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TECHNICAL MEMORANDUM

Hydropower Feasibility Assessment for the

Town of Joyabaj, Guatemala

Prepared for

Prepared by

March 2016

T E C H N I C A L M E M O R A N D U M

Hydropower Feasibility Assessment for the Town of Joyabaj, Guatemala

PREPARED FOR: Municipality of Joyabaj

PREPARED BY: Engineers Without Borders-USA, CH2M Team

DATE: May 10, 2016

Executive Summary of Assessment In early 2016, a team of professionals visited the Municipality of Joyabaj to study the feasibility of re-commissioning the hydroelectric system that produced power from the 1960s into the 1990s. In 1993 the regional utility grid was extended to Joyabaj and the facility was removed from service. The objective of this study is to determine whether the costs associated with updating the facility to once again produce power can be offset by savings from purchasing power from the regional supplier, INDE. This study consists of three general alternatives:

• Alternative 1 – Rehabilitation of the existing Kubota pump-type turbine

• Alternative 2 – Replacement of the existing Kubota pump-type turbine with a new turbine

• Alternative 3 – Rehabilitation of the existing Kubota turbine and the addition of the new turbine

Before studying each alternative, some fundamental questions needed to be researched:

1. Is there ample flow in the river to produce electricity? YES. The Hydraulic Assessment portion of the study, as well as Attachment B, discuss the seasonal flow available to the turbine. For the majority of the year at least 600L/s flows through the channel, which is sufficient to produce power for Alternatives 1 and 2, and during the wet season flows reach 9,000L/s. For approximately 6 months out of the year, it is possible to run two turbines, as discussed in Alternative 3.

2. Is it possible to refurbish the existing generator? YES, for the newer Kubota unit, but not for the older Drees unit. The Drees unit from the 1960s is beyond repair, but the Kubota unit has many components in relatively good condition. The gearbox and the control panels would need to be completely replaced, but the overall unit can be salvaged. Alternative 1 includes the refurbishment of this unit.

3. Is it possible to connect the power produced at the facility into the existing Joyabaj distribution system? YES. Although the specific point of connection was not identified as part of this study, representatives of the Joyabaj electric department were aware of the former routing of the transmission line. This will need to be finalized in the design of the project, and appropriate rights-of-way will need to be obtained.

4. Are the existing dam and channel still in good condition? YES. The Civil Works Assessment portion of the study reviewed the dam, channel, forebay, overflow spillway, penstocks, powerhouse, and tailraces and found them to be in need of some repairs but not major structural revisions. Several recommended repairs are noted, with costs ranging from $30,000 to $40,000 for each of the alternatives.

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HYDROPOWER FEASIBILITY ASSESSMENT FOR THE TOWN OF JOYABAJ, GUATEMALA

With the determination of these four questions being “YES”, the potential hydropower development was estimated for each of the three alternatives:

DESCRIPTION EQUIPMENT RATING ANNUAL ENERGY PRODUCTION

ESTIMATED COST

ALTERNATIVE 1 Rehabilitation of the existing Kubota pump-type turbine

64 kW

600 L/s FLOW

521,395 kWh $180,140

ALTERNATIVE 2 Replacement of the existing Kubota pump-type turbine with a new turbine

78 kW

600 L/s FLOW

635,450 kWh $673,952

ALTERNATIVE 3 Rehabilitation of the existing Kubota turbine and addition of the new turbine

64 kW & 78 kW

1,200 L/s FLOW

900,328 kWh $783,248

Given the estimated power production and the estimated costs, an Economic Evaluation shows that there are positive rates of return for each of the three alternatives, with payback ranging from just under 4 years (Alternative 1) to 9 years (Alternative 2). Attachment F provides additional background information on the analysis.

Based on the initial review of the facility, we recommend proceeding with Alternative 1. Doing so should provide a payback to the Joyabaj electric system, offsetting costs paid to INDE by reducing that demand. While feasible to move forward with Alternative 3 at this time, there is a larger cost and longer payback time involved with that option, and the second turbine can be added at a later date as a “Phase 2” of this project if so desired.

Utilizing a renewable resource at a facility that can be placed into service with minor upgrades and repairs is a sound concept. In order to proceed, we recommend the following actions:

1. Review this report and inform us if any portions of it appear to be incorrect or are unclear. If there are any questions about what is included here, it would be helpful to address those before moving along further.

2. Coordinate with Engineers Without Borders or another engineering company for the Final Design of the project. This is a complex facility, and there are significant costs associated with the work. Having a constructible design, complete with specifications on the equipment, will save costs and will serve as the basis for future maintenance and future phases of the project. This document should not be viewed as a design for the project.

3. Seek funding for the project. Alternative 1 has an estimated cost of $180,000. Funding sources should be explored to assist in the implementation if sufficient municipal resources are not available. Partners such as Engineers Without Borders can assist in identifying funding sources and writing grant proposals for this work.

Once these three items are in place, construction may begin on a project that should benefit the citizens of Joyabaj for many years to come.

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Introduction The objective of this report is to provide the Municipality of Joyabaj, Guatemala with an assessment of the hydroelectric facility located at the existing Powerhouse site. The assessment will provide a basis for Joyabaj’s leaders to consider whether to proceed with re-commissioning the site. This work was performed by engineers from CH2M as a service to Engineers without Borders USA and is organized in 10 sections plus attachments as follows:

• Executive Summary of Assessment

• Introduction

• Hydropower Background in Joyabaj

• Hydraulic Assessment

• Existing Turbine Generator Assessment

• Interconnection and Power Transmission Facilities Assessment

• Civil Works Assessment

• Operational and Safety Considerations

• Potential Hydropower Development

• Economic Considerations

Three alternatives have been developed for this report, based upon different equipment configurations and generating capacities, resulting energy production, complexity, and cost. The following additional alternatives were discarded as the study progressed:

1. Do Nothing: The “Do Nothing” alternative consists of choosing to not produce power at the site. Although the current Joyabaj electric distribution system is functional by simply purchasing wholesale power from the national (INDE) grid, each of the three proposed alternatives appear to provide the potential to produce a portion of Joyabaj’s power at less than this wholesale cost. Additionally, the power produced by the turbine-generator is more sustainable because the re-commissioning of the existing facility has a zero-carbon footprint, unlike the power purchased from the national grid.

2. Complete Project Replacement: The “Do Everything Over” alternative, wherein all project facilities – power plant, penstocks, flume, and dam – are replaced was deemed to be unnecessary since the civil works, although in need of some repairs, can be re-used. Costs for total replacement were not developed but could reasonably be assumed to be an order of magnitude greater than the costs developed in the three alternatives.

Detailed information supporting this Technical Memorandum is included in the following six Attachments:

• Attachment A: Cost Analysis

• Attachment B: Hydrograph and Rainfall/Flow Calculations

• Attachment C: Civil Works Defects and Remedial Works

• Attachment D: Drawings and Site Visit Records

• Attachment E: Cost Estimates

• Attachment F: Basic Economic-Feasibility Evaluation

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Hydropower Background in Joyabaj Power output from a hydropower turbine, regardless of size or type, is proportional to flow through the turbine and the head (or differential pressure) across the turbine. In principle, low-head/high-flow and high-head/low-flow conditions offer the same power and energy potential. The power formula for a hydraulic turbine-generator is:

Power output in kilowatts (kW) =

Q (cfs) x H (ft) x Turbine-generator efficiency

11.82

The energy produced in kilowatt-hours (kWh) equals the average power output multiplied by the operating time in hours. Generally speaking, turbine equipment utilizing large flows under low head are more costly than that operating under high heads at low flows. Further, turbine performance is also determined by the consistency of operation. A higher efficiency is realized when the head conditions are fairly constant compared to lower efficiency when the head is variable resulting in limitations in operating range.

At Joyabaj, power was produced from the 1960’s until 1992 using the older unit, a horizontal Francis-type turbine manufactured by Drees & Company of Germany. In 1992, the second, newer unit was installed, a split-runner pump-type turbine manufactured by Kubota of Japan. The newer unit only operated for a short time. When the regional utility grid supply was extended to serve Joyabaj in 1993, the plant was decommissioned. It was not clear that the two units ever successfully operated at the same time. Both units were designed to operate on an isolated grid, regulating voltage and frequency. The first unit’s output was regulated by a conventional mechanical governor. The second unit’s output was regulated by an electric load governor whose load bank was water-cooled.

The original Drees unit is no longer in serviceable condition, having been largely dismantled and demolished for scrap. The Kubota unit turbine is mostly intact, but the gearbox, generator, and controls have been demolished for scrap. Its repair and refurbishment appear practical.

