HomeMy WebLinkAboutR-2003-28 adopt portion of PICM called for in ordinance 1444/sanitary sewer system design & improvements
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RESOLUTION NO. 2003- ~ ~
A RESOLUTION ADOPTING A PORTION OF THE "PUBLIC IMPROVEMENT
CRITERIA MANUAL" ("PICM") CALLED FOR IN ORDINANCE 1444 OF THE CITY
OF LA PORTE (THE DEVELOPMENT ORDINANCE OF THE CITY OF LA PORTE),
RELATING TO SANITARY SEWER SYSTEM DESIGN CRITERIA AND
IMPROVEMENTS; MAKING CERTAIN FINDINGS RELATING TO THE SUBJECT;
FINDING COMPLIANCE WITH THE OPEN MEETINGS LAW; PROVIDING A
SEVERABILITY CLAUSE; AND PROVIDING AN EFFECTIVE DATE.
WHEREAS, the City Council has directed the qualified professionals of the City's
staff to prepare a Public Improvement Criteria Manual, setting forth City Policy and
guidelines relating to the design and construction of certain Public Improvements within
the City of La Porte, by virtue of the passage of Ordinance 1444, otherwise known as the
Development Ordinance of the City of La Porte; and
WHEREAS, City Staff has developed a portion of said policy, relating to drainage
criteria and improvements; and
WHEREAS, the Planning and Zoning Commission of the City of La Porte has
reviewed said policy (in the form attached hereto as Exhibit U2"), and has received public
comment on said policy at its meeting held on September 18, 2003, pursuant to due
notice, and
WHEREAS, the Planning and Zoning Commission recommends approval of said
Policy, in the form attached hereto as Exhibit U2;"
NOW, THEREFORE, BE IT RESOLVED BY THE CITY COUNCIL OF THE CITY OF LA
PORTE, TEXAS:
Section 1. The facts and matters set forth in the preamble of this Resolution
are hereby found to be true and correct.
Section 2. The portion of the PICM relating to Sanitary Sewer Collection
System Design Criteria and improvements, as set forth on Exhibit U2" attached hereto, is
hereby adopted by the City Council of the City of La Porte.
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Section 3. The City Council officially finds, determines, recites, and declares
that a sufficient written notice of the date, hour, place and subject of this meeting of the
City Council was posted at a place convenient to the public at the City Hall of the City for
the time required by law preceding this meeting, as required by the Open Meetings Law,
Chapter 551, Texas Government Code; and that this meeting has been open to the
public as required by law at all times during which this ordinance and the subject matter
thereof has been discussed, considered and formally acted upon. The City Council
further ratifies, approves and confirms such written notice and the contents and posting
thereof.
Section 4. In the event any clause, phrase, provision, sentence, or part of
this Resolution or the application of the same to any person or circumstance shall for
any reason be ajudged invalid or held unconstitutional by a court of competent
jurisdiction, it shall not affect, impair, or invalidate this resolution as a whole or any part
or provision hereof other than the part declared to be invalid or unconstitutional; and the
City Council of the City of La Porte, Texas, declares that it would have passed each and
every part of the same notwithstanding the omission of any such part thus declared to be
invalid or unconstitutional, whether there be one or more parts.
Section 5. This Resolution shall become effective after its passage and
approval, and it is so ordered.
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PASSED AND APPROVED, this November 10, 2003
By:
CITY OF LA PORTE
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Mayor
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REQUEST FOR CITY COUNCIL AGENDA ITEM
Requested By:
Agenda Date Requested:
er 10 2003
Appropriation
Source or Funds:
Department:
Account Number:
Report:
Resolution: X Ordinance:
Amount Budgeted:
Exhibits:
1.
Resolution
Amount Requested:
Exhibits:
2.
Sanitary Sewer System Design Criteria Budgeted Item: YES NO
Exhibits:
SUMMARY & RECOMMENDATION
The City has been working to improve and refine the City of La Porte's sanitary sewer system design criteria.
Standardization of design criteria of public sanitary sewer systems simplify and insure quality collections systems
that are constructed to be both effective and of high enough capacity to accommodate population growth. . As part of
the ongoing outreach efforts to involve the citizens in their local government, a voluntary public hearing on the
sanitary sewer system design criteria was held before the Planning & Zoning Commission to receive public input.
