HomeMy WebLinkAbout10023RESOLUTION NO. 10023
A RESOLUTION ADOPTING AND APPROVING REVISIONS TO THE SANITARY SEWER
DESIGN CRITERIA AND POLICIES MANUAL FOR THE CITY OF PUEBLO DATED DECEMBER
22, 2003, AND REPEALING RESOLUTION NO. 8703
WHEREAS, the City of Pueblo owns and operates a sanitary sewer collection system for
the purpose of collecting wastewater and transporting it to the water reclamation facility for
treatment; and
WHEREAS, protecting public health and safety and preventing nuisance conditions
requires safe and efficient operation of the sanitary sewer system; and
WHEREAS, safe and efficient operation of the sanitary sewer system requires orderly and
well-planned expansion and rehabilitation of the system; and
WHEREAS, planning, efficient design, and orderly expansion require clearly documented
policies and engineering design criteria,
BE IT RESOLVED BY THE CITY COUNCIL OF PUEBLO, 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
12-4-7(j)5(b) of the Pueblo Municipal Code, the Council does hereby adopt and approve as
minimum sanitary sewer standards the Sanitary Sewer Design Criteria and Policies for the City of
Pueblo published December 22, 2003, by the Wastewater Department, 211 East "D" Street,
Pueblo, Colorado, a true copy of which is attached hereto (hereinafter referred to as "Sanitary
Sewer Criteria"). The design of sanitary sewer facilities within the City after the date of approval of
this Resolution shall be performed in conformance with said Sanitary Sewer Criteria.
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 and re-
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 Criteria shall 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 Wastewater Department for purchase by the public at
a moderate price.
SECTION 4.
Resolution No. 8703 is hereby repealed.
INTRODUCED December 22, 2003
BY Al Gurule/Councilperson
APPROVED: Bill Sova/President of City Council
ATTEST: Gina Dutcher/City Clerk
Background Paper for Proposed
RESOLUTION
DATE: DECEMBER 22, 2003
AGENDA ITEM
DEPARTMENT: WASTEWATER DEPARTMENT
GENE MICHAEL, DIRECTOR
TITLE
A RESOLUTION ADOPTING AND APPROVING REVISIONS TO THE
SANITARY SEWER DESIGN CRITERIA AND POLICIES MANUAL FOR THE
CITY OF PUEBLO DATED DECEMBER 22, 2003, AND REPEALING
RESOLUTION NO. 8703.
ISSUE
Should the City Council adopt changes to the Sanitary Sewer Design Criteria and
Policies Manual for the City of Pueblo?
RECOMMENDATION
Approval of this Resolution.
BACKGROUND
The Sanitary Sewer Design Criteria and Policies manual sets forth engineering
design criteria for sanitary sewer construction, as well as policies for sanitary
sewer main extensions, cost recovery policies, and policies for dealing with
sanitary sewer backups. The manual was last updated in May 1999 and the
revisions were adopted by the City Council via resolution No. 8703. Resolution
8703 will be repealed and replaced by this present resolution.
In addition to correcting typographical errors and updating information and
references, the revisions include several substantive changes.
Cost Recovery: Replacing the word "reimbursement" with the term
"cost recovery" in the Development Policy (Sections 2.1.1.D and E)
and in the Main Extension Policy (Section 2.1.2) makes it clear that the
cost recovery program described in Title 16, Chapter 5 of the Municipal
Code is the sole mechanism provided for developers to recover
sanitary sewer installation costs.
Sanitary Sewer Backups: New language has been added (Section
5.3) describing the City's policy toward customers who experience
sanitary sewer backups. The policy establishes the following points:
· The "reasonable standard of care" for sanitary sewer maintenance
is defined as hydrocleaning accomplished every 24 months.
Cleaning sewer mains every 36 months is the standard of care
established by CIRSA.
· The "no-fault property damage" program is formalized. When
sewer backups result from blockages in a sanitary sewer main that
was cleaned within the previous 24 months, the City assumes no
liability for the backup but assists citizens by reimbursing citizens
for certain cleanup costs. This policy has been used for several
years, but had not previously been stated formally.
· The types of costs that are eligible and ineligible for
reimbursement under the no-fault property damage program are
defined.
· A cap of $3,500 is set for reimbursement of cleanup costs from the
Wastewater Department under the no-fault property damage
program.
· Customers must pay vendors for cleanup services, and the City
will then reimburse customers. The City will not pay vendors
directly.
