in diameter shall not be installed in a curvilinear alignment because they can be
cleaned using a bucket machine, unless otherwise approved by the City.
TABLE 4.1— MINIMUM PIPE RADIUS
Pipe Diameter (inches)
Minimum Radius of Curvature (feet)
8
200
10
250
12
300
15
375
Changes in alignment for service lines shall be accomplished with preformed bends /fittings
not to exceed 45'. When changes in direction exceed 45', a two foot section of pipe shall
be used to make the needed change of direction between fittings. Field bending of pipe
shall not be permitted.
4.4.1 Relation to Water Mains
Where sewer lines cross water mains or come within ten (10) horizontal feet of each other,
the sewer pipe shall be a minimum of 18 inches clear distance vertically below the water
HE
main. If this clear distance is not feasible, the pipe section must be designed and
constructed so as to protect the water main. Minimum protection shall consist of the
installation of an impervious and structural sewer. For example: at crossings,
a. One length of pipe at least 18 feet long centered over the water main. Joints
between the sewer pipe and the special length pipe shall be encased in a
concrete collar at least 6 inches either side of the joint;
b. Concrete encasement shall be at least 6 inches thick and extend a distance of
ten (10) feet either side of the water main.
In all cases, suitable backfill or other structural protection shall be provided to preclude
settling and /or failure of the higher pipe.
4.5 MULTIPLE PIPES IN A SINGLE TRENCH
Pipes shall not be installed one over the other in the same trench. Pipes adjacent to one
another with little difference in invert elevation may be laid in the same trench provided
the spacing between pipes is minimum of twelve (12) inches.
Pipes in close lateral proximity but at different elevations shall be installed as follows: the
deeper pipe shall be installed with standard trench method then backfilled to an elevation at
least one (1) foot higher than the top of the proposed higher pipe. The higher pipe shall be
installed using standard trench method, backfilled to the level of the backfill of the first
trench then final common backfill completed to the original or designed ground surface
elevation.
4.6 PIPE MATERIALS
Acceptable pipe materials are referenced in the Standard Construction Specifications and
Standard Details for City of Pueblo, Colorado under Article 12, Sanitary Sewers, Item
12.2 - Materials.
4.7 HYDRAULIC DESIGN
The size of pipe to be constructed as indicated on the plans will represent the inside or
nominal diameter of the pipe or sewer. No public sewer shall be less than 8 inches in
diameter. Privately owned branch sewers may be 6 inches in diameter, provided a six (6)
inch will accommodate the entire development.
Pipe size requirements shall be computed by using Manning's formula. The Manning
formula for circular pipes flowing full is:
19
8 1
Q= 0.00061 x d 3 x s 2
n
or
Q = VA
or
2 1
1.486
Q = R3 s2A
n
Where Q = Flow in cubic feet per second
V = Velocity in feet per second
n = Friction factor
d = Pipe diameter in inches
D = Pipe diameter in feet
A = Area of pipe in square feet
s = Pipe slope in feet per foot.
R = Hydraulic radius = area of pipe _ D in feet
wetted perimeter of pipe 4
The following coefficients of roughness, "n" shall be used in Manning's formula for the
computation of pipe capacity:
Table 4.2 - COEFFICIENTS OF ROUGHNESS
Type of Pipe
"n"
Vitrified Clay (VCP)
0.013
Polyvinyl Chloride (PVC)
0.010
Ductile Iron ( lined) (DIP)
0.010
20
Sewers shall be designed to flow at a maximum depth "d" of pipe inside diameter "D" at
peak discharge per the table below. Peak flows will be determined by applying a 2.6 peak
factor to the average design flow determined for the sewer.
