AAGC January 19-23, 2010

Cost Estimation & payback analysis

Towards Rain Cities -- Mainstreaming urban rainwater harvesting in cities

Module 7: Estimating cost and payback analysis

A. How to calculate the quantities and costs? B. Which is more economical storage or

recharge?C. What is the pay back period?D. Running and maintenance costsE. Parameters affecting the cost of RWH

A. How to calculate the quantities and costs?

ExcavationPlain Concrete CementMasonry (Brickwork) WallsReinforced Concrete CementCement PlasteringFilters Pipe work and manholes

Calculate separately for each item:

1. Assess topography of site

2. Level the required site area

3. Excavate required volume - Length x Breadth x Depth (m3)

Cost of excavation= Volume (m3) x rate (Rs per m3)

`

A. How to calculate quantities and costs? A1.Excavation

2.00

0.23

0.23

0.05

0.05

Note: When the required volume is 5 cu m, it means the inner area multiplied by depth

Brick wall

Hollow

A. How to calculate quantities and costs?A1. Excavation

Tank size (inner)-2 mX2 mX 2m

Volume of PCC of depth 10 cm

Length

(2+0.23+0.05+0.23+0.05)

Breadth

(2+0.23+0.05+0.23+0.05)

Height

(0.10)

2.00

0.23

0.23

0.05

0.05

0.10

A2. Plain Cement Concrete

A. How to calculate quantities and costs?

2.00

0.23

0.23

0.05

0.05

Section

Plan

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A3. Masonry (Brickwork) WallsA. How to calculate quantities and costs?

Tank size (inner)-2 mX2 mX 2m

Volume of brick wall 23cm thick

Length

(2+0.23+2+0.23) x 2

Breadth

(0.23)

Height

(2)

2.00

0.23

0.23

0.05

0.05

Section

A3. Masonry (Brickwork) Walls

A. How to calculate quantities and costs?

Plan

Tank size (inner)-2 mX2 mX 2m

Volume

Length

(2+0.23+0.10)

Breadth

(2+0.23+0.10)

Height

(0.10)

2.00

0.23

0.23

0.05

0.05

Section

A4. Reinforced cement concrete cover slab

A. How to calculate quantities and costs?

Plan

Tank size (inner)-2 mX2 mX 2m

Volume

Length

(2)

Breadth

(2)

Thickness

(2)

Filter volume is 30 % of total volume= 0.3 x (2x2x2)

2.00

0.23

0.23

0.05

0.05

Section

A5. Filter

A. How to calculate quantities and costs?

Plan

Cost of pipe = total length (m) x unit rate

Calculate the length of interconnecting pipe

A6. Interconnecting pipe and manholes

A. How to calculate quantities and costs?

And number of collection chambers if required

Cost of chambers = total no of chambers x unit rate

B1. Storage - Ferro cement tanksApx Rs. 2/litre

5,000 6,000 7,000 9,000 10,000Total cost inrupees 12,430 12,975 13,970 14,380 15,800

Source: Action for food Production and United Nations Children's Fund,Rooftop rainw ater harvesting systems

Capacity of rooftop water harvesting system in litres

B. Which is more economical storage or recharge?

B1. Storage -PVC tanks

Brand name

Unit cost (Rs. Per

litre)Hindustan, Jindal 1.8Storex, Ganga 2.75

B. Which is more economical storage or recharge?

B1. Storage – Brick Masonry tank

Suitable for small size underground or ground storage tanksCosts anywhere between Rs 2.5-3.5 per litre (varies as per the size of tank)

B. Which is more economical storage or recharge?

B1. Storage - RCC tanks

Suitable for underground storage tanksCosts anywhere

between Rs 3-5 per litre (varies as per the size of tank)

B. Which is more economical storage or recharge?

B1. Storage - Metal tank

Very economical for smaller size tanks

Costs anywhere between Rs 1- 1.5 per litre

B. Which is more economical storage or recharge?

How to calculate costs?S.n. Item of work Quantity Unit Rate (Rs) Amount (Rs)

1 Excavation Cu.m 902 PCC Cu m 27003 Brick work (23 cm) Cu.m 2250

Brick work (10 cm) Cu.m 25004 Plastering sq m 1005 RCC slab (100 mm thk) Cu m 5500

6 Drain pipes*M 250

7Brickbats Pebbles, sand and coir packing (filter)

L.S.

8 Interconnection pipe* M 250

9 Collection Chambers Each 500

10Drilling a recharge bore (specify size and mode of drilling)

M 250 (hand)/500

Contingency charges At 10 % Rs.Total Rs.

