Steve Hubbs & Tiffany Caldwell University of Louisville Clogging in Louisville.
-
Upload
lindsey-morgan -
Category
Documents
-
view
219 -
download
3
Transcript of Steve Hubbs & Tiffany Caldwell University of Louisville Clogging in Louisville.
Steve Hubbs &Tiffany CaldwellUniversity of Louisville
Clogging in Louisville
This presentation:
• Provide some slope data from US Rivers.
• Present calculations for Specific Capacity and decrease with time at Louisville (clogging).
• Analyze Pump Test data from 1999 and 2004 for indications of Riverbed compression at Louisville.
• Analyze field data for flux and head
• Review calculations of riverbed hydraulic conductivity (K) for 1999 and 2004 at Louisville.
Typical RBF systems in US
• Smaller system capacity (5,000 m3/day)
• Recent tendency for large systems (100,000 m3/day) and larger
• Located very close to streams (30 meters from bank)
• Laterals extend under riverbed
Sites with RBF Systems
• Louisville, 20 MGD (45 MGD planned), Ohio River
• Cincinnati, 30 MGD, Great Miami River
• Somoma, CA. 45 MGD, Russian River
• Lincoln NE, xx MGD, Platte R
• Des Moines, KC,
• Considering: St.Louis, New York, others
0
50
100
150
200
250
300
350
400
450
500
0 100 200 300 400 500 600 700 800 900 1000
Distance from Mouth (km)
Wat
er S
urfa
ce E
leva
tion
(m
)
0
500
1000
1500
2000
2500
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Distance from Mouth (km)
Wat
er S
urfa
ce E
leva
tion
(m
)
Missouri River
Mississippi River
Platte River
North Platte River
Ohio River
RBF Sites
RIVERBANK FILTRATIONAn effective technique for public water
supply
– An ancient technology…documented in the Bible!• Exodus 7:24 “…dug around the Nile for water to drink.
Filtered through sandy soil near the river bank, the polluted water would become safe to drink.”
– Modern installations in Germany over 140 years old– Extensive development in US since the 1950s– Recent interest as a treatment technique for
Disinfection By-Product and Pathogen Regulations
Indications of Clogging
• Louisville capacity decreases to 67% of original level over 4 years, hardpan present.
• Cincinnati “hardpan” forms when pumping at high levels under low-stream flow conditions
• Sonoma infiltration beds hard to penetrate and unsaturated below surface.
• Initial capacity of collector wells decrease after several years of operation.
Factors Impacting Yield
• Temperature (River, Aquifer, Well)
• Time (used as a surrogate for plugging)
• Pumping Rate and Driving Head
• Aquifer Characteristics (at riverbed, through bulk of aquifer, near wellscreen)
• Water Quality
Factors Restoring Yield
• Riverbed shear stress and scouring
• Biological “Grazing” (Rhine River)
• Mechanical Intervention (Llobregat River)
Sustainable Yield
• The long-range sustainable yield is a balance between all yield-limiting factors and all yield-restoring factors
• The question is: How do we measure and predict all of these factors?
• Focus of this part of the presentation: looking at the composite of plugging factors, and the impact of shear stress on sustainable yield.
Predicting Sustainable Yield
• Use a combined stochastic/deterministic approach.
• Specific Capacity = Flow/(river head - well head)
• Cs = a*(river temp) + b*(well temp) + c*(time)
ModelCs = intercept + (a) River T + (b) Well Temp + Plugging
Plugging is a function of Time (Time used as a dummy variable)
Linear Time
Log time
NOTE: This model is “forgiving” for inaccuracies in calculatingSpecific Capacity…in other words, if the assumption regarding Specific capacity being constant with Well Flow Q is WRONG, the regression for Temperature and Plugging will compensate for thiswrong assumption.
