Ecuadorian Gravel Pack Spring Water Supplies
Introduction
An advanced method using gravel pack to improve spring water sources developed in Ecuador provides
high quality sustaining water supplies for rural communities. The design allows substantial adaptability
for the wide variety of spring water formations encountered throughout Ecuador and requires little if any
maintenance when well-constructed. Naturally filtered spring water precludes the entrance of most
pathogens into the water supply and most often avoids the need for water treatment which is not
practical for most rural communities in developing countries. Naturally filtered spring water contains
limited organic content minimizing the amount of chlorine required to disinfect the water and taste and
odor issues sometimes associated with chlorine disinfection. Hundreds of spring intake structures built
with pick and shovel by rural communities with technical supervision by experienced personnel provide
reliable clean water supplies.
This spring protection method bears similarity to a gravel pack well albeit constructed horizontally rather
than the vertical construction of a gravel pack well. This design approach includes:
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collection of spring water subterranean using the aquifer and surrounding soil to filter the water
supply,
use of gravel pack to retain the surrounding aquifer materials and soil structure in place while
providing an easy flow path for water to enter a slotted collector pipe and flow to a receiving
tank without impounding spring water, and
protection of the collected spring water by covering the area with concrete to completely isolate
the water supply from surface water.
Studies by the Clean Water Institute of Calvin University (CWICU) indicates that this method provides
water deemed “No Risk” by the World Health Organization (WHO) in more than 50% of samples
collected. In comparison, no water samples collected from traditional spring capture methods achieved
this designation. This significant improvement provides motivation to disseminate information about this
method to promote wider use for rural water supplies. 1 2
Spring Protection Construction
Preparation
Evaluation of spring water sources includes measurement of the water quality and flow rate. The initial
results do not necessarily define the outcome, but rather only indicate of what can be expected.
Normally water quality improves after protecting the spring. The spring area can then be cleared of all
trees, stumps, and heavy vegetation.
To prepare for building the spring protection structure, a work force should be mobilized and all required
building materials conveniently available on site. Rural Ecuadorian communities customarily organize a
minga (work bee in English) in which all benefiting community members participate in the manual work.
Pea stone for the gravel pack should ideally be crushed stone 8 to 12 mm and free of fine particles and
sand to maximize voids so that water flows freely through the gravel pack. Gravel and concrete
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World Health Organization
Ten Pas
aggregates should be stored on plastic sheeting to prevent them from mixing with topsoil or organic
materials. The necessary hand tools, construction buckets to place concrete and gravel, wheelbarrows,
and concrete mixer should be available. A flat area with a hard or impervious surface for hand mixing of
concrete should be prepared when it is impractical to use a concrete mixer.
Figure 1- Typical Spring Protection Structure
Basic Steps of Spring Protection Construction
The basic steps in building the spring protection structure are as follows.
1. Clear debris and vegetation from spring area.
2. Stockpile the estimated gravel and building materials required adjacent to spring.
3. Excavate spring area to expose water producing aquifer and the underlying less permeable
strata.
4. Place geotextile against the sides of the excavation to prevent soil sloughing into the excavation.
5. Place slotted collector pipe(s) appropriately to receive spring water.
6. Excavate for cutoff wall on the downstream side of spring.
7. Place washed gravel pack around and covering PVC collector pipe while also placing concrete for
cutoff wall.
8. Rinse gravel pack to remove fines and then disinfect gravel pack with high-strength chlorine
solution.
9. Place plastic sheeting over leveled gravel pack.
10. Place 8 cm of concrete on the plastic sheeting covering the gravel pack.
11. After the concrete cover cures, place excavated soil on concrete cover.
12. Build concrete/masonry collection tank to receive the protected spring water flow.
Excavation
The spring area should be adequately cleared of all debris and extraneous materials that could
contaminate or diminish the water quality. All loose stone, roots, soil, and organic matter should be
removed to expose the strata producing water. The water bearing strata should be excavated down to
the impermeable or less permeable underlying soil or rock layer.
