Category: Hydraulic, Sanitation and Waterworks


 

 

 

 

 

 

 

YACYRETA HYDROELECTRIC POWER PLANT

 

WORKS FOR THE PROTECTION OF THE AGUAPEY STREAM

 

Introduction

 

Aguapey Stream Basin Protection is one of the main works for the finishing of Yacyreta Reservoir Project. This Project is fundamental since its completion will impede the flooding of vast territories of the Republic of Paraguay thought the elevation of the reservoir storage level to its definitive height of 83 m above sea level.

Main works consist of 64.5 km of land dams which begin in the left margin of the river in Rincon de Santa Maria, cross over the main branch where they reach a maximum height of 43 m. After covering part of Yacyreta Island, cross over Aña Cua branch, then continue through the right margin 25 km, finishing in Paraguay’s San Cosme and Damian cities.

Nearby Damian city is Aguapey Stream, tributary of Parana River, which discharges an average flow of 25 m3 / s over the reservoir at a level of approximately 78 meters.

The Elevation of the Reservoir to its definite storage level of 83 masl would flood Aguapey Stream Valley, generating a sub reservoir of over 450 km2 of which 360 km2 correspond to mainland and wetland, and the remaining 200 km2 corresponding to productive land.

To prevent this situation, Protection Works of Aguapey Stream have been developed consisting of a land dam in the stream mouth to avoid flooding when the reservoir in filled with more than the current storage level and, a drainage channel of 12.5 km long downstream which connects with the collection channel that exists in the dam’s bottom until it reaches the Aña Cua branch.

 

Aguapey II – Aguapey Stream Closure Dam

 

The second stage of the work consisted in the construction of Aguapey Dam with an approximate length of 4.3 km. reaching to a crest elevation over the asphalt pavement of 86.45 masl, the construction of an irrigation channel in the Paraguayan margin and the Closure of the Temporary Deviation and the Opening of Aguapey Deviation Channel simultaneously.

The original Dam Project included in the bidding documents consisted on a body of soil and a blanket towards the reservoir. The Dam contained two lower clay cofferdams in the stream channel bed that along with the blanket were works performed over 14 years ago. All the leaking control in the foundation relied on the blanket and wells of relief.

The Work consisted on the drainage of the sector between both cofferdams and the continuation of the Dam building works until it reaches a final profile of 86.45 masl.

Before the construction started, work direction had begun, by conducting a geological-geotechnical auscultation of the stream channel, the cofferdams and the blanket, in order to reassure that the emptying of the precinct was done in a safety manner.

This study was meant to contemplate the current state of the work that was going to be part of the final project, and the fact that the reservoir level was higher than the level expected when the dam was planned.

As a result, the conclusion was that the bottom of the stream presented significant soil heterogeneity with important permeable sand layers and that the blanket had low waterproofing capacity.

After calculations of thin matter in which filtrations and slopes stability were analyzed, the conclusion was that the central precinct couldn’t be emptied without risking   siphoning effect and cofferdams failure. Even though it was possible to empty the precinct up to a level of 76.50 masl, the work between both cofferdams should be done under a strap of approximately 4 m of water.

Since the blanket provided a poor water proving capability, flow lines were to be prolonged underneath the dam so as to decrease the gradients to acceptable levels.

During design adjustment, 3 constructive alternatives were analyzed to enlarge the flow lines underneath the cofferdams precinct:

  • A bentonite screen constructed underneath the cofferdam in Yacyreta side that goes up to the waterproof mantles
  • A waterproofing of the bottom of the central precinct between the cofferdams through the placement of a concrete layer poured under water
  • The waterproofing of the mentioned precinct through the collocation of a waterproof membrane under water. 

Comparative Studies were done taking into account constructive complexities, costs, work safety and construction time since there were contractual key dates related to the expected time for the elevation on the storage level of Yacyreta Reservoir.

From those studies, the last alternative resulted as the most convenient being the new dam project as indicated in the diagram below:

With the alternative defined, the constructive challenge was the correct placement of the waterproof membrane under a strap of approximately 4 m of water.

