Water Quality of Arroyo Willa (Esquél)

Water Quality of Arroyo Willa (Esquél)

By Lino Arturo Pizzolon

At the request of the Self-convened Neighbors of the city of Esquél, the concepts expressed in the report “Sampling, analysis and interpretation of a phenomenon observed in the Descolgado (or Amarillo or Will-a) stream located in the Cordón Esquél project (Province of Pcia. of Chubut) "

Analysis of Information on Water Quality of the Willa stream (Esquél cordon)

Until May 2005


1. At the request of the Self-convened Neighbors of the city of Esquél, the concepts expressed in the report “Sampling, analysis and interpretation of a phenomenon observed in the Descolgado stream (or Amarillo or Will-a) located in the Cordón Esquél project ( Province of Chubut) ”, produced by Dr. Marcelo Idoyaga, from the University of Buenos Aires.

2. This is the third report requested by the government of Chubut in relation to the spill of drilling fluids documented in the "Report on monitoring of water quality in the Willimanco stream basin" (1), and like the previous report, by Joyce Owen-Alberto Cerdá, of the Environmental Protection Directorate of the Province of Chubut, investigates only one of the hypotheses raised and concludes that indeed the phenomena of March 2003 respond exclusively to characteristics natural of the place.

3. The first was prepared by Dr. Adrián Pucci, director of CENPat, who without knowledge of the scene of the events, limited himself to a critical evaluation of the Coop16 report, pointing out some supposedly erroneous points, but emphatically emphasizing the importance and the need for further studies to elucidate the origin of the deposited sediment and the events referred to.

4. The second report was produced by the Directorate of Environmental Protection (Joyce Owen) on July 7, for the minister of production –Giaccone-, before the interpellation of deputies Retuerto and Zarcos. This report is based on a sampling carried out 45 days after the events denounced, the drilling activities being suspended and was in charge of the biologist Alberto Cerdá, lacking experience in mountain areas. Once the samples were taken using the mining company's means, the effort was focused on verifying only the hypothesis of a natural phenomenon in areas with acid drainage, without any attempt to demonstrate the presence of drilling fluids or their decomposition products. This report warned that a study would be requested from a "recognized" university, (2) and that the samples would be taken in duplicate, with the presence of the interested counterparts, Municipality, Cooperative, University and the DPA, notary public.

General considerations

5. If there are previous names for the stream in question, the use of the fancy names used by the mining company and by the government does not correspond. The original name is Will-a stream (Serra et al. 2000) (3), or Willa for simplicity. The naming is not a trivial fact. The name Willa is indicating its belonging to the Willimanco lagoon basin. The name introduced by the mining company, in addition to being inappropriate due to the existence of a previous name, is not innocent, since it insisted on convincing the population that said stream is not linked to the Willimanco lagoon, an environment that functions as Complementary drinking water reservoir for the city of Esquél.

6. The division of the course of the Willa stream into the upper, middle and lower reaches is correct for the purposes of better location of the described phenomena. However, the Idoyaga report frequently expresses conclusions referring to the upper section of the stream, -subjected directly to the natural acid drainage of the place-, as if they were applicable to the entire course, for which it generates serious confusion in the reader and reaches false conclusions in some cases. The acidity conditions and the production of secondary minerals and sediments like those mentioned by the author in the upper section, under normal conditions are strongly attenuated downstream, due to mixing with other waters.

7. In the Idoyaga report no elementary formalities were observed for its official / judicial validation: –a) No duplicate samples were taken or with the presence of the interested counterparts, Municipality, Cooperative. UNPat (The Cooperative). –B) the samples were taken without the presence of the personnel of the Environmental Protection Directorate, as required by the Environmental Protection Law 1503, to validate the procedures. –C) with the mining project area in the hands of the owner company, without judicial oversight, there are no guarantees that phenomena similar to those denounced in 2003 have not been intentionally caused.

8. It does not indicate anywhere if the conductivity measurements are compensated by temperature, and if they are, to what temperature they are referred, information without which these data are not comparable with each other or with others. As stated, the concept of harshness is open to misinterpretation. Hardness is not linked to sodium and potassium.

