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Keywords:

  • Exempt well;
  • ASR;
  • rain harvesting

Abstract:

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

The water management practice of storing water underground for use during dry periods is a very effective technique that has been practiced for a long time. Another water management practice that has been around for a long time is collection of rainwater and storage of rainwater aboce ground. There have been significant advances more recently in our understanding of aquifer geology and technologies used for rainwater harvesting. This article combines our advance in knowledge of storing and recovery water from wells and new rainwater harvesting practices to recharge a low yielding exempt well with treated rainwater. The studies presented in this article demonstrate that exempt wells provide a valuable underground water storage option and may provide a new effective urban water management tool.

Oregon's expanding population has led to a drastic increase in water demand and degradation of water and air quality. The state's surface water is fully allocated for most of the year, prompting many water users to turn to ground water to meet increasing water demands. In some areas of Oregon, the ground water is being consumed faster than it is being replaced. The study described in this article attempts to address how to best balance ground water use with recharge of ground water using exempt wells. Exempt wells provide a water management tool that allows water to be stored underground during times when precipitation is plentiful. Below-ground water storage in exempt wells can then be used during the drier times of the year when water demand increases.

Starting in 2007, three low-yield exempt wells in Oregon's Southern Willamette Valley (Figure 1) were evaluated to determine whether an existing domestic single-purpose exempt well could also be used as a dual-purpose well. A single-purpose well is only used to withdraw water for beneficial use and a dual-purpose well is used to recharge the ground water supply and recover water for beneficial use. In these pilot studies, three exempt wells were used as dual-purpose wells. All three exempt wells were low yield wells, and domestic water use routinely exceeded the ability of the well to supply enough ground water for domestic water demand. Oregon's unique regulatory framework for exempt wells and rainwater contributed to the success of these pilot studies. Harvested rainwater from a rooftop supplied high quality source water for each dual-purpose exempt well. The exempt wells in this study were recharged with treated rainwater when precipitation was plentiful, and the stored recharge water was recovered during the summer.

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Figure 1. Location of exempt ASR well pilot study.

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Converting the three single-purpose exempt wells in this study to dual-purpose exempt wells improved ground water quantity and quality. The use of an exempt well was shown to be an effective water management tool. Continued studies of how to most effectively and efficiently implement this type of water management tool on a larger scale is needed. In this article the potential of dual-purpose exempt well use in urban areas is explored. The use of dual-purpose exempt wells to augment municipal water systems could help balance declining ground water levels, reverse degradation of water quality, and improve air quality.

Exempt Wells As a Water Management Tool

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

Since most of the surface water in Oregon is fully allocated during summer months, there is very little left over for new uses. However, surface water in the state is available in the winter months. Ground water development remains an option for most Oregonians, but the scope of opportunities is shrinking. In some areas of Oregon, ground water level measurements have shown a significant decrease and have been administratively designated ground water management areas, which can restrict development. Development may also be limited or prohibited if a well is installed in proximity to a fully appropriated surface water source.

According to the 2011 Oregon Water Resources’ (WRD) Integrated Water Resource Strategy, Oregon historically has relied on stored water from the springtime snowpack runoff to meet competing water demands. Melting of the snowpack is sensitive to temperature, which is predicted to increase in Oregon as the Earth's climate changes. Higher temperatures in winter would cause a greater percentage of rain to fall versus snow, leading not only to less snow but to earlier snowmelt. The state's historical ability to store water in the snowpack could change, meaning Oregonians would have to stretch their water resources even thinner during the summer. Storing water underground when precipitation is plentiful and rivers are at high levels helps ensure that precipitation that falls in Oregon stays in Oregon for beneficial use. Harvesting of rainwater from rooftops, treatment and injection of this water to recharge exempt wells takes advantage of this valuable clean-water resource. Storing harvested rainwater underground using exempt wells keeps high quality rainwater in beneficial use within Oregon, generates multiple benefits for the environment, and provides another water management tool.

Oregon's Rules Support Dual-Purpose Exempt Wells

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

In Oregon, all water from every supply source belongs to the public. However, rainwater collected from impervious surfaces is not considered a supply source and therefore is not regulated by the Oregon WRD. Also, exempt well owners in Oregon are exempted from applying for a water right permit. In the three pilot studies, rainwater was collected from impervious surfaces and used as the supply source for the dual-purpose exempt well. All three property owners in the studies withdrew ground water from an exempt well, which was used for domestic use (less than a half-acre non-commercial lawn and garden), and was less than 15,000 gallons per day.