Giving the critical conditions of the Project, after having the bottom waterproofed and before the drainage of the precinct, this one had to be filled up with sufficient weight so as to prevent a siphoning effect and stability mentioned before. Filling the area with sand coming from the Parana River was the most viable solution.

The selected membrane was made up of Polyvinyl chloride of 1.2 mm. thick and a resistance of 15 Mpa according to ASTM 882.

The membranes were rolled in rolls of about 1.80 m. The panels were welded by heat with controlled temperature to achieve complete fusion of juxtaposed panels, forming a single piece of the size of the precinct to be fulfilled.

The joints were tested in perpendicular tension to the seam making sure that they possessed greater strength than the membrane itself.

Before the placement of the waterproof membrane, another geotextile membrane was spread on the bottom to protect the former of any tearing element that may be deposited in the bed of the stream.

Alter being welled, the membrane was rolled and placed over a pontoon withheld and mobilized by a hoisting engine for a controlled placement of it over the bottom of the stream.

Before the filling of the precinct it was necessary to counterbalance the membrane to avoid dislocation or movements.

For this reason geocells of 7.5 cm high, 1.1 mm thick of geotextile were employed as well as concrete slipped in a working platform on a maximum area of 1500 cm2 to transform them into counterweight articulated sheets. Afterwards, they were lifted with a rocker arm and collocated over the membrane with a crane.

The positioning and the correct placement of the membrane as well as the geocells were inspected underwater by divers from the Consulting Consortium.

Once the membrane had been counterweighted, the hydraulic filling of sand took place up to the level of the new project.

Alter the filling was done, the precinct was drained to the expected levels continuing in this way with the work in the traditional way.

The new design is stable even though if the membrane deteriorates or even if it disappears during the work. Something that is highly improbable.

The Dam Project is completed with the construction of an irrigation channel on the Paraguayan side with a volume of 600m3 of reinforced concrete.

Special Tasks had to be made for the coordination of the closure of the stream discharge over the reservoir and the simultaneous opening of Aguapey Channel.

Those tasks were performed under strict supervision and having developed an Operative Plan and a Plan for Contingencies on the handling of the plug cofferdams and the Channel gates that provide all the possible contingencies and other exceptional events that could appear while the Aguapey sub reservoir drainage was done.

 

The main data of the project is the following:

 

The Project Adjustment, Inspection, Contract Administration and Work Direction were in charge of the Joint Venture COINTEC-INCONPAR-GCM-ELEPAR-GEIPEX-GCA UTE under the denomination ENERYA Consortium.

 

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YACYRETA HYDROELECTRIC POWER PLANT

WORKS FOR THE PROTECCION OF THE AGUAPEY STREAM

Introduction

 

The Protection of the Aguapey Stream Basin is one of the main works for the finishing of Yacyreta Reservoir Project. This Project is fundamental since its completion will impede the flooding of vast territories of the Republic of Paraguay thought the elevation of the reservoir storage level to its definitive height of 83 m above sea level.

Main works consist of 64.5 km of land dams which begin in the left margin of the river in Rincon de Santa Maria, cross over the main branch where they reach a maximum height of 43 m. After covering part of Yacyreta Island, cross over Aña Cua branch, then continue through the right margin 25 km, finishing in Paraguay’s San Cosme and Damian cities.

Nearby Damian city is Aguapey Stream, tributary of Parana River, which discharges an average flow of 25 m3 / s over the reservoir at a level of approximately 78 meters.

The Elevation of the Reservoir to its definite storage level of 83 masl would flood Aguapey Stream Valley, generating a sub reservoir of over 450 km2 of which 360 km2 correspond to mainland and wetland, and the remaining 200 km2 corresponding to productive land.

To prevent this situation, Protection Works of Aguapey Stream have been developed consisting of a land dam in the stream mouth to avoid flooding when the reservoir in filled with more than the current storage level and, a drainage channel of 12.5 km long downstream which connects with the collection channel that exists in the dam’s bottom until it reaches the Aña Cua branch.