Raw Data (weekly averages)
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0 20 40 60 80 100 120 140 160 180 200
Week
Te
mp
F, L
ev
el F
t, Q
MG
D
Well Level
Well Flow
Well Temp
River Temp
River Level
Raw Data for Regression Model
30.0
40.0
50.0
60.0
70.0
80.0
90.0
1 21 41 61 81 101 121 141 161 181 201Week
Tem
pera
ture
: F
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Spe
cific
Cap
acity
: MG
D/f
eet
of d
rivin
g he
ad
River Temperature
WellTemp
Specific Capacity
Model with Temperature only
-0.300
-0.200
-0.100
0.000
0.100
0.200
0.300
0.400
0.500
0 20 40 60 80 100 120 140 160 180 200
Period (weeks)
Sp
ecif
ic C
apac
ity
(no
rmal
ize
d a
bo
ut
mea
n)
Regression: Cs = (0.491-0.48) + .0044 Well Temp + .0036 River Temp
R = .62F = 52
Actual
Predicted
Figure 5: Regression vs Actual, Linear Time
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0 20 40 60 80 100 120 140 160 180 200
Time, weeks
Sp
ec
ific
Ca
pa
cit
y (
no
rma
lize
d t
o m
ea
n o
f 0
.49
1 M
GD
/ft)
Cs = (0.491-0.41) + .0071 Well Temp + .0013 River Temp + -.0015 Linear Time
R = .91F = 266
Actual
Predicted
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0 20 40 60 80 100 120 140 160 180 200Period (week)
Spe
cific
Cap
acity
(no
rmal
ized
to
mea
n of
0.4
91 M
GD
/ft)
Cs (MGD/ft) = (0.491-.013) + .0045 (Well Temp. F) + .0018 (River Temp F) - .095 (Ln (Time week))
R = 0.96F = 583
Specific Capacity immediate followingflood event is greater than predicted
Period of flooding
Actual Data
Predicted Values
Regression Model, “cleaned data”
Projection of Model-20 years
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0 200 400 600 800 1000 1200
Time (Weeks)
Spe
cific
Cap
acity
(no
mal
ized
to
mea
n of
0.4
91 M
GD
/ft)
Point of Projection
Extrapolation with Jump
-0.400
-0.300
-0.200
-0.100
0.000
0.100
0.200
0.300
0.400
0.500
0 200 400 600 800 1000 1200
Week
Sp
ec
ific
Ca
pa
cit
y (
no
rma
l to
me
an
of
0.4
91
MG
D/f
t))
Projected
jumpjump jump
"Jump" is an added .0022 MGD/ft every 4 years to model
Modeled
September 9, 2004
Impact of 4 month layoff, 2004
• Pump failures resulted in long downtime
• Pumps off during high flow events of spring 2004
• Pumps restarted July 28, 2004
• Pump test of 1999 repeated
Projection with Jumps-capacity in MGD
0
10
20
30
40
50
60
70
0 200 400 600 800 1000 1200
Time (weeks-20 years)
Max
Well
Capaci
ty-M
GD
Jumps
ExtrapolationHistory
August 2004 (predicted)
Specific Capacity: Measured: 0.545 MGD/ftPredicted: 0.36 MGD/ft
measured
Specific Yield Calculations
• Adjusting for temperature, the calculated specific capacity for 2004 is 0.645 MGD/ft at week 4 of pump test.
• A similar calculation for specific yield was 0.848 for 1999 after week 4 of pumping.
• Current capacity approximately 76% of original after layoff and scouring event.
• Previous measurements indicated that capacity was approximately 67% of original.
