APPENDIX H

ACEC EVALUATIONS

 

September 2012 Lower Sonoran Record of Decision and Approved Resource Management Plan H-1

APPENDIX H

AREAS OF CRITICAL ENVIRONMENTAL CONCERN

(ACEC) EVALUATIONS

The Coffeepot Botanical ACEC was originally created in an Amendment to the Lower Gila South 

Resource Management Plan in 1988. The Lower Sonoran RMP reauthorizes it based on the Relevance 

and Importance originally used in that Amendment. No new evaluation sheet was created. The 

Amendment describes the Coffee Pot Botanical ACEC in this way:

“The Coffee Pot Botanical ACEC area (approximately 9,600 acres) includes portions of the northern 

and southern Sauceda Mountains. The Sonoran desert shrub community in this area is diverse, 

comprised of over 285 plant taxa, many of which have limited distributions in the United States. Five 

special status plant species also occur in the Coffee Pot Botanical area: They include Acalypha pringlei; 

Graptopetalum rusby; Stenocereus thurberi; Echinomastus erectocentra var. acunensis, and Peniocereus 

greggii. The latter two species are being considered for listing as federal endangered species.”

Importance

The occurrence of five special status plant species, particularly Red Pineapple Cactus, is sufficiently 

unique on BLM public land to meet the importance criterion necessary for ACEC designation.

Relevance

No apparent threat to biological resources exists. However, the Red Pineapple Cactus is found on a 

single limited soil type within the ACEC and any mining activity or other disturbance no matter how 

limited would have grave and irrevocable consequences to the population. Currently, the Red Pineapple 

Cactus population is declining and further study is needed to determine the cause. Therefore, the area 

meets relevance criterion necessary for ACEC designation.”

The Lower Sonoran RMP finds the conditions have not changed substantially and the area continues to 

qualify for ACEC designation.

Area Considered: Cuerda de Lena

General location T.13S. R. 6 & 5 W. (portions of) and T14S. R.6 & 5 W. (portions of)

General description Sonoran desert ecosystem

Acreage 59,300 acres

Values considered Wildlife, Natural process or system, Cultural resources

Identification Criteria

To be considered as a potential ACEC and analyzed in RMP alternatives, an area must meet the criteria of 

relevance and importance, as established in 43 CFR 1610.7-2.
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

H-2 Lower Sonoran Record of Decision and Approved Resource Management Plan September 2012

Area Considered: Cuerda de Lena

Relevance: There shall be present a “significant” historic, cultural, or scenic value; a fish or wildlife resource or other 

natural system or process; or natural hazard. This generally means that the value, resource, system, process, or hazard is 

characterized by one or more of the following:

Relevance Value Yes/No Rationale for Determination

A significant historic, cultural, or scenic value 

(including but not limited to rare or sensitive 

archeological resources and religious or cultural 

resources important to Native Americans).

Yes The area is of significant cultural importance as 

it is adjacent to the Tohono O’odham Nation 

and is part of their traditional homelands. In 

addition, a broad variety of cultural sites dating 

from the Middle Archaic period, thousands of 

years ago, to the late 19th century are 

represented in this area. The density of sites is 

greater in these areas than in the surrounding 

areas. One of the most important prehistoric 

obsidian sources for tool materials is located in 

this area.

Citations of material relied upon:

Jane Pike Childress and Lorraine Marquez Eiler

Darby Wells Village: An Hia-Ced O’odham 

Settlement near Ajo, Arizona (1998)

Rick Martynec and Jane Thompson Ajo’s Earliest 

Visitors, Based on the Black Mountain Survey

(2005) 

Rick Martynec, Shelby Ballard, Sandy Martynec, 

and Rich Davis

Ajo Earliest Visitors, Based on the Black Mountain 

Excavations (2011)

Citation of later supporting documentation:

John M.D. Hooper

Archaeological Resources of the Ajo Region: A 

Cultural Resources Inventory of 2,928 Acres of BLM 

Land in Western Pima County, Arizona (2011)

A fish and wildlife resource (including but not 

limited to habitat for endangered, sensitive, or 

threatened species; or habitat essential for 

maintaining species diversity).

