download-manuals-ground water-manual-gw-volume4fieldmanualgeo-hydrologypartviii

Government of India & Government of The Netherlands

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

VOLUME 4GEO-HYDROLOGY

FIELD MANUAL - PART VIII

MONITORING WELLSINSPECTION AND MAINTENANCE

Field Manual – Geo-hydrology (GW) Volume 4 – Part VIII

Geo-hydrology March 2003 Page i

Table of Contents

GENERAL 1

1 NEED FOR OPERATION AND MAINTENANCE (O&M) PLAN 2

1.1 GENERAL 21.2 IMPLEMENTATION OF O & M PROGRAMME 31.3 NEED FOR PERIODICAL INSPECTION 3

2 INSPECTIONS DETAILS 4

2.1 APPROACHABILITY 42.2 INSPECTION OF LOGBOOKS 42.3 INSPECTION OF LOCAL SITE CONDITIONS 52.4 INSPECTION OF FENCING 62.5 INSPECTION OF PROTECTIVE COVER 62.6 VALIDATING GEOGRAPHICAL CO-ORDINATES 72.7 INSPECTION OF OBSERVATION WELLS 72.8 INSPECTION OF SURFACE CASING OF PIEZOMETERS WITHOUT DWLR 82.9 CALIBRATION OF MEASURING TAPES 82.10 EXAMINATION OF WATER LEVEL HYDROGRAPHS 92.11 IDENTIFICATION OF MAINTENANCE TASKS BASED ON THE INSPECTION 10

3 FOLLOW-UP OF FIELD INVESTIGATIONS 13

3.1 GENERAL 133.2 DOWN-HOLE GEOPHYSICAL LOGGING 143.3 PUMPING OF MONITORING STRUCTURES 153.4 CARRYING OUT AQUIFER PERFORMANCE TESTS 17

3.4.1 STEP-DRAW-DOWN TEST 173.4.2 CONSTANT DISCHARGE TEST 17

3.5 DEVELOPMENT OF PIEZOMETER 183.6 REMOVAL OF ROOTS 183.7 HYDROFRACTURING 193.8 DEEPENING OF PIEZOMETERS 20

4 MAINTENANCE OF DIGITAL WATER LEVEL RECORDERS 20

4.1 REQUIREMENTS FOR DWLR PERFORMANCE-MONITORING 214.2 EXECUTION OF PERFORMANCE MONITORING 22

4.2.1 ADMINISTRATION AND LOGGING 234.2.2 ORGANISATION AND PREPARATION 234.2.3 PERFORMANCE CHECKS 234.2.4 VERIFICATION 244.2.5 MAINTENANCE PROCEDURE 25


Geo-hydrology March 2003 Page 1

GENERAL

The Field Manual on Geo-Hydrology comprises the procedures to be carried out to ensure properexecution of design of the groundwater water level monitoring network, operation and maintenance ofobservation well and piezometers. The operational procedures are tuned to the task descriptionsprepared for each Hydrological Information System (HIS) function. The task description for each HIS-function is presented in Volume 1 of the Field Manual.

It is essential, that the procedures, described in the Manual, are closely followed to create uniformityin the field operations, which is the first step to arrive at comparable hydrological data of high quality.It is stressed that water level network must not be seen in isolation; in the HIS integration of networksand of activities is a must.

• Volume 4 of the Field Manual deals with the steps to be taken for network design andoptimisation as well as for its operation and maintenance. It covers the following aspects.

• Part I deals with the steps to be taken for network design and optimisation. Furthermore, siteselection procedures are included, tuned to the suitability of a site for specific measurementprocedures.

• Part II details with piezometer construction procedure with details of the different elements andthe significance of different elements in the piezometer construction

• Part III comprises the preparatory activities and procedures for carrying out aquifer tests. Theprocedures to be adopted for analysis of pumping test data is briefly discussed

• Part IV comprises the testing and installation of DWLR’s. Procedures to be followed forprocurements and installation are outlined in Volume 4 of the reference manual.

• Part V deals with the need for carrying out Reduced Level Surveys and the procedures incarrying out the survey are outlined.

• Part VI deals with the standardised procedures to be adopted for manual collection of water leveldata from open wells and piezometers.

• Part VII deals with the standardised procedures to be adopted for retrieval of data from DWLRand integration with the software.

• Part VIII, deals with procedures to be adopted for regular inspection and maintenance ofpiezometers and DWLR’s.

The procedures as listed out in this manual are in concurrence with the ISO standards as far asavailable for the various techniques and applicable to the conditions in Peninsular India.



1 NEED FOR OPERATION AND MAINTENANCE (O&M) PLAN

1.1 GENERAL

The integrated groundwater monitoring networks comprise the newly constructed piezometers and theobservation wells of both the state and central agencies. In order to ensure generation of reliable datafrom the networks, the piezometers and the observation wells have to be systematically maintained.Under-performing observation wells and piezometers would generate erroneous data, that could resultin wrong interpretations. This would in the long run result in formulating wrong policies and legislations.

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

Open dug wells are referred to as the most efficient groundwater structures and, hence, in a normalsituation, if the dug well is not being used for pumping, it should be the ideal structure for monitoringthe water levels. In the case of observation wells the reliability of the data would decreaseconsiderably when:

• the well is used for drinking water supply, irrigation or other purposes,

• 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, and

• there is a number of production wells near the open well, overlapping the area of influence.

Piezometers are simple structures and require very little for a regular upkeep, also since there is nopumping equipment installed. Periodically, cleaning and/or rehabilitation may be required, removingunwanted materials to improve the flow of the surrounding aquifer to the piezometer. Poorperformance can be expected due to:

• clogging of the aquifer fractures or the borehole screen openings by deposition due to chemicalor physical processes,

• 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, and• submergence of the piezometer for part of, or throughout the year.

