MUS

Advanced Service Areas:

Please contact AGT for information and click on the links below to learn more.

• Design, Implementation and Monitoring of MUS Systems

• Performance Assessment, Redesign, and Revitalization of MUS Systems

• MUS Site Selection, Aquifer Parameter Estimation and Geophysical Surveys

• Pilot Testing (Proof of Concept) for MUS Systems

• Predictive Modeling of Geochemical and Biological Changes to Native and Introduced Water

• Laboratory Analysis of Mixing Water

• Simulate Impact of MUS Systems on Surface Water

• Stream Flow Augmentation Assessment and Design

• Modeling to Predict Recovery Efficiency

• Infiltration Modeling

• Investigate and Remediate Contaminated MUS Systems

• Waste Water and Storm Water Reuse as Input to MUS System

• Permit Application Preparation, Regulatory Relations

Design, Implementation and Monitoring of MUS systems

Design of MUS systems typically requires careful consideration of four major technical inputs. Design criteria include:

1. Source of water to be stored, e.g. river water, community effluent, storm water.

2. Recharge method, e.g., vadose zone wells, recharge wells, recharge basin.

3. Storage Site/Zone selection and management approach, e.g., aquifer type, geology, geochemistry considerations.

4. End use of recovered water e.g., potable, irrigation, industrial, seasonal supply, emergency/strategic supply

Each component of the MUS design may require engineering, geochemical, cultural, geologic, and legal considerations. 

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Performance Assessment, Redesign, and Revitalization of MUS systems

For a variety of reason (engineering, geologic, geochemical, societal, legal), sometimes the design of a water management system needs to be reviewed and modified. A reengineering or revitalization effort may be done to meet new performance criteria, or correct a continuing degradation in system production. AGT can assess the performance of your MUS system, compare operating parameters with design objectives and, if necessary, prepare reengineering and/or revitalization specifications. In addition, AGT can work closely with your regional planners to understand projected population and/or industrial growth to ensure the MUS system is upgraded to meet projected water needs.

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MUS Site Selection, Aquifer Parameter Estimation and Geophysical Surveys

To design a storage reservoir, engineers and hydrogeologists must have a good understanding of the hydrological properties of the aquifers to be used for storage and of the hydraulics. In particular, a successful MUS system design is predicated on answers to the following questions about the aquifer physical system and its hydraulics (including factors affecting success as listed by ASCE, 2001; Bouwer, 2002; NRC, 2008)

• What are the spatial constraints for the aquifer (basin extent, basin depth, aquifer thickness, interbeds, other boundary conditions)?
• What geological units are available for storage, and what are the hydraulic properties of these units?
• What temporal variations will affect the system (seasonal, climatic)?
• What are the short- and long-term impacts of the MUS system on the aquifer matrix, groundwater flow, or surface waters?

Factors which can preclude MUS development include:

• Low aquifer storage,
• Low hydraulic conductivity,
• High probability of clogging during recharge,
• Anticipated loss of recharge water,
• Anticipated degradation of water quality due to physical, chemical or biological processes,
• Changes in patterns of potentiometric gradients that would adversely affect existing water supplies.

AGT’s scientists can perform a variety of investigation activities to assess site physical and chemical suitability, and provide data for MUS system design. Examples of investigation methods/technologies include:

• Aquifer testing (pumping, slug, laboratory)
• MUS Cycling/Feasibility/Pilot Testing with monitoring for recovery efficiency
• Tracer testing
• Geophysical analysis (surface/airborne/borehole) (seismic reflection/refraction, EM, GPR, resistivity)
• Remote sensing (satellite and aerial photographs, magnetic, gravity, EM reflectivity)
• Groundwater Flow and Transport Modeling (analytical and numerical codes) (1D, 2D, and 3D) (saturated and unsaturated flow) (MODFLOW, MT3DMS, SEAWAT, HST3D, RT3D, SUTRA, FEMWATER)
• Geographic Information Systems and DBMS
• 3D Hydrogeologic and lithostratigraphic visualization/graphic development 

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Pilot Testing (Proof of Concept) for MUS Systems

A pilot test is a carefully controlled evaluation covering a limited area of proposed MUS aquifer, to assess the feasibility of MUS System success. The following are examples of components addressed in a typical pilot test (NRC, 2008).