In this article I will refer to Aguapey I – Aguapey Stream Discharge Channel

 

Aguapey I – Aguapey Stream Discharge Channel

 

The first stage of the construction consisted on a linking channel from Aguapey stream intake position to the station 12+500 in which a junction is made between this one and the channel at the bottom of the dam in order to derive water from the stream to the discharge area in the Aña Cua branch. Construction began in the second part of the year 2005.

The path of the trace was carried out mostly on clay soils, having to go through an important basalt mantle, sandstones and altered rocks between the stations 8+100 and 10+275.

The first excavations in these progressives allowed us to perceive the bedding state of rocky mantles, having as a consequence important alterations that required a demanding and heterogeneous slopes project to meet the safety of all personnel and equipment employed during the process of excavation and also to meet the channel’s medium and long term stability.

For this reason the degree of alteration, the jointing and the RQD of the rock mantle have been entirely analyzed and different sections have been designed to assure proper slope stability.

Due to the alteration of the rock mass, blasting methods were adjusted as regards positioning, separation, depth and drilling load to the effects of making blasting works more efficient.

Taking into account the deep alteration state of the rocks and sandstones present and giving prestige to the integrity of the work in its expected long lifetime, slopes that don’t require injected anchors as a means of support were decided.

 In some cases of deep alteration shotcrete protective paving was done.

Pure soil areas were found with a few little rock outcrops up to the station 8+000.

In almost every section clay soil was found and slopes and lines sections 3H: 1V were design.

In these sections, excavations were done with conventional high performance equipment through traditional methods and intensive dedication.

Slopes protection was done with medium rank rocks up to the berm, which is likely to get into contact with the water flow, and through a vegetable protection and stabilization drainages in superior areas that presented possibility of collapse.

Main data as regards dimensions:

Channel Length: 12.5 km.
Design Flood:   700 m3/ sec
Regular Excavation Volume: 8.640.079 m3
Rock Excavation Volume: 1.863.895 m3
Total Volume of the Excavation: 10.504.000 m3
Channel Maximum Depth:        39.0 m.
Channel Minimum Depth: 8.0 m.
Storage level of the Channel’s Sill: 69.00 masl.

 

The Channel is crossed by many different building works that completed the Project.

One of them is the crossing of the 5B Route in the station 9+400. This route had to be relocated and re-projected and its crossing required a viaduct to bridge the irregularities caused by the channel’s slopes. In the Interjection between the route and the channel a structure was built to control the flow of water.

The viaduct was design with premolded concrete beams that were mounted through the use of launching beams. The total concrete volume was 750 m3.

The central section contains the Channel’s Flow Control Structure, made of four big columns that hold three flat gates set on by hydraulic mechanisms.

These Gates will allow the realization of maintenance procedures downstream.

The Control Structure involved the realization of 2.230 m3 of concrete.

The Channel Crossings are completed by 3 bridges for animal transit and an irrigation bridge with a capacity of 108 m3 to irrigate arable land in Paraguay’s territory.

Aguapey Channel’s Works were successfully completed and in the original deadlines established in December 2007, except for the Irrigation Bridge. Its construction is to be decided by Yacyreta Binational Entity in a near future.

The Final Project, the Inspection, Contract Administration and the Building Work Direction were in charge of the Joint Venture COINTEC-INCONPAR-GCM-ELEPAR-GEIPEX-GCA UTE under the name of ENERYA Consortium.

COINTEC, from The Argentinean Engineering Consultants Chamber (Cámara Argentina de Consultores de Ingeniería) acted as the Argentinean leading company.

 

 

 

 

 

 

 

 

 

 

COMBINED CYCLE POWER PLANT

DOCK SUD S.A.

RIVER COOLING WATER INTAKE N° 1 y 3

Adequacy

 

During 1999 Dock Sud S.A. built a new Combined Cycle Power Plant in Dock Sud – Avellaneda – Buenos Aires Province.