Yes The area is only area within the Lower Sonoran 

Field Office that is managed for the endangered 

Sonoran pronghorn antelope. There are 

currently Sonoran pronghorn that take up 

residence on public lands within the proposed 

bounds of the ACEC. The proposed ACEC also 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

September 2012 Lower Sonoran Record of Decision and Approved Resource Management Plan H-3

Relevance Value Yes/No Rationale for Determination

contains suitable and occupied habitat for the 

Candidate species Cactus ferruginous pygmyowl. 

A natural process or system (including but not 

limited to endangered, sensitive, or threatened 

plant species; rare, endemic, or relict plants or 

plant communities which are terrestrial, aquatic, 

or riparian; or rare geological features).

Yes The area contains Saguaro cactus forest 

situations which are foraging habitat for the 

endangered lesser long-nosed bat. The 

proposed ACEC also contains suitable and 

occupied habitat for the Candidate species 

Cactus ferruginous pygmy-owl. The proposed 

ACEC contains important fawning, breeding, 

loafing and foraging habitat for the Sonoran 

pronghorn.

Natural hazards (including but not limited to areas 

of avalanche, dangerous flooding, landslides, 

unstable soils, seismic activity, or dangerous cliffs). 

A hazard caused by human action may meet the 

relevance criteria if it is determined through the 

resource management planning process that it has 

become part of a natural process.

No No natural hazards are known to occur.

Importance Criteria

Importance: The value, resource, system, process, or hazard described above must have substantial significance and values 

to satisfy the “importance” criteria. This generally requires qualities of more than local significance and special worth, 

consequence, meaning, distinctiveness or cause for concern. A natural hazard can be important if it is a significant threat to 

human life or property.

Importance Value Yes/No Rationale for Determination

Has more than locally significant qualities, which 

give it special worth, consequence, meaning,

distinctiveness, or cause for concern, especially 

compared to any similar resource.

Yes The area is of significant cultural importance as 

it is adjacent to the Tohono O’odham Nation 

and is part of their traditional homelands. In 

addition, a broad variety of cultural sites dating

from the Middle Archaic period, thousands of 

years ago, to the late 19th century is 

represented in this area. The density of sites is 

greater in these areas than in the surrounding 

areas. One of the most important prehistoric 

obsidian sources for tool materials is located in 

this area.

Citations of material relied upon:

Jane Pike Childress and Lorraine Marquez Eiler 

Darby Wells Village: An Hia-Ced O’odham 

Settlement near Ajo, Arizona (1998)

Rick Martynec and Jane Thompson Ajo’s Earliest 

Visitors, Based on the Black Mountain Survey 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

H-4 Lower Sonoran Record of Decision and Approved Resource Management Plan September 2012

Importance Value Yes/No Rationale for Determination

(2005) 

Rick Martynec, Shelby Ballard, Sandy Martynec, 

and Rich Davis

Ajo Earliest Visitors, Based on the Black Mountain 

Excavations (2011)

Citation of later supporting documentation:

John M.D. Hooper

Archaeological Resources of the Ajo Region: A 

Cultural Resources Inventory of 2,928 Acres of BLM 

Land in Western Pima County, Arizona (2011)

Has qualities or circumstances that make it fragile, 

sensitive, rare, irreplaceable, exemplary, unique,

endangered, threatened, or vulnerable to adverse 

change.

Yes The proposed Cuerda de Lena ACEC contains 

significant wildlife resources, including priority 

habitat for three endangered (priority) species -

Sonoran pronghorn, lesser long-nosed bat, and 

the cactus ferruginous pygmy-owl. The area is 

identified was proposed as critical habitat for 

the cactus ferruginous pygmy-owl and includes a 

proposed recovery area for the cactus 

ferruginous pygmy-owl. The area provides

important fawning habitat for the Sonoran 

pronghorn. Several large washes provide 

suitable cactus ferruginous pygmy owl habitat. 

The area provides foraging habitat for the 

endangered lesser long nosed bat and includes 

habitat for special status (priority) species 

including the Sonoran desert tortoise and rosy

boa. There is a strong cultural resource 

component associated with this area because 

the area is part of the traditional Tohono

O’odham homeland and contains much 

important information about prehistoric 

settlement and subsistence. The area is popular 

with local residents and seasonal winter visitors 

from around the United States and Canada for 

dispersed recreation including camping and 

sightseeing.

Has been recognized as warranting protection to 

satisfy national priority concerns or to carry out 

the mandates of FLPMA.