A range of alternatives for restoring hydropower generation are also possible. In addition to rehabilitation of the Kubota unit, the installation of a new replacement turbine generator can be considered. The flow capacities of each would closely match that of the existing equipment. New equipment could range from two small off-the-shelf pump-type turbines; a single, custom non-adjustable turbine; and a custom, fully-adjustable Francis-type turbine. The latter could be adjusted across the full range of available flow. The costs for these vary widely. In order to offer a reasonable range of options, this report presents three alternatives for restoring hydropower generation at Joyabaj, along with costs and an analysis of the economic viability for each. They are:


• Alternative 2 – Replacement of the existing Kubota pump-type turbine with a new turbine

• Alternative 3 – Rehabilitation of the existing Kubota turbine and the addition of the new turbine

The rationale for selecting these alternatives was:

• Alternative 1 – Simplest and lowest cost

• Alternative 2 – New equipment with Improved power output but higher cost

• Alternative 3 – Combination of alternatives 1 and 2, representing an approach for combining their advantages and offering a path to developing the site in two phases.

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Hydraulic Assessment The following presents the hydrology, net head, and energy methodology used for preliminary equipment selection and determination of the energy benefit of a hydroelectric facility at the site. The flow available to turbine-generator equipment is dependent on the hydrology at the site and the capacity of the conveyance channel.

Flow Available to the Turbine-generator An existing dam diverts flow from the river to supply the turbine-generator via open, rectangular channel or flume. The concrete channel is roughly 2.9 feet wide and 3.3 feet tall with a total length of 417.5 meters and a slope of roughly 1 percent. The capacity of the channel itself can be estimated using Manning’s equation, as shown in the following Equation, where Q is the flow, n is Manning’s roughness, A is the cross sectional area of flow, R is the hydraulic radius (or the cross sectional area divided by the wetted perimeter), and S is the channel slope.

𝑄𝑄 =1.49𝑛𝑛

𝐴𝐴𝑅𝑅2 3⁄ √𝑆𝑆

Assuming a flow depth of 2.25 feet and an operating freeboard of about 1 foot, and using a roughness value of 0.016, the channel’s capacity is about 56 cfs or 1.58 m3/s.

At the dam, a sluice gate controls flow diverted into the channel. While the gate itself requires replacement, the available opening at the gate appears to be adequate to supply the above channel capacity.

Available Flow Stream flow at the Joyabaj site was estimated from limited historical flow and rainfall data from nearby stations, as detailed in Appendix B. An annual hydrograph is presented in Figure 1. The estimated flows range from about 0.5 m3/s in the dry season to more than 9 m3/s at the height of the wet season.

In order to estimate flow available for diversion for hydropower generation, these figures were reduced by 10 percent, accounting for minimum streamflows to remain in the project reach of the river and an allowance for existing irrigation diversions.

It should be noted that this hydrologic analysis is based on limited data and is intended only to obtain a rough estimate of flow that may be available for hydropower generation. In order to provide actual data for this purpose, a stream gauge was installed at the existing dam to measure the flow throughout the year. This information will be critical to establish the low flow condition during the dry season, as the estimated hydrograph may not be accurately reflecting spring/groundwater flow during the dry season. At the time of the study (mid-January 2016), the flow was measured to be approximately 900 l/s based upon a broad-crested weir calculation and the flow in the channel. The flows were also measured in March and April and remained constant with the January measurements. Based on discussions with the operators of the previous system, and for simplicity’s sake, it will be assumed that at least 600 l/s is available throughout the year for hydropower generation, but this should be monitored through multiple seasons, particularly if Alternative 3 is selected.

These estimated available flows appear to correlate with nameplate capacities of the two existing turbines.

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Figure 1: Projected Hydrograph at the Joyabaj Site

Table 1: Estimated Average Daily Flow Available for Hydropower Generation

Month Available Total River Flow (l/s)

Calculated Available Hydropower Flow (l/s)

Assumed Available Hydropower Flow for Analysis (l/s)

January 639 575 600

February 526 473 600

March 456 410 600

April 451 406 600

May 900 810 810

June 2,921 2,629 2,629

July 4,359 3,923 3,923

August 5,168 4,651 4,651

September 9,754 8,779 8,779

October 5,896 5,306 5,306

November 1,784 1,606 1,606

December 886 797 797

3.5 4.8 4.2 4.2

12.1

5.91.0 0.6 0.3 1.0 0.4 0.5

0

9

18

27

36

450

3,000

6,000

9,000

12,000

15,000

May

-03

Jun-

03

Jul-0

3

Aug-

03

Sep-

03

Oct

-03

Nov

-03

Dec-

03

Jan-

04

Feb-

04

Mar

-04

Apr-

04

Flow

(L/s

ec)

Rain (in) River Flow (L/s) Flow Available (L/s) 1 Turbine 2 Turbines

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Available Head On the basis of previous surveys and measurements conducted during the site investigation, the gross available head was estimated to be approximately 17 m. The basis for this value is the difference in elevation between the nominal operating water surface elevation in the forebay structure (assumed to be the spillway crest elevation) and an estimated water surface elevation in the power plant tailbays. Head losses through the intake and penstock serving a turbine-generator unit were estimated to be no more than 0.5 m, yielding a net available head of about 16.5 m.

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Existing Turbine Generator Assessment The configuration and condition of the abandoned equipment and piping in the existing power plant were observed. Turbine inlet and outlet (draft tube) piping appeared to be in serviceable condition. The 500 mm butterfly-type inlet valve installed upstream of the newer Kubota turbine was removed from the piping and examined. The valve appeared to be serviceable.

The older Drees unit consists of inlet and outlet piping, spiral casing assembly, shaft and flywheel, generator stator housing, and governor assembly. The turbine runner and bearings are absent. All components are beyond repair and could be salvaged for scrap. No electrical switchgear or controls are present. The tailbay is filled with debris and its tailrace (discharge channel to river) is infilled with earth.

The newer Kubota unit consists of inlet and outlet piping, turbine housing with runner, partial shaft, gearbox housing (gear train absent), generator stator housing (rotor and shaft absent), governor load bank cooler, and control panels. Repair and refurbishment of the turbine itself appeared practical. The gearbox and generator components are beyond repair and could be salvaged for scrap. The control panels are completely gutted and could be salvaged for scrap. The tailbay is filled with a layer of debris, but its tailrace is serviceable.

On the basis of the nameplate, the rated capacity of the newer unit is 600 lps, under a net head of 16.9 m. It is anticipated that the unit could be rehabilitated to operate under a similar condition.

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Interconnection and Power Transmission Facilities Assessment The original power plant included a substation situated on a pad over the tailrace channel. From there, an overhead transmission line extended to the distribution system of Joyabaj. The transmission line alignment appears to have extended straight up hill to a location along the upper section of the access roadway. The original substation appeared to consist of an outdoor power transformer with exposed top-mounted bushings, exposed conductors up to fusible switches on a wood pole deadend take-off structure. Transmission voltage was 13.8 kV.

The outdoor transmission line deadend take-off structure is intact and standing, but condition of its wood poles is undetermined. The abandoned step-up transformer consists of tank only and is suitable only for salvage as scrap.

On the basis of discussions with the municipality’s utility staff, it appears that a transmission scheme similar to the original one can be installed. A proposed interconnection location with the local 13.8 kV distribution grid was identified at about 1.5 km from the power plant. The basis for this location was not determined (perhaps the nearest location of 3-phase circuits).

Interconnection of the new power plant with the municipality’s electric system should be possible without significant issues. However, the configuration, capacity, operation, and protection scheme for the system at the proposed connection location are currently unknown. The municipality plans to obtain and provide a system diagram and map for further analysis. In order to ensure that the connection and operation of the hydropower station does not impact safety, protection, reliability, or performance of the municipality’s electric system, a thorough analysis is necessary.

For the purposes of this assessment, it will be assumed that a straightforward interconnection can be installed and that the allowed costs are adequate.

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Civil Works Assessment A visual inspection of the scheme’s civil works was carried out, which included:

• Diversion dam

• Flume and flume stilling basin

• Forebay structure

• overflow spillway

• 2 penstocks

• Powerhouse

• 2 tailraces

Figure 2 shows a high-level schematic of these structures.

Figure 2: High level schematic of civil works structures

The objective of the inspection was to assess the condition of the structures, identify defects, and scope out remedial work required. A local contractor was consulted to provide advice on construction

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practices in the region and ensure remedial work could be feasibly carried out using local resources and labor.

Diversion Dam The diversion dam is a buttress gravity dam, approximately 3.75m tall, with a crest width of approximately 0.50m. Figure 3 shows a view of the dam from the downstream, and

Figure 4 shows a best-estimate on the cross-section of the dam. Design or as-built drawings of the dam were not available, and not all aspects of the dam could be measured during the evaluation. The items physically measured and used to develop the cross-section included (note that left and right refer to the dam when looking downstream):

• Vertical distance from reservoir pool to tailwater pool (3.75m)

• Height of water passing over the dam crest (50mm)

• Width of dam crest (0.50m)

• Length of dam crest (26.90m)

• Upstream dam slope (1:12 (H:V))

• Downstream slope (vertical for 1.42m below crest, 1:1.63 (H:V) below 1.42m)

• Buttresses (4.1m, 8.2m, 11.7m from left abutment vertical wall)

• Downstream scour hole (up to 2m below tailwater, up to 100mm horizontally under downstream toe)

• Upstream sediment depth (4.3m over the right half of dam, 0.6m over the left half of the dam)

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Figure 3: Downstream View of the Diversion Dam

Figure 4: Diversion Dam Cross-Section

The dam is a run-of-the-river dam, with the gravity section providing the spillway. Operators noted that during major rain events, it is not uncommon for there to be 3m of flow over the dam. There were indications of scour downstream of the dam, both under the flume as well as on the right abutment downstream of the dam and under a portion of the right toe of the dam. However, none of the scour

bedrock joint slope typically around 30-35°, spacing 0.1 to 1.0m

sediment thickness

varies from 0.6m to 4.3m

scour hole up to 2m

3.75m.

