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Geology 101 for Grass Valley Residents at Public Workshop on Emgold's Proposed Mine
Geology isn't a precise predictor for the future, especially when it comes to Emgold's proposal to reopen the old Idaho-Maryland gold mine in Grass Valley. That was the message at a public workshop last Wednesday during which consultants preparing a draft Environmental Impact Report (EIR) on the project focused on the known geology of the area - roughly Bennett Street to the Brunswick Basin - and most importantly, how the proposed dewatering of 72 miles of flooded mine shafts might affect nearby domestic well water supplies, as well as surface water.
Geohydrologist Tom Knoch of Environmental Science Associates (ESA) broke down the geology of the area, summarizing: "This whole area is crazy. ... There are no similarities and no continuity. Will there be dewatering of wells? I can't say what's going to happen. No one can say what's going to happen. Only God knows."
During a presentation titled "Geology, Geochemistry and Groundwater," ESA Project Manager Jeff Harvey noted that groundwater is the most complicated issue and one of the greatest concerns. "This is a priority issue and we wanted to have this discussion," Harvey said.
The Idaho-Maryland Mine current depth is 3,280 feet and Emgold wants to drill about 2,000 feet deeper. Most of the old mine workings are at the 1,000-2,000-foot levels and are under Bennett Street and Greenhorn Road and run into the Brunswick Basin area. What is known is that the naturally-occurring underground cracks in the rock and mine workings can interface at certain points. Where, that's anybody's guess.
The deepest water wells in the area are no deeper than 300 feet, which places them a distance above the existing mine workings. Potential impacts being considered include a partial dewatering, meaning yield or storage capacity decreases, and complete dewatering, meaning a well runs dry.
Emgold has often referred to an "impermeable" layer between private wells and the mine workings below. This notion of a waterproof layer seemed to be debunked last Wednesday during the discussion of how fractures in the rock connect and form a chaotic, unpredictable system.
"We recognize the uncertainty and will take that into consideration when we formulate our response (in the draft EIR)," Harvey said.
While research for the EIR is ongoing, ESA's consultants think that sudden well failures are not likely. "Any changes would be gradual," Knoch said, adding the likely connection of wells and mine workings decrease with distance.
The potential for gradual changes jibes with what a number of experts told YubaNet.com for Golden Gamble in Grass Valley, a 5-part special report on the proposed hardrock gold mine. Robert Glennon, a University of Arizona law professor and author of "Water Follies: Groundwater Pumping and the Fate of America's Fresh Waters", said, "You don't know until you pump. My hydrology buddies tell me that there's no such thing as completely impermeable surfaces. Everything's relative. "It may take years and even decades before it becomes obvious that the groundwater pumping has affected surface water. " Surface water moves quickly. Groundwater moves through sand and gravel, but it still moves. It still moves."
Glennon said to "Think of an aquifer as a giant milkshake glass and each well as a straw in the glass. Like most American states permit, if you allow limitless access to a finite resource, that is a recipe for disaster. " (Dewatering an Old Mine).
Emgold, a junior mining company from Canada, wants to explore for gold starting in 2010 or 2011, after the 72 miles of existing tunnels are dewatered. During the dewatering process 2,700 gallons of water would be flushed down Wolf Creek every minute.
Wednesday's meeting was a special session to apprise the community how the work is going and give residents a chance to ask questions. Two more workshops will address other key issues - water quality on Jan. 23, and another on cumulative effects on Feb. 13.
The Draft EIR is slated to be ready in late spring 2008, with details about the environmental impacts that will be caused by proposed mine operations and also mitigation plans to offset any impacts. Before dewatering and mining, Emgold will need approval by the City of Grass Valley as well as state and federal agencies.
Wednesday's public workshop afforded residents the opportunity to ask consultants questions about geology and groundwater.
Here are some of those questions and comments by the public with answers from the consultants and additional information provided by YubaNet.
Q: "Water is a resource, like oil. Won't we be flushing a lot of water down Wolf Creek?"
A: Initial dewatering of the mine will mean 2,700 gallons of water per minute will be pumped down Wolf Creek for about nine months around the clock. Knoch pointed out that beyond the pumping, water can be "recharged": "You average 55 inches or rainfall a year. For every inch of rain per acre, you accrue 27,000 gallons. That's a lot of water - a continual recharge."