Geotextile
After excavating the spring area, geotextile fabric can be used to line sides of the excavation to prevent
soil or loose material from sloughing into the excavation while the gravel pack and other materials are
placed. Large nails temporarily hold the geotextile fabric in place on the sides of the excavation. The
geotextile can be folded over the gravel pack after disinfecting the gravel pack. Openings in the
geotextile in areas of significant water flow allow those water streams to flow freely into the gravel pack
and collection pipe. Geotextile can be used on the floor of the excavation if necessary to stabilize the
underlying soil. Geotextile can be omitted in areas susceptible to root growth which can form a root mat
on the outside of the geotextile and impede water flow into the gravel pack.
Collector Pipe
The PVC collector pipe can be either a manufactured slotted pipe or be slotted in the field. Slots are
normally cut into the PVC pipe making 90 to 120-degree cuts at 1 to 2 cm spacing using a hacksaw. The
narrow width of the cuts or perforations allow water flow into the pipe while retaining the gravel pack.
The length and diameter of collector pipe should be sufficient to allow all spring water to freely enter the
pipe without ponding water higher than the center of pipe. If spring water ponds at an elevation higher
than its previous state, the risk exists that spring water may eventually find an alternate discharge route
reducing water flow or causing failure of the collection structure.
The collector pipe should be arranged with the necessary fittings and adequate branches to collect all
spring water produced. An open tee in the collector pipe is often placed immediately prior to the cutoff
wall to collect spring water behand the wall. Stones can be used to chock around open pipe ends to
prevent gravel from entering the collector pipe but allowing spring water to freely enter.
The unperforated pipe carrying spring water which extends downstream from the cutoff wall should be
sloped toward the collection tank. When the cutoff wall excavation is complete, plastic sheeting can be
cut for the upstream side of the cutoff wall with a hole for the collector pipe to pass through the plastic.
Gravel Pack
After installing the geotextile fabric, the slotted PVC collector pipe can be placed on gravel or granular
material, placement of the washed gravel pack around and over the pipe can begin. Gravel should be
washed adequately to flush out the fine particles before placement. The void spaces in the gravel pack
allow spring water to flow freely into the collector pipe. The extent of the gravel pack should be large
enough to minimize the velocity at the interface with the water bearing strata and prevent piping of fines
from the aquifer. Stones can supplement the volume of the gravel pack if necessary to reduce the
amount of gravel required to fill behind the cutoff wall. However, large stone should be separated from
the fragile collector pipe by a sufficient cushion of gravel pack to avoid damaging the pipe. Voids
between large stones should be filled with gravel to form an even top surface for the plastic sheeting to
be placed over the structure to form the concrete cover.
Cutoff Wall
Excavation for the cutoff wall should be done before placing the gravel pack. The 25 cm thick cutoff wall
should be keyed 30 cm into less permeable strata underlying the aquifer or to the depth practical to
prevent spring water flow from circumventing the collection structure. The cutoff wall should also be
keyed into abutments so that the water production area is completely enclosed, thus forcing the water
to enter the collection pipe. The concrete cutoff wall is constructed simultaneously during gravel pack
placement. The downstream side of the cutoff wall can be formed using conventional wood formwork
and plastic sheeting used on the upstream side, to separate the gravel pack and the concrete cutoff wall.
The weight of the gravel pack behind the cutoff wall provides essential pressure against the upstream
side of the plastic sheeting used to form the cutoff wall during placement of concrete. Figure X displays
this step being implemented in the field.
One of the construction challenges is that cutoff wall concrete must
normally be placed in water. To address this site, concrete should be
placed as a stiff rich mix at one end of the trench excavated for the
cutoff wall to displace water out of the excavation while pouring the
cutoff wall and minimizing entraining water into the concrete. Dry
concrete mix can be used as necessary.
Disinfection Rinse
When the cutoff wall is complete, the gravel pack should be rinsed
with clean water and then disinfected with a high-strength
hypochlorite solution. Water discharged from the spring can be
collected in buckets and poured over the entire gravel pack surface
multiple times until fines are removed and the water
discharged flows relatively clean. This reduces sediment and
fine particles remaining in the gravel pack after placement.