Specifications

1. Brick work> Cement mortar (CM) 1:6

2. Half brick> CM 1:3

3. PCC> 1: 4: 8 (40 mm nominal size for footings)

4. RCC> 1:2:4 (20 mm nominal size stone aggregates)

5. Pipe 4 or 6 kg/ cm2 HDPE pipe .

6. Manhole 60 cm x 60 cm for cleaning purpose.

C. What is the pay back period?

Method of harvestingAmount of water harvestedDepends on the city where you live

pricing rainfall patternwater requirements

Age of water harvesting system (esp in recharge)

An industry in Bangalore will effect better cost saving (due to highly priced water and temporally dispersed rainfall) than an industry in Delhi

Tex corpInvestment=Rs 5.50 lakhsRecharge and storageStorage capacity of 1.2 lakh litres at a time. Water used for non potable purposes-at Delhi rate its worth ONLY Rs 1800 but Bangalore rates 7200

And the saving on TANKERSSavings Rs 70000 per year on tankersNet saving: Lets say Rs 70000Pay back period from stored water alone is 8 years

C. What is the pay back period?- Eg case study of storage in Tex Corp Ltd

JamiaInvestment=Rs 6.25 lakhsRecharge only- yield has improved in some wells (indicator water levels)-power savings not quantified but can be doneDirect benefits-saving on TANKERSRs 3 lakhs (in 2001) now reduced by one third (approx a lakh) Net saving: Lets say Rs 2 lakh per year (will depend on rainfall and water demand)Pay back period (as calculated from savings from tankers is nearly 3.5 years)

C. What is the pay back period?- Eg case study of recharge in Jamia Hamdard

Table: Comparison of water rates

minimum charges

Unit cost slab

DomesticBangalore 90 6 0 to 15 klDelhi 40 to 150 (for

6 kl)2 6 to 20 kl

Chennai 50 2.5 0 to 10 klCommercialBangalore 360 36 0 to 10 klDelhi 250 10 0 to 25 klChennai 400 (non water

intensive)/800 water intensive

35 upto 500 kl

Industrial Bangalore not specified 60 not specifiedDelhi 600 15 0 to 25 klChennai

C. What is the pay back period?How does rate of municipal supply affect pay back period?

D. Running (maintenance) costs

You need to factor in running and maintenance costs also:Cleaning and minor repairing required Replacement or cleaning of filtersFlushing of bores (mechanical or manual)

Mechanical for three hour flushing Rs 15000Manual (using hand auger labour charges)

No energy and chemical costs

D. Running (maintenance) costs

Total cost> Number of structures; type of structures Jamia Hamdard

Rs 1.25 lakhs (2005)Rs 20000 (2004)

CSE building(Rs 400) twice a year ~ less than Rs 1000 annually

Water treatment plants-Rs 2-6 per kl depending on technologySewage treatment plants-Rs 0.60 to Rs 5 per KlDesalination- Rs 50-60 per klRO Rs 30-40 per kl

D. Parameters affecting the cost of RWH1. Catchments: Type of catchments and amount of water

harvested 2. Drainage pattern: Flow direction, spreading of rainwater

pipes and flow of storm water drains3. Retrofitting / new construction4. Geology, hydrogeology and meteorological parameters5. Purpose of harvesting6. Availability of unused tanks, dry/abandoned tube wells/

open wells etc7. Material used (PVC or MS pipe)

D. Parameters affecting the cost of RWH

D1.Catchments

Cost of RWH system is generally directly proportional to area of catchmentsFor equal size of catchments, the cost of RWH system varies (increase) from unpaved runoff to paved runoff to rooftop runoff.The RWH systems when done at community level costs less.The cost of RWH systems in clean and maintained catchment’s is less

D. Parameters affecting the cost of RWHD2. Drainage pattern: flow direction

Drainage pattern plays a very important role in over all cost or RWH system.If the rainwater outlets are spread all over the place in smaller buildings, it may require more interconnecting pipe or more structures to harvest maximum runoff, hence more costlier. If site has well defined drainage it may be easier to divert rainwater into recharge structures or storage tanks without much effort, therefore costs less.

D. Parameters affecting the cost of RWH

D3. Retrofitting / new constructionIt costs more to retrofit an existing building with a RWH system.Cost can be considerably reduced if RWH system is incorporated during the planning stage.

D. Parameters affecting the cost of RWH

D4. Geology, hydrogeology and meteorological parameters

The nature of terrain directly affects the cost eg. The cost of excavation and drilling on a hard rock terrain is more expensive. Costs are generally higher where porous strata is available at lower depth. Meteorological conditions also affect cost of storage. If the intensity of rain is high, it requires larger storage and thus increases the cost.

D. Parameters affecting the cost of RWH

D5. Purpose of harvesting

If RWH is done to meet non potable requirements ----less costIf RWH is done to meet potable requirements ---- cost is more as it requires good quality water and treatment also.

D. Parameters affecting the cost of RWH

D6. Availability of unused tanks, dry/abandoned tube wells/ open wells etcUnused tank available at site can be used as storage tanks or can be converted into recharge wells….lot of cost saving.Available dry bore wells can be used for recharging purpose---saving on drilling cost of recharge bore.Dry open wells provide good opportunity and can cater to larger catchments without much investment.