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Environmental Assessment & Due Diligence
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Pre-Existing Contamination Assessment and Allocation of Responsibility

Northgate provided an opinion regarding pre-lease and existing environmental contamination and the allocation of environmental responsibility between our client (the land owner) and their tenant. Northgate's client and the tenant needed to identify pre-existing contamination to determine the extent of contamination released or otherwise generated at the site as a result of the tenant's use and occupancy, and to come to agreement on compliance goals if and when the tenant vacates the property. Northgate's opinion on pre-existing contamination was based on a thorough review of historical fill import records, aerial photographs, site investigation reports, soil and groundwater data, regulatory audits and reports, and other available documents. Compliance goals were established through diligent statistical analysis of background concentrations, evaluation of current and likely future regulatory screening levels, identification of risk pathways and receptors, and understanding of our client's risk management plans and sensitivities.

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MarketCenter Railyard Redevelopment

San Jose

Northgate performed rapid site assessment, site characterization studies, and remediation services during the redevelopment of a 40-acre former railyard in San Jose, California. The property was redeveloped as San Jose MarketCenter, a mixed-use shopping center. Northgate prepared a complete evaluation of options and associated costs for excavation and treatment or disposal of impacted soil. Northgate subsequently prepared a Risk Management Plan for the site with the ultimate goal of maximizing reuse of soil and minimizing offsite disposal. A sophisticated soil segregation and re-allocation technique enabled the successful reuse of a significant portion of site soils, thereby minimizing disposal volume, costs, and trucking impacts. Engineered caps and passive vapor mitigation systems were also incorporated into the construction design. Northgate developed an Operation and Maintenance Manual that currently serves as a guidance document for MarketCenter employees and tenants. Northgate successfully negotiated site closure and obtained a finding of No Further Action (NFA) for the site. In addition, the use of a risk-based mitigation program and integration of remediation with development ultimately reduced cleanup costs by over $30M.

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As-Needed Environmental Services

Santa Clara Valley Transportation Authority

Under contract with the Santa Clara Valley Transportation Authority (VTA), Northgate performs environmental investigations, serves as a regulatory liaison, provides construction monitoring and reporting services, and conducts remediation cost estimating in support of the BART extension from Fremont to San Jose. Northgate has completed Phase I and II Environmental Site Assessments (ESAs) conforming to ASTM standards on over 25 individual properties. The ESAs are used by the VTA to negotiate purchase prices for the properties that the VTA will acquire or lease as part of the extension and to prepare contingency plans for managing contaminated materials during construction. Individual projects have included extensive testing and analysis for lead and arsenic in shallow soil along existing rail line rights-of-way, evaluating onsite and offsite soil reuse and disposal options, and preparing engineering estimates of contaminated soil volumes based on historic investigations and documents. Other work has included soil quality testing for evaluation of potential contamination exposure to construction workers at the VTA bus maintenance facilities, evaluation of underground storage tank (UST) releases, and sediment and floodplain analysis.

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As-Needed Environmental Services

City of Oakland

Northgate provides the City of Oakland with environmental services under an as-needed contract. Northgate has provided a wide range of services under this contract, including environmental investigations in support of Brownfields redevelopment, storm water management and modeling, water quality planning and analysis, and energy efficiency consulting. Northgate also performs site surveys, environmental site assessments, restoration site prioritizing and planning, and design development services for waterway restoration.

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Former Almaden Air Force Station Redevelopment

Mt. Umunhum Open Space and Park

The Former Almaden Air Force Station, purchased from the Department of Defense in the 1980s, is currently undergoing environmental investigation and cleanup of contaminants in preparation of its transition to publically-accessible open space and park land. Located within the Sierra Azul Open Space Preserve, Mt. Umunhum is a prominent Bay Area landmark, and is envisioned to be a significant recreational destination. Northgate oversaw a series of engineering and hazardous materials studies to support the Midpeninsula Regional Open Space District's planning efforts and CEQA/NEPA requirements. Studies included hazardous materials surveys of several abandoned buildings, a structural survey of the five-story Radar Tower, a slope stability investigation at the Radar Tower site, a cultural and historical assessment survey of the former Air Force Station, and soil sampling and analysis to assess environmental contamination. Northgate reviewed the investigation and cleanup work being completed by the US Army Corps of Engineers and represented the District's interests in communications with the Corps and state regulatory agencies. Northgate also assisted the District with engineering studies including structural analysis, rock slope stability analysis, serpentinite geologic mapping, hazardous materials studies, and soil characterization for lead, asbestos, and pesticides. We leveraged our experience with environmental issues on lands being converted from military or industrial uses to parks and ecological preserves to support the District in its mission to acquire and manage land for wildlife habitat and to provide safe and educational public access to these lands.

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Hazardous Substance Liability Assessments

Santa Clara Valley Water District

Northgate has performed multiple Hazardous Substance Liability Assessments (HSLAs) for the Santa Clara Valley Water District. The purpose of a HSLA is to reasonably evaluate the potential for, or the actual impact of, past practices on a given property. The services provided by Northgate include reviewing readily available information regarding the site history, reviewing chain-of-title documents, reconnaissance of the site and vicinity, reviewing regulatory agency publications and files, and evaluating the Recognized Environmental Conditions. The HSLAs are used by the Santa Clara Valley Water District to evaluate sites for possible acquisition as part of its flood control projects.

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Environmental Investigation & Characterization
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Emergent Chemical Investigation and Expert Witness Services

Northgate performed an investigation and provided expert testimony regarding the distribution and sources of hexavalent chromium and the emergent chemicals 1,4 dioxane and n nitrosodimethylamine (NDMA) and other inorganic and organic contaminants in soil and groundwater. The project site was a former printed circuit board manufacturing facility for the aerospace industry, and was previously used for automotive manufacturing. Northgate conducted a thorough review of historical data and facility plans, reviewed records of printed circuit manufacturing operations at the Site, and collected soil and groundwater samples. Historical plans of the manufacturing facilities and aerial photographs were used to correlate locations of impacted soil and groundwater with historical features and operations. These investigations confirmed that the historical printed circuit manufacturing operations were the most likely source of the subsurface contamination.

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Future Hospital Site Brownfields Redevelopment

Working within the framework of an Environmental Agreement with the prior and future property owners and a Prospective Purchaser Agreement with the San Francisco Bay Regional Water Quality Control Board, Northgate led the investigation, demolition, and remediation of an 18-acre former electronics research and manufacturing facility. The property was impacted with organic solvents, heavy metals, and petroleum hydrocarbons. Northgate provided oversight for the hazardous materials closure of the former manufacturing facilities, including the RCRA-permitted wastewater treatment plant and chemical storage areas. Demolition work included the removal of all underground utilities and abatement of more than 200 tons of asbestos-containing material and lead-based paint from four buildings encompassing 330,000 square feet. Stringent oversight and segregation practices resulted in approximately 99% of the building demolition debris being recycled. Northgate also prepared the Remedial Action Plan for the property, and conducted the cleanup of contaminated soil gas, soil, and groundwater. Northgate was able to segregate and reuse 80% of the 100,000 cubic yards of affected material at the site as a result of detailed characterization and onsite treatment processes. Northgate successfully remediated the site to unrestricted use standards, facilitating the property's redevelopment as a hospital and medical center.

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As-Needed Environmental Services

Santa Clara Valley Transportation Authority

Under contract with the Santa Clara Valley Transportation Authority (VTA), Northgate performs environmental investigations, serves as a regulatory liaison, provides construction monitoring and reporting services, and conducts remediation cost estimating in support of the BART extension from Fremont to San Jose. Northgate has completed Phase I and II Environmental Site Assessments (ESAs) conforming to ASTM standards on over 25 individual properties. The ESAs are used by the VTA to negotiate purchase prices for the properties that the VTA will acquire or lease as part of the extension and to prepare contingency plans for managing contaminated materials during construction. Individual projects have included extensive testing and analysis for lead and arsenic in shallow soil along existing rail line rights-of-way, evaluating onsite and offsite soil reuse and disposal options, and preparing engineering estimates of contaminated soil volumes based on historic investigations and documents. Other work has included soil quality testing for evaluation of potential contamination exposure to construction workers at the VTA bus maintenance facilities, evaluation of underground storage tank (UST) releases, and sediment and floodplain analysis.

