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HomeMy WebLinkAboutResolution 2014-001 agreement to continue water resources studyMARANA RESOLUTION NO. 2014-001 RELATING TO UTILITIES; APPROVING AND AUTHORIZING THE UTILITIES DIRECTOR TO EXECUTE A JOINT FUNDING AGREEMENT WITH THE U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY TO CONTINUE FROM OCTOBER 1, 2013 THROUGH SEPTEMBER 30, 2016 THE STUDY ENTITLED AQUIFER-STORAGE CHANGE AND LAND-SURFACE ELEVATION CHANGE MONITORING IN THE TUCSON ACTIVE MANAGEMENT AREA WHEREAS the U.S. Geological Service, the Town of Marana, the City of Tucson, Pima County, the Town of Oro Valley, Metropolitan Domestic Water Improvement District, and the Arizona Department of Water Resources have since 2003 been j ointly funding a study of changes in aquifer storage and land-surface elevation in the Tucson Active Management Area; and WHEREAS the land subsidence and aquifer storage proj ect provides information needed for the development of water resources and land planning. NOW, THEREFORE, BE IT RESOLVED BY THE MAYOR AND COUNCIL OF THE TOWN OF MARANA, ARIZONA, as follows: SECTION 1. The Joint Funding Agreement between the Town of Marana and the U.S. Department of the Interior U.S. Geological Survey attached as E�iibit A to and incorporated in this resolution by this reference is hereby approved, and the Utilities Director is hereby authorized to execute it on the Town's behalf. SECTION 2. The various Town officers and employees are autharized and directed to perform all acts necessary or desirable to give effect to this resolution. PASSED AND ADOPTED BY THE MAYOR AND COUNCIL OF THE TOWN OF MARANA, ARIZONA, this 7 day of January, 2014. ATTEST: `-� �' �.� � Mayor Ed Honea APPROVED AS TO FORM: / / / ��:��.�� �� � ��.�r�� �. � : � � � .,� •. , � Resolution No. 20�4-001 12/18/2013 1:49 PM Form 9-1�66 (oct. zoas) U.S, t3EFA�2TM�iVT �� T'NE fi��'E�il�l�i GEI�L,t�GICAL St1RifEY 10tMT �UN[�ING AGREEMENT [�il:i WATER RESOURCES INVESTIGATIONS Amount Date to $16,950.00 October 1, 2013 6000000832/AZ066 14 WSAZ00400 ZF009EF 86-6000266 YES THIS AGREEMENT is entered into as of the,l0th day of December, 2013 by the U.S. GEOLOGICAL SURVEY, UNITED STATES DEPARTMfNT OF THE INTERIOR, party of the first part, and the TOWN OF MARAPIA, party of the second part. �' The parties hereto agree that subject to availability of appropriations and in accordance with their respective authorities there shall be maintained in cooperation an investigation of aquifer storage change and land subsidence in the Tucson easin and Avra Valley as described in the attached workplan, herein called the program. The USGS legal authority is 43 USC 36C; 43 USC 50; and 43 USC 50b. 2. The following amounts shall be cantributed ta caver a11 of the cost of the necessary field and analytical work directly refated tn this program. 2(b) inciudes in-Kind Services in the amount of $0.00 (a} by the party af the first part during the period (b) by the party of the second part during the period Amount Date (c) �dy $22,500.00 October 1, 2013 Customer #: Agreement #: Project #: TIN #: Fixed Cost Agreement Date September 30, 2016 to Date September 30, 2016 Total = $39,450.00 AdditionaE or reduced amaunts by each party during the above period or succeeding periods as may be determined by mutual agreement and set forth in an exchange of letters between the parties. The perfiormance period may be changed by mutual agreement and set forth in an exchange of letters between the parties. 3. The costs of this program may be paid by either party in conforrnity with the laws and regulations respectively governing each party. 4. The field and analytical wnrk pertaining to this program shall be under the direction of or subject to periodic review by an authorized representative of the party of the first part. S. The areas to be included in the pragram shall be determined by mutual agreement between the parties hereto or their authorized representatives. The methods employed in the fie(d and office shali be those adopted by the party of the first part to insure the required standards af accuracy subject modificatian by mutuai agreement. 