Government of India & Government of The Netherlands

DHV CONSULTANTS &DELFT HYDRAULICS withHALCROW, TAHAL, CES,ORG & JPS

GROUNDWATER MONITORING

PROCEDURES FOR OPERATIONAND

MAINTENANCE NORMS

May 2002

May - 2002 TOC

Table of Contents

Preface 1

1 Piezometer Network 2

1.1 Background 2

2 Need for Operation and Maintenance (O&M) Plan 3

2.1 Implementation of O & M Programme 4

2.2 Need for Periodical Inspection 4

3 Inspections Details 6

3.1 Approachability 6

3.2 Inspection of Logbooks 6

3.3 Inspection of Local Site Conditions 7

3.4 Inspection of Fencing 8

3.5 Inspection of Protective Cover 8

3.6 Validating Geographical Co-ordinates 9

3.7 Inspection of Observation Wells 9

3.8 Inspection of Surface Casing of Piezometers without DWLR 10

3.9 Calibrate Measuring Tapes 10

3.10 Examination of Water Level Hydrographs 12

3.11 Identification of Maintenance Tasks Based on the Inspection 13

4 Follow-up of Field Investigations 17

4.1 Down-hole Geophysical Logging 19

4.2 Pumping of Monitoring Structures 19

4.3 Carrying out Aquifer Performance Tests 21

4.4 Development of Piezometer 22

4.5 Removal of Roots 23

4.6 Hydrofracturing 23

4.7 Deepening of Piezometer 25

5 Maintenance of Digital Water Level Recorders 26

May - 2002 Page 1

Preface

The critical components making up a groundwater monitoring network are the ObservationWells, Piezometers, Digital Water Level Recorders (DWLRs), Water Quality Networks,Laboratories and the Data Centre's. Historically, the observation wells have been thesingular source for understanding groundwater dynamics. This has been furtherstrengthened by the construction of piezometers, many of which have been equipped withDWLRs. Water level data emerging from the piezometers with DWLRs have startedproviding new insights on medium and short-term cycles of groundwater fluctuations, rainfall-recharge relationships and groundwater quality changes, and also enabled refinement ofgroundwater resources computations. The optimum performance of the monitoring networkneeds to be ensured through well-defined Operation & Maintenance (O&M) practices. Thiscalls for establishment of O&M procedures supported with adequate budgets and trainedmanpower.

Generally, the maintenance of monitoring systems has often been neglected and deferreduntil the performance declined considerably or the system collapsed. This should not beallowed to happen with the infrastructure created under the Hydrology Project (HP). Hence,there is a need to formulate and implement a well- defined O&M programme.

The Consultants to the Hydrology Project have been assisting the participating agencies inthe formulation of well defined Operation and Maintenance procedures, with focus onmaintenance and upkeep of the water level monitoring network established under the HP,even long after the funding from the World Bank is over. For developing the O&M policy anumber of HIS operationalisation - regional level - workshops have been conducted,beginning August 2001, in the different states. Division/District/ Sub-division officers alongwith the field staff involved with water level/water quality data collection have participated inthe workshops. The participants deliberated on the different themes that should be part ofpreventive maintenance as well as problem specific issues, and made recommendations.The manpower, budgetary requirements and operational procedures were also discussed,which has been reflected in the recommendations.

This manual explains the basics of maintenance and how it is to be done. It is an outcomeof the discussions in the numerous workshops. It systematically outlines the O&Mprocedures focusing on the upkeep of the piezometers and presenting them in a number oflogical steps. Simple procedures preventing the declining performance of piezometers arediscussed. The manual does not advocate a single strategy but recommends a series ofprocedures. O&M procedures should be guided by local hydrogeological settings, waterquality conditions, the design of the structure, the distribution of the network and the socio-economic settings around the monitoring locations.

It is expected that the guidelines will help in assessing the O & M procedures, budgetaryrequirements and staff that would be required for maintenance of the monitoring network.Detailed maintenance of DWLRs and the Data Centres is not discussed in the manual asthese will be company-specific, normally to be taken care of by the vendors through anAMC.

Active involvement of the Hydrology Data Users Group (HDUG) and the local communityhas to be envisaged in the O&M programme. Feedback from the HDUGs and frequentinteraction with the local community in the neighbourhood of the network stations, especiallyfarmers, youth and school children, and sharing the information generated from the networkwith the community, would help in devising new approaches in participatory O&Mprogrammes.

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1 Piezometer Network

1.1 Background

Historically, groundwater levels have been monitored using privately owned open dug wellstapping the upper unconfined aquifers. These levels reveal the piezometric head/water tableelevation of the semi-confined/unconfined aquifers. However, the necessary well-aquiferhydraulic connection has not always been well established. The frequency of monitoring hasgenerally been restricted to a few times in a year corresponding to water levels during pre-monsoon, monsoon, post-monsoon and winter seasons. These water levels have been usedto construct water table hydrographs representing the troughs and peaks of the water table.In reality, many times these data have been too sparse to construct reliable and crediblewater level hydrographs.

The Hydrology Project has enabled construction of a large number of scientifically designedpiezometers tapping unconfined and deeper aquifers. A piezometer is a purpose-builtobservation well that facilitates measurement of the piezometric head of the selected aquifer.Since the area covered under the project (Central & South India) is largely made up ofconsolidated formations, the bulk of the piezometers constructed in these formations hasbeen designed as bore-wells and a limited number in unconsolidated formations as tubewells.

