S.S. Papadopulos & Associates, Inc.

What S.S. Papadopulos & Associates, Inc. does

S.S. Papadopulos & Associates, Inc. (SSP&A) is a Rockville, Maryland-based, employee-owned environmental consulting firm founded in 1979 by Dr. Stavros S. Papadopulos. The firm specializes in groundwater resource evaluation, contaminant fate-and-transport modeling, geochemistry, geophysical investigations, engineering and remediation, and expert witness services for federal and state government agencies, industrial clients (chemical manufacturing, energy, manufacturing), and legal counsel in complex water-rights and environmental litigation, including matters before the U.S. Supreme Court.

SSP&A's technical platform centers on a portfolio of proprietary groundwater-modeling software built and continuously enhanced through contracts with USGS, USEPA, USDOE, USACE, and California DWR. Flagship tools include MT3D-USGS (the most widely used solute transport simulator in the world), GroundWater Desktop (a 3D visualization interface for MODFLOW, MODFLOW-USG, MT3D, MODPATH, and IWFM), mod-PATH3DU (particle tracking on structured and unstructured grids), Texture2Par (AEM-informed aquifer parameterization), and PEST.cloud (Azure-hosted model calibration); supporting modules include ATRANS, BIOSCREEN-AT, GENIE, OPR-PPR, MPNE1D, SSM, and the patented Well-DOC well-fouling abatement system. The firm integrates ML and LLM-based RAG into document-heavy litigation and data-analysis workflows.

Revenue is generated primarily through project-based professional-services contracts with government and enterprise clients, supplemented by one-time paid licensing of the professional MT3D99 code, fee-based national and international software training, and publication royalties. The firm operates from offices in Potomac/Boulder, San Francisco, Minnesota, Maine, Maryland/DC, West Virginia, and Waterloo, Ontario, with marketing driven by professional affiliations, technical publications, conference presentations, and free software distribution.

Name

S.S. Papadopulos & Associates, Inc.

Legal name

S.S. Papadopulos & Associates, Inc.

Website

https://sspa.com

Company type

Private

Founded year

1979

Operating status

Operating

Headcount range

101–250 employees

Short description

S.S. Papadopulos & Associates is an employee-owned environmental consultancy that delivers specialized groundwater modeling, contaminant fate-and-transport analysis, geochemistry, remediation engineering, and expert-witness services to U.S. federal and state agencies, industrial clients, and legal counsel, and develops the widely used MT3D-USGS, GroundWater Desktop, mod-PATH3DU, Texture2Par, and PEST.cloud software.

Ownership category

akta.pro rank

Product category

Environmental Consulting Services

NAICS

Environmental Consulting Services (54162), Custom Computer Programming Services (541511), Other Computer Related Services (541519)

SIC

Services-Engineering Services (8711), Services-Commercial Physical & Biological Research (8731)

akta.pro primary industry

Water, Wastewater & Hydraulics Engineering Consulting (BPAHAIAD)

akta.pro secondary industries

Groundwater & Contaminant Fate/Transport Modeling (MODFLOW/MT3D, Plume Modeling) (EUAHAKAG), Water Quality & Watershed/Hydrologic Modeling (SWMM/HEC-RAS, Flood/Runoff/Nutrient) (EUAHAKAF), Groundwater Extraction, Treatment & Discharge (Pump-and-Treat, reinjection) (BPALAKAF)

Keywords

• Groundwater modeling software
• Environmental consulting services
• Contaminant transport modeling
• Hydrogeology consulting
• Environmental remediation services

Headquarters

HQ city

Rockville

HQ country

United States

HQ region

North America

Offices8 records

Markets served

GTM type

B2B

Offering type

Services

Cost components

Personnel, Technology or R&D, Operations, Infrastructure, Marketing or Sales

Revenue model

1. Environmental Consulting Services: Project-based consulting engagements for groundwater modeling, hydrogeology, geochemistry, environmental remediation, site assessments, expert witness and litigation support. Revenue generated through professional service fees on contracts with government agencies, industrial clients, and legal firms.
2. Software Licensing (MT3D99): Many software programs are provided free-of-charge. A professional version of MT3D, referred to as MT3D99, is available for purchase.
3. Software Training: Training courses provided nationally and internationally for software tools developed by SSP&A and related professional courses on calibration and uncertainty analysis.

