B08_Attachment_5-RemovalActionWorkplan.pdf

Removal Action Workplan for Vista Point Trail Renovations in Sausalito, CA

Golden Gate National Recreation Area

Project PMIS No. 167755/186589

Vista Point Multi-Use Connections to Fort Baker

Dec. 19, 2023 ii iii

Table of Contents List of Figures ................................................................................................................... iv

List of Acronyms ............................................................................................................... v

Introduction

Background

Remedial Action Objectives

Cleanup Levels and Chemicals of Concern

Project Health and Safety

Temporary Facilities and Controls

Soil Management

Air Monitoring

Project Documentation

Figures

Tables, Appendices and Sample Logs iv

Figures

1. Site Location Map

2. Site Plan

3. Proposed Excavation Plan with Historical Sample Locations

3A. Proposed Excavation Plan Station 10+00 to 14+00

3B. Proposed Excavation Plan Station 14+00 to 18+00

3C. Proposed Excavation Plan Station 18+00 to 22+00

3D. Proposed Excavation Plan Station 22+00 to 25+00

3E. Proposed Excavation Plan Station 25+00 to 28+00

4. Proposed Stockpile Management Area

5. Work Zones

6. Proposed Confirmation Sampling Plan

7. Anticipated Local Truck Haul Routes

8. Proposed Air Monitoring Locations v

Acronym List Acronym Definition

ACMs Asbestos Containing Materials

ARAR Applicable or Relevant and Appropriate Requirement

BCA

Bgs bias-corrected accelerated below ground surface

BMP Best Management Practices

CAMP Community Air Monitoring Plan

CCR California Code of Regulations

CEQA California Environmental Quality Act

CQA Construction Quality Assurance

COC contaminant of concern

DTSC California Department of Toxic Substances Control

EC Environmental Contractor

EKI

ESA

Erler & Kalinowski Incorporated

Endangered Species Act

ESA Environmentally Sensitive Area

GC General Contractor

GGNRA Golden Gate National Recreation Area

HASP Health and Safety Plan

HHRA Human Health Risk Assessment

HAZWOPER Hazardous Waste Operations and Emergency Response

IWP

KM

Implementation Work Plan

Kaplan-Meier mg/kg milligrams per kilogram

NEPA National Environmental Policy Act

NPS

MVUE

National Park Service minimum variance unbiased estimator

OSHA Occupational Safety and Health Administration

PID photoionization detector vi

Acronym Definition

QA/QC quality assurance/quality control

QAPP Quality Assurance Project Plan

RAO Remedial Action Objective

RAP Remedial Action Plan

RAW Removal Action Workplan

RCRA Resource Conservation and Recovery Act

RACR Removal Implementation Completion Report

Roux Roux Associates, Inc.

RSL Regional Screening Level

SFBRWQCB San Francisco Bay Regional Water Quality Control Board

SMP Soil Management Plan

SWPPP Storm Water Pollution Prevention Plan

TBD To be determined

UCL Upper Confidence Limit

USA Underground Service Alert

USEPA U.S. Environmental Protection Agency

UST underground storage tank

Introduction This Removal Action Workplan (RAW) is incorporated into the construction contract documents for the Vista Point Trail renovations in the vicinity of the Golden Gate Bridge Dana Bowers Vista Point

– North Approach in Sausalito, California (Site), located just north of the Golden Gate Bridge along the east side of Highway 1/101 in Sausalito, California (Figure 1). The Site is specifically identified as the trail area associated with proposed renovations, as illustrated on Figure 2. This RAW describes the remedial actions, associated remedial action objectives (RAOs), as well as the implementation requirements for the lead- and zinc-impacted soil at the Site during grading activities.

Background The Golden Gate Bridge and Highway District were incorporated on December 4, 1928, with construction of the Golden Gate Bridge from 1933 to 1937. The original protective coating applied to the bridge consisted of red paint (68% lead by weight). To address corrosion in 1965, a paint replacement program was implemented which included removal of paint, rust, and mill scale by open sand blasting of the bridge, and repainting. The lead-based paint removal was completed by 1975 on the South Approach, and by 1994 on the North Approach. These maintenance activities resulted in the accumulation of sand blast and lead-based paint material in the vicinity of both bridge approaches.

The land supporting the Bridge, viaducts, and maintenance structures and facilities were transferred from the Department of Defense to the Department of the Interior over several years beginning around October 1, 1994, and the Bridge District maintains a permit to operate.

Based on previous soil sampling conducted in the area, surface soil in the proposed work area has been impacted with lead, resulting from wind deposition of historical lead-based paint from the Golden Gate Bridge during sandblasting activities. The removed paint also has the potential for zinc impacts, as zinc was present in the paint. The historical soil sampling results are shown in Figure 3.

The GGNRA has proposed to renovate the Vista Point Road as described above. In preparation for the trail improvements, additional soil samples were collected along the proposed trail by Langan Treadwell Rollo in 2015.

Remedial Action Objectives RAOs are designed to protect human health and the environment from releases and exposures to hazardous substances by incorporating information of Site contaminants of concern (COCs), current environmental conditions, potential exposure pathways, and anticipated future use of the

Site (i.e., recreational). Site characterization has revealed the presence of lead and zinc in soil from nearby off-Site sources. As described above and as shown in the excavation plan (Figure 3), future improvement plans for the Site include construction of the bicycle and pedestrian path and will require excavation and disposal of approximately 570 cubic yards of soil.

