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Leveraging Hydraulic Sewer Modeling
and Pipe Condition Data for a Robust and Sustainable GIS
April 7, 2011
NELSON ESQUIVEL AND MAZEN KAWASMI
Agenda
• GIS Perspective on the Wastewater Master Plan Process and Development of Hydraulic Sewer Model
• GIS Perspective on the Risk Base Assessment (RBA) and Condition Data
• Case Study: City of Irving Wastewater Master Plan and RBA Condition Assessment
2
What is a ? “A tracking parameter that is tied to an asset
and does not change over time.”
What is a ? “An application or software package that
performs tasks independently and is not
seamlessly linked to other systems.”
What is ? “Linkage of critical data residing in different sources providing users with enhanced information.”
What is a ? “A collection of activities that defines roles and responsibilities and provide sustainable work flow.”
3
Terminology
Basic Definitions:
A GIS Perspective: Wastewater Master Plan
Process and Development of Hydraulic Sewer Model
5
Why is a Master Plan needed?
Why Do It?
• Experiencing Serious Operational Problems
– To Identify System Deficiencies
• Experiencing Rapid Growth
– Provide Adequate Capacity Expansion
– Make Growth Self-Supporting (Impact Fee Study)
• A Tool for Developing Annual Budgets
– Phased Capital Improvement Plans
Typical Wastewater Master Plan Process
Population & Wastewater Flow
Projections
Field Testing and Calibration
Wastewater Collection Planning
Model Development
Strategic Planning
Wastewater Facilities Planning
6
CAPITAL IMPROVEMENT
PLAN
RBA Asset Management Prioritization
Model Selection
GIS Coordination
Features Infoworks CS
Bentley SewerGems
H2OMap SWMM
Info SWMM Hydra
Dynamic Model Yes Yes Yes No
Backwater Calculations Yes Yes Yes No
Inference Tools Yes Yes Yes No
Data Flagging Yes No Yes No
GIS Editing Yes Yes Yes Yes
Background GIS Layers Yes Yes Yes Yes
Rain Gauge Inputs Yes Yes Yes No
Can Define RDII Yes No Yes Yes
Validation Tools Yes No Yes No
Special Structures Yes Yes Yes Yes
3D View Yes No No No
EPA SWMM5 Import/Export Yes Yes Yes No
• Host Workshop to Demo Real Life Industry Examples
• Leverage Data Silos Available:
– CMMS, GIS, CCTV Data and Condition Scoring Database
• Select Software that Meet City’s Existing and Future Needs
• Work with City Staff to Determine In-House Applications Going Forward
Wastewater Model Selection Process
SOFTWARE EVALUATION CRITERIA
7
Data Sources for Model Development
Contours to determine manhole elevations
and areas with low elevations.
Water Billing Meter data by parcel to determine
usage for wastewater load allocation.
Using Existing GIS
• Identify or Establish a common link between GIS and the Model - Unique Identifier
• Use GIS Topology and Aerial Imagery to check for connectivity issues and to resolve alignment issues.
• Identify sewer selection sets for model development
• Develop large sewer line profile maps of data input for quality control review by both Consultant and City staff
Existing Models
• Compare existing model data with GIS data for selection set facilities.
• Review data flagging and update GIS where model data warrants.
• Review model data for special structures – weirs, convergent and divergent manholes, lift stations, etc. for input into updated model.
As-Builts Drawing Research
• Placing a person in City’s office to research and record critical missing attribute data
• Obtain digital electronic files (i.e. PDF, TIFF, etc) • Utilize design plans to populate missing attribute data for
ongoing projects.
• Collect lift station as-builts and pump performance data for input into model.
Surveying
• Conduct GPS and conventional surveying where necessary to collect accurate manhole location data.
• Conduct measure downs for field verification and use in determining missing invert elevations.
– Option 1
• Minimum of every 3rd manhole for each selection set line, divergent and convergent manholes, major PI’s, weirs, and junction boxes.
