Sustainable Design, Operations & Maintenance of Water Wells

Transcription

1 Sustainable Design, Operations & Maintenance of Water Wells Extending the Life of Your Well August 2-4, 2011 Presented By:

2 Seminar Overview Planning, Design & Construction Considerations Improving Water Well Management Well Operations & Maintenance Well Rehabilitation Local Case Studies

3 Planning, Design & Construction Considerations Presented by: Bob Ramsey

4 Why the Interest? Groundwater is a Major Source of Supply Most Municipalities / Districts Own & Operate Wells Many Wells are 25+ Years Old, and, Many Wells are Experiencing Problems

5 Political & Economic Drivers Current Economic Environment Changing Land Use Patterns Growing Demand for Water O&M vs. Capital Improvement Funding Time & Cost of Constructing a New Well If it Ain t Broke, Don t Fix it

6 We never know the worth of water till the well runs dry. Thomas Fuller 1732

7 Regulatory Drivers National Drinking Water Regulations Utah Water Quality Standards Division of Drinking Water Division of Water Rights (State Engineer)

8 Well Sustainability by Design Planning for the Future Extending the Life of a Well Plan Monitor Monitor Design Construct Operate Maintain Rehabilitate

9 Causes of Poor Performance Natural Formation Characteristics Poor Well Design Improper Well Construction Incomplete Well Development Groundwater Quality Conditions

10 Causes of Well Deterioration Plugging or Clogging Physical Mineral Incrustation Biological Growth Corrosion Structural Failure

11 Planning Considerations for New Wells Water Rights Flow Limitations Annual Volume Restrictions Siting Intended Use Water Quality

12 Siting Considerations State Engineer Restrictions Hydrogeologic Characteristics Land Use and Availability Proximity to Existing Infrastructure Potential Contaminant Sources Proximity to Existing Wells

13 Hydrogeologic Considerations Availability of Hydrogeologic Reports Siting Investigations Exploratory Drilling Formation Zone Testing Suitable Aquifer Characteristics Acceptable Water Quality

14 Drilling Method Considerations Commonly Used Methods Cable Tool Conventional Mud Rotary Reverse Circulation Rotary Air Drilling Systems Each Method has Advantages & Disadvantages Drilling Method Affects Design & Cost

15 Well Design Objectives Desired Yield with Least Drawdown Protection from Contamination Sand Free Production Design Life of 25 Years or More Minimize Operational Costs Ease of Operation & Maintenance

16 Well Design Considerations Local Hydrogeology Utah Administrative Rules Expected Well Yield Casing Sized for Pumping Equipment Appropriate Screen Selection Suitable Casing & Screen Materials Naturally Developed vs. Gravel Packing Well Development & Testing

17 Screen Selection Criteria Resistant to Corrosion Adequate Tensile and Collapse Strength Maximum Open Area Slot Openings Sized to Gravel Pack or Formation Materials Prevents Sand Production

18 Available Screen Types Continuous Slot Wire Wound Screen Louvered or Bridge Slot Casing Mill Slot Casing Slotted Plastic Screen

19 Available Screen Types

20 Well Development and Testing Objectives Remove Drilling Additives Repair Formation Damage Increase Flow to the Well Maximize Capacity of Well Identify Optimum Pumping Rate Establish Design Criteria for Equipping

21 Well House and Equipment Design Access to and Around Building Ample Space for Equipment & Personnel Line of Site from Rig to Well Head Heating, Cooling and Ventilation Insulation and Sound Proofing Pump Selection Monitoring Equipment

22 Rethinking Well Design Eliminate the Well Sump Upsize the Hole and Casing Diameter Use Continuous Slot Screen Install Water Level Sounding Tubes Install Chemical Feed Tubes Provide Camera Access Below Pump Design Recirculation Piping Flat Roof with Large Access Hatch

23 Improving Water Well Management Kathleen Wiseman Water Systems Engineering Consulting & Design since 1974

24 Resource managers, planners, engineers, scientists, and decision makers in various roles are being called upon to: assess water supplies assess water quality define and manage protection areas for water sources better understand resource

