2013 State of Arizona Hazard Mitigation Plan Risk Assessment

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1 Fissures Introduction/History Earth fissures are linear cracks in the ground that extend from the groundwater table and are a direct result of subsidence caused by groundwater depletion. The surface expression of fissures ranges from less than a yard to several miles long and from less than an inch to tens of feet wide. The longest fissure is in County, near Picacho, and is over 10 miles long. Earth fissures occur at the edges of basins, usually parallel to mountain fronts, or above local bedrock highs in the subsurface, and typically cut across drainage. Fissures change flood patterns, break buried pipes and lines, cause infrastructure to collapse, provide a direct conduit to the groundwater table for contaminants thrown into them, and even pose a life safety hazard. The Basin and Range Province that occupies the southern third of Arizona is the primary area that is susceptible to earth fissures; this area encompasses parts of four counties that are particularly prone to earth fissures:,, and Pima Counties. County has more fissures than any other county in Arizona. The AZGS combined fissure zones into groups, or planning areas, to facilitate legislative mandate that requires all fissures in Arizona to be mapped and publicly disclosed. Original mapping is complete for the areas listed below, and will be remapped as new areas of concern develop. These areas are also published and available at AZGS Earth Fissure Viewer ( Table RA-39: AZGS Mapped Fissure Areas Area Bowie-San Simon Croton Springs Dragoon Road Elfrida Sulphur Springs North (pending) Three Sisters Buttes Harquahala Plain Luke Mesa Scottsdale/NE Phoenix Wintersburg Apache Junction Greene Wash Heaton Marana Pete s Corner Picacho Sacaton Butte Santa Rosa Wash Signal Peak Tator Hills Toltec Buttes County 208

2 Source: AZGS Fissures have been occurring in Arizona at least since 1927, when the first one was found near Eloy. The number of fissures has increased dramatically since the 1950s because of groundwater depletion, first because of agriculture, and later, due to exponential population growth. The risk posed by fissures is also increased as the population expands into the outlying basin edges and mountain fronts. Several fissure case histories are outlined below. San Tan Mountains, and Counties Foothills undermining at least one home, and crossing several roads; dogs trapped in flash flood flowing through the fissure in Y-crack crosses the Hunt Highway and San Tan Blvd east of Sossaman Road; present at least by 1969; catastrophically re-opened from 195 th Street and Happy Road to San Tan in 2005 and again in 2007, damaging roads, corrals, fences, driveways, stranding and trapping vehicles, and killing a horse. Apache Junction/East Mesa, County Baseline & Meridian fissure crosses diagonally under the intersection, fissure zone over one mile long. Ironwood and Guadalupe industrial facilities built on top of several fissures in the area; fissures stop immediately east of subdivision; fissures crossing powerlines. Mesa, County Loop 202 (Red Mountain Freeway) fissure present at least since 1970s; attempted mitigation during construction cost $200,000. Sossaman Road and University Drive fissure runs diagonally through a subdivision along the entrance; fissure known in 1973 and subsequently backfilled. Picacho, County I-10 Arizona Department of Transportation still trying to determine effective mitigation for the fissure crossing. Picacho Pump Station fissure crosses access road and runs nearly to canal; damaged road in Wintersburg, County Fissure runs perpendicular to power transmission lines near Palo Verde Nuclear Generating Station; made one road impassable. Scottsdale, County CAP Canal fissure paralleling the canal opened within a few feet of the lining on the east side in th St and Cholla discovered in 1980s. Flood retarding structures, County McMicken Dam, White Tank Mountains dam had to be removed and replaced; cost several million dollars. Powerline FRS, Apache Junction fissure just discovered within 1200 feet of the FRS; Flood Control District examining mitigation options. Avra Valley, Pima County CAP Canal fissure discovered that nearly intersected the canal in Willcox, County Nickels Road in 1984, a fissure opened down one side of the road near where it crosses power transmission lines. 209

