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