25 Understanding, managing, and protecting our water resources presents a major challenge population growth land use changes climate changes increasing pressure from all sectors: municipal, domestic, industrial, agricultural

26 Goal of water supply planning is to provide adequate supplies of clean water for all users at a reasonable cost

27 Sustainable use of the resource is a major component of ground water utilization Questions of sustainability are very challenging

28 Evaluate and Manage the Well System Site Investigation Regional Influences Land Use Changes Well Analysis

29 Ground water quality is determined primarily by chemical characteristics that tend to vary spatially A regional approach to local and site assessment can be a valuable tool for resource management

30 Regional Well Evaluation Assess area: geology, land uses, site factors Determine risks Proximity to contamination sources Aquifers recover slowly, difficult to restore Benefits Longer well life Improved efficiency Most important: well is resilient and able to withstand short-term events or conditions

31 Water Bearing Formations, Areas of Recharge and Discharge NASA Visible Earth: Salt Lake City Groundwater in the Western Region of the US generally comes from precipitation on the mountains or valley benches, where it infiltrates into the soil and moves to the basin-fill aquifers. USGS W.Q. in the Great Salt Lake Basins UT, ID, and WY National Water-Quality Assessment Program. Circular 1236.

32 Local and Regional Land Use Changes Affect Ground Water Resource and Recharge Areas Conditions throughout the watershed affect all domestic, municipal, and industrial users

33 Well Analysis Determine well condition Recognize common problems exist in wells Well fouling begins as soon as the well is drilled and placed into operation

34 What is fouling? Mineral blockage Biological blockage Bacterial presence Corrosion Physical blockage

35 Why does fouling occur? Changes to the well environment: Chemical Biological Physical Combination

36 How can changes due to well fouling be recognized? Production Losses Color Changes Taste and Odor Issues Corrosion

37 Most wells are affected by common mineral and biological problems Most fouling is a result of biological and mineral accumulations and occurs within zones in the well

38 Static water level Zones of the Well System Zone 1 Surface Water Influence Zone 2 Active Well Zone Zone 3 Anoxic Low Flow Area

39 Zone 1 Surface Water Influence Surface Influence - Flooding, poor integrity - Cascading water Typical of: - Shallow wells - River Alluvial wells - Rapid Recharge wells

40 Zone 2 Active Well Zone Aerobic bacteria: - Planktonic (free swimming) - Sessile (attached) Also includes: - Iron oxidizing bacteria - branched & filamentous bacteria - screen scale build-up

41 Zone 3 Anoxic Low Flow Area Characteristics: - sumps, rat traps, sand traps - lower extensions of the well and gravel pack - clay lens within formations - low producing aquifer areas Anaerobic bacteria Including: - Sulfur Reducing bacteria - Facultative Coliforms Clay lens impedes water flow

42 Well Congestion Congestion: Including ions, compounds, formation material, biomass Yield: Increased potential for re-formation Decreased potential for evacuation

43 Saturation Index Formula used to predict the potential for formation of mineral deposits. ph Water Temperature Alkalinity Calcium Level Total Dissolved Solids (TDS)

44 Corrosion is the deterioration of a material due to interaction with its environment Pump Impeller Piping Screens

45 Chemical Analysis Perform specific chemical analysis to determine: Precipitate Potential (saturation index) Solids Concentration Oxidation / Reduction Potential Alkalinity vs Acidity Ion concentrations (Fe, SO 4, Ca, Mg)

46 Sample Collection Check with Lab for sample collection requirements: How much to collect How to collect How to ship Casing and Aquifer Samples

47 Chemical Analysis Results and Ranges: Calcite or Carbonate Formation ph 7.0 Alkalinity 150 mg/l Hardness 180 mg/l Good potential for carbonate deposit Will neutralize acid and produce carbon dioxide gas Will require more acid to clean

48 Chemical Analysis Results and Ranges: Oxide Formation Iron 1.0 mg/l Manganese 0.1 mg/l Hardness 180 mg/l Presence of any aeration such as cascading water or Vadose Zone water. Presence of iron/manganese oxidizing bacteria will result in iron oxide or manganese oxide accumulation.