This study investigated the feasibility of using an exempt well as a dual-purpose well, also known as an Aquifer Storage and Recovery (ASR) well (Figure 2). Large-scale ASR projects are jointly regulated by the Oregon WRD, the Oregon Health Authority-Drinking Water Program (OHA-DWP) and the Oregon Department of Environmental Quality-Water Quality Program (DEQ-WQP). The Oregon WRD regulates licensing, permitting and water right regulations of large ASR projects, including the source water diverted from one source (typically surface water) and the permitted ASR well being used for subsurface injection of the source water.

image

Figure 2. Storage and recovery of treated stored rain in exempt ASR well.

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An ASR well is a water management tool that can be used to better match water supply with water demand. ASR wells have been used by the public in the United States for more than 40 years as a way to store fresh water naturally underground (Pyne 2005). Other countries throughout the world have been utilizing ASR wells for even longer. Instead of constructing large water storage tanks, public water systems have been using ASR wells as a large underground reservoir to store millions of gallons of treated drinking water. Large-scale ASR systems are also being used in commercial irrigation operations.

Since the Oregon WRD does not require water right permits for rainwater or exempt wells, the small scale ASR projects in these pilot studies were regulated under the DEQ-WQP's Underground Injection Control (UIC) program. Under the UIC program's ground water quality protection requirements, all water injected into exempt wells must be of drinking-water quality. Each exempt ASR well in the study required submission of a UIC application to the DEQ for authorization by rule. The unique regulatory framework that applies to both rainwater and exempt wells in Oregon made the pilot studies and future projects possible. These same exempt ASR well rules apply to exempt well owners in urban areas.

Subsurface Geology of Pilot Study Exempt Wells

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

According to the 2009 Oregon Water Supply and Conservation Initiative (OWSCI): Inventory of Potential Below Ground Storage Sites, the aquifer type in which the three exempt wells are located is the Eugene Area Middle-Early Tertiary Volcanic and Volcaniclastic Rock Aquifer. This aquifer is made up of tuffaceous sandstone, typically considered a low-producing aquifer. The hydraulic conductivity in this type of aquifer is less than 1 foot per day. All wells in the study were low-yielding wells, with observed natural recharge rates below ¼-gallon per minute. The depths of the exempt wells in the study were 200 to 300 feet. Despite the low hydraulic conductivity of this type of aquifer there is still a great potential for storage of recharge water below ground. The aquifer properties also tend to slow the movement of the stored recharge water from the well, which improves the ability to recover the stored recharge water. A monitoring well was located about 143 feet from pilot study #1's exempt ASR well, and no ground water level changes were noticed in the monitoring well during recharge or recovery of the well.

In the 2009 Oregon-wide inventory, the aquifer in which these exempt wells were located was considered less capable of accepting water into storage. The aquifer lowers the feasibility of installing a large-scale ASR system that needs to be capable of injecting at high recharge rates and have the ability to store millions of gallons of water underground annually. The exempt ASR well provides an alternative small-scale method of storing recharge water in this type of aquifer. By recharging multiple exempt ASR wells at lower recharge rates, the sum of these underground pockets of stored water could add up to similar quantities of water stored underground in large-scale ASR systems.

Source Water Quality for the Exempt ASR Well System

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

In this study, exempt ASR wells were used to store thousands of gallons of treated rainwater underground. The rainwater was collected from rooftops using best management practices and water treatment methods as outlined in Table 1. The rainwater harvested from roof collection surfaces provided consistently high-quality source water. As with any type of water treatment process, source water quality is critical. In each of the three pilot studies, the rainwater collected from metal or asphalt rooftops provided exceptionally high-quality source water for treatment. The source water provided by the harvested rainwater was simple to treat and low in mineral content. The rainwater did not need the addition of treatment chemicals to reach drinking water quality and provided excellent injection water for recharge of an exempt ASR well.