Another part of this outreach program entailed the distribution of the proposed criteria to various engineering
consultants including Lockwood, Andrews & Newnam, Inc., Manning Engineering, ESOR Engineering, Windrose
Services, Klotz & Associates, Inc., PBS&J, Brown & Gay, Inc., local developer Eddie Gray, H. Carlos Smith, and
UA Engineering. Comments were received from Windrose Services, and PBS&J. Internally, the proposed design
criteria was reviewed by the Public Works department and the Inspections Department. The proposed sanitary
sewer design criteria will become Chapter 4 of the Public Improvements Criteria Manual (PICM). Currently there is
only one chapter ofPICM - Chapter 5 which deals with the design of storm sewer drainage systems. The need for a
full and complete PICM stems from the Development Ordinance which refers to PICM as being the location for
applicable design criteria for use in the design of public systems.
At its September 18, 2003 meeting the La Porte Planning & Zoning Commission solicited and received public
comment on the proposed Sanitary Sewer System Design Criteria. The Commission voted at that ineeting to
recommend approval of the proposed Chapter 4 to the City Council.
Action Reauired bv Couneil:
Conduct public hearing to receive citizen input on the proposed Sanitary Sewer Design Criteria and consider
approving a resolution adopting the Sanitary Sewer Design Criteria Chapter of the Public Improvements Criteria
Manual.
ADDroved for City Council A2enda
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Date
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EXHIBIT 1
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EXHIBIT 2
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CHAPTER 4
SANITARY SEWER DESIGN REQUIREMENTS
4.01 CHAPTER INCLUDES
A. Criteria for the design of sanitary sewer systems.
B. This chapter addresses the design of the sanitary sewer systems to be located within the
public right-of-way or a dedicated public easement. Sanitary sewers located on private
property, that are not in a dedicated public easement, shall not be considered part of the
publicly maintained sanitary sewer system.
C. On a case-by-case basis the City of La Porte reserves to the right to allow deviations from
these design criteria where necessary. These design criteria are not intended to cover
repairs to pre-existing facilities especially when such repair work is performed by City of
La Porte personnel/forces. These criteria are not intended to cover existing sanitary
sewer facilities located in alleys or other areas that do not conform to these criteria.
4.02 DEFINITIONS
A. Public Sanitary Sewer - All sewers that are maintained by the City of La Porte and
located in public easements or street rights-of-way, pre-existing sanitary sewer lines that
are serving the public at the time of the adoption of these regulations, and new sanitary
sewers that are installed in accordance with these standards.
B. Sanitary Sewer Main - A sewer which receives the flow from one or more lateral sewers.
C. Lateral Sewer - A sewer running laterally down a street, alley or easement which
receives flow from abutting property.
D. Service Lead - A sewer which branches off of a public sewer and extends to the limits of
the public right-of-way. It shall be construed as having reference to a public sewer
branching off from a main or lateral sewer to serve one or more houses, single family
lots, or other types of small land tracts situated in the same block, but not directly
adjacent to the main or lateral sewer. A service lead shall never exceed 60 feet in
perpendicular length from the intersecting sewer main or lateral. If the sewer is designed
to serve more than two houses, or the equivalent of two single family residences along a
street, a lateral sewer as defined above shall be constructed.
4.03 DESIGN REQUIREMENTS
A. Drawings to be Furnished
1. Before any sanitary sewer main or lateral sewer is constructed and before the
City will approve any proposed sanitary sewer for construction, plan-and-profile
sheets of the proposed sanitary sewer shall be prepared and submitted to the City
for approval.
2. These drawings shall become the property of the City of La Porte.
3. Drawings shall include at a minimum layout sheets with contours, plan-and-
profile sheets, and details sheets for special items.
B. Details to be Shown on Drawings:
1. The construction drawings shall show at a minimum the exact location of the
proposed sanitary sewer in the right-of-way, alley, or public easement with
respect to the edge of the particular right-of-way, survey base line, any nearby
utilities, 100-year floodplain elevation within the project area, major
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landscaping, and other structures (above ground and below ground) within the
construction site.