Table 4.3 - DESIGN DEPTH OF FLOW
PIPE SIZE
DESIGN DEPTH OF FLOW (d /D)
6" private
0.50
8"
0.50
10"
0.50
12"
0.67
15"
0.70
18" and above
0.75
In all cases, a depth- variable friction factor shall be used for the final design. See attached
Figures 1 and 2 for depth- variable friction factors for circular pipes and PVC pipes. In
these figures, the following terms apply:
Q = Flow at depth "d ", pipe flowing partly full
Q = Flow with pipe flowing full
V = Velocity with flow at depth "d"
V f = Velocity with pipe flowing full
d = Depth of water in pipe, measured vertically along centerline of pipe
D = Pipe diameter, full flow depth
Figures 1 and 2 shall be used to determine the allowable contributing flow to a new sewer
based upon a known diameter and slope. For example, a new 10" PVC sewer is to be
constructed. The sewer slope is 3 feet per 1000 ft. The allowable depth of flow is 0.5,
thus d/D is 0.5. Using Figure 2, the hydraulic element Q /Q is 0.4 and V /V f . is 0.8.
Knowing that the Q is 1.56 cfs, then the allowable peak flow contribution by the
Developer to this sewer is 0.62 cfs (1.56 cfs x 0.4). With V of 2.86 ft /s, the 0.5 depth of
flow will have a velocity of 0.8 x 2.86 ft /sec or 2.29 ft /sec.
21
FINAL DESIGN
Size of Pipe:
Type of Pipe:
Manning's "n" value (Table 4.2):
Pipe Slope:
Calculate Q f = 1.56 cfs
Calculate V = 2.86 fps
Design d/D (Table 4.3): 0.50
Q S
Q (Figure 1 or 2): 0.4
V S
V (Figure 1 or 2): 0.8
10 (diameter in inches)
PVC
0.010
0.003 (feet per foot)
Allowable Peak Flow: QS (Qf x QS)
f
V
Velocity at Flow Depth: V = ( V f x Vf
= (1.56x0.4) =0.62 cfs
= (2.86 x 0.8) = 2.29 fps
22
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4.7.1 Slope of Sewers
All sewers should be designed to transport average wastewater flows at mean velocities of two
feet per second based on the appropriate roughness factor. The slope between manholes shall
be uniform. The slope for sewer mains shall not be less than 0.40% unless the Engineer can
demonstrate why a lesser grade is necessary and as approved by the City. The required
minimum velocity shall be 2.0 feet per second (fps). The desired minimum velocity is 3.0 feet
per second. The desired maximum velocity is 9.5 feet per second. Sewers designed to carry
an average design flow of less than 0.1 cubic feet per second shall not be installed at a slope
of less than 0.6 ft/ 100 feet.
4.7.2 Hydraulic Jumps
Hydraulic jumps may occur in manholes when the slope of the upstream pipe is greater than
the downstream pipe. Care shall be exercised to avoid hydraulic jumps in conduits. When
unavoidable, structures shall be designed per Figure 3 and submitted with calculations for
approval.
4.7.3 Steep Grades /High Velocities
In the case of sewers where the slopes are such that over 15 percent grades are used or the
flow velocity exceeds 9.5 feet per second, special provisions shall be made to prevent
displacement of pipes and manholes by erosion and hydraulic forces. Such protection (i.e.
pipe anchors, special manholes, etc.) shall be shown on detail drawings and approved by the
Director of Public Works.
4.8 MANHOLE, JUNCTION STRUCTURES, AND CLEANOUTS
Manholes shall be installed at the end of each line, at all pipeline intersections, changes in
grade, size, alignment (except curvilinear sewers), and at distances not greater than those
listed in Section 4.8.6 below. For curvilinear sewers, manholes must be placed at all
intersections, changes in grade, changes in size, and at distances not greater than 400 feet.
Manholes must also be provided at all points of reverse curve, or where required by the
Director of Public Works. Manholes must be located to allow unassisted access by
maintenance vehicles which range in size from 1 /2 ton to 2 1 /2 tons. All manholes located
outside of dedicated street or alley rights -of -way will be designed and constructed with a bolt
down type cover as approved by the Director of Public Works. Lines and manholes located
in areas where access, in the opinion of the Director of Public Works, is not possible, will not
be approved for construction.
23
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4.8.1 Manhole Rings and Covers
Manhole rings and covers shall conform with the detail sheets for ring and cover designs per
the Standard Construction Specifications and Standard Details for the City of Pueblo,
Colorado.
