Rancho Palos Verdes City Council
   

OCTOBER 19, 2004 SANITARY SEWER MASTER PLAN OCTOBER 19, 2004 SANITARY SEWER MASTER PLAN

TO: HONORABLE MAYOR AND MEMBERS OF THE CITY COUNCIL

FROM: DIRECTOR OF PUBLIC WORKS

DATE: OCTOBER 19, 2004

SUBJECT: SANITARY SEWER MASTER PLAN

RECOMMENDATION

Receive and file the Sewer System Master Plan Study.

BACKGROUND

The City of Rancho Palos Verdes owns and operates its own sewage collection system. The sewage collection system serves a population of approximately 39,000 people within a 13.5 square mile, essentially fully developed, service area. Dwellings in the City are generally composed of individual homes, condominiums, and town homes.

Los Angeles County maintains the sewer system for the City of Rancho Palos Verdes. They collect a fee from each property within the City which was recently increased from $17.50 to $22.50 per year. Maintenance performed includes random line cleaning, repairing failed lines, performing visual inspections and responding to and rectifying sewer overflows. Los Angeles County has indicated to staff that they intend to begin two new maintenance tasks for the City of Rancho Palos Verdes which will include cleaning all pipes and performing Closed Circuit Television (CCTV) inspections of all pipes, over a ten-year period. Information from neighboring cities regarding how frequently sewage collection pipes are cleaned and inspected indicated varying periods of time from once in a two-year period up to once over a ten-year period.

The City’s investigation into the sanitary sewer system began in August of 2003 when the City Council authorized an engineering investigation to prepare a Sanitary Sewer Master Plan. Deliverables included a Graphical Information System (GIS) of the sewers, which is an electronic map and database, an inventory of the sewer system, a list of sewer pipes that were not functioning at an adequate level, hydraulic analysis of the sewers and an estimated cost to rehabilitate the system.

The Sanitary Sewer Master Plan was needed to create in a single document; a comprehensive look at the City’s sanitary sewer system, with a citywide estimate of needs and costs. The Master Plan addresses the soon to be implemented United States Environmental Protection Agency’s Capacity Management, Operations and Management (CMOM) program. Additionally, if the local Regional Water Quality Board adopts similar regulations, the Master Plan can be presented to the Board to address the non-fiscal aspects of the system. The plan analyses the hydraulic requirements of the system, the overall condition of the system and how to best estimate the costs associated with improving the system.

DISCUSSION

System characteristics

The City’s sewer system collects and conveys wastewater through pipes to a wastewater treatment facility operated by the Los Angeles County Sanitation District. Approximately 13,000 customers (about 39,000 people) are served by the 780,000-foot long system (148 miles). Seven lift stations are used to overcome grade differentials within the city; the smallest pipe diameter is 1.5 inches and the largest is 15 inches. The dominant pipe material is clay (95%) with some steel and ductile iron pipes. 3,550 manholes provide access points for maintenance activities to the sewers.

History of expenditures on sanitary sewers:

Since incorporation, the county has maintained the sewer system, made repairs and performed cleaning when they determined repairs or cleaning was necessary. The County cleans the system when they find roots in manholes or when blockages occur. Visual inspections are performed on each manhole in the City at least once per year. Attached as Exhibit A, is Los Angeles County’s Sewer Maintenance Productivity Report for Rancho Palos Verdes. This work was funded with an annual contribution of $17.50 from each parcel connected to the sewer system within the City (approximately $230,000). The county recently increased the sewer maintenance and operation fee $5.00 per year, accordingly their annual budget for work in Rancho Palos Verdes increased to approximately $300,000.

Deficiencies

Investigations performed by the various studies uncovered few deficiencies within the sanitary sewer system. The hydraulics of the system exceed requirements. Deficiencies do not currently exist with regard to the system’s ability to carry waste. The overall physical condition of the system included deficiencies which fall into the following categories:

  • Some pipes have roots intruding through joints varying from minor hair like roots to large roots
  • Some pipes have cracks of varying severity
  • Some pipes have accumulated fats and grease

A special inspection was conducted to determine if a relationship existed between observed roots and obscured structural damage (cracks). The results of that inspection did not reveal a clear relationship between root mass and obscured defects. It appears that the system has not been adequately maintained through regular cleaning and maintenance. Accordingly, the overall physical condition of the system is fair.

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

Fine to Medium Root intrusion

Sewage flow and system integrity of the pipe is compromised

Blockage will continue to grow and crack pipe or block sewage causing an overflow

Perform video inspections and needed cleaning

Low

Critical to maintain structural integrity of system and prevent overflows

2

Fats and Grease are present

Sewage flow is restricted

3

Structural condition of pipe (fine cracks)

Cracks can allow root intrusion & reduce structural integrity.

Roots enter the pipe, grow and continue to crack the pipe

Clean the pipe

Low

4

Structural condition of pipe (moderate to heavy cracks)

Ground water flows into pipe reducing capacity to carry sewage and structural compromise

Capacity reduction can lead to overflows; heavy cracked pipes can collapse and block the flow of sewage causing an overflow

Line or Remove and replace the pipe

High

Pipes are currently repaired by county when breaks are discovered

Costs

Sanitary Sewage Collection System Maintenance

Approximately 6% of the sewage collection system was CCTV inspected in conjunction with the Sewer Master Plan. Of the approximately 210 pipeline segments that were CCTV inspected, 51 were observed to have cracks. Fortunately however, most of the cracks observed were minor. Only 5 of the 210 pipeline segments had large, moderate or more than five small cracks. This indicates that while cracks were observed in approximately 25% of the inspected lines only 2.3% of the inspected lines were in such poor condition that they would require near-term action such as replacement. Replacement costs using standard open cut methods, are estimated at approximately $120/foot. Based on this limited sample, and if the remainder of the system has the same characteristics as the CCTV sample, then approximately $2.16 million is needed for pipe replacement.