RAOs have been established that will protect human health and the environment at the Site. The RAOs for actions as proposed in the RAW are as follows:

1. Protect occupational/construction workers and off-Site receptors from potential exposure to COCs through implementation of a soils management plan (SMP);

2. Protect recreational receptors from potential exposure to COCs; and

3. Compliance with Applicable or Relevant and Appropriate Requirements (ARARs).

Implementation of and compliance with the SMP described herein is an integral part of the remedy and it addresses soil contamination that may be encountered during Site improvements and will help to mitigate or prevent exposure to construction workers and future Site users.

Cleanup Levels and Chemicals of Concern Lead and zinc have impacted surface soil in the Golden Gate Bridge North and South approach sites. Elevated lead and zinc concentrations are generally co-located, as both lead and zinc are present in the lead-based paint deposited on near surface soils by the wind from historical sandblasting activities at the Golden Gate Bridge. Concentrations of lead from the North Approach have been detected at a maximum concentration of 15,900 milligrams per kilogram (mg/kg) at a depth of 4-inches below ground surface (bgs), and from the South Approach at a maximum concentration of 13,400 mg/kg at a depth of 24-inches bgs. Concentrations of zinc in the South Approach shallow soils were detected at a maximum concentration of 3,680 mg/kg in surface soil to depths of 24-inches bgs. Additional samples collected in 2011 detected lead in shallow soil at a maximum concentration of 5,330 mg/kg, and in 2015 at a maximum concentration of 3,200 mg/kg at the North Approach. Soil samples have not been analyzed for zinc in the North Approach portion of the Site. However, based on the presence of zinc in soils at the South Approach and the documented co-located nature of lead and zinc associated with paint deposits, zinc has been assumed to be present at the North Approach.

Though the maximum concentration of zinc of 3,680 mg/kg detected in 1999 does not exceed the U.S. Environmental Protection Agency (USEPA) Regional Screening Level (RSL) for residential soil of 23,000 mg/kg, zinc is retained as a COC since samples have not been analyzed from the North Approach project area of the Site. The Bridge District determined that lead and zinc impacts were co-located, and occurrences of zinc would be addressed by remedies for lead in soil, therefore lead is the primary COC for the Site.

Lead has been shown to be present at concentrations that exceed regulatory thresholds in near surface soils in portions of the work area, and zinc has not been analyzed in the work area.

Therefore, a potentially complete exposure pathway exists for future recreational users, occupational/construction workers, or Site workers to impacted near surface soils. This exposure could involve risk to human health resulting from inhalation, ingestion, and/or dermal contact with the potentially impacted shallow soil.

This project will achieve DTSC Human Health Risk Assessment (HHRA) Note 3 modified screening level (DTSC-SL) for residential soils of 80 mg/kg for lead and the USEPA RSL for residential soils of 23,000 mg/kg for zinc as the Site cleanup goals. This was determined to allow for unrestricted use of areas that will be open to the public. The remediation within the earthwork area will be considered complete if the 95% upper confidence limit (UCL) concentration of the confirmation samples for lead and zinc meets screening criteria. The 95% UCL for all confirmation sample results will be calculated in accordance with USEPA guidance (USEPA, 2002) utilizing ProUCL software and is described below.

The removal action consists of over-excavation and off-site disposal of contaminated soil. Shallow soil impacted with lead and zinc within the project area will be excavated, stockpiled, characterized, and transported to an appropriate, permitted off-site facility for disposal. Excavation will require equipment that will generate dust emissions. Suppressant, water spray, and other forms of dust control may be required during excavation, and workers may be required to use personal protective equipment to reduce exposure to COCs. Confirmation soil samples will be collected following soil removal and analyzed for applicable COCs to confirm soil concentrations meet screening criteria.

If confirmation soil samples have concentrations of COCs exceeding screening levels, over-excavation will be performed until confirmation samples do not exceed the applicable screening levels.

Implementation of the remedial alternative will require soil stockpiling following excavation and characterization on-Site prior to disposal. To achieve the RAOs, it is expected that some shallow soil from the Site will need to be removed, beyond what is proposed for construction purposes.

However, based on previous sampling, some areas of the trail (generally outside of the wind shadow) currently meet the cleanup criteria (Figure 3). According to the proposed construction drawings, the top 1 foot of soil will be excavated from most portions the Site for placement of aggregate base (AB) and asphalt, with some areas towards the northern portion of the trail requiring fill, and with deeper excavation towards the southern portion of the trail. The proposed areas of cut and fill are shown on Figures 3, and 3A through 3E. The approximate width of excavation throughout the trail is 20- to 25-feet across, with the maximum approximate width of groundwork for both excavation and fill of 50-feet across. The estimated volume of soil expected to be removed is 570 cubic yards (850 tons), however, over-excavation may increase soil excavation volumes depending on confirmation sampling results. Excavated soil is proposed for stockpiling and future characterization prior to off-site disposal.

Project Health and Safety The following sections describe the health and safety measures, such as preparation of a Health and Safety Plan (HASP), monitoring, and other work controls that will be implemented to maintain safe work environment.