· Customers must sign a release form in order to be compensated
under the no-fault property damage program
· Homeowners are responsible for the costs associated with
correcting protruding roots and faulty sewer taps at the connection
between the private service line and the City's main line.
FINANCIAL IMPACT
Funding for upsizing existing sanitary sewer mains will come from the Sanitary
Sewer Collection System Improvement Fund, which is funded by sewer
connection fees.
SANITARY SEWER DESIGN CRITERIA
AND POLICIES
FOR
CITY OF PUEBLO, COLORADO
DEPARTMENT OF WASTEWATER
211 EAST 'D" STREET
PUEBLO, COLORADO 81003
TELEPHONE: (719) 553-2298
FAX NO.: (719) 542-62~. ~
DECEMBER 22, 2003
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
CHAPTER 3.
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
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. l Public Sewers
5.2 Private Sewers
5.3 Sanitary Sewer Backups
LIST OF REFERENCES
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 4-2-20), 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 quantifies 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.
"Backup" means the flow of sewage from a sanitary sewer owned and operated by the City into a
private residence or business by means of the building sewer or service line, resulting from a
blockage in the sanitary sewer owned by the City.
"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. Branch sewers are
typically eight (8) inches to ten (10) inches in diameter. In plumbing, a branch sewer is the
sewer to which an individual building sewer is connected.
"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.
"CIRSA" means the Colorado Intergovernmental Risk Sharing Agency in which the City of
Pueblo participates with other municipal governments within Colorado for certain risk
management services.
"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 ¼ 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 ¼ 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.
"Cost Recovery" means the system established in Title 16, Chapter 5 of the Municipal Code that
provides a mechanism for developers to partially recover the costs of installing excess capacity
in sanitary sewer construction where oversize, off-site, or perimeter sewer improvements are
required to ensure that construction of the sanitary sewer system proceeds in a planned and
organized fashion and provides facilities that are adequately sized to serve reasonably anticipated
future development.
"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.
Development means any one (1) or more of the following activities:
a. Subdivision or resubdivision of one (1) or more parcels of property into distinct or
revised lots or parcels, or any other activity defined as a subdivision in Section 12-4-3 of
this Code;
b. Procurement of any building or plumbing permit to construct improvements upon
property which are intended for a use or occupancy likely to generate an increased
volume of wastewater or produce wastewater with an increase in concentration of
suspended solids, biological oxygen demand, metals or other pollutants; or
c. A rezoning of property which would permit a higher density use or other new use
which would foreseeably generate an increased volume of wastewater over the use or
uses of the property permitted by the existing zoning classification.
"Director of Public Works" is the manager of the Bureau of Public Works, or a designated
representative.
"Hydrocleaning" means the process of cleaning sanitary sewer lines using high-pressure water
jets that dislodges accumulated materials via the mechanical action of the water spray.
"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.
"Intercepting Sewer" means a sewer that receives flow from a number of collector sewers or
outlets and conducts such waters to the outfall sewer 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).
"Line" means a pipeline constructed for the purpose of conveying wastewater to the outfall
sewer.
"Line size" means the interior diameter of a round pipe.
"Low tap" means a service line not constructed in accordance with the requirements of Sheet SD
21, Sanitary Sewer Trench Detail, of the Standard Construction Specifications and Standard
Details for the City of Pueblo, Colorado, in that it connects to the sanitary sewer line so that the
flow line of the service line is below the spring line of the public sewer pipe for 8-inch and 10-
inch sewer mains, or below the top one-quarter of the public sewer pipe for 12-inch and larger
sewer mains.
"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 City of Pueblo Annexation
Agreement for the development.
"Private sewer" means a sanitary sewer main, pipe, or piece of equipment in a right-of-way or
easement to which title has not been conveyed to the City of Pueblo, but which connects to the
sanitary sewer collection system owned and operated by the City of Pueblo for the purpose of
conveying sanitary sewage to Pueblo's water reclamation facility for treatment and disposition.
A private sewer receives the discharge from one or more building drains and conveys it to a
public sewer, private sewage disposal system, or other point of disposal.
"Protruding tap" means a service line not constructed in accordance with the requirements of
Section 12.3.15 of the Standard Construction Specifications and Standard Details for the City of
Pueblo, Colorado, in that it protrudes into a sanitary sewer line in such a manner that it can block
the passage of cleaning equipment and can cause a blockage in the sewer line by providing a
point at materials carded in sewage can accumulate to block normal sewage flow.