CCTV inspections and cleaning has a relatively low cost ($1.50/ft.) and provides an immediate benefit to the system, in addition to aiding in identifying structural deficiencies in the system. A cleaning and CCTV program for the remainder of our system is estimated to cost $1.1 million.

If all the minor cracks anticipated to exist in the City’s sewer system were repaired by lining the pipe, an estimated 190,000 feet would need to be lined.

Maintenance performed to the system by Los Angeles County has not been adequately funded, and did not include provisions for rigorous preventative maintenance. However, as previously mentioned, with collection of the increased fee the County has indicated they will perform CCTV inspections and clean the entire system over a ten-year period. With the increased fees, they will collect approximately $3 million over the next ten years.

Not all the maintenance and repair activities identified in the study are of equal importance. Each activity was reviewed and prioritized s follows:

Priority One

CCTV and Cleaning – this activity will provide an immediate benefit to the system by restoring capacity and flow, discouraging root growth and halting the cracking that is associated with root intrusion.

Replacement of known structural deficiencies – this activity will correct suspected deficiencies and restore structural integrity to the system.

Priority Two

Line pipes to prevent water infiltration – this activity was determined to be of little benefit to the system due to the outstanding hydraulics of the system. The hilly terrain of the City allows fluids to move quickly through the system so capacity is generally not compromised.

A summary of costs by priority is as follows:

Method

Unit Cost ($/ft)

Length (feet)

Estimated Cost

CCTV & Clean

$1.50

740,000

$1,110,000

Replacement

$120.00

18,000

$2,160,000

 

Total Recommended Work

$3,270,000

Lining*

$140.00

190,000

$26,600,000

*Lining minor cracks in the system is not anticipated.

As discussed above not all of the potential work on the system is urgent. The priority two projects may be delayed with little consequence. Staff is in the process of discussing the results from the Sanitary Sewer Master Plan with County representatives of the Waterworks and Sewer Maintenance Division. It appears that the majority of maintenance activities required for our system should be carried out by the County through their annual sewer fee.

CONCLUSIONS

Engineering studies have identified a number of deficiencies in the City’s sewer infrastructure. Most of the deficiencies are related to inadequate system maintenance. The City is beginning a proactive effort to address problems identified in the Master Planning process. By conducting a CCTV inspection in a well dispersed sample area, the need to clean and CCTV inspect the entire system was affirmed. Only through additional CCTV inspection will the true condition and the total extent of rehabilitation be determined. As a result of these considerations our immediate recommendations include the following:

  • Clean and CCTV inspect the entire system
  • Pursue Replacement of failed pipe with the County

The County is planning to CCTV the entire sewer system over the course of the next ten years. Following the county’s plan could result in the continued slow degradation of the sewage collection system. Staff is in the process of meeting with the County to develop a more aggressive maintenance plan, one that will complete CCTV and cleaning activities over a 5-year period. Replacement of cracked pipes should be accelerated as well. The costs of an accelerated CCTV, cleaning and pipe replacement program are assumed to be approximately $220,000 per year for CCTV and cleaning and $432,000 per year to accomplish pipe replacement within the 5 years. At least $300,000 of the $654,000 annual maintenance program should be funded by the County. The remaining $354,000 annually may have to be provided by the City.

FISCAL IMPACT

Funding requirements for the City for an accelerated maintenance program are anticipated to be $354,000 per year for each of the next five years, however, actual costs will be determined during discussions with the County. Funds could be allocated from City General Fund Reserves if an accelerated maintenance program is agreeable to the County.

Submitted by,

Dean E. Allison

Director of Public Works

Reviewed by,

Les Evans, City Manager

 

Exhibit A – LA County Sewer Maintenance Productivity Report

SEWER MAINTENANCE PRODUCTIVITY REPORT

COLLECTION SYSTEM - DIVISION LEVEL

FIELD WORK COMPLETED: July 1, 2003 to June 30, 2004

City of Rancho Palos Verdes

Total pipe length as of June 30, 2004 - 752,133 feet

Total manholes as of June 30, 2004 - 3,436 manholes

PREVENTIVE MAINTENANCE ACTIVITIES

Sewer Pipe

    • Hydro cleaned 11,841 feet of pipe.
    • Mechanically rodded 52,073 feet of pipe.

Manholes

    • Inspected 6,872 manholes.
    • Adjusted 6 manholes.

SERVICE REQUESTS

Responded to:

    • 17 stoppage only
    • 12 overflows
    • 0 floodouts
    • 0 roach complaints
    • 1 misc
    • 0 other
    • 11 false alarm
    • A total of 41 service requests were responded to.

TELEVISING

A total of 4,131 feet of sewer pipe were televised.

ROOT CONTROL

5,880 feet of sewer pipe were chemically treated for roots.

CONSTRUCTION

0 saddles installed.

PUMP STATIONS

Total numbers of pump stations – 7

666 pump station inspections.

48 major equipment repairs/overhauls.

46 total call-outs for alarms and service requests.

ANNEXATIONS

0 parcel annexed to the district.

ACCUMULATIVE CAPITAL OUTLAY PROJECTS

0 sewer projects, reconstructed/rehabilitated.