In order to be effective, these piezometers should always have the necessary hydraulicconnection with the targeted aquifers and should be suitably isolated fromoverlying/underlying aquifers. Only then the water levels monitored in these piezometers willcontinue to provide a reliable water level elevation, representative of the regional piezometricelevation in its vicinity. Digital Water Level Recorders (DWLRs) are installed in a number ofpiezometers. Optimally functioning DWLRs can only give undistorted piezometric head at thedesired frequency.

High frequency water level monitoring using the DWLR has enabled the generation ofcontinuous hydrographs providing data on annual cycles. It also picks up many cycles ofshorter duration like seasonal, barometric, daily, and tidal cycles. This monitoring has helpedin generating a better understanding of the groundwater system, and of the recharge rainfall-response in different hydrogeological situations. It has also helped in refining the estimationof groundwater resources. Piezometers have become a reliable source for sampling thegroundwater from the tapped aquifer for water quality monitoring.

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2 Need for Operation and Maintenance (O&M) Plan

The integrated groundwater monitoring networks comprise the newly constructedpiezometers and the observation wells of both the state and central agencies. In order toensure generation of reliable data from the networks, the piezometers and the observationwells have to be systematically maintained. Under-performing observation wells andpiezometers would generate erroneous data, that could result in wrong interpretations. Thiswould in the long run result in formulating wrong policies and legislations.

Declining performance of piezometers and observation wells is natural with the passage oftime. The declining performance needs to be anticipated and preventive maintenance needsto be carried out. The causative factors for declining performances will be largely guided bythe local conditions and these have to be well understood, so as to formulate suitablemaintenance strategies.

Open dug wells are referred to as the most efficient groundwater structures and, hence, in anormal situation, they should be the ideal structure for monitoring the water levels. In thecase of observation wells the reliability of the data would decrease considerably when:

• the observation well goes into disuse and is used for dumping waste• declining water levels result in drying up of the well for part of, or throughout the year• there is siltation in the well• the well collapses• there are damages to the platform leading to seepage of surface water and domestic

waste• the monitoring structure is submerged for part of, or throughout the year• there is a number of production wells near the open well overlapping the area of

influence

Piezometers are simple structures and would require very little for a regular upkeep, alsosince there are no pumping equipments. Periodically it may require cleaning and/orrehabilitation, removing unwanted materials and improving the flow of the surroundingaquifer to the piezometer. Poor performance can be expected due to:

• clogging of the fractures or deposition on the bore-hole walls• poor or under-development of the piezometer at the time of construction• general decline in regional water levels leading to seasonal or complete drying up of

piezometers• siltation leading to blocking significant portions of the water bearing zones/screens• collapse of the piezometer• incrustation of the screen• growth of roots from the sides of the bore-hole• heavy influence of other production wells near the piezometers overlapping the area of

influence• seepage of surface water due to failure of sanitary seals• vandalism• dropping of DWLR into the piezometer• submergence of the piezometer for part of, or throughout the year

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The O&M procedures should identify the monitoring structures that encounter one or more ofthe problems listed above. Data emerging from such suspect structures should be identifiedat the initial stages itself and these structures should be repaired. In cases where thedeterioration is beyond repair, the monitoring structures should be abandoned and suitablereplacements planned. The O&M strategy should be preventive in nature rather thancurative. It has to be recognised that deterioration of monitoring structures is natural withtime, hence there is a need to invest in maintenance. Only this can ensure generation ofdata of reliable quality. In case of piezometers, the aim should to be maintain them in theiroriginal drilled/cased depth, ensuring a good hydraulic connection with the groundwaterreservoir being monitored. The O&M plan has to be formulated by all the agencies with aclear definition of the procedures, standard maintenance practices, prescribed technicaloptions for different generic problems with clear recognition of responsibilities at the differentlevels, the budgetary requirements, reporting and evaluation procedures.

2.1 Implementation of O & M Programme

An ideal O&M policy should ensure that a series of procedures are in place for monitoringthe health of all the monitoring structures.

Maintenance of the observation wells would continue to be a tricky issue, as most of themare privately owned. However, it has to be ensured that non-representative observation wellsdo not continue to generate data. (It was reported in the workshops that a number ofobservation wells are fully/seasonally abandoned open wells, which sometimes turn intogarbage dumps and need immediate replacement). These need to be replaced by reliableopen wells or dedicated piezometers. Review of the performance of all the observation wellsappears very relevant and all the agencies are advised to carry out a detailed examination ofall the observation wells and confirm that the data emanating from them are reliable.

Declining performance of a certain number of piezometers constructed under the HydrologyProject has also been reported. The problems that result in the poor performance need to beunderstood, the solutions for reviving them identified and repairs carried out so as to bringthem back to optimally performing levels.

2.2 Need for Periodical Inspection

The health of the monitoring network (for water level and water quality monitoring) needs tobe periodically evaluated by competent authorities in the different districts/divisions/regions,so as to reassure that the data generated are reliable and that the monitoring practices arein agreement with the prescribed methodology.

The officers responsible for data collection have the singular responsibility of picking up thefirst indicator that reflects a less than optimal performance of the structure. Keenobservations followed by systematic scrutiny of the data during every observation are thekey to picking up declining performances. The officers responsible for data collection have toallocate adequate time at all observation sites for evaluating the structures and the data. Ithas to be always kept in mind that data emerging from a poorly performing monitoringstructure can lead to wrong interpretations. Any structure whose performance is consideredsuspect by the field-data collector has to be reported to the concerned officer recommendingfollow-up investigations.

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As a procedure, detailed inspection has to be carried out annually or whenever earlier asrequested by the field officer responsible for data collection.