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Upper Guadalupe River Environmental Remedial Action Plan

Santa Clara Valley Water District

This three-acre property was acquired by the Santa Clara Valley Water District to construct a flood control ch...

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Upper Guadalupe River Environmental Remedial Action Plan

Santa Clara Valley Water District

This three-acre property was acquired by the Santa Clara Valley Water District to construct a flood control channel for the Guadalupe River. On behalf of the District, Northgate identified and confirmed the appropriate lead regulatory agency for the site, and facilitated enrollment in a Voluntary Cleanup Program. Northgate also prepared a Site Investigation Summary Report, researching and synthesizing historical soil and groundwater analytical results, and a Risk Analysis and Assessment Report, evaluating the risk to human health from residual soil and groundwater contamination. Additional evaluations and reports to be completed include a Remedial Action Plan, Plans and Specifications for remedial actions, and a Remedial Construction Completion Report.

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Wetlands Restoration

Yosemite Slough, Candlestick Point

The Yosemite Slough wetland restoration is the centerpiece of a long-term project to clean up contamination, restore tidal wetlands on filled lands, and improve habitat quality of associated transitional and upland areas on Candlestick Point in San Francisco. The restoration design provides public shoreline access, wetlands and wildlife habitat, bird nesting islands, transitional and upland buffer areas for sensitive habitats, interpretive trails, and an education center. Northgate conducted a remedial investigation and feasibility study, mapped the distribution of contamination using soil sampling combined with a geographic information system (GIS), and developed an environmental model. Detailed data visualizations facilitated negotiation of risk-based cleanup levels with the San Francisco Bay Regional Water Quality Control Board. The remedial strategy relies on detailed characterization and excavation of over 230,000 cubic yards of fill, and careful segregation, management, and reuse of onsite soil to reduce chemical concentrations in wetland cover soils to near-ambient sediment concentrations. While most of the soil met action goals, the soil associated with an underground storage tank and former metals fabrication facility exceeded the action goals for total lead for onsite reuse. Northgate stabilized this stream with onsite treatment to reduce lead solubility to below toxicity characteristic leaching procedure (TCLP) levels, tested the soil to confirm waste characterization, and disposed of the material offsite at a licensed landfill. Northgate also provided geotechnical engineering analysis, developed bid specifications for contractor selection, provided construction compliance monitoring, and participated in public outreach activities.

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Environmental Sampling and Analysis

City of San Francisco Playfields Initiative

In 2006, the City of San Francisco Recreation and Parks Department and the City Fields Foundation established the Playfields Initiative, a public-private partnership to renovate underused and neglected athletic fields with synthetic turf playfields and light installations. However, concerns from community action groups about potential environmental and health impacts from synthetic turf delayed the installation of some of these much-needed field renovations. Northgate worked with the Playfields Initiative to develop acquisition standards and a thorough testing and monitoring program to ensure that any synthetic turf fields installed by the Playfields Initiative do not contain heavy metals or are a threat to groundwater quality. Northgate also conducted seasonal first-flush stormwater sampling of multiple fields. The results of Northgate's efforts helped to alleviate community concerns and got the renovation projects back on track.

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Environmental Remediation & Engineering
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Elmhurst Creek Sediment Removal and Bridge Replacement

Northgate provides environmental, permitting, and geotechnical services on this project, which involves the excavation of contaminated sediment from a segment of Elmhurst Creek in East Oakland. The project also includes the replacement of a culvert and bridge. Northgate evaluated existing environmental conditions, assessed sediment quality, and conducted a geotechnical investigation for the bridge foundations. Northgate prepared a Joint Aquatic Resources Permit Application (JARPA) application for the work, coordinated agency responses to comments, and worked with the client, land owners, attorneys, consultants, and agencies to resolve project issues. The Northgate team is also preparing all CEQA documentation related to the project. The agencies participating in the project include the City of Oakland, U.S. Army Corps of Engineers, California Department of Fish and Game, and the San Francisco Bay Regional Water Quality Control Board.

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Investigation and Remediation

Former Braito Landfill, Benicia, California

Northgate performed comprehensive assessment and remediation of an approximate 60-acre residential development that had been partially constructed over a former landfill. Northgate's work, which began when refuse surfaced in residential backyards, included complete evaluation of historic land use, including review of facility operating records, development and implementation of a detailed characterization plan, evaluation of human health and environmental health risks, and implementation of site cleanup. Northgate prepared excavation, shoring, and underpinning plans, as well as remediation monitoring and contingency plans to ensure safety of nearby residents. Northgate performed soil gas extraction and treatment, in-situ stabilization of buried wastes, storm water management, and offsite transportation and disposal of hazardous and non-hazardous wastes. Northgate saved our client over $2M in disposal costs by using an innovative statistical analysis to establish that the majority of the waste could be classified as non-hazardous, and treating hazardous wastes to become non-hazardous. Northgate also developed and implemented public participation programs, and participated in Community Advisory Group meetings, workshops, and various agency meetings. Northgate negotiated final cleanup levels, and worked with our client's attorneys to prepare final documents, disclosures, and deed restrictions for the site following remediation. Northgate received a special recognition award from the City of Benicia following successful completion of the project.

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Environmental and Geotechnical Engineering Services

Mission Bay Loop Light Rail Extension

Construction of the Mission Bay Loop Extension of the Third Street Light Rail is subject to the Maher Ordinanc...

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Environmental and Geotechnical Engineering Services

Mission Bay Loop Light Rail Extension

Construction of the Mission Bay Loop Extension of the Third Street Light Rail is subject to the Maher Ordinance of the San Francisco Health Code, which governs construction in areas of known historical landfill. Northgate prepared an Environmental Site History Report and Soil Sampling Work Plan, which were approved by the San Francisco Department of Public Health. We reviewed site history, performed site reconnaissance, conducted reviews with regulatory agencies, developed a soil sampling program to characterize the soil to be excavated, and prepared the Maher Ordinance Application for the San Francisco Department of Public Works. Northgate also performed concurrent geotechnical and environmental investigations to identify hazardous chemicals in soil and determine potential environmental or human health and safety risks during construction. When chemical concentrations exceeded regulatory screening levels, Northgate prepared a Site Mitigation Plan describing construction management procedures to mitigate worker and public exposure during construction and recommending waste management and disposal options for construction-generated soils.

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Soil Remediation, Former Oakland Army Base

Oakland Base Reuse Authority

Northgate prepared support plans and provided construction monitoring, sampling services, and waste characterization for soil remediation at the former Oakland Army Base. The project site was a former oil reclamation plant for the military base, and used an acid-clay refining process that generated acidic sludge and spent clay contaminated with petroleum residuals and metals. The remedial action plan, approved by the California Department of Toxic Substances Control (DTSC), consisted of excavation and onsite treatment of the acidic organic residue to reduce the mobility of lead and other underlying hazardous constituents, and to minimize the amount of material that must be treated and disposed offsite. Northgate prepared support plans for the excavation (involving soil treatment, transportation, health and safety, stockpile management, decontamination, and storm water pollution prevention), performed noise monitoring, provided oversight of stockpile management, and conducted sample collection, analysis, and validation. The DTSC certified completion of the remedial actions in 2009.

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Wetlands Restoration and Corrective Action Plan

Sears Point

The Sears Point Wetland Restoration Project encompasses more than 2,300 acres of agricultural land owned by the Sonoma Land Trust (SLT), which is restoring the area to tidal wetlands. The former shooting range contains sediments contaminated with lead and polycyclic aromatic hydrocarbons. Northgate defined contaminant distribution and quantified residual lead concentrations in surface and shallow soil and groundwater. We used characterization data to evaluate potential impacts to wetland flora and fauna and to develop cleanup criteria for ecological protection. Northgate developed and evaluated remedial alternatives consistent with the future wetlands scenario, working closely with wetlands scientists, stakeholders, and the San Francisco Bay Regional Water Quality Control Board. We prepared a Corrective Action Plan, approved by the Water Board, which specifies removing contaminated material from the sensitive area and using it as borrow material in upland perimeter levees. This cost-effective solution provides material for levee construction, removes contaminated material from sensitive habitats, and lowers the site elevation to suitable levels for tidal wetlands development.