6. During the cnurse nf this program, all field and analytical work of either party pertaining to this prpgram shall be open to the inspection nf the other party, and if the work is not being carried on in a mutually satisfactory manner, either party may terminate this agreement upon 60 days written notice to the other party. �-�3� (��ntinuatie�nj Custom�r #; 6�}OOE�QQ��2/�4��iC ��reement #s 1�W�AZtIt34£}t� 7. The cari��rt�l re�atds resc�it��t� fr�m this �ra�r��n iu�l[ b� d�pr��ited in t�� aific� c�f €�ri�tr� �f ttrcise r�cca€ds. Upc�n reque�t; r;c�p'res of the c�r€�in�p r�c�r�ls wE(I �� �rrc�vided tc� �he c�ffice �f t�te c�th�r part�!. E�. Ttre rr��ps; r�cords, or €�parCs rssuiti�t� frcrrr� tt�is pca�r�rrr s�a�it be ��cfe aua�tabEe tc� th� �ub�ac as �r�mptly �� per�sibie: Ttt� m��s, rec�rds, c�r r��arts raar��fly �uiii be pt�biish�t# tay the party �f th� first part, Notirew�v�r, #Fs� p�riy t�f �t�e s���,nd part reseru�s the ri�hi �p p�ub��sk� tt�� r���lts a�f ttrls �Sro�rr�rn �nd� if ��r�ady pubtish�d �y th� p�rty c�f th� first part shai#, upc�n �equ�sk, �� �ur��sY��cf b�t�r� �art� c+f th� �irst p�r�, at cQSts, irrK�res�i�ns suEtat�i� €csr pur�ses c�f reprc��tuctl�r� s#milar ta tt�at f�r wt�ich titt� �rig"s�€�[ capy tcv�s pr�p�r�d. Th� rn�ps; recvrds, car r��prts pubiished k�y either p�s�y s�r�ll cant�t� ��taterr�ent t�� �he cvc�p�rat�ve r�latians b��r�r��n th� parti�s. �'• t#��a5 �us'I( ;issc�e biElin�s uti(�zit�g �ep�rtm�rst a# ttte tnt�riar �it! f�r �o[l�ctxarr (form [�1-1q�). Biltin� d��urn�r�t� are �c� be rert��red q��rt�rCy. ��yr�r�ts af b[i!s ar� du� wittrin 6E� d�ys:��t�r tt�� �Silidn� €tate. (f not paid �y th�€tue cia�, �nteres� r�rit� t�e c�sarg�d �t the eurr��t `� rate fcrr e�ch �� da}r �eriad, c�r p�rtic�n Chereaf th�# the ��yrn�:n°� �� c�efay�d b��!e�rr€4 th� {�t�� fiat�s {�ii U'SC �717, CtFttl�atrall�'r C;�tl�r�0 �if� 8-22�22�, i4tl�U�t 23 2�+E3��. tJ.�» i�arrte'; �#c4dr�s�- �'�4e}�hon�: Ernail: t�ep�r�rr�en3 0� t�s� �n#eric�r t� : l�rnes M. teenhc�ut� S2€� N. }'�t�k Av�<� �utt� �24, Tue5can, �4Z ���39 SZt1�fx7C�-�67� x2?$ Tc�w� c�f I�rtarana Narz��. A�d!ress 3"elep�itr�re. �t�r�il; �i�r�atur�: � F��t�. S��nat�r�; r ,� � , � t��: ���' J es M. L��nistTUts _ _ Nat'�t��; �`���ea P3ir��taar �'it[i�a m rP 1�ttn Krr�i� 11��5 �N. �i�ric C�ntec �rive C�19ara�r��, A* $5��� _ 5�t�m�82-257� A> ° Aquifer-Storage Change and Land-Surface Elevation Change Monitoring in the Tucson Active Management Area FY 2014-2016 Introduction Aquifer-storage change has been monitored by the U.S. Geological Survey (USGS) within the Tucson Active Management Area (AMA) since 1996. The USGS began a cooperative study with Metropolitan Domestic Water Improvement District and the town of Oro Valley in 1996 to monitor aquifer-storage change in the Lower Canada del Oro subbasin. In 1998, the USGS began a cooperative study with the Arizona Department of Water Resources (ADWR), Pima County, and the City of Tucson to monitor land-surface elevation change and aquifer-storage change in the Tucson AMA. In 2003, these two monitoring studies were combined, and the town of Marana joined the study. This proposal outlines a scope of work for continued and expanded monitoring of both aquifer-storage change and land-surface elevation change in the Tucson AMA for the period of October 1, 2013 through September 30, 2016. Aquifer-Storage Change Aquifer-storage change can be monitored by measuring changes in graviTy. As water is added or removed from the aquifer, there is a change in mass and a corresponding measurable change in gravity. Gravity also is affected by changes in land-surface elevation, so mnnitoring of land-surface elevation change is essential for accurate measurement of aquifer-storage change. Water levels in wells commonly are monitored to estimate aquifer-storage changes. However, use of water-level variations entails significant assumptions about the hydraulic properties of the aquifer system. One difficulty is the heterogeneity of hydrologic properties of the aquifer; the alluvial sediments of the aquifer vary in lithology and texture, both laterally and with depth. Thus, data from individual wells may not represent aquifer characteristics some distance away from the well. A second difficulty is monitor-well design; in Tucson Basin, most water levels are measured in deep wells that tap multiple aquifer layers, most of which are confined and have accordingly low storage properties. Water levels in these deep wells are a composite of water ievels from several aquifer units. When these composite water levels are used to estimate storage changes, the hydrologic properties used in the calculation typically do not reflect the range of aquifer materials over which the well is screened. Because of these complexities and requisite assumptions, use of water-level variations as the