49 Chemical Analysis Results and Ranges: Gypsum or Sulfate Formation ph 7.0 Alkalinity 150 mg/l Hardness 100 mg/l Sulfate 100 mg/l Should not use Sulfamic or Sulfuric acid to clean well Condition will not neutralize as much acid

50 Biological Analysis

51 Significance of Well Microbiology Accounts for 80% of the blockage in wells Bacteria produce 30 to 100 times their own weight in polysaccharide polymer Impacts water quality:» Pathogens» Taste, odor, and color

52 Iron Oxide Polysaccharide Biofilm Biofilm inside a well casing at 93 feet

53 Bacterial Identification Identification of major bacterial populations in the well can: Indicate problem zones Identify source of well fouling Identify cause of well fouling Detect combinations of bacteria species that can require different treatment plans

54 Bacterial Identification

55 Leptothrix Crenothrix Gallionella

56 Sulfate Reducing Bacteria found in the anoxic, low flow areas of the well often cause taste and odor problems

57

58

59 Bio-Fouling in the Well Initiates on screens or slot openings Develops and spreads to gravel pack as the population grows and matures Blocks flow Reduces capacity Mature populations slough off accumulations into the flowing water Bacteria infest distribution lines and treatment systems

60 corrosion-mic.html Gallionella are a principal form of microbiologically influenced corrosion (MIC) As it attaches to iron bearing surfaces, Gallionella pits the metal in an effort to secure the iron necessary for energy

61 All iron bearing structures, including stainless steel, are susceptible to this form of pitting

62 Hard iron oxide scale accumulations are significant fouling mechanisms Well and pump Screened zones Associated piping Result in added pump maintenance Fouling of the intakes Iron oxide accumulations in the pump bowls

63 Monitoring wells improves efficiency Water samples to lab Measure of maintenance effectiveness Monitor fouling before significant levels occur Effective Treatment Includes Identification Treatment Monitoring

64 Biological Analysis Results and Ranges: Potable Wells Clean Well ATP < 1, ,000 HPC < 100 SRB: Negative Anaerobic < 10% Coliform: Negative Fouled Well ATP > 100,000 HPC > 300 SRB: Positive Anaerobic > 20% Coliform: Positive or Negative

65 Recognizing and Identifying Well Fouling Issues Improves Water Well Management Most fouling within well systems occurs: as a result of biological and mineral accumulations, usually involves some level of physical blockage, is a function of its operating schedule, and is frequently a result of regional characteristics

66 Beyond Basic Maintenance Well Rehabilitation Mike Schnieders Water Systems Engineering, Inc.

67

68 Well Rehabilitation Guidelines & Procedures I. Diagnosis Construction History Performance History Treatment History II. Site Investigation Pump Testing Sample Collection Video Inspection III. Develop Work Plan Placement Contact Time Agitation Flushing Disposal IV. Post Treatment Testing Sampling V. Evaluation & Follow Up Maintenance

69 Well fouling begins as soon as: The budget allows The pump is serviced The well turns 7 years old The well is placed into operation The well is drilled

70 Effective Well Treatment Recognize the problem Rehabilitate in the best manner Re-evaluate your efforts Re-visit well operation & maintenance

71 Recognizing the Problem Water Quality Capacity Re-evaluate your efforts Re-visit well operation & maintenance

72 Quality Issues: Color and Smell

73 Water Quality Changes Iron Calcium Hardness

74 Sudden or Excessive Sand Production

75 Specific Capacity

76 Record Keeping

77 Proper diagnosis allows us to target the problem and level of response

78 Rehabilitation Disinfection chlorine treatment of the well to target bacteria Cleaning combined chemical and mechanical treatment of the well targeting biofouling and/or mineral scale Re-development combined chemical and mechanical efforts targeting muds and sediment within the borehole and aquifer

79 The location of the problem may dictate the method and direction of a treatment procedure, including the chemicals used and the mechanical efforts employed.