• Pilot program goals
• Soil borings
• Tracer tests
• Monitoring
• Valve testing
• Surface infiltration rates
• Injection well recharge rates
• Pretreatment evaluation
• Modeling evaluation
• Risk Assessment

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Predictive Modeling of Geochemical and Biological Changes to Native and Introduced Water

Computer modeling of MUS systems is crucial to understanding the potential changes to – and effects from - the surrounding environment. AGT’s scientists have extensive experience building sophisticated two and three dimension computer models to derive MUS system design parameters, and predict system response. Models are used to assess the hydraulic, geochemical, and biologic changes. 

• Answers to typical questions, such as those listed below, can be developed:
• How will the aquifer respond under storage stresses?
• How much waster can be stored in an aquifer?
• What are the hydraulic, geochemical, and biologic changes associated with the MUS system?
• What is the most efficient technology for delivery of storage water, e.g., injection wells or recharge basins, or a combination of both?
• What chemical changes may occur when stored water is placed in contact with native (existing) groundwater? 

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Laboratory Analysis of Mixing Waters

A comprehensive geochemical conceptual model is crucial to predicting the evolution of storage and native waters. The conceptual model is used to characterize the chemical (organic and inorganic), physical, and microbiological evolution of the water (NRC, 2008). The monitoring and analysis that are consistent with this characterization must focus on both constituents of concern to human health and those that affect operations of the MUS system. The consequences of the potential reactions during storage underscore the importance of a comprehensive aquifer characterization to fully understand the water quality changes that may occur during MUS. AGT’s scientists use geochemical models to simulate the chemical evolution of water, and validate/support model findings with laboratory analyses of waters involved.

AGT has access to a global network of qualified chemistry laboratories. Chemistry data are obtained in a variety of formats, including electronic files for efficient transfers of data to visualization software and analysis routines.

Typical MUS Chemical Parameters:

Ca²⁺
Mg²⁺
HCO₃^-
Na⁺
SO₄ ²
SiO₂
Cl^-
Eh
pH
Specific conductance
Temperature
Dissolved oxygen
Nutrients
Metalloids (including arsenic)
Mn, Mo, Fe, Ni, Co, V
Trace organics
Total organic carbon
Water treatment disinfection by-products
Microorganisms

The chemical analyses performed may change based on site-specific conditions and the origin of injection/recharge waters. 

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Simulate Impact of MUS systems on Surface Water

AGT’s scientists use advanced numerical and analytical modeling to simulate the effects of MUS on the hydrology around the storage area. Specifically the models predict changes in the flow system, and effects of recharge to, discharge from, and total flow volume in near-by streams and lakes. 

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Stream Flow Augmentation Assessment and Design

Where the quantity of surface water stream flow may be reduced by groundwater extraction or surface water diversion (e.g., for drinking or irrigation), MUS has successfully been used to store water and replenish flow volume. AGT can assess options for stream flow augmentation and design a MUS system to help ensure minimum required flow volumes are met.

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Modeling to Predict Recovery Efficiency

The understanding of the fate of recharged water is crucial to measuring the performance of a MUS System. Recovery efficiency (RE) broadly reflects the proportion of water recovered and can be effected by a variety of geologic, hydrologic, and climatic phenomena, such as:

• Stored water seeping into near-by stream as baseflow,

• Stored water infiltrating downward to recharge an underlying aquifer,

• Increases water levels in an unconfined aquifer facilitating loss through increased evapotranspiration.