– Option 2
• Major junctions, Diameter Changes, Lift Stations, Every 5th manhole
– Option 3
• Minimum of every 3rd manhole for larger interceptors, Major PI’s, and Lift Stations
What the model checks for…
13
Nodes in Close Proximity
Pipe Split Candidates
Intersecting Pipes
Disconnected Nodes
Parallel Pipes
Orphan Pipes
N 1 N
2 N
3
N 4
N 1 N
2 (only)
N 3
P 1
P 2
P 1
P 2
P 3
P 1
P 2
P 1
P 2
P 3
P 4
P 1
(over)
P 2
(under) P
1
P 2
What the model will find…
14
Below is an example of a sewer profile showing inaccurate attribute data within the GIS.
The sewer profile above represents correctly attributed data that has been verified and updated in the model.
Man
ho
le
Man
ho
le
15
Data Sources Inside the Model
• Implementing a Process to track data sources.
– Model development
– Model calibration
– Hydraulic analysis
• Color Scheme in flagging represents data confidence level and is tracked through the modeling process.
Develop Process to Flag Various Data Sources in the Model
Model / GIS Business Process
16
Step 1: Obtains Latest GIS Database
Step 2 : Import Changes Into
Model
Step 3: Check for Connectivity
and Other Inconstancies in
the Data
Step 4 : FNI Submits Attribute
Updates and Connectivity / Data Issues to
city’s GIS
Step 5 : GIS Researches
Connectivity / Data Issues
through Multiple Sources
Step 6 : Update GIS Database Changes and
Additional Parameters
Step 7 : Confirm that changes have
been updated in the GIS
Model
Software
17
GIS
17
Wastewater Model Initial Benefits
GIS
GIS Benefits of Master Plan
18
• Patterns are often more clearly observed when viewing mapped data.
• A Master Plan can help you organize and centralize your data.
• Field Collected GPS Data from the Master Plan Can Enhance Your GIS Database along with your wastewater model.
• Making better business decisions
A GIS Perspective: Risk Base Assessment (RBA)
and Condition Data
• Desire to graphically track sewer condition over time in a similar manner as a pavement management systems provides for roadways
• Desire to identify areas of highest risk and exposure
• Need to maximize value of rehabilitation dollars with increasingly limited resources
20
Why is a Risk Base Assessment Plan needed?
Risk Based Assessment Flow Chart
21
Low Impact
Medium Impact
High Impact
Very High Impact
Low Medium High Very High
Very Good
Good
Fair
Poor
Very Poor
Very High
High Medium
Low
Pipe Age
Pipe Material
SSOs & Stoppages
Infiltration/Inflow
Pipe Corrosion
Condition Scores
Very High
Impact
High Impact
Medium Impact
Low Impact
Capacity Scores Criticality Scores
Condition Risk
Matrix
Capacity Risk
Rating
Low Impact
Medium Impact
High Impact
Very High
Impact
Very Good
Good Fair Poor Very Poor
Condition Risk
Rating
Capacity Risk
Matrix
High Risk = Short Term CIP
Medium Risk = Long Term CIP
Condition of the Wastewater Assets
What is the Likelihood of an Asset Failing? • Develop a grading system that scores each asset by its
condition.
• Condition parameters to consider:
22
Pipe Diameter (GIS)
Material (GIS)
Age (GIS)
Level of infiltration/inflow
Soil conditions (GIS)
What parameters have data available and are applicable and how should they be weighted?
SSO, sewer stop & work order history (CMMS)
CCTV condition assessment data
Pipeline corrosion
Very Good
Good
Fair
Poor
Very Poor
Condition Scores
Criticality of the Wastewater Assets
• What is the Consequence of a Sewer Line or Lift Station Failing?
• Criticality parameters to consider: – Number of Upstream Wastewater Connections
– Line Size and Line Access Issues
– Proximity to: • Environmentally Sensitive Areas
• Schools / Hospitals
• Major Road Crossings
• High Density Commercial Developments
23
Very High
Impact
High Impact
Medium Impact
Low Impact
Criticality Scores
Capacity of the Wastewater Assets
Capacity parameters to consider:
• When does an overflow occur?
