Transcript - SEWER REHABILITATION - A TEN-STEP STRATEGIC PLAN GEORGE KURZ, P.E., DEE

- SEWER REHABILITATION A TEN-STEP STRATEGIC PLAN
GEORGE KURZ, P.E., DEE
615-252-4441 [email protected]
* A significant portion of this work was conducted
with CTE-AECOM as part of the Nashville Overflow
Abatement Program 1991-2005
SEMINAR OBJECTIVE
Teach a proven, successful strategy.
SUCCESSFUL REHAB
FACTORS
• DEFINE GOALS
• EXTENSIVE FLOW MONITORING &
STANDARD PROCEDURES
• LATERAL REHABILITATION
• “TARGETING” – STOP WATER MIGRATION
• ACCOUNTABILITY – VERIFY DESIRED
RESULTS
TOTAL SYSTEM APPROACH
- Nashville Policy GOAL: “CONTAINMENT” FOR FLOWS FROM 5YEAR, 24-HOUR RAINFALL
POLICY:
ALL SERVICE LATERALS CONNECTED TO THE
REHABILITATED PIPES WILL BE RENEWED TO
THE EASEMENT LINE OR THE PROPERTY LINE

ALL MANHOLES CONNECTED TO
REHABILITATED PIPES WILL BE RENEWED

1. Identify Goals
2. Select Target Area
Ten steps
3. Quantify Problem
4. Locate Defects
5. Select Pipe Segments
6. Estimate Cost-Benefit
7. Design & Install
8. Verify Performance
9. Follow-up Flow Monitoring
10. Calculate O & M Savings
1 - IDENTIFY COMMUNITY GOALS
“ELIMINATE OVERFLOWS AND BASEMENT BACKUPS”
• PERIOD OF TIME: 2
YEARS ?, 5 YEARS ?
• RELATE TIME TO
RAINFALL EVENT
RETURN INTERVAL
• NO OVERFLOWS
LEGALLY SANCTIONED
2 - SELECT TARGET AREA
• FLOW MONITORING NETWORK (~100,000
L.F.)
• CALCULATE OBSERVED & POTENTIAL I/I
• HYDRAULIC MODEL
• IDENTIFY CAPACITY PROBLEMS
• PRIORITIZE TRIBUTARY AREAS
DETECT CAPACITY PROBLEMS
(KIRBY 3 - MANNINGS SCATTERPLOT)
5.0
4.5
Velocity (ft/sec)
4.0
3.5
CAPACITY
LOST TO
HINDERED
FLOW
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
1
2
3
4
HC=5.4, full pipe = 4.766 m gd
5
6
7
8
9
10 11
Depth (inches)
12 13 14 15 16 17 18 19
Mannings Vel
Metered Vel
variable n adjusted
hi-Flow
3 - QUANTIFY PROBLEM CONDITIONS
• INTENSIVE MONITORING IN TOP
PRIORITY TRIBUTARY AREAS (8,000 15,000 L.F.)
• OBSERVED AND POTENTIAL I/I
• ADDITIONAL CAPACITY PROBLEMS
SUM OF TRIBUTARIES
=53.5 mgd
WEST PARK METER
=32 mgd
POTENTIAL I/I = 21.5mgd
WEST PARK PUMPING
STATION - 32 mgd
Clifton 2 - 1.6mgd
1.6mgd Clifton 1
2.0 mgd Clifton 3
11 mgd West End
Clifton 4 - 1.3mgd
Murphy Rd.- 4.2mgd
2.1 mgd White Br
1.5 mgd Sugartree 1
Sugartree 2 - 12.9mgd
15.3 mgd Brentwood
I/I REMOVAL EFFECTIVENESS
- ACCOUNT FOR POTENTIAL I/I !!
