1.1 MB pdf - Bolsa Chica Lowlands Restoration Project
1.1 MB pdf - Bolsa Chica Lowlands Restoration Project 1.1 MB pdf - Bolsa Chica Lowlands Restoration Project
SECTION 2 Problem Formulation The Problem Formulation presents and evaluates information that will be used to develop and focus the Analysis component of the ERA. Much of the information presented in this section was taken from the Scoping Assessment (CH2M HILL, 1998b) and the Ecological Effects Characterization (CH2M HILL, 1999). The end product of the Problem Formulation is an ecological conceptual site model that describes potential ecological receptors (plant and animal species) that may be affected at the site, COPECs, important site aspects to be protected (referred to as assessment endpoints), and means by which the assessment endpoints will be evaluated (called measures). The information used to develop the ecological conceptual site model includes the following: • Site Background – provides a description of the physical setting, climate, historical activity at the site, and previous site investigations that have been conducted. • Ecological Characterization – provides a description of the ecological setting, including identification of habitats and potential ecological receptors. • Chemicals of Potential Ecological Concern – provides a description of the preliminary identification of COPECs based on the previous Tetra Tech (1996) sampling efforts, including preliminary evaluations of data usability, background concentrations, and comparisons of preliminary data to screening effect levels to identify COPECs. • Assessment Endpoints and Measures – provides a description of the development of assessment endpoints (important aspects of the site to be protected), risk hypotheses (statements of how potential exposure to stressors could occur at the site), and measures (predictors of assessment endpoints and the means by which the risk hypotheses will be evaluated). 2.1 Site Background This section describes physical characteristics of the site including location and climate, provides a review of the relevant site history, and summarizes previous investigations conducted at the site. 2.1.1 Location/Setting The physical setting of the Lowlands and surrounding area was described by Jones and Stokes (1995), OCEMA (1996), and Tetra Tech (1996), and the relevant portions of those descriptions are summarized here. Figure 1-1 shows the location of the Bolsa Chica Lowlands study site relative to adjacent, interconnected, marine/estuarine habitat at Huntington Harbor and Seal Beach National Wildlife Refuge (NWR). The Lowlands project area includes about 880 acres of terrestrial and wetland habitat recently acquired from the Koll Real Estate Group, 306 acres in the Bolsa Chica Ecological Reserve, and about 25 acres of Southern California Metropolitan Water District (MWD) property. Extensive and highly urbanized watersheds drain into these three closely linked marine/estuarine systems. SAC/143368(002.DOC) 2-1 ERA REPORT 7/31/02
SECTION 2:PROBLEM FORMULATION The Lowlands lie east of the Pacific Coast Highway, between the higher elevation Bolsa Chica Mesa to the northwest and “Edwards Thumb” and Huntington Mesa to the eastsoutheast. Surface topography is subdivided into several general areas (e.g., Pocket Area, Fieldstone Property, Bolsa Chica Ecological Reserve, and the large central portion of the Lowlands), but the entire study area has relatively little topographic relief. For sampling purposes, the most important surface features (other than the general area designations and their priorities) are the network of levees and roads that divide the Lowlands into approximately 60 Cells. These Cells, along with surface water bodies and drainage pathways, provide the topographic focus for the ERA. Residential areas exist to the northeast of the Lowlands, between the upland/mesa areas to the north (Bolsa Mesa) and east-southeast (Edwards Thumb and Huntington Mesa), and on the upland/mesa areas themselves. Within the Lowlands, the primary land use is oil field operation (including onsite wells throughout the site and the Whipstock area, with wellheads for some wells that extend offshore). The Ecological Reserve is partially accessible to the public through a boardwalk; entry is from an access point (with a parking area) along Pacific Coast Highway. Beaches along Pacific Coast Highway opposite the Lowlands are within the Huntington State Beach and are used for surfing, swimming, and other recreational purposes. 