C. Sanitary Sewer Mains and Lateral Sewers
1. Sanitary sewers shall be identified by number, letter, or other identification as
shown on the sanitary sewer layout sheet and manholes identified by letter or
number.
2. Sanitary sewers in curved easements, easements defined by property lines, and
combined easements containing other public utilities must be shown in both plan
and profile views.
3. The profile shall show other underground and surface utilities and facilities, both
in parallel and at crossings; the size, grade, and type of pipe of the proposed line,
the elevations of the proposed line to the hundredths of a foot at manholes,
changes of grade and clean outs where allowed; and the proposed finished grade
over the sewer with elevations. Where proposed fill or cut is contemplated, the
proposed new natural ground line should be shown as a separate line from the
pre-existing natural ground line. Bedding and backfill shall comply with City of
La Porte standard specifications and standard details where applicable.
4. The construction drawings shall show the existing natural ground line at either
the right-of-way or edge of easement when the proposed sanitary sewer is to be
placed:
a. Between the existing pavement and the right-of-way line.
b. Between existing pavement and an existing or proposed easement.
5. When a sanitary sewer under existing pavement, then the finished elevations of
the pavement shall be shown on the construction drawings.
D. Plan and Profile Required for Sewer Mains
1. Sanitary sewer overall layout sheets for single family residential subdivisions
should use a standard engineering scale large enough to show the entire project
on 1 no more than 2 standard 24"x36" sheets. In all cases, the following
infonnation must be shown on the layout.
a. All easements containing or buffering sanitary sewers. These
easements shall be labeled both as to width and type.
b. Sanitary sewer sizes are shown at points of size change
c. All manhole locations.
d. The sanitary sewer alignment shall accurately reflect in the plan and
profile sheets the location of the sanitary sewer as shown on the
detailed plan view.
e. Service leads that cross street pavement or serve adjacent property
are to be shown on the overall layout.
f. The number, size, and layout of the lots depicted on both the overall
sanitary sewer layout sheet and the individual plan-and-profile sheets
shall match the number and size of the lots depicted on the final plat
after recordation.
g. The size and direction of flow for existing and proposed sanitary
sewers shall be shown on the overall sanitary sewer layout sheet.
h. The location of the proposed sanitary sewer within either the public
right-of-way or a dedicated public easement.
i. The overall sanitary sewer layout sheet shall show the area, in acres
or in number of lots plus any acreage outside the project area, which
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the proposed sewer is designed to serve. Include a vicinity map
which references the project or lots to nearby major thoroughfares.
2. Commercial sanitary sewer layouts shall follow the same overall layout sheet
format.
3. Horizontal and vertical scales for the detailed plan-and-profile views shall be
confined to standard engineering scales.
4. The plan view shall show, at a minimum, all of the following information for the
project area:
a Topographical features.
b. Stationing for the proposed sewers.
c. All existing utilities including gas, power, telephone, fiber optic,
cable etc.
d. Any significant landscaping or other structures which might impact
construction or construction-related activities.
e. The width and type of existing and/or proposed easements.
f. Proposed service leads.
g. The limits of any proposed bore and jack, microtunnel, or auger
operations.
h.Locations where pressure pipe is to be installed for water line
crossings.
i. The proposed sanitary sewer with pipe diameter, length, material
type, and grade clearly labeled.
5. The profile view shall show, at a minimum, all of the following information for
the project area:
a. Underground and surface utilities/facilities which are either parallel
to the proposed sanitary sewer or cross the proposed sanitary sewer
within the construction site.
b. The proposed sanitary sewer's diameter, grade, length, and material
type for each section between manholes. This shall be labeled on
every applicable page and identified as ''proposed.''
c. The flowline elevation for every sanitary sewer at every manhole.
d. The top ofrim elevation ofatfected existing and proposed manholes.
e. The flowline elevation at each sheet break.
f. The type of pipe bedding and backfill shall comply with City of La
Porte standard specifications and standard details where applicable.
g. The finished grade for proposed and existing pavement. Where cut
and fill are proposed, the proposed new natural ground line should be
shown as a separate line from the existing natural ground line.
h. The existing natural ground line at the centerline of the sanitary
sewer when a sewer is to be placed between the edge of pavement
and the public right-of-way. In the cases where roadside ditches
exist, the centerline elevations of the roadside ditch shall be shown.
i. The existing ground line at the centerline of the proposed sanitary
sewer where a sanitary sewer is to be placed within an existing
easement. Show any proposed cut and fill as described above.
j. The limits of any proposed bore and jack, microtunnel, or auger
operations.
k. Locations and limits of where pressure pipe is to be installed for
water line crossings.