3 Potential Secondary/Cascading Effects: The type of cascading events resulting from earth fissures is broad, ranging from accelerated erosion rates which undercut foundations, roads, gas and water lines, to contamination of fresh water aquifers. The latter is the most serious of secondary events, since entire communities may be affected by the contamination. In addition, mitigation may prove difficult, expensive and could require years of pumping and filtering to purge the contaminated waters. In southern Arizona, cascading events associated with earth fissure formation may potentially include: Harm to livestock cattle and horses, which can stumble into fissures and find it difficult or impossible to get out. Accelerated erosion rates leading to head-cut erosion and soil removal; Gully development, which further disrupts natural drainage patterns and impacts agricultural patterns; Drainage disruption where captured runoff can lead to local flooding; Canal breach where fissures intersect existing canal alignments Exhuming buried gas or water lines potentially leading to broken mains leading to fires or local flooding; Despoiled fresh water aquifers there is no evidence in Arizona for this yet, but contaminating groundwater, with concomitant disruption of water delivery to homes, municipalities, and farm fields, is a cascading event of great concern. Dumping of organic and inorganic substances into fissures (tires, appliances and sundry trash items are common features in some fissures); Disruption of transportation corridors roadways and railroads adversely impacting travel and in the case of train derailment could lead to a toxic chemical spill. According to Slaff (1993), fissure formation misaligned a section of track in the Picacho Basin causing a train to derail. Probability and Magnitude There are no methods of quantifiably predicting the probability and magnitude of earth fissures. The locations of increased risk for potential fissures may be highlighted to specific areas if enough information about the subsurface geology and groundwater levels are available. As long as subsidence continues (even if the groundwater levels should rise and stabilize), fissures will continue to occur. The magnitude of the fissures vary with the depth to groundwater, type of surficial material present, amount of groundwater removed, basin depth, volume of runoff from precipitation, and human intervention or lack thereof. The geographic extent of fissures are tracked and mapped by Arizona Geological Survey (AZGS) across the state. Some historically recorded fissures are not visible or traceable anymore, disturbed or filled due to human activities or natural events (floods, erosions, etc.). The map shown below illustrates known fissure areas captured in the AZGS GIS dataset. 210

4 Map RA-8: Fissure Hazard Map Source: Arizona Earth Fissures shapefile ((DI-39 v ) - AZGS 2013; Baker This map is preliminary and subject to change. This map is not to be used for disclosure purposes. The AZGS makes no warranties, expressed or implied with respect to this information. 211

5 Risk & Vulnerability The impacts of earth surface fissures due to subsidence have the potential be economically devastating to developed local areas. During the periods of heavy rains, fissures can enlarge and widen quickly through erosion and create a substantial hazard to people, buildings and infrastructure. Also, fissures provide a conduit for stormwater runoff to carry contaminates to underground aquifers. State owned assets that are typically most exposed to fissure hazards are roadways. There were no critical or non-critical structures identified within the high hazard areas shown on the map above. Damages to roadways are relatively minor and are best mitigated by keeping stormwater from entering the fissures within the vicinity of the roadways. The compilation of risk assessment data from local plans indicates that approximately $98 million in locally identified critical and non-critical facilities are exposed to a fissure risk hazard. There are no known state facilities that fall within a critical proximity of recorded fissures and no estimations of losses were made. Table RA-40: Population Sectors Exposed to Areas with Fissures Risk Monitored by AZGS County Total Population Population Exposed Percentage Exposed Over 65 Over 65 Exposed Percentage Over 65 Exposed Total Population Exposure to Fissures Apache 71, % 8, % 131,346 1, % 22, % Coconino 134, % 11, % Gila 53, % 12, % Graham 37, % 4, % Greenlee 8, % 1, % La Paz 20, % 6, % 3,817, , % 462,641 14, % Mohave 200, % 46, % Navajo 107, % 14, % Pima 980, % 151, % 375,770 31, % 52,071 3, % Santa Cruz 47, % 6, % Yavapai 211, % 50, % Yuma 195, % 30, % Statewide 6,392, , % 881,831 18, % Population counts based on census 2010 blocks intersection with fissures zone areas defined by AZGS. As seen in the table above, 147,427 of the state population live either in proximity to known earth surface fissures or within fissure hazard areas, which amounts to about 2.31% of the total population (6,392,017). When considering the just special population of those over 65, there is a slight decrease in percentage to 2.14% at risk to exposure. 212