The O&M procedures should identify the monitoring structures that encounter one or more of theproblems listed above. Data emerging from such suspect structures should be identified at the initialstages itself and these structures should be repaired. In cases where the deterioration is beyond



repair, the monitoring structure should be abandoned and a suitable replacement should be planned.The O&M strategy should be preventive in nature rather than curative. It has to be recognised thatdeterioration of monitoring structures is natural with time, hence there is a need to invest inmaintenance. Only this can ensure generation of data of reliable quality. In case of piezometers, theaim should to be maintain them in their original drilled/cased depth, ensuring a good hydraulicconnection with the groundwater reservoir being monitored. The O&M plan has to be formulated by allthe agencies with a clear definition of the procedures, standard maintenance practices, prescribedtechnical options for different generic problems with clear recognition of responsibilities at the differentlevels, the budgetary requirements, reporting and evaluation procedures.

1.2 IMPLEMENTATION OF O & M PROGRAMME

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

Maintenance of the observation wells would continue to be a tricky issue, as most of them areprivately owned. However, it has to be ensured that non-representative observation wells do notcontinue to generate data. These need to be replaced by reliable open wells or dedicatedpiezometers. Review of the performance of all the observation wells appears very relevant and all theagencies are advised to carry out a detailed examination of all the observation wells and confirm thatthe data emanating from them are reliable. The problems that result in the poor performance ofpiezometers need to be understood, the solutions for reviving them identified and repairs carried outso as to bring them back to optimally performing levels.

1.3 NEED FOR PERIODICAL INSPECTION

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

The officers responsible for data collection have the singular responsibility of picking up the firstindicator that reflects a less than optimal performance of the structure. Keen observations followed bysystematic scrutiny of the data during every observation are the key to picking up decliningperformances. The officers responsible for data collection have to allocate adequate time at allobservation sites for evaluating the structures and the data. It has to be always kept in mind that dataemerging from a poorly performing monitoring structure can lead to wrong interpretations. Anystructure whose performance is considered suspect by the field-data collector has to be reported tothe concerned officer recommending follow-up investigations.

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

The inspection should be carried out by the In-charge accompanied by the officers responsible fordata collection. These inspections need to be carried out preferably two months prior to the onset ofthe monsoon, so that remedial actions can be taken up before the monsoon. As part of the inspectionthe supervisor should witness field measurements of water levels, water quality sampling and DWLRdata transfer. The civil structures have to be examined, the instruments inspected and theneighbourhood of the monitoring structures observed. Brief chats with the people in theneighbourhood should prove beneficial in understanding issues that are not seen or otherwisevisualised during the inspection. The inspection should identify and verify:

• that the monitoring structure is providing reliable data,

• the potential threats that could affect the generation of reliable data,

• the solutions for ensuring continuous generation of data,



• the plans for ensuring the implementation of periodic maintenance procedures,

• the skills of the field officer in-charge of data collection,

• the usefulness of data collection formats and log books and cross-checks them in the field,

• the preparation of an estimate of the maintenance budget,

• the performance and the discipline of the observation staff and staff motivation,

• any observation procedure errors, and

• the calibration of the measuring tape.

The integration of the individual networks of the State and Central Agencies has to be ensuredthrough regular meetings between the agencies, for an exchange of notes after each inspection. Ajoint inspection is also useful at times, but is not always a necessity.

2 INSPECTIONS DETAILS

The inspection should verify whether the construction of the piezometer has been matching thespecifications and whether all the relevant information regarding the piezometer construction and thelocal conditions is recorded accurately. Further, it should look at the approachability of the monitoringsite, the time taken for reaching the site, the neighbourhood of the site, the status of the fence and ofthe protection cover and then examine the monitoring structure itself. The inspection team should alsoaddress issues related to facilities provided to the monitoring team, including timely availability oftransport, fuel allocation, the status of monitoring instruments, the availability of spares and otherrelevant issues.

2.1 APPROACHABILITY

The water level monitoring network of Penninsular India has a large area coverage. The networkrepresents the different hydro-geological units and aquifer systems. It is likely that a limited number ofthese monitoring structures are not easily approachable (or probably not at all) throughout the year. Ithas to be ensured that the normal routes taken for reaching the monitoring structures are inspectedand bottlenecks, if any, clearly identified, and that alternative routes, if any, have also been identifiedand inspected. During the inspection of the roads not only the mobility of jeeps but also of heavytrucks, that would carry the water quality sampling pumps/compressor/pumping test units/drilling rig/hydrofracturing units, has to be kept in mind. In terrain where approachability is difficult during certainseasons, the feasibility of using local observers (with the required technical skills) to monitor the datafor preventing discontinuity in data generation has to be examined. The usefulness of installingDWLRs for monitoring water levels in such piezometers also has to be examined.

A route map should be prepared for all observation sites giving the approach road from the nearesttown/highway or prominent feature. The map should give the distances, types of roads, majorbottlenecks and alternative routes, if any. The details of permanent identification marks and thenames of local contact persons with their address should also be part of the map. The maps with thedetails of the location should be part of the Logbook.

2.2 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, construction details,original depth, lithology, aquifer depth, discharge, and water quality details. Information on themonitoring details including initiation date, monitoring frequency, details of DWLR and cable lengthshould be part of the logbook as well.



The logbook should be carried to the site every time a water level monitoring or water quality samplingis carried out. The inspection team should examine data collection formats, and log books and crosscheck them in the field, essentially for assessing the performance of the field officer responsible fordata collection, and assessing the training requirements and the performance of the field instruments.

The purpose of the logbook is to keep a clear record of checks and details of maintenance undertakenwhen the site is visited. This includes routine monitoring and inspection by supervising officers. Thelogbook is an extremely important link in the data quality audit chain. The design of the logbook willdepend upon the type of the monitoring well, design, type of instruments installed and the frequencyof monitoring.

2.3 INSPECTION OF LOCAL SITE CONDITIONS

The observation wells forming part of the water level and water quality monitoring network are largelyprivate or community owned open dug wells. In the case of piezometers these are all located on thepremises of government institutions such as schools, colleges, local government offices, electric sub-stations, health centres, inspection bungalows, police stations, village centres or other governmentlands. It has been noticed that in many cases local agencies or interested volunteers have been ofassistance in protecting the piezometers from vandalism as well as helped maintain the surroundingsby cutting the grasses/weeds/branches etc. In some situations, the local institutions have not been ofmuch assistance 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 in their life.This situation needs to be altered and awareness should be created regarding the benefits of reliabledata.