1. The location of special backfill and any proposed stacks shall be
identified by stations indicated on the design plans.
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m. A void vertical breaks in profiles. Use alternate scale for all profile
sheets if all of proposed sanitary sewer cannot be shown on anyone
profile section for the station run indicated in plan view for that
sheet.
6. All construction drawings for new sanitary sewers shall show the proposed
location, by stations and offsets, of all service leads, and service connection
risers.
E. Service Lead Construction for Residential and Commercial Developments
1. Space the location ofservice leads so as to limit the number of service lead taps
to the lateral sewer or sewer main. Service leads should be spaced at every other
property line between two adjoining residential lots unless there is an odd
number of lots. The City reserves the right to direct the engineer to relocate any
proposed service lead upon reviewing any submitted plans. A single 6-inch
service lead located at the property line between two adjoining residential lots
would serve two single-family residences with a wye placed at the end of the
service lead. The wyes shall be located at the private property line.
a. Near side double sewer service leads shall not exceed 5 feet in length,
shall terminate at the property line, and shall be located within the
public right-of-way or public easement.
b. In cases where the sanitary trunk main is further than 5 feet from edge
of the right-of-way, a single 6-inch service shall be run from the sewer
main to the edge of the right-of-way whereupon a wye shall be placed
as described above in Article 4.02, Section E, Clause I if 2 lots or
parcels are to be served. This shall apply to residential sanitary service
leads and not to commercial service taps.
2. Any far side service lead of more than 60 feet perpendicular to the street right-
of-way shall, at the City's discretion, be treated as a lateral sewer.
3. Service leads for single-family developments should not connect to the manhole,
and may be granted approval on a case by case basis. Commercial or industrial
service leads expected to discharge more than 5000 gallons-per-day shall
discharge directly into a proposed or existing sanitary sewer manhole. Where
the flowline of the service lead is 36 inches or greater above the flow line of the
manhole, provide a standard drop manhole.
a. Service leads shall be provided to serve each lot or parcel within a
proposed residential, commercial or industrial development. The
detail for a typical near-side and far-side service leads shall be
included with the construction drawings.
b. Service leads shall be a minimum of 6 inches in diameter where two
or more lots or parcels are served. If the perpendicular length of a
service lead exceeds 60 feet, the minimum diameter shall be S inches
and a manhole shall be utilized for connection to the public sewer.
Such Sinch leads may, at the discretion of the City, be reviewed
upon submittal of the construction drawings as a lateral sewer line.
c. In such cases where a service lead is proposed to run diagonally
across the street, prior approval from the City Engineer must be
obtained.
d. Service leads with a diameter of 6 inches shall utilize full body
fittings be they extruded or factory-fabricated for connection to a
proposed public sewer or an approved saddle-type connector for
connection to an existing public sewer.
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e. PVC saddle-type connectors with gasket and stainless steel straps
shall be installed with the stub oriented 45 degrees from the
spring line. Tees may be oriented the in the same manner.
f. The service lead shall be placed so as to minimize the use of bends as
site conditions permit.
g. For existing residential lots (which are not served in accordance with
these guidelines) that need a service lead, if the distance to the
nearest existing sanitary sewer is less than 60 feet, the service lead
may be a 4 inch service tap if only one lot or parcel is to be served.
Commercial and industrial lots and parcels shall have a minimum 6
inch service tap under the same conditions.
h. The location where the service lead or its wye meets the property line
shall be shown on the plans and as-builts, and marked in the field
with a riser out of the ground. There shall be a riser placed where the
service lead meets the property line so that the service lead stub-out
can be recovered at the time that the connection to the service lead is
made. All service leads shall be extended to the property line and be
turned up (elbowed) to rise up above ground level a minimum of 2
feet. The end of the riser shall be sealed with a glued cap.
i. All service leads shall be installed at the time of the construction of
the sanitary sewer in new residential subdivisions.