The inspection should be carried out by the In-charge accompanied by the officersresponsible for data collection. These inspections need to be carried out preferably twomonths prior to the onset of the monsoon, so that remedial actions can be taken up beforethe monsoon. As part of the inspection the supervisor should witness field measurements ofwater levels, water quality sampling and DWLR data transfer. The civil structures have to beexamined, the instruments inspected and the neighbourhood of the monitoring structuresobserved. Brief chats with the people in the neighbourhood should prove beneficial inunderstanding issues that are not seen or otherwise visualised during the inspection. Theinspection should ensure that the monitoring structure:

• is providing reliable data• identifies the potential threats that could affect the generation of reliable data• identifies solutions for ensuring continuous generation of data• makes plans for ensuring the implementation of periodic maintenance procedures• verifies the skills of the field officer in-charge of data collection• inspects the data collection formats and log books and cross-checks them in the field• makes an estimate of the maintenance budget• checks the performance and the discipline of the observation staff and staff motivation• identifies any observation procedure errors• calibrates the measuring tape

The integration of the individual networks of the State and Central Agencies has to beensured through regular meetings between the agencies, for an exchange of notes aftereach inspection. A joint inspection is also useful at times, but is not always a necessity.

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3 Inspections Details

The inspection should verify whether the construction of the piezometer has been matchingthe specifications and whether all the relevant information regarding the piezometerconstruction and the local conditions is recorded accurately. Further, it should look at theapproachability of the monitoring site, the time taken for reaching the site, theneighbourhood of the site, the status of the fence and of the protection cover and thenexamine the monitoring structure itself. The inspection team should also address issuesrelated to facilities provided to the monitoring team, including timely availability of transport,fuel allocation, the status of monitoring instruments, the availability of spares and otherrelevant issues.

3.1 Approachability

The water level monitoring network established under the Hydrology Project has a large areacoverage. The network represents the different hydrogeological units and aquifer systems. Itis likely that a limited number of these monitoring structures are not easily approachable (orprobably not at all) throughout the year. It has to be ensured that the normal routes taken forreaching the monitoring structures are inspected and bottlenecks, if any, clearly identified,and that alternative routes, if any, have also been identified and inspected. During theinspection of the roads not only the mobility of jeeps but also of heavy trucks, that wouldcarry the water quality sampling pumps/compressor/pumping test units/drilling rig/hydrofracturing units, has to be kept in mind. In terrain where approachability is difficultduring certain seasons, the feasibility of using local observers (with the required technicalskills) to monitor the data for preventing discontinuity in data generation has to be examined.The advisability of installing DWLRs for monitoring water levels in such piezometers also hasto be examined.

A route map should be prepared for all observation sites giving the approach road from thenearest town/highway or prominent feature. The map should give the distances, types ofroads, major bottlenecks and alternative routes, if any. The details of permanentidentification marks and the names of local contact persons with their address should alsobe part of the map. The maps with the details of the location should be part of the Logbook.

3.2 Inspection of Logbooks

It is expected that for every monitoring site a log-book, also referred to as the well register, ismaintained giving location details in the form of a map and text. These details would includegeographical co-ordinates, height of Measuring Point (MP), structure design, constructiondetails, original depth, lithology, aquifer depth, discharge, and water quality details.Information on the monitoring details including initiation date, monitoring frequency, details ofDWLR and cable length should be part of the logbook as well.

The logbook should be carried to the site every time a water level monitoring or water qualitysampling is carried out. The inspection team should examine data collection formats, and logbooks and cross check them in the field, essentially for assessing the performance of thefield officer responsible for data collection, and assessing the training requirements and theperformance of the field instruments.

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The purpose of the logbook is to keep a clear record of checks and details of maintenanceundertaken when the site is visited. This includes routine monitoring and inspection bysupervising officers. The logbook is an extremely important link in the data quality auditchain. The design of the logbook will depend upon the type of the monitoring well, design,type of instruments installed and the frequency of monitoring.

3.3 Inspection of Local Site Conditions

The observation wells forming part of the water level and water quality monitoring networkare largely private or community owned open dug wells. In the case of piezometers theseare all located on the premises of government institutions such as schools, colleges, localgovernment offices, electric sub-stations, health centres, inspection bungalows, policestations, village centres or other government lands. It has been noticed that in many caseslocal agencies or interested volunteers have been of assistance in protecting thepiezometers from vandalism as well as helped maintain the surroundings by cutting thegrasses/weeds/branches etc. In some situations, the local institutions have not been of muchassistance in giving protection or maintenance. The reason for the indifference can be due tolack of awareness on the utility of the water level monitoring structures and its relevance intheir life. This situation needs to be altered and awareness should be created regarding thebenefits of reliable data.

Figure 3.1:Carry out regular inspection of allpiezometers and observation wellsby a team headed by the Data CentreIn-charge, to ensure that data generatedare reliable

The annual inspection team have to sensitise the local people regarding the utility of thepiezometers and the need for proper maintenance. It would always be useful if the design ofthe structure and the instruments used are explained along with sample sets of differentdata. This would generate interest in the local authorities and communities to help, if not inmaintenance, at least in preventing vandalism.

The neighbourhood of the piezometer, both inside and outside the fence, has to beexamined. Water logging conditions, sewage dumps, pumping wells etc have to be identifiedand their influence on the data generated examined. The corruption of the data, if any,because of the influences in the neighbourhood should be examined and remedial actionssuggested. This would refer to, for instance, the growth of weeds and grass inside theenclosure and the branches of trees outside hindering movement and maintenance work.Provisions have to be made for cutting weeds and grass once every quarter and to prune thebranches every year.

The cost of cleaning the neighbourhood of the piezometer should be worked out and theperson who can execute the job locally should be identified.