2.1.2 Climate The climate of the project area is characterized by warm, dry summers, tempered by ocean breezes, with mild winters. The annual average rainfall of about 12 inches occurs primarily between November and April. Fog and low clouds typically occur from February to April. In summer, morning fog and low clouds usually persist until mid-afternoon, keeping summer temperatures mild. The average daily temperature in the summer is 18 degrees Celsius (C), winter temperatures average 11 degrees C, and annual temperatures range from 1.7 to 38 degrees C. The prevailing winds, which blow onshore from the southwest, help lower summer temperatures and dissipate the summer fog. In autumn, strong, gusty winds from the inland deserts, known locally as Santa Ana winds, cause unseasonably warm days. 2.1.3 Site History During the late 19th and early 20th centuries, agricultural use of uplands north and east of the site may have included livestock grazing and crop farming that might have involved the use of fertilizers and some kinds of insecticides (Jones and Stokes, 1995; OCEMA, 1996). Many of these agricultural areas drained into the Lowlands, and runoff may have contained certain metals and pesticides. Some of the metals are related to the application of pesticides or herbicides or to repeated irrigation and runoff cycles. In the 1890s, the Bolsa Chica Gun Club used the Lowlands as a wildlife preserve for recreational hunting and fishing. Recreational hunting by Bolsa Chica Gun Club members ended in 1964 (Jones and Stokes, 1995; OCEMA, 1996). One of the events that has most profoundly affected water quality was the construction of tide gates between Inner and Outer Bolsa Bay by the Bolsa Chica Gun Club in 1899. With the resulting reduction in the tidal prism, the natural opening at Los Patos (now Warner Avenue) between Bolsa Bay and the Pacific Ocean silted in. A new opening that connected Outer Bolsa Bay to Sunset Bay ERA REPORT 2-2 SAC/143368(002.DOC) 7/31/02
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SECTION 2<br />
Problem Formulation<br />
The Problem Formulation presents and evaluates information that will be used to develop<br />
and focus the Analysis component of the ERA. Much of the information presented in this<br />
section was taken from the Scoping Assessment (CH2M HILL, 1998b) and the Ecological<br />
Effects Characterization (CH2M HILL, 1999). The end product of the Problem Formulation<br />
is an ecological conceptual site model that describes potential ecological receptors (plant<br />
and animal species) that may be affected at the site, COPECs, important site aspects to be<br />
protected (referred to as assessment endpoints), and means by which the assessment<br />
endpoints will be evaluated (called measures). The information used to develop the<br />
ecological conceptual site model includes the following:<br />
• Site Background – provides a description of the physical setting, climate, historical<br />
activity at the site, and previous site investigations that have been conducted.<br />
• Ecological Characterization – provides a description of the ecological setting, including<br />
identification of habitats and potential ecological receptors.<br />
• Chemicals of Potential Ecological Concern – provides a description of the preliminary<br />
identification of COPECs based on the previous Tetra Tech (1996) sampling efforts,<br />
including preliminary evaluations of data usability, background concentrations, and<br />
comparisons of preliminary data to screening effect levels to identify COPECs.<br />
• Assessment Endpoints and Measures – provides a description of the development of<br />
assessment endpoints (important aspects of the site to be protected), risk hypotheses<br />
(statements of how potential exposure to stressors could occur at the site), and measures<br />
(predictors of assessment endpoints and the means by which the risk hypotheses will be<br />
evaluated).<br />
2.1 Site Background<br />
This section describes physical characteristics of the site including location and climate,<br />
provides a review of the relevant site history, and summarizes previous investigations<br />
conducted at the site.<br />
2.<strong>1.1</strong> Location/Setting<br />
The physical setting of the <strong>Lowlands</strong> and surrounding area was described by Jones and<br />
Stokes (1995), OCEMA (1996), and Tetra Tech (1996), and the relevant portions of those<br />
descriptions are summarized here. Figure 1-1 shows the location of the <strong>Bolsa</strong> <strong>Chica</strong> <strong>Lowlands</strong><br />
study site relative to adjacent, interconnected, marine/estuarine habitat at Huntington<br />
Harbor and Seal Beach National Wildlife Refuge (NWR). The <strong>Lowlands</strong> project area includes<br />
about 880 acres of terrestrial and wetland habitat recently acquired from the Koll Real Estate<br />
Group, 306 acres in the <strong>Bolsa</strong> <strong>Chica</strong> Ecological Reserve, and about 25 acres of Southern<br />
California Metropolitan Water District (MWD) property. Extensive and highly urbanized<br />
watersheds drain into these three closely linked marine/estuarine systems.<br />
SAC/143368(002.DOC) 2-1 ERA REPORT<br />
7/31/02
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