Power Plant Construction - World Bank



ENVIRONMENTAL IMPACT ASSESSMENT

E1062-

Project Description

All three of the proposed projects (Leon, Guadalajara, and Monterrey II) involve the collection and combustion of landfill gas (LFG). LFG is comprised of approximately 50 percent methane and 50 percent carbon dioxide. Leon will combust the collected LFG in a flare. The Guadalajara and Monterrey II projects will use the collected LFG to fuel engine generators to produce electricity. Both processes destroy methane by converting it to carbon dioxide and water.

Overall, the installation and operation of a LFG collection and control system will significantly improve the environment. The primary environmental benefit is the collection and destruction of volatile organic compounds (VOCs) and methane. VOCs contribute to low level ozone formation (a precursor to smog) and methane is a potent greenhouse gas. The secondary emissions of nitrogen oxides (another smog forming compound) and carbon monoxide by the flare will be more than offset by the destruction of VOCs. In addition to emissions reductions, LFG collection will control and reduce odors and subsurface methane migration.

This projects will consist of the installation of a comprehensive LFG collection and control system at the Landfills. No project facilities will be constructed off site and no rights of way or easement are required for these projects. The major components of the LFG collection and control system to be constructed at the Landfill are as follows:

• LFG extraction wells,

• LFG collection piping,

• A blower flare station (Leon)

• LFG –fueled power plant (Guadalajara and Monterrey II).

LFG Extraction Wells

LFG extraction wells will be constructed with a 4 or 6-inch diameter PVC or HDPE pipe centered inside a boring. Well borings in waste are typically drilled between 12 and 36 inches in diameter depending on equipment availability and cost constraints. Well depths will vary according to the waste depth and will typically be installed to ¾ of that depth depending on liquid (leachate) levels within the waste mass. The well borings will be backfilled using a permeable media such as washed stone, crushed glass, or crushed concrete (sized to avoid penetration or blocking of the well perforations), a bentonite (or similar) seal, and soil. The length of slotted pipe generally will be two-thirds the well depth, although it may be increased at deeper wells to avoid installation of long sections of solid pipe.

Each LFG extraction well will include a wellhead that will include a valve to control LFG flow and vacuum and monitoring ports on either side of the valve to measure LFG quality, pressure, and temperature.

The LFG extraction wells will be constructed using drill rigs capable of drilling through waste. Other standard construction equipment, including dump trucks and backhoes, will be used to construct the LFG extraction wells.

Landfill Gas Collection Piping

The LFG piping will be constructed with 4-inch up to 18-inch diameter HDPE pipe typically installed above grade. The piping network will convey LFG from the LFG extraction wells to the blower/flare station where it will be flared.

HDPE piping is heat fused together and no solvent or glues are used.

Blower/Flare Station(Leon)

The LFG collected at the Leon site will be routed to a flare system that will be designed and operated to achieve a high destruction efficiency of methane and VOCs with no visible emissions. The control system will operate at all times when LFG is routed to the system. The control device is proposed to be an open flare (also referred to as a “utility” or “candle” flare).

Power Plant

The LFG collected at the Guadalajara and Monterrey II sites will be routed to a series of engine generators (each capable of producing approximately 1 MW of electricity). Combustion of LFG in the engines provides a high destruction efficiency of methane and VOCs.

Description of the Environment

The projects will take place entirely on closed landfills. The current, or baseline, condition of the environment is typical of closed landfills each containing multiple millions of tons of solid waste. Without a comprehensive LFG collection and control system, greenhouse gas emissions from the landfill are substantial. In addition the potential for subsurface methane gas migrating from the landfills exists.

At the Leon Landfill, leachate seeps are common and these have the potential to impact surface water.

Legislative and Regulatory Considerations

The regulations of the GOM applicable these types of projects were summarized in the Environmental Impact Statement (June 2002) prepared by SIMEPRODESO for the Monterrey I project. These regulations apply to air emissions, electrical substation planning and design, noise levels, landfill design and related projects, power plant installations, testing and security for electric installations, and natural gas use.

Presented below is an excerpt (in Spanish) from the above referenced report:

Normas Oficiales Mexicanas, Normas Mexicanas, Normas de Referencia y acuerdos normativos.

En materia de normas oficiales mexicanas, sobresalen las siguientes:

La NOM-085-ECOL-1994, la cual regula las zonas y por capacidad, los niveles máximos permisibles de emisión a la atmósfera de humos, partículas totales, bióxido de azufre y óxidos de nitrógeno provenientes de equipos de combustión de fuentes fijas que utilizan combustibles sólidos, líquidos o gaseosos.

La NOM-113-ECOL-1998, que establece las especificaciones de protección ambiental para la planeación, diseño, construcción, operación y mantenimiento de subestaciones eléctricas de potencia o de distribución que se pretendan ubicar en áreas urbanas, suburbanas, rurales, agropecuarias, industriales, de equipamiento urbano o de servicios y turísticas; y es de observancia obligatoria para las empresas responsables de dichas actividades.

La NOM-081-ECOL-1994, que establece los límites máximos permisibles de emisión de ruido de las fuentes fijas y su método de medición.