9. All observations on Willa Creek from here on, unless otherwise provided, refer to the lower section of the same. Some aspects of the Idoyaga report are taken up throughout the work from different angles, so some repetition is inevitable.

10. The Idoyaga report begins by stating that “the waters of the stream are of very poor quality, are not suitable for human consumption and present toxic conditions. This situation is not in itself indicative of contamination by anthropic activity (drilling fluids or any other cause), or of natural causes ”. However, the work carried out only tries to demonstrate the second of the possible causes.

11. The long section (Point 6), supposedly destined to demolish our foundations to speak of contamination, adolescent of the same failure of the Owen report. Preliminary Cerdá of the Chubut government: do not investigate the opposite hypothesis. This bias would be acceptable in a report by the mining company, but it is inadmissible in an official report, which is supposed to remain independent.

12. There are no previous data on the Amarillo stream. Faced with this very serious flaw in the EIA, which the Idoyaga report mentions but minimizes, raises and carries out an extensive analysis of the rocks in the basin in order to demonstrate that the same components found in the water and in the sediments are the found in the basin, stating then that it is not necessary to invoke any contamination process to explain the observed facts (point 7.1.2). The results turn into 13 pages destined to confirm the preconceived idea.

13. Too naivety and disregard for basic principles of scientific procedure are required to accept such a simplification without further ado. If the sampling had been carried out at the time of the events denounced, the contribution corresponding to the natural erosion of the rocks and the contribution corresponding to the drilling fluids should be discriminated and quantified. And it is, above all, to analyze specific components of the drilling fluids in remaining samples, an aspect that has been ignored both by the DPA and by the report that is analyzed.

14. In point 6.4, the Idoyaga report misinterprets the “methodologies used to postulate the contamination hypothesis” of the Pizzolon 2003 and Diaz 2003 reports, without considering the rest of the information provided in said reports. It thus introduces a serious conceptual flaw. The concept of pollution does not depend on the source of pollution, be it natural or man-made. Neither the levels of the hazardous waste law nor those of law 24585 (which introduced the environmental title in the mining code) have variations by region. If the proposal is accepted, the criterion would be established that in a naturally contaminated body of water, the prohibitions on discharges of anthropic origin that apply to any all body of water do not apply.

15. In the same sense, in 6.4 the Idoyaga report makes a vague and imprecise reference to “a sulfur compound” from the Willimanco lagoon based on a non-scientific journal, which is why it has “poor quality water for human consumption”. The Willimanco lagoon was used for more than 70 years to supply water to the city of Esquel and today it is a complementary environment to face any eventuality (droughts, population increase, rupture of the conduction pipes, etc.). It is not contaminated with heavy metals and it is well known that its hydrochemical characteristics respond to the geology of the place (4). The mention of the Willimanco lagoon in this report focused on the Willa Creek continues to surprise. The disagreement, as in the previous point, seems to be aimed at highlighting the state of natural contamination in the area and minimizing in government media and in public opinion the importance of subsequent pollutant dumps. This conceptual misrepresentation to which this report opens the door is unacceptable.

Drilling fluids

16. The Idoyaga report (6.2) indicates that none of the drilling fluids used could provide the elements that exceeded the limit values ​​for the trace elements indicated in our report. The lightness of this statement is remarkable, made without even mentioning the fluids used, much less indicating their chemical composition.

17. According to company statements (5)DD2200, Dies, Ultravis, Quick Gel Bentonite, Big Berar Diamond Drill Rod Grease, Polymer 550 were used. Depending on the source consulted, the lists of additives vary (Annex); There are testimonies on the use of diesel as a lubricant (Toca Madera radio program on 5/14/05), introducing from 20 to 60-80 liters per drill (x4) and per day.

18. Various drilling fluids are or have toxic components. Barite (used as a weighting agent for fluids) contains heavy metals such as mercury and arsenic as impurities. The existence of chromium, lignosulfonates, phenolic compounds, and highly risky compounds such as polyacrylamides. More information on drilling fluids was prepared in 2003 and is presented in the ANNEX.

