20150225 AWWA Groundwater Workshop_RJK

Groundwater WorkshopWell Site Selection, Design,

Construction, and Testing

Russell Kyle, MS, PG, CHG

Wood Rodgers, Inc.

American Water Works Association

California-Nevada Section

Groundwater Workshop, 2015

Rancho Cucamonga, California

February 25, 2015

Overview

• Well Site Selection

• Common Well Types

• Well Drilling Methods

• Well Design

• Well Construction

• Well Development

• Aquifer Testing

• Post Construction

Overview




• Well Design



• Aquifer Testing


Well Site Selection

• Define Preliminary Project Objectives

– Capacity requirements

– Specific areas that need water

– Distribution system limitations

– Water quality requirements

– Property availability

Considerations for Site Selection

• Ability to Produce Water with Acceptable Yield and Quality

• Availability of Property

• Proximity to Infrastructure (Distribution, Storage, Treatment)

• Consideration of Impacts to Nearby Wells (i.e. interference)

• Consideration of Impacts to Environment (e.g. vegetation, fish, wildlife)

• Potential Future Impacts from Upgradient Contaminant Source

• Basin Yield and Water Rights Issues

• Impacts to Contaminant Cleanup Activities (i.e., plume migration)

• Potential Water Quality Impacts from Vertical Migration of Undesirable Water

• Construction Feasibility

• Cost

Types of Siting Studies

• Regional Assessment (Basin-wide)– Allows for advance planning– Can select new well locations from available sites based on

suitability– Often used when developing a new well field– Also used when replacing wells that have been impacted by

regional contamination plumes

• Assessment of a Pre-Selected Site– Site often chosen without regard to suitability– Need to confirm compliance with offset requirements– Check site suitability for construction and maintenance – Consider ability to meet project objectives (may be difficult,

expensive, or impossible)

Understand the Hydrogeology!

Sources of Information

• Previous Investigations, Reports

• Water Data Library

• Existing Wells (Driller’s Logs, etc.)• Well location

• Lithology

• Well construction details

• Static water level

• Well capacity

• Pumping water level

• Test Borings / Test Wells

• Other Agencies in the Area

• Well Drillers

Records are confidential and require a signed release!

• Water quality data for regulated public systems

• Statewide database available for download

• Typically only includes data submitted for regulatory compliance (purveyors will often have more extensive datasets)

• Does not include any information on well construction or location

California Division of Drinking Water (formerly CDPH)



Potentially Contaminating ActivitiesState Water Resources Control Board

Geotracker Online Database

Production Potential

• Driller’s Logs

• Pump Efficiency Tests (i.e., Pump Check or Edison Tests)

Well No.

Screened Interval

Total Well Depth

Static Water Level

Pumping Rate

(New)

Specific Capacity

(New)

PumpingRate

(Current)

Specific Capacity(Current)

[ft bgs] [ft bgs] [ft bgs] [gpm] [gpm/ft] [gpm] [gpm/ft]

3 100-550 560 150 2,000 56 1,350 32

7 250-650 670 143 1,200 35 960 22

12300-400;450-600; 655-805

825 138 2,500 68 1,760 44

Well Interference

Site Assessments

• Assessing a well site that has already been selected to make sure it is suitable for well construction

• Identify any “fatal flaws” before expending significant time and resources

• Should be completed prior to acquiring land if possible

• Information is needed to ensure site meets owner needs, to obtain initial buy-off from DDW, and to prepare Drinking Water Source Assessment and Protection Program

Site Assessments

• If a regional assessment was not completed initially, perform a hydrogeologic review– Aquifer depths– Water quality– Well yields– Basin conditions– Contamination

• Gather data from nearby wells (water, monitoring, and oil/gas)

• Learn as much as possible from existing wells and studies before drilling at the site

Site Assessments

• Utilize aerial photos and topographic maps to make initial an evaluation of well site suitability

• Field reconnaissance– Site Access (for construction and ongoing maintenance)– Available work are (for construction and ongoing maintenance)– Underground and overhead utilities– DDW offset requirements– 50 ft Control Zone requirement– Noise restrictions/concerns– Environmental concerns– Water supply location and quality– Location to dispose of drilling spoils, fluids, and development/testing water– Pump to waste capability (storm drain or sewer?)– Proximity to other wells in the area– Safety concerns

