HomeMy WebLinkAbout03/01/2005, SS 4 - STORM SEWER MANAGEMENT PLAN council °ac
03/01/2005
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CITY OF SAN LUIS OBISPO
FROM: Jay D. Walter; Public Works Director
Prepared By: Matt Horn, Associate E gineer
SUBJECT: STORM SEWER MANAGEMENT PLAN
CAO RECOMMENDATION
1. Receive the Storm Sewer Management Plan..
2. Direct staff to do further research on funding options and return with recommendations to the
Council after the current budget is finalized.
REPORT IN BRIEF
The City has an obligation under Federal law to reduce the pollutants being discharged into local
waterways through the storm sewer system. We also have an obligation as a responsible steward
of the environment and our infrastructure to properly maintain and replace components of our
storm sewer system. The stone sewer system is not to be confused with new flood control
improvements, but instead consists of the inlets, manholes and pipelines that drain our City
streets. Under the management plan, the City would proactively replace, repair, and maintain
existing storm sewer facilities before failure, systematically resolve historic flooding problems
and upgrade the system so that the chance of new flooding hazards is minimized.
This report outlines alternative strategies for replacement and maintenance of these facilities,
each requiring levels of funding that are not feasible in our current fiscal situation. The
alternatives involve the replacement and maintenance needs of the system, and range from a
schedule for total system replacement to only the most problematic facilities; and from a new,
full time effort to increase maintenance to a slight increase over current levels.
The ideal solution, in.staff's opinion,is to create a program similar to the Pavement Management
Plan, which provides a plan for work that is needed and a recommended funding level to
accomplish the goal. The Storm Sewer Management Plan outlines a plan to replace the entire
system on a certain funding cycle, and provides an increased level of maintenance effort to do a
better job of removing silt and debris from the system before it can reach local waterways.
The major challenge for accomplishing the goals of the plan is a lack of available funding. The
options for raising the needed funds for any enhancement in our program are outlined in the
report. But it should also be noted that given our current fiscal constraints, revenue raising
restrictions, voting requirements, and potentially competing ballot measure options in the City
and County make funding this plan a challenging exercise for the Council.
With this report, staff hopes to at least thoroughly brief the Council on the current state of the
City's storm sewer system, the replacement and maintenance needs, and to get some preliminary
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direction on desired service levels and funding approaches. We realize that any significant
progress must be deferred until such time as our larger General.Fund problem is addressed and
future opportunities and constraints are better known.
DISCUSSION
Why do we need a Storm Sewer Management Plan?
In 1999, the US Environmental Protection Agency issued orders that cities and counties must
comply with the National Pollutant Discharge Elimination System (NPDES) Phase H
requirements of the Clean Water Act. Those orders require the City to submit a Notice of Intent
and a plan of compliance to the Regional Water Quality Control Board (RWQCB). These
regulations require ongoing activities to reduce the level of pollutants discharged from storm
drainage systems into natural waterways. As part of the requirements of NPDES H, the City
must develop, implement, and enforce a Storm Water Management Plan (SWMP). This SWMP
outlines Minimum Control Measures, Best Management Practices, and Measurable Goals to
gauge how well the City is complying with the NPDES requirements. On November 19, 2002
City Council approved the City's SWMP, and it was submitted to the RWQCB on March 10,
2003. The City's SWMP recommends the development of a Storm Sewer Management Plan as
part of a long-term strategy to address urban runoff.
Of primary importance is to develop a system in which these facilities are prioritized for
maintenance, replacement, and improvement to address system deficiencies. It is intended with
the use of this management plan that the City will transition from a reactive replacement strategy
to a proactive plan of system improvements. Under the plan, the City will proactively replace,
repair, and maintain existing flood control facilities before failure; systematically resolving
historic flooding problems while minimizing the possibility of new flooding hazards being
created.
How bad is the problem?
The entire stone drain system (manholes, inlets and pipes) was inspected and evaluated for its
overall condition in 2001. About 20% of the manholes and inlets that were surveyed were found
to be in need of repair or replacement, and about 25% of the pipes surveyed were of a material
type that no longer conforms to City standards and should be replaced, based on known
performance problems. A more detailed description of the criteria used for the evaluation of the
inlets, manholes and pipes is included in the management plan text.
From a flood capacity standpoint, the system was evaluated and analyzed using the latest
hydraulic analysis software. It was determined that about 65% of the drainage sub systems could
handle the flow from a 100 year storm event, but that about 25% of the systems could pass no
more than a 10 year event.
How has this need been handled in the past?
A Drainage Inlet Replacement Program was first approved in the 1985-1987 Financial Plan.
Since then, several projects were approved to replace drainage inlets, and currently, the Drainage
Inlet Replacement Program allocates $50,000 annually from the Street's Maintenance Operating
Budget to upgrade substandard drainage inlets. The City funds storm sewer system replacements
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Storm Sewer Management Plan Page 3
on a project specific basis. The City's most recent storm sewer system replacement was
approved in the 2001-2003 Capital Improvement Plan (CIP) Budget and completed for
approximately $110,000, replacing an undersized drainage system in the intersection of Morro
and Monterey Streets. The Public Works staff continues to submit capital improvement projects
requests on an as needed basis to compete with other projects for CIP allocation.
The City's Public Works and Utilities crews perform annual storm sewer maintenance activities.
The Wastewater Collections crew cleans drainage inlets in the downtown core, spending
approximately 70 staff hours of time over a three-week period. They also remove accumulated
sediments and debris from the Johnson Ave Underpass Lift Station in the fall, so that the storage
box has maximum capacity to hold water and keep the roadway from flooding. The Streets
Maintenance crew cleans drainage inlets and culverts citywide as identified by staff or citizens.
Typically, these drainage inlets have become blocked by large amounts of sediment that has
greatly reduced the inlet's capacity to accept water. Removing sediment and debris also has the
beneficial effect of keeping that material from being deposited in the creeks during periods of
heavy runoff.
What choices do we have to solve the problem?