19. The Idoyaga report notes that the Pizzolon 2003 report did not provide evidence for the existence of polyacrylamides. In this regard, it should be added that on 03/13/03 a "Deposition of an amber gelatinous substance on the membrane filters (0.45 µ) was described, which was not observed again two days later" (6). This consistency is typical of polymers such as Ultravis (polyacrylamides), which were being used extensively in perforations (source reserved).

20. The reasons why analytical evidence was not provided at that time were detailed in the ANNEX report (Pizzolon 2003).

21. In the Idoyaga report there is no attempt to analyze acrylamides or their decomposition products in material preserved from the first spill, nor does it make an analysis of these compounds in the 2004 sludge to identify similarities or differences.

22. The impacts of drilling fluids are often minimized in relation to other, much more serious impacts of mining activity. However, in countries like Mexico, the use of drilling fluids is subject to the annual approval of rigorous tests for toxicity, ecotoxicity, etc.

Comparison of the state of the stream in March 2003 and April 2004

23. The scientific nature of a report is not given by the complexity of the technologies used, nor by the prestige of the institution that supposedly endorses it, but by the internal coherence of the hypotheses formulated and by the relevance and solidity of the evidence that is contribute to prove or deny them.

Figure 1
The rigorous description of the observed phenomena, their organoleptic characteristics and their precise spatial location, constitute the unavoidable basic starting point for any report that claims to be scientific. In this sense, the Idoyaga report has not paid enough attention to our descriptions, thus making notorious errors.

Figure 2
24. The statement of point 6.1, and of conclusion 4, “all the characteristics observed in March 2003 were repeated in April 2004 in the absence of perforations” is false. First, because you cannot make affirmations or denials about a fact that you did not witness (March-03). Second, due to its own photographic documentation in the lower section of the course (photo n ° 42), in which no deposit similar in magnitude and characteristics to the one documented in March 2003 is observed (Figs. 1 and 2).

Third, from their own descriptions (p. 5), “depositing is usually observed…. where there is little depth of the watercourse ... the turbulence decreases and the speed of the current decreases ”, our report makes express reference to the striking fact of the total coverage of the bed bathed by the water and in a uniform way. Fourth, due to its subsequent descriptions that indicate that in the middle section of the stream ".. is where the greatest amount of yellowish-brown gelatinous sludge is deposited", a situation very different from that observed in March 2003. Fifth, due to our own data and direct observations on both occasions in March-2003 and in March-2004, within the framework of the control project maintained by the Cooperativa 16 de Octubre Ltda. (7)

Figure 3

25. What is mentioned in the previous point, together with the failure to observe the sampling procedures mentioned in 6, is enough to invalidate the entire report. However, its analysis is continued for the purposes of a major.

On acid drainage of rocks (dar)

26. The Idoyaga report expands on the DAR phenomenon, clearly dominant in the upper section of the Willa creek, located within the mining project area. Undoubtedly, this phenomenon explains acceptably some of our observations on the ferruginous precipitates in the middle section of the stream, described in the report of May 2003 and not correctly interpreted at that time and attributed to overturns of different origin throughout the summer. However, these natural characteristics of the site, which are correctly described, cannot be used to cover up spills of clearly anthropogenic origin or to obviate their investigation.

27. The statement in point of the report in question: “in spring the waters of the Willa Creek are not cloudy or colored” is false. The statement "from October to March there is a growing trend in conductivity, and a growing trend in turbidity and water color": it is only true in the case of mining activities in the headwaters; in the absence of disturbances the trend is exactly the opposite. Therefore that statement is also false. The Idoyaga report is based on two days of sampling in April, therefore, unless you provide some kind of evidence for it, you should refrain from making statements about what happens during the rest of the year. Secondly, our results taken throughout 2004, without mining activity, show exactly the opposite (see 38 and following).

The statement of the Idoyaga report regarding the acidity of the stream in point 3.3 and 6.1, generates confusion, causing it to reach false conclusions: on no occasion was acidity recorded in the middle section, much less in the lower section of the course; A very acidic pH was only recorded on a single occasion, the middle section, coinciding with the March 2003 event.