Table 1.  Best Management Practices (BMPs) for exempt ASR wells.
Step 1 Follow exempt well owner BMPs
Step 2 Follow exempt ASR well system BMPs
Step 3 Maintain clean rainwater catchment surface
Step 4 Maintain clean rainwater delivery system gutters
Step 5 Install screen over gutters
Step 6 Operating First Flush System: Prevents portion of first roof runoff from entering tanks
Step 7 Install screen over intake to rainwater storage tank
Step 8 Install protection over vents and openings to stored rainwater
Step 9 Allow particles in rainwater to settle in storage tank
Step 10 Filter rainwater through coarse sediment filtration
Step 11 Filter rainwater through fine sediment filtration
Step 12 Filter rainwater through an adsorbing filter that reduces odor, color, and organic chemicals.
Step 13 Disinfect with ultraviolet (UV) light system
Step 14 Install power outage or UV bulb failure injection shutdown control

In pilot study #1, rainwater was collected from a metal roof surface. The water quality results in Table 2 describe the harvested rainwater as very soft and low in mineral content. These results also illustrate harvested rainwater's exceptionally high water clarity (low turbidity). The rainwater provides low mineral content and exceptionally clear source water, which makes it ideal for water treatment and recharge of an exempt ASR well. Eight heavy metals were tested in rainwater from metal and asphalt roof surfaces, but none were detected. The total organic carbon of the untreated harvested rainwater tested very low, and the lead and mercury results of the rainwater from an asphalt roof were undetectable.

Table 2.  Water quality results for untreated harvested rainwater.
AnalyteResultsRangeUnitsRoof Type
Alkalinity20.00< 125mg/Lmetal
Calcium3.00< 75mg/Lmetal
Hardness10.00< 120mg/Lmetal
pH6.80 SUmetal
Total Dissolved Solids11.00< 500mg/Lmetal
Turbidity0.21< 1NTUmetal

Recharge Water Quality for the Exempt ASR Well System

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

In the three pilot studies, the rainwater was collected from either a metal or asphalt roof type. To ensure native ground water protection at the study sites, additional water quality testing was required by the Oregon DEQ-WQP for the treated rainwater. The treated rainwater was used as injection water or recharge water for the exempt ASR wells in the pilot studies. The microbial safety of the injection water was confirmed by testing for total coliform and E. coli, which is the standard method used by public water systems to indicate whether pathogens are present in the water. The microbial quality of the treated rainwater tested biologically safe by drinking water standards. The total coliform bacteria and E. coli were absent in the treated rainwater samples.

The DEQ-WQP required testing for heavy metals in the treated rainwater from both the asphalt and metal roof types. The state also required that the asphalt roof type be tested for Northwest Total Petroleum Hydrocarbon-Hydrocarbon Identification (NWTPH-HCID) suites and Polycyclic Aromatic Hydrocarbon (PAHs). Our water quality testing results from the pilot studies indicate that having either a metal or asphalt roof surface provides high-quality treated rainwater for injection or recharge in an exempt well. None of the contaminants or heavy metals were detected. In some studies, air quality was shown to impact harvested rainwater quality. Much of the research that analyzed the harvested rainwater quality for a variety of roof surfaces, including asphalt roofs, found that the air quality in heavily industrialized areas was a significant contributing factor in the water quality of the rainwater harvested (Chang et al. 2004). These three pilot studies were located in rural settings over 10 miles from the metro area of Eugene-Springfield, Oregon.

Water Quality of Exempt Well Native Ground Water and Stored Recharge Water

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

Both water quantity and quality were important to measure throughout the pilot studies. The ability of the exempt well to store the treated rainwater used to recharge the well could be determined with this data. In all three pilot studies, the volume of the stored and recovered treated rainwater of the exempt ASR well was recorded. Naturally occurring minerals commonly found in ground water were monitored throughout the recharge, storage and recovery phases of the exempt well. Ground water typically has much higher levels of dissolved minerals than rainwater. Different rocks (e.g., sandstone, limestone and basalt) all have different minerals; therefore, ground water in contact with these materials will have different compositions. The ground water concentration level is dependent on the length of time the ground water is in contact with subsurface geological material, the temperature of the ground water, the pH and the oxidation reduction potential of the ground water (Nelson 2002).

In 2011, water samples were collected from the pilot study #1 site. About 9,600 gallons of treated rainwater were injected into the exempt ASR well on site. After about 2,900 gallons of the water were recovered for domestic use, water samples were collected. The samples are representative of the 6,700 remaining gallons of stored recharge water, which is a blend of treated rainwater and the native ground water from the well. Table 3 describes the water quality impact of storing treated rainwater in this exempt well.