Well Siting – Offsets

Construction Logistics

Construction Logistics

Overview




• Well Design



• Aquifer Testing


Naturally Developed Well with Casing

Perforated in Place

Cable-Tool Type

Construction

Source: Roscoe Moss Company

Gravel Envelope Wellwith Gravel to Surface

Common Design


Gravel Envelope Wellwith Gravel Feed Tube

Common Design


Gravel Envelope Wellwith Inter-Aquifer Seals

Overly Complex

(Not Recommended)


Telescoping Well

• Reduced Cost

• Limits Lowering of

Pumps in Response to

Water Level Decline

• Can be Problematic

During Well

Rehabilitation


Overview




• Well Design



• Aquifer Testing


Drilling Methods for Production Wells

• Auger Drilling

• Air Rotary Drilling

• Casing Advancement Methods

– Casing Hammer Rotary Drilling

– Cable Tool Drilling

– Dual Rotary Drilling

• Direct Rotary Drilling

• Reverse Circulation Rotary Drilling

Two-Pass Well Drilling Method

• Conductor casing and sanitary seal

• Pilot borehole drilling

• Isolated aquifer zone testing

• Design

• Borehole reaming (enlargement)

• Well construction

• Development

• Testing

Direct Circulation Rotary Drilling

Direct Circulation

Rotary Drilling


Rotary Table


Advantages:

• For small diameter boreholes, penetration is very fast in alluvial formations

• Drilling fluid density can control flowing artesian conditions and formation gas

• Drilling fluid programs can be designed to help control sloughing clays and heaving sands in an open borehole

• Ideal for borehole resistivity logging• Most versatile form of drilling• Has been used to depths over 40,000 feet

Direct Rotary - 7.7 Miles Deep

Photo Credit: Gregory Ivannikov


Disadvantages:

• Requires potable water for drilling fluid makeup• Requires mud mixing equipment and drilling fluid

circulation system• Large diameter boreholes require high viscosity drilling

fluids to remove the formation cuttings• Drilling fluid additives may cause aquifer damage• Drilling fluid can be expensive to dispose of in urban

settings• Higher downhole fluid velocities can lead to borehole

washouts

Reverse Circulation Rotary Drilling

Reverse-Circulation

Rotary Drilling

Tri-cone Bit (Pilot Bit)

Tri-Cone Bit with Reamer

Weight Indicators


Large Compressor Required(Can be Noisy)


Circulation Tanks and Shaker


Sampling Box

Formation Samples


Advantages:

• Most cost efficient drilling method in alluvial formations for large diameter water wells

• Allows for larger borehole diameters• Hole penetration is very fast in alluvial formations• Lower downhole fluid velocities• Often requires less drilling fluid additives • Short time duration for well drilling, construction,

and well development • Provides clean and representative formation samples• Suitable for borehole resistivity logging • Provides good access for gravel pack installation


Disadvantages:

• Requires 24-hour per day operations• Requires a large site (100’ x 300’ or greater preferred)• Requires large drilling fluid circulation system• Requires a significant amount of potable water• Drilling fluid additives are required to stabilize water

sensitive formations• Drilling fluid can cause formation damage if not

monitored

Drilling Fluids Program

Objectives

• Keep the borehole open during drilling operations and well construction

• Effectively remove cuttings from the borehole

• Stabilize water-sensitive or loose formations

• Prevent damage to the aquifers to be completed

• Drilling fluid should be easily removable during well development

Drilling Methods Summary

• Direct Circulation Rotary Drilling – Most versatile method, good for small diameter wells, very deep wells, and test holes with elogs

• Reverse Circulation Rotary Drilling – Most common method for large diameter high capacity wells in alluvial formations, very short drilling and construction time, provides good access for gravel pack installation to provide sand-free water production at high capacities with proper gravel gradation selection and well screen design