Yes BLM is mandated to protect threatened, 

endangered, and candidate species and their 

habitats under the ESA.
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

September 2012 Lower Sonoran Record of Decision and Approved Resource Management Plan H-5

Importance Value Yes/No Rationale for Determination

Has qualities that warrant highlighting to satisfy 

public or management concerns about safety and 

public welfare.

No No threats have been identified.

Poses a significant threat to human life and safety 

or to property.

No No threats have been identified.

Area Considered: Gila River Terraces and Lower Gila Historic Trails

General location T.05S. R.9, 8, 7, 6, 5, 4 & 3W. (portions of) T.04S. R.9, 8, 7, 6, 5, 4 W. 

(portions of) T.03S. R. 5, 4 W. (portions of) T.02S. R. 5 W. (portions of)

T.01S. R. 5, 4, 3, 2 W. (portions of) T.04S. R. 1, 2 W. (portions of)

General description Historic trails and petroglyphs along the lower Gila River to Yuma County

Acreage 63,400 acres

Values considered Cultural, Archaeological, Historic Trails

Identification Criteria

To be considered as a potential ACEC and analyzed in RMP alternatives, an area must meet the criteria of 

relevance and importance, as established in 43 CFR 1610.7-2.

Relevance: There shall be present a “significant” historic, cultural, or scenic value; a fish or wildlife resource or other natural 

system or process; or natural hazard. This generally means that the value, resource, system, process, or hazard is 

characterized by one or more of the following:

Relevance Value Yes/No Rationale for Determination

A significant historic, cultural, or scenic value 

(including but not limited to rare or sensitive

archeological resources and religious or cultural 

resources important to Native Americans).

Yes • The trails and associated landscapes in this 

area have national significance as they are 

part of an important story about the 

peoples that have lived in, traveled through, 

and influenced the trail area. As well, the 

trails and landscapes inform us about the 

broader story of southwestern and 

transcontinental settlement, 

communications, and development. The 

cultural sites along the Gila River also have 

regional significance as they help to tell the 

story of the southwest’s indigenous 

peoples.

• Occupation and use of the Gila River 

terraces and trails spanned thousands of 

years evidenced by extensive prehistoric 

village sites and petroglyph sites, as well as

associated canals, farmsteads, intaglios, 

small camp sites, and trails. Historic uses 

included dams, water diversion features, 

trails, graves, stage station, corrals, and 

historic mines. At least 250 sites have been 

recorded within the ACEC boundary and 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

H-6 Lower Sonoran Record of Decision and Approved Resource Management Plan September 2012

Relevance Value Yes/No Rationale for Determination

are managed under a variety of

jurisdictions.

• Humans occupied this area beginning in the 

Archaic Period, nearly 8,000 to 10,000 

years ago as evidenced by the use of 

distinctive stone tools, including projectile 

points. By 300 B.C. the archaeological 

evidence begins to show the use of ceramic 

vessels and cultivation of corn. Along the

Salt and Gila Rivers, the Hohokam tradition 

was born, and is now recognized by their 

high level of sophisticated canal systems, 

used for irrigated cultivation of corn, beans,

squash, and cotton. Their pottery was often 

a buff color and decorated forms showed 

an exceptional artistry rendered in red on 

buff. Hohokam thrived in the area until the 

late 13th century, when they were forced 

to relocate to land with more abundant 

water supplies.

• The area of the Gila River within the 

proposed ACEC was located on the 

periphery of the core area of the Hohokam

tradition, but happened to be situated 

where major travel corridors developed.

• People from the Yuma / lower Colorado 

River region, called the Patayan, began to 

appear in the area by the first millennium 

A.D. The Patayan did not practice 

irrigation, but can be recognized by their 

pottery, a thin, buff colored type fired 

harder and polished. First the Desert 

Archaic and then the Patayan and Hohokam 

cultures contributed to the petroglyphs.

• A variety of cultural sites are concentrated 

along the basalt mesas and terraces 

overlooking the Gila River. The area

represents an unstudied instance: an 

amalgamation of elements from several 

archaeological cultures.

• In addition, the ACEC encloses an historic 

travel corridor with portions of the Juan 

Bautista de Anza National Historic Trail, 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

September 2012 Lower Sonoran Record of Decision and Approved Resource Management Plan H-7

Relevance Value Yes/No Rationale for Determination

Butterfield Overland Mail Route, Mormon 

Battalion Trail, and the Gila Trail following 

the same course along the Gila River 

floodplain.