Figure 2.1:Field inspection of piezometers

The annual inspection team have to sensitise the local people regarding the utility of the piezometersand the need for proper maintenance. It would always be useful if the design of the structure and theinstruments used are explained along with sample sets of different data. This would generate interestin the local authorities and communities to help, if not in maintenance, at least in preventing vandalism(see Figure 2.1).

The neighbourhood of the piezometer, both inside and outside the fence, has to be examined. Waterlogging conditions, sewage dumps, pumping wells, etc. have to be identified and their influence on thedata generated examined. The corruption of the data, if any, because of the influences in theneighbourhood should be examined and remedial actions suggested. This would refer to, for instance,the growth of weeds and grass inside the enclosure and the branches of trees outside hinderingmovement and maintenance work. Provisions have to be made for cutting weeds and grass onceevery quarter and to prune the branches every year.

The cost of cleaning the neighbourhood of the piezometer should be worked out and the person whocan execute the job locally should be identified.



2.4 INSPECTION OF FENCING

In some states, piezometers with DWLR have been enclosed with barbed wire fencing. The status ofthe fence and the angle iron posts anchoring them need to be inspected. During the inspection, it hasto be ensured that the prevailing fencing is not only good currently, but will also not deteriorate beforethe next inspection (see Figure 2.2).

Figure 2.2:Inspection of fencing

The portion where the barbed wire is loose has to be identified. The maintenance requirements fordifferent tasks, including giving tension to barbed wire or replacement wherever required, and paintingor replacement of angle iron posts have to be identified. Barbed wire fencing would likely need to bereplaced more frequently in coastal areas/areas with polluted air as compared to other areasSimilarly, the angle iron posts, which are rusted, damaged and need replacement should be identified.

2.5 INSPECTION OF PROTECTIVE COVER

The piezometers equipped with a DWLR have a protective cover. In many states piezometers withouta DWLR do not have any protective cover. The design of the protective cover varies from agency toagency. It is mounted on a brick masonry/concrete (some times pre-fabricated) platform anchoredthrough bolts and nuts (see Figure 2.3).

Figure 2.3:Inspection of protection cover

During the inspection it has to be ensured, that the protective cover is in good condition, the top coveris not rusted, and that the locked doors fully protect the instruments placed inside. It has also to beensured that rainwater does not stagnate on the top of the cover or seeps through the base of theplatform. The hinges should be in good condition. The Thermocol insulation inside the box should beinspected and replacements suggested wherever required. The nuts and bolts that anchor theprotection box with the platform need to be oiled and greased regularly. The bolts will have to beopened whenever maintenance works have to be carried out on the piezometer. Provision has to bemade for painting the protective cover and the board every two years in coastal areas/ areas withheavy air pollution and in other areas every 3 years. The masonry platform also has to be inspectedfor any development of cracks. The maintenance budget should include provisions for repair of theplatform every time the protective cover is removed.



2.6 VALIDATING GEOGRAPHICAL CO-ORDINATES

The geographical co-ordinates corresponding to the location of the piezometer need to be validatedby the Data Centre Manager. The validations should be carried out with the help of the toposheet(1:50,000 scale) brought to the site. Using the Brunton compass, locate the piezometer site accuratelyon the 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 and crosssections.

Figure 2.4:Verify the accuracy of the geographicalco-ordinates assigned for the piezometerusing Brunton compass and toposheet

An alternative method to determine the geographical coordinates is by using a GPS. The accuracy ofthe GPS-system is consistently improving and already horizontal accuracy’s better than 100 meter arepossible.

2.7 INSPECTION OF OBSERVATION WELLS

The observation wells, which have been the main source of data on water levels and water quality forthe last three decades, need to be inspected. Declining water levels, drilling of bore-wells/ tube wellsas reliable drinking water source and the easy availability of power have resulted in discontinuedmaintenance of the observation wells. In the absence of alternative sources, these observation wellscontinued to be used as monitoring wells by the groundwater agencies.

Figure 2.5:Spend time at observation well site,ensure that data generated are useful,reliable and representative

Inspection of the network should focus on the relevance of some of the observation wells (see Figure2.5). The inspection should clearly indicate that the observation well continues to represent theregional groundwater system that is being monitored and continues to generate reliable data. It hasalso to be ascertained that the groundwater does not get contaminated with the surface run off,sewage/ domestic waste and can continue to be used for water quality monitoring. The well platform(in the case of domestic wells) and the stone/cement covering that prevents collapsible material fromfalling into the well also have to be examined.

0.00 50.00 100.00 150.00 200.00 250.00 300.000.00

50.00

100.00

150.00

200.00

0.00 50.00 100.00 150.00 200.00 250.00 300.000.00

50.00

100.00

150.00

200.00



2.8 INSPECTION OF SURFACE CASING OF PIEZOMETERS WITHOUT DWLR

The piezometers that have not been fitted with a DWLR in many cases do not have a protective box.The top-casing pipe of the piezometer has in many cases a protective-casing pipe of galvanised ironalong with a cap. The protective cover is usually painted. It is exposed to the vagaries of the weatherand vandalism. The status of the protective cover has to be inspected, (see Figure 2.6).

Figure 2.6:Inspect Piezometers without a DWLR.Check protective casing, cap and masonryplatform, and identify maintenancerequirements

The necessity of painting and repairs if any has to be recorded. It has to be closely examinedwhether the cap is able to cover the piezometer properly. The inspection team should recommend onthe required frequency of painting. In case the surface casing pipe is of PVC and is not protected witha GI casing pipe, it has to be ensured that the PVC pipe does not provide scope for vandalism. Thenecessity of proper fencing of the piezometer sites has to be examined. The status of the platformalso has to be examined.

2.9 CALIBRATION OF MEASURING TAPES

The first indicator of the health of the piezometer/observation well is the water level. Manualmeasurement of the depth to water level should be carried out during the inspection. The manualwater level measurements should be recorded and compared with the DWLR water levels whereveravailable or with the previous readings in the piezometers without a DWLR. The inspection teamshould discuss with the officer in-charge of regular monitoring the type of method to be used formanual water level measurement and calibration of the tape. Manual measurement, are consideredvery simple and basic, and are usually taken for granted. The errors that creep in are ignored orarbitrarily corrected. The different methods used for water level monitoring are discussed in thefollowing:

A popular method is the wetted tape (hold & cut) method. In this method a graduated steel tape isused for measuring the depth to water levels. A weight is attached to the lower end of the tape. Thelower part of the tape is coated with chalk. The steel tape is lowered until part of chalked portion of thetape is below water. The reading from the MP is noted. The tape is then pulled up and the wettedchalk portion read. This reading is then subtracted from the measurement at the MP, which is theactual water level depth. This is a very reliable method for water level measurement.