"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 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.
"Reimbursement" means payments made to persons to partially compensate for the costs of
removing sewage and cleaning fouled structures in private homes or businesses resulting from a
blockage in a sanitary sewer owned by the City.
"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 Line" or "Building Sewer" 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.
"Service Stub" means a portion of a future building sewer rmming 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.
"Springline" means the horizontal mid-height line of a pipe with a circular cross section, or a
horizontal line at half the height of the minor axis for a pipe with a non-linear cross section.
"Standard Construction Specifications and Standard Details for the City of Pueblo, Colorado"
means the manual developed by the City of Pueblo's Bureau of Public Works related to
construction specifications and standard details, dated February 26, 2001, and as same may be
amended.
"Trunk Sewer" means the principal sewer to which branch sewers are tributary. Trunk sewers
are typically ten (10) inches to twelve (12) inches in diameter.
"UPC" means the that edition of the Uniform Plumbing Code produced by the International
Association of Plumbing and Mechanical Officials specified in Title IV, Chapter 4, Article 1 of
the Municipal Code, and as same may hereafter be amended.
"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 any lawfully
or unlawfully contributed 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 and accepted in writing by the City. Private
sewers and pump stations are intended to serve only site specific developments, (i.e., shopping
centers, special area plans, condominium developments, subdivisions where the subdivision
approval process provided for the sanitary sewer system within the subdivision to remain private,
etc.) and shall not serve any area beyond the development or become part of the Sanitary Sewer
System. The City of Pueblo is not responsible for operating or maintaining private sewers or
private pump stations.
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
All Development within the City shall require connection to the City's Sanitary
Sewer System.
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.
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.
If a larger sanitary sewer system (including pumping systems) is required to serve
a sub-basin area as described in 2.1.1.B and 2.1.1.C 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 to recover a portion of the
larger system within the developed area.
Any cost recovery to the Developer for constructing a portion of the Sanitary
Sewer System with a capacity greater than that required to serve the Development
will be based on the following:
Cost recovery related to oversizing the collection system shall only be
considered for sewer mains twelve (12) inches or larger. The dollar value
eligible for cost recovery shall be the difference in the cost of pipe and
installation between twelve (12) inches and the actual size installed.
10
Cost recovery related to oversizing pumping systems shall be based upon
the difference in cost between the capacity required to serve the
Development as described in 2.1.1.B and the capacity required to serve the
sub-basin as described in 2.1.1.C, as determined from information and
data submitted by the Developer and approved by the City of Pueblo.
Sanitary sewer lines smaller than twelve (12) inches are not part of the Backbone
System. Proposed developments will not be allowed to connect to sanitary sewer
lines smaller than twelve (12) inches unless adequate capacity is available to
accommodate the proposed development. If capacity is available, connection to
sanitary sewer lines smaller than twelve (12) inches may be approved by the
Director of Public Works. If there is insufficient capacity in the existing sanitary
sewer system, the Developer shall extend the sanitary system in accordance with
Section 2.1.2. As an option, the Developer may upgrade existing sanitary sewer
lines smaller than twelve (12) inches as approved by the Director of Public Works
and consistent with the intent of the City's Master Sewer Plan.
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 cost recovery for said extensions.
Co
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.
The Sanitary Sewer System shall be sized to the ultimate capacity as described in
Section 2.1.1.C and extended to the exterior boundaries of each subdivision
within the development.
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.
11
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
pur.suant to Section 16-11-4 of the Pueblo Municipal Code, or as same may be amended.
2.1.4 Street or Alley 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:
2.3.1.
Planning Criteria for Sanitary Sewers
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.
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.
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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 Peak Peak Flow
"Per Acre" (1) Factor "Per Acre" (1)
CFS MGD CFS MGD
Single-Family 0.0016 0.0010 2.6 0.0042 0.0027
Residential
Multiple-Family 0.0003 0.0002 2.6 0.0009 0.0006
Residential per unit per unit per unit 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 Special Study Required
Industries
Institutional Use Special Study Required
Areas Outside The 0.0017 0.0011 2.6 0.0044 0.0028
Development
Plan(Unplanned)
(1) Unless otherwise tated
2.4.2 Infiltration and Inflow
Identify and design for areas with a high potential for groundwater infiltration. Maximum
allowable infiltration/inflow (I/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.
13
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 En ineerin Re ort
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 (BODs and TSS) of wastewater and industrial waste
characteristics
D. The report shall also ad&ess the following for both initial and future conditions:
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.