F. General Requirements
1. A licensed plumber shall be responsible for connecting private residential
sanitary sewer service to the public sanitary sewer system, to wyes and/or tees or
to lateral sewers as indicated on the plans. Said licensed plumber shall be
responsible for a properly installed and watertight private residential service
connection.
2. Commercial service connections to the public sanitary sewer shall be made by
the City of La Porte.
3. Materials and construction shall conform to the City of La Porte Standard
Specifications and Standard Details where applicable.
4. All constructed sanitary sewer lines shall be air tested for leaks and a mandrel
pulled for structural defects. All sanitary sewer testing shall comply with or
exceed the procedures and qualifications listed in Texas Administrative Code,
Chapter 317, Section 317.2(a)(4)(B). A post construction video survey shall be
performed and video tapes provided to the City of La Porte before being
accepted by the city for maintenance.
5. All public sanitary sewers and service leads shall have bedding and backfill that
shall comply with or exceed City of La Porte Standard Specifications and
Details. Those sanitary sewers that are bore and jacked, m icrotunne led,
augured, or encased in a steel pipe may require special bedding and backfill.
a. Portland cement, Type I, ASTM C 150.
b. Clean, durable sand, with less than 0.5% clay lumps, ASTM C142;
with less than 0.5% lightweight pieces, ASTM C123; with organic
impurities, ASTM C40, not showing a color darker than standard color
and a plasticity index of less than 6 when tested in accordance with
ASTM 0423 and ASTM D424.
c. Compact to 95% Standard Proctor Density (ASTM D2922-78 and
ASTM D3017-78) in lifts of 8 inches thick. Actual testing may be
required as deemed necessary by the City of La Porte.
d. The cement-sand mixture shall consist of at least I ~ sacks of cement
per cubic yard of sand. The cement-sand mixture shall have a
minimum unconfined compressive strength of 100 psi in 48 hours when
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compacted to 95% of Standard Proctor Density (ASTM D2922-78 and
ASTM D3017-78), without additional moisture control, cured and
tested in accordance with ASTL C31.
6. Backfill excavated areas and trenches under or within one foot of existing or
proposed pavement with cement-stabilized sand. There shall be cement-
stabilized sand from the top of the pipe up to a maximum of one foot below the
paving subgrade.
7. The proposed location of any backfill other than cement stabilized sand backfill
shall be shown by stations in the drawings in both plan and profile views.
8. Public sanitary sewers and force mains shall be located in either the public right-
of-way or public easements. Side lot and back lot easements are discouraged
and should be avoided. Side lot and back lot easements may be granted special
approval only when a sanitary sewer located in the street right-of-way is
impossible from an economic and engineering standpoint.
a. Street Right-of-way
(1) Sanitary sewers with a depth of up to ten feet (10' measured
from finished grade), shall be placed within the right-of-way
at least 5 feet from the right-of-way line. Said sanitary sewer
should also be 5 feet from the paved area when achievable.
All sanitary sewers that are deeper than 10 feet shall be
centered in an exclusive public easement parallel to and
adjoining the street right-of-way. Where the City of La Porte
deems the need, the .Professional Engineer of Record may be
required to provide additional public easement adjoining the
street right-of-way to accommodate either horizontal or
vertical clearances.
b. Easements
(1) The maximum depth of a sewer in a side lot or back lot
easement shall be 8 feet where and if the use of side or back
lot easements are approved.
(2) Easements shall have a minimum of 2 access points for
maintenance purposes.
c. Lateral Location of Sewer in Right-of-Way/Easement
(I) The location of the sanitary sewer within a dedicated public
easement shall be along the centerline of the proposed public
easement or as close to the centerline as can be designed. In
those instances where the public easement is adjacent to the
public right-of-way, the lateral location of the sanitary sewer
shall be at the discretion of the Design Engineer with City
approval.
9. The final determination as to that portion of a street, alley, or public easement to
be occupied by a proposed sanitary sewer rests with the City. The City will take
into consideration existing, planned and proposed facilities such as manholes,
pavement, pipes/conduits, along with existing trees and shrubs, historical
features, wetlands or other unique surface conditions when arriving at a
decision.