-Ground elevation vs. Rim elevation
• Ratio of flow depth to pipe diameter, d/D
-d = depth of water ÷ D = Pipe Diameter
• Ratio of flow to pipe capacity, q/Q
-q = flow in pipe ÷ Q = designed flow
• What level of surcharge is acceptable?
-Define a distance below the rim
24
Very High
High Medium
Low
Capacity Scores
Risk Based Prioritization Screening
Risk Rating for each pipeline:
• Condition Risk =
(Condition Assessment Score)
x
(Criticality Assessment Score)
• Capacity Risk =
(Capacity Assessment Score)
x
(Criticality Assessment Score)
• Review Scoring to Identify CIP Candidates
25
Low Impact
Medium Impact
High Impact
Very High
Impact
Very Good
Good Fair Poor Very Poor
Low Impact
Medium Impact
High Impact
Very High Impact
Low Medium High Very High
Case Study: Irving Wastewater Master Plan
and Condition Assessment Study
Background on Irving’s Collection System
• 2008 Population – 214,073
• Wholesale Customer of TRA
• Major Interceptors up to 54” in diameter
• 3.8 Million Linear Feet of Sewer Pipe
• 12 Major Basins
• History of Failures on Concrete Pipes
27
GIS Update for Larger WW Infrastructure
Wastewater Model
Development
Wastewater Flow Projections & TRA Coordination
Flow Monitoring
& Model Calibration
RISK BASED PRIORITIZED CAPITAL IMPROVEMENT PLAN
Wastewater System Master Planning Process: City of Irving
28
Condition Analysis
Criticality Analysis
Hydraulic Capacity Analysis
TxDOT/ Development
Conflict Analysis
GIS vs. Original Hydroworks Model
Original Hydroworks
City’s GIS
29
Updating the Current GIS to Match Exiting Sewer Model
• Old Model Lines did not match current GIS
• Old model utilized Unique ID needed in the GIS
• Unique ID was populated in sequential order by upstream line
• Some connectivity issues were discovered by new sewer model
• As-Build research and Survey was needed in some areas
• Model and GIS needed to have a one-to one relationship.
Identified GPS Survey Point
GIS vs. Original Hydroworks Model
GIS vs. new H2OMap SWMM model
Utilized the previous Infoworks Model, GIS data, as-builts and survey data to update & complete
the wastewater model. Original
Hydroworks City’s GIS
Identified GPS Survey Point
City’s GIS
New H20Map SWMM
30
Updating the Current GIS to Match Exiting Sewer Model
GIS Update: Data Used
31
• Existing GIS Database
• As Built Data
• Survey Data
• Mark-Ups from City’s Field Operations
GIS Updates: The Process
32
• Researched sewer lines that were critical to the Model and were either fragmented or required connection clarification.
• Created an exact duplicate of the City of Irving SDE in order to facilitate the data exchange between FNI and Irving's GIS Department.
• Linked the As-Builts to GIS in order to streamline the research process.
• Field Operations were involved in areas where no As-Builts were located.
• Surveyed critical areas with manhole x,y,z and invert elevation where field clarification was needed.
• Populated and flagged critical attribute data inside the GIS
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GIS Update: Critical Lines Research
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GIS Update: Critical Lines Research
GIS Update: Attribute Updates
35
• Tracked by person who last updated the GIS
• Provided the source of the attribute data
• Provided location of the source of the attribute data
• Identified if the sewer line was modeled
GIS Updates: The Benefits
36
• Developed confidence in the GIS by flagging attribute data by source.
• Business process developed for sustainable Model to GIS Linkage and vice versa.
• GIS is still the primary source for attributed and spatial Data
• City of Irving used FNI Database to update their GIS on verified Lines.
• Better Data in the GIS makes for better decisions in RBA process.
QUESTIONS?...
37