6 Table RA-41: Local & Loss Estimates Based on Fissure Risk County Total Est Asset Value (x $1,000) Asset Value Exposed to Hazard(x $1,000) Est Potential Losses (x $,1000) Statewide Totals $382,041,435 $182,232 $0 Apache $11,101,665 No Data No Data $10,615,770 No Data No Data Coconino $22,517,439 No Data No Data Gila $6,811,526 No Data No Data Graham $2,999,628 $0 No Data Greenlee $6,747,353 No Data No Data La Paz $2,359,292 No Data No Data $189,975,238 $27,436 No Data Mohave $15,521,558 No Data No Data Navajo $11,908,834 No Data No Data Pima $50,584,821 No Data No Data $13,472,739 $70,676 No Data Santa Cruz $3,044,947 No Data No Data Yavapai $18,491,858 No Data No Data Yuma $14,750,955 No Data No Data NOTE: No Data denotes lack of available information for assessment. Risk & Vulnerability Based on the Index Values and Assigned Weighting Factors determined in the CPRI table discussed at the beginning of this section and updated by the Planning Team, the results based on Fissures are shown below. County and Local CPRI average values are also given below. These figures are based on information provided in their current respective mitigation plans. Table RA-42: State CPRI Results for Fissures Hazard Probability Magnitude/ Severity Warning Time Duration CPRI Score (max: 4) Likely Limited >24 Hours >1 Week Fissures CPRI Score = (Probability x.45)+(magnitude/severity x.30)+(warning Time x.15)+(duration x.10) Table RA-43: County and Local CPRI Results for Fissures County/Community CPRI 1.88 Benson 2.30 Bisbee 2.05 Douglas 1.45 Sierra Vista 2.05 Tombstone 1.45 Unincorporated County 1.95 Wilcox 2.85 Coconino 3.23 Coconino 3.85 County/Community CPRI Flagstaff 3.90 Williams 3.70 Page 1.45 Graham 3.20 Graham 3.55 Pima 3.15 Safford 3.40 Thatcher Avondale

7 County/Community CPRI Buckeye 1.10 Carefree 1.00 Cave Creek 1.00 Chandler 1.00 El Mirage 1.10 Fountain Hills 2.50 Fort McDowell Yavapai Nation 1.40 Gila 1.00 Gilbert 2.20 Glendale 2.35 Goodyear 1.45 Guadalupe 1.45 Litchfield Park 1.45 Unincorporated County 2.95 Mesa 3.10 Paradise Valley 1.65 Peoria 2.50 Phoenix 1.45 Queen Creek 1.90 CPRI scores for Flooding based on county mitigation plans Environmental Risk & Vulnerability 2013 State of Arizona Hazard Mitigation Plan County/Community CPRI Salt River Pima- Indian 2.50 Salt River Project 1.75 Scottsdale 1.90 Surprise 2.20 Tempe 2.05 Tolleson 1.30 Wickenburg 2.50 Youngtown Apache Junction 2.20 Casa Grande 2.50 Coolidge 0.90 Eloy 2.05 Florence 1.60 Kearny 1.50 Mammoth Superior 1.75 Unincorporated County 2.95 Based on the Index Values and Assigned Weighting Factors determined in the Environmental Risk CPRI table discussed at the beginning of this section and updated by the Planning Team, the results based on Fissure are shown below. Table RA-44: State Environmental CPRI Results for Fissure Environmental Risk Due to Fissure Component Probability of an Impact Magnitude/ Severity Duration of Impact/Damage CPRI Score (max: 3.6) Air Highly Likely Negligible < 1 month 1.8 Water Highly Likely Limited 6 months+ 3.0 Soil Highly Likely Catastrophic 6 months+ 3.6 Average CPRI Environmental Risk Rating: 2.8 (max 3.6) Consequences / Impacts Public There are no obvious direct impacts to public health due to the effects of earth fissures. Public safety is rare and can be eliminated with the use of caution, foresight, and preplanning. Responders to the Incident Similar to the impact to the public, there is no real threat to responders as this is not usually considered an incident response type of hazard. 214