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Upper Guadalupe River Environmental Remedial Action Plan

Santa Clara Valley Water District

This three-acre property was acquired by the Santa Clara Valley Water District to construct a flood control ch...

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Upper Guadalupe River Environmental Remedial Action Plan

Santa Clara Valley Water District

This three-acre property was acquired by the Santa Clara Valley Water District to construct a flood control channel for the Guadalupe River. On behalf of the District, Northgate identified and confirmed the appropriate lead regulatory agency for the site, and facilitated enrollment in a Voluntary Cleanup Program. Northgate also prepared a Site Investigation Summary Report, researching and synthesizing historical soil and groundwater analytical results, and a Risk Analysis and Assessment Report, evaluating the risk to human health from residual soil and groundwater contamination. Additional evaluations and reports to be completed include a Remedial Action Plan, Plans and Specifications for remedial actions, and a Remedial Construction Completion Report.

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Water Resource Assessment
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Emergent Chemical Investigation and Expert Witness Services

Northgate performed an investigation and provided expert testimony regarding the distribution and sources of hexavalent chromium and the emergent chemicals 1,4 dioxane and n nitrosodimethylamine (NDMA) and other inorganic and organic contaminants in soil and groundwater. The project site was a former printed circuit board manufacturing facility for the aerospace industry, and was previously used for automotive manufacturing. Northgate conducted a thorough review of historical data and facility plans, reviewed records of printed circuit manufacturing operations at the Site, and collected soil and groundwater samples. Historical plans of the manufacturing facilities and aerial photographs were used to correlate locations of impacted soil and groundwater with historical features and operations. These investigations confirmed that the historical printed circuit manufacturing operations were the most likely source of the subsurface contamination.

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Hard Rock Quarry Water Resources Assessment

Northgate performed a water resources assessment in support of the proposed expansion of a hard rock quarry. The quarry property overlies a complex fractured rock aquifer along a river and between three large fault zones. The river's close proximity to the quarry makes understanding surface water-groundwater interaction of critical importance. Naturally occurring levels of salts, metals, and other chemicals in local groundwater exceeding certain regulatory standards were also of concern. Northgate's primary objectives were to characterize groundwater seepage conduits that may intercept the pit, quantify seepage originating from the river and other recharge areas by developing a 3D MODFLOW groundwater model, and to test alternative grading and dewatering plans. Northgate also provided hydrogeologic assessment, geophysical surveying, pollution analysis, and data management and interpretation using 3D geographic information system (GIS) visualization.

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As-Needed Environmental Services

City of Oakland

Northgate provides the City of Oakland with environmental services under an as-needed contract. Northgate has provided a wide range of services under this contract, including environmental investigations in support of Brownfields redevelopment, storm water management and modeling, water quality planning and analysis, and energy efficiency consulting. Northgate also performs site surveys, environmental site assessments, restoration site prioritizing and planning, and design development services for waterway restoration.

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Investigation and Remedial Planning

Driscoll Ranch

Driscoll Ranch is a key landholding of the Midpeninsula Regional Open Space District, whose planned expansion of the adjacent La Honda Creek Open Space Preserve includes the 3,600-acre Driscoll Ranch, creating one of the largest regional ecological preserves on the San Mateo County coastline. Northgate helped the District develop and implement a strategic plan to add Driscoll Ranch to the preserve, and provided remedial planning and a detailed site investigation for contamination related to historical uses, including oil drilling and cattle ranching. Northgate developed site-specific cleanup levels for soil contaminated with petroleum hydrocarbons, polycyclic aromatic hydrocarbons, and pesticides, and developed a Site Management Plan to permit safe public access to the ecological preserve. We concluded that environmental conditions would not pose a risk to groundwater, surface water, or the health of visitors at the future ecological preserve, and that residual impacts be managed in-place through administrative mechanisms, avoiding costly remedial measures and expediting property access. The San Francisco Bay Regional Water Quality Control Board approved the Soil Management Plan and issued a "No Further Action" letter.

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Hard Rock Quarry Water Resources Assessment

Northgate performed a water resources assessment in support of the proposed expansion of a hard rock quarry. The quarry property overlies a complex fractured rock aquifer along a river and between three large fault zones. The river's close proximity to the quarry makes understanding surface water-groundwater interaction of critical importance. Naturally occurring levels of salts, metals, and other chemicals in local groundwater exceeding certain regulatory standards were also of concern. Northgate's primary objectives were to characterize groundwater seepage conduits that may intercept the pit, quantify seepage originating from the river and other recharge areas by developing a 3D MODFLOW groundwater model, and to test alternative grading and dewatering plans. Northgate also provided hydrogeologic assessment, geophysical surveying, pollution analysis, and data management and interpretation using 3D geographic information system (GIS) visualization.

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Hazardous Materials & Waste Management
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Environmental Assessment and Remediation,

Santana Row, San Jose, California

Northgate was the lead technical manager for a 50-acre Brownfields redevelopment site in San Jose, California, remediated under a Voluntary Cleanup Agreement and a Prospective Purchaser Agreement negotiated with the California Department of Toxic Substances Control (DTSC). The site, which originally consisted of orchards and other agricultural land, was first developed as a shopping center and automobile dealership during the early 1960s. As part of site redevelopment, the existing center was completely demolished and replaced with a unique, mixed residential/commercial development. During demolition and redevelopment, removal actions were implemented to protect human health and the environment by minimizing exposure to soils containing pesticides, lead, and arsenic. Cleanup goals were developed based on a risk assessment and an evaluation of naturally-occurring background levels of metals. Affected soils were identified, isolated, and encapsulated in proposed commercial development areas, with clean soils relocated to residential development areas of the site. More than 100,000 cubic yards of soil were removed from the site as clean fill. The removal action work required extensive coordination with the project construction manager, site grading and utility contractors, regulatory agencies, and the public. Northgate also provided third-party oversight of the cleanup and closure of the former automobile dealership, including a review of building decontamination and demolition, removal of aboveground storage tanks, removal of underground oil/water separators and associated drain lines, and removal of a previously unknown underground waste oil tank. Northgate also negotiated cost-sharing arrangements for facility cleanup and closure on the owner's behalf. Barbara Cook of the DTSC presented this site as a case study demonstrating success of the agency's Brownfield development program. Northgate continues to provide long term monitoring and compliance services for this project.

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Black Mountain Industrial Complex Investigation and Soil Remediation

Northgate completed several soil, groundwater, and indoor air investigations at a 450-acre industrial facility within the Black Mountain Industrial Complex in Henderson, Nevada. This active industrial facility was the world's largest magnesium production plant during World War II and was later used for a variety of other manufacturing activities, resulting in extensive soil and groundwater impacts from heavy metals, perchlorate, pesticides, chlorinated solvents, radionuclides, and other chemicals. Northgate rapidly mobilized and managed a team of staff and subcontractors to remove approximately 800,000 cubic yards of soil from the site under an accelerated schedule. Northgate also performed comprehensive environmental and health risk assessments related to groundwater-to-surface water impacts, plume capture and control, vapor intrusion, potential leaching of residual chemicals from soil to groundwater, and vadose-zone remedial alternatives. As part of our comprehensive analyses, Northgate developed and calibrated a regional three-dimensional groundwater model with an areal extent of over 10,000 acres, which was centered on the 450-acre industrial facility and encompassed the remediation systems of multiple responsible parties and outflow to the Las Vegas Wash, a tributary to Lake Mead. The model, developed using MODFLOW, is a valuable and efficient tool for evaluating plume capture from three groundwater extraction systems, optimizing our client's existing system to enhance capture and reduce operations/maintenance costs, and making recommendations for future remedial enhancements.

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Environmental and Geotechnical Engineering Services

Mission Bay Loop Light Rail Extension

Construction of the Mission Bay Loop Extension of the Third Street Light Rail is subject to the Maher Ordinanc...