Pump Tests at LWC
• 1999 Pump test
• 2004 Pump test
• Direct measures of infiltration
20 MGD Collector Well: Ohio River at Louisville
Silt ClayOhio River
Bedrock
Sand and Gravel
L4
Path 1Path 0 Path 2
50 feet
800 feet
Path nPath i
Figure 6.10 2-Dimensional Water Flow Paths from the River to Laterals
340
350
360
370
380
390
400
410
420
430
440
450
0 200 400 600 800 1000 1200 1400 1600 Distance from the Collector Well (feet)
Elevation (feet above sea level)
River Level = 420 feet
River Bed Surface
Piezometric Surface
Saturated Zone
Unsaturated Zone
Ohio River
Alluival Aquifer Sand and Gravel
Intersection of piezometric surface and Riverbed
Measured 2 feet below riverbed
Figure 6.5 Temperature Profile of Riverbank Filtration during Initial Pumping
0.0
5.0
10.0
15.0
20.0
25.0
30.0
0 2 4 6 8 10 12 14 16 18 20
Pumping time (Hours)
Tem
per
atu
re (
Deg
ree
C)
W1 W2 W3
Pump Start Time: 13:20, June 23, 1999Pumping Rate: 20 MGD
River Temperature: 26.5 oC
River WaterReached W2
River WaterReached W1
River WaterReached W3
The aquifer velocity q is measuredat the mid-point of curve at W1 (P39)at 1.08 hours for the 2 foot distance or 2 feet/hour
The measured head loss at P39 was10 feet across the 2 foot vertical distanceyielding a riverbed K value of:K=(2’/10’)(2ft/hour)=0.4 ft/hr (0.12m/hr)
P39
1999
Figure 7.1 Turbidity Results of the Ohio River and the Collector Well
0.01
0.1
1
10
100
1000
1/1
1/22
2/12
3/4
3/25
4/15
5/6
5/27
6/17
7/8
7/29
8/19
9/9
9/30
10/2
111
/11
12/2
12/2
31/
132/
32/
243/
174/
74/
28
Date (Year 2000 & 2001)
Tu
rbid
ity
(NT
U)
River Collector Well
n=480
Figure 7.2 Turbidity Removal as a Function of Filtration Distance
0.01
0.10
1.00
10.00
100.00
1000.00
0 10 20 30 40 50 60
Riverbank (Aquifer) Filtration Depth (feet)
Tu
rbid
ity
(NT
U)
Sampling Period: July 1999 - Feburary 2000n=21
W1 W2 W3
L4
River
2004 pump test repeat
Pump Test July 2004-P39
12
14
16
18
20
22
24
26
28
7/22/2004 0:00 7/27/2004 0:00 8/1/2004 0:00 8/6/2004 0:00 8/11/2004 0:00 8/16/2004 0:00 8/21/2004 0:00
Date
Te
mp
era
ture
- d
eg
ree
s c
elc
ius
395
400
405
410
415
420
425
Temperature
Piezometric Surface 0.6 meter below riverbed
Aquifer velocity q calculated at 20.6 oC at 3.3 hours for the .6 meter distance
Riverbed K value calculated at K=(2'/12.5')(2'/3.33hrs)=.096ft/hr = .03m/hr
Head loss across riverbed is measured at 3.8 meters
Start pump test
0.6 meter below surface
Temperature Data-Pump Test Start-up
0
5
10
15
20
25
30
0 50 100 150 200 250 300 350 400
Hours from start of test
Tem
per
atu
re-d
egre
es C
1999 Pump Test
2004 Pump Test
Temperature measured 3 meters below the riverbed
3 meters below surface
2004 Pump Test Data-Temperature and Piezometric Surface 3 meters below riverbed
-5
0
5
10
15
20
25
30
7/22/04 0:00 7/27/04 0:00 8/1/04 0:00 8/6/04 0:00 8/11/04 0:00 8/16/04 0:00Date
Tem
per
atu
re d
egre
es C
390
395
400
405
410
415
420
425
Pie
zom
etri
c el
evat
ion
Piezometric Water Level
TemperatureRiver Level - 420 feet
Riverbed elevation ~ 403 feet
Piezometric surface crosses riverbed
Temperature Data-Pump Test Start-up
0
5
10
15
20
25
30
0 10 20 30 40 50 60
Hours from start of test
Tem
per
atu
re-d
egre
es C
1999 P37 (3.0m)
2004 P37 (3.0m)
2004 P39 (.6m)
What’s going on?
330
340
350
360
370
380
390
400
410
420
430
440
450
0 200 400 600 800 1000 1200
Ohio River
Lateral L-4
Geokon Probe P37
t=20 min
t=2 days
BEDROCK
Sand and Gravel Aquifer
Piezometric surface
Geokon Probe P39
330
340
350
360
370
380
390
400
410
420
430
440
450
0 200 400 600 800 1000 1200
Ohio River
Lateral L-4
Geokon Probe P37
t=20 min
Several months
BEDROCK
Sand and Gravel Aquifer
Compressed Riverbed
Piezometric Surface
Interpretation of 2004 Temp data• Pump test starts with aquifer saturated to 420’.• As head increases, vertical velocity increases and
piezometric surface drops.• After 8 hours, the piezometric surface intersects
and drops below the riverbed. Riverbed conductivity reduces sharply, and the flow path shifts from vertical to horizontal.
• The piezometric surface continues to extend, increasing the distance of flow and bringing in cooler aquifer water. Minimal flow is passing P39.
