China Lake Watershed-based Management Plan
Alum Frequently Asked Questions (FAQ)
Food + a cozy home = algae blooms that degrade water quality. To expand:
One of algae’s main food sources – phosphorus – has entered the lake from stormwater runoff on developed land, leaking septic systems, timber harvesting, poorly maintained dirt/gravel/paved roads, fertilizers and other sources of soil erosion.
Phosphorus is also present due to the internal recycling/loading from stored phosphorus in lakebed sediments.
Warmer summertime water temperature and a longer growing season encourage algae to grow quickly and stay in the lake longer.
When algae grow quickly, an algae bloom can occur – this degrades water quality because the algae bloom reduces water clarity. Water can even become toxic to people and animals if the algae is a toxin-producing species.
When algae die, decomposition consumes the dissolved oxygen that fish and other aquatic wildlife depend on to survive; further degrading water quality.
China Lake’s water quality has been degrading since the early 1980’s. The lake has been extensively researched since then, with multiple studies recommending aluminum treatments (although none have been performed).
Left untreated, China Lake’s phosphorus problem means ongoing, persistent algae blooms that will adversely impact water quality, wildlife, recreational opportunities, drinking water, the community, and the local economy.
This is an important concept to understand. It’s the process of phosphorus being released from the lake’s bottom sediments into the water column when levels of dissolved oxygen are low in the water column (this can also happen during periods of ice cover).
To expand: when dissolved oxygen is plentiful, it binds – at the molecular level – to phosphorus and iron. This iron-bound phosphorus remains “trapped” in the sediment… so long as there’s enough oxygen. When dissolved oxygen is depleted; however, the phosphorus – again, at the molecular level – breaks free from the iron. This “breakup” is called a redox (reduction of oxygen) reaction. The more phosphorus that gets released, the greater the chance an algae bloom will occur and degrade water quality.
This is an important concept to understand. In summary: when dissolved oxygen is plentiful, phosphorus (which is negatively charged) remains bound – at the molecular level – to iron and aluminum (both positively charged). The aluminum-bound phosphorus remains bound to the aluminum, however, iron-bound phosphorus only remains bound as long as there’s enough oxygen.
When dissolved oxygen is depleted; however, the iron-bound phosphorus breaks free. This “breakup” is called a redox (reduction of oxygen) reaction. The more phosphorus that gets released, the greater the chance an algae bloom will occur (because algae eat phosphorus) and result in poor water quality.
How do oxygen levels get low enough to even cause all of this? Read on!
Warm water doesn’t contain as much dissolved oxygen as cool water. This low solubility occurs because of the water molecules’ high kinetic energy, i.e. they’re moving too quickly to “trap” more oxygen as in cooler temperatures.
Warmer water also “sits” on top of colder water due to differences in density. These layers (stratification) result in a temperature barrier (thermocline) that prevents the circulation of dissolved oxygen from the upper to the lower layers of the lake.
Meanwhile, microbes at the bottom of the lake consume dissolved oxygen as they decompose algae, plants and animal matter.
Since the stratification/thermocline prevents new dissolved oxygen from reaching the bottom to replenish what’s been consumed by the microbes, the amount of dissolved oxygen continues to lower. (Low-oxygen conditions are referred to as anoxia/anoxic).
This causes phosphorus to be released from sediment into the water column, where it feeds algae and can result in an algae bloom.
No. Watershed remediation isn’t – by itself – enough to meet the water quality goals in WBMP. While addressing runoff and shoreline erosion is critical to improving water quality within China Lake, in order to meet the water quality goals outlined the WBMP the internal recycling/loading must be addressed.
While it is well know that certain types of algae (Cyanobacteria) can produce toxins that are harmful to people and animals, it is extremely rare to find concentrations of these toxins in Maine Lakes that pose a threat. It is not completely understood what specific conditions lead this algae that produce toxins, however they are more commonly found when a Harmful Algae Bloom is occurring. Thus, by reducing the potential for an algae bloom we are reducing the risk of toxins in China Lake.