• More recently, these trails and river 

corridors served explorers, emigrants, 

commercial mail and freight companies, and 

the military during the 18th and 19th 

century western expansion. In 1775, 

Captain Juan Bautista de Anza traveled 

from Tubac, Arizona to California. The Juan

Bautista de Anza National Historic Trail

commemorates this passage. In 1858, the 

Butterfield Stage Line travelled the area, 

preceded by the 1846 Mormon Battalion 

and California 49er gold rush traffic.

• While much of this ACEC has not been 

systematically studied, there are some 

recent archaeological investigations by 

recognized experts that support a long held 

supposition that this area along the Gila 

River terraces were occupied by a great 

many people over a long period of time. 

Henry D. Wallace (1989), writes, “For the 

western desert in particular, water plays a 

very important role in determining the 

patterning of prehistoric settlement and 

activities.”

• One study, entitled An Archaeological 

Survey of Enterprise Ranch, Maricopa 

County, Arizona, was written in 2007 by 

Glen Rice, et al, a well-known expert on 

Hohokam archaeology. Dr. Rice’s crew 

inventoried 2,740 acres of private land 

known as the Enterprise Ranch, which is

adjacent to BLM lands. A total of 12 sites 

were recorded, eight of which have the 

characteristics which would make them 

eligible for the National Register of Historic 

Places (NRHP). Four sites are large, 

complex village sites with ballcourts, 

compound walls, trash mounds, houses, and

plaza areas. Three sites are smaller 

residential sites or farmsteads with buried 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

H-8 Lower Sonoran Record of Decision and Approved Resource Management Plan September 2012

Relevance Value Yes/No Rationale for Determination

features. Three sites are prehistoric work 

camps. One site has historic trash and 

possible historic flood control dam. The 

remaining sites are small, artifact scatters 

and possible camps. Almost all of the sites 

date to the Colonial and Sedentary Periods 

of Hohokam tradition, roughly AD 750-

1150. Two petroglyph sites were recorded

off the edge of this study area.

• Another important cultural resource 

investigation was documented in the report 

entitled Archaeological Investigations at 

Petroglyph Sites in the Painted Rock

Reservoir Area, Southwestern Arizona, by 

Henry D.Wallace (1989), noted 

archaeologist specializing in rock art. This

study focused on the petroglyph sites that 

occur within proximity of the Gila River 

between Gila Bend and the Painted Rock 

Dam. A total of 40 petroglyph sites were

recorded in the area along the Gila River 

between Red Rock Canyon and Painted 

Rock Dam. The more than 53 known 

cultural sites in this particular study area 

along the Gila River range from petroglyph 

sites to prehistoric trail segments to artifact 

scatters.

• The research potential in this proposed 

ACEC is unmatched. This is a large body of 

unique cultural resource data because of 

the number and complexity of the sites 

present.

• The Gila River terraces and the historic 

trails along the Lower Gila River contain a 

significant collection of historic, cultural, 

archeological, and scenic values. Upon 

searching the archival map collection here 

in the Phoenix District Office, it is 

estimated that 250 cultural sites have been

recorded to date within the ACEC

boundary.
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

September 2012 Lower Sonoran Record of Decision and Approved Resource Management Plan H-9

Relevance Value Yes/No Rationale for Determination

A fish and wildlife resource (including but not 

limited to habitat for endangered, sensitive, or 

threatened species; or habitat essential for 

maintaining species diversity).

No • Small parts of this ACEC proposal provide 

dispersed habitat for quail, dove, deer, and 

a variety of other wildlife species. In 1954, a 

segregation order on the Fred J. Weiler

Greenbelt withdrew a total of 62,735 acres 

under Public Land Order 1015 for wildlife 

habitat.

• The Gila River terraces corridor and trails 

area provides habitats for resident and 

migratory wildlife, but its overall 

contribution to habitat diversity and 

connectivity is minor. It does provide some 

connectivity to upland habitats and 

movement up and down the Gila River.

• Along riparian stretches of the corridor, 

mourning and white-winged doves, 

Gambel’s quail, coyote, desert cottontail 

and black-tailed jackrabbit are found, along 

with javelina, mule deer, and bobcat. 