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3.4 Inspection of Fencing

In some states, piezometers with DWLR have been enclosed with barbed wire fencing. Thestatus of the fence and the angle irons posts anchoring them need to be inspected. Duringthe inspection, it has to be ensured that the prevailing fencing is not only good currently butwill also not deteriorate before the next inspection.

Figure 3.2:Check barbed wire fence, angleirons, gate and locks

The portion where the barbed wire is loose has to be identified. The maintenancerequirement for different tasks, including giving tension to barbed wire or replacementwherever required, and painting or replacement of angle iron posts have to be identified.Barbed wire fencing would likely need to be replaced more frequently in coastal areas/areaswith polluted air as compared to other areas Similarly, the angle iron posts, which are rusted,damaged and need replacement should be identified.

3.5 Inspection of Protective Cover

The piezometers equipped with a DWLR have a protective cover. In many statespiezometers without a DWLR do not have any protective cover. The design of the protectivecover varies from agency to agency. It is mounted on a brick masonry/concrete (some timespre-fabricated) platform anchored through bolts and nuts.

Figure 3.3:Identify the components of the protective cover,including the box, hinges, thermocol insulation,bolts, nuts and locks that need maintenance orreplacement

During the inspection it has to be ensured that the protective cover is in good condition, thetop cover is not rusted, and the locked doors fully protect the instruments placed inside. Ithas also to be ensured that rainwater does not stagnate on the top of the cover or seepsthrough the base of the platform. The hinges should be in good condition. The Thermocolinsulation inside the box should be inspected and replacements suggested wherever

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required. The nuts and bolts that anchor the protection box with the platform need to be oiledand greased regularly. The bolts will have to be opened whenever maintenance works haveto be carried out on the piezometer. Provision has to be made for painting the protectivecover and the board every two years in coastal areas/ areas with heavy air pollution and inother areas every 3 years. The masonry platform also has to be inspected for anydevelopment of cracks. The maintenance budget should include provisions for repair of theplatform every time the protective cover is removed.

3.6 Validating Geographical Co-ordinates

The geographical co-ordinates corresponding to the location of the piezometer need to bevalidated by the Data Centre Manager. The validations should be carried out with the help ofthe toposheet (1:50,000 scale) brought to the site. Using the brunton compass, locate thepiezometer site accurately on the toposheet.

Figure 3.4:Verify the accuracy of the geographicalco-ordinates assigned for the piezometerusing brunton compass and toposheet

The Lat. - Long. values should be read from the toposheet and the values verified. Validatedgeographical co-ordinates should only be used for generating different types of maps andcross sections.

3.7 Inspection of Observation Wells

The observation wells, which have been the main source of data on water levels and waterquality for the last three decades, need to be inspected. Declining water levels, drilling ofbore-wells/ tube wells as reliable drinking water source and the easy availability of powerhave resulted in discontinued maintenance of the observation wells. In the absence ofalternative sources, these observation wells continued to be used as monitoring wells by thegroundwater agencies.

Figure 3.5:Spend time at observation well site,ensure that data generated are useful,reliable and representative

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Inspection of the network should focus on the relevance of some of the observation wells.The inspection should clearly indicate that the observation well continues to represent theregional groundwater system that is being monitored and continues to generate reliabledata. It has also to be ascertained that the groundwater does not get contaminated with thesurface run off, sewage/ domestic waste and can continue to be used for water qualitymonitoring. The well platform (in the case of domestic wells) and the stone/cement coveringthat prevents collapsible material from falling into the well also have to be examined.

3.8 Inspection of Surface Casing of Piezometers without DWLR

The piezometers that have not been fitted with a DWLR in many cases do not have aprotective box. The top-casing pipe of the piezometer has in many cases a protective-casingpipe of galvanised iron along with a cap. The protective cover is usually painted. It isexposed to the vagaries of the weather and vandalism. The status of the protective coverhas to be inspected.

Figure 3.6:Inspect Piezometers without a DWLR.Check protective casing, cap and masonaryplatform, and identify maintenancerequirements

The necessity of painting and repairs if any has to be recorded. It has to be closelyexamined whether the cap is able to cover the piezometer properly. The inspection teamshould recommend on the frequency of painting required. In case the surface casing pipe isof PVC and is not protected with a GI casing pipe, it has to be ensured that the PVC pipedoes not provide scope for vandalism. The necessity of proper fencing of the piezometersites has to be examined. The status of the platform also has to be examined.

3.9 Calibrate Measuring Tapes

The first indicator of the health of the piezometer/observation well is the water level. Manualmeasurements of the depth to water levels should be carried out during the inspection. Themanual water level measurements should be recorded and compared with the DWLR waterlevels wherever available or with the previous readings in the piezometers without a DWLR.The inspection team should discuss with the officer in-charge of regular monitoring the typeof method to be used for manual water level measurement and calibration of the tape.Manual measurements, are considered very simple and basic, and usually taken for granted.The errors that creep in are ignored or arbitrarily corrected. The different methods used forwater level monitoring are discussed on the following pages:

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The most popular method for measuring the water levels is to use a metallic tape. A stoneor bob is tied at the lower end. The tape is lowered into the piezometer. When the sound ofthe bob hitting the water level is heard the corresponding measurement is noted andrecorded as water level Below Measuring Point (BMP). Where the water levels are deeperthan the tape length additional pieces of some known length are tied to it. The measurementof water levels with a metallic tape should not be considered reliable as it has in-builtdeficiencies which change from person to person and tape to tape. So it should be replacedby other standard techniques.