Figure 2.7:Steel tape with weight



Measurement of water levels using electrical dip tapes is another practised method. The dip tape isbattery operated and touching the water the indicator gives a beep sound/glowing light or both. Rundown batteries, poor contacts and cuts in the tape may give erroneous values. It has to be ensuredthat the graduations marked on the tape are correct. It is recommended to purchase electrical tapesfrom companies with proven accuracy and reliability. The graduations need to be validated usingmore than one tape.

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 thedata. Cross verification of the measurement of water levels more than once and adopting more thanone method should be made a standard practise, every time water level measurements are carriedout.

Figure 2.8:Electrical dip tape

2.10 EXAMINATION OF WATER LEVEL HYDROGRAPHS

The field officers responsible for water level monitoring should be concerned about more than justmeasuring water levels. They should be aware of the details of the aquifer system being monitoredand the formations penetrated.

The inspection team should reassure itself of the optimum performance of the piezometers in thecourse of the inspection. Examination of the water level hydrographs of the concerned piezometeralong with the well section and design at the site itself should be part of the inspection. The responseof the water levels to recharge and discharge effects in the form of annual and seasonal cycles has tobe verified and, wherever required, compared with neighbouring wells which tap the same aquifer.Figure 2.7 shows a typical DWLR hydrograph with rainfall and the lithological section less thandesired responses to different situations have to be taken up as cases for detailed field investigations.

Figure 2.7: Examine the response of water levels to recharge and draft. Have a goodunderstanding of the aquifer being monitored and the piezometer design. Identifypiezometers showing less than optimum response for further investigations.



In such situations, it is likely, that the water level in the piezometer is not fluctuating simultaneouslywith the piezometric head of the tapped layer, due to lack of response or time lag. The piezometercould then be failing to provide the true information of the aquifer being monitored. Water level dataemerging from such piezometers cannot be considered as reliable. Such piezometers should besubjected to detailed investigations for identifying the nature of the problem in the piezometer.

2.11 IDENTIFICATION OF MAINTENANCE TASKS BASED ON THEINSPECTION

Based on the findings from the inspection, the team should be able to recognise the physical status ofthe piezometer, as well as what is happening down the hole in the piezometer. When it becomesdifficult to recognise the sub-surface behaviour based on the available evidence, additional tests mayhave to be conducted to find out whether the piezometer is operating efficiently or maintenance hasbe carried out. The inspection team should be able to 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, and

• 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 to pick upindicators of deterioration likely to set in. Then the inspection team should be able to give expertadvice on the different standard maintenance and preventive maintenance tasks to be carried out. Inthe case of non-representative monitoring structures, decisions have to be taken on the remedialactions or alternative options recommended. The inspection team has the professional responsibilityof ensuring continued efficiency of the different structures that are part of the network.

The inspection team should report the observations in the prescribed inspection report. A sampleformat of the inspection report is given in Table 2.1, which may be customised according torequirement. The inspection report on individual observation wells and piezometers should be sent tothe concerned Data Processing Centre In-charge for information and necessary follow-up action.

The inspection findings should form the guidelines for additional field tests to be carried out andmaintenance activities initiated. Maintenance work should be carried out at the appropriate, to ensuresystematic generation of authentic groundwater data.



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 the year/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

Neighbourhood ofobservation site

Does the data need any correction

Status of theName Board

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

Is the well currently usedStatus ofObservation Well

Is the water reported to be potable




Action

Is the well reported to go dry

Is there any physical damage to the well

Does the monitoring well represent aregional aquifer system

Does the well platform protect it fromentry of surface seepage

Is the fencing completely protecting thepiezometer from vandalismDoes the fencing need any main-tenanceWhat length of fencing needs tighteningWhat length of fencing needsreplacementDoes the angle post need anymaintenanceWhen was the angle post painted lasttime

Status of theBarbed Wirefencing aroundthe piezometer

How many angle posts needreplacementIs there grass and weeds around thepiezometerStatus of the area

besides thepiezometer

Are there any branches of treescovering the piezometer which need tobe removed

Is the protective cover anchored withthe cement plat-form

Does the protective cover show anyrusting

Does the protective cover need painting

Are the doors of the protective covercompletely protecting the instrumentsinside

Does the protective cover need repairsor replacement

Status of theprotective coverof the piezometer

Do the locks need replacement

Has the masonry platform developedmajor 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 and is thecover attachedStatus of casing

pipe exposed tooutside Does the casing pipe require painting

or other maintenance

Frequency of manual water levelmeasurementsWater Level

measurements Frequency of DWLR measurement




ActionDoes the water level hydrograph clearlybring out annual/seasonal/diurnal cyclesIs there a reason to believe that thewater level hydrograph is notresponding optimallyDoes the depth of the piezometer showany reduction

Depth of thepiezometer Does the diameter of the piezo-meter

show any reduction

Observations of the team:

Recommended follow up work if any

Table 2.1: Example of Annual Operation and Maintenance Inspection Report

3 FOLLOW-UP OF FIELD INVESTIGATIONS

3.1 GENERAL

The field investigation report should clearly mention the number of observation wells that needreplacement or repair. The number of piezometers that need additional investigations have to beidentified. The report should also suggest the type of follow-up studies to be taken up (see Figure3.1).

