Concrete MH Barrels Disintegrate While Lined MH

Bases Remain UnscathedPrepared for the

Rocky Mountain Water Environment Association

By:Peter Keefe, M. Sc.1

Rimon Estawro, P.E.1 Steve Underwood, P.E2

1. Predl Systems, 2. TRUE Consulting

Oliver, British Columbia

• Located in Okanagon River Valley, 15 miles north of Washington State

• Northern limit of Great Basin Desert and only desert in Canada

• Wine Capital of Canada• On Lake Tuc-el-Nuit

In 1992, the Town of Oliver extended it’s Sewer System

• Gravity extension outlined in blue• Precast FRP liners specified for

MH bases, but not for barrels and cones

• Red force-mains installed 2002• Road names: Pinot, Chardonnay,

Shiraz, Gamay, Cabernet… • What do you think they do here?

Minor Odor Complaints Arose Immediately• Odors thought to result from low flows• Oliver constructed extra sewer vents and hid them in the trees• Vents reduced odors, solved problems• Next decade was uneventful

In 2002, Winery Was Connected to Tuc-el-Nuit Sewer via Force-Main Shown in Red

• “A stench” arose immediately

• Town removed extra vent stacks in trees

• No reduction in complaints

• Installed charcoal filters• Ineffective, lots of maintenance• Town soon removed them

Oliver’s Fight Against Foul Odors Continued…

• Town installed P-traps on sewer laterals• Just like the P-traps beneath your sinks• Somewhat effective, but odor complaints continued

• Town Encapsulated MH covers in plastic bags and buried them under 4 inches of soil

• Odors finally removed!

• But something worse was bottled up…

In 2007, Part of the Main 36-inch Interceptor Near the Treatment Plant Collapsed• Oliver quickly replaced the interceptor with 36-inch PVC pipe• Concrete manholes were replaced with IPEX plastic MH structures• MH barrels along Lake Tuc-el-Nuit were discovered to be badly

corroded and in danger of collapse

When Tested, Winery Effluent Was Found to Be Acidic and Extremely High in BOD5 • pH of 4.0 and BOD5 concentrations as high as

14,000 mg/liter• Average wastewater has a more neutral pH

between 6 and 9 and a much lower BOD5 of 100 – 400 mg/liter

• Winery waste was quite abnormal.

Acidic Winery Waste Had Disintegrated Concrete MH Barrels in Only Five Years

• MH barrels were badly corroded• Fortunately, FRP lined manhole bases

were still completely intact.

• This allowed Oliver to replace the barrels, cones and covers on top of existing bases.

New FRP Lined Barrels Installed on Existing, Intact, FRP Lined Bases• Shallow 8” Tuc-el-Nuit sewer remained in service• Reusing MH bases avoided bypass pumping, saving ~$13,000.

In 2012 Winery Added Pretreatment

BOD5 dropped from 4,000 mg/l to less than 200 mg/l3

3. Sanitary Sewer System 2012 Annual Report, Town of Oliver, by TRUE Consulting, March 2013

So, the Oliver Story Ended Well

• Corroded manholes replaced with corrosion-proof FRP lined manholes

• Yellow, FRP MH bases reduced construction costs by at least $13,000

• Pretreatment greatly reduced acid concentrations.

• So, has Oliver started to live happily ever after too?

• Maybe so, but author needed to know more…

What About Long-Term Performance of FRP Liners?• This looks like a promising technology, but how effective is it?

• What is the known service life?• Do they really reduce maintenance?• Are they truly corrosion-proof?• Or my favorite: ”Do you have any before-and after rehab flow data?”

For Answers We Looked to the Largest, Oldest Database of Manhole Liners in North AmericaPierce County, Washington

• Stretches from Puget Sound and Tacoma to Mount Rainier – 39” to 115” annual precip

• 250,000 people served• Began installing FRP MH

bases in 1989 – 25 years ago• ~11,000 installed to date• ~870 miles of sewer mains

Did FRP Liners Really Reduce Maintenance Costs?

• Early flows were too low to pass solids through rough concrete MH channels

• Many channels clogged chronically• To eliminate clogs, County

rechanneled dozens of MHs• Clean, plug, jackhammer, re-clean, re-

formed concrete troughs• Three to Six people stayed until

concrete set – usually an entire day

Rechanneling Cost Estimate: 4 Workers and 2 Trucks:

• 4 * $20/hour * 8 hours * 3.0 overhead = $1,920• Vactor Truck - $3,000 per day• Cleaning Truck - $1,600 per day• Total $6,520

• Didn’t always stop clogging

County Discovers FRP Base Liners in 1988• FRP Base Liners:• Improve vision• Don’t clog: n-factor reduced

from 0.24 to 0.10• Cost $500 to $900?

depending on number of channels

• Never having to clean or re-channel another manhole – nearly priceless.

How Reliable Are the Liners?