El Proyecto de norma NOM-084-ECOL-1994, que establece los requisitos para el diseño de un relleno sanitario y la construcción de sus obras complementarias.

La NOM-001-SEMP-1994, relativa a instalaciones destinadas al suministro y uso de la energía eléctrica.

La NOM-EM-002-SCFI, relativa a productos eléctricos, conductores, alambres y cables, especificaciones de seguridad y métodos de prueba.

La NOM-002-SECRE-1997 sobre las instalaciones de aprovechamiento para gas natural.

Normas Grupo Gas Natural, como:

NT-700-GN, que establece criterios técnicos para la inspección periódica de instalaciones receptoras de gas en locales destinados a usos domésticos, colectivos o comerciales y la NT-701-GN (Rev 1), que establece criterios Técnicos para la revisión periódica de instalaciones receptoras de gas en locales destinados a usos domésticos, colectivos o comerciales, La NOM-002-SECRE-1997 sobre instalaciones de aprovechamiento para gas natural.

Potential Impacts of the Proposed Projects

As stated above, the installation and operation of a LFG collection and control systems (flare or engine generators) at the Landfills will significantly improve the environment compared to the baseline condition, including a reduction of air emissions. In addition, once the projects are complete, proposed environmental remediation measures should reduce the leachate seeps and overall quantity at Guadalajara and Leon. Reducing the number of leachate seeps and reducing air emissions at the sites will enable potential other end uses on the Leon landfill, such as recreational uses (i.e., athletic fields).

During the construction and installation of the projects, potential environmental impacts could arise. Examples of potential impacts include:

• Noise during construction,

• Emissions from construction vehicles and equipment,

• Spilled fuel, engine oil, and lubricant during re-fueling and maintenance activities to support construction vehicles and equipment,

• Excavated MSW derived from drilling LFG extraction wells,

• Air emissions from LFG extraction well boreholes prior to the wells being completed, and

• Distressed vegetation is the vicinity of the LFG extraction wells.

To minimize the environmental impacts from the above items the following will be performed:

• Good housekeeping measures will be followed during vehicle and equipment maintenance and re-fueling activities. Spills or leaks of petroleum liquids will be quickly contained and cleaned.

• Excavated MSW derived from drilling LFG extraction wells will be relocated on the landfill and covered with soil to minimize odors and control vectors.

• LFG extraction wells will not be left open (i.e., unfinished) overnight unless the borehole is covered to protect air emissions.

• If significant disturbance of the landfill’s vegetative cover occurs during construction, the disturbed areas will be re-vegetated.

Power Plant Construction – Monterrey II and Guadalajara

Construction of the power plant involves the following primary activities:

1. Site clearing and grading.

2. Concrete foundations for engine generator skids; blower and flare equipment; administration building; new oil, waste oil, and spent antifreeze storage tanks and containment area; and transformers.

3. Utilities installation, including water supply, electrical, telephone, and sewer (optional).

4. Equipment installation, including blowers, flare, engine generators, condensate sump/pump.

5. Piping, including landfill gas supply to blower inlets; piping between blowers and flare or engine generators; condensate piping; engine oil piping.

6. Auxiliary lighting, fencing, parking area, signage, etc.

The potential environmental impact for each of these installations is discussed below:

1. Site clearing and grading at a landfill facility is likely to encounter buried refuse (even if none was reportedly buried in the construction area). Such waste must be excavated to provide a competent foundation for the equipment. Excavated waste must be handled appropriately to minimize potential environmental impacts. Appropriate measures include removing the refuse daily and placing it in the landfill or disposing of it offsite. Grading also can increase particulate (dust) emissions during such activities, but not to a degree or duration that warrants control.

2. Construction of concrete foundations and footings may require some additional excavation beyond the clearing and grading, but no environmental impacts are anticipated.

3. Utility installation will involve trenching for utility lines. At this time, it is undetermined as to how far or from what direction the utilities will be brought to the site. The developer will be responsible for complying with applicable regulations that govern such activities.

4. The engine generators themselves will be shipped in containers with all the mechanical, electrical, and equipment components pre-assembled. Thus, the actual installation requirements for these units is generally limited to: unloading the equipment from a flatbed truck and setting it on the prepared foundations; connection of the landfill gas piping from the compressors to the fuel supply piping for the engines; and electrical wiring. Similarly, the blower and flare equipment is anticipated to be pre-assembled and delivered to the site on a skid. Commissioning of the engines will involve oil and lubricant handling and appropriate measure to prevent or contain spills is necessary. The oil tanks, for example will be located within a containment compound to prevent it from impacting the environment if a leak or spill should occur.

5. Piping within the power plant compound will be primarily high density polyethylene (HDPE) and steel. Steel piping is welded or flanged; HDPE is joined by butt fusion (a thermal process) or electro-fusion. None of these processes poses a significant threat to the environment as no solvents are used and mishaps would not involve spills or other potential harm.

6. The installation of lighting, fencing, parking areas, and signage are not anticipated to have any negative environmental impacts.

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