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Environmental and Geotechnical Engineering Services

Mission Bay Loop Light Rail Extension

Construction of the Mission Bay Loop Extension of the Third Street Light Rail is subject to the Maher Ordinance of the San Francisco Health Code, which governs construction in areas of known historical landfill. Northgate prepared an Environmental Site History Report and Soil Sampling Work Plan, which were approved by the San Francisco Department of Public Health. We reviewed site history, performed site reconnaissance, conducted reviews with regulatory agencies, developed a soil sampling program to characterize the soil to be excavated, and prepared the Maher Ordinance Application for the San Francisco Department of Public Works. Northgate also performed concurrent geotechnical and environmental investigations to identify hazardous chemicals in soil and determine potential environmental or human health and safety risks during construction. When chemical concentrations exceeded regulatory screening levels, Northgate prepared a Site Mitigation Plan describing construction management procedures to mitigate worker and public exposure during construction and recommending waste management and disposal options for construction-generated soils.

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Environmental Site Assessments and Groundwater Monitoring

City of Palo Alto, California

Northgate prepared Phase I and Phase II Environmental Site Assessments to ensure that several properties owned...

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Environmental Site Assessments and Groundwater Monitoring

City of Palo Alto, California

Northgate prepared Phase I and Phase II Environmental Site Assessments to ensure that several properties owned by the City of Palo Alto did not pose a threat to public health or the environment during or after redevelopment. Northgate helped the City negotiate agreements that included compensation to remediate known environmental conditions. Properties included the Palo Alto Municipal Airport, which was leased by the City to Santa Clara County, and Palo Alto Sanitation Company (PASCO) Maintenance Yard. Phase I assessments identified recognized environmental conditions and issues of concern requiring investigation of these sites to establish baseline conditions prior to lease termination and reuse. Northgate performed comprehensive Phase II soil and groundwater quality investigations in accordance with regulatory requirements including ASTM E-1527-05, 40 CFR Part 312, and ASTM E-1903-97. Northgate also performed subsequent groundwater monitoring at the properties.

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Wetlands Restoration

Yosemite Slough, Candlestick Point

The Yosemite Slough wetland restoration is the centerpiece of a long-term project to clean up contamination, restore tidal wetlands on filled lands, and improve habitat quality of associated transitional and upland areas on Candlestick Point in San Francisco. The restoration design provides public shoreline access, wetlands and wildlife habitat, bird nesting islands, transitional and upland buffer areas for sensitive habitats, interpretive trails, and an education center. Northgate conducted a remedial investigation and feasibility study, mapped the distribution of contamination using soil sampling combined with a geographic information system (GIS), and developed an environmental model. Detailed data visualizations facilitated negotiation of risk-based cleanup levels with the San Francisco Bay Regional Water Quality Control Board. The remedial strategy relies on detailed characterization and excavation of over 230,000 cubic yards of fill, and careful segregation, management, and reuse of onsite soil to reduce chemical concentrations in wetland cover soils to near-ambient sediment concentrations. While most of the soil met action goals, the soil associated with an underground storage tank and former metals fabrication facility exceeded the action goals for total lead for onsite reuse. Northgate stabilized this stream with onsite treatment to reduce lead solubility to below toxicity characteristic leaching procedure (TCLP) levels, tested the soil to confirm waste characterization, and disposed of the material offsite at a licensed landfill. Northgate also provided geotechnical engineering analysis, developed bid specifications for contractor selection, provided construction compliance monitoring, and participated in public outreach activities.

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PCB Runoff Prevention Plan

Alameda County Clean Water Program

In 2010, the U.S. EPA approved a Total Maximum Daily Load (TMDL) for polychlorinated biphenyls (PCBs) in the San Francisco Bay. As part of the TMDL implementation, the Municipal Regional Storm Water Permit requires local municipalities to take steps to reduce controllable sources of PCBs that can migrate to the Bay. Northgate supported the Alameda County Clean Water Program in a pilot project designed to identify potential PCB sources in construction materials and implement best management practices (BMPs) to reduce PCBs in storm water runoff. At the client's request, Northgate evaluated the draft BMPs for completeness and effectiveness. Northgate developed materials to support the Model Implementation Process and participated in role-playing exercises with the client and with other stakeholders at the municipal and state level.

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Environmental Modeling & Data Visualization
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Emergent Chemical Investigation and Expert Witness Services

Northgate performed an investigation and provided expert testimony regarding the distribution and sources of hexavalent chromium and the emergent chemicals 1,4 dioxane and n nitrosodimethylamine (NDMA) and other inorganic and organic contaminants in soil and groundwater. The project site was a former printed circuit board manufacturing facility for the aerospace industry, and was previously used for automotive manufacturing. Northgate conducted a thorough review of historical data and facility plans, reviewed records of printed circuit manufacturing operations at the Site, and collected soil and groundwater samples. Historical plans of the manufacturing facilities and aerial photographs were used to correlate locations of impacted soil and groundwater with historical features and operations. These investigations confirmed that the historical printed circuit manufacturing operations were the most likely source of the subsurface contamination.

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Black Mountain Industrial Complex Investigation and Soil Remediation

Northgate completed several soil, groundwater, and indoor air investigations at a 450-acre industrial facility within the Black Mountain Industrial Complex in Henderson, Nevada. This active industrial facility was the world's largest magnesium production plant during World War II and was later used for a variety of other manufacturing activities, resulting in extensive soil and groundwater impacts from heavy metals, perchlorate, pesticides, chlorinated solvents, radionuclides, and other chemicals. Northgate rapidly mobilized and managed a team of staff and subcontractors to remove approximately 800,000 cubic yards of soil from the site under an accelerated schedule. Northgate also performed comprehensive environmental and health risk assessments related to groundwater-to-surface water impacts, plume capture and control, vapor intrusion, potential leaching of residual chemicals from soil to groundwater, and vadose-zone remedial alternatives. As part of our comprehensive analyses, Northgate developed and calibrated a regional three-dimensional groundwater model with an areal extent of over 10,000 acres, which was centered on the 450-acre industrial facility and encompassed the remediation systems of multiple responsible parties and outflow to the Las Vegas Wash, a tributary to Lake Mead. The model, developed using MODFLOW, is a valuable and efficient tool for evaluating plume capture from three groundwater extraction systems, optimizing our client's existing system to enhance capture and reduce operations/maintenance costs, and making recommendations for future remedial enhancements.

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Wetlands Restoration

Yosemite Slough, Candlestick Point

The Yosemite Slough wetland restoration is the centerpiece of a long-term project to clean up contamination, restore tidal wetlands on filled lands, and improve habitat quality of associated transitional and upland areas on Candlestick Point in San Francisco. The restoration design provides public shoreline access, wetlands and wildlife habitat, bird nesting islands, transitional and upland buffer areas for sensitive habitats, interpretive trails, and an education center. Northgate conducted a remedial investigation and feasibility study, mapped the distribution of contamination using soil sampling combined with a geographic information system (GIS), and developed an environmental model. Detailed data visualizations facilitated negotiation of risk-based cleanup levels with the San Francisco Bay Regional Water Quality Control Board. The remedial strategy relies on detailed characterization and excavation of over 230,000 cubic yards of fill, and careful segregation, management, and reuse of onsite soil to reduce chemical concentrations in wetland cover soils to near-ambient sediment concentrations. While most of the soil met action goals, the soil associated with an underground storage tank and former metals fabrication facility exceeded the action goals for total lead for onsite reuse. Northgate stabilized this stream with onsite treatment to reduce lead solubility to below toxicity characteristic leaching procedure (TCLP) levels, tested the soil to confirm waste characterization, and disposed of the material offsite at a licensed landfill. Northgate also provided geotechnical engineering analysis, developed bid specifications for contractor selection, provided construction compliance monitoring, and participated in public outreach activities.