Field Observation Inference Follow up Technical Task Remarks

Geophysical bore-hole logging

Diameter

Caving zone

Corrodedcasing/screen

Depth of the piezo-metershows reduction

Siltation due to caving fromweaker zones or break in thecasing/screens

Flushing - Development Restore the originaldepth

Cleaning through pumpingClogging of fractures/screens

Development

Remove clogging

Siltation Flushing - Development Restore the originaldepth

Steep decline in water levels Piezometer deepening or replacement

Water columns beyondmeasuring range of DWLR

Replace DWLR or change thetransducer depth

Optimal measuringrange

Non-responsive waterlevels

Reduced Hydraulicconnection with the aquifer

Hydro-fracture Improved hydraulicconnection

Growth of other obstructions For growth of roots in the bore-wells,design appropriate tools to clean thepiezometer walls of the roots

Difficulty in lowering themeasuring tape

Other obstructions Flushing

Restore the originalpiezometer design

Table 3.1: Summary of field investigation report (an example)



In the annual budget of the HIS an imported competent is operation and maintenance cast of theobservation network. In table 3.2 a list of items is presented to be considered for budgeting.

Operation and Maintenance Estimates

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

Item No. 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 sixmonths)

Job/year

4 Giving tension to barbed wire fencing Job/year

5 Replacing barbed wire fencing Job/year

6 Replacing 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

9 Replacing the protective cover (wherever required) Job

10 Repairing the masonry platform (wherever required) Job

11 Replacement of pad-locks (every year) Unit

12 Painting the outer casing pipe (wherever required) Job/year

13 Strengthening the casing pipe (wherever required) Unit

14 Sounding the piezometer (every year) Job/year

15 Geophysical down hole logging (wherever required) Job

16 Development through pumping (every three years) Job

17 Pumping tests (every 5 years) Job

18Cleaning of piezometer using cutting tool (whereverrequired)

Job

19Cleaning the piezometer using compressor (every 5years)

Job

20 Hydro-fracturing (wherever required) Job

21 Deepening the piezometer (wherever required) Unit

Total Estimate towards Operation & Maintenance

Table 3.2: Table for preparation of Operation and Maintenance Estimates (an example)

3.2 DOWN-HOLE GEOPHYSICAL LOGGING

Down-hole geophysical logging should be carried out on piezometers that are suspected of siltation,deviations, incrustations and bacterial growth that need confirmation. Logging could also be used toexamine the well design and check for breakage in the casing pipes or screens. The borehole loggingtools can be chosen from the (see Table 3.3 and Figure 3.1).

Systematic planning forO&M will call forpreparing the O&Mbudget with adequateallocation of funds forthe differentcomponents. Listing ofthe different activitiesunder O&M and repairingan estimate is a pre-requisite



Figure 3.1: Bore-hole logging tools

Type of Logging Information Obtained

Calliper Diameter of the borehole, permeable zones and type of clay, casing features, casing leaks, screenposition 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

Table 3.3: Summary of logging types and information obtained

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

The results of the logging should be the basis for deciding the follow-up activities for revitalising poorlyperforming piezometers.

3.3 PUMPING OF MONITORING STRUCTURES

The simplest method of sustaining the performance of observation wells/piezometers is throughpumping. In this method, the monitoring structure should be pumped at a discharge rate in excess ofthe potential discharge. During pumping the effort should be to over-pump the monitoring structure.Pumping would remove the storage water/ replace stagnant water as well as help in limited removal offines in the case of piezometers.

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



In the case of piezometers pumping may not always help in cleaning of the piezometer. This has to befollowed up by other steps such as using compressors, drilling rig, jetting and in limited cases evenhydrofracturing. Piezometers throwing up a big amount of fine materials during pumping run the risk ofgetting spoiled because of sand locking in the pump (see Figure 3.2)

Figure 3.2:Typical sub-surface section with submersiblepump

Cleaning of piezometers through pumping using submersible pumps needs to be carried out as aregular maintenance procedure. The frequency of pumping will vary from piezometer to piezometerdepending upon its performance. Regular checking of the specific capacity will indicate the need forcleaning through pumping. Declining of the specific capacity should be considered as an indication forcarrying out the pumping. Every piezometer has to be pumped once every three years as part ofdevelopment. In many cases the piezometers will come up for pumping as part of water qualitysampling. However, this should not be considered as a cleaning technique as the water quality-sampling pump is of low discharge. Cleaning through pumping should be considered as anindependent process.

The procedure to be adopted is to pump the piezometer using a suitable submersible pump. Thepump capacity, discharge and depth of lowering should be guided by the yields obtained duringdrilling/development of the piezometer. Preferably, the pump should be placed above the screen inthe case of unconsolidated rocks or against the deepest water-yielding zone in the case ofconsolidated rocks. The procedure should involve pumping of the piezometer in multiple spells. Waterlevels and discharge have to be monitored during the tests. Initially, the piezometer should bepumped till the water level drops close to the suction limits. The initial water is likely to be muddy withsome fines. After the pumping is stopped the piezometer should be allowed to recover. In manysituations it is likely that the pumping discharge and water level will start rising compared to initiallevels due to the process of development. This should be followed by another spell of pumping and



recovery. The process of pumping and recovery should be continued until the pumped water is clearwith no fines, and till the water level rise is stabilised.

3.4 CARRYING OUT AQUIFER PERFORMANCE TESTS

After cleaning and development through pumping it would be advisable to carry out systematic aquiferperformance test for estimating the aquifer parameters. The change in the characteristics of thegroundwater reservoir and the aquifer parameters over time, need to be understood. This would bebeneficial in improving the computation of groundwater resources (see Field Manual Part III for adescription of Aquifer Testing). The testing can be carried out using a mobile pumping test unit asshown in Figure 3.3.

Figure 3.3:Mobile pumping test unit

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

3.4.1 STEP-DRAW-DOWN TEST

The step-draw-down test should be performed on piezometers constructed in the un-consolidatedformations, primarily to understand the efficiency of the piezometer. An efficient piezometer withminimum well loss would reflect a good hydraulic connection between the aquifer and the piezometer,thereby indicating that the piezometer is reflecting the regional aquifer system very well.

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

3.4.2 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 constant dischargerate. The water level changes need to be monitored systematically in the piezometer as well as in anywell in the neighbourhood tapping the same aquifer. An analysis of time-distance-draw-down dataprovides estimates of the aquifer parameters.



The pumping tests are not an essential method in the process of development. However, they help inunderstanding the aquifer system being monitored as well as in recording any changes in aquifercharacteristics over time.