4.8.2 Flow Channel
The flow channel shall be made to conform in slope and shape to that of the sewer pipe and
wherever possible, shall use the lower one -half of the sewer pipe for the invert of the open
flow channel. At intersections with other lines, channels shall be formed with a sweeping
curve to minimize turbulence.
4.8.3 Manhole Steps
Manhole steps shall be not less than eighteen inches nor more than twenty -four inches from
the top of the manhole ring and not more than twenty -four inches from the bench of the
manhole. Intermediate steps will be a sixteen inches apart, plus or minus 3 /a inch. Steps shall
be made of minimum 1 /z inch steel bar conforming to ASTM A615 Grade 60 encapsulated in
copolymer polypropylene. The steps shall be capable of withstanding a force of 350 pounds,
applied at any place on the step and in any direction which projects from the point of
application through a diameter of the step cross section at that point, with no permanent
deformation resulting.
4.8.4 Manhole Drops
A drop manhole will be required when the difference between the elevation of the inlet and
outlet flow lines is two feet (2') or greater. The incorporation of outside drop manholes into
a pipeline system should be restricted by the designer to those locations where no other means
of attaining slope or accommodating adequate flow velocity is feasible or where there are
physical limitations, (i.e., rock, groundwater, etc.). Outside drop manholes shall conform
with standard detail in configuration and size. See the Standard Construction Specifications
and Standard Details for City of Pueblo, Colorado.
4.8.5 Manhole Spacing
The maximum distance between manholes shall be as follows:
Pipe size Maximum Distance
8 " to 21 " 400 feet
larger than 21 " 500 feet
private sewers (when installed) 300 feet (per UPC)
24
4.8.6 Taps to Manholes
Sanitary service lines (building sewers) shall not be connected to the city main -line manholes
unless otherwise approved by the Director of Public Works.
4.8.7 Intersections
All pipes shall have free discharge into the collection system. Where possible, the flow line
of the intersecting pipe shall be at or above the design depth of flow of the collection sewer.
Minimum elevation drops at manholes are as follows:
Horizontal Deflection Angle of Minimum
Sewer Pipe at MH Drop
00 0.1 feet
Between 0' and 45' 0.2 feet
45 ° to 90 ° 0.3 feet
Changes in direction at intersections shall not be greater than 90'. The minimum drop at a
manhole with a 0' pipe defection can be less than 0.1 feet when the grades of the pipe entering
and exiting the manhole are the same and the pipe is laid continuous through the manhole,
using the bottom half of the pipe as the channel.
4.8.8. Cleanouts
For private sewer mains, ceanouts may be installed in lieu of manholes. Cleanouts shall be
installed in accordance with the provisions of the Uniform Plumbing Code.
4.9 PUMP STATIONS AND FORCE MAINS
Wastewater pumping stations are to be situated above flood levels by building a suitable
structure, preferably located off the right -of -way of streets and alleys. Pump stations will be
built for easy access into the pump- house. When wastewater must be pumped prior to grit
removal, the wet well and the discharge piping shall be designed to prevent grit accumulation.
It is the intent of the City that pump stations be standardized.
4.9.1 Configuration
The following items should be given consideration in the design of wastewater pumping
stations:
Wet wells and dry wells, including their super- structure, should be completely separated.
25
Provisions should be made to facilitate removal of pumps, motors, and valves for
replacement/ repair.
Suitable and safe means of access should be provided to dry wells and to wet wells containing
either bar screens or other mechanical equipment for inspection or maintenance. (Stairways
are preferred)
4.9.2 Pump Equipment Characteristics
A. Duplicate Units
Multiple pump units must be provided. Should only two units be provided,
equal capacity is required. Each pump shall be capable of handling flows in
excess of the expected maximum flow. Where three or more pumps are
provided, they should be designed to fit actual flow conditions and must be of
such capacity that with any one pump out of service, the remaining pumps will
have capacity to handle maximum wastewater flows.
Ejector - type and suction lift pumping stations will not be allowed unless
approved by the Director of Public Works.