only indicators of stora�e change can be uncertain, and cannot be reliably extrapolated beyond the well location. Monitoring of gravity and water levels in Tucson Basin has shown that large changes in groundwater storage, as much as several feet of water, have occurred that were not reflected in comparable water-level changes. Water levels following intense precipitation and infiltration, and associated gravity increases, either tend to rise slightly or to cease or slow their declines as gravity declines. These responses generally are manifested up to a year after the storage increase. The extent to which water levels are influenced by storage changes are directly related to the proximity of the well to the recharge area. Closer proximity yields an earlier and more discernible water-level response. Water- level responses also depend on the geometry and lithology of the sedimentary layers in the aquifer system that wells sample. Typically this information is missing, incomplete, or uncertain. Ail of this points to the need for a combination of storage-change and water-level data, which together enable defensible estimates of aquifer specific yield distribution. Land-Surface Elevation Change Permanent land subsidence can occur in alluvial basins when water is removed from aquifer systems (Galloway and others, 1999). Aquifer systems in unconsolidated rocks such as those in the Tucson AMA are supported by the granular skeleton and the pore- fluid pressure. When groundwater is withdrawn and the pore-fluid pressure is reduced, the granular skeleton is compressed, causing some lowering of the land surface. Both the aquifers (sand and gravel) and aquitards (clay and silt) of aquifer systems are deformed as a result of changes to the pore-fluid pressure and skeleton, but to different degrees. Most permanent subsidence occurs due to the irreversible compression of aquitards during the slow process of aquitard drainage (over a number of years). Permanent subsidence, seasonal elastic deformation, and uplift have been observed in Tucson Basin and Avra Valley. Rates of compaction in Tucson Basin in relation to water- level decline have been less than 0.5 foot per 100 feet of water-level decline. Comparison with the Eloy and Phoenix areas (greater than 1 foot per 100 feet of decline) suggests that compaction to date in the Tucson region has been largely elastic and recoverable. Compaction and land subsidence can be slowed or stopped, and in areas having appropriate geologic conditions, reversed to some extent by eliminating groundwater withdrawals or through artificial recharge. The City of Tucson has increased delivery of Central Arizona Project (CAP) water, while reducing pumping from the Central Well Field. This has reduced water-level declines; however, subsidence due to previous pumpage may continue for some time into the future. Continued monitoring of areas having the greatest potential for subsidence will provide information that municipalities and resource managers can use in the development and implementation of prevention and mitigation efforts. Objectives The objectives of this project are to monitor aquifer-storage change and land-surface elevation change within the Tucson AMA. 2 Approach Land-surface elevation change is monitored at a network of benchmarks (figure 1) throughout the Tucson AMA by measuring changes in land surface elevation over time (approximately annually) with Interferometric Synthetic Aperture Radar (InSAR) and targeted GPS surveys. The Arizona Department of Water Resources (ADWR) has an InSAR program in the Tucson AMA. InSAR is a technique that utilizes interferometric processing to compare the amplitude and phase signals received during one pass of the satellite-based SAR platform over the AMA with the amplitude and phase signals received during a second pass of the platform over the same area but at a different time. The SAR data are used by ADWR to produce a land-surface elevation-change map over the same time period as the targeted GPS surveys in the AMA. The GPS data is then used to compare with and constrain the InSAR deformation information. The annual InSAR product provides a much broader coverage of land-surface deformation information than could be feasibly obtained with GPS alone. Aquifer-storage change is monitored by measuring changes in gravity over time at the same network of benchmarks. Gravity is affected by mass and distance; a change in mass or a change in elevation will cause a change