The Storm Sewer Management Plan discusses three different types of system replacement
alternatives and two different maintenance alternatives. All proposals require different levels of
funding and staff time. The system replacement alternatives propose varying strategies for
achieving replacement of the failing storm sewer system components over time, similar to what
the Utilities Department does with the water and sewer systems. The maintenance alternatives
propose a higher level of annual maintenance that would bring us more into compliance with the
requirements of the NPDES II plan, with a greater emphasis on removing debris and sediment
before it is flushed down into the local waterways.
System Replacement Alternatives
Alternative 1: Total System Replacement
The total system replacement alternative recommends that the City selects a replacement cycle
period for a complete replacement of all storm sewer system components and fund accordingly.'
The replacement cycle in years corresponds to the length of time the system will remain in place
and operational. For example, if the City funds stone sewer replacements at a 75-year level, in
theory, no newly installed drainage facility would remain in service longer than 75 years. In
practice, systems may remain in service longer if the structural condition or hydraulic capacity
does not warrant replacement. This is similar to the rationale used for sewer and water utilities.
Sewer and Water utilities fund at a 50-year replacement cycle. Below is a table relating system
replacement cycle lengths to required annual funding and staffing requirements.
Replacement Cycle Annual CIP Funding Annual Engineering& Inspection
Requirements Staff Hours
25 Years $3,000,000 7500
50 Years $1,500,000 4000
75 Years $1,000,000 2500
Storm Sewer Management Pian Page 4°
100 Years $750,000 2000
150 Years $500,000 1500
200 Years $375,000 1000
500 Years $150,000 500
Funding could be adjusted yearly to reflect increases or decreases in replacement needs and
increases in cost due to inflation. Annual funding will be used as needed to replace inlets,
manholes,pipelines and street crossing culverts.
Advantages of Alternate 1: Total System Replacement
The advantages of the Total System Replacement alternative are that it uniformly addresses
system requirement throughout the City. The Total System Replacement alternative is a long-
term way to address localized flooding problems and an aging infrastructure.
Disadvantages of Alternate 1: Total System Replacement
The disadvantages of the Total System Replacement alternative are that it is very expensive and
could take a long time to accomplish. It also requires a large amount of staff time for design and
inspection.
Alternative 2: Corrugated Metal Pipe (CMP)Replacement
About 25% of the Storm Sewer System is composed of CMP, a type of pipe that has achieved
minimal service life, commonly rusting through at the bottom and allowing surrounding soil to
be carried away. The CMP system replacement alternative recommends that the City selects a
replacement cycle period and fund accordingly. The replacement cycle in years corresponds to
the length of time until the City has replaced its entire existing CMP infrastructure with more
durable materials. The management plan is recommending a replacement cycle of 25 years. In
theory that would mean all existing CMP facilities will have been replaced in that 25-year period.
CMP Replacement Cycle Annual CIP Funding Annual Engineering/Inspection
Requirements Staff Hours _
8 Years $1,738,000 4200
10 Years $1,400,000 3600
20 Years $725,000 1800
25 Years $590,000 1500
50 Years $320,000 800
Advantages of Alternative 2: Corrugated Metal Pipe (CMP) Replacement
The advantages of the CMP Replacement alternative are that it focuses funding on the most
probable source of system failures. The CMP Replacement alternative is a long-term strategy to
address storm sewer system material failures. The CMP Replacement alternative requires less
funding than the Total System Replacement alternative.
Disadvantages of Alternative 2: Corrugated Metal Pipe (CMP) Replacement
Storm Sewer Management Plan Page 5
The disadvantages of the CMP Replacement alternative are that it only funds replacement of
systems that are comprised of corrugated metal pipe. The CMP Replacement alternative will not
address capacity problems in non-CMP systems.
Alternative 3:System Replacements for Historic Hooding/Failure Sites
Currently the City spends approximately $50,000 a year to fund drainage inlet replacements and
$50,000 a year to fund silt removal projects. The historic flooding alternative recommends
continuing with the same funding but augmenting it with an additional $1.50,000 per year to fund
selected system replacements that address historic flooding/capacity problems. This would bring
the total funding for this work to $250,000 a year. This alternative could also be considered as
an interim solution intended to fund the system replacements at a minimum level until additional
funding becomes available and one of the previously mentioned long-term alternatives could be
implemented.
Advantages of Alternative 3: System Replacements for Historic Flooding/Failure Sites
The advantages of the System Replacements for.Historic Flooding/Failure Sites alternative is that
it allows funding to be directed both at system failures as well as capacity issues identified
throughout the City. The System Replacement for Historic Flooding/Failure Sites alternative is
the least expensive and the least demanding on staff time of all alternatives presented, but still
presents some measurable progress towards a goal of system replacement.
Disadvantages of Alternative 3: System Replacements for Historic Flooding/Failure Sites
The disadvantages of the System Replacements for Historic Flooding/Failure Sites alternative are
that it is not intended to be a long-term strategy to address flooding and an aging infrastructure.
Pipe failures and flooding problems would still persist to some degree, and would be more
difficult to solve given the limited funding.
System Maintenance Alternatives
Alternative 1: Total System Maintenance
The Total System Maintenance alternative would provide resources for City Street Maintenance
staff to clean every one of the City's 2100 drainage inlets at least once a year, some more often.
This alternative would require 3150 hours of staff time a year, and would provide for a program
to proactively clean the inlets, reducing the amount of trash, debris and sediment that are flushed
into the creek system.
For the City to accomplish this level of maintenance, additional staff and equipment would be
required. Two new staff positions will be needed to offset the additional maintenance work and
a Vactor truck will be required to adequately clean the inlets and pipe sections.
Annual Funding Requirements
2 Staff positions $138,000
Vactor Truck Maintenance $10,000
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Storm Sewer Management Plan Page 6
Funding Requirements for Equipment Purchase 8 Year Life Span)
Vactor Truck_ $ 250,000
Advantages ofAlternative 1: Total System Maintenance
The advantage of the Total System Maintenance alternative is that it addresses maintenance
requirements of the storm sewer system throughout the City. Thisalternative is the best method
to reduce the amount of trash, sediment and debris from entering the City's storm sewer system
and eventually local waterways. It provides for the highest level of compliance with the NPDES
II requirements and fulfills a commitment made in the City's Storm Water Management Plan.
This alternative is the best way of keeping the City's storm sewer system functioning as
designed.