• The piezometric surface stabilizes, and temperature increases to river temperatures.
330
340
350
360
370
380
390
400
410
420
430
440
450
0 200 400 600 800 1000 1200
0
Winter: T = 2oC Summer: t = 28oC
Piezometric Surfaces: Summer 2002 and Winter 2003
14oC
22oC
Direct Measure of Riverbed Flux Rate
• Seepage meter procedure modified for deep river use– Heavy “can” 1 sq. foot surface (0.093 sq meter)– Flexible connection to surface– Stilling well at river surface– Camera to observe riverbed conditions
Problems with flux measurement
• Wind, Waves, and Current are enemies
• Unable to work when river velocity exceeds 1 mph (1.6 km/hour) due to erosion of seal
• Wind/waves make boat and stilling well pitch
• It takes near-perfect conditions to get repeatable data
Seepage meter“can”
Hose to Attach to Bladder
In StillingWell
Stilling Well
330
340
350
360
370
380
390
400
410
420
430
440
450
0 200 400 600 800 1000 1200
Ohio River
Lateral L-4
Geokon Probe P37
t=20 min
Several months
BEDROCK
Sand and Gravel Aquifer
Piezometric Surface
No flux Area of high flux measurement
Calculating Riverbed K from direct measurement of infiltration rate
• Approach Velocity measured at .3 to 1 meter/hour• Porosity assumed at 0.2• Aquifer velocity q = (.3/0.2) = 1.5 m/hour• Head loss across riverbed at 0.6 meter depth is 6 meters
• K=(L/hL)(q)= (0.6/6)1.5m/hour = 0.15 m/hr
• Measured range based on approach velocities was 0.15 to 0.45 m/hour
Summary of Measured Riverbed K values
• At identical points (P39, 0.6m depth)– 1999 temperature-derived value = 0.12 m/hr– 2004 temperature-derived value = 0.03 m/hr
• From direct measure of flux across riverbed– Max 2003 flux-derived value = 0.45 m/hr– Typical 2004 flux-derived value = 0.15 m/hr– Max 2004 flux-derived value = 0.38 m/hr
Measuring Riverbed Compression
• 0.33 meter Drift Pin attached to 1 meter rod
• Dropped a distance of 0.58 meters.
• Penetration into riverbed observed by underwater camera.
• Submerged trees are the enemy!
Results of Penetrometer
• Riverbed surface varies considerably.
• Drift pin penetrates up to 0.33 meters in undisturbed areas…typical is 0.15 meters.
• Penetration is less than 0.05 meters in areas of riverbed compression near well.
• Additional measurements needed to define area of riverbed compression.
Ongoing Work at Louisville
• Mapping infiltration rates.
• Mapping riverbed compression area.
• Proceeding with expansion of wellfield from 20 MGD to 60 MGD total capacity (75,000 m3/day to 225,000m3/day)
• Using vertical wells (as opposed to horizontal collectors)
Discussion
• Any other observations regarding compression of riverbed?
• Do the values of riverbed “K” look right?• Any other theories about riverbeds under
unsaturated conditions?• Guidance regarding design and operation of
RBF systems with regards to unsaturated conditions under the riverbed?