14
4. Wastewater detention time in the wet well and force main.
15
CHAPTER 3. PROCEDURES/SUBMITTALS FOR
SUBDIVISIONS AND MASTER DEVELOPMENT PLANS
3.1 SUBDIVISIONS
Procedures and submittals for subdivisions shall be in accordance with the Application, Review,
and Approval Process Manual for Subdivisions, November 2002, and as same may hereafter be
amended.
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 I 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.
The Report shall include but not limited to:
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1. Master Development Plan (Land Use Plan)
2. Tabulation of peak flows and preliminary pipe sizes.
Locations of all points on the City's existing sewer system where the new system
will connect.
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).
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 (4) 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 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
18
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, whichever is greater. 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--MINIMUMPIPERADIUS
Pipe Diameter(inches) Minimum Radius of Curvature(~et)
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 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,
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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;
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 and compacted 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 and compacted 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:
O. 00061 s ~
Q=- xdTxs5
n
or
20
Q=VA
or
1.486 2 ~
Q=-- RTs~A
Where Q
d =
D =
A =
S
Flow in cubic feet per second
= Velocity in feet per second
= Friction factor
Pipe diameter in inches
Pipe diameter in feet
Area of pipe in square feet
Pipe slope in feet per foot.
area of pipe
D in feet
R = Hydraulic radius = 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
0.010
Ductile Iron (polyethylene lined)
(DIP)
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.
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Table 4.3 - DESIGN DEPTH OF FLOW
PIPE SIZE
6" private
8"
DESIGN DEPTH OF FLOW (d/D)
0.50
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:
Flow at depth "d", pipe flowing partly full
Flow with pipe flowing full
Velocity with flow at depth "d"
Velocity with pipe flowing full
Depth of water in pipe, measured vertically along centerline of pipe
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 fi. The allowable depth of flow is 0.5, thus d/D is 0.5. Using
Figure 2, the hydraulic element Qs/Qf is 0.4 and VdVf. is 0.8. Knowing that the Qf 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 Vf of 2.86 ft/s, the 0.5 depth of flow will have a velocity of 0.8 x 2.86 fi/sec or 2.29
fi/sec.
Size of Pipe: 10 (diameter in inches)
Type of Pipe: PVC
Manning's "n" value (Table 4.2): 0.010
Pipe Slope: 0.003 (feet per foot)
Calculate Qf = 1.56 cfs
Calculate Vf = 2.86 fps
Design d/D (Table 4.3): 0.50
Q/. (Figure 1 or 2): 0.4
22
V$
V~ (Figure 1 or 2):
Allowable Peak Flow:
Velocity at Flow Depth:
0.8
Qs= (Q.r x ~) = (1.56 x 0.4) = 0.62 cfs
vs=(V/ x v" )=(2.86 xO. 8)= 2.29 fps
v/
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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 4.8.5 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 ½ ton to 2 ½ 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.
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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 3A inch. Steps shall be made of
minimum ½ 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 pemianent 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"
larger than 21"
private sewers (when installed)
400 feet
500 feet
300 feet (per UPC)
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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
Sewer Pipe at MH
0°
Between 0° and 45°
45° to 90°
Minimum
Drop
0.1 feet
0.2 feet
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, cleanouts may be installed in lieu of manholes.
installed in accordance with the provisions of the Uniform Plumbing Code.
Cleanouts shall be
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.
Provisions should be made to facilitate removal of pumps, motors, and valves for
replacement/repair.
26
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.
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.
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.
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.
27
D. Intake
Eo
Fo
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.
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.
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.
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.
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.
Pump Wet Wells
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.
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.
28
Jo
o
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.
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 intemfittent operation
is practiced.
Where excessive moisture or low temperatures become a problem, consideration
should be given to installation of heating and/or dehumidification equipment.
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.
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.
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.
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.
29
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.
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.
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.
Force Mains
Size
The minimum allowable force main size is four inches in diameter
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.
Air relief valves
Automatic air relief valves shall be placed at high points in the force main
to prevent air locking.
30
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.
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 SDR 26 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
31
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.
4.14 HYDROGEN SULFIDE PRODUCTION (FORCE MAINS 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.
The following settings have the potential to generate high levels of hydrogen sulfide:
1. Areas of high-turbulence in the stream-flow which generate disagreeable and
unacceptable levels of hydrogen sulfide gas.
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.
