Gary Manhart

Gary L. Manhart

Senior Engineering Geologist

Mr. Gary Manhart is a Senior Engineering Geologist and a key member of LACO Associates’ outstanding geologic team. With over 25 years of experience in geology and environmental science, Mr. Manhart has honed his geologic and communication skills through a wide verity of development work. He originally joined LACO in 1995 and served as a Senior Staff Geologist until 2007 when he moved to Virginia. Mr. Manhart rejoined the LACO team in 2014, as a Senior Engineering Geologist. Mr. Manhart’s experience working all over northern California has given him a wealth of knowledge on the geology and geomorphology and how it affects client’s projects.

Mr. Manhart can work collaboratively with many stakeholders and is easily approachable. He has a strong collaborative nature which allows for good communications between all parties.  Mr. Manhart has developed innovative solutions to problems that have arisen during site development facilitating the successful completion of projects. Mr. Manhart is always willing to share his knowledge and works to help his clients understand the complex geologic issues that often come with site development. Mr. Manhart continually educates and mentors LACO’s geology staff to help them further their careers and promote their professional growth. 

During Mr. Manhart’s time with LACO, he has successfully investigated sites for a verity of geologic issues; fault evaluations to site both private and public infrastructure, geotechnical and geologic hazard reports, environmental site evaluations and remediation, stormwater pollution prevention plans, materials testing, construction management, and hydrologic assessment.

Areas of Expertise


Hillslope Processes

Fluvial Processes

Slope Instability Analysis


Aerial Photographic Interpretation

Remediation Design

Phase I/II Environmental Site Assessments


BA in Geology, Humboldt State University, Arcata, CA

Continuing Education

Fundamentals of Project Management – ASFE 

In Situ Chemical Oxidation – AEHS

Spreadsheet Analytical Model to Estimate MTBE Plume Life & Travel Time – AEHS

Geotechnical and Environmental Site Investigation using the Cone Penetration Test – Gregg Drilling

NGWA Intro to Ground Water & modeling – National Ground Water Association

Introduction to Groundwater Geochemistry – Bill Deutsch, Hosted by AEG

Registrations and Certifications

Professional Geologist – California License No. 7169

Professional Geologist – Oregon License No. G2103

Professional Geologist – Washington License No. 2447

Professional Geologist – Virginia License No. 1781

Professional Geologist – North Carolina License No. 2265

Professional Geologist – South Carolina License No. 2546

Professional Geologist – Georgia License No. 002084

Hazardous Waste Site Operation Training (EPA) 40 hour – OSHA 29 CFR 1910.120

Nuclear Gauge Safety and Operation Course – CPN Corporation

Trench Shoring Safety Seminar/Competent Person – The Plank Company

Fall Protection Training program – AGC

Select Project Experience
Coastal Erosion and Slope Stability Analysis – Radcliff project, Big Lagoon, California.

Mr. Manhart completed a slope stability analysis and coastal erosion exploration to support the development of an oceanfront property near Big Lagoon, California. The primary goal of the project was to establish a development setback from rapidly eroding bluffs with the intent of providing at least a 75-year lifespan for the development. The project involved aerial photo analysis, quantitative slope stability analysis, geomorphic mapping, and interaction with the California Coastal Commission. 

Private and Commercial Development.

Mr. Manhart has completed geotechnical soils and geologic hazard explorations for a variety of private and commercial buildings in California, Maryland, and Delaware. The investigations for the sites included deep drilling with a geotechnical drill rig, a quantitative liquefaction analysis, settlement, and design recommendations to mitigate the poor soils conditions.  

Private Trench-Based Fault Hazard Explorations – Humboldt County, California.

Mr. Manhart has completed several trench-based fault hazard explorations on the McKinleyville, Trinidad, and Little Salmon fault systems in Humboldt County, California. He conducted the fault explorations to support the single-family residential development and DSA regulated development. The trench-based fault hazard explorations have generally included aerial photo analysis, stratigraphic analysis within open excavations, preparation of technical reports, and interaction with local and state agencies. 

City of Arcata – Arcata, California.

Mr. Manhart was the senior geologist for a fault hazard evaluation in support of a proposed residential development. The report was accepted by the reviewing geologist for the City of Arcata. 

Town of Wytheville 20-inch Water Main Project – Wytheville, Virginia.

In 2012, Mr. Manhart served as a resident inspector for the construction of 17,000 feet of 20-inch water main in downtown Wytheville. Mr. Manhart prepared daily reports, coordinated testing, spoils disposal and obtained data for compliance reporting to the Town of Wytheville. Construction valued at $4.3 million.

UST Removal, Investigation and Remediation – Maryland, Delaware, Virginia, West Virginia, North Carolina, South Carolina, and California.

Mr. Manhart coordinated, supervised, and implemented various subsurface investigations to collect soil and groundwater data related to a release of petroleum hydrocarbons resulting from USTs. Mr. Manhart prepared Corrective Action Plans for the remediation of soil and groundwater, and completed technical submittals to governing regulatory agencies.

Public/Private Clients.

Mr. Manhart has designed subsurface investigations and logged soils from hundreds of locations in California, Oregon, Maryland, Delaware, Virginia, West Virginia, North Carolina, South Carolina, Georgia, and Tennessee utilizing a variety of drilling technologies including hollow-stem auger, direct push, mud-rotary, and sonic.

College of the Redwoods Building Evaluation – Eureka, California.

LACO conducted a Phase 3 and Phase 4 fault investigation to evaluate potential building sites on campus. Mr. Manhart coordinated all aspects of excavation actives and equipment. His field responsibilities included safety evaluation of trenches, cleaning of trench walls, logging, and mapping. Mr. Manhart also managed the production of the fault evaluation report. Investigation valued at $886,000.

College of the Redwoods Building Evaluation – Eureka, California.

Mr. Manhart is the senior site geologist for a fault hazard evaluation in support of a new Gymnasium Complex. This report was submitted to the California Geological Survey

Hoopa Valley Tribal Council Road Construction – Hoopa, California.

During the 1998 construction season, Mr. Manhart served as resident inspector for roadway and utility construction. He prepared daily reports and obtained data for labor compliance reporting. Construction valued at $865,000.

Stafford Debris Basin/Pacific Lumber Co. – Stafford, California.

In 1999, Mr. Manhart served as resident inspector for construction of a debris basin to mitigate possible debris flows. Mr. Manhart prepared daily reports, coordinated survey and obtained data for labor compliance reporting. Construction valued at $950,000.

Site Septic Evaluations and System Design for Public/Private Clients.

Mr. Manhart has designed subsurface investigations and logged soils from hundreds of locations in California, Oregon, Maryland, Delaware, Virginia, to evaluate site soils for septic suitability and percolation testing. Mr. Manhart has prepared system designs for construction from standard leach field systems to alternative treatment systems.

Phase I and II Environmental Site Assessment Public/Private Clients.

Mr. Manhart has prepared Phase I and II Environmental Site Assessment (ESA) for over a hundred locations in California, Maryland, Delaware, Virginia, West Virginia, and North Carolina.  Recognized Environmental Conditions. (RECs) included waste oil releases, burn pits, dry cleaners, gasoline agricultural chemicals, industrial chemicals and uncontrolled fill. Mr. Manhart has prepared over 15 Phase I ESAs for Brownfield properties including former lumber mills, gas stations, vehicle maintenance facilities, and a pulp mill facility.  Phase II ESAs were performed on several properties using both surface and subsurface explorations.

  • Home Office: Eureka, CA

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