Health and Safety Plans The Contractor is responsible for the health and safety of their own employees and will prepare a Site-specific HASP complying with 29 CFR 1910.120 OSHA HAZWOPER, 29 CFR 1926.62 OSHA Lead in Construction to protect and inform workers who may handle or contact hazardous wastes, hazardous materials, or contaminated soil at the Site while conducting earthwork activities. The HASP must include dust monitoring, action levels, and work stoppage provisions that will be followed during construction activities. Earthwork activities constituting Cal/Occupational Safety and Health Administration (OSHA) Hazardous Waste Operations and Emergency Response (HAZWOPER) “clean-up operations” or “hazardous substance removal” must be conducted by HAZWOPER-trained personnel. Soil that is visibly stained, discolored, oily, or has a noticeable solvent-like or hydrocarbon odor should be handled only by HAZWOPER-trained personnel until it is determined by a qualified person that such precautions are not warranted.

Health and Safety Officer

A Site Health and Safety officer (SHSO) identified in the HASP will be on Site at all times during excavation activities to ensure that all health and safety measures are maintained. The SHSO and all onsite workers will have authority to direct and stop (if necessary) all construction activities to ensure compliance with the HASP.

Public Health Protection Measures The general public will be protected through the following measures:

• The Site and stockpile staging area will be fenced to restrict access;

• Exposed soil at the construction Site will be watered at least twice a day, or at the sign of visible dust, to prevent visible dust from migrating off-Site;

• Soil stockpiles will be covered and secured when not in active use;

• Berms or barriers will be placed around stockpile perimeters to prevent off-Site migration of soil, especially during rain events;

• Water will be misted or sprayed during the loading or unloading of soil onto or off trucks to minimize visible dust migrating off-Site;

• Trucks transporting contaminated soil will be covered with a tarpaulin or other cover;

• The wheels of the trucks exiting the Site will be cleaned prior to entering public streets;

• Public streets will be swept daily if soil is visible; excavation and loading activities will be suspended if winds exceed 20 miles per hour

Monitoring and Work Controls The Contractor will provide a means of minimizing and controlling dust levels at locations where restricted and/or potentially impacted soils are observed. Airborne dust monitoring will be conducted by the EC as described herein.

Temporary Facilities and Controls The GC will provide and maintain temporary facilities and controls during implementation of the corrective actions as described in the following sections.

Soil Staging Facilities The GC will construct and maintain soil staging facilities for stockpiling excavated material, in the location shown in Figure 4. Soil segregation details, including stockpiling and best management practices (BMPs) are further discussed below. The GC will also establish decontamination areas in which dust, debris, and oil will be removed from the equipment prior to leaving the Site.

Decontamination methods are discussed below.

Soil Stockpile Management

Soil stockpiles should be placed in dumpsters or on top of at least one layer of 10 mil polyethylene sheeting (or equivalent) to prevent contact with the ground surface. Stockpiles should be covered with a tarp or sheeting, and top sheeting must be adequately secured so that all surface areas are covered, when not actively being worked.

Additionally, stockpiles must be managed in compliance with storm water runoff regulatory requirements. A project specific Stormwater Pollution Prevention Plant (SWPPP) is required for any construction project involving earth disturbing activities greater than one acre in area.

Contractor shall use the following measures to manage on-Site stockpiles:

• Excavated soil should be placed directly onto consolidation areas to minimize the potential for cross contamination, where possible. Soil excavation, handling, and stockpiling shall be performed in a manner which limits and controls the depositing of excavated material across areas already excavated (i.e., non-impacted material).

• If temporary stockpiling soil is necessary on the trail, soil should be stockpiled in areas where excavation work still needs to be performed. Plastic sheeting should be used below temporary stockpiles to minimize the potential of cross contamination and to demark the extent of stockpiled soil.

• All soil stockpiles will be securely covered with plastic sheeting (minimum 10 mil thickness) at the end of each workday during Site work. Soil stockpiles will be managed in accordance with procedures outlined in this plan and the project specific SWPPP.

• Silt fencing, hay bales, straw rolls, polyethylene covers, or other BMPs shall be implemented and maintained as necessary to control storm water run on and/or runoff from all stockpiles, as specified in the Site SWPPP. At a minimum, stockpiles shall be covered prior to inclement weather.

• Construction debris (if encountered) shall be removed from the excavated soil and stockpiled separately for off-Site disposal.

• Stockpiles must be inspected daily during active construction and following significant rain events, to ensure dust control, storm water runoff and erosion control measures are functioning adequately. If it is determined that BMPs are not in place, the GC will be responsible for implementing the BMPs as soon as possible.

Personal Hygiene/ Decontamination/ First Aid Facility The GC will supply and maintain a personal hygiene/ decontamination facility and emergency first aid facility at the Site throughout the duration of the construction activities. The emergency first aid facility may be located within the personnel hygiene/ decontamination facility.

Soil Management

Dust Control The dust control plan described below contain measures to protect construction workers and the public during excavation and dust-generating activities at the Site. The dust control plan will be implemented through the implementation of engineering controls, to minimize generation of dust and the potential off-site migration of chemicals in soil from the Site. Additional details on the dust control measures, such as dust monitoring intervals, protocols, and action levels, that will be implemented during construction are further discussed in below.