80 Chemical Treatment Varies by type and severity of problem Simple disinfection vs. total rehabilitation Degree of fouling Varies by well size and type Well construction and well use Volumes necessary may dictate chemistry Neutralization potential of water column, deposits Varies by well integrity, site constraints

81 What can chemical cleaning remove? A variety of contaminants Primary targets are: Mineral blockage Biological blockage Physical blockage (silts and clays)

82 Chemical Cleaning Chlorine Acids Caustics Surfactants Enhancers / Dispersants Phosphates Temperature Treatments

83 Mechanical Efforts Varies by well age & integrity Varies by well size and type Original construction and modifications Varies by site constraints & chemicals used Varies by type and severity of problem Hard scale vs. heavy biofouling vs. sediments Degree of fouling

84 Mechanical Cleaning Surge block Brushes Pump-to-tank Surging High Pressure Gas Injection High Pressure Jetting Sonar Jet

85 How can mechanical efforts assist? A variety of ways: Deliver chemicals to troubled zones Agitation and activity during cleaning Chemical dispersal throughout target zone Aid in destruction of blockage within inner well

86

87

88 Combined Mechanical and Chemical Treatment More efficient solids and debris removal Biomass Heavy mineral scaling Fine sediment infiltration Increased effectiveness Break-up, dislodge stubborn deposits Reach beyond the screen and casing Increased effectiveness of debris removal Pre treatment Post treatment

89 Re-evaluate your efforts Pump Test Video Survey Water Samples Compare Results Initiate Maintenance Program

90 Re-visit Operation & Maintenance Was the well over-pumped? Did the well sit idle too long? Were maintenance needs prioritized? What role does the well play?

91 Preventative Maintenance The initial level of fouling may dictate program Proper post treatment evaluation allows for determination of maintenance needs State and local requirements? Use and operation

92 Monitoring Periodic monitoring of key parameters Evaluate analyses with performance data Useful to ID problems early More cost-effective response More effective response

93 Recognize Problem Sample Analysis Casing vs. Aquifer Chemistry and Microbiology Well Video Static vs. Dynamic ID specific problems & zones Rehabilitate Well Pull Pump, Clean, Service Store in clean area Evaluate Corrosion Damage Mechanical Pre-treatment Purge Chemical/Mechanical Efforts Purge Re-development Purge ph Balanced Chlorination Re-install pump Purge Re-evaluate Efforts Monitoring Program Active Pumping Allows for more cost effective and efficient use of chemicals Monitoring ph Critical: < 3.0 during treatment Balance time & energy Allow sufficient time and volume to effectively treat casing and gravel pack; return well to active service ASAP Follow-up with pump tests, video, sampling Brush, jet or swab, tool size should match inner diameter Balance Efforts with Chemicals and Time; Monitor ph, TDS Monitor TDS, Conductivity, Visible Turbidity Monitor Chlorine Concentration, ph, Contact Time Keep Well Active

94 Well Maintenance and Repair Taking Care of Your Aging Well Presented by: Kyle Widdison

95 Well Development

96 Single Swab

97 Dual Swab

98 Jetting Tool

99 Development Work

100 Repair Work

101 Repair Work

102 Repair Work

103 Repair Work

104 Repair Work

105 Repair Work- Damaged Screen

106 Repair Work

107 Repair Work

108 Repair Work

109 Repair Work

110 Pump Development

111 Pump Development

112 Well Abandonment

113 Presented by: Mark Chandler & Bob Ramsey Case Studies

114 Regulatory Considerations Division Of Drinking Water Division Of Water Rights Division Of Water Quality Local Sewer District

115 Regulatory Considerations Division Of Drinking Water Project Notification Includes plans and specifications Chemical use in well Chemicals must be NSF 60 certified Exception to rule may be granted New operating permit may be required