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Wetlands Restoration

Yosemite Slough, Candlestick Point

The Yosemite Slough wetland restoration is the centerpiece of a long-term project to clean up contamination, restore tidal wetlands on filled lands, and improve habitat quality of associated transitional and upland areas on Candlestick Point in San Francisco. The restoration design provides public shoreline access, wetlands and wildlife habitat, bird nesting islands, transitional and upland buffer areas for sensitive habitats, interpretive trails, and an education center. Northgate conducted a remedial investigation and feasibility study, mapped the distribution of contamination using soil sampling combined with a geographic information system (GIS), and developed an environmental model. Detailed data visualizations facilitated negotiation of risk-based cleanup levels with the San Francisco Bay Regional Water Quality Control Board. The remedial strategy relies on detailed characterization and excavation of over 230,000 cubic yards of fill, and careful segregation, management, and reuse of onsite soil to reduce chemical concentrations in wetland cover soils to near-ambient sediment concentrations. While most of the soil met action goals, the soil associated with an underground storage tank and former metals fabrication facility exceeded the action goals for total lead for onsite reuse. Northgate stabilized this stream with onsite treatment to reduce lead solubility to below toxicity characteristic leaching procedure (TCLP) levels, tested the soil to confirm waste characterization, and disposed of the material offsite at a licensed landfill. Northgate also provided geotechnical engineering analysis, developed bid specifications for contractor selection, provided construction compliance monitoring, and participated in public outreach activities.

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Hard Rock Quarry Water Resources Assessment

Northgate performed a water resources assessment in support of the proposed expansion of a hard rock quarry. The quarry property overlies a complex fractured rock aquifer along a river and between three large fault zones. The river's close proximity to the quarry makes understanding surface water-groundwater interaction of critical importance. Naturally occurring levels of salts, metals, and other chemicals in local groundwater exceeding certain regulatory standards were also of concern. Northgate's primary objectives were to characterize groundwater seepage conduits that may intercept the pit, quantify seepage originating from the river and other recharge areas by developing a 3D MODFLOW groundwater model, and to test alternative grading and dewatering plans. Northgate also provided hydrogeologic assessment, geophysical surveying, pollution analysis, and data management and interpretation using 3D geographic information system (GIS) visualization.

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Expert Witness & Litigation Support
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Expert Witness and Litigation Support for Cost Recovery Lawsuit

Los Angeles, California

Northgate assisted a former land owner to negotiate a favorable settlement in this cost recovery lawsuit. A l...

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Expert Witness and Litigation Support for Cost Recovery Lawsuit

Los Angeles, California

Northgate assisted a former land owner to negotiate a favorable settlement in this cost recovery lawsuit. A local agency had taken our client's land and the neighboring properties by eminent domain, and planned a large-scale and costly excavation to remediate chemicals in soil, soil gas, and groundwater. Northgate performed a field investigation, data analyses, and review of historical information to substantially limit our client's liability for regional contamination issues. Northgate's analyses demonstrated that most of the contamination was attributed to other sources, including former underground storage tanks, other industrial operations, and naturally occurring oil and gas deposits. Northgate prepared a cost allocation strategy and represented our client in mediation. Our efforts substantially lowered our client's share of cleanup costs and achieved a favorable settlement, thereby avoiding a costly legal battle.

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Emergent Chemical Investigation and Expert Witness Services

Northgate performed an investigation and provided expert testimony regarding the distribution and sources of hexavalent chromium and the emergent chemicals 1,4 dioxane and n nitrosodimethylamine (NDMA) and other inorganic and organic contaminants in soil and groundwater. The project site was a former printed circuit board manufacturing facility for the aerospace industry, and was previously used for automotive manufacturing. Northgate conducted a thorough review of historical data and facility plans, reviewed records of printed circuit manufacturing operations at the Site, and collected soil and groundwater samples. Historical plans of the manufacturing facilities and aerial photographs were used to correlate locations of impacted soil and groundwater with historical features and operations. These investigations confirmed that the historical printed circuit manufacturing operations were the most likely source of the subsurface contamination.

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Pre-Existing Contamination Assessment and Allocation of Responsibility

Northgate provided an opinion regarding pre-lease and existing environmental contamination and the allocation of environmental responsibility between our client (the land owner) and their tenant. Northgate's client and the tenant needed to identify pre-existing contamination to determine the extent of contamination released or otherwise generated at the site as a result of the tenant's use and occupancy, and to come to agreement on compliance goals if and when the tenant vacates the property. Northgate's opinion on pre-existing contamination was based on a thorough review of historical fill import records, aerial photographs, site investigation reports, soil and groundwater data, regulatory audits and reports, and other available documents. Compliance goals were established through diligent statistical analysis of background concentrations, evaluation of current and likely future regulatory screening levels, identification of risk pathways and receptors, and understanding of our client's risk management plans and sensitivities.

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Expert Witness and Litigation Support for Cost Recovery Lawsuit

Los Angeles, California

Northgate assisted a former land owner to negotiate a favorable settlement in this cost recovery lawsuit. A l...

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Expert Witness and Litigation Support for Cost Recovery Lawsuit

Los Angeles, California

Northgate assisted a former land owner to negotiate a favorable settlement in this cost recovery lawsuit. A local agency had taken our client's land and the neighboring properties by eminent domain, and planned a large-scale and costly excavation to remediate chemicals in soil, soil gas, and groundwater. Northgate performed a field investigation, data analyses, and review of historical information to substantially limit our client's liability for regional contamination issues. Northgate's analyses demonstrated that most of the contamination was attributed to other sources, including former underground storage tanks, other industrial operations, and naturally occurring oil and gas deposits. Northgate prepared a cost allocation strategy and represented our client in mediation. Our efforts substantially lowered our client's share of cleanup costs and achieved a favorable settlement, thereby avoiding a costly legal battle.

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Elmhurst Creek Sediment Removal and Bridge Replacement

Northgate provides environmental, permitting, and geotechnical services on this project, which involves the excavation of contaminated sediment from a segment of Elmhurst Creek in East Oakland. The project also includes the replacement of a culvert and bridge. Northgate evaluated existing environmental conditions, assessed sediment quality, and conducted a geotechnical investigation for the bridge foundations. Northgate prepared a Joint Aquatic Resources Permit Application (JARPA) application for the work, coordinated agency responses to comments, and worked with the client, land owners, attorneys, consultants, and agencies to resolve project issues. The Northgate is also preparing all CEQA documentation related to the project. The agencies participating in the project include the City of Oakland, U.S. Army Corps of Engineers, California Department of Fish and Game, and the San Francisco Bay Regional Water Quality Control Board.

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Strategic Planning & Exit Strategies
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Environmental Impact Review

Former Paint Manufacturing Facility

Northgate provides environmental consulting services at a former paint manufacturing facility located in Los Angeles County. Previous investigations identified contaminants in soil vapor, dissolved in shallow groundwater, and as a layer of light non-aqueous phase liquid (LNAPL). Remedial actions to mitigate chemical impacts have been underway since 1987, initially through product removal by mechanical means, and subsequently with the installation of a soil vapor extraction (SVE) and bioventing system to remove product and stimulate biodegradation of residual source-zone contaminants. Northgate conducted a review of the remedial system and provided recommendations for immediate action to eliminate threats to underlying aquifers. Northgate is now working with the responsible party to reduce current and long-term operating costs by optimizing the existing SVE system and using a risk-based approach to evaluate performance benchmarks and identify a path to closure.

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Superfund Site Remediation Program Oversight and Optimization

Northgate provided program oversight of the groundwater remediation and restoration program at a large, multi-party Superfund site in the Santa Clara Valley. The remediation program entails containment and treatment of a one-mile long solvent-contaminated groundwater plume migrating beneath commercial and residential properties. Northgate developed strategies to optimize the 25-year old pump-and-treat program, characterized and evaluated the feasibility of sustainable remediation alternatives, implemented innovative technologies to move the project toward closure, and performed a sustainability assessment to streamline the operations, maintenance, and monitoring program to save energy, water, and costs. Northgate also provided strategic analysis to focus data collection and analysis, identify potential future liabilities, and develop risk-based mitigation measures appropriate for current and future development.