±1.00m.

buttress

? ? ??

?

??

?

?

Low-level outlet

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observed appeared to pose any threat to the stability of the dam, though it is recommended that the scour be monitored after each wet season and actions implemented to stop the scour if it progresses further under the dam or erodes either abutment.

The dam alignment appears to have a “bow” near the right abutment, and has a slightly varying crest width (Figure 5). It was noted by maintenance personnel that this “bow” was an artifact of the original construction and does not represent damage or movement of the dam.

Figure 5: dam crest

The abutments appeared to be in good condition, with no visible seepage noted through joints or fractures in the rock.

Based on discussions with maintenance personnel, the dam originally included an elevated walkway across the crest of the dam that was used to access the right abutment, as well as access an operator for the low-level outlet. The walkway and gate operator were destroyed during a flood. The low-level outlet is visible in Figure 3 to the left of the middle buttress near the bottom of the dam. It is not clear if the gate can still be operated, but the operator was not observed during the inspection and the upstream side of the gate as it is buried under sediment. One of the maintenance personnel noted that he had operated the low-level outlet three times during the 1980s before its being destroyed. It is recommended that the low-level outlet gate valve be replaced. A new permanent walkway is not recommended given the potential damage due to future flood events. However, safe access to the gate valve is required, and two options were considered: (1) a small boat be stored at the dam and used to access the gate valve as necessary or (2) a temporary walkway be designed and constructed that can be lowered into place when access is required.

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The inlet to the flume consists of a sluice gate operated on the upstream face of the headwall, as well as a second sluice gate operated on the downstream face. In discussions with maintenance personnel, it was noted that the upstream gate was installed during the original dam construction. The downstream gate was added in the early 1990s during installation of the new turbine (possibly because the original upstream gate had failed). It is not clear if either gate is still operable, though it is our understanding that the downstream gate has been used most recently. The upper gate does not currently include an operator, though the stem is in place. Both gate valves are in poor condition and are recommended to be replaced.

The flume intake section used to include a training wall or trash rack that provided protection of the gates from the flow and debris in the river. Remnants of the wall are visible upstream of the outlet works. The training wall should be reconstructed and is included in the cost estimates.

Flume Comprises a channel approximately 420 m long, with typical internal dimensions of 0.9m wide by 1 m high. The local utility advised the original channel walls were 0.5m high; these were raised to 1m high in the early 1990s to increase the flow capacity of the channel, as part of the second turbine installation. The original channel walls typically comprise 150 mm thick concrete sections (reinforcement content not known), and the raised sections range from approximately 125 mm to 300 mm thick and are constructed from unreinforced cyclopean concrete. See Figure 6.

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Figure 6: damaged section of flume wall showing construction form

The channel base slab thickness was measured as being 150mm thick in one isolated location only. Lightly reinforced concrete planks span between the walls for a significant length of the channel. A detailed description of the flume from a site survey is in Attachment D.

Flume Sediment Trap Approximately 40m downstream of the dam, the flume includes a basin (Figure 7) to collect sediment, and two gate valves to flush the basin. The basin depth was uncertain, but a minimum of 2m, and was almost entirely full of sediment. The operability of the gate valves is unknown, but they appear to be inoperable and are recommended to be replaced.

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Figure 7: Flume Sediment Trap, full of sediment and plant growth

Forebay structure The forebay structure, shown in Figure 8 and Figure 10 is constructed from concrete walls typically 300mm thick. Reinforcement content is unknown. There are 3 cells, the first (most upstream) is separated from the others by a trash rack. The downstream cell was constructed later to serve the second penstock and powerhouse extension, to accommodate the second turbine.

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Figure 8: forebay structure

Spillway Shown in Figure 9, this structure conveys water from the forebay structure away from the hillside above the powerhouse to a safe location where it flows back into the river. The layout of the structure and its key components are also shown in Figure 10. Walls are typically 150mm thick concrete, reinforcement quantities are unknown.

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Figure 9: forebay structure spillway. Photo taken from Forebay structure.

Figure 10: Forebay and spillway schematic

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Penstocks Both penstocks fall about 17m vertically. The older penstock appears to be about 600 mm in diameter and of ductile iron construction. It is buried along its entire length, except where it enters the back wall of the power plant. The newer penstock has a diameter of 460mm. and is manufactured from ductile iron. There are 3 concrete thrust blocks, approximately 1m3 each, at roughly 5m, 11m and 30m downstream of the penstock inlet. See Figure 11.

Figure 11: penstock and thrust blocks

Powerhouse Refer to Attachment D for rough sketches of the powerhouse building. It has a concrete slab floor, rendered masonry walls and a roof comprising timber trusses and corrugated metal. These dimensions may be used in developing schematic engineering drawings.

Tailraces Rectangular channels with concrete walls, approximately 8m long, discharging into river. The older tailrace channel has concrete walls near the building, but is an earthen channel beyond. The newer tailrace was constructed as part of the second turbine works and consists of a narrow vertical-walled channel.

Results of inspection All structures are in fair condition, no sign of significant or widespread deterioration were identified. Concrete construction forms the majority of the structures; this was observed to resist moderate striking with a hammer, showing no signs of crumbling. There is no evidence of long term cracking of the concrete (with the exception of discrete structural cracks documented in the flume site walkover record (Attachment D). Based on the historical performance of the structures and their current condition, it is reasonable to expect a residual service life in excess of 25 years.

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However, a series of defects and recommended remedial work for the civil works were identified and will require addressing as part of any refurbishment project (see Attachment C for details). The most significant of these are listed below:

• Repairing the low-level outlet of the dam.

• Removing sedimentation at the dam and stilling basin so that the low-level outlets are operable.

• Repairing/replacing the wall upstream of the dam outlet works to provide a trash rack and protection of the outlet works.

• Repair the dam outlet works gate.

• Repair the scour undermining the flume between the dam and the flume stilling basin.

• Repair the damaged sections of the flume wall and strengthening weak (slender) wall sections

• Remediating the undermined section of the spillway base slab and the lower spillway wingwall

The risk of damage from future extreme events (earthquakes and floods) is not included in the 25 year service life estimate. The utility advised that the structures withstood an extreme flood event caused by failure of a blocked bridge, and the 1976 magnitude 7.6 earthquake. Flood damage to the structures includes localized scour at the dam and under the flume (refer to Attachment C for details); these can be repaired. The risk of a flood causing irreparable damage is therefore judged to be low. There were no signs of earthquake damage, suggesting the original structure is capable of withstanding moderate seismic events.

Given the risk of extreme events occurring, some future repair work is anticipated to be required within the service life of the new mechanical and electrical equipment.

Recommended further study Some areas requiring further investigation that were unable to be included during the inspection are as follows:

• During construction, the upstream and downstream faces of the dam should be inspected for excessive deterioration or cracking. Ideally, this would occur after the low-level outlet was opened and sedimentation was cleaned from upstream of the dam to expose the upstream face of the dam. With the low-level drain in operation, flow over the dam should be minimal and the downstream face could also be inspected for deterioration or cracking.

• Periodic inspection and more detailed mapping of the scour hole downstream of the dam should be continued and mitigation measured enacted if the scour hole expands.

• Condition of the foundation of the flume downstream of STA 185m should be inspected. Access was not possible.

• Condition of the penstocks, where planned for re-use.

• Condition of the low level drains from the forebay structure to where they discharge into the spillway. Access was not possible due to sediment.

• Condition assessment of the hillside below the flume where the wall was damaged. Access to the hillside downslope of the flume was not possible.

• Condition of the hillside below the flume, where the spillway at STA 279m discharges. Access was not possible

• More information on the thickness and condition of the flume base slab should be collected when the flow is removed.

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Assessment of Geotechnical Considerations at and Above the Site The general geotechnical conditions at the site are good. The following observations were made during the site inspection:

• The dam foundation and abutments appears to be in good shape, except for the scour hole under the right side of the dam. However, this scour may be due to rock “plucking” out during large storms and may not progress any farther. Continued monitoring is recommended. Maintenance personnel noted a small landslide on the right abutment, but no damage or other issued were observed with this landslide.

