Rancho Palos Verdes City Council
   

Storm Drain Master Plan Update Storm Drain Master Plan Update Power Point Presentation 06/15/2004

Storm Drain Master Plan Update Power Point Presentation

TO: HONORABLE MAYOR AND MEMBERS OF THE CITY COUNCIL

FROM: DIRECTOR OF PUBLIC WORKS

DATE: JUNE 15, 2004

SUBJECT: STORM DRAIN MASTER PLAN UPDATE

RECOMMENDATIONS

  1. Receive and file a report from the Director of Public Works regarding the update to the Master Plan of Storm Drain.
  2. Request the Infrastructure Financing Team to review the update and propose a spending and finance program for storm drain improvements.
  3. Establish a new program to line corrugated metal storm drains for FY 04 – 05 and authorize the expenditure of $500,000.

BACKGROUND

The City’s investigation into the storm drain system began in 1998 when a storm drain master plan was prepared. The principal deliverables of the master plan were an inventory of the storm drain system, a list of storm drains that were not adequate in size to convey the design storms, maps of the existing storm drain system showing the pipe location size and material type, and a cost to reconstruct those storm drains that were undersized.

The principal conclusions of the 1998 Master Plan were:

  1. There are a significant number of undersized pipes throughout the city.
  2. The majority of undersized pipes are in the eastern portion of the City, and more specifically in the Miraleste Area.

The 1998 Master Plan was presented to the City Council and later at a Community Leaders Breakfast in 1999.

A limitation of the 1998 Master Plan is that it did not investigate deficiencies in the City’s storm drain system other than those related to pipe size. For example it did not investigate the condition of pipes, nor did it determine if there were adequate inlets to collect drainage. It therefore underestimated costs.

In 1999 the City Council authorized an engineering investigation that focused on the storm drains along Palos Verdes Drive East. The report was more detailed than the 1998 Master Plan in that it did conduct video inspections to assess pipe conditions, and it did the necessary calculations to determine if there were an adequate number of inlets to pick up drainage. The report also proposed solutions and calculated an engineer’s estimate of cost.

The principal conclusions of the 1999 study were:

  1. There are large segments of Palos Verdes Drive East without an adequate drainage system. This deficiency results in drainage from Palos Verdes Drive East flowing onto private properties as well as into residential neighborhoods where there may not be adequate drainage facilities.
  2. The condition of corrugated metal storm drains is generally poor. Approximately 75% of corrugated metal pipes along Palos Verdes Drive East have decayed to such a degree that pipe collapse is possible.
  3. The cost to reconstruct deficient storm drains along Palos Verdes Drive East is approximately $10,000,000

In 2003 the City Council authorized an engineering investigation to prepare an update to the 1998 Master Plan of Drainage. The purpose of the update was to create in a single document a compensative look at the City’s storm drain system, with a citywide estimate of needs and costs. The update was needed to bring the detail in the 1998 Master Plan up to a level that is comparable to the 1999-focused study. To do this, approximately additional storm drains were video inspected. In addition, the plan was updated to reflect construction completed since the 1998 report, and finally the hydrology assumptions were updated based on revised criteria established by the County of Los Angeles.

DISCUSSION

System characteristics

The City’s storm drain system collects and conveys drainage runoff to the ocean and to other points outside the City’s boundary. It is independent and much different from the City’s sewer system, which connects to homes and collects and conveys wastewater to a treatment plant.

In total there are 477 storm drain systems throughout the City. Approximately 40% of the system is owned and operated by the County of Los Angeles. Attached, as Exhibit A, is a map of the City’s storm drain system.

The pipes that make up the storm drain system vary in size from 12 inches to as much as 120 inches in diameter. Pipe material for the most part is either corrugated metal or reinforced concrete. The older pipes are predominantly corrugated metal, while the newer pipes, those less than 40 years old, are predominantly reinforced concrete.

A brief summary of the City’s inventory of storm drain by ownership and material is as follows:

Inventory of Pipes by ownership

Material Type

City Owned

County Owned

Total

Corrugated Metal Pipes

200

0

200

Reinforced concrete

95

180

275

High density polyethylene

2

0

2

 

297

180

477

It is not a coincidence that none of the corrugated metal pipes are County facilities. Upon incorporation the County would only accept storm drain systems that were made of reinforced concrete and were 18" in diameter or greater.

History of expenditures on storm drains

Since 1993 the City has spent a total of $8.6 million on storm drain projects. Attached as Exhibit B is a list of those expenditures. For the most part, spending has been in response to an urgent need due to flooding. The bulk of expenditures were for the San Ramon Landslide and Drainage project, the Bronco storm drain, the PVIC storm drain, and a joint project with the City of Palos Verdes Estates.

Deficiencies

Investigations performed by the various studies uncovered a number of storm drain deficiencies. These deficiencies fall into the following categories:

  • The pipe is too small to convey the design storm
  • There are not adequate inlets to the pipe to pick up street drainage and flooding occurs
  • The pipe has the wrong configuration and discharges drainage at an unacceptable location
  • The pipe has deteriorated to such a degree that its ability to convey drainage is reduced, and pipe collapse is possible. Only corrugated metal pipes (CMPs) are subject to deterioration.