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.
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).
32
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 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.
4.15 CONCRETE PROTECTION IN HIGH-SULFATE SOILS
High-sulfate soils are common throughout Pueblo. To protect concrete installations from
corrosion in high-sulfate soils, all concrete mixes must comply with the specifications presented
in Article 4 of the Standard Construction Specifications and Standard Details for the City of
Pueblo, Colorado, February 26, 2001, and as same may be amended.
33
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.
5.3 SANITARY SEWER BACKUPS
5.3.1 Responsibilities
5.3.1.1 Standard of Care
The City of Pueblo exercises what it believes to be a reasonable standard of care in maintaining
and cleaning sanitary sewer lines by cleaning the City's lines at least once per 24 months using
hydrocleaning. If a City sanitary sewer line has been hydrocleaned within 24 months prior to a
backup event, the City is deemed to have exercised a reasonable standard of care, the City is not
negligent, and negligence on the part of the City is deemed not to have been the proximate cause
of the event.
5.3.1.2 Emergency Response
The City of Pueblo makes reasonable effort to provide emergency response to sanitary sewer
problems, including backups, on a 24-hour basis. This response is provided by means of
assigning employees to standby duty, with communication accomplished by means of mobile
telephones.
5.3.1.3 Homeowner/Business Owner Responsibilities
Homeowners and business owners are responsible for maintaining building sewers, service lines,
and private sewers that connect structures to sanitary sewers. Roots protruding from service
lines and grease discharged from household taps are frequent causes of sanitary sewer backups.
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Protruding taps can block the passage of cleaning and inspection equipment, thus preventing
normal maintenance activities, and they can block the movement of materials through the
sanitary sewer line resulting in backups. Low taps increase the likelihood of backups because
they are constructed in a manner that allows wastewater to flow from the sanitary sewer line into
a service line. Because they are part of the service line, protruding taps and low taps are the
responsibility of the homeowner or business owner.
5.3.1.4 Roots and Grease
Roots protruding from service lines and grease discharged from household taps are frequent
causes of sanitary sewer backups. The Municipal Code of the City of Pueblo prohibits the
discharge to the sanitary sewer collection system of materials in such concentration or amount as
to restrict the hydraulic capacity of the collection system (Section 16-7-14(3)). Where roots
enter the sanitary sewer collection system from a private sewer or service line, removal of such
roots are the responsibility of the homeowner or property owner, and the City cannot assume
responsibility for backups caused by such conditions where normal maintenance activities have
been performed within 24 months preceding the backup. Because discharge of grease in
quantities sufficient to restrict the hydraulic capacity of the collection system is prohibited, the
City is not responsible for backups caused by such conditions.
5.3.2 Compensation Program
5.3.2.1 No-Fault Property Damage Program
The City of Pueblo maintains a "no-fault" property damage program to ease the burden upon
residents who have experienced a sewer backup into a home or business by reimbursing certain
costs associated with cleanup following a sewer backup. Compensation under this program is
not required of the City, nor does it indicate or admit liability on the part of the City. The City's
no-fault property damage program does not cover the cost of replacing carpeting or other
damaged goods. It only covers those activities required to return a home or business to a
reasonably safe condition by removing sewage and disinfecting those areas of homes or
businesses that come into contact with sewage as a result of a sanitary sewer backup. This
program is limited to the amounts lawfully appropriated therefor in the discretion of City
Council, and no payment may be made unless unencumbered funds are available therefor.
5.3.2.2 Insurance Program
The City of Pueblo participates in liability risk sharing through CIRSA. CIRSA may make a
determination as to whether the City of Pueblo is legally responsible for a sewer backup. Claims
for replacement of carpeting and other items are processed by CIRSA. Normally, claims for
replacement of items damaged by sewer backups are evaluated based on whether the City of
Pueblo accomplished its goal of cleaning the sanitary sewer line in which the backup occurred
within the 24 months immediately prior to the backup event. If the City did accomplish this
goal, then there is no negligence on the part of the City and requests for reimbursement are
normally denied.
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5.3.3 No-Fault Property Damage Ineligible Costs
The following costs are not eligible for Reimbursement under the City of Pueblo's no-fault
property damage program:
5.3.3.1 Replacing carpeting, tile, rugs, clothing, toys, furniture, or other household item
5.3.3.2 Refurbishing carpeting, tile, rugs, clothing, toys, furniture, or other household items
5.3.3.3 Re-installing carpeting, tile, sheet rock, doors, wainscoting, molding, plumbing fixtures,
etc.