• The flume and flume sediment trap in general were in good shape, except for the noted scour near the dam. However, the flume is located on very steep (greater than 1:1 slopes, see Figure 12) for much of its length, with small drainages crossing over and under the flume. There is the potential for future landslide activity to damage and/or fill the flume with sediments. It is recommended that human activities on the slope upstream of the dam be limited and that large scale clearing be limited to prevent runoff and erosion of the hillslope upslope of the flume. In addition, it appears as though the damaged wall section (STA 380-395) of the flume was due to a downslope landslide removing support for the wall and resulting in the wall failing. In repair of this wall, it is recommended that the slope conditions be carefully evaluated to minimize the potential for future landslide activity.

• The forebay appears to have slope erosion into it from the hillside above (Figure 8). It would be difficult to fully control this erosion, though several options are possible: 1) lay the slope back, however, this is difficult due to the length of the slope, 2) oversteepen the lower portion of the slope to provide a catch area for future erosion, which will require periodic maintenance to clear, or 3) stability through the use of shotcrete or managed vegetation growth. It is recommended that option 2 be implemented to minimize the erosion into the forebay. There was also erosion downstream of the forebay due to overtopping of the forebay in the past. It is recommended that during the repair of the facility, the capacity of the forebay be confirmed and that future overtopping prevented.

• Geotechnical concerns at other facilities were not observed during the site observations.

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Figure 12: Hillside above and below the flume

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Operational and Safety Considerations Findings and Recommendations

Figure 13: Photos of areas where care must be taken

Working at Heights, Fall Protection and Maintenance The water Canal/supply system requires extensive maintenance. There are multiple areas where the possibility of falling from heights exist. Consideration should be taken towards the Safety and Maintenance program of the canal/ water supply system. A Risk assessment should be done on the proposed system and proper installation for fall protection and arrest systems. These systems should take into consideration the established maintenance program and emergency response for personnel during unplanned maintenance activities.

Figure 14: Forebay

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Access Restriction and Guardrails General Warning Signs and Access restriction should be taken into consideration. The area is accessible to the public and some of the surrounding communities use the canal to channel water to their crops and farms, this is a safety concern to the community and uncontrolled or even unrestricted access could cause incidents which could have been prevent9ed if appropriate warning signs, guardrails, access restriction were put in place.

Previous provisions have been made for guardrails, but upon assessment it seems like substandard design of such barriers, lack of maintenance, change in weather conditions and seasonal water levels have not been taken in consideration.

The public, including children, frequent the project area. Their entry into project works or exposure to the hazards around the water conveyance features should be carefully managed. It is recommended that the forebay be secured by fencing.

In addition, all existing irrigation supply dams and taps that are currently routed in the flume must be removed. A new outlet should be placed at the forebay structure and a new supply pipeline installed across the existing footbridge for distribution to all irrigation systems across the river.

Figure 135: Inside the Powerhouse

Power Plant Access and Gantry Crane for Maintenance A portable Gantry system was utilized to perform the maintenance on the turbine within the building. Elevation conflicts with roof beams prevent its convenient use. It is recommended that a new system be designed to accommodate any future maintenance activities. In addition, appropriate access provisions should also be considered to the power plant.

Signs and Information in applicable Language When systems are installed, language and training should be taken in consideration, and when training is provided to employees this must be done in the language they conduct their work in. Furthermore, adequate provisions must be made with regard to fire fighting and response, warning signs and labels should be displayed in applicable language of employees.

24


Waste and Waste Management

Figure 16: Refuse in the river near the dam

Waste and pollution were observed along the river within the project limits. Training and awareness should be conducted with the community on required waste management and environmental control. This can be in the form of educational programs at the surrounding schools and through assistance with volunteering groups. Controlling the waste in the river will reduce the maintenance needed at the trash racks and other facilities.

25


Potential Hydropower Development On the basis of the foregoing assessments, the development of the hydropower potential of the site was evaluated. Turbine selection and sizing were developed in consultation with manufacturers on the basis of available flow and net head. These analyses yielded three alternative development schemes for consideration.

Project Operation and Unit Selection The optimization of development of a site’s hydropower potential is typically a complex process that balances several factors. This site exhibits a hydrograph of available flow that is quite typical, with a low level of flow that is present year-round, but which peaks for a short period of time at higher levels during a wet season.

A project’s benefit is proportional to the energy produced each year. A project’s cost is generally proportional to the generating and hydraulic capacity of the project works. A larger project can take advantage of higher flows, producing higher outputs, but if those higher flows are only present for a short period, a point of diminishing returns is reached. As a result, optimum project size tends to be that which is selected for flows that are present most of the year.

Other factors can influence sizing. For example, this site has the economic advantage that most of the civil works (dam, flume, forebay intake, and penstocks) are existing and serviceable. However, those existing facilities have a certain practical hydraulic capacity (about 1.58 m3/s). The existing Kubota turbine also appears to be capable of rehabilitation. The potential cost savings are essential to project feasibility.

In this case, project capacity cannot exceed the maximum flume capacity of 1.58 m3/s without an impractical level of investment. Further, it is likely that rehabilitation of the existing Kubota unit represents the lowest cost alternative for development. Under the estimated net head of 16.5 m, this unit would discharge approximately 0.6 m3/s. The hydrograph also suggests that, if feasible, the utilization of an additional 0.6 m3/s could be considered. The development of 1.2 m3/s of available flow would be well within the civil works’ capacity and represent an alternative that would significantly expand development of the site’s potential.

Development Alternatives On the basis of the forgoing considerations, three alternatives were selected for further evaluation:

Table 2: Alternative Summary DESCRIPTION RATIONALE

ALTERNATIVE 1 Rehabilitation of the existing Kubota pump-type turbine

Simplest and lowest cost with reasonable output

ALTERNATIVE 2 Replacement of the existing Kubota pump-type turbine with a new turbine

New equipment with Improved power output but higher cost

ALTERNATIVE 3 Rehabilitation of the existing Kubota turbine and addition of the new turbine

Combination of alternatives 1 and 2, representing an approach for combining their advantages and offering a path to developing the site in two steps

26


Two additional equipment alternatives were also investigated for the purpose of exploring possible options:

• The first consisted of a variant of Alternative 2, in which two smaller pump-type turbines would be installed. Two units were necessary because these off-the-shelf products are only offered in sizes up to about 250 lps in capacity. Such an approach would not fully utilize available flow and would require additional piping in the power plant.

• The second consisted of a true Francis turbine with adjustable wicket gates and the capability of operating from the minimum available flows, up to 1.2 m3/s. While such a unit offers the advantage of a single unit that can operate over the full available range of flow at higher efficiencies, its cost was twice that of Alternative 2 and would require a new larger penstock.

Features and highlights of each alternative are summarized below. Features common to all alternatives include:

• New dam low level drain

• Intake gate replacement

• Safety and access improvements

• Flume wall repair

• Sedimentation basin clean-out and repair

• Flume clean-out and other flume improvements and repairs

• Spillway improvements and repairs

• Forebay drain gate replacement

• Penstock gate replacement

• Power plant fencing

• Transformer pad improvements and repair

• Site grading

• Power plant wall and window improvements and repairs

• Power plant roof replacement

• Power plant hoist

• Power plant door replacement

• Power plant service water and drainage improvements

• Power plant electrical and lighting improvements

• Power plant grounding, power plant substation transformer and take-off structure, transmission line, and allowance for interconnection costs.

Alternative 1 – Rehabilitation of the existing Kubota pump-type turbine • Equipment type: Rehabilitated Kubota turbine with new belt drive, induction generator,

rehabilitated turbine inlet valve with new hydraulic actuator and HPU, protection and control panel with switchgear.

• Equipment rating: 64 kW, 600 lps, 16.5 m.

27


• Other major features: Reuse of existing penstock. Rehabilitation of turbine-generator will be performed in local shop and assumes that no major damage or defect is disclosed during its testing or inspection. Generator power factor will be corrected to 0.95 using switched capacitors.

• Advantages: Low cost and reasonable efficiency. Minimal structural/concrete modifications of the power plant building are anticipated.

• Disadvantages: Efficiency and output will be as determined by the existing equipment – no change or improvement is possible. Low cost is dependent upon finding of no major defect or damage in existing equipment.

Alternative 2 – Replacement of the existing Kubota pump-type turbine with a new turbine • Equipment type: New fixed-geometry Francis-type turbine (flow not adjustable by internal gates)

with new direct-drive induction generator, new turbine inlet valve and HPU, protection and control panel with switchgear.

• Equipment rating: 78 kW, 600 lps, 16.5 m.

• Other major features: Reuse of existing penstock. Manufacture of turbine will likely not be domestic. Generator power factor will be corrected to 0.95 using switched capacitors.

• Advantages: 20 percent higher guaranteed efficiency. Low risk of performance or installation issues.

• Disadvantages: Higher cost. Some structural/concrete modifications of the power plant building are required for equipment and draft tube installation.

Alternative 3 – Rehabilitation of the existing Kubota turbine and addition of the new turbine • Equipment type: Combination of rehabilitated existing and new equipment systems as

described above.