10. The drawings of the sanitary sewer shall show the location of any existing pipe
or duct that might interfere with the construction of the sanitary sewer and call
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to the attention of the City any known obstacles that might be encountered in
constructing the sanitary sewer in any location under consideration. The
Professional Engineer of Record shall determine the existence of pipes, ducts,
obstacles and other utilities (i.e. gas, telephone, electric, fiber optic, cable, etc.)
from a visual survey on the ground plus research of the public records and
private records when available.
11. Sanitary sewers within the City of La Porte's jurisdiction shall be designed and
installed at such a size and depth as to allow for orderly expansion of the system,
so as to avoid duplication in the future, and shall conform with the
Comprehensive Wastewater Collection and Treatment Plan (1984) for the City
of La Porte (as amended where applicable).
12. Sanitary sewers shall be separated from water lines by a minimum of 10 feet of
horizontal clearance. See Chapter 3 Water System Design Criteria for water and
sanitary sewer crossing design criteria.
13. Sanitary sewers shall be separated from storm sewer lines by a minimum of 4
feet of horizontal clearance and the storm sewer line shall be above the sanitary
line where possible.
14. For sanitary sewers crossing utilities other than water or storm sewer (i.e. cable,
gas, fiber optic, power, etc.), a minimum of 6 inches of horizontal clearance
shall be maintained as measured from outside wall to outside wall.
G. Line Size
1. The minimum pipe diameter for a public sanitary sewer main or lateral sewer
other than a service lead shall be 6 inches.
2. Service leads 6 inches in diameter shall not serve more than the equivalent of 2
single family lots or other equivalent types of small land tracts.
3. Service leads for single family residential lots shall have a minimum grade of
0.10% for a 6 inch line. The average daily flow for the design of sanitary sewers
shall be based on a minimum of 1350 gallons per day per acre (GPD/AC) of
residential land, 6534 GPD/AC of commercial land and 9450 GPD/AC of
industrial land.
4. For commercial service leads such as street bores, the required size of the line
shall be established from the plumbing drawings. Commercial, industrial, and
office areas shall be designed for an average daily flow that can be anticipated
from the contributing area.
5. Commercial sewer service leads shall be 6 inch pipe or larger. A single 6 inch
commercial service connection shall not serve more than one commercial lot or
parcel. Four inch service leads for commercial developments shall not be
allowed.
6. Sewer mains and lateral sewers shall meet at a manhole. Sewer mains and
lateral sewers shall end in a manhole and may end in a cleanout with special
permission and approval from the City Engineer.
7. The City shall have final review and approval authority as to the size and depths
required for sanitary sewer mains and lateral sewers.
H. Line Depth
1. The sanitary sewer should be laid with the top of the pipe a minimum of 4 feet
below the surface of the natural ground or finished grade.
2. Sanitary sewers laid in street rights-of-way with a curb and gutter section shall
have a minimum cover of 4 feet from the top of the pipe to the flowline
elevation of the gutter in the street at all locations. The Professional Engineer of
Record shall account for any anticipated future sanitary sewer extension whereas
the future sanitary sewer extension shall have a minimum 4 feet of cover from
the top of the pipe to the flowline of the gutter of the street. The Professional
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Engineer of Record shall adjust the depth of the proposed pipe accordingly. The
City of La Porte reserves the right to require greater depth where the need is
perceived by the City.
3. Sanitary sewers laid in street rights-of-way with crowned roads and roadside
ditches shall have a minimum depth of 6 feet from the crown of the road to the
top of the pipe and an absolute minimum cover of2 feet below the flowline ofa
roadside ditch when non-rigid or pipes of low hoop strength are used. The City
of La Porte shall have final determination on any deviation from these criteria.
4. Where the cover over the pipe is less than 2 feet, the sanitary sewer shall be laid
with Class 150 pressure pipe, steel pipe or ductile iron pipe. Class 150 pressure
pipe must be laid with cement stabilized sand backfill in accordance with the
Standard Details. Ductile iron pipe maybe used but shall be lined with either a
polyethylene or polyurethane coating with manufacturer recommendation and
applied by the pipe manufacturer. The minimum liner thickness shall be 40 mil.
Other rigid pipe or pressure pipe will be considered for approval on a case-by-
case basis by the City Engineer.
