Lessons Learned on MSI Assessment and Heavy Cleaning of Large Diameter Sewers
Capital Region Water / Harrisburg PA
OWEA Collections Specialty Conference
May 2, 2017
John P. Schroeder, P.E., BCEE
Marc A. Lehmann, P.E.
Agenda
Sewer Inspection with CCTV & MSI
Data Review and Management
Developing Prioritized Improvements for Cleaning
Developing Prioritized Rehabilitation Programs
Lessons Learned on Cleaning Project
Design of Rehabilitation Program
3
Project Location
4
Combined/Separate Sewer System
Miles of Pipe
Interceptor Sewers 13
Trunk Sewers 31
Collection System 92
Total System 136
Pipeline Asset ManagementA Continuous Multi-Step Process
GIS Data
Hydraulic Model
O&M Data
Field Samples / Inspections
History of Problems
GIS Based Risk-Analysis and Ranking
CMMS
CCTV Software
Defensible &
Sustainable
Capital
Planning
Long-Term Needs Analysis
Statistical
Condition Estimation
Risk = COF X LOF
Capital Imp. Programs
Decision Framework
Condition Assessment
Improved O&M
Monitor Success & Benefits
CCTV, Sonar, Laser Equipment & Data
CCTV, Laser & Sonar
13 Miles (71,000’) of Interceptors
~250 pipes
24” to 72”
Data
13.3 miles CCTV, Laser, Sonar, GIS Mapping
ICOM software
Interactive, Maps/PACP
Video, PDF Reports
Pipe is Buckled & Flow is 30%
Restricted
CCTV & Laser Review: CRW Harrisburg PA
CCTV & Laser Review: CRW Harrisburg PA
Sonar Data / Graph Review : CRW Harrisburg PA
Sonar Data / Graph Review : CRW Harrisburg PA
Many sewers are 50% to 75% full of water and 25% full of settled debris
Prioritized Cleaning Program: Harrisburg PA
Must review maximum, average debris depths and sediment volume
Interceptor Sewer Cleaning Design & Bidding
35,000 LF of sewer 36” to 60”x72” noncircular;
Estimated 2300 Tons of solids from sonar
3 Bidders: $1.4M to $1.6M
Average - $25 per linear foot cleaning
$145 per ton to dispose (range of three bidders $100 to $145)
$100,000 for mobilization., demob. and traffic control
Interceptor Sewer Cleaning Design Plans
Heavy Cleaning Equipment & Setups
Contractor: Terra / Taplin Group
Hose Reels 1.5” Hose reels up to 1500 linear feet on skids (moved by forklifts)
Heavy Cleaning Equipment & Setups
Booster Pump Truck
Direct connections to fire-hydrant for constant flow
Specially build truck boosts flows and pressures
2000 psi
180 gallons per minute
Heavy Cleaning Equipment & Setups
Nozzles, Flows and Pressures Specialty skids and nozzles
Moves debris with existing flows which helps move the debris
Step Cleaning ~ 25 feet per step
Heavy Cleaning Equipment & Setups
Right: Booster Pump/ hose to Jetter @ DSMH
Below: Combo Truck (Vactor & Jetter), skid mounted hose reel & air compressor
Heavy Cleaning Equipment & Setups Vactor
Step Cleaning ~ 25 feet per step & bring debris to DSMH
Air Compressor adds air to suction tube which forces debris upward
Constant decanting of water
100 to 300 linear feet per day
Sewer Debris Collection and Disposal
Collect ~ 20 to 30 tons per day (16 to 25 cubic yards per day) ~ 560 cf per day
Eg. 12”debris x 300’ = (772cf/27)x1.2= 34 Tons = ~11 Tons per 100 LF or 1T/10’
Clean 100’ to 300’ per day
Vactor Dumps into 8’x20’ roll-off boxes (3 each on site)
12 CY (13 tons) transferred per load to dump
1,500 CY Removed vs. 1700 1,700 CY Estimated
Post-Cleaning Sonar is Essential
Verify cleaning for each pipe segment
Post-Cleaning Sonar is Essential
Post CCTV often shows new/lower dry-weather mark & frequent high-flow water mark
Post-Cleaning Sonar is Essential
Biggest Challenges
Buried Manholes
> 1500 CY (1800 Tons) debris
Large Debris/Obstacles
Difficult Access
Holes in Pipes / Lost nozzle
Very cold winter
Biggest Challenges : Access and Cold
Biggest Challenges : Access and Cold
Suction piping down the hill to the manhole on the Riverwalk
Jet hose from truck
Biggest Challenges : Access and Cold
Paxton Creek Interceptor Rehabilitation
30
Interceptor Sewer Size Shape Length
60” h by 72” w Parabolic 5,000
48” h by 59” w Parabolic 7,600
42” h by 60” w Rectangular 400
Total 13,000
Unique shapes
Limited Access
Alternatives Geopolymers
CIPP
Estimated Costs
Bypass Pumping 23 CSOs
31
Paxton Creek Interceptor Rehabilitation
Buried Manhole
Paxton Creek Interceptor
DWF
WWF
Summary & Lessons Learned
How to Prioritized Cleaning and Rehab Recommendations
Costs and Benefits
Post Cleaning Sonar & Field Inspection
Construction Sites, Equipment, Setups
Debris Estimates from Sonar very close to actual debris removed
Contractor can perform about 25 tons per day of cleaning
New videos helped refine the rehab design
32
Questions