B. Protection Against Clogging
Pumps handling raw wastewater should be preceded by readily accessible
screens with clear openings not exceeding 2 inches, unless special devices such
as comminutors are installed to protect the pumps from clogging or damage.
If the size of the installation warrants, a mechanically cleaned bar screen with
grinder is recommended. Where screens are located below ground, convenient
facilities must be provided for handling screenings. For the larger or deeper
stations, duplicate units of proper capacity are preferred.
1. Pump Openings
Pumps should be capable of passing spheres of at least 3 inches in
diameter. Pump suction and discharge openings shall be at least 4
inches in diameter.
2. Priming
The pump should be so placed that under normal operating conditions,
it will operate under a positive suction head. The NPSH and suction lift
requirements of the pumps shall be considered.
26
C. Electrical Equipment
Electrical equipment, located in enclosed areas where gas may accumulate, shall
comply with the National Board of Fire Underwriters' specifications for
hazardous locations. Electrical equipment for pump motors shall contain
elapsed time meters.
D. Intake
Each pump should have an individual intake. Wet -well design should be such
as to avoid turbulence near the intake and cavitation in the pump.
E. Dry -well Dewatering
A separate sump pump shall be provided in dry wells to remove leakage or
drainage with the discharge to the wet well above the overflow level of the wet
well. Water ejectors connected to a potable water supply will not be approved.
All floor and walkway surfaces should have an adequate slope to point of
drainage.
F. Pumping Rates
The pumps and controls of main pumping stations, and especially pumping
stations operated as part of treatment works or in developing areas, should be
selected to operate at varying delivery rates to permit discharging wastewater
from the station to the treatment plant at approximately the rate of delivery to
the pump station.
G. Pump Controls
Liquid level controller activators should be so located as not to be affected by
flows entering the wet well or by the suction of the pumps. Float tubes in dry
wells shall extend high enough to prevent overflow. Provisions should be made
to provide automatic alternations of the pumps in use.
H. Pump Valves
Suitable (readily accessible) shutoff valves will be located on suction and
discharge lines of each pump. A check valve or pump control valve shall be
placed on each discharge line, between the shutoff valve and the pump.
27
I. Pump Wet Wells
1. Divided Wells
When continuous pump station operation is required, division of the wet
well into two sections may be constructed, with properly interconnected
control gates, to facilitate repair and cleaning.
2. Size
The effective capacity of the wet well should provide a holding period
not to exceed 30 minutes for the design minimum flow. Smaller wet
wells may be considered when utilizing variable capacity pumping
systems.
3. Floor Slope
The wet well floor should have a minimum slope of 1 to 1 to the hopper
bottom. The horizontal area of the hopper bottom should be no greater
than necessary for proper installation and function of the pump inlet.
J. Pump Station Ventilation
Adequate ventilation shall be provided for all pump stations to mechanically
ventilate the dry well. If screens or mechanical equipment requiring
maintenance or inspection are located in the wet well, it shall be mechanically
ventilated. There shall be no inter - connection between the wet well and dry
well ventilating systems. In pits over 15 feet deep, multiple inlet and outlets are
desirable. Dampers should not be used on exhaust or fresh air ducts and fine
screens or other obstructions in the air ducts should be avoided to prevent
clogging. Switches for operation of ventilation equipment should be marked
and located conveniently. Consideration should be given to automatic controls
where intermittent operation is practiced.
Where excessive moisture or low temperatures become a problem,
consideration should be given to installation of heating and /or dehumidification
equipment.
1. Wet Wells
If mechanical wet well ventilation is required it should be continuous
and should provide at least 12 complete air changes per hour. For
intermittent operation, at least 30 complete air changes per hour should
be provided.
28
2. Dry Wells
Ventilation may be either continuous or intermittent. For continuous
operation, at least 6 complete air changes per hour should be provided.
For intermittent operation, at least 30 air changes per hour should be
provided.
K. Flow Measurement
At larger pumping stations, installation of suitable devices for measuring,
recording and totalizing wastewater flow and power consumption should be a
design consideration.
L. Water Supply
There shall be no physical connection between any potable water supply and a
wastewater pumping station; otherwise contamination of the potable water
supply may result. Provision of a water supply for washdown should be
planned.
