Monitoring

The most important part of any restoration project is proper data collection. We develop and implement monitoring plans for all types of surface waters. Often the assessment method (modeling) drives what type monitoring is required. Some of the monitoring we conduct:

  • Sediment: nutrients, metals, benthic invertebrates
  • Water: nutrients, plankton, profile measurements of temperature, oxygen, etc.
  • Flow: propeller and float methods
  • Climate: Temperature, wind, solar radiation, and more with on-site weather stations (Tempest©️)

Modeling and assessment

Proper assessment goes hand-in-hand with monitoring. In most cases, dynamic modeling will give the best results, but it is important to ensure that a proper monitoring plan is created to maximize modeling results while minimizing uncertainty (error).

  • Mass balance (black box) models: somewhat lower data requirements but greater uncertainty, generally suitable for very small (<1 ha) water bodies
    • Often on a monthly time scale
    • Single point estimates used to create averages between sampling periods
    • Internal nutrient sources are can only be estimated
  • Dynamic (mechanistic) models: suitable for all water bodies, ranging from one (surface to sediment) to three dimensions (vertical and horizontal)
    • Can be developed with as short as an hourly time-step
    • Increased resolution that can capture shorter duration events like pH and oxygen decreases during night
    • Internal nutrient sources, and how they affect changes in water quality are modeled

Recommendation and design of measures

Based on the nutrient loading assessment and lake specific conditions, we recommend the restoration measures that are most cost-effective and sustainable. Then we design the measures chosen by the client. Proper design ensures safety during implementation while maximizing effectiveness and lowering cost. Some of the measures we work with include:

Internal measures

  • Mineral (aka chemical) treatment: lake and sediment treatment using nutrient binding minerals (aluminum, iron, and calcium)
    • Geochemical modeling of a future treatment to ensure safety
    • Binding efficiency modeling to maximize nutrient inactivation and minimize the amount of material needed
  • Dredging: removal of lake sediment using different dredging methods (hydraulic, low flow, etc.)
    • Pre-dredging studies to determine depth distribution of nutrients and potential pollutants
    • Dewatering and treatment of sediment before transport
    • Reuse planning based on the properties of the dredged sediment
  • Aeration: oxygenation of bottom water to improve sediment binding of nutrients
    • Aeration type: air or oxygen entrainment, bottom water diffusion, etc.
    • Determination of the nutrient binding capacity of the sediment (for example, how much phosphorus can the sediment bind)
    • Assessment of the need for increased binding capacity to maximize aeration results
    • Determination of oxygen demand and optimal placement

External measures

  • Permeable reactive barriers: these types of devices are designed to remove nutrients from water as it moves horizontally through a system.
    • One example is a permeable, limestone barrier we designed using granular limestone to reduce phosphorus as water moved through a wetland
  • Enhanced sand filters: filters enhanced with materials like iron to reduce nutrients in stormwater runoff
    • An example of this type of system is the iron enhanced (5%) sand filter we designed using reused iron filing to reduce nutrients in stormwater runoff
  • Drinking water treatment residual (DWTR) filters
    • An innovative method that reuses DWTRs in a filter to remove phosphorus and other nutrients from runoff. These types of filters are still experimental, with the first being designed in the US using spent lime. Research is ongoing to optimize both the pre-treatment method and design variables needed to maximize nutrient removal