3.5 DEVELOPMENT OF PIEZOMETER

Declining performance of the piezometers will be the result of accumulation of fines in the fractures,mineral scale, slime bacteria, silt or sand build-up, changes in the aquifer or the geological areaaround the piezometer. With the right equipment and techniques, these can easily be removed fromthe piezometer. Other problems, such as large physical obstructions, extensive damage to the wellscreen, or changes in the aquifer due to natural events may not be so easily resolved.

Piezometer development should be undertaken for removing unwanted materials and improving theflow of the surrounding aquifer to the piezometer. Development should physically remove silt, clay,fine sand, scale, and befouling and correct any deficiencies during construction. This can beaccomplished through jetting, surging and/or airlifting. Development will clear unwanted materialsfrom the piezometer and its surroundings, and serve to integrate the piezometer into its environment.No matter how carefully a piezometer has been designed and constructed, over a period of timedevelopment is essential to ensure its efficiency and water quality.

Development to be carried out on piezometers drilled in consolidated and unconsolidated formationsmust be different. In the latter case, development of the piezometer would require movement of adrilling rig to the piezometer site. This needs some preparatory work including 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 to prevent damage to casing and well assembly. Detailsof the piezometer including type and combination of casing used, the total depth of casing and depth ofwater bearing zones should be made available to the development unit.

In tube well designs jetting is the most effective way to clean the well screen and rehabilitate thesurrounding aquifer. Jetting involves shooting jets of water through the screen and into the formationwhile simultaneously pumping the dislodged materials out of the well. The water column should beagitated effectively after the jetting through spells of airlifting. Chemical solutions can also be used forclearing the drilling mud clays, bentonite mud, encrustations, bacterial growth etc. Fresh water mixedwith sodium tripolyphosphate should be circulated through the screen. The well should be allowed toset until the polyphosphate can effectively work on the mud cake/ clay masses and desegregatethem. Simply poured into a piezometer, the chemicals will not be effective; they need to be followedby physical cleaning. 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 and any majorchanges in water quality subsequent to chemical treatment should be clearly recorded. Suchpiezometers should not be used for drawing major inferences on groundwater quality characteristics.

3.6 REMOVAL OF ROOTS

Special cutting tools have to be made for cleaning the piezometers where growth of roots is seen.While designing the cutting tool, piezometer details such as its diameter, the lithology of the formationand the nature of the water bearing formation have to be kept in mind. The drilling rig should beproperly positioned keeping in mind the deviations in the piezometer. The cutting tool has to belowered below the surface casing after which the walls are cleaned with a rotary movement. Thecleaning should be stopped 1 metre from the sounded depth. The cutting tool should be pulled outand replaced by the button bit, and cleaned to the bottom. Airlifts should also be carried out with acompressor. Occasionally, the cutting and air-lifting should be stopped and the piezometer allowed torecuperate before repeating the process. Airlifting has to be carried out for longer periods against thewater bearing zones.



3.7 HYDROFRACTURING

Hydrofracturing should be considered as a technical option only for reviving piezometers that showclogging of fractures or those piezometers that show limited hydraulic connection with the aquifer thatis being monitored. Hydrofracturing can be carried out in consolidated rocks especially in thosepiezometers where complete development cannot be achieved. Based on the logging data the aquifershould be isolated using packers and hydrofracturing should be carried out (Figure 3.4). Geophysicaldown-hole logging is a pre-requisite before hydro-fracturing, for isolating the aquifer being monitored.In hydro-fracturing pressurised water is injected to clear the fines from the fractures (Figure 3.5). Carehas to be taken to see that new fissures are not created in the process of hydrofracturing. Theprocess involves injection of water into the fracture zone and the fines are washed out. Specialisedinfrastructure is required for carrying out hydrofracturing and is available with the agencies involvedwith groundwater development for rural water supply. Care has to be taken to see that the waterinjected matches with the quality of water in the piezometer.

Figure 3.4: Schematic representation of hydrofracturing procedure

Figure 3.5:Inflated packer and hydrofracturing procedures



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 the hydraulic pump,• Inject water into the fracture using a high-pressure water pump. The injected water will start

working into the fracture. Continue the propagation for 5-10 minutes. Repeat the injection forshorter spells, and

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

3.8 DEEPENING OF PIEZOMETERS

Deepening of the piezometers in consolidated formations can be taken up in select cases where thepiezometers show partial penetration, seasonal drying up or large declining water levels. Thedeepening should be undertaken after ensuring that the tapped aquifer is extending deeper.Geophysical resistivity surveys should be carried out prior to deepening. Before deepening, thedeviation of the piezometers has to be examined. Piezometers with large deviations should not beconsidered for deepening. The diameter of the bit used should be considerably less than the smallestdiameter of the piezometer. Deepening of piezometers will be risky if the targeted aquifer is not clearlydemarcated. During deepening, there is a potential danger for the piezometer to collapse.

4 MAINTENANCE OF DIGITAL WATER LEVEL RECORDERS

Although the DWLRs were selected for proven reliability, they cannot be left without attention. Thedata return, i.e. the amount of collected data, and the data quality can be adversely affected by manycauses resulting in damage and/or accuracy deterioration. Damage may be caused by vandals,rodents, collapse of the well, flooding, lightning strikes, insects, corrosion, fungi, moisture ingress,battery leakage, operator error and unfortunately many more causes. The accuracy may deterioratedue to any of the above mentioned damage causes but also due to drift of sensor and electronics,slippage of the suspension, change in water density, blockage of the air vent system, corrosion,sedimentation or salt deposition on the pressure sensor.

Unavoidably, problems will arise during large-scale deployment of DWLRs. To avoid severe loss ofdata and / or deterioration of the data quality, proper measures have to be taken. Implementation of aperformance-monitoring scheme is one of such measures. The performance-monitoring scheme aimsto limit the duration of data loss, if any, and to collect reference data for validation purposes. Thesooner an instrument defect is detected, the less data might be lost. Therefore, the performance-monitoring interval should be as short as practical.

The quality of the validated data depends on the accuracy and reliability of the DWLR and also of theaccuracy and amount of the reference data. Hence, also for validation purposes the performance-monitoring interval should be short. Moreover, the effect of errors caused by drift, e.g. of the clock, ofthe pressure sensor or of the suspension can be limited by timely verification and adjustment, ifrequired.

