Addendum 

Palmdale Hybrid Power Project 

Biological Assessment 

AMEC Earth & Environmental, Inc. (AMEC) is providing this Addendum to the Palmdale 

Hybrid Power Project Biological Assessment, Los Angeles County, California, March 2009 

(BA) to clarify that construction and operation of the proposed Palmdale Hybrid Power 

Project (PHPP or Project) is not likely to adversely affect the federally threatened desert 

tortoise or federally endangered arroyo toad. 

Desert Tortoise

Pg. 19 – Replace the last sentence with the following: “Although there is suitable habitat on 

the north-south portion of transmission line segment 1 and the southeast portion of 

transmission line segment 2, with relatively uninterrupted habitat to the east, the lack of 

documented tortoise sightings closer than 12 miles away and the lack of observed sign on 

the Project surveys suggests that desert tortoise occurrence potential is low along these 

transmission line segments.” 

Pg. 23 – Replace Section 5.2 paragraph 2 with the following: “It is highly unlikely that desert 

tortoises are present on the power plant site. Based on discussions with Dr. Alice Karl, a 

well-known desert tortoise expert, there is a low chance that desert tortoises are present 

along the north-south portion of transmission line segment 1 and the southeast portion of 

transmission line segment 2 (Karl 2008). Based on the survey results from two years of 

focused surveys, plus other data from historic and recent surveys and assessments, desert 

tortoise are presumed to be absent on the power plant site, reclaimed water pipeline, potable 

water pipeline, natural gas supply pipeline, and sanitary wastewater pipeline. The occurrence 

potential along the north-south portion of transmission line segment 1 and the southeast 

portion of transmission line segment 2 is considered to be low. Although the proposed 

transmission line would result in the loss or disturbance of 26.84 acres of suitable habitat for 

the desert tortoise, this impact would be insignificant because: (1) desert tortoises are likely 

absent from this area; (2) based on the desert tortoise recovery plans (FWS 1994a, 2008) 

and critical habitat designation (FWS 1994b), FWS does not consider this area to be 

important to the recovery of the species; and (3) FWS has no plans to re-introduce desert 

tortoises in this portion of the desert. Also, in the unlikely event that a small number of desert 

tortoises remains in the area, the small amount of habitat loss and the dispersed nature of 

the loss would not impair the ability of these desert tortoises to find food and shelter. The 

Project therefore may affect, but is not likely to adversely affect, the desert tortoise. 

Pg. 25 – Change Condition 7 to: “No tortoises will be handled during this Project. In the 

unlikely event that a tortoise is observed in a work area, it will be avoided and allowed to 

continue unimpeded. Work may halt in the immediate area of the tortoise, a temporary 

separation fence may be erected, or the tortoise may simply be monitored. The City will 

employ whatever measures are necessary to ensure its safety.” 

Pg. 25 – Remove last paragraph of Section 5.2 and insert the following text as Condition 10 

regarding common raven measures: 
Although desert tortoises are absent from the power plant site and have low potential to 

occur along the transmission line route, desert tortoises occur within the area within the 

distance that common ravens can fly to obtain food and water. Project construction and 

operational activities could contribute to a regional increase in the common raven population, 

which could cause a regional increase in common raven predation on desert tortoise. The 

following avoidance measures will be implemented to reduce the Project’s likelihood of 

contributing to a regional increase in the common raven population. The goals of these 

avoidance measures are to: (i) educate Project staff about common raven and desert 

tortoise; (ii) reduce and preclude human-provided subsidies of food and water; and (iii) 

reduce common raven nest and communal roost sites (FWS 2008). 

i. Training and Awareness Program 

The Project’s employee training and awareness program for both the construction 

and operational phases of the Project will include education relative to common 

ravens. This program is intended to complement measures described in the FWS 

Common Raven Management Environmental Assessment (FWS 2008b). 

During both the construction and operations phases of the Project, workers will 

participate in an environmental awareness training program that will provide 

information about the biology and status of the desert tortoise and the potential for 

juvenile predation by common ravens. Ensuring that the Project staff and contractors 

are properly trained and educated regarding common ravens and the potential for 

predation on tortoises is an important component of the long-term common raven 

minimization strategy for the Project. Day-to-day operational practices can greatly 

influence the potential for common ravens to obtain food, water, and other 

anthropogenic subsidies. Workers will be made aware of the importance of not 

leaving any food or water outside of the facilities for stray animals or pets. They will 

also be encouraged to not leave any potential sources of food (such as grain, fruit, 

etc.) in uncovered truck beds, flat-bed trailers or other accessible external locations 

on their vehicles. 