Resident songbirds include black and Say’s 

phoebes, ash-throated flycatcher, 

loggerhead shrike, phainopepla, verdin, 

cactus, rock and canyon wrens, black-tailed 

gnatcatcher, crissal thrasher, Abert’s 

towhee, and black-throated sparrow. In 

winter, species include sparrows and 

blackbirds. Birds of prey are present during 

the fall and winter.

A natural process or system (including but not 

limited to endangered, sensitive, or threatened

plant species; rare, endemic, or relict plants or 

plant communities which are terrestrial, aquatic, 

or riparian; or rare geological features).

No Not applicable.

Natural hazards (including but not limited to areas 

of avalanche, dangerous flooding, landslides,

unstable soils, seismic activity, or dangerous cliffs). 

A hazard caused by human action may meet the 

relevance criteria if it is determined through the 

resource management planning process that it has 

become part of a natural process.

No Not applicable.
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

H-10 Lower Sonoran Record of Decision and Approved Resource Management Plan September 2012

Importance Criteria

Importance: The value, resource, system, process, or hazard described above must have substantial significance and values 

to satisfy the “importance” criteria. This generally requires qualities of more than local significance and special worth, 

consequence, meaning, distinctiveness or cause for concern. A natural hazard can be important if it is a significant threat to 

human life or property.

Importance Value Yes/No Rationale for Determination

Has more than locally significant qualities, which 

give it special worth, consequence, meaning,

distinctiveness, or cause for concern, especially 

compared to any similar resource.

Yes • The ACEC’s basalt boulder terraces 

contain extensive examples of petroglyphs 

in the region. These petroglyph panels are a 

unique and irreplaceable part of America’s

national heritage that requires increased 

protection to prevent looting and 

vandalism.

• These river terraces and trails are part of 

important stories about prehistoric and 

historic development of the American

nation. The trails were used prehistorically 

as important trade and travel routes for 

Native Americans. In historic times, these 

trails were used by explorers, emigrants, 

commercial mail and freight companies, and 

the military during the 18th and 19th 

century Anglo and Hispanic western 

expansion.

Has qualities or circumstances that make it fragile, 

sensitive, rare, irreplaceable, exemplary, unique, 

endangered, threatened, or vulnerable to adverse 

change.

Yes • A wide diversity of significant prehistoric 

cultural sites are found along the Gila River, 

which supported robust cultures as a 

reliable source of water. The density of 

sites is higher than many surrounding areas, 

and includes extensive and important 

prehistoric petroglyph sites, village sites, 

canals, trails, and associated sites. The sites 

date from the Late Archaic, more than two 

thousand years ago, to the late 19th 

century. Many of these sites have the 

characteristics essential for a site to be 

eligible for the National Register of Historic 

Places.

• Sites are at risk due to the increased 

urbanization and encroachment and 

associated increase in activities on the

public lands. The area’s cultural values are 

exceedingly delicate and vulnerable to 

impacts from other land uses such as 

recreational OHV, mineral material sales, 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

September 2012 Lower Sonoran Record of Decision and Approved Resource Management Plan H-11

Importance Value Yes/No Rationale for Determination

mining and rights-of-way. Inundation, 

vandalism, boulder displacement, farmland 

encroachment, target shooting, erosion, 

trash accumulation, soil deposition, and 

unauthorized collection are some of the 

most common threats to these resources.

Has been recognized as warranting protection to 

satisfy national priority concerns or to carry out 

the mandates of FLPMA.

Yes • FLPMA directs BLM to manage the public 

lands “in a manner that will protect the 

quality of scientific, scenic, historical, 

ecological, environmental, air and 

atmospheric, water resource, and 

archeological values.” The relevance and 

importance of this ACEC proposal 

illustrates this area’s extensive cultural 

resource values. The potential for impacts

to the ACEC’s archaeological features and 

the Fred J. Weiler Greenbelt, make this 

ACEC a BLM management priority.

• The petroglyph panels and other cultural 

resource features are vulnerable to 

vandalism, looting, and impacts from other

land uses. The ACEC’s proximity to 

growing communities increases the 

likelihood of recreational damage occurring

to cultural resources.

• Increased use of the Gila River terraces and 

historic trails by indiscriminate OHV travel, 

target shooters, unauthorized collection of 

natural and cultural resources, vandalism, 

and rock and quarry saleable mineral 

material operations could disturb or 

destroy significant cultural sites and 

represent a major threat to the cultural and 

historic trail resources. For example, the 

use and ownership of OHVs in the Phoenix

metropolitan area and throughout the 

terraces and trail corridors is expected to 

grow dramatically over the life of the plan. 