116 Regulatory Considerations Division Of Water Rights Need approval to clean, deepen or repair a well R Tools shall be cleaned Displaced materials must be removed Use only approved cleaning agents Well must be disinfected

117 Regulatory Considerations Division Of Water Quality And Local Sewer District What to do with treated water Discharge to natural channels Use DWQ best management practices De-chlorinate following disinfection Neutralize acids Discharge to sewer system Obtain permit from local sewer district De-chlorinate following disinfection ph must be above 5.0 Flow rate constraints- off peak discharge times

118 Case Studies Original Screen

119 Case Studies Problematic Screen

120 Case Studies There Is No One Size Fits All 3 Separate Case Studies Caught problem at different times Degree of success will vary Better understanding of well s health and life expectancy in all three cases Improved specific capacity in each case

121 Case Studies-Well #1 Initial Observations Well only used during summer months Diminished pumping yield Pumping water levels in screen section Red staining on pump base and floor Pump failed Video survey revealed mineralization Extensive corrosion and scaling on pump and column Water analysis indicated IRB

122 Case Studies-Well #1 Recommendation For Rehab Wire brush and bail well 2 separate rounds of chemical treatments Acid and ph balanced chlorination Pump development & testing Installation of new pump and column Disinfection Installation of permanent tremie line for treatment

123 Case Studies-Well #1 Before Treatment

124 Case Studies-Well #1 Pre-treatment Casing Aquifer Parameter Before Before ph Value Total Alkalinity* Total Dissolved Solids ORP (mv) Langlier Saturation Index Iron Total (as Fe) Bacterial Analysis Plate Count (colonies/ml) Anaerobic Growth 50% 50% Sulfate Reducing Bacteria Positive Positive Fe/Mn Oxidizing Bacteria Positive Positive ATP (cells per ml) Initial 545, M ATP (Cells per ml) 24 hour 559, M Total Coliform Positive E.coli Coliform Negative

125 Case Studies-Well #1 Before And After Treatment

126 Case Studies-Well #1 Before And After Casing Aquifer Parameter Before Today Before Today ph Value Total Alkalinity* Total Dissolved Solids ORP (mv) Langlier Saturation Index Iron Total (as Fe) Bacterial Analysis Plate Count (colonies/ml) Anaerobic Growth 50% <10% 50% <10% Sulfate Reducing Bacteria Positive Negative Positive Negative Fe/Mn Oxidizing Bacteria Positive Positive Positive Negative ATP (cells per ml) Initial 545, M 7.9 M 23,000 ATP (Cells per ml) 24 hour M Total Coliform Positive Negative E.coli Coliform Negative Negative

127 Case Studies-Well #1 Rehabilitation Results Removed congestion from casing and screens Installed smaller capacity pump Recommended 40% reduction in pumping rate Pumping water level above screens Installed permanent tremie line for routine chlorination Implemented operations and maintenance program Quarterly bacterial samples and chlorination Routine treatment has limited regrowth especially in aquifer

128 Case Studies-Well #2 Initial Observations Black water upon start up Diminished pumping yield and specific capacity Water quality changes -Increased Iron and Manganese Video survey revealed mineralization Extensive corrosion and scaling on pump and column Water analysis indicated IRB Initial video revealed damaged screens

129 Case Studies-Well #2

130 Case Studies-Well #2 Pre-Treatment

131 Case Studies-Well #2 Before And After

132 Case Studies-Well #2 Before And After

133 Case Studies-Well #2 Rehabilitation Results Removed congestion from casing and screens Increase in specific capacity and pumping Installed new lower capacity pump Installed permanent tremie line for routine chlorination Recommended use of a VFD Specific Capacity increased by 328% Specific Capacity reached 100% of original

134 Case Studies-Well #3 Initial Observations Specific Capacity had reached 36% of original Pumping Rate at 56% of original Stable water quality over 20+ years Owner tested all wells and found large bacterial population Owner chose proactive rehabilitation (did not wait until failure) Video survey revealed heavy congestion Accumulated debris in bottom portion of well