Excavation Equipment and Methods According to the proposed Site improvement plans, shallow soil excavation will be required along most of the proposed trail, including rest area turn-outs, for the placement of 9-inches of AB, and 3 inches of asphaltic concrete, with a maximum up to 5.86 feet of excavation in portions of the trail (Figures 4 and 4A through 4E).

As part of a removal action, the vertical extent of the excavation may be extended to over-excavate soil that exceeds applicable screening levels. If over-excavation is required to mitigate additionally identified impacts, based on confirmation sample results, it will be completed in accordance with this IWP. All confirmation sampling results will be used to calculate the 95% UCL for lead and zinc as described below. If the 95% UCL concentration of the confirmation samples exceed the screening levels, additional soil will be removed in 3-inch lifts within the horizontal extent of the trail excavation area, extending halfway laterally to the nearest adjacent confirmation sample (with results below screening criteria), in either direction. Following over-excavation of any areas with soil COC concentrations exceeding applicable screening levels, additional confirmation samples will be collected from the over-excavation bottom to confirm COCs have been removed, and the 95% UCL will be re-calculated with the new results. Soil excavated from these areas will be handled as described below. Confirmation sampling protocols are also outlined below.

If over-excavation is required based on confirmation sampling results exceeding screening levels, the GC construction contractor will remove soil beneath the exceedance 3-inches vertically. Over-excavation will continue vertically in 3-inch increments, until confirmation sampling indicates soil concentrations of COCs do not exceed screening levels. The area of over-excavation will not extend horizontally away from the extent of the proposed trail. Areas beyond this extent will be addressed by the Bridge District in a Phase 2 Remedial Action.

Portions of the trail require fill to raise the surface grade, and over-excavated areas may require backfilling with virgin quarry materials and/or imported clean fill, as needed, to meet the finished grade prior to placement of asphalt paving. Any proposed imported fill material will be evaluated prior to import to the Site in accordance with the 2001 DTSC Information Advisory Clean Imported Fill Material Fact Sheet (DTSC, 2001), to meet sampling requirements and applicable DTSC screening criteria.

Soil excavated during the construction activities will be loaded into trucks and staged nearby at a stockpile staging area, for waste characterization prior to transport for off-Site disposal (Figure 4).

Based on the estimated depth of the groundwater beneath the Site (around 42 feet below ground surface (bgs), it is not expected that groundwater will be a concern for the development project, and dewatering is not anticipated based on the proposed improvements construction plans.

Decontamination Plan Proper decontamination methods of equipment will take place to reduce the potential tracking of waste off-site. Decontamination methods will consist of brushing, vacuuming, and/or wetting the truck haul routes and utilizing rumble plates within or immediately adjacent to excavation areas in the contaminant reduction zone (Figure 5) to remove soil adhering to equipment. The decontamination methods are listed and described further below.

Surface Drainage and Erosion Control The GC will prepare a Stormwater Pollution Prevention Plan (SWPPP) to be used during the construction activities. The SWPPP will be in accordance with regulatory requirements for stormwater pollution management. It will include BMPs to reduce the sediment load of stormwater runoff from the Site and prevent stormwater from running from active work areas onto undisturbed areas.

Excavation of Impacted Soil Based on existing soil sampling data and the proposed trail construction plans, initial excavation limits are shown on Figure 3, and are anticipated to include removal of approximately 570 cubic yards (850 tons) of soil. Excavated soil will be loaded into trucks and transferred to the soil staging facility described in Section 2.3.1. It is anticipated that this project can be accomplished using standard excavation and backfilling equipment.

Locations with identified soil impacts exceeding screening criteria based on previous soil sampling for lead that are not proposed for excavation within the project area for trail improvements will be over-excavated prior to proceeding with confirmation sampling and backfill. The GC will perform excavation as described below for over-excavation of soil exceedances at the following locations:

• NS4 to a depth of at least 8-inches bgs (Figure 3C); and

• NP13A to a depth of at least 9-inches bgs (Figure 3D).

Once excavation and grading are completed to the proposed excavation limits in one or more portions of the excavation areas, the EC will collect confirmation soil samples for laboratory analysis. Confirmation soil sample collection and analysis, including protocols for over-excavating and re-sampling if initial confirmation sampling results exceed cleanup goals, is discussed further below. The vertical and/or horizontal limits of the excavations will be extended, if necessary, in the areas where confirmation soil sample analytical data indicate that COCs are present above soil cleanup levels.

Sampling and Analysis Plan After soil has been excavated and graded for trail construction, the exposed soil surface will be sampled by the EC to confirm removal of soil containing COCs above soil cleanup levels. A Sampling and Analysis Plan (SAP) for the Site is included in Tables 1 and 2, with supporting information in Table 3 and 4 for sampling containers, handling, and reporting limits for analyses.

The following section describes the collection, and analytical methods for confirmation sampling and stockpile sampling of onsite soils, sample handling, and quality assurance protocols. The locations for the proposed confirmation soil samples are shown on Figure 6.