Moreover, over 100,000 new homes are 

platted near the area as communities 

southward (Gila Bend) and northward 

(Buckeye) look forward for rapid growth as

economic expansion returns to the region.
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

H-12 Lower Sonoran Record of Decision and Approved Resource Management Plan September 2012

Importance Value Yes/No Rationale for Determination

Has qualities that warrant highlighting to satisfy 

public or management concerns about safety and 

public welfare.

No Not applicable.

Poses a significant threat to human life and safety 

or to property.

No Not applicable.

Area Considered: Saddle Mountain

General location T.10N. R. 8 & 7 W. (portions of) and T.10S. R.8 & 7 W. (portions of)

General description A 55,000+ acre block of Sonoran Desert public lands in western Maricopa 

County, west of Phoenix

Acreage 55,600 acres

Values considered Cultural, Wildlife, Scenic, Geology, Education, Sensitive Status Species

Identification Criteria

To be considered as a potential ACEC and analyzed in RMP alternatives, an area must meet the criteria of 

relevance and importance, as established in 43 CFR 1610.7-2.

Relevance: There shall be present a “significant” historic, cultural, or scenic value; a fish or wildlife resource or other 

natural system or process; or natural hazard. This generally means that the value, resource, system, process, or hazard is 

characterized by one or more of the following:

Relevance Value Yes/No Rationale for Determination

A significant historic, cultural, or scenic value 

(including but not limited to rare or sensitive 

archeological resources and religious or cultural 

resources important to Native Americans).

Yes • Saddle Mountain is a volcanic landscape 

containing unique archaeological sites, 

wildlife habitat, interpretive geology, and 

dramatic scenery. Recognized by travelers 

for thousands of years, Saddle Mountain is a 

distinctive landmark located on the fringe of

metropolitan Phoenix, Arizona--60 miles 

west of downtown. The mountain towers 

2,000 feet above the Harquahala Plain at an 

altitude of 3,037 feet above sea level.

Yes • The area contains a rich diversity of 

significant cultural sites. The density of sites 

is higher than many surrounding areas, and 

includes important prehistoric petroglyph, 

rock shelter, and geoglyph sites. The sites 

date from the Middle Archaic, several 

thousand years ago, to the middle of the 

19th century. At least five sites have the 

characteristics essential for a site to be 

eligible for the National Register of Historic 

Places. Sites are at risk due to the increased 

urbanization and encroachment and 

associated increase in recreation and 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

September 2012 Lower Sonoran Record of Decision and Approved Resource Management Plan H-13

Relevance Value Yes/No Rationale for Determination

commercial activities on the public lands.

• Saddle Mountain and the Palo Verde Hills 

region share a history spanning thousands 

of years of prehistoric cultures that

inhabited the deserts of western Arizona. 

Converging washes and uplands provided 

the Palo Verde Hills and Saddle Mountain 

area with an arboreal environment, creating 

stands of mesquite, ironwood, and Palo 

Verde trees. This environment provided 

sources of food and cover. Plus, both areas 

offered opportunities for hunting deer and 

bighorn sheep along with smaller game 

animals. An overview of cultures associated 

with this Saddle Mountain site stretch from 

Middle Archaic traditions of the Amargosa 

to the later Patayan, Hakataya, and 

Hohokam to more recent historic Yavapai 

and lastly, to the historic Anglo American.

• The volcanic upthrust of the mountain has 

created a highly visual and scenic example 

of geologic forces. Cliffs, spires, and buttes 

tinted by andesite, rhyolite, and basalt 

result in magnificent scenery. Colorful 

minerals scattered the northern skirt of the 

mountain. The mountain's pyroclastic 

rocks, distilled by eons of differential 

erosion account for the dramatic scenery 

and multicolored strata witnessed today. 

This scenery is viewed by thousands of 

motorists traveling on Interstate 10 each 

day.

A fish and wildlife resource (including but not 

limited to habitat for endangered, sensitive, or 

threatened species; or habitat essential for 

maintaining species diversity).

Yes • This area provides habitat to a number of 

big game species, including big horn sheep, 

javelina and mule deer, habitat essential for 

maintaining species complexity and 

diversity. The area provides habitat for BLM 

sensitive species, including the Sonoran 

desert tortoise, and nesting habitat for a 

variety of raptor species. Much of the area 

is Category II desert tortoise habitat. 

