BLPA Action Plan for the Alum Project
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BLPA Action Plan for the Alum Project
1. Why are we putting alum into the Bear Lakes?
The algae that turns lakes green feeds on nutrients from two main sources: internal and external. The internal source is recycled nutrients from the bottom sediment. Lakes get worse over time because nutrients (mainly phosphorous) accumulate in the bottom sediments. This is our main target. With alum we can literally turn back the hands of time by eliminating the possibility this phosphorous will ever cycle back into the water where algae can feed on it. As a bonus, alum also traps toxic heavy metals.
External sources include lawn fertilizer and other contaminates in stormwater run off and pollutants in the atmosphere that fall on the lake. Our secondary target is water clarity. We can add alum as needed to improve/restore water clarity. (This is why alum is used to clarify drinking water and swimming pools.)
2. What were the results of the alum study?
The study produced two possible courses of action. One was to put a large amount of alum into the lake at one time to sequester all the bottom nutrients and any new nutrients from external sources for up to 10 years. This large dose would also strip the water of other particles turning it crystal clear overnight (flocculation). The second and recommended course was to put a smaller amount of alum in the lake to last about a year or two. Then put maintenance doses of alum in future years as needed to achieve the water clarity we want.
3. Do we know how much phosphorous enters the lake each year from external sources?
No, we don’t. We could get a rough idea at a cost of about $30,000. Even if we knew how much phosphorous entered the lake each year and from where, it would not tell us how much alum to use in future years as land development progresses. The most cost effective and accurate way to determine how much phosphorous enters the lake each year is to monitor water clarity as we have done for many years, and see how much alum it takes to keep it clear. A fixed amount of alum combines with a fixed amount of phosphorous. It’s a constant that will allow us to know how much phosphorous enters the lake from external sources just by measuring how much alum it takes to keep the water clear.
4. Who did the study and what are their qualifications?
The BLPA Ecology Committee that is being guided by our consultants, Dr. Harry Gibbons (just elected the new president of the North American Lake Management Society) and Dr. Eugene Welch (he wrote many of the textbooks on the subject of limnology) together have treated over 250 lakes with alum. They are the best in the country.
5. Why not just use one big treatment and be done with it for 10 years?
One, since we do not know the amount of external nutrient influx, we would not be able to calculate how much alum to use for a 10 year solution. Two, one big dose would cost more than multiple smaller ones, because that much alum at one time would require using a buffer which adds to the price of materials. It is more cost effective and safer for the fish and bottom dwelling life to use small doses. Three, the “10 year fix” could lead to a false sense of security at a time when we should be increasing our efforts to lower external nutrient imports including eliminating excess fertilization, getting more lawn companies to eliminate phosphorus, pressuring stores to carry phosphorous-free fertilizers, installing more berms and swales, and supporting government efforts to pass rules to reduce the amount of fertilizer residents can apply. Without continuing our efforts to reduce external loading, the 10 year fix could end up only lasting a few years.
6. I’m glad we’re looking out for the fish and bugs, but is alum safe for humans? Can it cause Alzheimer’s?
Alum has been used for decades to clarify drinking water and as a leavening agent in breads and other foods. If you have a swimming pool, you have probably used it as a water clarifier and swim in it as much as you would the lake.
Alum forms a very stable and inert compound when mixed with water. It will settle to the bottom of the lake as a floc and permanently bond to the bottom over time. So the aluminum will not be in the water, but be part of a stable compound on the bottom. In any event, it is not advisable to drink lake or pool water whether it has alum in it or not.
7. Is this floc a slimy layer covering the bottom that I would not want to walk in, and how will it be vacuumed up?
There will be no need to remove it. We will only apply the alum in water 16 feet and deeper. These deep areas are where the nutrient-rich sediments have drifted by gravity and accumulated over time. No alum will be applied in water anywhere within wading distance of your waterfront unless it is more than 16' deep or you are very tall. The floc will eventually mineralize and become part of the bottom just like the sand.
8. In that case, will the alum only clear the water in the deep areas of the lake?
Water clarity will be achieved by starving the algae that makes the water green and cloudy, not by flocculation. The source of the recycled food is mainly from the deep areas of the lake. But since the water circulates throughout the lake, all the water will eventually be the same clarity.
9. How much will this cost?
Experts that have done this on other lakes estimate anywhere from $30,000 for one treatment that might last a year up to $300,000 for a dose that could last up to 10 years. Our plan is to collect enough to apply a smaller dose and have money left over to pay for maintenance applications in future years without going back for more donations. We would not expect to spend it all in one or even two years but use it as needed to keep the lakes clear. Once we get an idea of what the annual external nutrient loading is and its trend, we can more accurately forecast future needs.
10. Will financial reports be available on a periodic basis?
Yes, we are going to maintain a separate account for this project. The monies will not be used for any other purpose or mixed in with the general BLPA treasury. Just like the Bear Lake Action Coalition fund, if for some reason the funds are not used, they will be returned. We are looking at methods of providing reports including the BLPA website. The only information we cannot divulge is who donated how much as some contributors wish to remain anonymous.