M. Power Supply
Electric power supply will be tied -in from at least two independent generating
sources, or emergency power equipment should be provided. Automatic
starting of emergency power equipment shall be installed. Emergency power
generation units or portable pumping equipment on standby are considerations.
An overflow should be provided at such an elevation as to prevent basement
flooding or back water from affecting the operation. Where power failure
would result in objectionable conditions because of resultant discharge or
basement flooding, an emergency operation capability shall be provided. The
need for the latter requirement will be determined for each proposed installation
at the time plans are reviewed.
N. Alarm Systems
Alarm systems shall be provided for all pumping stations. The alarm shall be
designed and installed so as to activate in cases of power failure, pump failure,
or any other pump station malfunction. Pumping station alarms shall be
telemetered. An audio - visual device may also be installed at the station so as
to allow surveillance from the outside.
29
O. Instruction
Wastewater pumping stations shall come with a complete set of equipment
operational and maintenance manuals. The manuals shall include emergency
procedures, maintenance procedures, tools and such spare parts as may be
considered necessary.
Operation and maintenance manuals shall also be provided for all emergency
power generation equipment.
P. Force Mains
1. Size
The minimum allowable force main size is four inches in diameter
2. Velocity
At the design pumping rate (initial and ultimate), the velocity shall be at
least three feet per second, but no more than five feet per second.
3. Air relief valves
Automatic air relief valves shall be placed at high points in the force
main to prevent air locking.
4. Termination
Force mains shall enter the gravity sewer system at a point not more
than two feet above the flow line of the receiving manhole.
Q. Pump Cycling
Pump, wet well and force main configuration and capacity will be considered
in order to reduce excessive pump cycling over the range of flow rates expected
during the design life of the pumping station.
R. Special Conditions
Pumping station designs which do not follow the design criteria listed above will be
evaluated on an individual basis. Special circumstances may warrant additional
requirements.
30
4.10 INVERTED SIPHONS
The use of inverted siphons in sewer design shall be avoided, except in the most exceptional
cases. Where proposed, justification must be presented.
Inverted siphons shall have at least two barrels, with a minimum pipe size of eight (8) inches,
and shall be provided with necessary appurtenances for convenient flushing and maintenance;
the inlet and outlet structures shall have adequate clearance for rodding; and, in general,
sufficient head shall be provided and pipe sizes selected to insure velocities of at least 3.0 feet
per second under both initial and future conditions. The inlet and outlet details shall be
arranged so that the normal flow can be diverted to one barrel and so that either barrel may
be removed from service for cleaning.
4.11 STUB -ENDS OF LINES
Future pipeline extension requirements should be addressed, including provision of manhole
stub -outs at the end of a pipelines. However, stub -outs should not be used in cases where no
future extension of the sewer is possible or contemplated. Taps to stubs shall not be allowed.
4.12 STREAM AND DRAINAGE CROSSINGS
All stream and drainage channel crossings greater than 35 feet in length shall be ductile iron
encased in reinforced concrete unless otherwise approved by the City (see detail sheet in the
Standard Construction Specifications and Standard Details for City of Pueblo, Colorado). For
crossings less than 35 feet, either Schedule 40 PVC or ductile iron can be used, encased in
reinforced concrete.
Stream Crossings less than four feet below existing or proposed channel bottoms shall be
supported by reinforced concrete caissons, drilled a minimum of five feet into an impervious
soil unless deemed unnecessary by the City as determined on a case by -case basis. In the
absence of impervious soils, caissons shall extend twenty feet below the invert of the sewer
main.
4.13 RAILWAY AND HIGHWAY CROSSINGS
Design of crossings shall conform to the requirements of the Railroad Company or the
Colorado Department of Transportation.
31
4.14 HYDROGEN SULFIDE PRODUCTION (FORCEMAINS AND INVERTED
SIPHONS)
Short and long term hydrogen sulfide production effects within any Sanitary Sewer System
should be addressed by the designer particularly with respect to identifying and pinpointing
those locations where high generation potential is likely. The effect of deterioration caused
by hydrogen sulfide must be assessed in designing pipelines to ensure that a fifty (50) year
operational life is provided by the design.