Measurement of water levels using electrical dip tapes is another practised method. The diptape is battery operated and touching the water the indicator gives a beep sound/glowinglight or both. Run down batteries, poor contacts and cuts in the tape may give erroneousvalues.

This method is more reliable but it has to be ensured that the graduations marked on thetape are correct. It is recommended to purchase electrical tapes from companies with provenaccuracy and reliability. The graduations need to be validated using more than one tape.

Another popular method is the wetted tape (hold & cut) method. In this method a graduatedsteel tape is used for measuring the depth to water levels. A weight is attached to the lowerend of the tape. The lower part of the tape is coated with chalk. The steel tape is lowereduntil part of chalked portion of the tape is below water. The reading from the MP is noted.The tape is then pulled up and the wetted chalk portion read. This reading is then subtractedfrom the measurement at the MP, which is the actual water level depth. This is a veryreliable method for water level measurement.

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Manual measurement of water levels has to be taken up only by using a reliable tape. In thepiezometers fixed with a DWLR this has to be carried out once every month before down-loading the data. Cross verification of the measurement of water levels more than once andadopting more than one method should be made a standard practise, every time water levelmeasurements are carried out.

3.10 Examination of Water Level Hydrographs

The field officers responsible for water level monitoring should be concerned about morethan just measuring water levels. They should be aware of the details of the aquifer systembeing monitored and the formations penetrated.

The inspection team should reassure itself of the optimum performance of the piezometersin the course of the inspection. Examination of the water level hydrographs of the concernedpiezometer along with the well section and design at the site itself should be part of theinspection. The response of the water levels to recharge and discharge effects in the form ofannual and seasonal cycles has to be verified and, wherever required, compared withneighbouring wells which tap the same aquifer. Less than desired responses to differentsituations have to be taken up as cases for detailed field investigations.

Figure 3.7: Examine the response of water levels to recharge and draft.Have a good understanding of the aquifer being monitoredand the piezometer design. Identify piezometers showing lessthan optium response for further investigations

In such situations, it is likely, that the water level in the piezometer is not fluctuatingsimultaneously with the piezometric head of the tapped layer, due to lack of response or timelag. The piezometer could then be failing to provide the true information of the aquifer beingmonitored. Water level data emerging from such piezometers cannot be considered asreliable. Such piezometers should be subjected to detailed investigations for identifying thenature of the problem in the piezometer.

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3.11 Identification of Maintenance Tasks Based on the Inspection

Based on the findings from the inspection, the team should be able to recognise the physicalstatus of the piezometer, as well as what is happening down the hole in the piezometer.When it becomes difficult to recognise the sub-surface behaviour based on the availableevidence, additional tests may have to be conducted to find out whether the piezometer isoperating efficiently or maintenance has be carried out. The inspection team should be ableto build a mental picture on the situation down-hole by:

• measuring the depth of the piezometer• measuring the water levels• recording the obstructions met with while measuring the depth of the piezometer• examining mirror observations reflecting light down the piezometer• examining water level hydrographs

The field inspection team, basing itself on these checks, should be able to infer whether themonitoring structure can generate accurate data. The results of the check should be used topick up indicators of deterioration likely to set in. Then the inspection team should be able togive expert advice on the different standard maintenance and preventive maintenance tasksto be carried out. In the case of non-representative monitoring structures, decisions have tobe taken on the remedial actions or alternative options recommended. The inspection teamhas the professional responsibility of ensuring continued efficiency of the different structuresthat are part of the network.

The inspection team should report the observations in the prescribed inspection report. Asample format of the inspection report is given in Table 1, which may be customisedaccording to requirement. The inspection report on individual observation wells andpiezometers should be sent to the concerned Data Processing Centre In-charge forinformation and necessary follow-up action.

The inspection findings should form the guidelines for additional field tests to be carried outand maintenance activities initiated. Maintenance work should be carried out at theappropriate, to ensure systematic generation of authentic groundwater data.

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Table 1: Annual Operation and Maintenance Inspection Report

Date:………………………………………………………………… District: ……….…………………………………………….………

Agency: ……………………………………………………………………………………………………...…………………….…………….

Mandal/Block: …………………………………………….……… Village: ………………………………………………………….…..

Longitude: ………………………………………………………… Latitude: ………………………………………………….………..

R.L.: ……………………………………………………….……….. M.P.: …………………………………………………………………

Well No.: ………………………………………………..…………. Well Type: ………………………………………………………….

Total Depth: ………………………………………………………. Aquifer tapped: ……………………………………………………

DWLR Details, Make…………………………………….……… S. No.: ……………………………………………………………….

Capacity Range: ………………………………….………………………………………………………………………….…………….…..

Installation details: …………………………………………………………………………………………………………………………….

Inspection team members: ………………………………………………………………………………………………………………….

Parameter Query ResponseRecommended

Action

Approachable throughout theyear/seasonal

Areas of poor approachability

Periods of poor approachability

Alternative routes, if any

Period for which data generation will beeffected??