Table 3.  Water quality results pilot study #1 Exempt ASR Well using a metal roof. Units are in mg/L.
AnalyteTreated Rainwater ResultsNative Ground Water ResultsStored Recharge Water Results
  Recharge Water Before Recharge After Recharge
  1. * The alkalinity and arsenic samples were taken during separate sampling events from the other results presented.

  2. ** The native ground water arsenic level in this table was 0.013 mg/L in 2008, and in 2011 the level dropped to 0.0059 mg/L.

Alkalinity18.00240.00150.0*
Arsenic0.013**0.0098*
Bicarbonate13.00228.00
Calcium3.604.803.2
CarbonateND12.00
ChlorideND6.300.3
Hardness10.0012.008.0
MagnesiumNDNDND
Potassium0.550.600.6
Silica0.506.002.0
Sulfate6.005.004.0
Total Dissolved Solids22.00340.0040.0

In 2010, water samples were collected from the pilot study #2 site. About 10,600 gallons of treated rainwater were used to recharge the exempt well on site. After about 450 gallons were recovered for domestic use, water samples were collected. The samples are representative of the 10,150 gallons of remaining stored water, which is a blend of treated rainwater and the native ground water from the well. Table 4 illustrates the water quality impact of storing treated rainwater in this exempt ASR well.

Table 4.  Water quality results for pilot study #2 exempt ASR well using an asphalt roof. Units are in mg/L.
AnalyteTreated Rainwater ResultsNative Ground Water ResultsStored Recharge Water Results
  Recharge Water Before Recharge After Recharge
  1. * The chloride and sulfate samples were taken during separate sampling events from the other results presented.

Alkalinity18.0166.0128.0
Bicarbonate13.0166.0128.0
Calcium4.040.034.4
CarbonateNDNDND
Chloride0.48.40.6*
Hardness10.0128.090.0
MagnesiumND6.81.0
Manganese0.48ND
NitrateNDND
Potassium0.552.30.6
Silica0.510.73.25
Sulfate6.07.0*
Total Dissolved Solids22.0440.0260.0

In 2010, water samples were collected from the pilot study #3 site. About 4,300 gallons of treated rainwater were used to recharge the exempt well on site. After about 1,300 gallons were recovered for domestic use, water samples were collected. The samples are representative of the 3,000 gallons of remaining stored water, which is a blend of treated rainwater and the native ground water from the well. Table 5 illustrates the water quality impact of storing treated rainwater in an exempt ASR well.

Table 5.  Water quality results for Pilot Study #3 exempt ASR well using a metal roof. Units are in mg/L.
AnalyteTreated Rainwater ResultsNative Ground Water ResultsStored Recharge Water Results
  Recharge Water Before Recharge After Recharge
  1. * The sulfate sample was taken during a separate sampling event from the other results presented.

Alkalinity18.0280.052.0
Bicarbonate13.0280.052.0
Calcium4.025.05.6
CarbonateNDNDND
Chloride0.45.01.1
Hardness10.068.014.0
IronND0.15ND
MagnesiumND2.0ND
Manganese34.0ND
NitrateNDND
Potassium0.552.00.5
Silica0.534.0ND
Sulfate6.07.0*
Total Dissolved Solids22.0480.090.0

The mineral content of treated rainwater was lower than the ground water of the three pilot study exempt wells. In all three pilot studies, the natural mineral levels of these exempt ASR wells decreased when treated rainwater was used to recharge them. These lower mineral levels indicate that the treated rainwater recharged the exempt ASR wells. The exempt ASR well acted as a large reservoir to store thousands of gallons of recharge water. If the treated rainwater or recharge water were not stored in the exempt ASR well, then the native ground water mineral content would not have decreased or become diluted.

The pH of the treated rainwater averaged about 6.9, and the average native ground water pH of the pilot study wells was about 8.0. A very small decrease in pH of the stored recharge water in the wells was observed. In one of the pilot studies the exempt ASR well water demonstrated a decrease in turbidity after treated rainwater recharged the well. The other two exempt ASR wells in the study were on average about 1 NTU before and after recharge of the well with treated rainwater.