8 Continuity of Operations / Delivery of Services Fissures do not pose a threat to the state s ability to continue effectively functioning. Though, it may be hampered if key infrastructure is compromised or access is limited/denied. Economic / Financial Condition of Jurisdiction Economic impact due to earth fissures can be a result of damaged transportation systems, buildings, sewage facilities, irrigations systems, water-storage systems, pipelines and agricultural fields, just to mention a few. Areas prone to or experiencing fissures may also be affected by decreased property value as well as increased cost to development projects caused by modifications to plans and structure placement. These costs may directly or indirectly affect the jurisdiction in costs or tax base. Public Confidence in Jurisdiction s Governance Although response is not generally an issue directly related to this hazard, taking a proactive approach by addressing earth fissures through prevention as opposed to only when a critical point is reached is likely to maintain the public s confidence level. Lack of situation knowledge will lead to a misunderstanding of the situation and may result in frustration and a negative attitude toward those that are perceived as responsible, which in most cases is the government. Resources Definitions AZGS Arizona Geological Survey GIS Geographical Information System Subsidence (see Section ) USGS U.S. Geological Survey Sources AZGS Earth Fissure Viewer interactive map: AZGS fissure study areas (shows all publsihed Earth Fissure Planning Maps for,, Pima and Counties, Arizona. Map scale 1:250,000, products of the Arizona Geological Survey, 2007, Online at Earth Fissure Study Area Map of Arizona. Map Scale 1:24,000, products of the Arizona Geological Survey, , Online at (As of February 2010, 16 of 23 study area maps are available). Earth Fissure Publication List, Arizona Geological Survey 2009, Online at See for numerous other earth fissure resources. References Allison, M.L., and Shipman, T.C., 2007, The role of AZGS in mapping earth fissures in AZ, Arizona Geology, Vol. 36, No. 4/ Vol. 37 No. 1, Winter/Spring 2007, AZGS, Tucson, AZ. Allison, M.L., and Shipman, T.C., 2007, Earth fissure mapping program 2006 progress report, OFR 07-01, June 2007, AZGS, Tucson, AZ. AZ Land Subsidence Group, 2007, Land subsidence and earth fissures in AZ: Research and informational needs for effective risk management, white paper, Tempe, AZ. Carpenter, M.C., 1999, Land subsidence in the US [Galloway, D., Jones, D.R., and Ingebritson, S.E., editors], South-Central Arizona: Earth fissures and subsidence complicate development of desert water resources, USGS Circular Conway, B.D., 2006, What is land subsidence?, presentation to Arizona Planning Association Conference, AZ Department of Water Resources. Fergason, K.C., 2006, Earth fissure zone investigation report Powerline and Vineyard flood retarding structures, County, AZ, AMEC Earth & Environmental, Inc., 25 May 2006, Tempe, AZ. Gelt, J., 1992, Land subsidence, earth fissures change Arizona s landscape, Arroyo, Summer 1992, Vol 6 No. 2, University of AZ. 215

9 Harris, R.C., 2001, A new earth fissure near Wintersburg, Co, AZ, OFR 01-10, Nov. 2001, AZGS, Tucson, AZ. Harris, R.C., and Allison, M.L., 2006, Hazardous cracks running through AZ, Geotimes, August 2006, Geological Society of America, Boulder, CO. Holzer, T.L., 2000, Methods for prediction of earth fissures & surface faults caused by groundwater withdrawal, The Fragile Territory, Congresso Nazionale dei Geologi, 10 th, Rome, Proceedings, Consiglio Nazionale dei Geologi, p Leake, S.A., 1997, Land subsidence from ground-water pumping, Impact of climate change on the southwestern US workshop, USGS. Pewe, T.L., 1990, Land subsidence and earth-fissure formation caused by groundwater withdrawal in Arizona; a review, in Groundwater geomorphology; the role of subsurface water in earth-surface processes and landforms [Higgins, C.G., and Coates, D.R., eds.], Geological Society of America Special Paper 252, Boulder, CO. Sandoval, J.P., & Bartlett, S.R., undated, Land subsidence/earth fissuring on the CAP, AZ, US Bureau of Reclamation, AZ Projects Office. Schumann, H.H., & Genauldi, R., 1986, Land subsidence, earth fissures, and water-level changes in southern Arizona, Arizona Bureau of Geology and Mineral Technology Map 23. Slaff, S., 1993, Land subsidence and earth fissures in Arizona, Down-to-Earth Series 3, AZGS, Tucson, AZ. 216