Scope for identifying a local observer

Approachability

Solution for ensuring continuous datageneration

Status of the neighbourhood of thepiezometer

Does anything in the neighbourhoodaffect data generation

Details of influencing conditions

Distance of the influencing zone fromthe piezometer site

Will the data generated be influencedseasonally or throughout the year

Has the influencing zone come up afterthe establishment of the piezometer

Is there a possibility of data corruption

Neighbourhoodof observation site

Does the data need any correction

Status of theName Board

Does the name board need any repair.Does any detail mentioned on theboard need correction or addition

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Is the well currently used

Is the water reported to be potable

Is the well reported to go dry

Is there any physical damage to thewellDoes the monitoring well representa regional aquifer system

Status ofObservation Well

Does the well platform protect itfrom entry of surface seepage

Is the fencing completely protectingthe piezometer from vandalismDoes the fencing need any main-tenanceWhat length of fencing needstighteningWhat length of fencing needsreplacementDoes the angle post need anymaintenanceWhen was the angle post paintedlast time

Status of theBarbed Wirefencing aroundthe piezometer

How many angle posts needreplacementIs there grass and weeds aroundthe piezometerStatus of the area

besides thepiezometer

Are there any branches of treescovering the piezometer whichneed to be removed

Is the protective cover anchoredwith the cement plat-form

Does the protective cover showany rusting

Does the protective cover needpainting

Are the doors of the protectivecover completely protecting theinstruments inside

Does the protective cover needrepairs or replacement

Status of theprotective coverof the piezometer

Do the locks need replacement

Has the masonry platformdeveloped major cracks

Does the masonry platform allowseepage of surface water

Status of themasonry platformaround thepiezometer

Does the masonry platform needrepairs or replacement

Is the casing pipe protected andis the cover attachedStatus of casing

pipe exposed tooutside Does the casing pipe require

painting or other maintenance

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Frequency of manual water levelmeasurementsWater Level

measurementsFrequency of DWLR measurement

Does the water level hydrographclearly bring out annual/seasonal/diurnal cyclesIs there a reason to believe that thewater level hydrograph is notresponding optimallyDoes the depth of the piezometershow any reduction

Depth of thepiezometer Does the diameter of the piezo-

meter show any reduction

Observations of the team:

Recommended follow up work if any

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4 Follow-up of Field Investigations

The field investigation report should clearly mention the number of observation wells thatneed replacement or repair. The number of piezometers that need additional investigationshave to be identified. The report should also suggest the type of follow-up studies to betaken up.

Field Observation Inference Follow up Technical Task Remarks

Geophysical bore-hole logging

Diameter

Caving zone

Corrodedcasing/screen

Depth of the piezo-meter shows reduction

Siltation due tocaving from weakerzones or break inthe casing/screens

Flushing - Development Restore theoriginal depth

Cleaning through pumpingClogging offractures/screens Development

Remove clogging

Siltation Flushing - Development Restore theoriginal depth

Steep decline inwater levels

Piezometer deepening orreplacement

Water columnsbeyond measuringrange of DWLR

Replace DWLR or change thetransducer depth

Optimalmeasuring range

Non-responsive waterlevels

Reduced Hydraulicconnection with theaquifer

Hydro-fracture Improvedhydraulicconnection

Growth of otherobstructions

For growth of roots in the bore-wells, design appropriate toolsto clean the piezometer wallsof the roots

Difficulty in lowering themeasuring tape

Other obstructions Flushing

Restore theoriginalpiezometerdesign

May - 2002 Page 18

Operation and Maintenance Estimates

Well No. …………………………… Village…………………………………

ItemNo.

Item Qty. Rate(in Rs.)

Unit Amount(in Rs.)

1 Cutting of branches Job/year

2 Repair approach (wherever required) Job/year

3Clearance of grass, weeds and branches(every six months)

Job/year

4 Giving tension to barbed wire fencing Job/year

5 Replacing barbed wire fencing Job/year

6Replacing broken angle posts Lump Sum(LS)

Job/year

7 Providing ‘U’ nails and barbed wire etc. (LS) 6 Kgs.

8 Painting the protective cover (every 2 years) Job/year

9Replacing the protective cover (whereverrequired)

Job

10Repairing the masonry platform (whereverrequired)

Job

11 Replacement of pad-locks (every year) Unit

12Painting the outer casing pipe (whereverrequired)

Job/year

13Strengthening the casing pipe (whereverrequired)

Unit

14 Sounding the piezometer (every year) Job/year

15Geophysical down hole logging (whereverrequired)

Job

16Development through pumping (every threeyears)

Job

17 Pumping tests (every 5 years) Job

18Cleaning of piezometer using cutting tool(wherever required)

Job

19Cleaning the piezometer using compressor(every 5 years)

Job

20 Hydro-fracturing (wherever required) Job

21Deepening the piezometer (whereverrequired)

Unit

Total Estimate towards Operation &Maintenance

Systematicplanning for O&Mwill call forpreparing the O&Mbudget withadequate allocationof funds for thedifferentcomponents.Listing of thedifferent activitiesunder O&M andrepairing anestimate is a pre-requisite

May - 2002 Page 19

4.1 Down-hole Geophysical Logging

Down-hole geophysical logging should be carried out on piezometers that are suspected ofsiltation, deviations, incrustations and bacterial growth that need confirmation. Logging couldalso be used to examine the well design and check for breakage in the casing pipes orscreens. The borehole logging tools can be chosen from the following:

Type of Logging Information Obtained

Calliper Diameter of the borehole, permeable zones and type of clay, casing features, casingleaks, screen position and build up, if any

Spontaneous Potential Lithology, permeable zone, formation water quality

Resistivity Lithology, permeable zone, layer resistivity, thickness, formation water quality

Natural gamma Lithology, clay zone, water production zone, layer thickness

Temperature Permeable zone, casing leaks, fluid flow and water level

Conductivity Casing leaks, permeable zones, formation water quality and water level

Interpret the logging results carefully for detecting changes in the piezometer diameter,zones that probably show caving, build up in the piezometer due to siltation, position of thescreens, break in casing or screen joints or leakage in casing joints.

The results of the logging should be the basis for deciding the follow-up activities forrevitalising poorly performing piezometers.