• Six (6) liner breaks in 11,000 manholes• Four caused by improper repairs to existing liners• Two (2) caused by unauthorized new lateral taps• All defects were repaired on-site• 99.95% Intact through construction

How Effective Against Corrosion?Lab Testing Results4 on 20-year Old

Specimen• Energy Dispersive X-ray Spectroscopy• Fourier Transform Infrared Spectroscopy• Scanning Electron Microscope• Mechanical Destruction

• Conclusion: Liner completely intact; no sulfur intrusion into concrete

• Concrete actually stronger!

4. “Evaluation of Predl Base Liner After 20 years of Service” Polymer Engineering Company, September 2013

How Waterproof Are the Liners?

• All FRP sections heat welded in the field• All connecting pipes gasketed

• Choice of 6 different types of gaskets

All penetrations include turn-backs extending through the concreteCompletely watertight

Did MH Liners Really Help Reduce I/I?• Anecdotally, Pierce County Sewer System had:

• Never had a capacity related SSO !• Never had an NPDES Violation at the WWTP !• Had only a 2:2 peaking factor at the plant during 10-year storm !

• In 99 previous sewer studies, I had never heard of a system that performed this well. Have you?

So, We Were Just a Tad Skeptical…

Asked if Pierce County had any flow monitor and rainfall data to prove it?Found flow data from 16 flow meters and 5 rain gauges

Proposed a rigorous RDII AnalysisUploaded all dataProcessed data in Sliicer

Calculated RDII rates for 400 basin-storms using an online tool called Sliicer65. John Cleese – Monty Python

6. Sliicer.com – ADS Environmental Services

Sliicer Dry Day Flows Highly Rigorous

Weekdays and WeekendsAverages of 73 candidate dry days

Sliicer Storm Analyses 400 Basin-Storms

All Metered Locations Can Transport 10-yr Storm Flows

(1/12/2011)

(12/26/2011) (12/29/2011)

0.0

0.1

0.2

0.3

0.4

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Q vs i - PC_22Peak Gross I/I vs. Rolling Peak Rainfall Intensity

Peak

Gro

ss I/

I (M

GD

)

Rolling Peak Rainfall Intensity (in/hr)

AllStorms

Straight-line Q to i flow projections from Sliicer

Here are Resultsfrom 400 StormsBasin

Linear Footage

Max Percent

RDII

Num. SSOs

Num. WIBs

Excessive? Rank

PC01 121,026 4.58 0 0 nonexcessive 1PC18 181,490 3.62 0 0 nonexcessive 2PC21 181,207 3.62 0 0 nonexcessive 3PC17 96,622 2.41 0 0 nonexcessive 4PC06 160,724 1.77 0 0 nonexcessive 5PC16 98,801 1.73 0 0 nonexcessive 6PC08 17,751 1.41 0 0 nonexcessive 7PC02 485,709 1.36 0 0 nonexcessive 8PC05 246,996 1.19 0 0 nonexcessive 9PC04 168,502 1.06 0 0 nonexcessive 10PC Tunnel 810,267 0.79 0 0 nonexcessive 11PC22 166,615 0.18 0 0 nonexcessive 12PC03 408,527 0.00 0 0 nonexcessive 13PC19 153,428 0.00 0 0 nonexcessive 14PC20 108,527 0.00 0 0 nonexcessive 15PC25 99,005 0.00 0 0 nonexcessive 16

Table 1-1: Maximum Percent RDII Results Ranked

No possibly excessive I/I >5%

No excessive I/I >10%

Analysis & Report took only 88 hours using Sliicer & Mail Merge

Rigorous AnalysisConfirmed & Amplified

Anecdotal Evidence

Comparative Results Were Astonishing

• 2013 – Report compared Pierce County’s to I/I in 8 other systems.

• Conclusion was that I/I is 71% lower than the next tightest system author had ever evaluated.

• MH liners significant in reducing I/I

0

10

20

30

40

50

60

70

80

90

100

PER

CEN

T R

DII

Comparison of RDII Rates

Avg Basin RDII Max BasinRDII

To Summarize, We’ve Shown that FRP Manhole Liners:

1. Remained unscathed after 20 years in Oliver, BC including 5 years of strong acidic assault, showing 0% corrosion

Same performance after 25 years in Pierce County

2. 99.95% reliable as delivered – repairable in the field3. Saved more than their own cost in maintenance,4. Reduce clogs, improving flows and5. Are an integral part of the tightest sewer system that the author has ever

evaluated

In Conclusion: You Can Benefit Three Ways from Specifying FRP Lined MHs in Your Sewer System

1. Little Maintenance, 2. No Corrosion and, 3. No I/I

• Check the links below – It’s rare that a product corrects all three major sewer system problems.

• Links contain all information presented herein as well as manufacturing videos and technical specifications:

www.predlsystems.com/

http://www.predlsystems.com/downloads-center/performance-reports/Phone: 604-415-9944

“I think I’m in love with those manholes” – Alejandro Doble, P.E. - CH Caribe

Thank You

Are there any questions?