Disadvantages of Alternate 1: Total System Maintenance
The disadvantage of the Total System Maintenance alternative is that it is an expensive effort and
requires the purchase of equipment to do the work properly.
Alternative 2:Select Maintenance
The select maintenance alterative would require City staff to clean select drainage inlets in the
more debris prone areas of the City (near Cal Poly, San Luis High School, Foothill Boulevard
and key creek corridors). This alternative would require at least 500 hours of staff time a year
and is intended to lessen the amount of trash and debris that could be flushed into the creek
system.
The City can accomplish this level of maintenance service by utilizing existing maintenance staff
and working on weekends. Focusing on a six-week period prior to the rainy season(October 15),
existing maintenance staff would work overtime and weekends to clean these select drainage
inlets. By working outside of normal hours, it might also be possible to utilize the Wastewater
Collections Vactor truck. The possibility of hiring an outside contractor with a vactor truck is an
option if the Collections crew is not available.
Annual Funding Requirements
Streets Maintenance Worker Overtime _$25,000
Vactor Truck Rental $30,000
Total $55,000
Advantages ofAlternative 2: Select Maintenance
The advantages of the Select Maintenance alternative is that it focuses staff time and City
resources for minimum maintenance requirements. The Select Maintenance alternative is the
least expensive option and the least demanding of staff time during normal working hours.
Disadvantages ofAlternative 1: Select Maintenance
The disadvantages of the Select Maintenance alternative are that it does not fully comply with the
City's NPDES II plan. It maintains only known problem areas and does not focus the same level
of maintenance throughout the City.
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Stone Sewer Management Plan Page 7
Summary
Given the age of the City's existing storm sewer system it is important to have a long term plan
in place in order to protect the City's previous infrastructure expenditures. Additionally, with a
thorough storm sewer maintenance plan, much of the trash, sediment and debris can be collected
and disposed of before it is allowed into our creek system. Therefore, Staff preference would be
for the Total System Replacement and Total System Maintenance alternatives using a 75 year
replacement cycle. With this recommended level of maintenance and recommended level of CIP
funding, annual demands on staff time will increase approximately 6150 hours (2500 for
Engineering and Inspection, 3150 hours for drainage inlet maintenance and 500 hours for
maintenance staff inspection). This work effort is equivalent to three new, full time City
employees, one a Public Works Inspector and two Streets Maintenance.Personnel. The funding
levels for this recommendation would be:
Annual Funding Requirements
Yearly CIP Funding 75 Year Cycle) $1,000,000
Program Operating Costs $50,000
One Public Works Ins ector $85,000
Two Streets Maintenance Workers $138,000
Total $1,273,000
Funding Requirements for Equipment Purchase
Vactor Truck $250,000
CONCURRENCES
The plan has been reviewed by the Utilities Department and Public Works Staff and has received
support for the concept and concurrence that it will help the City achieve compliance with the
NPDES H requirements.
FISCAL IMPACT
How could this work be funded?
The General Fund primarily funds maintenance of City infrastructure. Past and current projects
such as drainage inlet replacements, storm drain repairs, silt removal, street reconstruction, slung
seals and other similar projects all take their own share of General Fund dollars. The Stone
Sewer Management Plan projects would need to be prioritized along with the other types of
projects and be competitive for the same dollars. The bottom line at this time is that there is no
extra funding for this program. It must become recognized as a need for the City to focus
resources on and as a requirement of our Storni Water Management Plan obligations under
NPDES U.
The Financing Plan section of the Storm Sewer Management Plan details options other than
General Fund for these improvements. For example, funding is currently available to the City
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Storm Sewer Management Plan- Page 8
from the San Luis Obispo County Flood Control and Water Conservation District Zone 9
Advisory Committee for creek cleaning and maintenance. It is unlikely that it will ever provide
more than the $100,000 in funding that it currently provides; which is far from adequate to fund
the needs identified in this plan. Another complicating factor to using Zone 9 fonds is that the
State has informed the County that it intends to take the property tax revenue ($100,000 per year)
for the next two years, leaving Zone 9 to operate only on its reserve funds.
Another option would be to create a Storm Sewer Enterprise Fund. Similar to the water and
sewer funds already in place in the City, where user fees cover the full cost of the programs, the
City could establish a storm sewer enterprise fund. In fact, the City did so in 2002 when the
Creek and Flood Protection Fund was created, albeit briefly. This option would cover funding for
both waterways and storm sewers in meeting the City's flood protection needs. Very soon after
the Council acted to create the new fund, a court decision was reached involving the City of
Salinas and the funding mechanism they created for their NPDES requirements. The City's
planned assessment was found to be property related, and as such, should have been approved by
a vote of the people. The City Attorney at the time pointed out that the new Creek and Flood
Protection Fund was vulnerable to a similar judgment and the Council acted to reverse their
previous decision..
A third option would be to create an Assessment District. While structurally different from an
enterprise fund with user fees, the practical result is the same. For example, instead of a $4.50
per month user fee for single-family residences, there could be a $4.50 per month assessment.
The approval process is also very similar to that for an enterprise fund. Assessment revenues
would be collected on the property tax roll. To utilize this option, an Assessment District would
have to be created by a vote of those affected property owners.
Finally, a Special Purpose Tax could be created. With the exception of ad valorun property
taxes (which are strictly limited to 1% of market value under Proposition 13), the City can
impose new or added taxes in a wide range of areas, including sales taxes, parcel taxes, real
property transfer taxes, utility users taxes, transient occupancy taxes and business taxes. For this
option to take effect, a supermajority(2/3) vote of the people is required.
All of the financing options are discussed in greater detail in the Storm Sewer Management Plan.