5.3.3.4 Cleaning air ducts associated with forced-air furnaces or central air conditioning
5.3.3.5 Remediation for mold
5.3.4 No-Fault Property Damage Eligible Costs
Provided funds are available, the following costs are eligible for Reimbursement under the City
of Pueblo's no-fault property damage program:
5.3.4.1
5.3.4.2
5.3.4.3
5.3.4.4
5.3.4.5
Removing and disposing of carpet, carpet pads, tile, sheet rock, doors, wainscoting,
molding, etc. damaged by a backup
Cleaning sub-flooring or concrete pad
Disinfecting sub-flooring or concrete pad
Removing liquids and solids deposited by the backup using pumps, vacuums, or similar
types of equipment
Drying areas affected by the backup using blowers, fans, dehumidifiers, heaters, or other
types of equipment
5.3.5 Reimbursement for Cleanup Costs
5.3.5.1
When damage to furnishings results from a sewer backup, homeowners and business
owners are responsible for contacting firms that remediate water damage and for paying
the costs of those services. In order to obtain reimbursement from the Wastewater
Department for cleanup costs under the no-fault property damage program, homeowners
and business owners must promptly submit invoices for cleanup services to the
Wastewater Director.
5.3.5.2 All claims of damage or loss must be made in sufficient detail to allow the Wastewater
Director to investigate the incident, make a detailed examination of the costs for which
reimbursement is requested and determine whether such requests are eligible for
reimbursement.
5.3.5.3
Customers being reimbursed for cleanup costs must sign a release and settlement
agreement releasing and holding the City harmless from any other claims arising from the
incident as a condition of receiving reimbursement.
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5.3.5.4 Reimbursement for cleanup costs under the no-fault property damage program shall be
limited to a maximum of $3,500.
5.3.6
5.3.6.1
5.3.6.2
Discretionary Reimbursements
In extreme circumstances, the Wastewater Director may exercise discretion to authorize
limited reimbursement for damaged items based on circumstances of unusual need. Such
circumstances may include, but may not be limited to, advanced age of household
residents, chronic illness making occupants unusually susceptible to infection, or low or
fixed income of household residents.
In extreme circumstances, at the discretion of the Wastewater Director, reimbursement
may be made for the cost of a plumber or drain cleaning service. Citizens are strongly
encouraged to contact the Wastewater Department before contacting a plumber so that
the sanitary sewer collection system can be inspected and blockages cleared before
unnecessary plumber's fees are incurred.
5.3.6.3 In extreme circumstances, the Wastewater Director may exercise discretion to authorize
limited reimbursement for members of an affected household to occupy a motel
temporarily until cleanup and disinfection has been completed. The total of such costs
shall be limited to $150 per household member for each incident.
5.3.6.4 Discretionary reimbursements shall be limited to $1,500.00 per occurrences.
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LIST OF REFERENCES
Sanitary Sewer Design Technical Manual, City and County of Denver, Department of
Public Works, Wastewater Management Division, May, 1985.
Wastewater Division Rules for the Installation of Sewer Mains and Services, City of
10.
11.
12.
13.
Colorado Springs, Department of Utilities, February, 1980.
Public Utility Improvements Rules and Regulations Regarding Standards and
Specifications, City of Aurora, January, 1984.
Gravity Sanitary Sewer Design and Construction, WPCF Manual of Practice No. FD-5,
1982.
Water Quality Rules and Regulations, Wyoming Department of Environmental Quality.
Water and Wastewater Technology, Mark J. Hammer, John Wiley and Sons, 1986.
ISCO Open Channel Flow Measurement Handbook, Fourth Edition, Douglas M. Grant
and Brian D. Dawson, Isco Environmental Division, 1995.
Inspector Handbook for Sewer Collection System Rehabilitation, National Association of
Sewer Service Companies, t 993.
Uniform Plumbing Code, International Association of Plumbing and Mechanical
Officials, 1997.
Handbook of PVC Pipe, Design and Construction, Uni-Bell PVC Pipe Association, 1982.
Standard Construction Specifications and Standard Details for Pueblo, Colorado, City of
Pueblo, Department of Public Works, June.
Pueblo Municipal Code, Charter and code of the City of Pueblo, Colorado.
Design Criteria Considered in the Review of Wastewater Treatment Facilities, State of
Colorado, Department of Public Health and Environment, June, 1994.
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