• Equipment rating: 64 and 78 kW, 600 lps and 600 lps, 16.5 m.

• Other major features: See above. Reuse of existing penstock for rehab unit. New penstock for new unit. Manufacture of new turbine will likely not be domestic. Generator power factor will be corrected to 0.95 using switched capacitors.

• Advantages: Utilization of up to 1.2 m3/s available flow. See above. Offers possible approach of staged development (Alternative 1 followed by Alternative 2).

• Disadvantages: Larger investment. Significant structural/concrete modifications of the power plant building are required for installation of the new equipment and draft tube at location of existing Drees unit.

Estimated Energy Production On the basis of the minimum available monthly flows (600 lps minimum assumed) and the estimated net head, monthly average power outputs were calculated for each unit or combination. Where available flow exceeded unit requirement, a constant output was employed. Where available flow for a given unit was less than the 600 lps rated flow, it has been assumed that each unit can be operated at less than rated flow by throttling of the inlet valve. Reduced output was estimated on the basis of turbine similarity law and the assumption that efficiency was constant. Monthly results were summed to provide average annual energy production figures for each alternative as follows:

• Alternative 1: 521,395 kWh



28


Estimated Cost The construction cost for each alternative was estimated on the basis of material and equipment quotations and labor/material estimates by local partners. The scope of work and level of effort for many items are very preliminary. A 10 percent allowance for engineering and administration costs was assumed. A 20 percent contingency was also added to the total cost. Cost estimate summaries and breakdowns are presented in Attachment E. Total estimated project development costs for each alternative are:

• Alternative 1: $180,140



29


Economic Evaluation A simple economic evaluation of the development alternatives, their costs, and their energy production was conducted. The results compare the alternatives on the basis of several measures, including net present value and simple payback period.

Methodology Preliminary costs for each alternative were estimated by the CH2M staff who conducted the field assessment. Costs included new or replacement equipment, repairs, and additions. These data are summarized in Attachment E.

On the basis of the generating equipment selected for each alternative, including turbine-generator performance and operating ranges, estimates of average annual energy production were developed. The incremental value of energy was applied to these results to produce the project benefits.

The results of the associated economic analysis are presented below:

Table 3: Key Financial Results

Alternative 1 Alternative 2 Alternative 3

Installed capacity (kW) 64 78 64 and 78

Total system cost $180,140 $673,952 $783,248

Annual energy production (kWh) 521,395 635,450 900,328

Year one revenue $51,715 $63,903 $90,654

Year one return 29% 9.5% 11.5%

30 year IRR (internal rate of return)

32% 12% 14%

30 year net profit $2,392,049 $2,507,088 $3,722,886

Net Present Value $1,164,015 $988,364 $1,571,540

Payback (years) 3.3 9.2 7.7

Further background information on the economic feasibility analysis can be found in Attachment F.

30

Attachment A Cost Analysis


The capital and operation cost estimates to refurbish the Joyabaj micro hydro scheme provided in this analysis are based on the site visits and inspections by the CH2M professionals. Major cost elements are divided into the following sections:

• Civil Works: For the different sections of the infrastructure major cost items have been identified for: Dam and Intake, Flume, Forebay and Penstock, Power Plant;

• Power Plant Refurbishment and Replacement: Mechanical and electrical works, refurbishment and replacement of the generating equipment, electrical transmission costs;

• Design Costs and contingency.

Once the major refurbishment and replacement items are identified under these headings, corresponding costs are estimated based on engineering judgment in collaboration with local partners. The cost estimates are identified for the three different options that have been put forward based on the technical feasibility as described in previous sections.

The majority of the cost is due to the turbine replacement in Option 2 and 3. Option 1 being the exception due to the lower refurbishment costs of the turbine. The rest of the costs (civil works, transmission, M&E and structural works) are comparable across the options.

Design cost and contingency are estimated as a fraction of the total cost and therefore proportional to the rest of the project costs.

Further details of the cost breakdown itemized for each and individual element can be found in Attachment E Cost Estimates.

A-1

Attachment B Hydrograph and Rainfall/Flow

Calculations


This appendix details the flow and rainfall analyses that were completed to project the annual hydrograph at the Joyabaj hydrodam site, a key factor of the feasibility study. The following data was available for the analysis.

• Monthly flow averages for 40 stations across Guatemala from May 2003 to April 2004.

• Monthly rainfall data at 40 gauges across the Guatemala from 1980 to 2015, with some sites having more complete data than others

• NASA Shuttle Rader Topography Mission (SRTM) data which provides global elevations at a resolution of 90 meters.

Figure 17 shows the rain gages and flow monitors in Guatemala, along with the Joyabaj hydrodam site location.

Figure 17. Guatemala Rain Gages and Flow Monitors

B-1


Flow Analysis Watershed areas were delineated for each flow meter and for the Joyabaj hydrodam site using an automated ArcGIS process on the SRTM raster elevation data. The resulting watersheds are shown in Figure 18.

Figure 18. Watersheds

To be thorough, the hydrographs for each meter, shown in Figure 19, were evaluated. Ultimately, the flow meters in the same larger watershed as the Joyabaj site, Flow Meters 11 and 17, were selected to use in projecting the annual flow at the hydrodam site due to similarities in geology and rain conditions. Figure 19 shows those hydrographs.

These hydrographs were normalized to the area of the Joyabaj hydrodam watershed (270 acres) and averaged, as shown in Figure 19 to estimate flow at the site.

B-2


Figure 19. Normalized Hydrographs and Joyabaj Projection

Rain Analysis Monthly rain data dated back to 1980 was available at several gage locations across the country. A theissen polygon analysis confirmed that the Chinque rain gage completely covers the Joyabaj hydrodam site watershed, as shown in Figure 20.

0

2

4

6

8

10

12

May-03 Jun-03 Aug-03 Sep-03 Nov-03 Jan-04 Feb-04

Flow

(m3/

sec)

Chiche (16) Puente Orellana (17) Joyabaj (100)

B-3


Figure 20. Thiessen Polygons

Gaps in the rainfall data at the Chinque gage were filled with data from the next nearest gage, Cubulco. Figure 21 shows the compiled annual rainfall totals from 1980 through 2015.

B-4


Figure 21. Rainfall Data

Figure 22 shows the estimated rainfall and flow at the Joyabaj hydrodam site from May 2003 through April 2004.

Figure 22. Estimated Joyabaj Rain and Flow

A relationship between flow and rainfall was developed from the estimated hydrograph, as shown in Figure 23.

0.0

20.0

40.0

60.0

80.0

100.0

120.0

Total Rainfall (in)

3.5 4.8 4.2 4.2

12.1

5.9 1.0 0.6 0.3 1.0 0.4 0.5

900

2921

43595168

9754

5896

1784886 639 526 456 451

0

9

18

27

36

450

3,000

6,000

9,000

12,000

15,000

May

-03

Jun-

03

Jul-0

3

Aug-

03

Sep-

03

Oct

-03

Nov

-03

Dec-

03

Jan-

04

Feb-

04

Mar

-04

Apr-

04

Flow

(m3/

sec)

Rain (in) River Flow (L/s)

B-5


Figure 23. Flow vs Rainfall

Figure 24 shows the monthly average flow projected from historical rainfall totals from the relationship above. Note that the flow monitoring period, May 2003 to April 2004, occurs during an extended period of lower than average rainfall totals. This may indicate that the flow projections is on the conservative side.

Figure 24. Projected Monthly Flow from 1980 through 2015

y = 0.0011x + 0.1277

0

2

4

6

8

10

12

14

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Rain

fall

(in)

Flow (L/s)

Composite Rainfall Chinque Rainfall Linear (Composite Rainfall)

010203040500

10,00020,00030,00040,00050,000

Jan-

80M

ay-8

1Se

p-82

Jan-

84M

ay-8

5Se

p-86

Jan-

88M

ay-8

9Se

p-90

Jan-

92M

ay-9

3Se

p-94

Jan-

96M

ay-9

7Se

p-98

Jan-

00M

ay-0

1Se

p-02

Jan-

04M

ay-0

5Se

p-06

Jan-

08M

ay-0

9Se

p-10

Jan-

12M

ay-1

3Se

p-14

Rain

fall

(in)

Flow

(L/s

)

Month

Rain (in) Flow (m3/s)

B-6


Table 4: Spillway flow capacity calculations

Method 1: Head loss approachpipe diameter =Pipe inlet invert level arbitary datum

Maximum upstream level (at capacity) = water level at top of headwall

Pipe bed slopePipe lengthoutlet invert = surveyed by contractor

Pass forward flow Goal seeky1 = y2 + (v2/2g) + hfwherey1 = upstream depthy2 = downstream depth =v = downstream velocity = free to discharge

hf = total head loss = hf1 + hf2 + hf3:

hf1 = inlet head loss = ki x (vav2/2g):

ki = loss coefficient = CIRIA C689 - Table A1.5

vav = inlet velocity = Q/A = Q=VA

hf1 =Inlet head losshf2 = head loss through culvert barrel = LE manning's equation

Energy slope, E = (nQ/AR2/3)2

L = culvert length = see above

n = manning's hydraulic roughnessA = culvert area =R = hydraulic mean radius = A/P =top term (nQ)

bottom term (AR2/3)Energy slope, E = (nQ/AR2/3)2Barrel head loss =hf3 = outlet head loss = K0{(vb2 - vd2)/2g}K0 = loss coefficient CIRIA C689 - Table A1.5

vb2 = velocity in culvert barrel =Vdc = velocity in channel downstream = free to discharge

Outlet head loss =Total head loss, hf =y1 =Corresponding upstream level =

Calculation self checked through comparison with alternative method.