Overview




• Well Design



• Aquifer Testing


Design Objectives

• Desired Water Quality

• Total Capacity Needed

• Desired Well Efficiency

• Operational Plans

• Desired Well Service Life

• Sand Production Requirements

• Budget

• Schedule

Well Design Requirements and Standards

• Local Agency Well Standards

• California Department of Water Resources (DWR) Bulletin 74-90 Well Standards

• California Department of Drinking Water (DDW) Requirements

• AWWA Standard for Water Wells A 100

Good References for Well Design

Well Design Components

• Conductor casing (if needed): depth, material, annular seal material

• Aquifer selection to meet well capacity and water quality objectives

• Gravel envelope to meet sand control objectives

• Well screen slot size to retain the proper amount of gravel envelope

• Seal locations to prevent contamination migration

• Well casing/pump chamber diameter, material, and wall thickness to meet the project objectives

• Well screen diameter, material, and type to meet the project objectives

• Borehole diameter to allow for gravel and seal thickness requirements and to accommodate accessory pipes

• Accessory pipes, types, and locations

Aquifer Criteria

• Acceptable water quality (from zone testing)

• Sufficient yield

• Separation from contamination

• Confining zones above to seal against

Aquifer Selection

Gravel Envelope Criteria

Sand Production• Artificial filter pack must be engineered to provide the

appropriate grade to complement the aquifer formations

Well Efficiency• Gravel that is not well-cleaned, too small, or improperly

engineered may reduce well efficiency

Well Service Life• Lower-efficiency wells have shorter life spans

• Angular gravel is more likely to foul and harder to clean during rehabilitation, reducing the service life of a well

Gravel Envelope Design

• Sieve formation samples from the target aquifers – design around finest material to control sand

• Incorrectly designed filter pack gradation may:

– Allow unacceptable sand production

– Result in low well efficiency

• Consider products that have a proven track record in the area for the target aquifer

U.S. Standard Sieves

Fine Formation Sample

Coarse Formation Sample

Sieve Analysis – Terzaghi CriteriaMigration Factor

D15 (filter) / d85 (finest formation) < 4Permeability Factor

D15 (filter) / d15 (coarsest formation) > 4

Source: Roscoe Moss Company, 1990

AcceptableScreen Slot Size~15% passing

Uniformity Coefficientof Filter Pack (D60/D10)

~2.0 - 2.5

Pack Aquifer Ratio(D50/d50)~4 - 20

Examples of Gravel Envelope

Oglebay Norton8x16

Well Screen Design

• Select slot size to complement the filter pack gradation and allow the desired percent passing of the filter pack.

– ~10-25 percent passing

• NEVER design the slot size around the formation material!!!

Louvered Well Screen

Wire Wrapped Well Screen

Steel Selection

• Select a material and well screen type suited to the depth, water quality, application, and desired well service life

– Purpose of the Well

• Potable, Irrigation, Desalination, Dewatering, Industrial

– Required Service Life

– Local Setting/Environment (Water Quality)

– Cost

Steel Types

• Historical (Cable Tool)– Hard Red (pre-1942) and Kai-

Well (post-1945)

• Common– Mild– Copper-Bearing– High Strength Low Alloy (HSLA)– 304L SS– 316L SS

• Exotic– Super Duplex SS 2507

Hybrid Wells

• Dissimilar Metals Connector

• Dielectric Coupler


Well Casing/Pump Chamber

• Provide a diameter large enough for the largest anticipated pumping equipment

• Additional casing diameter is often beneficial– Larger pump than anticipated

– Well modification – liners

– More forgiving

• Select an appropriate material and wall thickness to prevent casing collapse

• Select material types and thicknesses that meet the well service life objective

• Address potential for corrosion when joining dissimilar metals


• Drilling fluids and cement seals can exert inward pressure on the casing during construction

• Water outside the casing can exert inward pressure during pumping

ASTM A 139 Grade B Steel w/ 0.2% Cu


Other well casing design considerations:

• Calculate the collapse pressure for each casing type to confirm the materials can withstand pressures exerted during well construction and pumping operations of the completed well

• Adding sounding and camera ports will significantly weaken the casing

• Pumping cement seals applies additional pressure to the casing

Accessory Pipes

• Provide adequate internal diameter for the intended use

• Select materials and wall thickness to meet the well service life objective

• Provide adequate borehole diameter to ensure seals can be placed around the pipes (2-inch annulus)

• Injection, camera, and sounding ports should have smooth entrances to the well casing

• Inlet depths should be designed for planned uses

• Weld all accessory pipe joints

Example Accessory Pipes

Gravel Feed Pipe

SoundingPort

Conductor Casing

• Often fulfills “sanitary” seal requirements with DDW

• Stabilizes surface materials to allow circulation of fluids during drilling

• May aid in sealing very permeable unsaturated (dry) formations that could cause lost circulation