AGT’s scientists use numerical models of the MUS System to simulate water storage and recovery operations, conducting mass balance and sensitivity analyses to evaluate the integrity and potential recoverability of stored water. During pilot testing, AGT conducts cycling testing (series of injection and withdraw test) to collect additional feasibility information for comparison to modeling results. In cases where field data and modeling results poorly correspond, AGT can gain insight into the hydrodynamics of the MUS-aquifer system and modify the engineering and/or operating parameters of the System as warranted to seek system optimization. Modeling results and field data are periodically updated and compared in an iterative performance assessment process. 

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Infiltration Modeling

Surface infiltration systems require permeable soils and vadose zone to get the water into ground and to the aquifer, and unconfined and sufficiently transmissive aquifers to allow for lateral flow away from the infiltration systems without excessive groundwater mounding. If artificial recharge causes rise of groundwater mound in the aquifer high enough, it can reduce the infiltration rates of artificial recharge system. The most reliable way to calculate groundwater mound beneath recharge basin is to use calibrated groundwater models. Also, use of inverse models during calibration of groundwater models is highly recommended. Inverse models can be used as tool to estimate uncertainty in prediction of groundwater models as the most important topic in groundwater modeling. Pump and slug test can be used in order to obtain representative values of parameters.

Some of the questions that managers and operators would like to know are:

• How much water can be stored in aquifer

• Will the area become waterlogged

• How the drying period will influence the capacity of nearby discharging wells

• Where the groundwater mound be 20 or 50 years from now.

All these questions can be answered using mathematical models. Saturated groundwater models are usually used (like famous MODFLOW) or for more precise data unsaturated models can be used (MODFLOW SURFACT ex.).

Simple 3D unsaturated-saturated model using Modflow Surfact.

If unsaturated models are used, additional data is required, like Van Genuchten parameters that gives relation between soil water content and hydraulic properties of vadose zone.

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Investigate and Remediate Contaminated MUS systems

Sometimes MUS systems become contaminated, either by geochemical reactions between stored and native water, or by the introduction of an industrial chemical. AGT can investigate the occurrence and distribution of contaminants in a MUS system. If necessary, a human health risk assessment can be performed to assess the potential impacts to consumers. In cases where remediation of the MUS system is necessary (e.g., to protect public health, meet government water quality regulations, or lower business risks), AGT can design and implement a remediation plan to correct the problem.

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Waste Water and Storm Water Reuse as Input to MUS System

Sometimes sewage effluent can be an important source of water for agricultural, irrigation, commercial, and for potable use. Non-potable purposes such agricultural and urban irrigation (lakes, golf courses, sport fields) are usually use more water versus potable purposes. Before applying recharge water via recharge basins or other surface infiltration facilities, waste water (sewage) effluent is usually given primary and secondary treatment and disinfection with chlorine. In primary treatment all that floats or sinks is removed. Secondary treatment is a biological process where bacteria degrade organic compounds in aeration tanks. Tertiary treatment consists of sand filtration and disinfection. 

When water quality improvement is the main objective of recharge with sewage effluent such systems are called soil-aquifer-treatment (SAT) systems. With SAT systems typically all suspended solids and micro-organisms are removed. Also, nitrogen concentration is greatly reduced by denitrification, dissolved organic carbon and most phosphate and metals are also removed from water. 

Recovery wells near-by SAT systems can pump 100 % reclaimed water but alternatively the wells can be located to pump a mixture of reclaimed water and natural groundwater. Water from wells are basically pathogen free and can be used for purposes like irrigation, golf courses, fire protection etc. The main reason that this water cannot be used for drinking as such is the presence of residual organic carbon, which consists of wide spectrum of synthetic organic chemicals. In California it is set upper limit of 1mg/l for total organic carbon content after SAT. 

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Permit Application Preparation, Regulatory Relations

AGT’s experienced groundwater professionals can prepare permit applications for your MUS system, for submittal to the appropriate regulatory agencies. AGT’s scientists are a technical resource for you and, at your request, can be present at meeting with government regulators or public representative, to answer questions concerning the design and safety of your MUS system.

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