Revision: 0 Project:

Hydropower feasibility assessment for Joyabaj, Guatemala

Verified by:

Calculation sheet

Calculation title: Forebay tank overflow spillway capacity check Created by: ABC Project code: 662747 Date: 24/02/2016 Serial no: /

ABC Sheet no:

m AOD

0.000 m/s

1.26 m3/s

99.5 m AOD

100 m AOD

12 1 in6 m

0.6 m

References/results

101

1 Date: 24/02/2016

0.300

CIRIA C689, Section 6.10

calculate0.600 m

6.000 m

4.459 m/s0.304 m0.304 m

Rev 1 (06/2012) BPG121_F01(Excel)

1.503 m101.003 m

0.000 m0.90 m

4.459 m/s4.459 m/s

0.599 m

0.75

0.0250.0800.100

CIRIA C689 - Table A1.2Average PE, smooth inner wall

0.283 m2

0.150 m

0.020

should equal top of inlet headwall

B-7


The calculations were completed in MS Excel

Method 2: Orifice equationAreaHeadCdFlow

Adopt smaller value for calculated spillway capacityFactor of safety adoptedDesign spillway capacity

1.21.01 m3/s

Project: Hydropower feasibility assessment for Joyabaj, Guatemala

Verified by:

Calculation sheet

Calculation title: Forebay tank overflow spillway capacity check Created by: ABC Project code: 662747 Date: 24/02/2016 Serial no: /

References/results

0.283 m2

1 m

2 Date: 24/02/2016 Revision: 0

ABC Sheet no:

Rev 1 (06/2012) BPG121_F01(Excel)

1.21 m3/s

0.971.21421 m3/s

B-8

Attachment C: Civil Works - List of Defects and Recommended

Remedial Work


List of defects and recommended remedial work Table 5: Remediation Work

Defect Possible remedial work

1 Scour hole downstream of the dam Monitor

2 Sedimentation of the reservoir pool Remove as much sediment as feasible.

3 Low-level outlet Replace with new gate valve

4 Access to low-level outlet Provide small boat or removable walkway for access

5 Upstream training wall/trash rack wall

Replaced with wall and trash rack to minimize damage and clogging of the outlet works

6 Inoperable gate valves at outlet

Replaced with new gate valve, preferably on upstream face of the dam.

Table 6: Flume Defect listing


1 18 no. concrete planks severely spalled, rebar exposed.

Various locations

Plank replacement. The planks provide pedestrian access and provide bracing across the top of the channel walls, the new planks require to extend down the side of the wall.

2 Left bank channel has accumulated approximately 200mm thick layer of vegetated soil. Excavate soil to clean off left bank wall.

3 Upper 500mm section of wall has sheared off for approximately 15m, at STA 380-395.

New section of channel wall constructed from unreinforced cyclopean concrete, with additional concrete planks to provide bracing across top of walls.

4 Upper 500mm section of wall sheared off for approximately 4m, at STA 4-8m.

New section of channel wall constructed from unreinforced cyclopean concrete, with existing columns extended up to provide lateral strength.

5

Scour from river has undermined flume over approximately 22m length. STA 23-45m.

New wall constructed underneath flume where currently undermined. Additionally, new support columns at 5m centers founded on excavated rock. Both constructed from unreinforced cyclopean concrete.

6 6 No. support columns undermined. STA 90-105m, 140-150m Infill to base of columns with mass concrete.

7 12 no. cracked sections of channel wall. Various locations. Cement mortar used to repair cracks

8 Sediment basin located at STA 40-57m requires its silt emptying. Excavate silt out.

9 2 sediment trap gates seized 2 new gates

C-1


Table 6: Flume Defect listing


10 Channel has accumulated silt, stones and large rocks, some placed deliberately by local community to extract water for irrigation purposes. Clean out channel

11 No edge protection against falls in very exposed location: STA 95-110m, 220-250m

Bolt steel angles to channel wall at regular centers with cable running between.

12 flume wall is notably slender (2 approx. 125mm thick), some leakage observed. STA 125-135m, 140-145m, 155-165m, 170-178m.

Additional concrete planks constructed in these locations to provide bracing between channel walls.

13 Hillside stream spillway training walls spalled, rebar exposed. Break back concrete and re-cast.

Forebay structure • The two low level drain gates require replacing

• Silt that has accumulated in the bottom of the structures requires excavating

• The slope above the forebay structure occasionally sheds material and is unstable. This needs to be prevented to avoid the material being carried into the turbine. Of three possible options discussed in the Civil Works Assessment section of the report, it is recommended to oversteepen the lower portion of the slope to provide a catch area for future erosion. This will require periodic maintenance to clear.

Forebay Spillway • The lower spillway wingwall requires repair work and strengthening. This will involve breaking back

the cracked section and reconstructing, infilling voids created for the irrigation pipes, and constructing new columns behind the wall.

• A section of the spillway channel base slab has been undermined. This requires breaking out and backfilling with mass concrete.

• For the spillway to operate safely it must be able to pass the maximum inflow from the flume. The capacity is dictated by the 600mm diameter pipe; which can convey a maximum of approximately 1.0m3/s (Refer to spillway flow capacity calculation in Attachment B). Given the flow capacity of the channel is close to 2000 L/s and there is no feasible method of restricting inflows into the channel during a flood situation, it is suggested a side weir and spillway chute should be constructed in the flume wall at some location upstream of where it discharges into the forebay. This will limit the spillway flow to a safe value, and is likely to be a cheaper and more logistically feasible option than replacing the spillway pipe or reconfiguring the spillway on the steep hillside to increase flow capacity.

Note the flow does not need to be reduced below the 900l/s flow required by Alternative 2 Since alternative 3 requires 1200l/s combined flow, additional works to increase the spillway capacity would be required if this alternative is taken forward.

C-2


Penstocks • The joint seals should be tested under pressure and may need replacing

• A protective coat of paint is recommended to maximize the residual life of the structure

• The lower thrust block has a crack which requires repairing

• The original penstock was found to be in poor condition and would require to be replaced if a two turbine arrangement is proposed.

Powerhouse • Sections of internal and external wall require re-rendering

• Walls repainted

• 5 new windows (note the existing grills are in good condition)

• A new roof is recommended, timber structure and corrugated iron or other locally available product would be suitable. This should be configured to allow access for a portable crane for moving heavy equipment.

• A new door through the riverside wall would provide additional convenient access for operators

• Replacement of the existing main door to improve access and security

• Regrading around the building to improve drainage and vehicle entrance access

Tailraces Newer tailrace: • Void in the left bank wall to be infilled with concrete

• Scoured out backfill behind the right bank wall to be infilled with granular material.

• There was a small flow through the new tailrace, and a weep hole in the right bank wall was operational. Given the lack of rain at the time of the inspection it is likely the flow originates from the forebay structure. This requires further investigation to establish its source.

Original tailrace: • If a twin turbine system is adopted, this will require its left bank wall reconstructing, dimensions

approximately 6m long by 1m high.

C-3

Attachment D: Miscellaneous Site Data


Table 7: Flume Walkover Survey Record

STA (m) Comment

0 flume intake from dam

4 Upper section of wall sheared off START

8 Upper section of wall sheared off END

23 Scour underneath flume START

32.5 Column providing support to flume

45 Scour underneath flume END

40 Sediment trap (Stilling basin) START

48 650x650mm Gate outlet to sediment structure discharges underneath flume

54 650x650mm Gate outlet to sediment trap discharges underneath flume

57 Sediment trap END

80 Flume raised on columns START

85 Planks across top of flume START

90 Column formations partly undermined

95 Edge of flume is very exposed and would benefit from edge protection START

111 Soffit slab over flume START

111 Edge of flume is very exposed and would benefit from edge protection END

115 Soffit slab over flume END

115 Flume raised on columns END

125 Planks across top of flume END

125 Right bank wall leaking, has no riverside resistance and appears slender START

135 Right bank wall leaking, has no riverside resistance and appears slender END

140 Flume raised on columns START

140 Right bank wall has no riverside resistance and appears slender START

144 Right bank wall has no riverside resistance and appears slender END


155 Flume raised on columns END






183 Stream spillway across top of flume

D-1


Table 7: Flume Walkover Survey Record

STA (m) Comment



220 Edge of flume is very exposed and would benefit from edge protection START


250 Planks across top of flume END

250 Edge of flume is very exposed and would benefit from edge protection END

285 Stream spillway across top of flume (looks to operate frequently)

299 Stream spillway across top of flume in poor condition


380 Right bank wall sheared off START

395 Right bank wall sheared off END

D-2


Figure 24: Powerhouse Plan Sketch

D-3

Attachment E: Cost Estimates


This section provides the cost breakdown of each development alternative:


• Alternative 2 – Replacement of an existing Kubota pump-type turbine with a new turbine

• Alternative 3 – Rehabilitation of the existing Kubota turbine and replacement of the other turbine

Table 5. Alternative 1 – Rehabilitation of Existing Turbine

CIVIL WORKS - DAM AND INTAKE

Item (Major cost elements) Unit Unit Cost Quantity Total Development Cost

Replace low level drain

Intake gate replacement

Repair the training wall and trash rack

Safety improvements: ladder, railing, platform

Path/trail improvements

LS

LS

LS

LS

LS

$1,000

$1,000

$2,000

$200

$200

1

1

1

1

1

$1,000

$1,000

$2,000

$200

$200

SUBTOTAL - DAM AND INTAKE $ 4,400

CIVIL WORKS - FLUME


Wall replacement STA 380 to 395

Wall repair STA 4 to 8 (near the dam)

Wall strengthing

Repair scour STA 23 to 45 under flume

Clean the sedimentation trap

Sedimentation gate replacement (two)

Repair/Replace Cover planking

Crack Repair

Safety railing STA 95-111, 220-250

Repair of undermined columns STA 89 to 105 and STA 140 to 150

Clean flume of debris (rocks, etc.)

Clean left bank

Repair sediment trap outlet

Repair flume stream crossing

UC

UC

LS

LS

LS

UC

UC

LS

LS

UC

UC

UC

LS

LS

$1,000

$500

$40

$9,000

$300

$600

$40

$20

$200

$500

$300

$360

$200

$300

1

1

60

1

1

2

18

12

1

6

1

1

1

1

$1,000

$500

$2,400

$9,000

$300

$1,200

$720

$240

$200

$3,000

$300

$360

$200

$300

SUBTOTAL - FLUME $19,720

CIVIL WORKS - FOREBAY AND PENSTOCK


Forebay spillway end wall remedial

Remediate undermined section of spillway

Low level drain gate replacement

New gate for existing penstock

New gate for new penstock

LS

LS

LS

LS

LS

$1,000

$1,000

$700

$600

$600

1

1

2

1

0

$1,000

$1,000

$1,400

$600

$0

SUBTOTAL - FOREBAY AND PENSTOCK $ 4,000

E-1


POWER PLANT - SITE/CIVIL


Access roadway grading and site grading

New fencing

Substation transformer pad/containment

Open pit toilet

LS

LS

LS

LS

$2,000

$800

$1,000

$250

1

1

1

1

$2,000

$800

$1,000

$250

SUBTOTAL - SITE/CIVIL $4,050

POWER PLANT - STRUCTURAL/ARCHITECTURAL


Repair defective plaster/mortar

New windows

New door to existing opening

New paint

New roof

New crane system

LS

LS

LS

LS

LS

LS

$300

$200

$500

$300

$1,500

$1,000

1

5

1

1

1

1

$300

$1,000

$500

$300

$1,500

$1,000

SUBTOTAL - STRUCTURAL/ARCHITECTURAL $4,600

POWER PLANT - MECHANICAL


Turbine service water and drainage - seal water, drains

Turbine inlet valve refurbishment and actuator

LS

LS

$500

$3,000

1

1

$500

$3,000

SUBTOTAL - MECHANICAL $3,500

POWER PLANT - ELECTRICAL


Main service disconnect

Building services transformer and panelboard

Lighting

Miscellaneous - convenience receptacles

Conductors and conduit

Grounding

LS

LS

LS

LS

LS

LS

$ 700

$ 1,500

$ 400

$ 100

$ 3,500

$ 500

1

1

1

1

1

1

$ 700

$ 1,500

$ 400

$ 100

$ 3,500

$ 500

Pole mounted transformer with riser, fused cutouts and lightening arresters

LS $ 12,000 1 $ 12,000

E-2


SUBTOTAL - ELECTRICAL $ 18,700

GENERATING EQUIPMENT


Turbine removal, testing, and repair

New Belt Drive System

New Generator

Generator Control Panel and HPU

Remote Monitoring Capability

Manufacturer's services

LS

LS

LS

LS

LS

LS

$ 4,750

$ 2,750

$ 9,000

$ 25,000

$ 5,000

$ 1,000

1

1

1

1

1

1

$ 4,750

$ 2,750

$ 9,000

$ 25,000

$ 5,000

$ 1,000

SUBTOTAL - GENERATING EQUIPMENT $ 47,500

ELECTRICAL TRANSMISSION


Lands and ROW

Interconnection facilities

Transmission line - 13.2 kv

LS

LS

LS

$ -

$ 10,000

$ 20,000

1

1

1

$ -

$ 10,000

$ 20,000

SUBTOTAL - ELECTRICAL TRANSMISSION $ 30,000

GENERAL COST


Subtotal of all categories

Design cost

Contingency

LS

LS

LS

NA

NA

NA

1

1

1

$ 136,470

$ 13,647

$ 30,023

TOTAL - PROJECT DEVELOPMENT COST $ 180,140

E-3


Table 6. Alternative 2 - Replacement of One Turbine








LS

LS

LS

LS

LS

$1,000

$1,000

$2,000

$200

$200

1

1

1

1

1

$1,000

$1,000

$2,000

$200

$200

SUBTOTAL - DAM AND INTAKE $4,400

CIVIL WORKS - FLUME




Wall strengthening





Crack Repair




Clean left bank



UC

UC

LS

LS

LS

UC

UC

LS

LS

UC

UC

UC

LS

LS

$1,000

$500

$40

$9,000

$300

$600

$40

$20

$200

$500

$300

$360

$200

$300

1

1

60

1

1

2

18

12

1

6

1

1

1

1

$1,000

$500

$2,400

$9,000

$300

$1,200

$720

$240

$200

$3,000

$300

$360

$200

$300


CIVIL WORKS - FOREBAY AND PENSTOCK INTAKE





LS

LS

LS

$1,000

$1,000

$700

1

1

2

$1,000

$1,000

$1,400



LS

LS

$600

$600

1

1

$600

$600

SUBTOTAL - FOREBAY AND PENSTOCK INTAKE $4,600




New fencing


Open pit toilet

LS

LS

LS

LS

$2,000

$800

$1,000

$250

1

1

1

1

$2,000

$800

$1,000

$250

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New windows


New paint

New roof

New crane system

LS

LS

LS

LS

LS

LS

$300

$200

$500

$300

$1,500

$1,000

1

5

1

1

1

1

$300

$1,000

$500

$300

$1,500

$1,000

Concrete Structure Changes for new Turbine LS $5,000 1 $5,000





Turbine inlet valve and actuator - Included with new Turbine

LS

LS

$500

$0

1

1

$500

$0

SUBTOTAL - MECHANICAL $500





Lighting

LS

LS

LS

$700

$1,500

$400

1

1

1

$700

$1,500

$400



Grounding


LS

LS

LS

LS

$100

$3,500

$500

$12,000

1

1

1

1

$100

$3,500

$500

$12,000

SUBTOTAL - ELECTRICAL $18,700

GENERATING EQUIPMENT - NEW UNIT


Turbine/Generator/HPU/Control Panel/Turbine Inlet Valve- New



LS

LS

LS

$389,000

$5,000

$25,000

1

1

1

$389,000

$5,000

$25,000

SUBTOTAL - GENERATING EQUIPMENT $419,000

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Lands and ROW



LS

LS

LS

$0

$10,000

$20,000

1

1

1

$0

$10,000

$20,000

SUBTOTAL - ELECTRICAL TRANSMISSION $30,000

GENERAL COST



Design cost

Contingency

LS

LS

LS

NA

NA

NA

1

1

1

$510,570

$51,057

$112,325

TOTAL - PROJECT DEVELOPMENT COST $673,952

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Table 7. Alternative 3 – Rehabilitation of Existing Turbine Combined with Replacement of the Other Turbine