On the seasonality of acid drainage

As a general rule, the periodicity of acid drainage in elevated areas - the acidity peaks and accompanying phenomena - occurs in early spring. In this situation, the acidifying material accumulated during the period without liquid water is dragged downstream, a fact well known in the literature on RAD. (8). A similar phenomenon occurs in mountainous regions with acidic precipitation. The peak of greatest acidity occurs at the beginning of the thaw and precedes the maximum spring flow by several weeks. It is striking that the Idoyaga report did not refer to this characteristic of the DAR, which is highly significant for elucidating the facts at hand.

30. The seasonality of the DAR cannot be invoked, as has been done both by the company and from the governmental sphere, for it cannot be invoked is to explain any acidity peak and downstream drag of clays and colloidal materials, at any time of the year . In this sense, March is the month in which the least possibilities exist that the phenomena that accompany the DAR are observed downstream of the sources.

Acidity peak registered in the middle section on 03-15-03

31. Chemical data in the middle section of Arroyo Willa are too scarce to constitute a reliable baseline. This caveat does not exempt from rigorously considering the information available, even if it is scarce.

32. In the middle section of the Willa stream, immediately before small water courses that we call Huenú (T2 of the Idoyaga Report), the pH values ​​-including those of the Idoyaga report- were always higher than 7. The only strongly acidic record, pH 4.75 (3.80 in the laboratory) was that of 03-15-03 referred to in Pizzolon 2003. It is striking that 15 days later -suppression of exploration tasks by means of (9)-, the pH rose from 3.8 to 8.76 units, figures that represent a decrease in acidity of more than 91,000 times.

33. The Idoyaga report states (6.2) that none of the drilling fluids have additives that could have caused the mentioned acidity peak. However, the referred data is a real data from two readings with two different equipment of excellent quality, one from the WTW field (4.75) and the other from the ORION 720 laboratory with Ross electrode (3.8). How to explain, then, such a low pH value in the middle section of the course, in a place where acid drainage is already normally neutralized?

34. The aforementioned event occurred in the historically driest month of the year. The registry of the rainfall station of the University (Km. 4) indicates total absence of rainfall in 48 days prior to sampling. Therefore, there are no known natural causes that can explain a change in pH of such magnitude during that time.

35. The remaining explanation is that said acidity peak comes from some type of anthropogenic disturbance of the DAR. A plausible hypothesis is that the acidifying material generated and accumulated in the A ° Willa headwaters, in the terminal part of the underground aquifer, was caused to drag downstream in a dry period. Any increase in flow, whether by water or by drilling fluids, even momentary, dragged a large amount of said substrate downstream. This material can produce very low pH peaks as well described in the Idoyaga report. It was not neutralized in the middle section, as occurs in normal conditions (immediately upstream of A ° Huenú).

36. In other words, the drilling fluid spill carried a large amount of acidifying material downstream. The higher the acidifying load in the lower headers and the greater the distance the acidity peaks and secondary minerals that are formed. The aforementioned events constitute a small sample of what could happen there in gigantic dimensions and for centuries, in the case of a mining exploitation.

Influence of exploration tasks on the water quality of Willa Creek

37. As indicated in the Diaz report (10), the monitoring data of the Willa Creek during the exploration period taken by Meridian Gold, allows to observe the increase in conductivity, total dissolved solids and some heavy metals from October 2002 to March 2003.

38. Total suspended solids or TSS, is a basic measure of water quality, normally correlated with turbidity, and indicates the amount of particles that are retained in a filter, whatever their origin. Under natural conditions the TSS depends on the flow rate and varies with precipitation or thaw. In simple terms, the higher the flow, the higher the TSS and the higher the turbidity. Comparing the TSS data taken monthly by the MG company during the exploration period (11) and the data subsequently taken by the Coop. October 16 (12)Far from the drilling period, it is observed that the TSS values ​​of MG are clearly increasing as the exploration tasks progressed on the western slope of the watershed, towards the end of the summer (Fig. 1, blue bars ). In autumn and in the absence of drilling (March 2004), the stream presented the minimum TSS, and in this sense, in the absence of disturbances in its headwaters, the Willa stream functioned like any other stream in the forest-steppe ecotone (Fig. 1, yellow bars) These data are not strictly comparable with each other in absolute values, since the techniques of the two intervening laboratories, eg. filter pore size used, have not been intercalibrated. But they are comparable with those of the group itself and allow us to visualize clearly different trends in both periods of analysis.