In both the 1998 and 1999 studies whenever a storm drain deficiency was found, it was recommended that the pipe be reconstructed. This recommendation is due to the fact that whenever a deteriorated pipe was found it was also found to be undersized in which case reconstruction is the appropriate remedy. During the course of this current study a number of CMPs were identified that were found to be deficient due to poor condition only and not undersized. In such cases the pipe could be reconstructed, however, a more attractive solution would be to repair the deteriorated pipe with some type of liner.

The greatest risk from a CMP storm drain that is in a state of disrepair is that it will collapse and cause immediate settlement to ground above. Such a condition would be dangerous if the pipe were under a roadway. Such a condition could cause damage to a structure that is adjacent to the storm drain (a number of our storm drains are immediately adjacent to residences). There have been two recent examples of a collapsed pipe; the first occurred on Miraleste Drive / 9th Street in the City of Los Angeles, and a second occurred just outside the right of way of Palos Verdes Drive East at Mustang Drive.

Except in some rare instances the cost of lining a storm drain will be significantly less than reconstruction. Lining a storm drain will not significantly add or reduce capacity to a storm drain. The lining process does add wall thickness to the pipe and thus reduces the pipe diameter slightly, however, this reduction is more than offset by the fact that the lining process reduces pipe roughness which adds capacity.

There is insufficient empirical data as to how much the life of corrugated metal pipe is extended by lining it. A number of factors play a part such as: the method of lining, flow characteristics, and the amount of sediment contained in the discharge. Pipe lining is fairly routine in the Public Works industry and based on information staff could obtain from vendors it is estimated that lining will extend the useful life a pipe by 25 years.

The following is a summary of the deficiency type, the risk of each deficiency, the preferred solution to each deficiency type, and the relative cost of each solution.

TABLE ONE

 

Deficiency due to

Problem

Risk of no action

Solution

Relative Cost

Remark

1

Size of pipe

Existing pipe is too small

Street flooding will enter private property

Construct a new storm drain

High

Especially critical when grade of property is below grade of street

2

Absence of pipe or inlets

A pipe is needed to pick up drainage

3

Pipe configuration

Existing pipe conveys drainage to private property

Drainage pipe discharges onto private property

Relatively rare

4

Condition of pipe

Portion of corrugated metal pipe has deteriorated.

Pipe collapse. Sink hole at surface.

Line pipe

Lower

Collapse may occur even during mild storm events.

It is noted that some CMPs were found to be both undersized and in a state of disrepair. A summary of finding is as follows:

TABLE TWO

Actions Required

Pipe Material Type

Total

Number

None

Lining only

Reconstruction only

Lining and Reconstruction

Corrugated Metal Pipes

200

47

91

9

53

Reinforced concrete

117

114

0

3

0

High density polyethylene

2

2

0

0

0

319

163

91

12

53

Table Three

Table Four

Costs

Storm Drain Reconstruction

The 65 systems that require reconstruction are part of 58 identified storm drain construction projects with a total cost of $ 24.8 million.

Not all the projects are of equal importance. Each project was reviewed and a priority was been assigned using the following criteria:

Priority One

Projects were assigned a Priority One if it was determined that failure of the storm drain to convey the 50 year storm would result in flooding of private property. Most priority one projects have experienced flooding in the past.

Priority Two

Projects were assigned Priority Two if it was determined that failure of the storm drain to convey the 50 year storm would result in significant street flooding or bluff or canyon erosion that over time could threaten structures. Some priority two projects have experienced flooding in the past.

Priority Three

Project were assigned a priority Three if it was determined that failure of the storm drain to convey the 50 year storm would result in inconsequential street flooding which would not, even over time, threaten structures.

A summary of project cost to reconstruct by priority is as follows:

TABLE FIVE

 

Priority One

Priority Two

Priority Three

Total

Number of projects

12

21

25

58

Construction Costs

$4,975,960

$7,981,393

$4,788,900

$17,746,253

15% contingency

746,394

1,197,209

718,335

$2,661,938

25% admin legal, and engineering

1,243,989

1,995,348

1,197,225

$4,436,563

Total Project Costs

$ 6,966,343

$11,173,950

$6,704,460

$24,844,754

Storm Drain Lining

As shown in Table Two above, in addition to the CMPs requiring reconstruction 91 CMPs require lining. Utilizing an average cost of $50,000 per lining project results in a $4.6 million program.

Staff has experience in the lining process as follows:

Mustang Culvert

Size Specifications: 140 lineal foot of 30" corrugated metal pipe

Location: Palos Verdes Drive East at Mustang Road

Process: Manual placement of concrete slurry

Cost: $17,000, $120 per lineal foot

San Ramon Drive

Size Specifications: 375 lineal foot of 18"/24" corrugated metal pipe

Location: San Ramon Drive to San Ramon Canyon, between two private residences

Process: Cured in place lining from remote location

Cost: $63,000, $168 per lineal foot

Location of projects

Storm drain deficiencies are found throughout the City, however they were found to be concentrated in two drainage areas; along Palos Verdes Drive East and along the city’s southern coastline. This should not be surprising since these two areas were the first areas of the city to be developed and they have the oldest infrastructure.