The performance-monitoring interval could be set in such a way that the drift errors are effectivelylimited to acceptable margins and the chances of large data loss are minimised. Hence, a stable andreliable instrument may be visited less frequently than a drifting instrument and / or risky piezometerwell. Initially, the performance-monitoring interval may be as short as possible to gain experience with



the individual instruments and piezometer wells and to build adequate performance statistics. Anassessment of the statistical data may result in an adjustment of the performance-monitoring interval.

4.1 REQUIREMENTS FOR DWLR PERFORMANCE-MONITORING

The following general requirements have to be met:

• The piezometer well is properly functional

For the water level reference measurement a level (dipper) tape is used. In order to get areproducible result, the well should have a reference point that is used for all water levelreference measurements. The reference point should be clearly marked for unambiguousidentification and it should be acute-angled for accurate measurement. All measurements, bothby tape and by DWLR should be referenced to that point.

The well interior should be easily accessible for the level tape, there should be no obstructionsthat may hamper the movement/use of the tape. The level tape can deliver the required accuracyonly if it is vertical, without bends along obstructions.

• The proper reference tools are available

The time reference is derived from the clock of the DRS, the latter is synchronised with thenational time reference or with GPS time. For verification of level measurements, accurate leveltape is needed. The level tapes should have an accuracy that effectively exceeds the DWLRaccuracy, at least by a factor of 2. Comparison of various level tapes is quite instructive.Differences of 5 mm/m are common. The level tape may also be verified against an electronicdistance meter, e.g. one that is integrated in a precision 'total station'.

• The operator is properly trained

Operators who execute the performance monitoring should be aware of the objectives for theperformance monitoring. Moreover, the operator should be fully conversant with the DWLR andDRS.

• A performance-monitoring protocol is available

The performance monitoring at each station should be executed in compliance with a formalprotocol, this to collect all the required data in a standardised format which allows comparison ofprevious checklists pertaining to that station.

• A station logbook is available

The logbook of a station is the collection of all checklists pertaining to that station plus all otherdocuments related to the performance of that station, i.e. it contains all the historical informationpertaining to the station. From the historical data the operator may learn what aspects requirespecial attention, e.g. zero drift (cable grip check), moisture ingress (desiccator replacement),communication problems (spare cable required).

It is recommended to prepare and implement an operation and maintenance plan catering for:

• reference measurements,

• system performance monitoring,

• data retrieval,

• preventive maintenance, and

• fault handling.



Some activities can be executed by field staff, others require thoroughly trained staff equipped withDRS.

4.2 EXECUTION OF PERFORMANCE MONITORING

Performance monitoring should be part of standard procedures. Initially, after-set-up andcommissioning of the instrument, performance is monitored rather frequently, later, after assessmentof the collected data the monitoring interval may be optimised for best result at minimum effort andcosts.

Especially in the first year of deployment, when the DWLR properties are not fully known yet, theperformance should be monitored by manually taking accurate (better than 0.01 m) referenceobservations. Every important aspect of instrument performance should be monitored on a routinebasis. The performance monitoring should be continued during the full operational lifetime of eachDWLR. The performance-monitoring interval may be adjusted according to the findings. That is, if theDWLRs prove to function reliably, then the frequency of monitoring may be decreased to optimisecost versus data quality and data return.

Data retrieval should be done at an appropriate interval, possibly in combination with preventivemaintenance.

Preventive maintenance merely concentrates on keeping the instrument clean, changing desiccanttimely and replacing batteries. Some maintenance aspects, like replacing of batteries in sealedenclosures, may only be executed by specialists. In particular in piezometer wells, featuring high saltconcentrations, regular checks for corrosion and deposition of salts are required.

Service visits are made to the piezometer well to check the proper performance of the DWLR, tocollect reference data, to apply servicing to the instrument and to retrieve recorded data.

The data return and the quality of a water level collection network strongly depend on operationalprocedures. Frequent service visits by properly trained and dedicated service engineers are essential.

The services visits pursue following goals:

• Data recovery

Off-loaded data are to be copied immediately to an independent medium which is kept in thestation office. The primary data are transported to the custodian office and loaded into the datastorage and processing system and subsequently backed-up.

• Supervision of procedures and station operation

All stations have one or more gauge readers. These aides have to be properly instructed, trainedand guided. Careful annotation procedures as well as proper time keeping, including timely gaugereading, must be frequently reviewed. The purpose of staff gauge installation at DWLR stations,and reading of the same, is to maintain a double check against data loss due to any mishap.

• Acquire quality assurance data

In particular, manual readings should be taken during each service visit to the station,simultaneously with DWLR reading. This is one of the keys for data quality assurance andvalidation.

• Formulate recommendations and directives for local operator

In case of found irregularities in the systems functioning as well as applied procedures appropriatesteps are to be taken.

During service visits, the stations are checked for proper functioning, and procedures and factors thatmight jeopardise data yield and quality are appraised and modified. Normal operation and maintenanceworks during a service visit include:



• administration and logging,

• organisation and preparation,

• performance check,

• ventification, and

• maintenance procedures.

The activities are elaborated in the following sub-section.

4.2.1 ADMINISTRATION AND LOGGING

This involves the following activities:

• For each station a comprehensive history file should be maintained,

• For each DWLR a comprehensive history file should be maintained, and

• All findings and activities related to the field stations, instruments used, observations made, anddata collected should be logged into history file.

After each service visit, a Service Report is made, giving the details of the technical status of the station,its functioning, and any particulars of interest regarding data collection, data quality, continuity, etc. isnecessary.

4.2.2 ORGANISATION AND PREPARATION

The preparation of a performance check/site visit should be the same as described in Part IV of theField Manual. The only exception is that only spare DWLRs have to be carried and not a new one foreach piezometer that is visited.

4.2.3 PERFORMANCE CHECKS

Annotate all checks and their results in the station visit sheet, much like with the other activities andobservations. Any remedial action should take place after instrument verification. Do not pull theinstrument out of the water because this may affect its reading and / or hamper trouble shooting. Thefollowing checks have to be carried out:

• Check the local conditions.

The local conditions are assessed, in particular for changes which may affect the functioning ofthe equipment and the accuracy of the collected data,

• Check the piezometer housing for damage, tampering.