in gravity. Groundwater depletion is a mass change and land-surface elevation change is a distance change. By removing the effect of change in distance, changes in gravity are used to determine changes in aquifer-storage. Temporal-gravity surveys are used in the Tucson AMA to detect local changes in the gravitational field of the Earth. The method is readily applied to measurement of aquifer- storage change in the AMA because of the occurrence of significant variations in pore- space storage that result from groumdwater withdrawal and periodic (non-continuous) focused recharge. Two instruments are used at the network of benchmarks: the relative gravity meter and the absolute gravity meter. The relative meter is the primary instrument by which differences in gravity are monitored at stable monuments. Much as control benchmarks are used in conventional land surveying, repeated relative gravity surveys for groundwater storage monitoring should include a reference station where gravity is known to vary little, or the absolute acceleration of gravity is monitored. The USGS uses a Micro-g LaCoste A-10 field-portable absolute gravity meter to establish these reference stations as needed. This is particularly valuable in a hydrologic context where a number of absolute stations may be located throughout a basin, thereby serving to constrain a least-squares adjustment of the network of gravity differences from relative gravity surveys. Gravity surveys are conducted annually at the entire network of benchmarks (figure 1). GPS surveys also are conducted annually at the portion of the network that previous surveys have shown to be the most active areas of land-surface elevation change. The network of benchmarks may be modified and/or expanded in areas of poor coverage to improve resolution. These areas include Avra Valley, Sahuarita, and central Tucson. Gravity measurements will increasingly be made using the A10 portable absalute gravimeter; this will allow for fewer relative gravity measurements, thus improving the efficiency of data collection. Fig. 1. Proposed network for aquifer-storage and subsidence monitoring in the Tucson AMA. Bene�ts Aquifer-storage monitoring Microgravity surveys are an efficient, noninvasive means of ineasuring changes in the amount of groundwater in Southwestern alluvial basins. Monitoring changes in groundwater storage in the Tucson AMA is a means to monitor the status of the basin aquifers. This will be of value as water-supply entities in eastern Pima County address needs to manage and augment groundwater resources. The most significant value would accrue as the city further implements aquifer storage and recovery efforts at the Clearwater Renewable Resource Facility (CRRF). As the CRRF reaches anticipated capacity, pumping from the Central Well Field will continue to be reduced. This decreased demand will, if withdrawals do not increase, enable the aquifer to slowly refill. Water-level data entail assumptions about aquifer and well properties; thus, monitoring of gravity changes as pumping decreases in the basin currently is the only way to measure attendant changes in the amount of water in the aquifer and determine if and when aquifer recovery is occurring. This information conceivably will serve as part of a basis for decisions regarding distribution of groundwater withdrawals to help in mitigating land subsidence or aquifer storage losses in particular areas. Aquifer-storage change is one of the three components of the groundwater budget. The other two are inflow to and outflow from the aquifer system. Measurement of aquifer- storage change and measures and estimates of outflow enable better estimation of recharge and development of a more reliable groundwater budget for the basin. Measures of aquifer-storage change increase the reliability and utility of groundwater flow and management models. Use of storage-change data to improve model calibration enables addttional reduction in the uncertainty of model results. The improved understanding of the movement, distribution, volume, and availability of ground water, to which storage monitoring contributes, enables more effective water management in the Tucson AMA and in other areas of the State. Surveys in the Tucson AMA since 1998 have provided previously unavailable data quantifying recharge and storage changes. For example, the results of aquifer-storage change monitoring in the Tucson Basin between 1998 and 2012 indicate that storage change and recharge can vary considerably from year to year. It is possible that just a few years may account for the majority of recharge to southwestern aquifers for an entire decade or more. These data are being used to improve the understanding of the aquifer systems and to improve groundwater flow models that will be used in resource planning. 