Table Six

Area

Reconstruction costs

Lining Costs

1

$ 11,231,080

$ 2,050,000

2

$ 11,471,110

$ 850,000

3

$ 210,000

$ 450,000

4

$ 514,500

$ 650,000

5

$ 730,800

$ 450,000

6

$ 687,260

$ 100,000

Total

$ 24,844,750

$ 4,550,000

As discussed above not all projects identified for reconstruction are urgent projects. Those given a priority three may in fact be delayed with little consequence. Given this as well as the limitation on funding when the Infrastructure Financing Team reviews the report, and proposes a funding program, consideration will be given to a program that completes all storm drain lining as well as those construction projects given a Priority rating of one or two. The costs for such a program would be as follows:

Table Seven

Area

Reconstruction costs

Lining Costs

1

$10,885,280

$ 2,050,000

2

$ 6,905,850

$ 850,000

3

$ 210,000

$ 450,000

4

-

$ 650,000

5

-

$ 450,000

6

$ 139,160

$ 100,000

Total

$18,140,290

$ 4,550,000

CONCLUSIONS

Engineering studies have identified a number of deficiencies in the City’s storm drain infrastructure. Storm drains were found to be undersized, lacking inlets, configured such that it discharged drainage in an unacceptable manner, and in a state of disrepair. The total cost of reconstruction is $24.8 million. The total cost for lining is $ 4.5 million. Not all projects are urgent. For example, approximately $6.7 million of the reconstruction costs are considered priority three projects and can be deferred with little consequence.

To address these deficiencies staff recommends that two new programs be established. The first program would construct new storm drains where deficiencies related to pipe size, lack of inlets, or configuration are found. The second program would line those corrugated metal pipes that are found to be in a state of disrepair. The two programs would not be independent since many corrugated metal pipes were found to be in need of lining and were undersized. A decision as to if a corrugated metal pipe should be lined or reconstruct will be made only after consideration of risks is made.

Funding for these two programs will be challenging for the City. Currently funding is not available on a consistent basis for either program. For example the adopted FY 04 -05 budget includes no funding for storm drain construction, and it includes $500,000 for a storm drain lining program only because the City received one-time insurance funds regarding the San Ramon project.

The staff recommendations include the recommendation that the update be presented to the Infrastructure Financing Team for the purposes of recommending a spending and funding plan.

The staff recommendations also include the recommendation that staff move forward with the program to line storm drains. Staff has a backlog of such needs and it is expected that within two months a project can be advertised. After that a second project will be assembled and awarded during the later part of FY 04 – 05.

If funding is continued staff will proceed in a proactive manner to inspect conditions for those high-risk corrugated metal storm drains and line those found to be in a state of disrepair. High-risk storm drains are those, which are older, under major arterial roadways or immediately adjacent to private residences.

FISCAL IMPACT

Funding is available in the adopted FY 04 – 05 budget for a $500,000 storm drain-lining program. There are no additional funds available for the construction of storm drain improvements and the Infrastructure Financing Team will be tasked to recommend a funding program.

Possible Establishment of Storm Drain User Fee

A report presented to the City Council by the Finance Advisory Committee dated March 4, 2003, included the following recommendation:

Staff and the FAC believe that the City must immediately implement a long-term plan to replace existing and build additional storm drain infrastructure. After reviewing several alternatives, staff and the FAC believe establishing a storm drain user fee is the most practical "revenue" alternative to provide monies to pay for storm drain infrastructure improvements.

At the conclusion of its discussion, the City Council directed staff to proceed with the preparation of an Engineer’s Report for the possible formation of a storm drain user fee. The Infrastructure Financing Team that includes Fieldman and Rolapp, the City’s Financial Advisor, Robin Harris, Deputy City Attorney Robin Harris, Joan Cox of Harris & Associates, the City’s assessment and fee rate engineer, the City Manager, the Director of Public Works, the Director Finance and Information Technology, the Accounting Manager and Senior Administrative Analyst, affirmed the FAC’s recommendation to consider the establishment of a storm drain user fee.

On March 2, 2004, the City Council approved the selection of Moore Iacofano Goltsman, Inc. ("MIG") as the City’s public information consultant for the Infrastructure Renewal and Maintenance Project. MIG recommends that the City complete a storm drain user fee study prior to stakeholder interviews and the completion of a baseline survey that would determine the community acceptance of a possible storm drain user fee. Depending on the results of the Sewer Master Plan Study, currently in progress, a sewer renewal financing plan may also be required. If so, the scope of the stakeholder interviews and baseline survey may also incorporate the possibility of a sewer user fee. The Sewer Master Plan Study should be available in August.

Submitted by,

Dean E. Allison

Director of Public Works

Reviewed by,

Les Evans, City Manager

Exhibit A – Exhibit of storm drains citywide

Exhibit B – Chronology of storm drain expenditures