More information on this subject can be found on the Maine DEP’s cyanobacteria and cyanotoxins page.
When properly dosed, monitored and applied, no; people can safely recreate in and drink aluminum-treated water.
Aluminum sulfate is commonly used by water treatment facilities, including Kennebec Water District to create drinkable water.
Yes, but recreational boaters should avoid the barge by at least 300 feet to avoid interfering with the treatment.
YES to both!
During treatment, sensors onboard the treatment barge will monitor and apply sodium aluminate to keep the water at neutral pH (between 6 and 8 with a tighter target of 6.5 to 7.5 to minimize impact to fish and other aquatic life).
A second boat will follow behind the barge and test the water as the treatment is applied. If necessary, it will notify the barge to adjust the amount of sodium aluminate to balance pH.
Surveys of fish and other aquatic life will be conducted in the days leading up to, during and after the treatment to monitor their overall health. Any potential impacts to bottom-dwelling species -- such as plants or mussels – would be minimal and not last very long.
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Another potential impact is that increased water clarity may enable plants to grow where they previously couldn’t. Plants – like American waterweed – that get nutrients directly from the water may grow less densely due to reduced phosphorus.
No. Aluminum sulfate binds to phosphorus in the sediments and will not need to be removed. The treatment is focused on inactivating phosphorus in the top 10 cm of the bottom sediments. Over time, new phosphorus from below 10 cm will migrate up through the treated sediment; this is why aluminum treatments often need to be repeated.
Areas 6 m (approximately 20 ft) and greater in depth in the East Basin will receive 20-90 g/m2, depending on exact depth.
6-9m depths (representing 612 acres) will receive the lowest dose (20 g/m2) because it has less available phosphorus.
9-15m depths will receive a dose of 30-50 g/m2.
15-18m depths (representing 48 acres) will receive the highest dose (90 g/m2) because it has the most available phosphorus.
Areas requiring a higher dose will receive lower dose split treatments across multiple days rather than a single high dose treatment to minimize any impact to aquatic life.
The treatment is designed to inactivate phosphorus in the upper 10 cm of lakebed sediment by using a 2:1 ratio by volume of aluminum sulfate and sodium aluminate in ~5% liquid concentrations.
WHY: Determining the correct dose prevents harming the ecosystem and maximizes the treatment’s effectiveness.
HOW: Maine DEP, Colby College and KWD collected 30 sediment samples in both the east and west basins during their 2020 sediment project, followed by eight additional composite (group) sediment samples in the east basin in 2022 to develop the final recommendation in consultation with Maine DEP, CLA, KWD and outside consultants.
Aluminum assays (adding alum to lake sediments in the lab) conducted by Colby College provided critical data for the recommendation, i.e. how much iron, aluminum and phosphorus exist in the sediment, and how sediments from different areas of the lake and different depths respond to different aluminum doses.
WHEN: Over the course of a week after ice out, under calm conditions and when water temperature is over 40 degrees F.
WHERE: In the East Basin, in water 6 meters and greater in depth.
HOW: A barge will apply aluminum sulfate and sodium aluminate from onboard tanks to these areas.
During treatment, sensors on the treatment barge will monitor and apply sodium aluminate to keep the water at neutral pH (between 6 and 8 with a tighter target of 6.5 to 7.5 to minimize impact to fish and other aquatic life).
A second boat will follow behind the barge and test the water as the treatment is applied. If necessary, it will notify the barge to adjust the amount of sodium aluminate to balance pH.
During treatment, sensors on the treatment barge will monitor and apply sodium aluminate to keep the water at neutral pH levels (between 6 and 8 with a tighter target of 6.5 to 7.5 to minimize impact to fish and other aquatic life).
A second boat will follow behind the barge and test the water as the treatment is applied. If necessary, it will notify the barge to adjust the amount of sodium aluminate to balance pH.
Aluminum sulfate will be provided by GAC Chemical in Searsport, ME.
Sodium aluminate will be provided by Holland Co. in Adams, MA.