Example: 52% I/I REMOVAL
2.5
PROJECTED METER
READING
I/I (mgd)
2
POTENTIAL I/I
1.5
PIPE CAPACITY
RESTRICTED FLOW
1
I/I AFTER REHAB
0.5
0
0
1
2
3
RAINFALL (inches-24 hours)
4
5
“POTENTIAL” I/I
• I/I Which Cannot Enter the Sewer Because
the Pipe is Already Overloaded!
• Overall I/I Removal Goals
• Monitor Depth & Velocity
• Extrapolated
DATA INTERPRETATION
• 24-hour rainfall more reliable than peak hour rain for
predicting peak design I/I
• AMC – Antecedent Moisture Condition is critical for
selecting valid rainfall events
• HINDERED FLOW - POTENTIAL I/I
There are
ways to correct for this, however the analyst must
be aware of this condition
• Underestimating the peak flow can result in the
inadequate design of new facilities
• Need to standardize criteria
PEAK
INFILTRATION/I
NFLOW RATE
(mgd)
REGRESSION ANALYSIS
PEAK I/I vs 24-HOUR RAINFALL
MI-09 YEAR 2004-05
140
120
100
80
60
40
20
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
24 HOUR RAINFALL (inches)
PEAK HOUR BEST FIT LINE
95% CONFIDENCE
95% CONFIDENCE
Peak-hour flow
(24-hr rain
vs. Peak-hr rain)
REMAINING CAP.(I/I)
PEAK
INFILTRATION/INFLOW
RATE (mgd)
PEAK HOUR RAIN I/I
COMPARISON OF
RESULTS
REGRESSION ANALYSIS
PEAK I/I vs. PEAK HOUR RAINFALL
MI-09 YEAR 2004-0
0.4
1.6
200
150
100
50
0
0.0
0.2
0.6
0.8
1.0
1.2
PEAK HOUR RAIN I/I
PEAK
HOUR
BEST FIT(inches)
LINE
24
HOUR
RAINFALL
95% CONFIDENCE
95% CONFIDENCE
1.4
1.8
REMAINING CAP.(I/I)
2.0
Which type rainfall pattern puts the most stress
on the system – for a standard return interval,
design storm?
Summer ?
Or Winter ?
TYPICAL RAINFALL
Type II Rainfall* – Characterized by short-term,
high intensity thunderstorms and also by
long-duration frontal storms.
* USDA-SCS 1986
NASHVILLE
5-Year, 24-Hour & 3-Hour Design Rainfall
2
1.8
5-YEAR, 3-HOUR
Peak Rain =1.97"
Depth (inches)
1.6
1.4
5-YEAR, 24-HOUR
Peak Rain =1.26"
1.2
1
0.8
0.6
0.4
0.2
0
0
5
10
15
20
25
Hours
24-Hour rain
3-Hour Rain
Design Storm Peak: 2-Yr, 24-Hr vs. 3-Hr
PEAK I/I vs 24-HOUR RAINFALL
CMC02 - YEAR 2003
4.0
Peak hour I/I from 2-Yr, 24-Hr
Storm is 3.89 mgd with good
3.5
r= 0.91
3.0
level of confidence
95% Conf. =
16%
2.5
2.0
1.5
1.0
0.5
0.0
0.00
0.40
0.80
1.20
1.60
2.00
2.40
24 HOUR RAINFALL (inches)
PEAK HOUR RAIN I/I
95% CONFIDENCE
PEAK HOUR BEST FIT LINE
95% CONFIDENCE
Peak hour I/I from 2-Yr, 3-Hr
Storm is 2.35 mgd with poor
PEAK INFILTRATION/INFLOW
RATE (mgd)
PEAK INFILTRATION/INFLOW
RATE (mgd)
4.5
2.80
4.0
3.20
PEAK I/I vs 3-HOUR RAINFALL CMC02 2003 3-HOUR STO
3.60
REMAINING CAP.(I/I)
3.5
3.0
2.5
2.0
r= 0.47
1.5
95% Conf.= 87%
1.0
0.5
0.0
level of confidence
0.0
0.5
1.0
1.5
2.0
2.5
24 HOUR RAINFALL (inches)
PEAK HOUR RAIN I/I
95% CONFIDENCE
PEAK HOUR BEST FIT LINE
95% CONFIDENCE
REMAINING CAP.(I/I)
4 - LOCATE & IDENTIFY DEFECTS
• TELEVISE TARGET AREA SYSTEM (MAY
BE CONCURRENT WITH MONITORING)
• CATEGORIZE
DEFECTS WITH
RESPECT TO I/I
POTENTIAL
4 - LOCATE & IDENTIFY DEFECTS
(CONT.)