Sampling Locations Following excavation completion, the construction contractor or their EC will collect confirmation exit samples from the trail excavation bottom approximately every 50-linear feet, at least 5-feet from the horizontal extent of the excavation on either side of the trail at each location, according to Figure 6. Following over-excavation, as needed, an additional confirmation exit sample will be collected from the base of the over-excavated sidewall.

Soil Sampling Protocol Soil sampling for confirmation samples, including from any over-excavation areas, will be performed using hand methods (slide hammer, trowel, or hand auger) in increments of 3-inches to a total depth of 6-inches bgs below the base of the excavation, at least 5-feet from the horizontal extent of the excavation on either side of the trail. Soil samples will be collected in two 3-inch intervals, and only the shallowest sample will be analyzed initially. If the shallow sample exceeds screening levels, the deeper sample (e.g., 3- to 6-inches bgs) will be analyzed. If the deeper sample meets remedial objectives, additional excavation will be performed to this bottom depth and will be considered complete. This process will be repeated until all confirmation sample locations meet screening levels following over-excavation. The soil samples will be collected at the designated intervals either by capping the stainless steel liner tube on either end with a Teflon tape and a plastic cap at the appropriate sample interval depths, and labeling, or placing the samples into the appropriate sample jar, labeling, and storing.

One 4-point composite sample will be collected for every 250 cubic yards (CY) of material generated up to 1,000 CY and one additional sample per each additional 500 CYs, unless the planned disposal facility allows for a modified characterization profiling. Composite environmental samples will be obtained using a pre-decontaminated or disposable hand trowel and transferred into laboratory-supplied glass containers.

Equipment rinsate blank samples will be collected for quality assurance/quality control (QA/QC) at a frequency of one per day of confirmation sampling. QC samples analyzed by the laboratory for all samples will include matrix spike/matrix spike duplicates (MS/MSD) at a frequency of 10 percent of the primary samples. Sample analytical results will be reviewed for any detections of analytes to ensure proper decontamination methods are used during sampling.

Equipment rinsate blank samples will be collected from a piece of non-dedicated sampling equipment, by running deionized water over the equipment and collecting the water in laboratory-supplied glass containers.

Sample Handling, Designation and Labeling Each confirmation sample will receive a unique designator. Unique designators may be an alphanumeric combination that signifies the location, depth, etc. The following format will be used to label samples:

• Survey station number (e.g., 15+00);

• Depth in inches (e.g., 6 for 6-inches) from initially proposed excavation depth (i.e., the first confirmation bottom depth will be 3-inches bgs);

• Left or right side of trail (looking up-station).

• The survey station number is followed by a dash, then the depth in inches and the cardinal direction. For example, a sample collected at survey station number 15+00 at a depth of 3-inches on the left side of the trail would be identified as 15.00-

3-LEFT.

QA/QC samples collected will be designated as “EB” for equipment blank, followed by a dash and the date in day/month/year (DDMMYY) format. For example, a field equipment rinsate collected on June 24, 2023, would be identified as EB-062423. All QA/QC samples will be recorded on a sampling log sheet that will identify the associated sampling equipment that the rinsate was collected from.

Each sample will be labeled with sample identification, date and time collected, sampler name and firm, and preservative (if applicable).

Samples will be stored in a cooler with double-bagged ice to maintain them at approximately 4°C prior to their delivery to the designated laboratory.

The chain of custody record will also be used to document samples collected and the analysis requested. Field personnel will record the following information on the chain-of-custody record:

• Project name

• Project number

• Name and signature of sampler

• Destination of samples (laboratory name)

• Sample identification number

• Sample location, description, and depth (when applicable)

• Date and time of collection

• Number and type of containers filled

• Analysis requested

• Preservatives used

• Signatures of individuals involved in custody transfer (including date and time of transfer)

• Laboratory purchase order number

• Shipping company air bill number (if applicable)

• Relevant remarks related to sample analysis (such as samples selected for MS/MSD analysis)

Unused lines on the chain of custody record will be crossed out and initialed. Completed chain of custody records will be placed in a plastic bag and taped to the inside of the lid of the container used for sample transport. Copies of the chain of custody record (and air bill, when applicable) will be retained and filed by field personnel before the containers are shipped. A copy of the chain of custody record will be delivered to the EC project manager or designee as soon as possible after sampling.

Soil Analytical Methods Confirmation exit samples will be analyzed for COCs only: lead and zinc by USEPA Method 6020 on a dry-weight basis (including analysis for percent moisture by USEPA Method 8000).

Stockpile samples for waste characterization will be analyzed for: California Administrative Manual (CAM) 17 Metals by USEPA Method 6020/7471B, asbestos by CARB 435, volatile organic compounds (VOCs) by USEPA Method 8260B, and total petroleum hydrocarbons (TPH) as diesel (TPH-d), as gasoline (TPH-g) and as motor oil (TPH-mo) by USEPA Method 8015B/8015Bm on a dry-weight basis (including analysis for percent moisture by USEPA Method 8000).

Water Analytical Methods Equipment rinsate blank water samples for QA/QC will be analyzed for: lead and zinc by USEPA Method 6020.

Decontamination water samples will be analyzed, as-needed, for: CAM 17 Metals by USEPA Method 6020, VOCs and TPH-g by USEPA Method 8260B, and TPH-d, and TPH-mo by USEPA Method 8015B.