A company experienced in conducting aluminum treatments in Maine will be contracted to apply the alum.
The selected location (TBD) will serve as the holding area for the chemicals (2-3 large tanks 10 feet in diameter x 15 feet tall holding 7,000 gallons) in order to refill the barge’s onboard tanks. The barge will be refilled multiple times daily over the course of the treatment using the tanks, and the tanks will be refilled multiple times daily by 62 foot-long chemical trucks.
Significant progress with watershed management in the first four years is necessary to receive state/federal funding to support an alum treatment, and to allow enough time to raise the necessary funds, as local funds will also be needed to offset the costs of the treatment.
The 2022 Watershed Plan’s Steering Committee developed a project calendar outlining the timing of public meetings, permitting, and treatment. Permitting takes 90 days once submitted to Maine DEP. The current plan is to apply for a permit in 2024 for approval in 2025 to get contractors and consultants lined up for treatment in 2026.
China Lake periodically experiences low levels of dissolved oxygen, which allow phosphorus to escape lakebed sediment and become food for algae. An aluminum treatment is expected to work because it has proven to be very effective in this scenario.
Aluminum treatments have been conducted on over 250 lakes worldwide; between 1978-2022, nine alum treatments in Maine have been performed on eight lakes, with no adverse impacts. Immediate improvement was noticed in most; older treatments provided benefits for over 20 years.
China Lake has a complex ecosystem, so treatment may not be as effective or last like research/models indicate. This is why continued watershed remediation is important; less phosphorus runoff means less phosphorus build-up in lakebed sediment, extending the treatments’ effectiveness.
Another (low) risk is the water could become too acidic (pH lower than 6.5) or too alkaline (pH higher than 8.2) during treatment. To mitigate this, a second boat will follow behind the barge and test the water as the treatment is applied. If necessary, it will notify the barge to adjust the amount of sodium aluminate to balance pH.
NOTE: There have not been any fish kills in Maine caused by aluminum treatments in over 20 years, due to the improvements in dosing determination and application.
Yes. In a 1994 analysis performed by an independent contractor, the failure of Threemile Pond’s 1989 aluminum treatment was attributed to poor timing, misapplication, and insufficient/improper dosage of aluminum sulfate (deeper parts of the lake should have received a higher dose and the shallowest parts should not have been treated at all.)
China Lake’s treatment plan has been thoroughly researched including two rounds of sediment analysis; aluminum sulfate and sodium aluminate (used to keep pH levels neutral) will be applied properly to avoid failure.
Although dead plants contribute to the lake’s internal load of phosphorus, the amount isn’t significant enough to negatively impact treatment.
By only treating the East Basin (as recommended), phosphorus concentrations will be reduced by at least ~40% in the East Basin and ~20% in the West Basin, if not more.
According to research, the aluminum treatment will result in 90% decrease in the internal phosphorus load in China Lake’s East Basin.
The aluminum treatment is estimated to remain effective for ~20 years (based on treating the top 10 cm of sediment). Success depends on proper dosing and application as well as continued watershed remediation efforts to maximize the treatment’s lifespan.
Between 1978-2022, nine alum treatments on eight lakes in Maine have been performed with no adverse impacts. Immediate improvement was noticed in most; older treatments provided benefits for over 20 years.
No. The alum will be deployed to water depths greater than 6 meters; beyond the reach of motorboats.
In short: an aluminum treatment is a way to prevent internal recycling/loading of phosphorus in lakebed sediments so it can’t become food for algae, thereby greatly reducing the chances of algae blooms.
To expand: aluminum treatments involve adding a carefully measured dose of aluminum sulfate – one of aluminum’s alum forms (and yes, this is why the treatment is often referred to as an “alum” treatment) – and sodium aluminate (to keep pH levels neutral during treatment) to the water.
Aluminum sulfate binds – at the molecular level – to phosphorus. Afterwards, water quality rapidly improves since there’s less phosphorus available for algae to consume.