ATTACHMENTS
Storm Sewer Management Plan
AVAILABLE FOR REVIEW IN THE COUNCIL OFFICE
Appendix A— Watershed
Appendix B—Replacement Cost
Appendix C—Hydraulics
B Council Agenda Reports\2005 agenda reports\Engineering and Maintenance.Services(Walter)\Capital Projects Design(Lynch)\Storm Sewer
Management Plan CAR.DOC
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ATTR' �`HMENT 1
STORM SEWER MANAGEMENT PLAN
FEBRUARY 2005
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Prepared by:
Jay Walter,Director of Public Works
Barbara Lynch,Civil Engineer
Matt Horn,Associate Engineer
Public Works Department
City of San Luis Obispo
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STORM SEWER MANAGEMENT PLAN
Table of Contents
PURPOSE.......:...............:...........:....................................................................................... 1
CURRENT STORM SEWER MANAGEMENT EFFORTS............................................. 1
INVENTORY ANALYSIS................................................................................................. 1
SYSTEM CAPACITY....................................................................................................2
HYDROLOGY...........................................................................................................:2
HYDRAULICS...........................................................................................................3
RESULTS....................................................................................................................3
SYSTEMCONDITION..................................................................................................3
STORMSEWER STRUCTURES..:...:...:...................................................................4
PIPELINES .....................................:.:.........:...:...........:.......:.......................................4
SYSTEMVALUE...........................................................:......o........:.........::...................5
FINDINGS..........................................................................................................................5
SCOPE............................................................................................................................5
INSPECTION..................................................................................................................6
SEQUENCING...............................................................................................................6
CAPITAL IMPROVEMENT PLAN...............................................................................8
RANKING CRITERIA...........................::..............:...............:.....................................8
ONGOINGWORK.................................................................................................:.......8
ALTERNATIVES...........................................................................................................9
A. SYSTEM REPLACEMENT METHODOLOGIES............................................9
Al. TOTAL SYSTEM REPLACEMENT METHODOLOGY.........................9
A2. CMP SYSTEM REPLACEMENT METHODOLOGY........................... 10
A3. HISTORIC FLOODING/FAILURE METHODOLOGY......................... 10
B. MAINTENANCE METHODOLOGIES ............:............................................. 10
B 1. TOTAL MAINTENANCE METHODOLOGY......................:...:.......:.... 10
B2. SELECT MAINTENANCE METHODOLOGY...........................:.......... 1 I
RECOMMENDED PROGRAM................................................................................... 1 I
Appendix
A Watershed
B Hydraulic
C Replacement Cost
Storm Sewer Management Plan
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STORM SEWERMANAGEMENT PLAN
PURPOSE
The Storm Sewer Management Plan is intended to be a long-term strategy to address the
maintenance, rehabilitation and capacity improvements for the facilities that carry urban
runoff. Of primary importance is to develop a system in which these facilities are
prioritized for maintenance, replacement, and improvement to address system
deficiencies. It is intended with the use of this management plan the City will transition
from a reactive replacement strategy to a proactive plan of system improvements.
Proactively replacing, repairing, and maintaining existing flood control facilities before
failure; systematically resolving historic flooding problems while avoiding the creation of
new flooding hazards.
CURRENT STORM SEWER MANAGEMENT EFFORTS
A Drainage Inlet Replacement Program was first approved in the 1985-1987 Financial
Plan. Since then, several projects were approved to replace drainage inlets, and currently,
the Drainage Inlet Replacement Program allocates $50,000 annually from the Street's
Maintenance Operating Budget to upgrade substandard drainage inlets. The City funds
storm sewer system replacements on a project specific basis. The City's most recent
storm sewer system replacement was approved in the 2001-2003 Capital Improvement
Plan(CIP)Budget and completed for approximately $110,000, replacing an undersized
drainage system in the intersection of Morro and Monterey Streets.
Current annual maintenance activities are provided by the City's Public Works and
Utilities Departments. The Utilities department cleans drainage inlets in the downtown
corridor spending approximately 70 staff hours of time over a three week period. The
City's Streets Maintenance Staff clean additional drainage inlets and culverts on a case-
by-case basis as identified by staff or citizens. These additional drainage inlets are
usually cleaned because large amounts of sediment have blocked or have greatly reduced
the drainage inlets capacity to accept water.
INVENTORY ANALYSIS
In order to complete the Storm Sewer Management Plan, the City's existing storm sewer
system was surveyed using a Global Position System(GPS) and mapped using a
Geographic Information System(GIS). A database of horizontal and vertical locations,
material, structure type, structural condition, and photos were collected for all accessible
structures. Even though this mapping represents a large work effort, the data represents
planning level accuracy only. Pipeline runs are schematic. Only 77% of all features
were physically surveyed. Pipeline materials and conditions are only known at storm
system access points (manholes and inlets). Record engineering drawings were used to
supplement portions of the unknown information. Historic data was also collected with
respect to storm sewer deficiencies.
The value of GIS mapping for the storm sewer system is large. GIS was chosen over
other mapping methods (mainly CAD or Computer Aided Drafting) because of its ability
to:
1. store additional relevant data;
Storm Sewer Management Plan
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2. interrelate other associated documents and;
3. integrate with other existing data sets and applications.
By creating the this data set, the Storm Sewer Management Plan envisioned:
1. creating the necessary building blocks for future enhancements;
2. collecting the data once and sharing it with others and;
3. creating a centralized model where changes to the system could be easily
analyzed locally as well as Citywide.
The storm sewer GIS map may be viewed on the City's local network at
\\gis\gisdata\ built\StormDrain\sd map.mxd.
SYSTEM CAPACITY
A hydraulic analysis was performed on City owned drainage facilities. This planning
level analysis was completed in order to rate City facilities based on standard hydrologic
criteria.
HYDROLOGY
Hydrology is a science related to the occurrence and distribution of natural water on the
earth. The portion of hydrology that is most important to the Storm Sewer Management
Plan is the estimation of peak flows.
The goals of the analysis portion of the Storm Sewer Management Plan are to identify
restrictions throughout the system and then use this information to help prioritize
replacements. Once a restriction is identified, a replacement design would then be
completed. The analysis watersheds were developed using the City aerial photo and
existing 0.5 meter contour interval lidar topo. In undeveloped areas the analysis watershed
delineation are of design quality. Developed areas(i.e. street areas) should be reanalyzed
by the design engineer during design using more detailed topographic information.