Figure 4. Graph of total suspended solids in the lower section of A ° Willa. Dark bars: monthly data from Oct-02 to Mar-03 for Meridian Gold, during the exploration period. Clear bars: CASEP project quarterly data from Dec-03 to Oct-04. Time scales were overlaid to highlight differences. See more explanations in the text.

Figure 4

Figure 5. A ° Willa springs. Arrow in the center: trace of perforations during the events of March 2003. Arrow to the left: headwaters of A ° Willa.

Figure 5

39. The drilling tasks -up to 200 m depth- were carried out in the same springs of A ° Willa (Fig. 5). Therefore, the infiltration of drilling fluids into the groundwater and subsequent emergence in the headwaters of the stream is perfectly plausible. This hypothesis does not rule out possible direct surface dumps or spills from the existing lagoons at the stream's headwaters. In any case, regardless of how the fluids reached the watercourse, the consequences were seen downstream.

Evidence of a massive drilling fluid spill

40. A change in the concentration of hydrogen ions of more than 91,000 times in the driest month of the year (03-15-03), in the middle section of the Willa stream, referred to in 32 et seq.

41. Absence of rainfall in 60 days, only 1 mm on March 19 (13).

42. Observations of the organoleptic characteristics of the phenomenon on March 13: observed on March 13 and in subsequent weeks by technicians and neighbors (14).

a) Flocs in the water; b) straw yellow color c) Adhesion and sealing of the deposit, once dry, on all the rocky particles and sands of the bottom, d) formation of a continuous film of every bed bathed by water, as a waterproofing of the bottom; a) Deposition of an amber gelatinous substance on the membrane filters (0.45 µ), which was not observed again two days later (15).

43. Extension of the spill to the end of the lower course of the Willa Creek, where it is lost in a wash.

44. The fact that two days later the gelatinous material was not observed.

45. There is no guarantee that a phenomenon similar to that of 2003 has not been artificially simulated. Even so, there is no evidence of its repetition in 2004 and 2005. On 05-13-05 some precipitates were found adhering to gravel at the bottom in the lower section, but in no case is this close to the magnitude of the events documented in 2003.

Legal aspects

46. ​​The increasing impact of the mining activity on the quality of the water in the Willa stream and the multiple evidences of a massive spill verified on 03/13/03 constitute events that clearly violate the Water Law 1503 of the province of Chubut and its regulatory decree 2099/77.

47. In the same there are very clear provisions that prohibit the discharge of any liquid, solid or semi-solid effluent, which alters the visual and organoleptic characteristics of any water course, which "causes any detriment to the receiving body" in addition to damaging human health. (Regulatory Decree 2099/77, art. 31). In art. 14 of the same decree, states that "the discharge or injection by any means, of all types of waste into underground waters is expressly and strictly prohibited." In article 26, which lists the substances whose discharge is prohibited, in subsection f), “all those that interfere with the purification processes of the receiving body”.


48. Considering the formal and procedural defects mentioned in (7) and the unsubstantiated assertions (25,28,29), the Idoyaga report should be rejected without further analysis. However and for the purposes of further clarification it is stated:

49. The report contributes to a better understanding of the nature of the Willa stream, demonstrating the existence of a natural acid rock drainage (ARD), dominant in the headwaters of the same but that is attenuated downstream by contributions from other water courses, being practically unobservable as such in the lower section.

50. This implies, on the one hand, attenuating some of the expressions made in the Pizzolon 2003 report, in the sense that it is possible that the absence of all forms of life is due to the relatively extreme characteristics of this environment and that this has been prior to any effusion or subsequent anthropic alteration.