Restoring the Balance of Ground Water

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

Before the pilot study, two of the exempt wells were over-pumped and not producing the minimum needed for domestic water use. The other pilot study exempt well was routinely over-pumped, and often the homeowner had to have drinking water hauled in from an outside source. The exempt well in pilot study #1 had a water level below surface level of 260 feet. After the installation of the proper equipment for collection, treatment and injection of harvested rainwater into these exempt ASR wells, each well was able to provide a drinking water supply throughout the entire year. The static water level in the winter of the exempt ASR well in pilot study #1 increased to 50 feet below surface level.

About 20,000 gallons of treated rainwater were used to recharge the exempt ASR well from pilot study #1. To determine how much of the recharge water was stored underground and recovered for the pilot study, water quantity and water quality parameters were monitored for the recovered water. Once the volume of recovered water reached 20,000 gallons, the water quality parameters represented native ground water water quality parameters and the exempt well returned to being over-pumped. The stored recharge water was recovered at about 100 percent during the summer months. The amount stored was limited by the amount of harvested rainwater available for treatment and injection during the winter.

Potential for Exempt ASR Wells in Urban Areas

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

In pilot study #1 about 65,000 gallons of rainwater was collected from a metal rainwater catchment surface. Since, the exempt well was not yielding enough water for basic domestic use, the objective of this project was to use all rooftop harvested rainwater to sustain an adequate domestic water supply throughout the year. In this area of Oregon there are typically about 9 months of precipitation and 3 months without precipitation. To manage increased water use during the 3 months without precipitation, a large amount of rainwater storage is needed. In this pilot study 35,000 gallons was used in 9 wet months and about 30,000 gallons were used in the 3 dry months. To provide this much above ground water storage it would take about a 1000 square footprint on the property. Using an exempt ASR well to store 30,000 gallons takes less than 1 square foot. This small footprint for storing thousands of gallons of treated rainwater in an exempt ASR well opens the potential of using this water management tool in an urban setting. If exempt ASR wells were used in an urban setting to store precipitation underground, it would provide another tool for Low Impact Development (LID).

Infiltrating runoff on-site rather than discharging to the surface would better replicate the pre-development hydrology. By infiltrating on-site, basin hydrology will be closer to that of pre-development by increasing baseflows while also reducing surface flows (Stuart 2001). Applying exempt ASR well water management methods on a city-wide scale could potentially increase on-site rooftop rainwater collection and use within an urban area. The nearby City of Salem, Oregon. was used as an example of how exempt ASR wells could act as a Low Impact Development tool, store drinking water underground and augment public water supplies.

The City of Salem reported in its 2009 Water Management Conservation Plan (WMCP) that annual residential base water flow in 2007 was 8.7 million gallons per day (mgd) and the total city-wide base water flow was 23.4 mgd. The City of Salem defines the base water use as the average calculated from the winter months when outdoor water uses are negligible. The City of Salem's annual total reported water demand for 2007 was 9.53 billion gallons. The annual residential base water flow for the City was 3.17 billion gallons and total annual base water flow for the City was 8.54 billion gallons. Between the base water flow (average winter water use) and the total annual base water demand, there was about 1 billion gallons of outdoor water use. Salem's WMCP reported that there are 40,579 residential service connections and 5,125 commercial/multifamily water service connections.

In a 2001 Analysis of Land Cover Distribution for the City of Salem, Oregon, urban growth boundary (UGB) high-resolution satellite imagery was used to determine the amount of land covered in the UGB by buildings. According to the analysis, 2,000 acres of land within the UGB were covered by impervious surfaces from buildings. The average annual rainfall for Salem is 42 inches. If each water service connection represents a rainwater catchment system location and a potential site for installation of an exempt ASR well, then each site could recharge a well with treated rainwater to be stored underground. The amount of rainwater that could be harvested annually from rooftops in Salem's UGB was calculated to be about 2.28 billion gallons of water.

Potential Benefits of Exempt ASR Well Network for the Public

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

Rainwater is a clean water source available at the location of the water users. The rainwater is delivered to the water user at no cost. Rainwater harvested, treated and stored underground provides water to the user without building new water mains from a distant water source. Using exempt ASR wells would not require building a separate distribution system under streets and would reduce the need to expand the existing municipal distribution system to meet growing water demands.