Analysis flows were either calculated or obtained using HEC-HMS (Hydrologic
Engineering Center—Hydrologic Modeling System), HEC-RAS (Hydrologic Engineering
Center—River Analysis System),or Area Proration. The Area Proration method relies on
the existing calibrated hydraulic model prepared by Questa Engineering for the Waterway
Management Plan. This methodology takes 61 watersheds and divides them into
approximately 2000 watersheds. Taking an area ratio and multiplying it by the total flow
from the Questa watershed quantified the flows from the subwatersheds..
(Asub Watershed/AQuesta Watershed) * QQuesta Watershed=QSn=11 Watershed
Asub watershed=Area of subwatershed
AQue,.Wa,ershed=Area of original watershed
QQuesra wa,ershed=Flow of original watershed
QSmall watershed=Flow of subwatershed
See Appendix A for watershed delineation and estimated flows.
Storm Sewer Management Plan
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HYDRAULICS
Hydraulics is the physical science of the static or dynamic behavior of fluids. For the Storm
Sewer Management Plan,the hydraulic analysis performed quantified the amount of runoff,
which can be conveyed through a given structure with respect to the statistical probability of
such an event occurring. Each analyzed system was given a 1, 2, 10,25,50, 100,or 200
year value corresponding to the largest event that this system could pass.
Computer software used to perform these calculations was dependent on the types of
drainage system. StormCAD,by Haestad Methods, was used to perform pipeline system
calculations. CulvertMaster,by Haestad Methods,was used perform minor street cross
culvert capacity analysis. Our existing HEC-RAS model was used to analyze all other
culvert/bridge capacities where existing Army Corps of Engineers reports were not
available. See Figure 2 for Major Channel Model Flow information and Appendix B for
hydraulic calculations.
RESULTS
Maximum Hydrologic Event Percentage of City Owned
Drainage Facilities
Will pass less than 2 Year event 2%
Will pass a 2 Year event 12%
Will pass a 10 Year event 10%
Will pass a 25 Year event 7%
Will pass a 50 Year event 5%
Will pass a 100 Year event 64%
A direct conclusion stating that some percentage of these storm sewer systems meet or do
not meet City standards is not available given the analysis that was performed and the
standard hydrologic criteria that was applied. Since City standard closed conduit flow
requirements are directly related to the associated street's flow capacity, a direct
conclusion is not available until a design analysis is performed. The City now knows
which systems can successfully pass greater flows based on their tributary area. This
information coupled with other information will help determine which systems should be
enhanced and where the major system deficiencies exist.
SYSTEM CONDITION
Drainage structures were rated on standard criteria as to the working order and observed
structural condition. Each structure was given either an excellent, good, fair, poor or
unknown assessment. Criteria for rating drainage structures were:
• Excellent—The structure is in pristine condition (typical condition of a newly
installed facility).
• Good—The structure is in above average working order. Lids and grates display
minor signs of wear. Concrete does not have any visible signs of cracking or
fatigue.
• Fair—The structure is in working order. Lids and grates show a greater degree of
wear but are in working order and concrete has some cracking.
Storm Sewer Management Plan
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• Poor—The structure is near the end of its design life. Lids and grates are
damaged or not working properly, concrete has cracking or has failed.
• Unknown—Unable to visual inspect structure due to locks,bolts,traffic or safety
concerns.
STORM SEWER STRUCTURES
The results of the inventory for structural condition on storm sewer structures:
Structure Type Percentage of Total Condition
44% Excellent
37% Good
Storm Sewer Manholes 13% Fair
1% Poor
5% Unknown
33% Excellent
48% Good
Drop Inlets 16% Fair
2% - Poor
1% Unknown
The results of the structural inventory for the storm sewer structures are positive.
Contributing factors to these results are:
1. Drainage Inlet Replacement/Rehabilitation Program
2. Public Visibility: Drainage inlets are the most visible portion of the storm sewer
system. When these facilities are not operating at maximum efficiency, the
ramifications (siting water and localized flooding) are usually reported
immediately either by staff or the general public.
PIPELINES
Pipeline conditions are not expected be as positive. Pipeline conditions are known at
storm system access points(manholes and inlets) only. Pipeline conditions can vary
dramatically from section to section; therefore, an overall pipeline condition can not be
reported without a much more intensive inspection that is beyond the current City
resources.
The results of the inventory for pipeline material as determined from storm system access
points:
Pipeline Material Percentage of Total System Length
Concrete 46.5%
Corrugated Metal Pipe (CMP) 22.4%
High Density Polyethylene (HDPE) 13.9%
Polyvinyl Chloride (PVC) 13.4%
Iron/Steel Pie 2.0%
Brick/Stone 0.6%
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Clay 0.4%
Unknown 0.7%
The results of the pipeline material inventory indicate that approximately one quarter of
the City's storm sewer pipeline system is comprised of non City Standard materials. A
large portion of these non-standard materials are CMP. This isnot a surprise since a
large portion of the City's existing storm sewer system was designed and installed in the
1970's and 1980's. At that time,CMP was the industry standard due to its inexpensive
material cost and ease of installation. Since then, CMP has proven to have a design life
of 20 to 30 years. CMP typical fails by friction, corrosion or both. Friction dissolves the
flow line of the pipe while corrosion weakens the entire pipe. Once the integrity of the
pipe has been compromised,the pipe's surrounding soil becomes susceptible to piping
(soil picked up by flowing water and carried away) and the pipe will eventually collapse.
A recent local example of this failure scenario is the Foothill Bridge failure in March
2001. While the exact age of all the City's CMP facilities is not known, all CMP
facilities in the City should be targeted for replacement.
SYSTEM VALUE
On October 22, 2003 the City received its final Governmental Accounting Standards
Board (GASB) 34 report which among other items reported the estimated values of the
City's storm sewer system. This report estimates the current value of the storm sewer
system as $6,586,730 with a current replacement cost of$12,338,587. These numbers
were reviewed and found to have limited value due to the fact that the GASB 34
methodology only places value and cost on drainage facilities that have been installed
after 1980.
A revised current replacement cost has been developed using all City owned drainage
facilities irrespective of installation date and actual replacement costs from recent City
funded projects.
Structure Type Replacement Cost
Pipeline $63,000,000
Inlets $10,000,000
Manholes $2,000,000
Total System Replacement Cost $75,000,000
See Appendix C for estimated replacement costs.