Rinsing the gravel pack with hypochlorite solution reduces the
presence of bacteria. A hypochlorite solution of 300 ppm can be
made using granular calcium hypochlorite or liquid bleach (sodium hypochlorite). One tablespoon (5ml)
of granular calcium hypochlorite mixed in 10 L of water produces a 300-ppm solution. When preparing
the disinfection solution, it is advisable to wear rubber gloves and eye protection.
Spring Protection Cover
After disinfection of the gravel pack, plastic sheeting should be placed over the gravel pack and concrete
poured 8 cm thick to provide a protective concrete cover. The concrete cover should be keyed into the
surrounding soil structure so that neither rainwater nor surface water can penetrate the protection
structure without being filtered through the surrounding soil alluvium. Soil previously excavated from
the spring area should be placed over the concrete after it has adequately cured to further protect the
spring.
Trench Style Spring Protection
This spring protection method can be adapted to collect ground water produced over a larger area by
constructing a trench collector of the length necessary. Numerous spring protection structures of this
type can be used to collect spring water flowing to a single collector tank. Figure X shows a profile and
plan view of a spring protection structure used for localized springs.
The trench style spring protection structure can be built on an axis approximately perpendicular to
groundwater flow. On sloped spring areas, plastic sheeting placed on the downhill side of the trench
forces water to enter the collector pipe.
Figure 3- A Plan Schematic of a Trench Style CODEINSE Spring Protection Structure
Figure 4- A Section Schematic of a Trench Style CODEINSE Spring Protection Structure
The trench-style
spring protection
components are
similar to the
previous
description. The
trench should be
dug to a depth that
maximizes the
water flow to be
captured, lined
with geotextile
fabric on the
upstream face, and
plastic sheeting
placed on the downstream trench face. In cases where the ground water flow enters from both sides of
the trench, geotextile fabric can be used to line both sides of the excavation to prevent soil from
sloughing into the trench. A slotted PVC pipe placed in the trench collects the water and the trench is
filled with gravel pack using the same principles described previously. The collector pipe should slope to
allow open channel flow to the collector tank so that water flows freely to the collector tank and the
pipe also acts as a breather for the spring protection structure.
Concrete cutoff walls constructed normal to the trench axis or plastic sheeting can be used to direct
water into the collector pipe. PVC pipe without slots extends from the cutoff wall to the collection tank.
Rinsing and disinfection of the gravel pack should use the same procedure previously described. Trench
spring collectors can be connected in series to one another when collecting groundwater flowing
through a large area of alluvium. Figure X illustrates a trench spring collector.
Springs in Rocky Locations
Rocky locations provide more stable circumstances for spring protection because the release of fine soil
particles into the collected water is less likely. Excavation for spring protection structures built in rocky
locations, require that all loose rock, and organic material such as moss, roots, and lichens should be
removed. Rock surfaces to be covered with gravel filter pack should be first scrubbed with a wire brush
to remove organic growth. Cracks and fissures in the surrounding rock outside the spring collection
structure where roots could penetrate the filter pack should be grouted with cement or cement mortar.
The placement of the filter pack, cutoff wall, concrete cover, and collection pipe should be like the
process described in the localized spring protection structure; however, when installing the cutoff wall,
the surrounding rock surfaces should be thoroughly cleaned and roughened to prepare the surface so
that the concrete adheres to those surfaces (Rydbeck and Guapi 5).
Collection Tank
The collection tank can be built at any time during the spring protection process in a dry location remote
to the spring. The collection tank water surface should be lower than the elevation of the spring itself
allowing spring water to freely flow into the collector tank. The sloped pipe from the cutoff water to the
collection maintains open channel flow so that the pipe also acts as a breather for the spring protection
structure. Figure X shows a typical collection tank.