• Typically mild steel casing, normally sealed with cement grout that is pumped under pressure

• The production borehole is drilled through the conductor casing, so it must be plumb

• Large enough to allow for largest anticipated reamed borehole diameter

Annular Seals

“Sanitary” Seals• Regulatory term for a surface seal with specified minimum

requirements

• Minimum requirements may not meet project objectives

Surface Seals• Seal off upper aquifers

• Provide a barrier against the downward migration of contamination

Intermediate Seals• Isolate aquifers

Sand/Cement Grout

• Excellent for surface or “sanitary” seals

• Mix for seals is subject to regulation by DDW

• Typically a 10.3-to 10.5-sack

Well Design Summary

• The additional material costs for an extended well life are relatively small portion of the cost of a new well and pump station

• Viable new well sites are going to continue to become harder to locate and more expensive to purchase

• Not every well can be designed with a 100-year service life; however, advanced design considerations can extend the life of a well in most settings

Overview




• Well Design



• Aquifer Testing


Well Construction• Surface Casing/Conductor Casing

• Mobilization

• Pilot Borehole Drilling

• Geophysical Logging

• Isolated Aquifer Zone Testing

• Design

• Borehole Reaming

• Well Construction– Well Casing, Well Screen and Accessory Pipes

– Gravel Envelope and Intermediate Seals

– Annular Seals


• Well Testing

• Well Performance/Acceptance Tests

Conductor Installation

• Collect formation samples

• Borehole diameter – bit size

• Borehole depth (minimum 50 ft for sanitary seal)

• Casing diameter and wall thickness

• Casing material type

• Cement mix, quality, and age

• Cement volume versus volume of annular space

Conductor InstallationBucket Auger Typically Used for

Large Diameter Conductor Boreholes

Mobilization

• Document and inventory equipment– Drill Rig Type and Model

– Support Equipment (i.e., backhoe, water truck, pipe trailers, air compressor, etc. )

• Complete list of personnel

• Review Contractor Safety Plan– Contractor maintains responsibility

• Inventory tubular goods (drill and tremie pipe)– Size, length, and type of thread or connections

• Other materials– Drilling water source, drilling fluid additives, sound walls

Mobilization

Tremie Pipe

Pilot Borehole Drilling

• Borehole diameter – bit size and caliper surveys

• Borehole deviation – deviation surveys

• Weight on the bit – weight indicator

• Drilling fluid properties – measurement frequency, compliance with drilling fluid program and specifications

• Abnormal drilling conditions

• Formation samples

Formation Sample Collection

• Collected minimum of every 10 ft or at change in formation

• Classified using Unified Soil Classification System (USCS)

• Stored in Plastic Bags and Transported for Analysis

Soil Classification

• Sample Depth Interval

• Drilling Rate / Penetration Rate (ft/hour)

• Drill Chatter, Shaking, etc.

• Color (wet)

• Particle Sizes and Distribution

• Sorting

• Angularity of Sands and Gravels

• Plasticity of Silts and Clays

• Mineral Composition

• Mineral Cementation

• Miscellaneous

Drilling Fluid Properties

• Viscosity• Weight• Sand Content• Water Loss• pH

Geophysical Borehole Logging• Provides Formation

– Depths– Thickness– Properties– Water level

• Used to select intervals for zone testing and well screen intervals– 16-in. and 64-in. normal

resistivity– Guard log– Spontaneous potential– Gamma– Sonic porosity

Isolated Aquifer Zone Testing

• Select 3 to 5 zones for testing

• Constructed within the open pilot borehole, starting with the deepest

– 20 ft screen with annular gravel pack

– Sealed above and below (important)

– Development

– Pumping for 3-6 hours once clean

– Sampling for groundwater water quality

Casing and Accessory Pipes

• Inventory all materials on site• Confirm Compliance with Specifications

– Mill Certificates and Delivery Orders– Measure Diameter and Lengths– Wall Thickness

• Check for Roundness• Inspect Machined Ends• Identify flaws or damage that warrants repair or

replacement• Check storage conditions – NOT ON GROUND• Confirm Installation Order