FINDINGS
SCOPE
The Storm Sewer Management Plan will include all City owned facilities that convey
runoff and require maintenance. Examples of such items are drop inlets, storm sewer
manholes, pipeline, street crossing culverts. These items will have criteria and
methodology for the prioritization of replacement, repair, and.maintenance.
Storm Sewer Management Plan
Page 5
y-15
i
INSPECTION
Each year data will need to be acquired in order to help prioritize which structures are
replaced, repaired or cleaned. Yearly data acquisition in an area of the City will begin
with visual inspection. City street's maintenance staff trained in confined space entry
will visually inspect all pipes at manholes, drop inlets or other convenient points of
access in a given area. Typically, these areas will coincide with the pavement
management area limits and precede pavement work. After the structures are visually
inspected, lines requiring maintenance will be cleaned. Cleaned lines will then be re-
inspected in order to obtain the structural condition of the pipeline. Using the results of
the structural condition inspection, the worst lines will then be video inspected.
SEQUENCING
The City's Pavement Management Program divides the City into nine different areas for
street repair and rehabilitation. On an eight year rotation, one area per year is inspected
and work in that area is completed in order to repair deficient streets. The City's Streets
Maintenance Division maintains the ninth area, the downtown. Pipeline work, excluding
Street Crossing Culverts, affecting streets would use similar areas and the same rotational
concept to minimize cutting of newly paved streets. The downtown area will be included
with the fifth pavement management area, and analyzed and maintained at the same time.
See Figure 1 for Storm Sewer Management Plan Maintenance Area locations.
'Storm Sewer Management Plan
Page 6
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CAPITAL IMPROVEMENT PLAN
There are two basic types of systems that the Storm Sewer Management Plan will
include.
1. Pipeline
2. Street Crossing Culverts
Pipeline systems can best be described as systems that are comprised of drop inlets,
manholes and the underground pipes that connect them. Street crossing culverts are
closed conduit or box culverts, not considered bridges, which convey concentrated flows
of a natural waterway under roads..
RANKING CRITERIA
Criteria for ranking systems replacements and deficiencies shall be based on three
factors.
1. Pipeline Structural Conditions (obtained via Inspection Reports)
2. Historic Flooding Sites
3. Hydraulic Capacity Deficiencies
Pipeline structural conditions shall be the most important criteria for ranking system
replacements. Pipeline conditions revealed by video reports will serve as a first indicator
of possible structural failure. Focusing funding on systems that are near structural failure
will reduce the future need for emergency funded projects and allow the City to more
precisely control storm sewer expenditures. As poor structural conditions are replaced,
new systems will be designed to eliminate hydraulic deficiencies and flooding. If
multiple lines rank the same, systems with a larger tributary area shall receive higher
priority.
Street Crossing Culvert replacements shall be prioritized in order to replace failing or
undersized culverts starting at the downstream portion of the City and working up.
Coordination with the Pavement Management Plan will be required, but these types of
system replacements will not follow the Pavement Management Program Maintenance
Area schedule because of the necessity to sequence projects based on their position along
the stream.
ONGOING WORK
The mapping and associated database should never be considered complete. These tools
will require yearly maintenance and augmentation to remain useful. Areas of
maintenance would include the addition of new storm sewer systems as constructed or
revisions to existing systems as completed. An area of augmentation that should be
considered is the mapping of detention basins.
Detention basins should be mapped for a more complete inventory of drainage features in
the City. Although small detention basins are not of high importance for larger
hydrologic studies, collecting this information will allow the City to have a centralized
database with ownership, capacity, outflow and maintenance activities records.
Storm Sewer Management Plan
Page 8
CAPITAL IMPROVEMENT PLAN
There are two basic types of systems that the Storm Sewer Management Plan will
include.
1. Pipeline
2. Street Crossing Culverts
Pipeline systems can best be described as systems that are comprised of drop inlets,
manholes and the underground pipes that connect them. Street crossing culverts are
closed conduit or box culverts, not considered bridges, which convey concentrated flows
of a natural waterway under roads.
RANKING CRITERIA
Criteria for ranking systems replacements and deficiencies shall be based on three
factors.
1. Pipeline Structural Conditions (obtained via Inspection Reports)
2. Historic Flooding Sites
3. Hydraulic Capacity Deficiencies
Pipeline structural conditions shall be the most important criteria for ranking system
replacements. Pipeline conditions revealed by video reports will serve as a first indicator
of possible structural failure. Focusing funding on systems that are near structural.failure
will reduce the future need for emergency funded projects and allow the City to more
precisely control storm sewer expenditures. As poor structural conditions are replaced,
new systems will be designed to eliminate hydraulic deficiencies and flooding. If
multiple lines rank the same, systems with a larger tributary area shall receive higher
priority.
Street Crossing Culvert replacements shall be prioritized in order to replace failing or
undersized culverts starting at the downstream portion of the City and working up.
Coordination with the Pavement.Management Plan will be required,but these types of
system replacements will not follow the Pavement Management Program Maintenance
Area-schedule because of the necessity to sequence projects based on their position along
the stream.
ONGOING WORK
The mapping and associated database should never be considered complete. These tools
will require yearly maintenance and augmentation to remain useful. Areas of
maintenance would include the addition of new storm sewer systems as constructed or
revisions to existing systems as completed. An area of augmentation that should be
considered is the mapping of detention basins.
Detention basins should be mapped for a more complete inventory of drainage features in
the City. Although small detention basins are not of high importance for larger
hydrologic studies, collecting-this information will allow the City to have a centralized
database with ownership, capacity, outflow and maintenance activities records.
Storm Sewer Management Plan
Page 8
4/
Detention basin mapping should be gradually obtained on a yearly basis as maintenance
and structural conditions are ascertained for project selection. Additionally, as video
reports are obtained, pipeline mapping shall be revised to more accurately represent
existing conditions.
ALTERNATIVES
The Storm Sewer Management Plan is proposing three different types of system
replacement methodologies and two different maintenance methodologies. It is the intent
of the Storm Sewer Management Plan that one replacement methodology and one
maintenance methodology be selected, funded and implemented. All proposals require
different levels of funding and staff time.
