Inspection-Driven Cleaning – South Placer Municipal Utility District’s Promising New Approach to its Mainline Pipe Cleaning Program

By Sam Rose, Superintendent, South Placer Municipal Utility District

About South Placer Municipal Utility District 

South Placer Municipal Utility District (District) is a sewer collection system agency that was founded in 1956 and serves the City of Rocklin, Town of Loomis, the communities of Penryn, Newcastle and a portion of Granite Bay, California.  Its service area is 31 square miles with a population of approximately 76,000. 

System Assets: 

  • 277 miles of mainline pipe ranging in size from 6” to 54”,  
  • 23,000 lower laterals totaling 108 miles 
  • 6,600 manholes 
  • 13 pump stations 
  • 12 flow recorders 

Employees: 

  • 27 total employees   
  • 5 in Administrative Services,  
  • 6 in Technical Services (Engineering, Inspection and IT) 
  • 16 in Field Services 

Background 

The District is dedicated to continual improvement and strives to improve business efficiencies for all aspects of its operations.  One area where significant improvement has been made is our CCTV inspection and pipe cleaning practices.   

Cleaning and inspecting pipes are common tasks for most collection system agencies.  These two tasks are generally top priorities in sewer collections.  Most agencies have problem lines, often referred to as Hot Spots, Trouble Spots or High Frequency Lines, that require more frequent cleaning.  However, industry practices are that most lines are cleaned on standard interval that the agency believes is adequate to prevent service disruptions and overflows.  In this regard, SPMUD had been cleaning their pipes on a five-year interval.    

This question was posed:  How do you know you are not cleaning “clean” lines?  A good question, one that staff does not typically contemplate or is of general concern. The method previously employed, 20% of the limes cleaned annually, was working well, as SPMUD maintained a low overflow rate (mainline pipes) for many years – averaging 2.2 spills per year since 2006.   

Staff began to develop a plan where only lines that needed to be cleaned, would be cleaned.  It was determined that CCTV inspections would be the key.  The plan was to CCTV a line segment and then determine whether it needed to be cleaned.  Since we had two CCTV crews and one Hydro-cleaning crew we believed we could keep the hydro-cleaning crew busy.  We determined a four-year CCTV cycle would be adequate.  At the core of this program is this: Once a line segment is inspected, the defect data (and other information) are analyzed, a decision is made:  1) clean it now, or 2)wait four more years for the CCTV crews to come around and inspect so it can be evaluated again.   

InspectionDriven Cleaning – How it works 

First, the collection system was divided into 43 maintenance zones (MZ’s).  After review of historic defect data (using PACP coding) and work order history, we were able to prioritize the MZ’s based on the likelihood of failure (i.e. blockage or overflow)

The District’s two CCTV crews are sent to work in the same maintenance zone at the same time and coordinate their efforts to inspect the entire zone in the most efficient manner.  Examples of this coordination: One crew might set up to inspect 6-inch pipes while the other sets up for eight-inch to allow for fewer transporter changes.  If most of the pipes in an MZ are the same diameter, crews will split the load geographically with daily progress check-ins to ensure no duplication of efforts.  

On the first of every month the defect data is pushed to a spreadsheet for analysis. The CCTV Lead Worker and the Field Supervisor responsible for the CCTV program perform the review independently and make determinations whether to clean each line segment.  Then, the two staff members compare findings, come to consensus and finalize the list of line segments to be cleaned.  This process requires about two staff-hours to complete.  A work order is created, and those lines are cleaned during the month. 

Since inception, only 21.5% of lines inspected have been deemed necessary to clean, which totals 1,565-line segments cleaned over four years (or 392/year) In addition to this are the District’s 213 High Frequency lines, which have cleaning intervals ranging between 1 and 24 months.  The High Frequency lines represent an additional 412-line cleanings per year or 1,648-line segments over the four-year period.  

Prior to this program, the Hydro-cleaning crew would be out every day cleaning lines with the intent of cleaning every line in the system in five years.  Now this same crew has been freed up to perform a multitude of additional tasks in support of other District programs. Each month the hydro-cleaning crew now performs: 

  • High Frequency mainline cleaning 
  • Inspection-Driven mainline cleaning 
  • InspectionDriven lateral cleaning 
  • Lateral root foaming 
  • Flow Recorder (x12) inspections     
  • Other duties as time allows     

 

In addition, the hydro operators can select the nozzle best suited – no guessing – they have the defect data and corresponding distances for each line segment.  And, less fresh water is being used for cleaning operations.  There is more windshield time for hydro operators, as the lines that need cleaning are not generally contiguous, though they are always located within the same maintenance zone.   

Since this program began in July 2015, we have experienced Five (5) mainline SSO’s.  This equates to 1.25 SSOs/ year, down from 2.2 SSO/ year prior to the implementation of the Inspection Driven program. Of these five SSOs, one was caused by concrete being discharged into the system and another was due to a failed cleanout plug that came apart and found its way into the mainline. The remaining three were determined to be maintenance-related (roots and wipes.) 

It is not necessary to have two CCTV crews working every day to inspect the system in four years.  We need about 1 1/4 CCTV crews to accomplish the four-year cycle.  If we are staying on schedule, one of the CCTV crews can be used to support other maintenance programs when sick leave, vacation or some other circumstance leaves another crew short-handed. Or, for tasks that have been deemed important, but not urgent, the ones that don’t ever seem to rise high enough on the priority list to get done.    

This method is now applied to all maintenance programs.  Programs like our pipe repair, manhole repair and easement maintenance programs historically have been inspection-driven programs.  Now our lateral cleaning, lateral root foaming and vector control programs are inspection-driven as well.  We know when it’s time to take action. 

Conclusions 

The first four-year cycle has been completed and it has been a great success.  Resources are being better utilized, productivity for other programs has increased and SSO’s have decreased.  It is recognized the real challenge will come during the second cycle, as the time since the last cleaning for many of these line segments will be have been extended significantly, in some cases it may be as much as 9 years between cleanings.  One can only ask, “Will those evaluating the pipe conditions have the stomach to let it ride another 4 years?  It is likely the percentage of lines requiring cleaning will increase.  We look forward to finding out.   

 

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