Data Management The EC will obtain analytical data directly from the laboratory and will perform a preliminary review of the chemical data and quality assurance/ quality control (QA/QC) data prior to making decisions in the field regarding over-excavation and backfilling. A final QA/QC review will be performed in the Removal Action Completion Report (RACR).

The EC will make decisions based on data that has undergone QA/QC and been compiled using 95% UCL software, as described below. The EC will present draft data at periodic data meetings, as requested, to the GGNRA and DTSC, and will consult with the GGNRA and DTSC regarding plans for over-excavation and backfilling of excavations and plans for modifying planned excavation extents if required based on the soil confirmation results.

95% UCL Data Analysis A statistical evaluation of the confirmation sampling results will be performed to assess whether detected concentrations are on average in exceedance of applicable screening criteria.

Representative soil concentrations are estimated by the 95% UCL of concentrations of lead and zinc detected in soil from the trail. ProUCL software version 5.2.00 (USEPA, 2022a) will be used to calculate the 95% UCL in accordance with USEPA statistical guidance (USEPA, 2022b; and 2022c).

Data sets for each analyte are input as columns of detected values for contaminants and whether each value is a detect or non-detect at the quantitation limit. Data can be evaluated for fit to normal, lognormal, or gamma distributions. If a minimum of eight samples with two distinct detects is not met, the UCL cannot be calculated because of inadequate information on data distribution, and estimates of summary statistics, such as mean and variance, are unreliable. Therefore, at least eight sample results will be used to calculate the 95% UCL.

The selection of the appropriate 95% UCL depends on the distributional assumption for the dataset, which is accomplished using the ProUCL software. ProUCL checks whether the data set should be assumed to be normally distributed and/or the data set should be assumed to follow a gamma distribution. Based on the results of this evaluation, an appropriate probability distribution is assumed for the data to be used in the calculation of the 95% UCL in the next step.

The Shapiro-Wilk W test is used to test the normality of the dataset at a 5% significance level (i.e., 95% confidence level), as described in the USEPA guidance document titled Data Quality Assessment: Statistical Methods for Practitioners (USEPA, 2006). The test is first applied to the dataset and if the dataset passes the normality test, the data is assumed to be normally distributed.

If the dataset does not pass the normality test, a gamma distribution goodness-of-fit test (at a 5% significance level) is then applied to the dataset, and if the dataset passes the gamma distribution goodness-of-fit test, the data is assumed to follow a gamma distribution. If the dataset does not pass the gamma test, a lognormal distribution goodness-of-fit test (at a 5% significance level) was then applied to the dataset, and if the dataset passed the lognormal distribution goodness-of-fit test, the data were assumed to follow a lognormal distribution. If the dataset fails all three tests, the data are assumed to be nonparametric. In all cases, visual inspection of the shape of histograms and normal probability plots are performed to confirm the distributional assumption.

For datasets without non-detect, if the data is determined to be normally distributed, the 95% UCL is calculated as follows (USEPA, 2022c):

𝑈𝑈𝑈𝑈𝑈𝑈 = 𝜇𝜇 + 𝑡𝑡1−𝛼𝛼,(𝑛𝑛−1)�𝜎𝜎𝑆𝑆𝑆𝑆2

where μ = sample mean t = the student t value at α significant level, with n-1 degree of freedom α = 0.05 (one-tailed) n = sample size 𝜎𝜎𝑆𝑆𝑆𝑆2 = sample standard deviation

Otherwise, if the data is determined to follow a gamma or lognormal distribution, or if nonparametric assumption was used, the 95% UCL is determined based on the recommendation of the ProUCL software, which considers sample size and data skewness and ensures adequate coverage of the 95% UCL (USEPA, 2015c). Depending on the sample statistics, the ProUCL software generally recommends one of the following methods:

• For gamma distribution, Approximate Gamma UCL or Adjusted Gamma UCL.

• For lognormal distribution, Chebyshev Theorem using the minimum variance unbiased estimator (MVUE) of the parameters for a lognormal distribution, or Land’s H-statistic.

• For a non-parametric assumption, Chebyshev Theorem using the sample arithmetic mean and standard deviation, or the Hall’s bootstrap method.

For datasets with non-detect(s), non-detect data may be censored at the laboratory reporting limit.

If the data is normally distributed and/or if the data are symmetric or approximately symmetric, the Kaplan-Meier (KM) (t) method (i.e., Kaplan-Meier estimates using the Student’s t-distribution cutoff value) is used to calculate the 95% UCL. The equation to compute UCL is the same as the one illustrated above, except that the sample mean and sample standard deviation substituted by KM estimates of mean and standard deviation.

If the data are assessed to follow a gamma or lognormal distribution, or if the data are assumed to be non-parametric with moderate and high skewness, one of the following methods, in general, is recommended by the ProUCL software for the calculation of UCL:

• UCL based upon KM estimates using the Chebyshev inequality.

• UCL based upon KM estimates using the bias-corrected accelerated (BCA) bootstrap method.