A. System Replacement Methodologies
1. Total System Replacement Methodology
2. CMP System Replacement Methodology
3. Historic Flooding/Failure Methodology
B. Maintenance Methodologies
1. Total Maintenance Methodology
2. Select Maintenance Area Methodology
A. SYSTEM REPLACEMENT METHODOLOGIES
ALTOTAL SYSTEM REPLACEMENT METHODOLOGY
The total system replacement methodology recommends that the City selects a
replacement cycle period and fund accordingly. The.replacement cycle in years
corresponds to the length of time each system will remain in place and
operational. Therefore, if the City funds storm sewer replacements at a 100 year
level, in theory, no newly installed drainage facility shall remain in service longer
than 100 years. In practice; systems may remain in service longer if the structural
condition or hydraulic capacity does not warrant replacement. This is similar to
the rationale used for sewer and water utilities. Sewer and Water utilities fund at
a 50 year replacement cycle. Below is a table relating system replacement cycle
lengths to required annual funding and staffing requirements.
Replacement Annual CIP Annual Program Annual Engineering/
Cycle Funding Operating Costs Inspection
Requirements Staff Hours
25 Years $3,000,000 $50,000 7500
50 Years $1,500,000 $50,000 4000
75 Years $1,000,000 $50,000 2500
100 Years $750,000 $50,000 __ _ 2000
150 Years $500,000 _ $504000 1500
200 Years _ $375,000 $50,000 1000
Storm Sewer Management Plan
Page 9
500 Years $150,000 $50,000 500
Funding should be adjusted yearly to reflect increases or decreases in system
extents and current replacement costs due to inflation. Annual funding will be
used as needed to replace pipeline and street crossing.culverts.
A2.CMP SYSTEM REPLACEMENT METHODOLOGY
The CMP system replacement methodology also recommends that the City selects
a replacement cycle period and fund accordingly. The replacement cycle in years
corresponds to the length of time until the City has replaced its entire existing
CMP infrastructure with more modem materials. Therefore, if the City funds
.storm sewer CMP replacements at a 50 year level, in theory, all existing CMP
facilities will have been replaced in that 50 years period.
CMP Annual CEP Annual Annual Engineering/
Replacement Funding Program Inspection
Cycle Requirements Operating Costs Staff Hours
8 Years $1_,687,500 $25,000 4200
10 Years $1,350,000 $25,000 3600 _
20 Years $675,000 $25,000 180.0 .
25 Years $540,000 $25,000 1500
50 Years $270,000 $25,000 800
Funding should be adjusted yearly to reflect increases due to inflation. Annual
finding will be used as needed to replace CMP pipeline and CMP street crossing
culverts.
A3.HISTORIC FLOODING/FAILURE METHODOLOGY
Current the City spends approximately$50,000 a year to fund drainage inlet
replacements. The historic flooding methodology would recommend continuing
with the same rational and augmenting the funding with an additional $150,000 to
fund a selected system replacement. This would bring the total funding for this
methodology to$200,000 a year. This methodology is intended to fund the
system replacements at a minimum level until additional funding becomes
available and one of the previously mentioned long-term methodologies can be
implemented.
B. MAINTENANCE METHODOLOGIES
B 1.TOTAL MAINTENANCE METHODOLOGY
The total maintenance methodology would require City Streets Maintenance Staff
to clean every drainage inlet once a year. The City currently owns over 2100
drainage inlets. This methodology will require 3150 hours of staff time a year.
This methodology will greatly reduce the amount of trash, debris and sediment
that the first rains of winter flush into the creek system.
Storm Sewer Management Plan
Page 10
�-ao
For the City to accomplish this level of maintenance, additional staff and
equipment will be required. Two City Maintenance Worker II's will be needed to
offset the additional maintenance work and a Vactor truck will be required.
Annual Fu ding Requirements
Two Streets Maintenance Worker 1 $138,000
Vactor Truck Maintenance J $10,000
Funding Requirements for Equipment Purchase
Vactor Truck J $ 250,000
B2.SELECT MAINTENANCE METHODOLOGY
The select maintenance methodology would require City Streets Maintenance
Staff to clean select drainage inlets in the more debris prone areas of the City
(near Cal Poly, San Luis High School, Foothill Boulevard and key creek
corridors). This methodology will require 500 hours of staff time a year and is
intended to lessen the amount of trash and debris that the first rains of winter flush
into the creek system.
The City can accomplish this level of maintenance service by utilizing existing
maintenance staff and working on weekends. Over a six week period, prior to the
rainy season (October 15 —April 15), existing maintenance staff working
overtime on Saturdays and Sundays can clean these select drainage inlets. By
allowing this weekend work, it might also be possible to rent other agencies
Vactor equipment or if not possible outsourcing the City's Vactor truck
requirements to an outside contractor is an option.
Annual Funding Requirements
Streets Maintenance Worker Overtime $25,000
Vactor Truck Rental $30,000
Total $55,000
RECOMMENDED PROGRAM
Given the age of the City's existing storm sewer infrastructure, it is important to have a
long-term storm sewer rehabilitation plan in place in order to protect the City's previous
expenditures long into the fixture. Additionally, with a thorough storm sewer
maintenance plan, much of the trash, sediment and debris can be collected and disposed
of before it is allowed into our creek system. Therefore, the Storm Sewer Management
Plan recommends a total system replacement and total maintenance methodology using a
75 year replacement cycle. With this recommended level of maintenance and
recommended level of funding, annual demands on staff time will increase for capital
improvement project (CIP) management and ongoing maintenance.
As summarized below, this results in a significantly expanded CIP, and three added
regular staffing positions: two added maintenance workers in addition to the one
Storm Sewer Management Plan
Page 11
currently authorized; and an additional inspector to manage the increased level of
improvement projects.
FundingAnnual Requirements
Current Proposed Chan e
Annual CIP Funding(1) $ 27,500 $ 1,000,000 $ 972,500
Operating Costs 0
Maintenance Workers(2) 69,000 207,000 138,000
Public Works Inspector 85,000 85,000
Other Operating Costs 50,000 50,000
Amortized ui ment Costs:Vactor @ $250,000, 8-year life 31,200 1 31,200
Total 96,500 1,342 000 1,245,500
1. $50,000 is the annual average.annual level of funding for storm sewer improvements over the last four
years;the estimated annual cost of the proposed program is based on current system value divided by
the replacement cycle.