• “INVISIBLE” DEFECTS - ELECTRIC FIELD
LEAK DETECTION, SEGMENTAL
ISOLATION
• GROSS INFLOW (ROOF DRAINS, ETC.)
5 - SELECT SEGMENTS FOR
REHABILITATION
• CATEGORIZE & COLOR CODE LINES
– 3 OR MORE MAJOR DEFECTS
– 1-2 MAJOR DEFECTS
– NO MAJOR DEFECTS
• “3 OR MORE” - RENEW !
• CHECK ADJACENT SEGMENTS
• RENEWAL “INTENSITY” - RANGE OF 1520% FIRST ROUND
CONNECT THE DOTS
> 3 DEFECTS
< 3 DEFECTS
?
0 DEFECTS
25 % intensity
?
METER
?
?
REHABILITATE
SEWER REHAB STRATEGY:
HALT MIGRATION !
INVISIBLE DEFECT
LEAK
"DRY" DEFECT
POTENTIAL LEAK
LEAK
"NEW" LEAKS REVEALED FOLLOWING
TRADITIONAL REPAIRS
LINING OR REPAIR
6 - ESTIMATE COST-BENEFIT
• COMPARE RENEWAL COSTS TO: O&M
COSTS ($1.73 - $1.87/ 1,000 GAL)
• AT LEAST 50% I/I REMOVAL
• COSTS:
– LINING (8-10” CIPP) ~ $43 / LF
– LATERALS ~ $2,250 ea. (1/ 200 LF)
– MANHOLES ~ $1,000 -1,300 ea. (1/200 LF)
– ENGINEERING ~ 12% - 15% OF TOTAL
(GROSS= ~ $132/ft rehab)
7 - DESIGN & INSTALL REHAB
• HALT MIGRATION FROM OUTSIDE PIPE
• HALT MIGRATION (“TRACKING”) INSIDE
PIPE
• PROVIDE SEAL AT MANHOLE JUNCTION
• RENEW SERVICE LATERALS
(over 10,000 rehabilitated in Nashville)
LATERAL REHABILITATION
EFFECTIVENESS
DOWNINGTON, PA -area 5
38 laterals in 1,513’ CIP - 100% treated
97% reduction - 22 mg annually
STEGE SAN. DIST, CA - subarea N
111 laterals in 13,400’ Slip-PE & MH - 100%
86% reduction
NASHVILLE, TN - Oak Valley
63 laterals in 4,400’ CIP - 41% treated
77% reduction (20%-laterals) - 67 mg annually
8 - PERFORMANCE TESTING
• AIR-TEST SEWER SERVICE CONNECTION !
– MOST VULNERABLE PART
– NOT ACCEPTED UNTIL PERFORMANCE
VERIFIED
9 - FOLLOW-UP FLOW MONITORING
• QUANTIFY I/I REDUCTION
• STANDARDIZED I/I ANALYSIS
• TV DURING WET WEATHER
• RERUN HYDRAULIC MODEL
• DETERMINE IF DESIGN GOALS MET !
5-YEAR, 24-HOUR I/I REDUCTION (CU-01 1999-2002)
5.0
4.5
24-hour I/I (m g)
4.0
CAPACITY
3.5
3.0
I/I REDUCTION
BEFORE REHAB
2.5
2.0
1.5
AFTER REHAB
1.0
0.5
0.0
0
0.5
1
1.5
I/I Before Rehab
2
2.5
24-hour rainfall (in.)