• The distinctive Saddle Mountain landform 

offers desert bighorn sheep habitat and an 

associated lambing area, augmented by a 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

H-14 Lower Sonoran Record of Decision and Approved Resource Management Plan September 2012

Relevance Value Yes/No Rationale for Determination

water tank developed through the

cooperative efforts of the Desert Bighorn 

Sheep Society, the Arizona Game and Fish 

Department, and BLM. Foliage creates a 

habitat valuable to a range of wildlife in the 

Palo Verde Hills, including the 

aforementioned desert tortoise, and 

approximately 162 other species. Important

or special status species within the area 

include Gila monster, kit fox, Cooper’s 

hawk, and sharp-shinned hawk. 

Additionally, prairie falcons and golden 

eagles are found in the upper reaches of 

Saddle Mountain.

A natural process or system (including but not 

limited to endangered, sensitive, or threatened 

plant species; rare, endemic, or relict plants or 

plant communities which are terrestrial, aquatic, 

or riparian; or rare geological features).

Yes The mountain’s pyroclastic rocks, coupled with 

millenniums of erosion and weathering, account 

for good rock specimen hunting, a Saddle 

Mountain pursuit known throughout the

southwest in rock collection circles. One result 

of Saddle Mountain's complex volcanic history 

has been the colorful minerals scattered the 

northern skirt of the mountain. However, the 

once plentiful fire agate, chalcedony, and calcite 

"desert roses" have become scarce due to overcollection. The mountain's pyroclastic rocks, 

distilled by eons of differential erosion, account 

for the multicolored strata that we see today. 

The mountain’s pyroclastic rocks offer potential 

geological interpretation; nearly every type of

volcanic and pyroclastic rock type can be 

located in the proposed ACEC.

Natural hazards (including but not limited to areas 

of avalanche, dangerous flooding, landslides, 

unstable soils, seismic activity, or dangerous cliffs).

A hazard caused by human action may meet the 

relevance criteria if it is determined through the 

resource management planning process that it has 

become part of a natural process.

No There are no known natural hazards at this 

time.

Importance Criteria

Importance: The value, resource, system, process, or hazard described above must have substantial significance and values 

to satisfy the “importance” criteria. This generally requires qualities of more than local significance and special worth, 

consequence, meaning, distinctiveness or cause for concern. A natural hazard can be important if it is a significant threat to 

human life or property.
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

September 2012 Lower Sonoran Record of Decision and Approved Resource Management Plan H-15

Importance Value Yes/No Rationale for Determination

Has more than locally significant qualities, which 

give it special worth, consequence, meaning, 

distinctiveness, or cause for concern, especially

compared to any similar resource.

Yes • The proposed ACEC contains bighorn 

sheep and desert tortoise, noteworthy 

priority wildlife species, outstanding 

scenery and vistas, visually exposed

geologic forces, important cultural 

resources and outdoor education 

opportunities. Paved and maintained dirt 

roads north and south of the area

represent both a benefit for ensuring 

popular regional recreation visitation, and a 

threat from easy access, OHVs, and nearby 

urbanization.

• The Saddle Mountain locale is the sole 

remaining and potentially useable corridor 

for wildlife movement north and south of 

Interstate 10. Consequently, the area

represents a regionally important wildlife 

movement area between the Gila Bend

Mountains to the south and the 

Harquahala/Belmont Mountains to the 

north. Moreover, future transportation 

mitigation could further improve 

opportunities for wildlife movement. Such

wildlife movements are critical to maintain 

genetic diversity for wildlife populations 

over large tracts of public land north and 

south of Interstate 10.

• Saddle Mountain’s striking upthrust is a 

highly visible and educational example of 

volcanic geologic resources. A one-hour 

drive from downtown Phoenix, Saddle 

Mountain is a familiar regional landmark to

community members, travelers, and urban 

recreationists over hundreds of square 

miles.

• The area offers outstanding wildlife, cultural 

and geologic study and education 

opportunities if these resource values are 

maintained in good to excellent condition. 

In particular, the mountain’s pyroclastic

rocks account for both dramatic scenery 

and interpretive geologic values.