2. There is currently one maintenance worker authorized for storm sewer maintenance.
It is important to emphasize that these funding needs only address the storm sewer
components of the City's flood protection system. Creek-related improvements and
maintenance are covered in the City's Waterways Management Plan, and as such, the
cost for these are not presented in this plan.
FINANCING PLAN
There are three possible sources for funding the proposed storm sewer plan: General
Fund; County Flood Control Advisory Board Zone 9; and a dedicated revenue source.
The following discussed each of these options.
General Fund
This has traditionally been the City's primary funding source for storm sewer
maintenance and improvements. However, because it competes with other high-priority
needs for funding — such as.police protection, fire suppression, medical emergency
response, streets and parks — it has not historically received anywhere near the level of
funding identified in this plan, even in the best of fiscal times. Given the significant
financial challenges facing the City's General Fund, it is unlikely that continuing to rely
upon the General Fund will result in funding the program set forth in this plan. In fact,
reductions in current resources are much more likely,
County Flood Control Advisory Board Zone 9
The County Flood Control Advisory Board Zone 9 is comprised of agencies and citizens
located, operating or living in the San Luis Obispo Watershed. The intent of Zone 9 is to
advise the San Luis Obispo County Board of Supervisors on watershed related issues.
Additionally, Zone 9 funds projects and studies that benefit the watershed as a whole.
The County, through Zone 9, has traditionally allocated some funding for flood
protection maintenance and improvement to the City through this source. In recent years,
Storm Sewer Management Plan
Page 12
Z� 'o�o
we have received about $67,000 annually from this source, although it has been as high
as $600,000 in funding the preparation of the Waterways Management Plan. There are
five challenges in relying upon Zone 9 to help fund the proposed stone sewer program:
1. Funding allocations are not within the City's control: this is solely a discretionary
decision by the Board of Supervisors.
2. Zone 9 is bigger than the City, and as such, we compete with other areas in the
County for funding.
3. Special district like Zone 9 have also experienced significant State budget cuts, and as
such, future funding levels are uncertain at best.
4. It is highly unlikely — on an average annual basis — that it will provide more than
$100,000 in funding, which is far less than the needs identified in this plan.
5. Lastly, while Zone 9 funding could be used for storm sewer maintenance and
improvements, it has traditionally been used for creek-related activities such as
Prefumo Arm dredging and reed clearing.
Dedicated Funding Source
Establishing a dedicated funding source is the best way of ensuring an adequate, reliable
funding for the storm sewer program. There are three basic was of doing so:
Storm Sewer Enterprise Fund. Similar to the water and sewer funds already in place in
the City, where user fees cover the full cost of the programs, the City could establish a
storm sewer enterprise fund. In fact, the City did so in 2002, with an approach that would
cover both waterways and storm sewers in meeting the City's flood protection needs.
The Creek and Flood Protection Fund approved by the Council in May 2002 was funded
by user fees from four classes of customers: single family residential, multi-family
residential, schools and all other users. Fees were apportioned based on a very
sophisticated analysis using our geographic information system of impermeable surfaces.
With this approach, users would be charged based on their relative shares of run-off into
the City's storm sewer and creek system, this reflecting their apportioned use of the
City's flood protection infrastructure.
The Council ultimately adopted a five-year rate plan that would generate $1.3 million
annually based on the following monthly rate structure:
Storm Sewer Management Plan
Page 13
Customer Typ
Single Family Residential $4.50 Per Unit
Multi-Family Residential $1.50 Per Unit
Schools $0.1368 Per 1,000 Square Feet of Parcel Size
All Other Customers $0.6792 Per 1,000 Square Feet of Parcel Size
However, shortly after Council approval of the Creek and Flood Protection Fund and
rates, there was a court decision that these types of fees were "property 'related," and as
such, required majority property owner approval under Proposition 218. This did not
mean that the City could not form this enterprise fund and set rates for service
accordingly, but it did mean that the Council could not do so on its own..
Accordingly, the option of creating a dedicated funding source via an enterprise fund
concept is still a viable one; and an "equivalent dwelling unit" rate of $4.50 per single
family resident would generate the $1.3 million recommended in this plan. However,
doing so in accordance Proposition 218 will require of the rates by a majority of the
property owners who would be responsible for paying these fees. As this implies, this
means that eligibility for voting is based on who pays the fee, rather than who is a
registered voter. Additionally, votes are weighted by the amount of the fee to be paid.
For example, a property owner with $500 fee would have five-times more of a vote than
an owner with a $100 fee. Using this as the basis for determining voter eligibility, the
outcome would be determined by a majority of the weighted votes cast(versus two-thirds
voter approval for special taxes discussed below).
Fees would be collected on the property tax roll, which is very effective, reliable and
low-cost method of revenue collection.
Assessment District. While structurally different from an enterprise fund with user fees,
the practical result is the same. For example, instead of a $4.50 per month user fee for
single family residences, there be a $4:50 per month assessment. Additionally, while
there are some differences, the approval process is also very similar to the enterprise
fund, property-related user fees discussed above. Lastly, assessment revenues would also
be collected on the property tax roll.
Since the outcome and approval process are so similar, the enterprise fund approach may
be preferable from a "transparency" perspective: while our customers are used to paying
fees for service, we do not currently have any assessment districts.
Special Purposes Taxes. With the exception of ad valorum property taxes (which are
strictly limited to 1% of market value under Proposition 13), the City can impose new or
added taxes in wide range of areas, including sales taxes, parcel taxes, real property
transfer taxes, utility users taxes, transient occupancy taxes and business taxes. Tax rates
for virtually any of these sources could be set at levels — either singly or in combination
with each other — that would fund the proposed program. However, doing so and
dedicating the proceeds to the storm sewer program would require two-thirds voter
approval. Descriptions of each of these sources and their revenue raising potential are
Storm Sewer Management Plan
Page 14
Ll -v
i
provided in the General Fund Five-Year Fiscal Forecast, along with an overview of what
it would take to initiate a successful revenue ballot measure.
Storm Sewer Management Plan
Page 15