High generation (sulfide) potential locations may involve or be found in some of the following
settings:
1. Areas of high - turbulence in the stream -flow which generate disagreeable and
unacceptable levels of hydrogen sulfide gas.
2. Areas where sulfide levels equal or exceed 1 mg /liter and rates of flow are low
without benefit of daily cleansing /oxidation velocities, or where detention creates
a loss of free oxygen levels below 50% of normal.
3. In areas where stream temperatures rise above the normal within the sewer line
environment due to highly thermal discharge points or sources.
Design approaches which should be considered in avoiding or reduction malodorous gas and
in providing for greater pipeline design life are:
1. Use of pipe material which does not react to acid attack (e.g. PVC).
2. For pipe sizes greater than 27 ", use a pipe material only as approved by Director
of Public Works.
3. Treatment of flows with chlorine, lime, iron or zinc salts, hydrogen peroxide or
nitrate chemical compounds in sufficient quantities to eliminate dissolved sulfide
based upon a periodic maintenance schedule for the length of pipeline affected.
4. Providing a coating or sleeve inside the pipeline with a material which is non -
reactive to hydrogen sulfide (beware of fabrication faults however, which may
accentuate sulfide concentrative deterioration).
5. Increasing the size of pipe above the "otherwise appropriate design ", even though
the larger pipe is seemingly oversized for the design flow. This design measure
is intended to increase the wastewater surface area leading to greater reservation
1 2
and less sulfide generation. Also, the perimeter of the sewer (and thus "dry"
surface area) increases with increasing pipe size leading to less wall penetration
from a given amount of acid.
CHAPTER 5. OPERATION AND MAINTENANCE OF SEWERS
Responsibility for the operation and maintenance of the Sanitary Sewer System is hereby
defined.
5.1 PUBLIC SEWERS
Only after dedication by the Developer, construction of the improvements in accordance with
the approved design, and written acceptance of the improvements by the City will the
operation and maintenance of the public Sanitary Sewer System become the responsibility of
the City. Maintenance by the City shall be conducted as part of the regular sewer maintenance
program of the City. Such maintenance shall not extend to any building sewer or private
sewer as defined herein.
5.2 PRIVATE SEWERS
Private sewers shall be the responsibility of the Owner(s) to install, maintain and repair. The
provisions of the operation and maintenance of any private sewers shall be clearly defined in
the Declaration of Covenants for each subdivision or development.
34
LIST OF REFERENCES
1. Sanitary Sewer Design Technical Manual City and County of Denver, Department of
Public Works, Wastewater Management Division, May, 1985.
2. Wastewater Division Rules for the Installation of Sewer Mains and Services City of
Colorado Springs, Department of Utilities, February, 1980.
3. Public Utilijy Improvements Rules and Regulations Regarding Standards and
Specifications City of Aurora, January, 1984.
4. Gravity Sanitary Sewer Design and Construction WPCF Manual of Practice No. FD-
5, 1982.
5. Water Quality Rules and Regulations Wyoming Department of Environmental Quality.
6. Water and Wastewater Technology Mark J. Hammer, John Wiley and Sons, 1986.
7. ISCO Open Channel Flow Measurement Handbook, Fourth Edition, Douglas M. Grant
and Brian D. Dawson, Isco Environmental Division, 1995.
8. Inspector Handbook for Sewer Collection System Rehabilitation National Association
of Sewer Service Companies, 1993.
9. Uniform Plumbing Code International Association of Plumbing and Mechanical
Officials, 1997.
10. Handbook of PVC Pipe, Design and Construction Uni -Bell PVC Pipe Association,
1982.
11. Standard Construction Specifications and Standard Details for Pueblo, Colorado City
of Pueblo, Department of Public Works, June, 1997.
12. Pueblo Municipal Code Charter and code of the City of Pueblo, Colorado, 1997.
13. Design Criteria Considered in the Review of Wastewater Treatment Facilities State
of Colorado, Department of Public Health and Environment, June, 1994.
35