Has qualities or circumstances that make it fragile, 

sensitive, rare, irreplaceable, exemplary, unique, 

Yes • Contrasted by the surrounding area’s rapid 

development, the Saddle Mountain area has 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

H-16 Lower Sonoran Record of Decision and Approved Resource Management Plan September 2012

Importance Value Yes/No Rationale for Determination

endangered, threatened, or vulnerable to adverse

change.

long been noted for its conspicuous natural 

condition, wildlife habitat, geology, scenery 

and recreational opportunities. These

values are all especially vulnerable to 

adverse change from increasing public use 

and commercial activities.

• Saddle Mountain’s easily assessable scenery 

and landscapes are a rarity in the locality. 

Most natural landscapes require difficult 

access and four wheel drive. Saddle 

Mountain has long been recognized for the 

quality and diversity of its recreation 

opportunities and its unusual assemblage of 

scenic, geologic and archaeological values. 

The area is noted by rock collectors for 

mineral specimens and is a popular camping 

and picnic area. Saddle Mountain is also 

noted for its remarkable springtime 

wildflower displays of poppies and other 

rare desert blooms.

• Increased use of Saddle Mountain’s public 

lands by indiscriminate OHV travel, target 

shooters, unauthorized collection of natural 

and cultural resources, and saleable mineral 

material operations likely will disturb or 

destroy wildlife habitat, scenic resources, 

and cultural landscapes. These uses 

represent a major threat. Use of OHVs is 

expected to increase as the population in of 

the Phoenix metropolitan area and 

surrounding communities near the 

mountain grow and sprawl into this area. 

Over 200,000 new homes are anticipated 

and platted north, west and east of Saddle

Mountain the area over the next 20 years.

• Over the past quarter century, the area’s 

natural conditions, wildlife habitat, scenic 

resources, and cultural values, have been 

steadily diminished and sometimes 

destroyed by peripheral road building, 

OHV travel, utility line construction, 

mining, arson, plant theft, target shooting, 

wire burning, cultural resource theft and 

vandalism, wildcat dumps and trash 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

September 2012 Lower Sonoran Record of Decision and Approved Resource Management Plan H-17

Importance Value Yes/No Rationale for Determination

dumping, abandoned and stolen cars, and 

other activities. Over 13,000 acres have 

been damaged in this fashion. Active

management of the area can both protect 

the geologic, biological, and cultural 

resources and provide excellent 

recreational opportunities based on these 

resources.

Has been recognized as warranting protection to 

satisfy national priority concerns or to carry out 

the mandates of FLPMA.

Yes • FLMPA mandates that the public lands be 

managed in a manner that will protect the 

quality of scientific, scenic, historical, 

ecological, environmental and archeological

values; and where appropriate, BLM will 

preserve and protect certain public lands in 

their natural condition. Such lands will 

provide food and habitat for wildlife and

provide for outdoor recreation. 

Additionally, FLMPA stated regulations and 

plans for the protection of public land areas 

of critical environmental concern would be

promptly developed.

• The Saddle Mountain area warrants 

protection to meet the mandates of 

FLPMA. Saddle Mountain’s dramatic

visibility and proximity to the Phoenix 

metropolitan area, along with the newly 

developing or growing communities 

surrounding near the mountain, have

presented it avid public attention. The land 

use plan’s scoping process revealed strong 

public interest in long-term protection and 

conservation of the area from citizens 

across the region. Local, regional and 

national citizen groups have proposed 

recreation SRMAs, ACECs, wilderness, 

wilderness character allocations, regional 

county park status, state park designation, 

and federal national monument designation 

over the past 30 years.

• The area offers outstanding wildlife, 

cultural, photography, geologic and outdoor 

education opportunities for youth, regional 

schools and universities, but only if the 

subject resource values are maintained in 
Appendix H. Areas of Critical Environmental Concern (ACEC) Evaluations

H-18 Lower Sonoran Record of Decision and Approved Resource Management Plan September 2012

Importance Value Yes/No Rationale for Determination

good to excellent condition. In particular,

the mountain’s pyroclastic rocks account 

for dramatic scenery, volcanic science, and 

potential geological interpretive values. 

Nearly every type of volcanic and

pyroclastic rock type can be located in the 

area.

Has qualities that warrant highlighting to satisfy 

public or management concerns about safety and 

public welfare.

No No qualities were identified.

Poses a significant threat to human life and safety 

or to property.

No No threats have been identified.