If a minimum of eight samples with two distinct detects are not met, the UCL will not be calculated because of inadequate information on data distribution, and estimates of summary statistics, such as mean and variance, are unreliable. If the recommended UCL is greater than the maximum detected value, an alternative UCL may be selected from the ProUCL report (instead of the recommendation) to better and realistically represent the mean concentration term. The detailed statistical steps of the various methods described above are documented in the ProUCL software technical guide (USEPA 2022c).

Over-excavation Confirmation soil sample analytical results will be used to calculate the 95% UCL, which will be compared to the screening level of 80 mg/kg and 23,000 mg/kg, as described in Section 1.3 to assess whether further excavation is necessary in accordance with the process described herein.

If the 95% UCL concentration of the confirmation samples exceed the screening levels, discrete confirmation sampling locations will be compared to the screening levels. Additional soil will be removed at the confirmation sampling locations where screening level(s) are exceeded in 3-inch lifts within the horizontal extent of the trail excavation area to the center-point of the trail, extending halfway laterally to the nearest adjacent confirmation sample (with results below screening criteria), in either direction. The GGNRA and DTSC will be consulted regarding over-excavation decisions.

Following over-excavation of any areas with soil COC concentrations exceeding applicable screening levels, additional confirmation samples will be collected from the over-excavation bottom in the same manner as was done for the initial confirmation samples, to confirm COCs have been removed, and the 95% UCL will be re-calculated with the new results.

Laboratory Quality Control Samples

The QA/QC program will evaluate laboratory data for soil samples using the following four types of quality control samples for soil samples: matrix spikes, duplicates, lab control samples, and blanks as described below:

1. Matrix spike analyses are used to evaluate the accuracy of laboratory analyses for site-specific matrices. Surrogate spike analyses are intended to evaluate sample-specific extraction efficiency and accuracy for analyses performed on a gas chromatograph. Matrix spike and matrix spike duplicate (MS/MSD) samples are prepared by spiking the sample with a known amount of a target analyte. Once the spike is added to the MS/MSD sample, the sample is carried through the complete sample preparation process along with the other samples in the batch. Performance of the analytical method will be assessed for accuracy by evaluating percent recoveries of the spiked compounds. Percent recoveries will be assessed against established lab- and compound-specific data control limits.

2. Duplicates: Matrix spike duplicate and laboratory duplicate analyses are intended to evaluate the precision of laboratory analyses of site-specific matrices.

Laboratory control sample duplicates are intended to monitor analytical precision whenever there is insufficient sample available for matrix spiking. In all cases, performance of the analytical method will be assessed for precision by evaluating the relative percent difference (RPD) between duplicates. RPDs will be assessed against established lab-specific data control limits.

3. Laboratory Control Samples: Laboratory control samples (LCS) are intended to evaluate the performance of the analytical system without any potential matrix interferences. If sample matrix effects produce out-of-control matrix spike or matrix spike duplicate results, then the lab control sample recoveries are used to validate the analytical batch. In this case, performance of the analytical method will be assessed for accuracy by evaluating percent recoveries of the lab control sample compounds. Percent recoveries will be assessed against established lab- and compound- specific data control limits.

4. Blanks: Blanks are intended to evaluate the potential for external contamination of samples due to laboratory or field procedures.

Field Quality Control Samples

The following sections describe the field quality control samples to be collected.

Blank Samples

Blanks samples will be collected during soil sampling from equipment rinsate water to check for possible cross-contamination during sample collection, and from laboratory-provided blank water to check for possible cross-contamination during sampling and shipment to the laboratory.

Equipment blanks, and trip blanks, will be prepared and analyzed to determine the data quality provided by the sampling and analysis activities.

Equipment Blank Samples

Equipment blanks will be collected when sampling equipment (e.g., hand auger, trowel, slide hammer) is decontaminated and reused in the field. Laboratory provided “blank” water (e.g., deionized water) will be used to rinse the sampling equipment after the equipment has been decontaminated and then this water will be collected in the proper sample containers.

Trip Blank Samples

Trip blanks are used to assess the potential for contamination during sample storage and shipment.

The trip blank consists of laboratory provided blank water and will be provided with the sample containers to be used when sampling for volatile organic compounds (VOCs). Trip blanks will remain inside the coolers and will be included along with each shipment cooler containing project samples to be analyzed for VOCs.

Trip blanks analyzed for VOCs will only be collected in association with samples for which VOCs are part of the analytical suite (e.g., import fill analysis) with the following exception: QA/QC of VOC analysis will not be conducted for waste characterization sampling (i.e., water and soil), as is common practice.

Laboratory QA/QC Check

Laboratory QC samples will be analyzed at each laboratory for all samples analyzed.

Laboratory quality control checks will be performed by the laboratory in adherence to method-specific laboratory QC procedures. The QC procedures listed in Chapter 1 of SW-846 (USEPA, 1998), will be followed for each laboratory method for chemical analysis of soil samples.

Laboratory QC procedures include the following:

1. One internal method blank will be analyzed for every 20 samples analyzed or one per batch for each method, whichever is more frequent.

2. One MS/MSD will be analyzed for every 20 samples analyzed or one per batch for each method, whichever is more frequent. The MS/MSD will be performed using standard spike compounds on a sample from the Site for each method specified under SW-846.

3. One LCS will be analyzed for every 20 samples analyzed or one per analytical batch for each method, whichever is more frequent.