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MarketCenter Railyard Redevelopment

San Jose

Northgate performed rapid site assessment, site characterization studies, and remediation services during the redevelopment of a 40-acre former railyard in San Jose, California. The property was redeveloped as San Jose MarketCenter, a mixed-use shopping center. Northgate prepared a complete evaluation of options and associated costs for excavation and treatment or disposal of impacted soil. Northgate subsequently prepared a Risk Management Plan for the site with the ultimate goal of maximizing reuse of soil and minimizing offsite disposal. A sophisticated soil segregation and re-allocation technique enabled the successful reuse of a significant portion of site soils, thereby minimizing disposal volume, costs, and trucking impacts. Engineered caps and passive vapor mitigation systems were also incorporated into the construction design. Northgate developed an Operation and Maintenance Manual that currently serves as a guidance document for MarketCenter employees and tenants. Northgate successfully negotiated site closure and obtained a finding of No Further Action (NFA) for the site. In addition, the use of a risk-based mitigation program and integration of remediation with development ultimately reduced cleanup costs by over $30M.

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Investigation and Remedial Planning

Driscoll Ranch

Driscoll Ranch is a key landholding of the Midpeninsula Regional Open Space District, whose planned expansion of the adjacent La Honda Creek Open Space Preserve includes the 3,600-acre Driscoll Ranch, creating one of the largest regional ecological preserves on the San Mateo County coastline. Northgate helped the District develop and implement a strategic plan to add Driscoll Ranch to the preserve, and provided remedial planning and a detailed site investigation for contamination related to historical uses, including oil drilling and cattle ranching. Northgate developed site-specific cleanup levels for soil contaminated with petroleum hydrocarbons, polycyclic aromatic hydrocarbons, and pesticides, and developed a Site Management Plan to permit safe public access to the ecological preserve. We concluded that environmental conditions would not pose a risk to groundwater, surface water, or the health of visitors at the future ecological preserve, and that residual impacts be managed in-place through administrative mechanisms, avoiding costly remedial measures and expediting property access. The San Francisco Bay Regional Water Quality Control Board approved the Soil Management Plan and issued a "No Further Action" letter.

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Former Benicia Arsenal Chemical and Munitions Cleanup

Benicia, California

Northgate served as the program manager, lead engineer, and contractor to clean up and restore the Tourtelot Property (a portion of the former Benicia Arsenal) for future residential development and to provide open space and wetlands. Northgate developed a remedial exit strategy, prepared remedial investigation documents (RI/FS, RAP), remedial design documents, and bid specifications, and remediated soils impacted with munitions and explosives of concern (MEC). We conducted human health and ecological risk assessments for explosives and chemically-affected areas following remediation to verify that residual levels of explosives and other constituents were protective of human health and the environment. Northgate was the key regulatory liaison and successfully obtained a "No Further Action" regulatory decision for the site—the first MEC site in California to receive regulatory approval of unrestricted residential development. Northgate continues to provide operation and maintenance services related to surface water and wetlands mitigation monitoring.

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Superfund Site Remediation Program Oversight and Optimization

Northgate provided program oversight of the groundwater remediation and restoration program at a large, multi-party Superfund site in the Santa Clara Valley. The remediation program entails containment and treatment of a one-mile long solvent-contaminated groundwater plume migrating beneath commercial and residential properties. Northgate developed strategies to optimize the 25-year old pump-and-treat program, characterized and evaluated the feasibility of sustainable remediation alternatives, implemented innovative technologies to move the project toward closure, and performed a sustainability assessment to streamline the operations, maintenance, and monitoring program to save energy, water, and costs. Northgate also provided strategic analysis to focus data collection and analysis, identify potential future liabilities, and develop risk-based mitigation measures appropriate for current and future development.

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Geotechnical Engineering
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Elmhurst Creek Sediment Removal and Bridge Replacement

Northgate provides environmental, permitting, and geotechnical services on this project, which involves the excavation of contaminated sediment from a segment of Elmhurst Creek in East Oakland. The project also includes the replacement of a culvert and bridge. Northgate evaluated existing environmental conditions, assessed sediment quality, and conducted a geotechnical investigation for the bridge foundations. Northgate prepared a Joint Aquatic Resources Permit Application (JARPA) application for the work, coordinated agency responses to comments, and worked with the client, land owners, attorneys, consultants, and agencies to resolve project issues. The Northgate team is also preparing all CEQA documentation related to the project. The agencies participating in the project include the City of Oakland, U.S. Army Corps of Engineers, California Department of Fish and Game, and the San Francisco Bay Regional Water Quality Control Board.

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Geotechnical Engineering for Communications Infrastructure

Northgate conducted geotechnical field investigations, seismic analysis, and liquefaction assessments for Sprint-Nextel Communications to support their development of additional communications infrastructure in Southern California. Following the geotechnical investigations and analyses, Northgate developed foundation recommendations and prepared geotechnical investigation reports for more than 70 sites in Los Angeles, San Bernardino, and Riverside Counties. Northgate also provided construction oversight services that included compaction testing, oversight of foundation construction, and report preparation.

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Rosamond Solar Farm

Antelope Valley, California

Northgate conducted a geotechnical investigation of a property for suitability as a solar farm. Northgate investigated the site to assess pertinent subsurface data, and submitted geotechnical samples to measure subsurface soil characteristics. Northgate performed an engineering analysis to determine appropriate geotechnical engineering design criteria, and prepared a report summarizing the results and presenting recommendations for design.

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Passive Remediation System, Shinsei Gardens Housing Development, Fleet Industrial Supply Center

Alameda, California

Northgate prepared a Removal Action Workplan and developed and evaluated cleanup alternatives for volatile org...

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Passive Remediation System, Shinsei Gardens Housing Development, Fleet Industrial Supply Center

Alameda, California

Northgate prepared a Removal Action Workplan and developed and evaluated cleanup alternatives for volatile organic compounds and petroleum-related chemicals in soil, soil gas, and groundwater at the former Fleet Industrial Supply Center in Alameda, California. The California Department of Toxic Substances Control required the use of engineering controls to mitigate vapor intrusion risk to indoor air of a planned affordable housing project at the site. Northgate recommended a passive sub-slab depressurization system as an effective, sustainable, and cost-effective technology. Northgate designed the system to recirculate fresh air beneath the residential buildings and reduce the potential for drawing impacted soil gas into the depressurization system. The system included a vapor barrier, clean air intakes, and wind turbines to draw air through the system. Northgate provided oversight for system installation and testing, conducted initial monitoring to verify its effectiveness, and prepared the operations and maintenance plan. Northgate continues to provide annual inspections and maintenance of the system.

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Former Almaden Air Force Station Redevelopment

Mt. Umunhum Open Space and Park

The Former Almaden Air Force Station, purchased from the Department of Defense in the 1980s, is currently undergoing environmental investigation and cleanup of contaminants in preparation of its transition to publically-accessible open space and park land. Located within the Sierra Azul Open Space Preserve, Mt. Umunhum is a prominent Bay Area landmark, and is envisioned to be a significant recreational destination. Northgate oversaw a series of engineering and hazardous materials studies to support the Midpeninsula Regional Open Space District's planning efforts and CEQA/NEPA requirements. Studies included hazardous materials surveys of several abandoned buildings, a structural survey of the five-story Radar Tower, a slope stability investigation at the Radar Tower site, a cultural and historical assessment survey of the former Air Force Station, and soil sampling and analysis to assess environmental contamination. Northgate reviewed the investigation and cleanup work being completed by the US Army Corps of Engineers and represented the District's interests in communications with the Corps and state regulatory agencies. Northgate also assisted the District with engineering studies including structural analysis, rock slope stability analysis, serpentinite geologic mapping, hazardous materials studies, and soil characterization for lead, asbestos, and pesticides. We leveraged our experience with environmental issues on lands being converted from military or industrial uses to parks and ecological preserves to support the District in its mission to acquire and manage land for wildlife habitat and to provide safe and educational public access to these lands.