A two-prong approach:
1. Reducing the amount of phosphorus that gets into the lake from the surrounding watershed AND 2. Conducting an aluminum (alum) treatment to stop the internal recycling/loading of phosphorus.
One of aluminum’s “alum” forms, consisting of aluminum, sulfur and oxygen. It is commonly used by water treatment plants, including Kennebec Water District to create drinkable water.
The alum commonly found on grocery store shelves is a different compound – it’s potassium aluminum sulfate.
Sodium aluminate is a compound of sodium, oxygen and aluminum. It is used to balance pH levels in water, and is applied in conjunction with aluminum sulfate during an aluminum treatment.
Kennebec Water District is working with Maine Department of Marine Resources to monitor the number of alewives entering/leaving China Lake and collect water quality data to analyze the effects of their reintroduction.
Some models suggest alewives could decrease phosphorus while others suggest they could increase phosphorus as the result of eating zooplankton (which eat algae).
Although the extent of these interactions and their actual effect is currently unknown, it’s likely that alewives have little to no impact on water quality.
Although extremely effective at removing phosphorus from a lake, dredging is also extremely expensive ($50,000 per acre foot). Furthermore, acquiring the necessary permits and disposing of dredged sediments can be difficult and expensive.
As a result, this option was not recommended for China Lake.
Pumping oxygen into the lower layer of water in the lake (hypolimnion) is called hypolimnetic oxygenation.
It was successful in the Androscoggin River and could increase oxygen levels by 75% in China Lake; however, it’s extremely cost prohibitive (~$4 million to install necessary structures with additional, annual operating costs of $450,000) and permitting is difficult.
Additionally, anchors, fishing lines or other objects can get caught on the structures.
As a result of these challenges, this option was not recommended for China Lake.
Removing water from the lower layer of the lake (hypolimnion)is called hypolimnetic withdrawal. For any noticeable change (within a reasonable amount of time) to occur, the lake would become destratified. If removed more slowly to preserve stratification, it would take decades to see desired results.
This method was researched by a KWD consultant in 2012 and determined infeasible, as either outcome is undesirable.
KWD and Colby are interested in monitoring the Hunter Book outlet, which is the watershed’s largest sub-drainage area. The northeastern portion of the East Basin (near the Hunter Brook outlet) is where the greatest amount of sediment-released phosphorus was measured.
On a per acre basis; however, research shows that smaller drainages – such as the shoreline of both basins and some smaller unnamed drainages in the West Basin with denser development – are currently contributing high levels of phosphorus, so would likely benefit more from targeted watershed remediation.
Alum dosing stations (as they’re called) can be effective, but are usually only recommended for urban sites that can’t otherwise be improved through watershed work.
China Lake – on the other hand – is not an urban site and has a fair amount of open land. As such, there are many other opportunities to reduce external phosphorus loading from the watershed before needing to consider a tributary aluminum dosing station.
Data obtained by others could help with long-term monitoring of water quality/improvement after implementing the plan and/or address possible issues in the future.
Glossary
Additional Reading
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Alum Treatments to Control Phosphorus in Lakes - Wisconsin Dept. of Natural Resources
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China Lake Watershed Based Management Plan (WBMP)
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Dissolved oxygen – USGS
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Dissolved oxygen – US EPA
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Harmful Algal Bloom – US EPA
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Harmful Algal Blooms and Cyanotoxins in Maine - Lake Stewards of Maine
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Phosphorus Primer for Maine’s Lakes - Colby College
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Seasonal Changes in Water – USGS
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The Use of Alum for Lake Management - North American Lake Management Society
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What Role do Soil and Sediment Play in Damping or Enhancing Eutrophication?
Since China Lake’s Watershed-Based Management Plan (WBMP) was launched, many questions have come up regarding its recommendation for an aluminum (alum) treatment.
Certain answers to these questions require understanding the lake’s ecosystem and background science, which we know can be daunting. Fortunately, we’re here to help! This FAQ has been curated with thoughtful information and explanations.
Click the tabs located above to view respective FAQs.
Questions? Contact us!