WASH Cluster – Emergency Training GWD GWD4 1 1 Groundwater Development and Drilling Session 4 Developing Groundwater Sources

WASH Cluster – Emergency Training GWD GWD4 2 Provide guidance on appropriate methods of developing groundwater resources. Clarify understanding of the development of groundwater by wells, boreholes, spring enhancement Discuss excavation and drilling techniques appropriate to hydrogeological conditions. Session Aims 2

WASH Cluster – Emergency Training GWD GWD4 3 Wells are holes in the ground that intersect groundwater and enable groundwater to be brought to the surface Holes are dug by hand or by drilling machine Walls of the hole usually supported Depth depends on aquifer type, available yield Wells and Bores 3

WASH Cluster – Emergency Training GWD GWD4 4 Drilling techniques How do you……?

WASH Cluster – Emergency Training GWD GWD4 5 Types of wells Shallow well Hand dug Unconfined water table aquifer Groundwater recovered by hand or low rate suction pump 5

WASH Cluster – Emergency Training GWD GWD4 6 Types of wells Deep well Machine drilled Confined and unconfined aquifers Groundwater recovered by pump 6

WASH Cluster – Emergency Training GWD GWD4 7 Hand excavation / boring Hand drilling – incl augering and jetting Machine drilling –Rotary, percussion, down hole hammer Drilled wells –Reach greater depths –Penetrate wider range of rocks Well installation methods 7

WASH Cluster – Emergency Training GWD GWD4 8 Hand augering a small hole –install narrow casing - tube well Hand digging larger diameter (~1m diam) Ground must be soft enough to penetrate Shallow water table required Hand completed wells 8

WASH Cluster – Emergency Training GWD GWD4 9 Likely in the very first phase of an emergency –equipment can be mobilised quickly –produced from available materials Relatively low cost Often local expertise available Can be labour intensive Application of hand completed wells 9

WASH Cluster – Emergency Training GWD GWD4 10 VIEW Video of hand augering: _WPwSZo _WPwSZo Affordable Water Well Drilling in Sierra Leone - Fresh Hope Ministries International 7min 2UMwM Hand Auger drilling 10

WASH Cluster – Emergency Training GWD GWD4 11 Shallow hand auger wells 11 A C BD

WASH Cluster – Emergency Training GWD GWD4 12 Hand dug Groundwater wells

WASH Cluster – Emergency Training GWD GWD4 13 Lining of Hand Dug wells 13 From Oxfam Manual on Hand Dug Well Equipment

WASH Cluster – Emergency Training GWD GWD4 14 Completion of Hand dug wells 14 Simple open holes, no protection from contamination Sanitary surrounds with hand pump

WASH Cluster – Emergency Training GWD GWD4 15 Drilling equipment and technique is affected by: –rock type(s) encountered –depth to groundwater –aquifer pressure Bore Drilling 15

WASH Cluster – Emergency Training GWD GWD4 16 Hand operated drilling 16 Narrow diameter (< 100mm diam) bores Casing installed to construct tube wells (narrow diameter production wells). VIEW YOUTUBE FILES Shallow percussion: Shallow percussion in Senegal: Deep well in Dhaka slums 200ft (>60m) deep:

WASH Cluster – Emergency Training GWD GWD4 17 Jetting Techniques 17 Use water pressure forced down a drill pipe through a nozzle to penetrate the soil Need a source of water and pump to provide the pressure Source: Water for the World, Constructed Jetted Wells, Technical Note No RWS 2.C.3

WASH Cluster – Emergency Training GWD GWD4 18 Jetting Techniques 18 Use water pressure forced down a drill pipe through a nozzle to penetrate the soil Need a source of water and pump to provide the pressure 20m deep jetted well, near Matatuto, Timor Leste

WASH Cluster – Emergency Training GWD GWD4 19 Jetting Videos 19 A jetting operation in Ethiopia: Jetting in Indonesia: A backyard well in USA :

WASH Cluster – Emergency Training GWD GWD4 20 Machine Drilling Advantages Can reach great depths Can penetrate wide range of rock types Can produce high yielding wells Disadvantages Expensive Require highly skilled crews Can have long lead time from set up to completion May be privately or Govt owned and not available for an emergency 20

WASH Cluster – Emergency Training GWD GWD4 21 Percussion Rigs 21 VIDEO: of cable tool operation : Application in the Philippines: crushes the rock under the weight of a tool dropped down the hole on a length of cable Suitable for unconsolidated and soft formations Relatively slow