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Elmhurst Creek Sediment Removal and Bridge Replacement

Northgate provides environmental, permitting, and geotechnical services on this project, which involves the excavation of contaminated sediment from a segment of Elmhurst Creek in East Oakland. The project also includes the replacement of a culvert and bridge. Northgate evaluated existing environmental conditions, assessed sediment quality, and conducted a geotechnical investigation for the bridge foundations. Northgate prepared a Joint Aquatic Resources Permit Application (JARPA) application for the work, coordinated agency responses to comments, and worked with the client, land owners, attorneys, consultants, and agencies to resolve project issues. The Northgate is also preparing all CEQA documentation related to the project. The agencies participating in the project include the City of Oakland, U.S. Army Corps of Engineers, California Department of Fish and Game, and the San Francisco Bay Regional Water Quality Control Board.

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Sustainable Solutions
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Environmental Impact Review

Former Paint Manufacturing Facility

Northgate provides environmental consulting services at a former paint manufacturing facility located in Los Angeles County. Previous investigations identified contaminants in soil vapor, dissolved in shallow groundwater, and as a layer of light non-aqueous phase liquid (LNAPL). Remedial actions to mitigate chemical impacts have been underway since 1987, initially through product removal by mechanical means, and subsequently with the installation of a soil vapor extraction (SVE) and bioventing system to remove product and stimulate biodegradation of residual source-zone contaminants. Northgate conducted a review of the remedial system and provided recommendations for immediate action to eliminate threats to underlying aquifers. Northgate is now working with the responsible party to reduce current and long-term operating costs by optimizing the existing SVE system and using a risk-based approach to evaluate performance benchmarks and identify a path to closure.

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Superfund Site Remediation Program Oversight and Optimization

Northgate provided program oversight of the groundwater remediation and restoration program at a large, multi-party Superfund site in the Santa Clara Valley. The remediation program entails containment and treatment of a one-mile long solvent-contaminated groundwater plume migrating beneath commercial and residential properties. Northgate developed strategies to optimize the 25-year old pump-and-treat program, characterized and evaluated the feasibility of sustainable remediation alternatives, implemented innovative technologies to move the project toward closure, and performed a sustainability assessment to streamline the operations, maintenance, and monitoring program to save energy, water, and costs. Northgate also provided strategic analysis to focus data collection and analysis, identify potential future liabilities, and develop risk-based mitigation measures appropriate for current and future development.

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MarketCenter Railyard Redevelopment

San Jose

Northgate performed rapid site assessment, site characterization studies, and remediation services during the redevelopment of a 40-acre former railyard in San Jose, California. The property was redeveloped as San Jose MarketCenter, a mixed-use shopping center. Northgate prepared a complete evaluation of options and associated costs for excavation and treatment or disposal of impacted soil. Northgate subsequently prepared a Risk Management Plan for the site with the ultimate goal of maximizing reuse of soil and minimizing offsite disposal. A sophisticated soil segregation and re-allocation technique enabled the successful reuse of a significant portion of site soils, thereby minimizing disposal volume, costs, and trucking impacts. Engineered caps and passive vapor mitigation systems were also incorporated into the construction design. Northgate developed an Operation and Maintenance Manual that currently serves as a guidance document for MarketCenter employees and tenants. Northgate successfully negotiated site closure and obtained a finding of No Further Action (NFA) for the site. In addition, the use of a risk-based mitigation program and integration of remediation with development ultimately reduced cleanup costs by over $30M.

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Passive Remediation System, Shinsei Gardens Housing Development, Fleet Industrial Supply Center

Alameda, California

Northgate prepared a Removal Action Workplan and developed and evaluated cleanup alternatives for volatile org...

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Passive Remediation System, Shinsei Gardens Housing Development, Fleet Industrial Supply Center

Alameda, California

Northgate prepared a Removal Action Workplan and developed and evaluated cleanup alternatives for volatile organic compounds and petroleum-related chemicals in soil, soil gas, and groundwater at the former Fleet Industrial Supply Center in Alameda, California. The California Department of Toxic Substances Control required the use of engineering controls to mitigate vapor intrusion risk to indoor air of a planned affordable housing project at the site. Northgate recommended a passive sub-slab depressurization system as an effective, sustainable, and cost-effective technology. Northgate designed the system to recirculate fresh air beneath the residential buildings and reduce the potential for drawing impacted soil gas into the depressurization system. The system included a vapor barrier, clean air intakes, and wind turbines to draw air through the system. Northgate provided oversight for system installation and testing, conducted initial monitoring to verify its effectiveness, and prepared the operations and maintenance plan. Northgate continues to provide annual inspections and maintenance of the system.

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Wetlands Restoration

Yosemite Slough, Candlestick Point

The Yosemite Slough wetland restoration is the centerpiece of a long-term project to clean up contamination, restore tidal wetlands on filled lands, and improve habitat quality of associated transitional and upland areas on Candlestick Point in San Francisco. The restoration design provides public shoreline access, wetlands and wildlife habitat, bird nesting islands, transitional and upland buffer areas for sensitive habitats, interpretive trails, and an education center. Northgate conducted a remedial investigation and feasibility study, mapped the distribution of contamination using soil sampling combined with a geographic information system (GIS), and developed an environmental model. Detailed data visualizations facilitated negotiation of risk-based cleanup levels with the San Francisco Bay Regional Water Quality Control Board. The remedial strategy relies on detailed characterization and excavation of over 230,000 cubic yards of fill, and careful segregation, management, and reuse of onsite soil to reduce chemical concentrations in wetland cover soils to near-ambient sediment concentrations. While most of the soil met action goals, the soil associated with an underground storage tank and former metals fabrication facility exceeded the action goals for total lead for onsite reuse. Northgate stabilized this stream with onsite treatment to reduce lead solubility to below toxicity characteristic leaching procedure (TCLP) levels, tested the soil to confirm waste characterization, and disposed of the material offsite at a licensed landfill. Northgate also provided geotechnical engineering analysis, developed bid specifications for contractor selection, provided construction compliance monitoring, and participated in public outreach activities.

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Wetlands Restoration and Corrective Action Plan

Sears Point

The Sears Point Wetland Restoration Project encompasses more than 2,300 acres of agricultural land owned by the Sonoma Land Trust (SLT), which is restoring the area to tidal wetlands. The former shooting range contains sediments contaminated with lead and polycyclic aromatic hydrocarbons. Northgate defined contaminant distribution and quantified residual lead concentrations in surface and shallow soil and groundwater. We used characterization data to evaluate potential impacts to wetland flora and fauna and to develop cleanup criteria for ecological protection. Northgate developed and evaluated remedial alternatives consistent with the future wetlands scenario, working closely with wetlands scientists, stakeholders, and the San Francisco Bay Regional Water Quality Control Board. We prepared a Corrective Action Plan, approved by the Water Board, which specifies removing contaminated material from the sensitive area and using it as borrow material in upland perimeter levees. This cost-effective solution provides material for levee construction, removes contaminated material from sensitive habitats, and lowers the site elevation to suitable levels for tidal wetlands development.

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Public Outreach
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Investigation and Remediation

Former Braito Landfill, Benicia, California

Northgate performed comprehensive assessment and remediation of an approximate 60-acre residential development that had been partially constructed over a former landfill. Northgate's work, which began when refuse surfaced in residential backyards, included complete evaluation of historic land use, including review of facility operating records, development and implementation of a detailed characterization plan, evaluation of human health and environmental health risks, and implementation of site cleanup. Northgate prepared excavation, shoring, and underpinning plans, as well as remediation monitoring and contingency plans to ensure safety of nearby residents. Northgate performed soil gas extraction and treatment, in-situ stabilization of buried wastes, storm water management, and offsite transportation and disposal of hazardous and non-hazardous wastes. Northgate saved our client over $2M in disposal costs by using an innovative statistical analysis to establish that the majority of the waste could be classified as non-hazardous, and treating hazardous wastes to become non-hazardous. Northgate also developed and implemented public participation programs, and participated in Community Advisory Group meetings, workshops, and various agency meetings. Northgate negotiated final cleanup levels, and worked with our client's attorneys to prepare final documents, disclosures, and deed restrictions for the site following remediation. Northgate received a special recognition award from the City of Benicia following successful completion of the project.