Casing – Properly Stored

Casing – Flawed

Casing “Peep” Hole

Machined End

Casing Collar

Peep Hole

Casing

Accessory Pipes

Sounding Port (Welded Connection)

Sounding Port (Inside Casing)

Casing Installation

Casing Tally

Gravel Envelope

• Obtain current factory sample/sieve to confirm compliance with specifications

• Sieve selected gravel samples upon delivery to confirm compliance with specifications

• Confirm volume/weight delivered

• Inspect for foreign material

• Installation method and procedures

• Disinfection during installation

• Consolidate prior to annular seal placement

• Verify that the calculated volume of gravel envelope was installed prior to annular seal placement

Gravel Envelope

Gravel Envelope Installation

Cement Grout Pump

Overview




• Well Design



• Aquifer Testing


Well Development

• Remove drilling fluid additives

• Grade filter pack and near-well zone (coarsest at well screen)

• Maximize specific capacity and well efficiency

• Stabilize sand production

Well Development Program

• Drill Rig Well Development– Open ended airlifting

– Double swab/airlifting

– Chemical treatment (if necessary)

• Pump Development– Pumping and surging

– Aquifer pumping tests

Well Development Tools

Double-Swab Tool(Swabs Typically

Spaced 10 ft Apart)


Swab/Airlift Development

Test Pump Development

Rossum Sand Tester

Measures Entrained

Sand within the Well

Discharge

Well Development


Overview




• Well Design



• Aquifer Testing


Aquifer Testing

• Step Drawdown Pumping Test– 6 – 10 hours duration with increasing flow rates at each step– Typically 3 – 4 steps

• Constant Rate Pumping Test– Typically 12 – 24 hours duration– Constant pumping rate– Collect Title 22 water quality samples– Conduct flowmeter survey

• Purpose– Verify acceptable sand production– Short- and long-term pumping dynamics– Well efficiency– Appropriate pump intake setting

Well Testing Short Constant Rate Tests

11/29/2007

125

130

135

140

145

150

155

160

165

170

175

1 10 100 1000 10000

Elapsed Time (Minutes)

Dep

th t

o W

ate

r (F

eet)

Short Constant Rate 1350 GPM Short Constant Rate 1800 GPM Short Constant Rate 2700 GPM

24 hr

Short Constant

Rate Tests

1350 GPM

SWL=116.8 ft.

Q/ΔS =59 GPM/FT

1800 GPM

SWL=118.42 ft.

Q/ΔS =58 GPM/FT

2700 GPM

SWL=118.02 ft.

1367 GPM

1778 GPM

2750 GPM

Flow Rate Adjusted

Possible Causes of Sand Production

• Construction Defect

– Void in the gravel envelope

• Poor Well Development Program

– Incomplete development

– Overly aggressive development

• Design

– Improper gravel envelope design

– Lack of gravel reserve

• Well Structure Failure

– Casing hole or enlarged perforations

Overview




• Well Design



• Aquifer Testing


Post Construction

• Well plumbness and alignment

– Cage survey for plumbness

– “Dummy” survey for alignment

– Gyroscopic survey

• Downhole video survey

• Well disinfectionSource: Roscoe Moss Company

Gyroscopic Survey

Alignment Dummy

Well Disinfection

• Dropping the pH of the water prior to disinfection makes the chlorine more effective

• Place chlorine evenly throughout the well by spotting with tremie pipe

• Use only newly purchased, liquid sodium hypochlorite

– Granular products and calcium hypochlorite can lead to trapping of solids within the gravel pack

Downhole Video Survey

• Run water at least 24-hours prior to inspection

• Inspect with downward view on the way down

• Check for water movement

• Use a focusing side scan view on the way out of the well

• Inspect casing joints and problem areas including scale, encrustation, holes and enlarged perforations

• Compare depths with as-built records

Downhole View

Side Scan View

Video SurveyReport

Well Performance Requirements

• Conditions for acceptance of completed well (should be specified in construction contract)

– Sand Content

– Turbidity

– Well Efficiency

– Plumbness & Alignment

– Video Survey Review

Questions?

Russell Kyle, MS, PG, CHG

Associate Hydrogeologist

Wood Rodgers, Inc.

[email protected]

(626) 379-7569

mailto:[email protected]

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20150225 AWWA Groundwater Workshop_RJK

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