4. All sample analyses will be performed within the holding time specified for each individual analysis. Holding times for analyses are presented in Table 3 of the

IWP.

Data Evaluation

Data quality will be measured and evaluated in terms of sensitivity, precision, accuracy, representativeness, completeness, and comparability parameters. A discussion of these measurement parameters and how they will be used to evaluate the project analytical data follows.

Sensitivity

Sensitivity is the lowest detection limit of the method or instruments for each of the measurement parameters of interest. Essentially, it is the capability of a method or instrument to discriminate between measurement responses representing different levels of the variable of interest. All field and analytical activities will follow well-established methods. Reporting limits for each analysis are presented in Table 4 of the IWP. If the accepted method does not provide the sensitivity required for the project, alternative methods will be considered and presented to the DTSC.

Precision

Precision is the degree of agreement among repeated measurements of the same characteristic on the same sample or on separate samples collected as close as possible in time and place. It tells you how consistent and reproducible your field or laboratory methods are by showing you how close your measurements are to each other. It does not mean that the sample results reflect the "true" value, but rather that the sampling and analysis are giving consistent results under similar conditions.

Precision will be determined using field duplicates, matrix spike/matrix spike duplicates and duplicate quality control samples. The RPD between the two results will be calculated and used as an indication of the precision of the analyses performed. The following formula should be used to calculate precision:

𝑅𝑅𝑅𝑅𝑅𝑅 =

(𝑈𝑈1 − 𝑈𝑈2)

�(𝑈𝑈1 + 𝑈𝑈2)

2 �

∗ 100

Where: C1 = larger of the two observed values

C2 = smaller of the two observed values

It should be noted that duplicate analysis will not be performed on soil samples as the inherent nature of soil is heterogeneous.

Accuracy

Accuracy is a measure of confidence in a measurement. The smaller the difference between the measurement of a parameter and its "true" or expected value, the more accurate the measurement. The more precise or reproducible the result, the more reliable or accurate the result.

Accuracy will be assessed through the analysis of quality control samples. This includes analysis of method blanks, surrogates percent recovery, initial and continuing calibration criteria, including percent relative standard deviations, percent difference, and relative response factors. The analytical accuracy will be expressed as the percent recovery (%R) of an analyte which has been added to the environmental sample at a known concentration before analysis and is calculated according to the following equation.

%𝑅𝑅 =

(𝑆𝑆 − 𝑈𝑈)

𝑈𝑈𝑆𝑆𝑆𝑆

∗ 100

Where: S = measured concentration in spiked aliquot

U = measured concentration in unspiked aliquot

Csa = actual concentration of spike added

Representativeness

Representativeness is the extent to which measurements depict the true environmental condition or population you are evaluating. The representativeness of the data is largely addressed through the sampling design, and the proper collection and handling of samples and use of established field and laboratory procedures. The sampling design is based on the previous sampling data and proposed areas of disturbance on the trail and involves the sampling location selection (targeted sampling) and collecting sufficient sample population.

Completeness

Completeness is defined as the measure of the amount of valid data obtained from a measurement system compared to the amount that was expected to be obtained under normal conditions. Data completeness will be expressed as the percentage of valid data obtained from the measurement system. For data to be considered valid, it must meet all the acceptable criteria including accuracy and precision, as well as any other criteria required by the prescribed analytical method. Deficiencies in the data can include sampling techniques, inadequate accuracy, precision, or laboratory error.

Comparability

Comparability is a qualitative parameter expressing the confidence with which one data set can be compared with another. Sample data should be comparable with other measurements for similar samples and sample conditions. The objective for the QA/QC program is to produce data with the greatest possible degree of comparability. The number of matrices that are sampled and the range of field conditions encountered are considered in determining comparability.

Comparability is achieved by using standard methods for sampling and analysis, reporting data in standard units, normalizing results to standard conditions, and using standard and comprehensive reporting formats from one sampling event to the next.

Corrective Actions

If a batch of data does not meet the accuracy or precision goals described in Section 3, then an evaluation and explanation will be sought from the laboratory. Qualitative criteria to be considered include the following:

1. Comparison with historical data;

2. Comparison with regional data trends;

3. Evaluation of recent Site activities that could have a possible influence on data;

4. Review of sampling procedures; and

5. Review of other data obtained from samples collected on the same date.

If no reasonable explanation can be established that would validate the represented data and allow use of the data for the project, then the following corrective action(s) may be used:

1. Have the laboratory check sample documentation, calculations, and transcription steps for errors.

2. If possible, repeat the measurement; for example, re-extract and re-analyze.

3. Check instrument calibration and repeat measurement if possible.

4. Check adjustments for ambient conditions such as temperature.

5. Check presence of laboratory background contaminants, such as zinc or methylene chloride.

6. Replace or repair measuring device as necessary.

7. Resample if possible.

Corrective actions will be handled by the contract laboratory on a case-by-case basis with specific actions communicated to the EC QA/QC Officer as a written corrective action memorandum, where appropriate.

Loading, Off-Haul, and Disposal

Following characterization, soil will be loaded, managed, sampled, and disposed of in accordance with the requirements below.

All wastes will be transported and disposed of in accordance with applicable laws and regulations. All generated wastes will be disposed of at facilities that have been selected in advance by GGNRA.