WASH Cluster – Emergency Training GWD GWD4 22 Photo of Rotary rig, with drill bit and drilling rods visible – white tubing is PVC casing to be installed in the bore. Photo courtesy GHD Pty Ltd Rotary Rigs 22 Can drill to great depths (1000+ m) Drill bits attached to the end of a segmented string of steel drilling rods As the drilling rods rotate, the bit grinds through the soil and rock Air, water or drilling mud used as a circulation fluid to remove cuttings of rock and soil

WASH Cluster – Emergency Training GWD GWD4 23 Rotary Rigs 23 VIDEO of a mud rotary rig Some rotary rigs require no mud and are powered by air to activate the drilling bit. This is shown on the following video: ure=related ure=related

WASH Cluster – Emergency Training GWD GWD4 24 In most drilled wells, the walls need support Wells are cased with lengths of factory-made pipe Casing can be steel or plastic (Eg PVC, PE, ABS) Holes in very strong rock sometimes not cased Constructing a Well 24 Installation of plastic casing in rotary drilled bore, Photo Courtesy GHD Pty Ltd

WASH Cluster – Emergency Training GWD GWD4 25 Constructing a Well 25 Highest flow from an aquifer into a drilled well is ? through the most permeable zones Identified through: Drill cores “Cuttings” pushed to surface during drilling

WASH Cluster – Emergency Training GWD GWD4 26 Opening the well to the Aquifer 26 Cased wells need to have a screen to allow water to flow from the aquifer into the well Screens are a length of slotted or perforated pipe Typically PVC, steel or stainless steel Screens often have a filter pack to improve inflow to the well Wells drilled in stable rock sometimes are not cased and have no screen – termed “open hole”

WASH Cluster – Emergency Training GWD GWD4 27 Positioning Screens in a well 27 from Nkhoma and Baumle, (2007)

WASH Cluster – Emergency Training GWD GWD4 28 Aquifer Display of constructing a well 28 Drilled Bore (Plastic bottle) Insert narrow pipe / plastic bottle Gravel pack Flour to seal Soil mixed with flour Casing Screen

WASH Cluster – Emergency Training GWD GWD4 29 Typical Well construction 29

WASH Cluster – Emergency Training GWD GWD4 30 Summary of Types of Wells 30 Modified From Wikepedia

WASH Cluster – Emergency Training GWD GWD4 31 Well Development 31 Well development is undertaken after installing casing, screen and gravel pack Improves well efficiency Involves surging or jetting water or air in and out of the well screen to clean out residual drilling fluid. May take several days. Well developed wells have lower pump costs, longer pump life – sand and mud passing through screen damages pumps

WASH Cluster – Emergency Training GWD GWD4 32 Groundwater pumping effects 32

WASH Cluster – Emergency Training GWD GWD4 33 Completed after well development Tests the potential pumping rate and resulting drawdown Assists in determining : –Long term pumping rate and water level –Size of pump –Impact on surrounding wells or environment Test pumping of wells 33

WASH Cluster – Emergency Training GWD GWD4 34 Step drawdown test –short periods of pumping at progressively higher rates and measuring drawdown in the well –helps work out achievable pumping rate Constant rate test –Pumping at constant rate (could be for days or weeks) –Measure drawdown in well and nearby “observation” wells –Helps assess pumping impacts on the aquifer under different pumping scenarios Pumping tests 34

WASH Cluster – Emergency Training GWD GWD4 35 Measures ratio of drawdown to pumped flow rate Allows a check of well efficiency Helps indicate bore deterioration eg blocked screens Reduced capacity (greater drawdown to pumping rate) indicates reduced well efficiency Specific Capacity of a Well 35

WASH Cluster – Emergency Training GWD GWD4 36 Groundwater can be developed quickly in some situations – eg springs, shallow wells, available drilling equipment Existing deep wells may be available –Could be included in emergency water supply solution –Need to understand capacity, condition, constraints on use Potential for future development later in emergency Relevance to an Emergency 36

WASH Cluster – Emergency Training GWD GWD4 37 Springs 37 From Oxfam technical brief Spring being protected, Zaire - S House / WEDC May be harvested in a number of ways Should always be protected from degradation.

WASH Cluster – Emergency Training GWD GWD4 38 Springs 38 Spring box with discharge pipe leading down hill, Nias, Indonesia A protective box that enables: collection of water by hand discharge to a tap for collection at the spring discharge downhill by distribution pipe.

WASH Cluster – Emergency Training GWD GWD4 39 Estimating volume of groundwater available Q:How you might work out how much groundwater is available? A: Factors to be considered Area where rainfall might occur on aquifer When does it rain Will all of the rainfall enter the aquifer? The rock type Flows of existing bores / springs