Many cities have a single source of water and lack reliability in the event of an emergency that causes shutdowns of the supply. If all rainwater harvested was stored underground in exempt ASR wells in the City of Salem, there would be an emergency backup water source network that could last almost 100 days at the base water use rate of 23.4 mgd. An exempt ASR well network could provide increased flexibility and reliability to a community's water supply. An exempt ASR well network could augment the existing public water supply, which might provide new ways for permitting, licensing and water rights regulation on existing municipal water rights. Reducing the quantity of source water needed to be treated and distributed to water users also saves money for municipalities.

An exempt ASR well network in urban areas could significantly reduce stormwater runoff. For the City of Salem, about one-third of the impervious surfaces come from rooftops. The rainwater from these rooftops could potentially be stored on site in exempt ASR wells. This type of stormwater reduction would meet regulatory objectives for cities, reduce the need for new infrastructure and allow for more efficient ways to build Low Impact Deveolpment communities. This exempt ASR well network could provide an extensive ground water monitoring system to monitor the state's ground water supply.

Potential Benefits of Exempt ASR Well Networks for a Community

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

One of the findings in this study was that the amount of water recovered was directly related to the amount of treated rainwater injected into the exempt ASR well. In a city-wide exempt ASR well network, the stored water in the exempt ASR well could be limited to what was recharged, to help promote conservation. Exempt ASR well owners paid much greater attention to the amount of treated rainwater that recharged their exempt ASR wells and the amount recovered for domestic uses. This heighten attention to their exempt ASR well instilled a sense of ownership of their new water supply. If a city-wide ASR network cost water users less money to use, it would provide an incentive to use the limited quantity of water in the exempt ASR well first. The exempt ASR well could promote ownership or entitlement, leading to increased awareness of water conservation.

If developers were able to use exempt ASR wells as a Low Impact Development tool, they could construct more buildings on less land. Property owners in areas of Oregon with low-yielding exempt wells designated as Critical Ground Water Areas could recharge the exempt ASR wells with treated rainwater and restore lost value to the property.

Installation of exempt ASR wells in an urban setting could also open up the potential of using a Geothermal Heat Pump (GHP). Residents in Portland, Ore., using GHPs with desuperheaters for hot water heating would save 3945 kWh annually (Rafferty 2001). This would provide a large cost savings for each resident and business owner. The use of exempt ASR wells could provide large operational cost savings for city drinking water systems and stormwater systems, which could be returned to residents owning exempt ASR wells by reducing fees.

Potential Energy Savings of Exempt ASR Well Networks for Communities

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

If 2.28 billion gallons of rainwater were treated and stored in exempt ASR wells, water could be stored or used for domestic uses. Since the water flow needed for a single residence is low, submersible solar pumps could supply an adequate flow for domestic use of the exempt ASR well. According to Science Applications International Corporation's 2006 Water and Wastewater Energy Best Practice Guidebook, the energy that would be saved by not treating or delivering 2.28 billion gallons of water would be about 3.2 MWh for a city such as Salem that uses a surface water source. If the city was supplied by ground water, the annual energy savings would be 4.1 MWh.

If exempt ASR wells were placed all over the city to store treated rainwater, the well could serve a dual purpose by providing efficient heating, cooling and hot water heat. These urban exempt ASR wells could also supply Geothermal Heat Pumps (GHPs) for residential and commercial buildings. If every building with a water service connection in the City of Salem, including residential and commercial, installed a GHP system, the annual energy savings could be 180 GWh. The energy savings for commercial businesses were calculated using the annual residential energy savings reported by (Rafferty 2001). Research is under way for using ASR wells as a way to generate power from water falling into a well and potentially this could apply to exempt ASR well networks.

Potential Benefits of Exempt ASR Well Networks for Air Quality

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

According to the Environmental Protection Agency's Greenhouse Gas Equivalencies Calculator, combining the energy savings of the public water system and property owners with GHPs, the carbon dioxide emissions from more than 14 million gallons of gasoline being consumed annually would not enter the air. Another way to describe the benefit to air quality would be that 126,000 metric tons of greenhouse gas emissions would not be released. Also, exempt ASR wells could be equipped with filters that clean rainfall from the sky to a level that is even cleaner than what naturally falls to the ground.