4 Land-surface elevation change monitoring Some types of infrastructure are more sensitive to changes in land slope than other types. Sewer systems are largely gravity driven, and aze designed and constructed at slopes of about 2 feet per 1,000 feet. Small slope changes can cause operational problems under some conditions. Accurate determination of the rates, amounts, and distribution of land subsidence, together with delineation of higher-risk areas, will provide data upon which mitigation and protection plans can be based. Subsidence rates will increase when the stress threshold between elastic and inelastic compaction is exceeded. Because it is not possible to reliably estimate when the threshold might be exceeded in the Tucson AMA, and infrastructure damage becomes more likely, subsidence monitoring also provides a means to identify the type of compaction that is occurring. Groundwater withdrawals from the City's Central Well Field has been substantially decreased as the CRRF reaches full capacity. However, regional subsidence in response to previous pumping is unlikely to end in the near future. It will continue until the aquifer system reaches pressure equilibrium. Observation of the timing and magnitude of aquifer responses will further improve the understanding of land subsidence and of how the aquifer systems function. Monitoring data also will contribute to a better understanding of the responses of the aquifer systems to withdrawals, and will provide additional insight in future plans for well-site selection, recharge efforts, and water- management programs. Additionally, monitoring data will continue to augment and serve as ground truth for satellite-based information that the ADWR is acquiring to enable broad-scale assessments of regional subsidence in the Tucson Basin. Differential subsidence refers to a relatively large amount of subsidence over a relatively short distance, and can cause focused effects. For example, localized subsidence of as little as one-half inch can necessitate rebuilding a highway overpass. Differential subsidence has the potential to separate pipe joints of sewer and water lines—this can lead to system disruptions and roadway damage. Also vulnerable are the concrete lining sections of engineered channels that rely on the integrity of expansion joints to prevent flood damage. Costs to address such infrastructure failures are high. Awareness of the distribution and magnitude of differential subsidence can help to guide the design and implementation of maintenance and monitoring schedules, selection of monitoring methods, and the design and construction of future infrastructure. Products 1) Annual interpretive maps of aquifer-storage change and land-surface elevation change in the Tucson AMA (available to all cooperators and to the public on http://az.water.usgs.gov�. 2) Oral presentation of findings to all cooperators each year. 3) Oral presentation of findings at a state or national professional society meeting each year or as funding permits. 6 Work Schedule and Budget Fixed-cost funding information for this project is provided in tables 1 and 2. Table 1 presents the schedule of work activities over the project life. Table 2 presents the summary of funding by agency. It is understood that all agency funds in future years are subject to appropriation. Table 1—Schedule of work activities. Work Tasks Year 1 Year 2 Year 3 1. GPS and InSAR surve s 2. Gravi surve s 3. Data post rocessing, analysis, and inter retation . z 4. Preparation of annual digital maps of aquifer-storage change and land-surface elevation change ` 5. Oral Report to project cooperators 6. Oral Presentation at state or national rofessional meeting ,. 7. Review, revision and approval of annual maps of a uifer-stora e chan e and land-surface elevation chan e 8. Posting of annual maps to http://az.water.usgs.gov/ and distribution to roject cooperators 7 Table 2—Summary of funding by agency. Note: Funding distributions shown are proposed for the FY14-16 project period. A table reflecting the final distribution will be provided to all participants following completion of funding agreements.