5. Maximum depth for 8-12 inch diameter collection lines shall be 20 feet from
average ground surface to sanitary sewer invert. Depths greater than 20 feet
shall require the use of Class 150 pressure pipe with cement stabilized sand
backfill in accordance with the Standard Details. Ductile iron pipe may be used
but shall be lined with either a polyethylene or polyurethane coating with
manufacturer recommendation and applied by the pipe manufacturer. The
minimum liner thickness shall be 40 mil.
I. Line Grades
1. The following table lists the minimum grade for 6-inch to 39-inch diameter
public sanitary sewers. The recommended velocity for a sanitary sewer flowing
full shall be 2.0 feet per second (fps). The maximum recommended grade shall
be calculated by the Professional Engineer of Record for a maximum velocity of
4.5 fps based on a Manning equation for full flow with the Manning's "n" equal
to 0.013.
Table 4.1
MINIMUM GRADES FOR SANITARY SEWERS
PIPE SIZE MINIMUM GRADE (PERCENn
6 0.50
8 0.33
10 0.25
12 0.20
15 0.15
18 0.11
21 0.09
24 0.08
27 0.06
30 0.055
33 0.05
36 0.045
39 0.04
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2. For sanitary sewers larger than 39 inches in diameter, the Professional Engineer
of Record shall determine the appropriate grade utilizing a full pipe maximum
velocity of 4.5 fps and minimum velocity of2.0 fps.
J. Gravity sanitary sewers shall be lain in straight alignment with uniform grade between
manholes. Changes in grade without the use of manholes at the grade change shall not be
allowed. Deflection in sanitary sewer pipe runs shall never exceed manufacturer's
recommendation. The use of bends to achieve deflections in alignment are encouraged in
lieu of pipe deflections. All construction plans showing alignment change by use of
deflections are subject to review by the City Engineer.
K. Manholes
I. Type: Manholes shall be either precast concrete manholes in accordance with
standard details or the Professional Engineer of Record may submit a cast-in-
place manhole design for review and approval by the City. All concrete
manholes shall be coated with a coal tar epoxy to a thickness of 10 mil. or
thicker. Fiberglass manholes with precast, gasketed, concrete bottoms are
allowed outside paved areas where the manhole depth is designed to be 8 feet
deep or less. It shall be the responsibility of the Professional Engineer of
Record to ensure that the precast manholes conform to the latest ASTM
requirements. Manhole covers shall have the City of La Porte logo on them.
All manholes shall be installed with stainless steel or polyethylene manhole
inserts with 1/8 inch vents and strap handles.
2. Location: Manholes shall be placed at changes in alignment, changes in grade,
changes in size of sanitary sewers, at the intersection of sanitary sewers, junction
points, and either at street, alley, or easement intersections.
a. Sanitary sewers laid in public easements shall have a manhole in each
street right-of-way outside the paved section of the street crossed by the
sanitary sewer regardless of the manhole spacings mentioned in these
criteria.
b. The maximum distance between manholes shall be determined from the
following table for 6 inch to 39 inch pipe diameters. Spacings for
manholes on sewer mains with diameters larger than 39 inches shall be
recommended on an individual basis by the Professional Engineer of
Record subject to City of La Porte approval.
Table 4.2
MAXIMUM DISTANCE BETWEEN
SANITARY SEWER MANHOLES
PIPE DIAMETER IN INCHES MANHOLE MAXIMUM SPACING IN FEET
6-15 400
18-39 800
>39 Per PE of Record subject to City of La Porte
Approval
c. Place manholes at the dead-end of sewer mains and lateral sewers. A
clean out may be used with special permission and approval of the City
Engineer.
d. Manhole covers shall be cast iron, traffic bearing type ring and cover.
e. Criteria for Manhole Junctures
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(1) Connections between public sanitary sewers and the manhole
shall adhere to the following criteria.
(a) The elevation of the flowline of the discharging
sanitary sewer shall match the elevation of the
flowline of the receiving sanitary sewer for both
equal and unequal pipe diameters.
(b) Drop manholes are allowed. A drop connection or
drop manhole is required when the difference in
elevation between the effluent flowline and the
influent flowline is greater than 36 inches.
