Madagascar Water Supply Project: TAC Review Summary May 14, 2013

Madagascar Water Supply Project: TAC Review

SummaryMay 14, 2013

Ambalona, Madagascar

Population: ~800Households: ~160

~125 m

Project Objective:Domestic Water Supply

Project History

May, 2008: Initial Visit December, 2009: Test Well

Installation March, 2012: Follow-Up Assessment

• Status of test wells• Feasibility of a gravity flow system

Test Wells

May, 2008: Initial Visit December, 2009: Well Installation March, 2012: Follow-Up Assessment

Test Well Status

Village Well Several breaks in

service Low yield/sediment

School Well• Working since

installation• Serves entire village

Gravity Flow

Springs nearby

Technically feasible

High capital cost

Sustainable?

Project Process

October, 2012: Alternatives Analysis Report

December, 2012: Preliminary Design Report

January, 2013: Pre-Implementation Report

February, 2013: TAC Review

Alternatives Analysis

Gravity Flow

Wells, Solar Powered Pumps & Elevated

Water Tanks

Wells & Hand Pumps

BioSand Filters

Preliminary Design

Demand Analysis: For this population, five communal water supply points are required to meet basic water needs – 20 l/capita-day

Four new wells India MK III pumps ≥100-mm casing (allowing

for later installation of solar pumps, if desired)

Preliminary Design

Hydrogeology: Based on test well logs and slug tests, assumed unconfined conditions, Kh = 2-5×10-5 cm/s

Depth-to-water varies seasonally: ~3-7 mbgs

Porosity, anisotropy, etc. estimated

Modeled multiple well scenarios with AQTESOLV

Preliminary Design

TD: 39.5 mbgs Screened Interval: 8 –

38 mbgs Sump: 38 – 39.5 mbgs Casing: 100-mm SCH

80 PVC Borehole: 40 mbgs Cement grout surface

seal: 0 – 6 mbgs Washed sand filter

pack: 6 – 40 mbgs

Preliminary Design

India Mk II/III pumps

Sloping concrete apron

Protective casing

Fenced enclosure

Preliminary Design

Well siting criteria:• Locations decided with community• Provide reasonable access• At least 30 m from human waste disposal• At least 15 m from food/wastewater disposal• At least 30 m from animal housing• Outside areas susceptible to flooding

Solicited bids from three drilling contractors Phased implementation: build two now,

monitor, build remainder next year

TAC ReviewContext

Follows initial technical approval of Pre-Implementation Report by Project Manager

Requires short (20 minute) webinar presentation to one of the regional Technical Advisory Committees (not necessarily home region TAC)

TAC reviews Pre-Implemetation Report, HASP and slides prior to presentation

Q&A session follows presentation More than one project may be on the agenda

TAC Review:Presentation Structure

24 Slides Country Background: 3 Slides (12.5%) Community Background: 3 Slides (12.5%) Project Overview, Including Objectives,

History, stakeholders: 6 Slides (25%) Alternatives Analysis: 1 Slide (4%) Preliminary Design: 11 Slides (46%)

TAC Review:Q&A

12 Questions Country Background: 0 Questions(0%) Community Background: 0 Questions(0%) Project Overview, Including Objectives,

History, stakeholders: 0 Questions(0%) Alternatives Analysis: 0 Questions(0%) Preliminary Design: 12 Questions(100%)

TAC ReviewQuestions/Comments

Why does the well have a sump? What is the minimum/maximum grain size of

the filter pack? Has the depth of the village test well been

measured to determine is it has been filling up with sediment?

Will centralizers be used to keep the casing in the center of the borehole?

TAC ReviewQuestions/Comments

The preliminary design is for 39 metre wells, compared to 18 metres for the test wells. If the driller is unable to go to 39 mbgs, it may be possible to get sufficient yield from a shallower well.

What water quality testing has been done? The pH of well water is in the range 4.7 – 5.4.

How will this be addressed? The Denver wiki shows a high coliform count

for the village well.

TAC ReviewQuestions/Comments

The design is based on demand of 20 l/capita-day. This is too low.

Some wells are telescoped (i.e., borehole diameter is wider near the surface and narrows with depth). Was this considered?

The setbacks specify 15 metres from the wellhead to food/wastewater disposal areas. This should be 30 metres.

TAC ReviewResponse

If TAC questions and comments are not resolved during the Q&A following the presentation, the project may be put on hold until these issues are they are.

Don’t panic! This is perfectly normal. All questions and comments to be resolved are

provided in writing. Responses are submitted in the a Form 809

report – Response to TAC Comments Can be an iterative process

TAC ReviewResponse

All questions and comments must be addressed, but acceptable responses may vary from compliance to dispute, as long as they are technically sound.

Examples:• A more comprehensive water quality monitoring

program will be implemented; 30 metre setbacks will be introduced

• The 20 l/capita-day design basis was retained; telescoped well was not necessary or feasible

TAC ReviewConclusion

The Madagascar project submitted responses two weeks after being put on hold.

The TAC gave techinical approval ten days later

The project will be traveling to Madagascar this June to install two new wells in Ambalona

Final Note

Wiki as a means to preserve and share TAC experiences?