4.2 Pumping of Monitoring Structures

The simplest method of sustaining the performance of observation wells/piezometers isthrough pumping. In this method, the monitoring structure should be pumped at a dischargerate in excess of the potential discharge. During the pumping the effort should be to over-

May - 2002 Page 20

pump the monitoring structure. Pumping would remove the storage water/ replace stagnantwater as well as help in limited removal of fines in the case of piezometers.

In privately owned dug wells used for domestic purpose it might not always be possible tocarry out the pumping. However, this should not be a problem with the agricultural wellsused for monitoring.

In the case of piezometers pumping may not always help in fully cleaning of the piezometer.This has to be followed up by other steps such as using compressors/ drilling rig, jetting andin limited cases even hydrofracturing. Piezometers throwing up a big amount of finematerials during pumping run the risk of getting spoiled because of sand locking in thepump.

Cleaning of piezometers through pumping using submersible pumps needs to be carried outas a regular maintenance procedure. The frequency of pumping will vary from piezometer topiezometer depending upon its performance. Regular checking of the specific capacity willindicate the need for cleaning through pumping. Declining of the specific capacity should beconsidered as an indication for carrying out the pumping. Every piezometer has to bepumped once every three years as part of development. In many cases the piezometers willcome up for pumping as part of water quality sampling. However, this should not beconsidered as a cleaning technique as the water quality-sampling pump is of low discharge.Cleaning through pumping should be considered as an independent process.

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The procedure to be adopted is to pump the piezometer using a suitable submersible pump.The pump capacity, discharge and depth of lowering should be guided by the yields obtainedduring drilling/development of the piezometer. Preferably, the pump should be placed abovethe screen in the case of unconsolidated rocks or against the deepest water-yielding zone inthe case of consolidated rocks. The procedure should involve pumping of the piezometer inmultiple spells. Water levels and discharge have to be monitored during the tests. Initially,the piezometer should be pumped till the water level drops close to the suction limits. Theinitial water is likely to be muddy with some fines. After the pumping is stopped thepiezometer should be allowed to recover. In many situations it is likely that the pumpingdischarge and water level will start rising compared to initial levels due to the process ofdevelopment. This should be followed by another spell of pumping and recovery. Theprocess of pumping and recovery should be continued until the pumped water is clear withno fines, and till the water level rise is stabilised.

4.3 Carrying out Aquifer Performance Tests

After cleaning and development through pumping it would be advisable to carry outsystematic aquifer performance test for estimating the aquifer parameters. The change in thecharacteristics of the groundwater reservoir and the aquifer parameters over time, need tobe understood. This would be beneficial in improving the computation of groundwaterresources.

Step-draw-down test and constant discharge tests can be carried out on the piezometer.

4.3.1 Step-draw-down Test

The step-draw-down test should be performed on piezometers constructed in the un-consolidated formations, primarily to understand the efficiency of the piezometer. An efficientpiezometer with minimum well loss would reflect a good hydraulic connection between theaquifer and the piezometer, thereby indicating that the piezometer is reflecting the regionalaquifer system very well.

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In the step-draw-down test the piezometer should be pumped in increasing levels (steps) ofpumping discharge. For each step water levels have to be monitored systematically until thewater level reaches a steady (or near-steady) state. Every step has to be sustained for aperiod of 60 -100 minutes or until the drawdown in the well ceases to increase any further.The analysis of the discharge in comparison to the draw-down data will permit estimation ofaquifer and well loss. This is the base on which a good hydraulic connection of thepiezometer with the regional aquifer can be inferred.

4.3.2 Constant Discharge Test

A pumping test with a constant discharge needs to be carried out for estimating the aquiferparameters of the tapped aquifer. The test involves pumping the piezometer at a constantdischarge rate. The water level changes need to be monitored systematically in thepiezometer as well as in any well in the neighbourhood tapping the same aquifer. Ananalysis of time-distance-draw-down data provides estimates of the aquifer parameters.

The pumping tests are not an essential method in the process of development. However,they help in understanding the aquifer system being monitored as well as in recording anychanges in aquifer characteristics over time.

4.4 Development of Piezometer

Declining performance of the piezometers will be the result of accumulation of fines in thefractures, mineral scale, slime bacteria, silt or sand build-up, changes in the aquifer or thegeological area around the piezometer. With the right equipment and techniques, these caneasily be removed from the piezometer. Other problems, such as large physicalobstructions, extensive damage to the well screen, or changes in the aquifer due to naturalevents may not be so easily resolved.

Piezometer development should be undertaken for removing unwanted materials andimproving the flow of the surrounding aquifer to the piezometer. Development shouldphysically remove silt, clay, fine sand, scale, and befouling and correct any deficienciesduring construction. This can be accomplished through jetting, surging and/or airlifting.Development will clear unwanted materials from the piezometer and its surroundings, andserve to integrate the piezometer into its environment. No matter how carefully a piezometerhas been designed and constructed, over a period of time development is essential toensure its efficiency and water quality.

Development to be carried out on piezometers drilled in consolidated and unconsolidatedformations must be different. In the latter case, development of the piezometer would requiremovement of a drilling rig to the piezometer site. This needs some preparatory workincluding site preparation, removal of fence, clearing of bushes and branches of trees,removal of DWLR and protective works. The drilling rig has to be positioned carefully toprevent damage to casing and well assembly. Details of the piezometer including type andcombination of casing used, the total depth of casing and depth of water bearing zones shouldbe made available to the development unit.