Due to the necessity of cooling water, the old intake channels Nº 1 and 3, which link the “Riachuelo” with the new pump house, were adapted.

COINTEC participated in the civil preliminary Project for the adequacy of the underground collection channels by checking and modifying the existing reinforced concrete structures and piling and, at the same time, planning new distribution channels and inspection wells.

 

SAN LORENZO HARBOUR

ESSO S.A.P.A.

 

Given the Risk Assessment Conditions defined by ESSO Company internationally, the redesigning of San Lorenzo Plant’s services was necessary.

COINTEC participated in this Project performing the following tasks in San Lorenzo’s Harbour:

 

  • Dock and Mooring Dolphins Topographic Survey
  • Bathymetry for the installation of water intakes for the fire fighting system.
  • Design of water intake for plant supply system.
  • Fire fighting system revamping.

 

 

 

 

 

 

 

 

SANITATION AND WATER RESOURCES

 

In 1998 the National Health and Social Action Ministry set in motion a plan for improvements in health facilities in its area.

As a part of this plan, COINTEC was in charge of The Remodeling of the Sanitary Drain and the Treatment System of Colonia Montes de Oca, Open Door, Buenos Aires Province.

The work involved the survey of the existing facilities, basic engineering for effluents treatment in two mechanized and aerobic plants and the preparation of the bidding conditions so as to call for public bidding.

Furthermore, it dealt with the remodeling of the Medium and Low Voltage Power Supply System and the Outdoor Lighting System.

The scope of the tasks performed was similar to the ones of the Drainage System.

 

 

 

 

 

 

 

 

SANITATION AND WATER RESOURCES

 

COINTEC has incorporated the environmental dimension to its projects, creating and developing for each one of them the engineering that combines the most modern, rational and effective techniques, with environmental protection and sustainable development concepts.

In this sense, COINTEC gives its clients the chance of carrying out an Assessment on the Environmental Impact in projects and Environmental Auditing as well as a Health and Safety Evaluation for Work Sites and Plants, assisting them in the use of the best environmental technology available.

In relation to what was previously mentioned, COINTEC has developed Sanitation and Environmental Control Projects, like COCA COLA Formosa Refrescos Effluents Plant and the remodeling of the Drainage system and effluents treatment of Colonia Montes de Oca Medical Center depending on SECRETARIA DE SALUD Y ACCION SOCIAL DE LA NACION (HEALTH AND SOCIAL ACTION DEPARTMENT).

During 1995, COCA COLA’s headquarters, established an international policy for the preservation of the ecology worldwide, stipulating that all their productive plants were due to treat their effluents by the end of 1996 in order not to contaminate the environment.

COCA COLA – FORMOSA REFRESCOS S.A. trusted to COINTEC the development of basic complementary engineering, detail engineering and the bidding conditions of their new effluent treatment  plant.

 



 

 

 

 

 

 

 

 

In the field of Hydraulics, COINTEC collaborated with IECSA in the study and budget of the bidding for the construction of the Storage Reservoir and Rainfall attenuators for Buenos Aires city. 

Buenos Aires City’s Government called for a public bidding.

The detailed study of the bidding conditions that COINTEC realized, allowed IECSA to comply with the mention bidding solicitation.

From flow verification, as in the duct sections and system automation till Vega Stream mouth draft, in Rio de la Plata, were, among others, COINTEC’s contribution to the study of the Bidding Project.

SANITATION AND WATER RESOURCES

 

Comodoro Rivadavia is an important Argentine southern city and the capital of petrol exploitation in Patagonia.

Located on the parallel 46 º South latitude and on the coastline, has no nearby sources of potable water supply.

For this reason it was necessary the construction of an Aqueduct from Munster Lake, located approximately 100 km. towards the West.

COINTEC collaborated with the Aqueduct executive project, being in charge of detailed engineering of Pumping and Anti-waterhammer Stations.

COINTEC collaborated also with the development of executive engineering and technical assistance during the construction of the Neutralization System in the Demineralizer Plant Expansion in La Plata Distillery of Fiscal Oil Fields.