As the piezometer housing protects the DWLR and the well against external hazards, immediateaction should be taken in case the housing is found to be damaged.

• Check the well for damage, tampering.

• Check the main and safety suspensions of the DWLR.

• Check if the marking of the reference point on the well head is still in good condition.

• Check for possible slip on the main suspension.

• Check the safety wire and its fixing.

• Check the suspension cable for damage, kinks etc.

• Check the communication connector for damage, dirt, moisture.



• Check the air-vent for damage, dirt, moisture, replace hydrophobic filter if required.

• Check the desiccator for remaining capacity/saturation, replace if saturated or the remainingcapacity is not sufficient to cover the time to the next service visit.

• Check the state of maintenance of the DWLR station.

Such simple tasks as occasional painting of the housing, internal cleaning of enclosures, executionof simple repairs are easily overlooked. However, a well-maintained station will be less prone tounexpected failures, leakage, animal bite etc. Also for the local staff it must be more enjoyable towork in conveniently arranged environment than at a disorganised station.

• Annotate all observations/checks and any other observation that possibly may be of interest forDWLR operation, data validation and/or trouble shooting.

4.2.4 VERIFICATION

Verification includes the following steps:

• Retrieve the new data records from the DWLR.

• Take a manual water level observation with high accuracy level tape. For reproducibility reasons,preferably always the same level tape is used.

• Annotate reading, time, observer name, and level tape identification (which tape was used).

• Do an instantaneous DWLR level reading, annotate DWLR reading, date and time on the logsheet. The interval between instrument reading and manual observation should be kept short.

• All readings and observations should be in meters. The resolution of readings and observationshould be 1 mm.

• The instrument reading should be relative to ToC. If the instrument gives level as head, i.e. waterlevel above the sensor, then the ToC value is obtained by subtracting the head from theinstallation depth (relative to the well head). The ToC value should be positive and increase withfalling water level, it is equivalent to a manual observation.

• Verify both manual observation and instrument reading for consistency.

• Check the DWLR clock against the DRS clock: make log sheet entries of DWLR and DRS time.

• Synchronise the DWLR with the DRS clock: make log sheet entries of DWLR and DRS time.

Errors in the setting of the DWLR’s system clock result in erroneous time labels in collected data.The higher the water level rate of change the more important the clock’s setting and associatedtime keeping is.

• Do a DWLR battery voltage reading, make an entry in the log sheet, and assess the remainingcapacity

Nearly exhausted batteries have to be replaced by new ones. Remaining battery capacity mustbe more than adequate to keep the DWLR fully operational up to next service visit, this includinga practical safety margin.

• Do not erase the DWLR data. First the retrieved data have to be stored and reliably backed up inoffice. It is recommended to keep all the data on the DWLR. This is most easy if the loggermemory is organised in a ring structure. The ring structure implies that when the memorybecomes completely filled, the oldest data gets overwritten by the new data.Under normal conditions, the retrieve function should automatically retrieve the new data only.The already retrieved data does not have to be retrieved again, unless data were lost orcorrupted during transport / transfer to data storage in office. In that case, there should be anoption to retrieve data starting at a user-defined date: that is the date of the latest correctlytransferred data, or retrieve all the recorded data.

• Verify the internal consistency of the time series, e.g. by displaying a time series graph. Thisgraph should display sufficient detail to make these verifications. For that the level and timescales should be adjustable and zooming-in on particular data events should be supported by thesoftware.



• If any flaws in the data or the functioning of the DWLR are detected then these have to bedocumented and reported immediately. Prior to departing, the DWLR operator may have toexecute some trouble shooting tests and trials on site. Refer to the DWLR manual for details.The instrument should not be opened at that occasion. Returned in office, the flaw has to bereported and immediate actions have to be organised to remedy the DWLR problem.

After finishing the performance checks, the post-installation procedure should be followed to bring thestation to a normal working state in a coordinated way.

4.2.5 MAINTENANCE PROCEDURE

Proper first line maintenance should be executed, including:

• Cleaning of cable, connector and sensor.

The cable, communication connector and the sensor should be kept clean. The exterior of thecommunication connector should be cleaned during each data retrieval visit.

The cleaning of the sensor and suspension cable should be executed whenever the DWLR isremoved from the well, e.g. when water quality samples have to be collected and for troubleshooting purposes.

• Replacement of hydrophobic filter and / or breather bag.

This is executed during normal data retrieval visits whenever applicable.

• Replacement of desiccator.


• Painting.

Painting of housing should be scheduled in a general maintenance plan. However, in caseexcessive corrosion is reported the painting should be executed at the earliest occasion.

• Oiling of locks.


• Repair of damage.

In case damage is reported immediate action should be taken.

• Watch and Ward Staff.

The payment of any watch and ward staff if arranged should be executed in compliance with thecontract. Delays should be avoided.



Checklist for Maintenance of DWLRs

Problem Handing- reporting- assessment- action- follow up- monitoring- testingRole of Vendor- knowledge- replacement of defective units- repair- cable extension- training- trouble shooting- AMCSpares- spare units- spare suspension accessory- spare batteries for DWLR and DRS- spare communication cables- required numbers- where to store

- post AMCMonitoring- Investment costs- AMC costs- Operational costs- Costs of data handling- Number of piezometer wells- Number of instruments procured- Number of instruments installed- Instrument months- Number of defective and repaired instruments- Time between occurrence of defect and re-installation of instrument- Number of defective and replaced (beyond repair) instruments- Time between occurrence of defect and installation of replacement

instrument- Number of instruments connected to MSL- Maintenance interval- Re-calibration interval- Battery replacement interval- Desiccator replacement interval- Hydrophobic filter replacement interval- Manual observation interval, difference between manual/instrument

observation- Months of data retrieved (functional data collection period per instrument)- Months of valid data, per instrument- Months of invalid data, per instrument- Annual graph of retrieved data (levels/temperature), per instrument

Table 4.1: Checklist for maintenance of DWLRs

download-manuals-ground water-manual-gw-volume4fieldmanualgeo-hydrologypartviii

Technology

maintenance of piezometers

hydrology field manual

field manual deals

maintenance of observation

monitoring wells inspection

standardised procedures

operational procedures

maintenance procedure