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Former Benicia Arsenal Chemical and Munitions Cleanup

Benicia, California

Northgate served as the program manager, lead engineer, and contractor to clean up and restore the Tourtelot Property (a portion of the former Benicia Arsenal) for future residential development and to provide open space and wetlands. Northgate developed a remedial exit strategy, prepared remedial investigation documents (RI/FS, RAP), remedial design documents, and bid specifications, and remediated soils impacted with munitions and explosives of concern (MEC). We conducted human health and ecological risk assessments for explosives and chemically-affected areas following remediation to verify that residual levels of explosives and other constituents were protective of human health and the environment. Northgate was the key regulatory liaison and successfully obtained a "No Further Action" regulatory decision for the site—the first MEC site in California to receive regulatory approval of unrestricted residential development. Northgate continues to provide operation and maintenance services related to surface water and wetlands mitigation monitoring.

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PCB Runoff Prevention Plan

Alameda County Clean Water Program

In 2010, the U.S. EPA approved a Total Maximum Daily Load (TMDL) for polychlorinated biphenyls (PCBs) in the San Francisco Bay. As part of the TMDL implementation, the Municipal Regional Storm Water Permit requires local municipalities to take steps to reduce controllable sources of PCBs that can migrate to the Bay. Northgate supported the Alameda County Clean Water Program in a pilot project designed to identify potential PCB sources in construction materials and implement best management practices (BMPs) to reduce PCBs in storm water runoff. At the client's request, Northgate evaluated the draft BMPs for completeness and effectiveness. Northgate developed materials to support the Model Implementation Process and participated in role-playing exercises with the client and with other stakeholders at the municipal and state level.

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Wetlands Restoration

Yosemite Slough, Candlestick Point

The Yosemite Slough wetland restoration is the centerpiece of a long-term project to clean up contamination, restore tidal wetlands on filled lands, and improve habitat quality of associated transitional and upland areas on Candlestick Point in San Francisco. The restoration design provides public shoreline access, wetlands and wildlife habitat, bird nesting islands, transitional and upland buffer areas for sensitive habitats, interpretive trails, and an education center. Northgate conducted a remedial investigation and feasibility study, mapped the distribution of contamination using soil sampling combined with a geographic information system (GIS), and developed an environmental model. Detailed data visualizations facilitated negotiation of risk-based cleanup levels with the San Francisco Bay Regional Water Quality Control Board. The remedial strategy relies on detailed characterization and excavation of over 230,000 cubic yards of fill, and careful segregation, management, and reuse of onsite soil to reduce chemical concentrations in wetland cover soils to near-ambient sediment concentrations. While most of the soil met action goals, the soil associated with an underground storage tank and former metals fabrication facility exceeded the action goals for total lead for onsite reuse. Northgate stabilized this stream with onsite treatment to reduce lead solubility to below toxicity characteristic leaching procedure (TCLP) levels, tested the soil to confirm waste characterization, and disposed of the material offsite at a licensed landfill. Northgate also provided geotechnical engineering analysis, developed bid specifications for contractor selection, provided construction compliance monitoring, and participated in public outreach activities.

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Wetlands Restoration and Corrective Action Plan

Sears Point

The Sears Point Wetland Restoration Project encompasses more than 2,300 acres of agricultural land owned by the Sonoma Land Trust (SLT), which is restoring the area to tidal wetlands. The former shooting range contains sediments contaminated with lead and polycyclic aromatic hydrocarbons. Northgate defined contaminant distribution and quantified residual lead concentrations in surface and shallow soil and groundwater. We used characterization data to evaluate potential impacts to wetland flora and fauna and to develop cleanup criteria for ecological protection. Northgate developed and evaluated remedial alternatives consistent with the future wetlands scenario, working closely with wetlands scientists, stakeholders, and the San Francisco Bay Regional Water Quality Control Board. We prepared a Corrective Action Plan, approved by the Water Board, which specifies removing contaminated material from the sensitive area and using it as borrow material in upland perimeter levees. This cost-effective solution provides material for levee construction, removes contaminated material from sensitive habitats, and lowers the site elevation to suitable levels for tidal wetlands development.

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MEC
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Former Benicia Arsenal Chemical and Munitions Cleanup

Benicia, California

Northgate served as the program manager, lead engineer, and contractor to clean up and restore the Tourtelot Property (a portion of the former Benicia Arsenal) for future residential development and to provide open space and wetlands. Northgate developed a remedial exit strategy, prepared remedial investigation documents (RI/FS, RAP), remedial design documents, and bid specifications, and remediated soils impacted with munitions and explosives of concern (MEC). We conducted human health and ecological risk assessments for explosives and chemically-affected areas following remediation to verify that residual levels of explosives and other constituents were protective of human health and the environment. Northgate was the key regulatory liaison and successfully obtained a "No Further Action" regulatory decision for the site—the first MEC site in California to receive regulatory approval of unrestricted residential development. Northgate continues to provide operation and maintenance services related to surface water and wetlands mitigation monitoring.

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Munitions and Explosives Investigation

Former Santa Rosa Army Airfield

Northgate conducted an investigation at the Apex Aviation Sonoma County Airport for munitions and explosives of concern (MEC), chemical warfare materials (CWM), and common environmental pollutants. The site was formerly part of the Santa Rosa Army Airfield and the presence of both MEC and CWM had been reported in the general vicinity. Northgate prepared the investigation plans (Work Plan, Health and Safety Plan, and Soil Sampling Plan). Northgate personnel investigated each of the hundreds of targeted anomalies to determine their sources. Blind seeding was used as a quality assurance measure and 100 percent of the seeds were recovered during the investigation. Northgate also sampled soils for the presence of CWM and common environmental pollutants. Northgate's investigation concluded that the site did not contain MEC or CWM.

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Fort Pickett Range Cleanup and Renovation

Blackstone, Virginia

Northgate investigated and removed munitions and explosives of concern (MEC) from a 2,000-acre area as part of the renovation of Range 15 at Fort Pickett in Blackstone, Virginia. Northgate conducted an environmental site assessment of the facility in preparation for remediation activity. The assessment included records review, personnel interviews, and field surveys for MEC and chemical agents. Northgate mapped the property and conducted surface sweeps of the 730-acre construction area, and cleared the surface and subsurface of the 156-acre cut/fill construction area to a depth of 4 feet. The clearance area included munitions disposal sites and target placement areas. Northgate removed several target backstop berms and mobile target rail track systems. We safely recovered and disposed more than 1,500 hazardous MEC items ranging in size from 20 mm to 106 mm. Munitions clearance activities were accomplished without compromise to either planned construction activities or explosive safety standards.

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Former Benicia Arsenal Chemical and Munitions Cleanup

Benicia, California

Northgate served as the program manager, lead engineer, and contractor to clean up and restore the Tourtelot Property (a portion of the former Benicia Arsenal) for future residential development and to provide open space and wetlands. Northgate developed a remedial exit strategy, prepared remedial investigation documents (RI/FS, RAP), remedial design documents, and bid specifications, and remediated soils impacted with munitions and explosives of concern (MEC). We conducted human health and ecological risk assessments for explosives and chemically-affected areas following remediation to verify that residual levels of explosives and other constituents were protective of human health and the environment. Northgate was the key regulatory liaison and successfully obtained a "No Further Action" regulatory decision for the site—the first MEC site in California to receive regulatory approval of unrestricted residential development. Northgate continues to provide operation and maintenance services related to surface water and wetlands mitigation monitoring.

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Former Benicia Arsenal Chemical and Munitions Cleanup

Benicia, California

Northgate served as the program manager, lead engineer, and contractor to clean up and restore the Tourtelot Property (a portion of the former Benicia Arsenal) for future residential development and to provide open space and wetlands. Northgate developed a remedial exit strategy, prepared remedial investigation documents (RI/FS, RAP), remedial design documents, and bid specifications, and remediated soils impacted with munitions and explosives of concern (MEC). We conducted human health and ecological risk assessments for explosives and chemically-affected areas following remediation to verify that residual levels of explosives and other constituents were protective of human health and the environment. Northgate was the key regulatory liaison and successfully obtained a "No Further Action" regulatory decision for the site—the first MEC site in California to receive regulatory approval of unrestricted residential development. Northgate continues to provide operation and maintenance services related to surface water and wetlands mitigation monitoring.

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