Clogging in Louisville
Download
1 / 68

Steve Hubbs & Tiffany Caldwell University of Louisville - PowerPoint PPT Presentation


  • 111 Views
  • Uploaded on

Clogging in Louisville. Steve Hubbs & Tiffany Caldwell University of Louisville. This presentation:. Provide some slope data from US Rivers. Present calculations for Specific Capacity and decrease with time at Louisville (clogging).

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Steve Hubbs & Tiffany Caldwell University of Louisville' - tanika


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Steve hubbs tiffany caldwell university of louisville

Clogging in Louisville

Steve Hubbs &

Tiffany Caldwell

University of Louisville


This presentation
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
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
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


Riverbank filtration an effective technique for public water supply
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
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
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
Factors Restoring Yield

  • Riverbed shear stress and scouring

  • Biological “Grazing” (Rhine River)

  • Mechanical Intervention (Llobregat River)


Sustainable yield
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
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)




Steve hubbs tiffany caldwell university of louisville

RegressionModel, “cleaned data”




Impact of 4 month layoff 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
Projection with Jumps-capacity in MGD

Specific Capacity:

Measured: 0.545 MGD/ft

Predicted: 0.36 MGD/ft

August 2004 (predicted)

measured


Specific yield calculations
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
Pump Tests at LWC

  • 1999 Pump test

  • 2004 Pump test

  • Direct measures of infiltration




Steve hubbs tiffany caldwell university of louisville

1999

P39

The aquifer velocity q is measured

at 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 was

10 feet across the 2 foot vertical distance

yielding a riverbed K value of:

K=(2’/10’)(2ft/hour)=0.4 ft/hr (0.12m/hr)






Steve hubbs tiffany caldwell university of louisville

Ohio River

Geokon Probe P39

t=20 min

t=2 days

Geokon Probe P37

Sand and Gravel Aquifer

Lateral L-4

BEDROCK

Piezometric surface


Steve hubbs tiffany caldwell university of louisville

Compressed Riverbed

Ohio River

t=20 min

Geokon Probe P37

Sand and Gravel Aquifer

Several months

Lateral L-4

BEDROCK

Piezometric Surface


Interpretation of 2004 temp data
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.


Direct measure of riverbed flux rate
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
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


Steve hubbs tiffany caldwell university of louisville

Hose to

Attach to

Bladder

In Stilling

Well

Seepage meter

“can”



Steve hubbs tiffany caldwell university of louisville

Ohio River

t=20 min

No flux

Area of high flux measurement

Geokon Probe P37

Sand and Gravel Aquifer

Several months

Lateral L-4

BEDROCK

Piezometric Surface


Calculating riverbed k from direct measurement of infiltration rate
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
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
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
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
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
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?




Assumptions problems in velocity profile measure of shear stress
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
Stream Slope Calculations for Shear Stress 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
Inferring Maximum Shear Stress by Bedload Transport Stress

  • 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


Future work at lwc
Future Work at LWC Stress

  • Direct measure of riverbed conductivity

  • Analysis of additional streams under varying conditions

  • Influence of barges?


Shear stress definition
Shear Stress: Definition Stress

  • 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


Riverbed scouring
Riverbed Scouring Stress

  • 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).