During the orientation session, Project staff and contractors will be provided 

instruction pertaining to proper trash disposal techniques and water minimization 

procedures, including minimizing standing water during construction. A brochure will 

be provided that summarizes specific positive actions that will be taken and those to 

avoid. Workers will also be provided with raven nest identification training and learn 

how to differentiate a raven nest from various raptor species. They will be 

encouraged to report roosting and nesting observation to a qualified Project biologist 

or the site environmental compliance officer (such observations will be augmented by 

those of biological monitors). 

ii. Reduce/Preclude Human-Provided Subsidies of Food and Water 

To minimize the potential for food scavenging by common ravens, all outdoor trash 

cans at the Project facility will be raven-proof and equipped with self-closing lids or 

covers. An adequate number of these trash cans will be provided for employees and 

the general public at entrances and exits to the building and in parking lots. All large 

dumpsters at the facility will be equipped with tightly fitting lids. 

It is anticipated that the greatest potential for providing unintended common raven 

water subsidies resulting from Project implementation may occur during the 

construction phase of the Project because water may be used for a variety of 
purposes such as compaction, dust abatement, hydrostatic testing, and other 

relatively short-term purposes. To the extent practicable, activities that may produce 

standing or ponded water will be minimized or avoided during construction. 

Temporary surface drainage improvements such as land grading or field ditches will 

be used to conduct water away from areas with standing water. Discharge areas for 

construction activities such as hydrotesting will be selected with adequate drainage. 

Water truck fill locations will also be selected in areas that drain well. If necessary, 

gravel will be laid down, or other temporary engineering solutions (such as a leach 

field) will be installed to ensure that water truck filling operations do not provide a 

source of water for common ravens. 

Construction staff will be instructed to minimize the use of water during the 

construction phase of the Project. During the operational phase of the Project, the 

environmental awareness training program described above will help ensure that 

workers minimize sources of surface water available to common ravens during dayto-day operations. Staff will also be encouraged to immediately report and repair 

leaking faucets and/or waterlines. 

The Project design does not include any evaporation ponds, landscaping, or other 

readily available sources of surface water that might serve as a common raven 

subsidy. In addition, the site grading plans and design of the facilities will minimize 

the potential for post-construction stormwater to pond on the site. Infiltration basins 

will be designed to remain dry between rainfall events, detain storm water no longer 

than 48 hours after rainfall events, and incorporate other engineering design features 

in accordance with Federal Aviation Administration guidance. 

iii. Reduce/Preclude Common Raven Nest and Communal Roost Sites 

To the extent practicable, the power plant site structures will be designed and built to 

incorporate elements that reduce the potential for use as common raven nest and 

roost sites (e.g., communication towers, billboards, and shade structures). Following 

construction, if a feature proves to be an especially attractive nesting or roosting 

location, it will be modified or equipped with non-harmful deterrent or repellent 

devices. Common deterrents include spikes, repellent coils, post and wire (control 

wire), netting, and electric shock systems. Should a raven nest be built on a power 

plant structure, it will be removed during the non-nesting season in consultation with 

CDFG and FWS. If an active raven nest is found on the power plant site or 

transmission line that has a dead desert tortoise in or beneath it, the Ventura U.S. 

Fish and Wildlife Office will be contacted immediately. 

Arroyo toads – Replace Section 5.1 of the BA with the following.

Designated critical habitat for arroyo toads is located 2-3 miles south (upstream) of where 

transmission line segment 2 crosses Little Rock Creek. If arroyo toads are present in this 

critical habitat area, arroyo toads, larvae, and egg masses could potentially move 

downstream during years of favorable rainfall when water is present. However, the most 

recent recorded sighting was in 2001 (CDFG 2009), approximately three miles upstream 

from the Project’s proposed crossing of Little Rock Creek. To reach the transmission line 

crossing location, an arroyo toad individual, larva, or egg mass would need to navigate 

across Little Rock Reservoir and Little Rock Dam, which is highly unlikely. 
Focused breeding season surveys were conducted in 2009 in the Little Rock Creek area 

(where transmission line segment 2 crosses Little Rock Creek), and no arroyo toad adults, 

juveniles, eggs, or larvae were detected. Based on the intermittent flow at this location 

(drying out by early summer; dry throughout some years), marginal habitat (lack of suitable 

stream and burrowing substrate), and the absence of arroyo toads during 2009 focused 

surveys, it is highly unlikely arroyo toads utilize this section of Little Rock Creek and the 

Project therefore will have no effect on the arroyo toad. No additional avoidance and 

minimization measures (beyond what the Project is already proposing to avoid and minimize 

impacts to the Little Rock Creek Significant Ecological Area) are necessary. 

References

Pg. 27 – Add the following reference: 

United States Fish and Wildlife Service (FWS). 1994a. Desert tortoise (Mojave population) 

Recovery Plan. U.S. Fish and Wildlife Service, Portland, Oregon. 73 pp plus 

appendices. 

---. 1994b. Final rule: determination of critical habitat for the Mojave population of the 

desert tortoise. FR 59 (26):5820-5866. 

---. 2008a. Draft revised recovery plan for the Mojave population of the desert tortoise 

(Gopherus agassizii). U.S. Fish and Wildlife Service, California and Nevada Region, 

Sacramento, California. 209 pp. 

---. 2008b. Final Environmental Assessment to Implement a Desert Tortoise Recovery 

Plan Task: Reduce Common Raven Predation on the Desert Tortoise. Ventura, 

California.