I/I After Rehab
3
3.5
4
Linear (I/I Capacity)
4.5
STANDARDIZED I/I ANALYSIS
• DEFINES LEVEL OF CONFIDENCE FOR
PROJECTED I/I
• USES QA/QC CONTROLS THAT ARE
SIMILAR TO “STANDARD METHODS”
(nationally recognized)
Example: Typical Nashville Rainfall Event Analysis
1.600
FLOW (MGD)
ADF= 0.3 mg
(adjusted to match
beginning of storm
flow @ 0.99 mg)
WL02 2-01
1.200
0.3
1.000
0.25
0.800
0.2
0.600
0.15
0.400
0.1
0.200
0.05
0.000
0
Total Flow
A
2: M
00
A
4: M
00
A
6: M
00
A
8: M
00
10 AM
:0
0
12 A M
:0
0
P
2: M
00
P
4: M
00
P
6: M
00
P
8: M
00
10 PM
:0
0
12 P M
:0
0
AM
Hour
0.4
0.35
TIME (HOURS)
DRY WEATHER
ADF
0.45
1.400
05:45 07:45 09:45 11:45 13:45 15:45 17:45 19:45 21:45 23:45 01:00 03:00 05:00
:0
0
12
Average Flow, MGD
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
WET WEATHER
HYDROGRAPH
1.800
7 day dry flow
Characteristic Base Flow Curve
0.5
Infiltration/Inflow
Base Flow
Rain
2.11” Rainfall
24-hr I/I
=0.37 mg
RAINFALL (INCHES)
2.000
Peak-hr I/I
=0.738 mgd
NASHVILLE REHABILITATION EFFECTIVENESS
ANNUAL I/I REDUCTION FROM REHABILITATION
ANNUAL I/I REDUCTION (MG)
800
700
600
500
400
300
200
100
0
0
10,000
20,000
30,000
40,000
50,000
REHABILITATION LENGTH (FT)
ANNUAL I/I REDUCTION (MG)
Linear (ANNUAL I/I REDUCTION (MG))
60,000
EFFECTIVENESS
(a “rule of thumb”)
15-20%
REHABILITATION
INTENSITY
(including MH & laterals,
& in deteriorated areas)
~ 8-10 MILLION
GALLONS ANNUALLY
per 1,000 ft.
LINING or
REPLACEMENT
10 - CALCULATE O&M SAVINGS
• POSSIBLE 7-11 YEAR PAYBACK
(construction)
• PROVIDES DATA FOR FUTURE
PROGRAM PLANNING
• ACCOUNTABILITY TO COMMUNITY
PROGRAM PAYBACK COMPARED TO O&M
CHARGED
Years to Payback
35
8 Mill Gal Removed per Year/1,000 ft Lining
Total Program costs ~ $ 700,000/ mile
20% intensity
30
25
20
15
10
5
0
$0.80
$1.00
$1.20
$1.40
O & M ($ per 1,000 gal)
$1.60
$1.80
$2.00
Payback years
SUCCESSFUL REHAB
FACTORS
• EXTENSIVE FLOW MONITORING
• LATERAL RENEWAL TO EASEMENT
• “TARGETING” - LINING SELECTED BY
OBSERVED DEFECTS, AGE, PROXIMITY,
MIGRATION POTENTIAL, SURFACE
WATER
• PERFORMANCE (AIR) TEST LINE &
LATERAL
STRATEGIC GOALS MET
• I/I REDUCTION
• SSO REDUCTION
• STREAM IMPROVEMENT
NASHVILLE MEASURED RESULTS
For the 27 areas (94 miles) analyzed so far:
3.6 billion gallons I/I eliminated annually
49.6%
Annual I/I eliminated
53%
24-hour, 5-year I/I reduction
52.2%
Peak-hour, 5-year I/I reduction