More information: The Initial Study of the Idaho-Maryland Mine Project notes: "... dewatering activity would continue thought the life of the project (20 years). At the New Brunswick site, mine water would be pumped directly to the on-site water treatment plant at a rate of up to 6 cubic feet per second (cfs) or 2,700 gallons per minute (gpm) to dewater the underground workings to the 3,280 level to enable industrial mineral and ore extraction. It is expected it would take about 24 months for the historical workings to be evacuated to this level. After initial mine dewatering, the dewatering rate would range between 500 gpm and 1,200 gpm, varying by season, throughout the life of the project."
Q: "Water is a finite resource and decreasing in the Sierra. We can't be irresponsible here."
A: This issue will be further addressed in the water quality workshop on Jan. 23.
More information: Due to accelerating climate change, water and geology experts had some dire predictions about water supplies in the entire Sierra Nevada that were presented during the Sierra Nevada Conservancy symposium, held on Dec. 5 in Nevada City. (Experts Talk Turkey about Climate Change at Sierra Nevada Conservancy Symposium)
During that event, Dan Cayan of Scripps Institution of Oceanography/U.S. Geological Survey noted that runoff from winter snow is beginning up to three to four weeks earlier than normal. This poses a problem for much of the state, which relies on the Sierra for 60 percent of its freshwater supply.
As snowpack transforms into rain-field runoff, the dynamics of our water management will need to adapt: "This could mean that in the future we are not dependent on our surface water but groundwater," said Lorraine Flint, geologist at the U.S Geological Survey.
In other words, rising temperatures are melting the Sierra snowpack earlier, causing rivers and streams to peak earlier. The state's reservoirs are fed by the winter rainy season and as those levels are drawn down, they are replenished by the snowmelt. The earlier the snow melts in the mountains, the sooner accumulated water from the rainy season has to be released from reservoirs, to make room for the snowmelt and prevent flooding.
"The transformation from snow dominance to rain dominance presents a significant challenge for water managers," said Frank Gehrke of the California Department of Water Resources.
At this stage, it is unknown if the EIR will address any potential impacts of climate change.
Q: "The veins are going through secondary fracture zones that house water. What does that mean to groundwater?
A: "Not much unless you mine right there. Most veins do not have mine workings in them," Knoch said.
Q: "What about the well monitoring program?"
A: Most, if not all, domestic wells were dug in the 1950s - the Idaho-Maryland Mine ceased operations in 1956 - so no historical information is available. Emgold has maintained a voluntary well monitoring program for 10 years to make a monthly check of water depth levels in 60-80 wells in the area. Through the years, more than 8,400 readings have been taken and provide a wealth of information. "When you have that much data you can start to see the trends," Knoch said. "These wells would act as a pre-warning."
Although the percentage of the wells in the monitoring program to the overall number of wells in the area is not known, the data is representative and valuable, Knoch added.
The monitoring program will continue if the mine project is approved. "In the EIR we will look at the well monitoring program and have mitigation plans to ensure no wells go dry," Harvey said.
Other information: The Initial Study notes: Emgold "has monitored water levels in domestic well proximate to the New Brunswick site since the mid-1990s for those property owners that volunteered to participate in IMMC's well monitoring program. The data generated will be evaluated as part of the EIR. As a part of the project design, (Emgold) is working with the Nevada Irrigation District (NID) to plan the extension of trunk lines to areas that have a potential to be impacted by the mine dewatering."
Q. "What about future domestic wells? There are many undeveloped parcels in the area designated for development - will the potential to find well water decrease for those parcels?"
A: Consultants referred to existing knowledge about the area that is applicable to new development as well. The closer a domestic well is to the mine tunnels, the more likely it will be affected. Not necessarily related to mine operations, the closer domestic wells are to each other, the more likely they will compete for the same water source.
Q. "Who is paying for EIR?
A: Emgold pays the city to hire a consultant, and the applicant will pick up the tab, estimated at about $800,000. No taxpayer money will go toward the EIR, and ESA consultant Jeff Harvey reassured residents that they were working for the City of Grass Valley and not Emgold. Outside routine meetings with city officials and Emgold representatives, the consultants do not have contact with Emgold.
Q: "You can't assure us what's going to happen (in regards to well water)?"
"That's correct," said Harvey. He added, "There may be changes in wells and due to complexities you cannot predict. We will monitor this during dewatering of the mine. And there will be mitigations to get people water. We recognize the uncertainty."
The Initial Study was completed in September and can be downloaded from the city's website. All of YubaNet's articles about the proposed mine are archived in the Special Report section.
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