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In tube well designs jetting is the most effective way to clean the well screen and rehabilitatethe surrounding aquifer. Jetting involves shooting jets of water through the screen and intothe formation while simultaneously pumping the dislodged materials out of the well. Thewater column should be agitated effectively after the jetting through spells of airlifting.Chemical solutions can also be used for clearing the drilling mud clays, bentonite mud,encrustations, bacterial growth etc. Fresh water mixed with sodium tripolyphosphate shouldbe circulated through the screen. The well should be allowed to set until the polyphosphatecan effectively work on the mud cake/ clay masses and desegregate them. Simply pouredinto a piezometer, the chemicals will not be effective; they need to be followed by physicalcleaning. Chemicals that are hazardous and also change the quality of the water shouldnever be used. Before using chemicals, a water quality analysis has to be carried out andany major changes in water quality subsequent to chemical treatment should be clearlyrecorded. Such piezometers should not be used for drawing major inferences ongroundwater quality characteristics.

4.5 Removal of Roots

Special cutting tools have to be fabricated for cleaning the piezometers where growth ofroots is seen. While designing the cutting tool, piezometer details such as its diameter, thelithology of the formation and the nature of the water bearing formation have to be kept inmind. The drilling rig should be properly positioned keeping in mind the deviations in thepiezometer. The cutting tool has to be lowered below the surface casing after which thewalls are cleaned with a rotary movement. The cleaning should be stopped 1 metre from thesounded depth. The cutting tool should be pulled out and replaced by the button bit, andcleaned to the bottom. Airlifts should also be carried out with a compressor. Occasionallythe cutting and air-lifting should be stopped and the piezometer allowed to recuperate beforerepeating the process. Airlifting has to be carried out for longer periods against the waterbearing zones.

4.6 Hydrofracturing

Hydrofracturing should be considered as a technical option only for reviving piezometersthat show clogging of fractures or those piezometers that show limited hydraulic connectionwith the aquifer that is being monitored. Hydrofracturing can be carried out in consolidatedrocks especially in those piezometers where complete development cannot be achieved.Based on the logging data the aquifer should be isolated using packers and hydrofracturingshould be carried out. Geophysical down-hole logging is a pre-requisite before hydro-fracturing, for isolating the aquifer being monitored. In hydro-fracturing pressurised water is

May - 2002 Page 24

injected to clear the fines from the fractures. Care has to be taken to see that new fissuresare not created in the process of hydrofracturing. The process involves injection of water intothe fracture zone and the fines are washed out. Specialised infrastructure is required forcarrying out hydrofracturing and is available with the agencies involved with groundwaterdevelopment for rural water supply. Care has to be taken to see that the water injectedmatches with the quality of water in the piezometer.

The steps involved in hydrofracturing are:

• Study the lithological log of the piezometer.• Identify the aquifer position. Carry out geophysical down-hole logging and decide on the

aquifer where water is to be injected.• Lower a dummy tool to check the verticality and diameter of the piezometer to ensure

that the piezometer has not collapsed• Carry out a discharge test using a submersible pump for finding the pre-fracture yield

test• Fill the piezometer with potable water so as to remove the air from the piezometer and

isolate the fracture zone using the packer. The packer should be inflated with thehydraulic pump.

• Inject water into the fracture using a high-pressure water pump. The injected water willstart working into the fracture. Continue the propagation for 5-10 minutes. Repeat theinjection for shorter spells.

• Carry out post fracturing yield tests. Repeat the logging for comparing the pre- and post-fracturing changes in the formation.

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4.7 Deepening of Piezometer

Deepening of the piezometers in consolidated formations can be taken up in select caseswhere the piezometers show partial penetration, seasonal drying up or large declining waterlevels. The deepening should be undertaken after ensuring that the tapped aquifer isextending deeper. Geophysical resistivity surveys should be carried out prior to deepening.Before deepening, the deviation of the piezometers has to be examined. Piezometers withlarge deviations should not be considered for deepening. The diameter of the bit usedshould be considerably less than the smallest diameter of the piezometer. Deepening ofpiezometers will be risky if the targeted aquifer is not clearly demarcated. During deepening,there is a potential danger for the piezometer to collapse.

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5 Maintenance of Digital Water Level Recorders

Maintenance of DWLRs installed on the piezometers will be a major issue coming up in thenext few years. DWLRs are under warrantee for the first year and subsequently are coveredunder an AMC. Poor functioning/failure of DWLRs in the different agencies is notuncommon. The different makes and different models have their own specific problems.Combined with operating errors of the field staff, the performance of DWLRs has been lessthan satisfactory.

The O&M programme for the DWLR has to be systematically planned. Efforts should be onto identify poorly performing DWLRs and bring these to the notice of the vendor for suitableaction. Since the DWLRs are under AMC, contractual obligations would require that only thevendor is allowed to attend to any repairs. Experience shows that since vendors are not veryprompt in attending to the problems it would be beneficial if the field staff have the requisitetraining in identifying potential problems and forewarn the vendor of potential problems. Theoptimum performance of the DWLR should be verified in the field by validating the waterlevel recorded by the instrument with manual measurements. It has to be ensured that acalibrated tape is used for manual measurements.

The major problems in DWLRs functioning have been related to depletion of batteries,sensors not responding to commands, water ingress, excessive power consumption, poorcontact of the communication cable between data logger and the Data Retrieval System(palmtop computer/hand held terminal), limitations of the software and its user interface. Aspart of the O&M strategy, the agencies will have to ensure adequate training by the vendorto the field staff. Regular contacts have to be established with the vendors so as to ensurethat different problems reported from different locations are attended to immediately. It hasto be ensured that the vendor has an adequate inventory of essential spares. Regular reviewmeetings have to be carried out with the vendor and also the manufacturer for evaluating theperformance of DWLRs, identifying critical areas requiring attention and for anticipatingpotential problems.