The Eagle Lake Guardians (ELG) — a group formed by Spalding residents Rebecca Walker, owner of the Eagle Lake General Store in Spalding, and Valerie Aubrey, publisher/owner of Eagle Lake Fishing Information and Network — want answers from Pacific Gas and Electric Co. (PG&E) regarding its weather modification/cloud seeding programs in Northern California.

In an effort to get answers to its questions about how seeding impacts the local community, ELG submitted a formal letter of request to PG&E July 1 and is anxiously awaiting a reply.

“There are no regulations on weather modification. All PG&E has to do is give a letter of intention to (the Department of Water Resources and) put a notice in the paper, then they legally can use whatever chemicals they choose to use,” Walker said. “What goes up will come down.”

Many detailed studies have been conducted to address questions concerning possible negative health effects of the chemicals used in the seeding process. These studies have ranged from chemistry-focused work to environmental investigations.

The process of cloud seeding employs two categories of materials, which are tied to the type of precipitation process involved. One category includes substances that act as ice-forming agents, such as silver iodide, dry ice and compressed liquid propane or carbon dioxide.

The second category is focused on cloud systems where the warm process predominates. In those environments, water-attracting materials such as salt, urea and ammonium nitrate may be utilized.

Proponents claim no significant environmental effects have been observed due to the use of the cloud seeding materials. They argue seeding supplies are used in very small amounts relative to the size of the geographic areas being affected, so the concentrations of iodine in rainwater or snow from seeded clouds is far below the concentration found in common iodized table salt.

Others, including members of ELG, believe the chemicals used in seeding are hurting the environment and its inhabitants. Therefore, ELG has asked PG&E to supply a copy of its Weather Modification Environmental Impact Statement for California; a list of all the weather modification programs ongoing in the past two years in California by county; and a complete list of chemicals, gases, particles and methods used for cloud seeding in California in the past two years.

ELG also requested specific information about PG&E’s cloud seeding methods in the local area using aircraft and ground-based methods; results from water, air and soil tests conducted by PG&E in the last 10 years; detailed questions about air quality impacts from seeding; and several other general questions.

According to Walker, PG&E ramped up seeding in 2006 because the demand for water was getting bigger and bigger. She said ELG members are worried Lassen and Plumas counties are becoming a “toxic chemical dump” all because Northern California has to supply water to Southern California, and it doesn’t have enough precipitation to meet everyone’s needs.

For more information about ELG visit eaglelakeguardians.org, call 825-2191 or 249-1430, or email eaglelakeguardians@yahoo.com.

Cloud seeding 101

Cloud seeding, or weather modification, is the process of spreading either dry ice or, more commonly, silver iodide aerosols into the upper part of clouds to try to stimulate the precipitation process and form rain.

Attempts to modify the weather have been conducted for centuries. However, modern cloud seeding dates from the 1940s, springing from a discovery at the General Electric labs in Schenectady, N.Y., in 1946.

According to one source, the ability of dry ice shavings to convert super cooled water droplets (those existing as water at temperatures lower than freezing) to ice crystals was observed during the conduct of an unrelated experiment.

Later consideration of those observations led to a series of laboratory trials that demonstrated the nucleating properties of various materials in certain cold cloud conditions. Trials in the atmosphere soon followed, and operational cloud seeding programs began in about 1950.

Over its history, modern cloud seeding has involved projects of various types in nearly 50 countries around the world. Some individual projects have been in operation nearly continuously for decades, with a few operating for nearly 50 years. As water needs increase worldwide, the demand for weather modification services will also likely increase.

The history of cloud seeding has experienced uncertain results because it can never be known whether a cloud that rains after seeding might have rained anyway. This is because seeding is performed on clouds that look like they have some potential for producing rain.

The materials used in cloud seeding include two primary categories, which are tied to the type of precipitation process involved. One category includes those that act as glaciogenic (ice-forming) agents, such as silver iodide, dry ice and compressed liquid propane or carbon dioxide. Of the ice-forming materials, the most commonly used is silver iodide.

The second major category is focused on cloud systems where the warm (coalescence) process predominates. In those environments, hygroscopic (water attracting) materials such as salt, urea and ammonium nitrate can be utilized. Of the hygroscopic materials, the most commonly used are salts.