Figure 5- A Section View of a Collector Tank
Collector tanks are normally constructed on a reinforced concrete base with reinforced masonry walls
and a reinforced concrete cover. Masonry walls are filled solid with concrete and cement plastered
interior and exterior using acrylic bonding agent to provide adherence to the masonry. Waterproofing
additive should be used for the interior cement plaster. Collection tanks include access for periodic
maintenance with a secure hatch cover, constructed of steel or aluminum such that the metal cover
overlaps the frame (Figure X) to keep rainwater, dust, and insects from entering the collection tank. The
cover should include provisions for a padlock to prevent unauthorized access to the water supply.
The vertical PVC overflow pipe controls the water surface elevation in the collector tank to prevent
pressurizing the spring. An unglued connection at the overflow pipe base allows removing the pipe to
drain the tank. The drainpipe should discharge to an appropriate location where flood levels are lower
than the water surface elevation of the collection tank so contaminated flood water does not enter the
collection tank. The inlet to the collection tank outlet pipe to the water distribution system includes a
short piece of vertical pipe raised above the floor so that any sediment or sand generated by the spring
does not enter the water system and can be observed. These design features preclude the need for
outlet and drain valves which simplifies construction. Multiple spring protection structures can each
direct their flow to a single appropriately located receiving tank to economically develop the available
spring formations and provide the water flow required.
Spring Capture Construction Summary
The advantages of this spring protection method are the following:
● This method adapts to the widely varying and disperse nature of springs to collect the amount of
water needed for the water system.
● Most often the difficult aspects of building a spring protection structure in a water producing
area can be completed in a single day. This improvement substantially reduces the difficulty of
constantly removing mud and dewater the construction area multiple times which is normally
required to build a spring box.
● The cut-off wall enables the structure to collect the maximum amount of spring water possible
and prevents piping under the structure which can eventually cause failure.
● This method completely isolates the collected spring water from any surface water inflow
whereas surface water can potentially flow down the face of the spring box structure into the
aquifer and enter the structure.
● This spring protection method can be used at a site periodically inundated since the collector
tank located remote to the spring at can be designed with an overflow discharge above flood
level.
● The collector tank allows observation of the spring flow rate and any sediment produced by the
spring.
Community Development Principles
In addition to thoroughly protecting the spring water source, the community should prepare to
successfully operate and maintain the water system. A high level of ownership by the community is
generated when each family receiving water provides labor to build the project and a significant amount
of the finances needed. Prior to building the water system, Ecuadorian communities elect a legally
recognized community water board (junta administrativa de agua potable). They also commit to building
a latrine or toilet for each home, long-term maintenance of the water system, and charging each home a
per cubic meter water use fee to finance a water system operator (aguatero) and the tools, pipe, etc. to
maintain the water system. Each water service includes a meter to measure water use and residents
pay for the water quantity consumed. The aguaterro takes responsibility for conducting the routine
maintenance and collecting fees, to ensure a successful water system. Adequate follow-up visits after
completion of the water system are important to help resolve any operational or maintenance issues.
Acknowledgements:
This spring protection method was initially developed by Desarrollo Comunitario Vozandes, a Christian
ministry serving in Ecuador since 1978, and an arm of HCJB World Radio. Since 2014, the work has been
implemented by Corporación de Desarrollo Integral Socio Económico (CODEINSE), an indigenous,
Christian, Ecuadorian ministry located in Riobamba. CODEINSE provides WASH solutions, engineering,
and technical assistance to communities building, improving, and maintaining their water systems. The
ministry is supported by Life Giving Water International (LGWI) and expatriate volunteers affiliated with
LGWI. We are indebted to the hundreds of individuals and churches that support this work and to the
Divine Hand of Providence.
The Clean Water Institute of Calvin University (CWICU), a research institute in Grand Rapids, Michigan,
focuses on global sustainable water supply solutions. CWICU’s interdisciplinary research engages faculty
and students of engineering, chemistry, political science, and public health to identify lasting solutions in
clean water supply. CWICU’s partnership with CODEINSE and LGWI, began in 2016, to research solutions
in providing clean water for the communities they serve.
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