51. However, this natural phenomenon cannot be invoked to disguise an event that is clearly out of the ordinary observed on 03/13/03 and subsequent weeks, which spanned the lower end of Willa Creek, with magnitudes never previously observed or subsequently repeated. .

52. The Idoyaga report is focused on demonstrating only one of the hypotheses, that the compounds found in the stream water are the same as those that make up the rocks in the basin (p 7.1.3, and conclusions). As is well known, this is obvious anywhere in the world, at least for surface waters. All this information is not relevant to the problem in question.

53. It does not propose and does not even raise the need to investigate the presence of drilling fluids or their degradation products in any remaining material from the reported spill, nor does it make any contribution in this regard. This notorious bias could be accepted in the case of a report from the mining company, but by no means in a report from the official sector, and that involves a National University, entities from which strict impartiality is expected.

54. It is false to invoke the seasonality of the DAR to explain the events observed in March 2003, 1) because, as a general rule, the DAR in elevated areas, with snowy deposition, manifests itself at the beginning of spring, 2) because it never happened again. observe the phenomenon 3) because it does not explain how the event occurred in the historically driest month of the year and in the complete absence of rainfall in the previous 48 days, or of any other natural event, 4) because in the soil profile there is no no sign of stratification left by a periodic event. The sediments are all very dark up to 50 cm deep.

55. In addition to one or more specific direct spills to the watercourse through the aquifers, I reaffirm what was expressed in the Diaz 2003 report and provide further evidence that makes it possible to compare a period with mineral exploration and another without exploration, and confirms the negative impact increasing throughout the exploration period.

56. The Idoyaga report quite rightly points out the internal contradictions of the EIA regarding acid drainage. In this sense, we can conclude by affirming that said report constitutes the best demonstration produced to date that all mining activity in the headwaters of the Willa and Esquel Viejo streams will do nothing other than remove and disperse the enormous deposit of highly toxic materials that are found there locked up and from which only the gold and silver would be extracted.

* M.Sc. Linen Arturo Pizzolon
Director of the Aquatic Ecology Laboratory
Faculty of Natural Sciences
National University of Patagonia SJB
Sarmiento 849 - (9200) Esquel - Chubut


(1) L.A. Pizzolon. 05-13-03. UNPat-Coop Agreement. October 16. Annex of Tabajo No. 2.
(2) Note dated 07-11-03 to deputies Retuerto and Zarco from Minister Giaccone accompanying the report Joyce Owen.
(3) National University of Patagonia. Work on the water resources of the Esquel area.
(4) Pizzolon, L. and others. Various technical reports, UNPat-Coop16 Agreement. 1992-04.
(5) Note 680 from Mónica Mariaca to the Director of Environmental Protection, dated 07-07-03.
(6) L. Pizzolon Report, ANNEX.
(7) Collaboration between the National University of Patagonia SJB - Cooperativa 16 de Octubre, CASEP Project (Water quality in the Esquel-Percey System).
(8) Proceedings form the Fifth International Conference on Acid Rock Drainage, Society for Mining, Metallurgy and Exploration, Inc. (SME), Littleton, CO, USA. Linen Arturo Pizzolon. Aquatic Ecology Laboratory. F.C.N. UNPat. 8/13
(9) Inspection Certificate of the Mining Directorate, -delegation Esquel.
(10) Fernando Máximo Díaz. 2003. Evaluation of the water and sediment analysis of the Willa stream, presented to the Cooperativa "16 de Octubre" by the company Meridian Gold on 06/06/03.
(11) Meridian Gold report delivered to the Coop. October 16 dated June 6, 2003, With a note from Manager Edward Colt. Análisis de metales pesados realizados en el Laboratorio de Ingeniería Laboral y Ambiental de Cba.
(12) Proyecto CASEP, UNPat-Coop16.
(13) Información de la Estación Meteorológica de la Universidad Nacional de la Patagonia
(14) Ver Anexo
(15) Anex

Video: Water by the Numbers. GOOD (May 2021).