LS

LS

LS

LS

LS

$1,000

$1,000

$2,000

$200

$200

1

1

1

1

1

$1,000

$1,000

$2,000

$200

$200

SUBTOTAL - DAM AND INTAKE $4,400

CIVIL WORKS - FLUME




Wall strengthening





Crack Repair


UC

UC

LS

LS

LS

UC

UC

LS

LS

$1,000

$500

$40

$9,000

$300

$600

$40

$20

$200

1

1

60

1

1

2

18

12

1

$1,000

$500

$2,400

$9,000

$300

$1,200

$720

$240

$200



Clean left bank



UC

UC

UC

LS

LS

$500

$300

$360

$200

$300

6

1

1

1

1

$3,000

$300

$360

$200

$300


CIVIL WORKS - FOREBAY AND PENSTOCK INTAKE







New penstock pipe

LS

LS

LS

LS

LS

LS

$1,000

$1,000

$700

$600

$600

$10,000

1

1

2

1

1

1

$1,000

$1,000

$1,400

$600

$600

$10,000

SUBTOTAL - FOREBAY AND PENSTOCK INTAKE $14,600

E-7





New fencing


LS

LS

LS

$2,000

$800

$1,000

1

1

1

$2,000

$800

$1,000

Open pit toilet

Vehicle access over tailrace

Old tailrace new wall

LS

LS

LS

$250

$1,000

$2,500

1

1

1

$250

$1,000

$2,500





New windows


New paint

New roof

New crane system

New door to access second turbine

LS

LS

LS

LS

LS

LS

LS

$300

$200

$500

$300

$1,500

$1,000

$1,000

1

5

1

1

1

1

1

$300

$1,000

$500

$300

$1,500

$1,000

$1,000

New Concrete Structural for New Turbine LS $7,000 1 $7,000





Turbine inlet valve refurbishment and actuator

LS

LS

$500

$3,000

1

1

$500

$3,000

SUBTOTAL - MECHANICAL $3,500





Lighting



Grounding


LS

LS

LS

LS

LS

LS

LS

$700

$1,500

$400

$100

$5,000

$500

$25,000

2

1

1

1

2

2

1

$1,400

$1,500

$400

$100

$5,000

$1,000

$25,000

SUBTOTAL - ELECTRICAL $34,500

E-8


GENERATING EQUIPMENT - REFURBISHMENT + NEW UNIT


Turbine/Generator/HPU/Control Panel/Turbine Inlet Valve- New

Original Turbine removal, testing, and repair

New Belt Drive System

New Generator

Generator Control Panel and HPU



LS

LS

LS

LS

LS

LS

LS

$389,000

$4,750

$2,750

$9,000

$25,000

$5,000

$26,000

1

1

1

1

1

2

1

$389,000

$4,750

$2,750

$9,000

$25,000

$10,000

$26,000

SUBTOTAL - GENERATING EQUIPMENT $466,500



Lands and ROW



LS

LS

LS

$0

$10,000

$20,000

1

1

1

$0

$10,000

$20,000

SUBTOTAL - ELECTRICAL TRANSMISSION $30,000

GENERAL COST



Design cost

Contingency

LS

LS

LS

NA

NA

NA

1

1

1

$593,370

$59,337

$130,541

TOTAL - PROJECT DEVELOPMENT COST $ 783,248

E-9

Attachment F: Basic Economic-Feasibility Evaluation


An economic analysis has been carried out for the Joyabaj Hydro Scheme. This takes account of the the capital and operational costs, and the revenues generated by electricity produced by the hydro turbine. Al three options have been assessed individually and the results are shown below in the table.

Table 3: Key Financial Results

Alternative 1 Alternative 2 Alternative 3

Installed capacity (kW) 64 78 64 and 78

Total system cost $180,140 $673,952 $783,248

Annual energy production (kWh) 521,395 635,450 900,328

Year one revenue $51,715 $63,903 $90,654

Year one return 29% 9.5% 11.5%

30 year IRR (internal rate of return)

32% 12% 14%

30 year net profit $2,392,049 $2,507,088 $3,722,886

Net Present Value $1,164,015 $988,364 $1,571,540

Payback (years) 3.3 9.2 7.7

As can be seen from the table above, Option 1 has the least capital expenditure and also the most financially viable of all options with a payback term of 4 years and the highest rates of return.

Option 2 and 3 closer in financial results with regards to the returns and the payback. Whilst Option 3 is the most expensive of all (in capital costs), Option 2 has the highest payback term of 9.2 years.

As described in cost analysis section, this is due to the relatively lost cost of the turbine refurbishment as opposed to replacement when the rest of the infrastructure costs remain comparable. Further to this, the revenues generated by the turbines are limited by the flow available throughout the year. This results in reduced utilization of Option 3 turbines when compared to Option 1 and 2.

However, when examined across the lifespan of the scheme all options yield to a sizeable profit. The net profit due to the revenues generated by electricity production vary from $2.3M to $3.7M across the options.

It needs to be noted that the financial analysis is based upon an assumption that wholesale rates from INDE will increase at an annual rate of 3% per year. Recent rate adjustments make the process of developing a trendline very difficult. If the wholesale rates are higher than 3%, and thus more costs are offset, the economic viability will be greater.

Evaluation of the Scheme in the Context of Sustainable Development Beyond the technical and economic feasibility of the scheme, there are some further considerations with regards to sustainability credentials of the scheme and its impact on the Joyabaj region overall.

In the context of sustainable development, environmental and social-economic aspects of the scheme are discussed below:

Environmental: Joyabaj micro Hydro scheme provides renewable electricity without causing any harmful CO2 emissions. Furthermore, there are no other emissions (i.e. NOx, particulates etc) associated with the scheme. Therefore, the proposed project is effectively “zero carbon” and emission free. The CO2 emission savings from offsetting the grid electricity result in 274 tonnes of CO2 savings per annum. Over the life time of the development this equates to more than 8,200 tonnes of savings.

F-1


In addition to this, due to minimal infrastructure work required to refurbish the scheme, there will be negligible impact on the environment during the refurbishment, and almost no “embedded emissions” attributed to the construction works.

Therefore, unlike some other infrastructure schemes, benefits stated in this study would not result in a “hidden” environmental cost in any way.

Key Financial Results

Option 1 Option 2 Option 3

Installed capacity 64 78 64 & 78

Cost/tonne CO2 saved (capital)

$40 $77 $72

Cost/tonne CO2 saved (lifecycle)

-$177 -$146 -$150

Fuel/Energy resilience: The scheme would add small but a meaningful contribution to the energy generation profile of the region. Diversifying energy production by adding a local renewable scheme would increase the fuel security of the region

Employment, and increasing technical expertise: The project will bring in expertise in operating a micro scale hydro turbine to Joyabaj. It will create employment, increase the acceptance and uptake of such schemes in Guatemala.

Economic Benefits: Significant financial benefits are projected in this study. The revenues generated by the scheme can be used elsewhere in the region in areas where funding is needed, further improving the wellbeing of the region.

Assumptions It is assumed that lifespan of the system is 30 years.

Electricity price data is based on the utility bills provided by the municipality, increased by 3 percent yearly.

Total $/kWh

Electricity Price - social 0.088

Electricity Price - non social 0.109

Electricity Price - regular - average (social and nonsocial) 0.094

Total $/100 kW

Electricity Price - peak demand - social 8.848

Electricity Price - peak demand - non social 9.968

Electricity Price - peak (social and nonsocial) 9.240

2015

kgCO2/kWh

From http://ecometrica.com/assets/Electricity-specific-emission-factors-for-grid-electricity.pdf

F-2


Total $/kWh

Grid supplied electricity 0.341

Financial Parameters CPI 3% from https://www.focus-economics.com/country-

indicator/guatemala/inflation

discount rate 4% Widely accepted figure

Additional Costs design cost 10% Based on internal discussions

contingency 20% Based on internal discussions

F-3


Key Input Figures ENERGY

GENERATION

System size kWp 64 78 64 and 78

Annual Yield in kWh 521,395 635,450 900,328

Capital Cost

Civil Works - Dam And Intake $4,400.00 $4,400.00 $4,400.00

Civil Works - Flume $19,720.00 $19,720.00 $19,720.00

Civil Works - Forebay And Penstock Intake $4,000.00 $4,600.00 $14,600.00

Civil Works - Penstock $0.00 $0.00 $0.00

Power Plant - Site/Civil $4,050.00 $4,050.00 $7,550.00

Power Plant - Structural/Architectural $4,600.00 $9,600.00 $12,600.00

Power Plant - Mechanical $3,500.00 $500.00 $3,500.00

Power Plant - Electrical $18,700.00 $18,700.00 $34,500.00

Generating Equipment - Refurb $47,500.00 $419,000.00 $466,500.00

Electrical Transmission $30,000.00 $30,000.00 $30,000.00

Design Cost And Contingency $43,670.40 $163,382.40 $189,878.40

Project Administration Cost $0.00 $0.00 $0.00

Total Cost $180,140 $673,952 $783,248

Operational Cost

Maintenance, insurance, admin/Total pa 5,000 5,000 7,500

Replacement gear (% of initial capital) 1,000 1,000 2,000

other maintenance costs ─ ─ ─

Revenue

Electricity Tariff (offsetting peak demand) $/100 kWp 9.24 9.24 9.24

Electricity Tariff (regular - social and nonsocial - demand) $/kWh 0.09 0.09 0.09

Value of excess electricity sold (export) ─ ─ ─

% generation within the municipality/community 1.0 1.0 1.0

Other Info

System Install Year 2018 2018 2018

Discount Rate 0.04 0.04 0.04

other data

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Hydropower Feasibility Assessment for the Town of Joyabaj ... · hydropower feasibility assessment...

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