135 Case Studies-Well #3 Planned Rehabilitation Wire brush and bail inner screen and casing Remove inner screen and casing and gravel pack 2 rounds of chemical treatments Acid and ph balanced Chlorination Reinstall cleaned screens and casing and new gravel pack Pump development and testing Installation of new pump Disinfection

136 Specific Capacity (GPM/ft dd) Case Studies-Well #3 Specific Capacity- Pre-treatment Year

137 Case Studies-Well #3 Casing and Screen

138 Case Studies-Well #3 Cemented Materials Before After

139 Case Studies-Well #3 Progression of Plugging Open Partially Plugged Fully Plugged

140 Case Studies-Well #3 Pre-treatment Casing Aquifer Parameter Before Before ph Value Total Alkalinity* Total Dissolved Solids ORP (mv) Langlier Saturation Index Iron Total (as Fe) 0.05 ND Bacterial Analysis Plate Count (colonies/ml) 15 2 Anaerobic Growth 10% <10% Sulfate Reducing Bacteria Negative Negative Fe/Mn Oxidizing Bacteria Positive Negative ATP (cells per ml) Initial 4.3 M 141,000 ATP (Cells per ml) 24 hour 1.7 M 276,000 Total Coliform Negative Negative E.coli Coliform Negative Negative

141 Case Studies-Well #3 Post Treatment

142 Specific Capacity (GPM/ft dd) Case Studies-Well #3 Specific Capacity REHABILITATION Year

143 Case Studies-Well #3 Before And After Casing Aquifer Parameter Before Before After ph Value Total Dissolved Solids ORP (mv) Iron Total (as Fe) 0.05 ND 0.04 Bacterial Analysis Plate Count (colonies/ml) Anaerobic Growth 10% <10% <10% Sulfate Reducing Bacteria Negative Negative Negative Fe/Mn Oxidizing Bacteria Positive Negative Negative ATP (cells per ml) Initial 4.3M 141, ,000 ATP (Cells per ml) 24 hour 1.7M 276,000 Total Coliform Negative Negative Negative E.coli Coliform Negative Negative Negative

144 Case Studies-Well #3 Rehabilitation Results Successfully removed congestion from casing and screen Recovered specific capacity to 140% of original Installed new pump Installed permanent tremie lines Visibly opened perforations previously closed Decreased power consumption by over 25%

145 TOOLS OF THE TRADE

146 Cause for Caution

147 Typical Well Performance Problems Decreased pump and/or motor efficiency Increased energy consumption Increased motor loading Unusual noises and/or vibrations in the motor or column Tripping the automatic shut-off

148 Typical Well Performance Problems (cont.) Excessive fluctuation of the variable frequency drive (VFD) Decreased well yield and or pressure Falling pumping water levels Breaking suction in the pump Air entrainment in discharge water Color and/or odor in discharge water

149 Lessons Learned Maintain consistent well records Prepare and Implement Operations and Maintenance Plan Collect and analyze water samples at least annually Perform down-hole video whenever pump is out Watch for early warning signs Place extra emphasis on redevelopment

150 Lessons Learned (cont.) Record and monitor specific capacity and pump yield Consider rehabilitation when loss exceeds 10-15% Rehabilitate sooner rather than later Design rehab approach to site conditions Choose appropriate chemicals Carefully control chemicals, ph, chlorine

151 Well Maintenance When to Perform Maintenance TABLE 1 INSPECTION AND SAMPLING FREQUENCY Frequency Required Task Daily Weekly Monthly Semi-Annual Annual General Site Security Check for unusual noises, vibrations or leaks Record sand level readings Inspect oil levels Measure Chlorine levels Check Chemical supplies Record static and pumping water levels Record instantaneous pumping rate Record totalized pumping Sample/analyze for Coliform Bacteria Sample/analyze for Iron Related Bacteria Sample/analyze for Drinking Water Parameters