Potential Benefits of Exempt ASR Well Networks for Water Quality

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

Many ground water supplies have minerals that can degrade water quality. The addition of the low-mineral treated rainwater could improve ground water quality, as treated rainwater is added to the native ground water and as water is pumped out of the well. Ground water pumped from an exempt ASR well could be treated again to provide additional water quality improvement. Ground Water Management Areas are areas in Oregon where ground water quality has been degraded. Using exempt ASR wells in these areas could dilute the degraded native ground water, and with the ground water recovered, it could be cleaned up even more with treatment.

Potential Benefits of Exempt ASR Well Networks for Ecosystem

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

Peak stream flows have been drastically impacted by impervious surfaces in urban areas. This unnatural rapid movement of rainwater from impervious surfaces to streams could be returned closer to natural storm event flows with exempt ASR wells. Large-scale urban exempt ASR well networks also would guard against drought and flooding. By having more water stored underground, there would be more clean and cold ground water available to discharge into streams and rivers. If all residential and commercial properties in Salem installed an exempt ASR well at a depth of 300 feet, there would be more than 900 acres of available surface area to recharge treated rainwater into the ground for storage. Using exempt ASR well networks could help restore some of the benefits that wetlands provided before development of the urban area. Exempt ASR wells promote ground water recharge, trapping of sediment, reduction in erosion and improved water quality.

Conclusion

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

This study demonstrated that treated rainwater harvested from rooftops can be effectively stored underground using exempt wells. There are many possible applications for this water storage and recovery method. Exempt ASR well networks could provide a water management tool that helps restore the balance in water quantity, water quality, air quality, and ecosystem health. Using exempt ASR well networks to store treated rainwater underground could help contribute to returning balance to the Earth's climate by improving air quality and conserving energy. Future studies are needed to determine the feasibility of urban exempt ASR wells networks.

Author Bio and Contact Information

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References

David Embleton has worked for three public drinking water systems in Oregon during the past 15 years. His experiences with these agencies have focused on water treatment, water quality, source protection, education and ASR operation. Since 2007, he has been the owner of a consulting business called GeoRain. He has assisted several clients in rainwater harvesting and exempt ASR well permitting. Mr. Embleton graduated from Linfield College with a Biology Degree with a minor in chemistry in 1997. He is licensed in Oregon in water treatment for public and private water systems. He is also an accredited professional in rainwater catchment systems. He can be contacted at: GeoRain, PO Box 221, Creswell, OR 97426 or by email at georain@centurytel.net.

References

  1. Top of page
  2. Abstract:
  3. Exempt Wells As a Water Management Tool
  4. Oregon's Rules Support Dual-Purpose Exempt Wells
  5. Subsurface Geology of Pilot Study Exempt Wells
  6. Source Water Quality for the Exempt ASR Well System
  7. Recharge Water Quality for the Exempt ASR Well System
  8. Water Quality of Exempt Well Native Ground Water and Stored Recharge Water
  9. Restoring the Balance of Ground Water
  10. Potential for Exempt ASR Wells in Urban Areas
  11. Potential Benefits of Exempt ASR Well Network for the Public
  12. Potential Benefits of Exempt ASR Well Networks for a Community
  13. Potential Energy Savings of Exempt ASR Well Networks for Communities
  14. Potential Benefits of Exempt ASR Well Networks for Air Quality
  15. Potential Benefits of Exempt ASR Well Networks for Water Quality
  16. Potential Benefits of Exempt ASR Well Networks for Ecosystem
  17. Conclusion
  18. Author Bio and Contact Information
  19. References
  • Chang, M., M. McBroom, and S. Beasley. 2004. Roofing as source of nonpoint water pollution. Journal of Environmental Management 73: 307315.
  • Nelson, D. 2002. Natural variations in the composition of groundwater. Drinking Water Program. Oregon Department of Human Services. Springfield , OR .
  • Pyne, D. 2005. Aquifer Storage Recovery: A Guide to Groundwater Recharge Through Wells. ASR Systems Press. Gainesville , FL .
  • Rafferty, K. 2001. An information survival kit for the prospective geothermal heat pump owner. Geo-Heat Center at Oregon Institute of Technology. Klamath Falls , OR .
  • Stuart, D. 2001. On-site runoff mitigation with rooftop rainwater collection and use. King County Department of Natural Resources Water and Land Resources Division. King County , WA .