D. Manholes should be located as to minimize or eliminate the inflow of storm water into the
sanitary sewer. The top of manhole rim shall be set a minimum of 6 inches above the
surrounding finished grade when the manhole is not in a paved roadway. Sealed
manholes are required on all newly constructed manholes within the 1 OO-year flood plain.
Vented manholes are required a minimum of every 800 feet when not located in the
100-year floodplain. Under no circumstances shall the elevation of the top of rim of a
sanitary sewer manhole be below the 100-year base flood elevation for the area it is being
built in.
E. Manholes shall be constructed in accordance with the Standard Details where applicable.
All manholes shall include rubber seals precast into the manhole for pipe inserts or 3M
Scotch Seal 5600 and Oakum at all pipe connections (no Fosroc or cement) or approved
equal. Precast manholes shall incorporate a boot-type connector for sanitary sewer
diameters up to 24 inches. For sanitary sewer diameters greater than 24 inches, utilize
either the boot-type connector if available or an integral gasket.
F. Steps in manholes shall not be allowed.
G. All manhole adjustments shall be made with precast concrete rings when an additional
precast vertical section is too large.
H. All manholes shall be tested by the construction contractor and results provided to the
City of La Porte before being accepted by the city for maintenance. The City of La Porte
reserves the right to require retesting of manholes if there is reason to question the results.
All manhole testing shall comply with or exceed the procedures and qualifications listed
in Texas Administrative Code, Chapter 317, Section 317.2(c)(5)(H).
L. Lift Stations
I. Lift station design and construction drawings as wen as design requirements and
pertinent data shall be sealed by a Professional Engineer registered in the State
of Texas and submitted with the construction drawings for review by the City.
2. Lift Stations should be considered only when a gravity system cannot be
achieved from both an engineering and an economic standpoint. Lift stations
should only be considered with prior approval from the City of La Porte or
where the lift station is designed to be temporary in nature.
3. Lift station controls shall be enclosed and fenced in such a way to deter
unauthorized operation, vandalism and/or terrorism.
a. Controls and equipment shall be approved by the City. Pumps shall be
submersible type manufactured by Hydromatic, or Flygt, or approved
equal. Pump controls shall be manufactured by E.G. Controls or
Consolidated Electric, or approved equal.
4. Wet Wells
a. .Provide adequate clearance between pumps so as to easily facilitate
retrieval of a pump.
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b. Wet well working volume shall be sized to allow for the
recommended minimum pump cycle time of 10 minutes for each
pump.
5. Lift station site - Minimum size of 20 feet by 20 feet. Vehicular ingress and
egress access to the site shall be provided.
6. The lift station's control panel shall sit a minimum of 2 feet above the nearest
base flood elevation.
7. The top of concrete of the lift station's wet well shall sit a minimum of2 feet
above the nearest base flood elevation.
7. Pumps shall be sized to operate at optimum efficiency. Minimum acceptable
efficiency at the operating point shall be 60%.
8. Emergency operations should be considered. Provide fittings and a blind flange
that will be readily accessible for emergency bypass pump.
M. Design Analysis
1. Calculations of design flows for the overall development project shall be
provided to the City of La Porte.
4.04 QUALITY ASSURANCE
A. Prepare calculations and construction drawings under the supervision of a Professional
Engineer trained and licensed under the disciplines required by the drawing. The final
construction drawings must be sealed, signed, and dated by the Professional Engineer
responsible for the development of the drawings. Ifmore than one Professional Engineer
was responsible for the development of the design/construction drawings, then the
appropriate Professional Engineer should seal the drawings he is responsible for.
4.05UNSEWERED BUILDING SITES AND SEPTIC TANKS
A. It is the responsibility of the land owner to file a Citizen Developer Request (CDR) fonn
with the City to ensure that a site has sanitary sewer service available.
B. For unsewered building sites and building sites with no sanitary sewer availability, the
owner/developer will execute a utility extension agreement with the city. The
owner/developer must pay for all materials and affect installation and testing before the
city will accept the sewer for maintenance.
C. If a lot or parcel is within 200 feet of an existing sanitary sewer then the site shall tie-on
to the existing sanitary sewer. Such building shall comply with Section 74 Article 3 of
the City of La Porte Code of Ordinances.
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