Figure 5.1 Particle Size Distribution of Aquifer Materials at Different Depths(at Collector Well)
0
10
20
30
40
50
60
70
80
90
100
0 0.5 1 1.5 2 2.5 3 3.5 4
Particle Size (mm)
Cu
mu
lati
ve P
erce
nt
Ret
ain
ed
85-90 ft 80-85 ft 75-80 ft 70-75 ft 65-70 ft 60-65 ft 55-60 ft
Fine Sand Course Sand Very Fine Gravel Fine Gravel
Laterals located near the bottom of this layer
PrecipitationPrecipitation
Direct Runoff
Direct Runoff
Direct Runoff
Soil and clay
Water Table
Sand and GravelShale
Shale
Shale
Shale
Limestone
Zone of solutionaldevelopment
Zone of poorcirculation
Eva
pora
tion
Tra
nspi
ratio
n
Ohi
o R
iver
Velocity profiles from Doppler data (USGS)
OHIO RIVER DATA AT BEPWTPvelocity depth shear
velshr strs fric
slopefeet/sec feet feet/sec Newtons per
10005.34 37.545.53 35.9 -1.70 -8.35 -0.0745.50 34.26 0.26 0.19 0.0025.13 32.62 3.02 26.26 0.2345.57 30.98 -3.41 -33.58 -0.2995.31 29.34 1.91 10.55 0.0945.25 27.7 0.42 0.50 0.0044.91 26.06 2.23 14.32 0.1284.96 24.42 -0.31 -0.27 -0.0024.82 22.78 0.81 1.87 0.0174.67 21.14 0.80 1.86 0.0174.31 19.5 1.78 9.17 0.0824.48 17.86 -0.77 -1.73 -0.0154.24 16.22 1.00 2.87 0.0264.21 14.58 0.11 0.04 0.0004.18 12.93 0.10 0.03 0.0004.17 11.29 0.03 0.00 0.0004.09 9.65 0.20 0.12 0.0013.31 8.01 1.68 8.09 0.0723.39 6.37 -0.14 -0.06 -0.0010.01 0.014.67 21.96 0.42 1.68 0.015
Assumptions/Problems in Velocity Profile measure of
Shear Stress
• Uniform bed surface and predictable interface velocities based on particle size.
• Theoretical curve based on uniform flow (and implications from river bedforms)
• Doppler velocities limited by technique: unable to read velocities at the top and bottom 5 feet of the profile.
Stream Slope Calculations for Shear Stress
• Data available from USGS via internet.
• Variety of stream flow conditions available.
• Yields an averaged shear stress for a particular stream reach.
• Influenced by stream characteristics: bedforms, obstructions, curves.
Inferring Maximum Shear Stress by Bedload Transport
• Larger shear stresses required to move larger rocks.
• Smaller shear stresses required to move gravel and sand.
• Data available to indicate minimum shear stress to move riverbed particles: sand 0.2 Newtons/sq. meter; gravel 3 N/sq. m
Figure 2: Particle Size Distribution Analysis-Riverbed and Suspended SolidsUSGS Data, 1979-1982, Ohio River at Louiville
0
20
40
60
80
100
120
0.001 0.01 0.1 1 10 100
Particle Size
Per
cen
t P
assi
ng
SS -11/30/1979
SS -6/10/1981
SS-1/27/1982
bed-1375' from KY bank
bed-1650' from KY bank
bed-1850' from KY bank
bed-2000' from KY bank
bed-2200' from KY bank
bed-2500' from KY bank
bed-2700' from KY bank
bed-2900' from KY bank
bed-3900' from KY bank
bed-4120' from KY bank
SS-6/2/82 mid-stream
SS-6/2/82 Ind side
Suspended Solids Indiana side Riverbed
Main channel and Kentucky side Riverbed
Flow = 301,000 to 434,000 cfsTSS = 482 to 698 mg/l
Flow= 239,000 cfsTSS=408-466 mg/l
Future Work at LWC
• Direct measure of riverbed conductivity
• Analysis of additional streams under varying conditions
• Influence of barges?
Shear Stress: Definition
• Shear stress is the resistance imparted by a fixed surface (streambed) on a moving fluid.
• This is similar to the friction forces at work in pipe headloss, and provides for the “head loss” in river system.
• Units: Newtons/sq. meter; psi/sq. foot
• Occurs when shear stress imparts a force on the riverbed adequate to move the particles of the riverbed.
• Is a function of stream velocity at the riverbed, and the particles (size, shape, density) making up the riverbed itself (sand and gravel).
Riverbed Scouring
Comparison of Models
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0 20 40 60 80 100 120 140 160 180 200
Time in Weeks
Speci
fic C
apaci
ty (
norm
al t
o m
ean)
Temp only: Cs = -.323 + .0024 Well T + .0026 River T R=.39, F=16Linear time: Cs = -.21 + .0036 Well T + .0014 River T - .0012 Time R=.61, F = 36Log time: Cs = 0.070 + .0018 Well T + .0018 River T - .070 time R=.61, F=36
Actual Data
Linear Time
Log Time
Temperature Only
N
Ohio River
L3 L6
L4 L5
L7 L2
M1
M2
M4
M3
L1
Well
Lateral
Figure 4.3 Locations of Area-wide Water Quality Sampling Wells
200 Ft
240 Ft
100 Ft