Pricing tiers

Go-to-market motion1 record

Distribution channels3 records

Marketing channels4 records

Core offering

SSP&A delivers project-based groundwater and environmental consulting services (modeling, hydrogeology, geochemistry, engineering/remediation, geophysics, field services, data management, and expert witness/litigation support) to government agencies and industrial clients. It also develops and distributes specialized groundwater modeling software (MT3D-USGS, GroundWater Desktop, mod-PATH3DU, Texture2Par, PEST.cloud, and supporting tools), most of which is provided free-of-charge with a paid professional version (MT3D99).

Product overview

S.S. Papadopulos & Associates, Inc. (SSP&A) is an internationally recognized groundwater and environmental consulting firm that develops and distributes specialized groundwater modeling software alongside providing professional consulting services. Their product portfolio centers on groundwater flow and transport simulation tools: GroundWater Desktop provides 3D visualization for MODFLOW, MT3D, MODPATH, and IWFM models; MT3D-USGS (the most widely used solute transport simulator worldwide) handles contaminant fate-and-transport modeling; mod-PATH3DU performs particle tracking; Texture2Par parameterizes aquifer properties; and PEST.cloud enables cloud-based model calibration. These software offerings are complemented by professional services including environmental modeling and hydrogeology, geochemistry (PFAS, isotopes, MNA), engineering and remediation, geophysics, data management with ML/LLM capabilities, field services, and expert witness/litigation support. The company maintains continuous improvement through contracts with USGS, USEPA, USDOE, USACE, and California DWR.

Differentiator

Problem solved

Functional benefit

Brands

• GroundWater Desktop: A flexible and intuitive 3D interface that allows scientists to explore, understand and visualize groundwater models, geologic and spatial data. Supports MODFLOW, MODPATH, MT3D, MODFLOW-USG, and IWFM.

Products and services

• GroundWater Desktop (GWD) A fully 3D interface to visualize groundwater models and environmental data, supporting MODFLOW, MODPATH, MT3D, unstructured grid MODFLOW-USG, and finite-element IWFM models with VTK-based cross-sectional, cut-away, and layer-exploded views. For groundwater modelers and environmental scientists.
• MT3D-USGS The most widely used solute transport simulator in the world, originally developed at SSP&A, supporting unsaturated zone transport, salt and nutrient transport within streams and lakes, kinetic reactive transport, pump-and-treat remedies, and the Hydrocarbon Spill-Source Package (HSS). Released in collaboration with USGS.
• mod-PATH3DU 3D particle-tracking program for structured and unstructured grids that calculates pathlines in MODFLOW and MODFLOW-USG models. Supports quadpatch, quadtree, Voronoi, triangular, and nested grids with linear-sorption and random-walk modules.
• Texture2Par Co-developed with California DWR; integrates sediment texture data to construct hydrogeological conceptual models and estimate aquifer properties in MODFLOW and IWFM models, with optional integration of Airborne Electromagnetic (AEM) data as co-variates.
• PEST.cloud Web-based cloud tool for model calibration using PEST on Microsoft Azure, streamlining compute node setup, file distribution, and run monitoring with easy result packaging and downloads. Developed in collaboration with Dr. John Doherty.
• ATRANS Exact analytical solution for 3D transport with decay and retardation, used for screening-level and detailed groundwater transport analysis.
• BIOSCREEN-AT Enhanced version of USEPA's BIOSCREEN that incorporates the ATRANS solution as an alternative to Domenico's approximate solution for 1D transport with decay and retardation.
• KT3D_H2O Generates gridded maps of groundwater elevations using hydrologically based trends to account for pumping, boundaries, and surface-water features; combined with particle tracking for capture zones and contaminant fate calculations.
• MPNE1D 1D multi-species transport model with dual porosity mobile-immobile mass transfer, equilibrium and kinetic sorption, and first-order transformations.
• SSM (Source Screening Module) Source Screening Module for quick, conservative assessments of contaminant migration and potential impacts from soil sources through the vadose zone to groundwater receptors.
• OPR-PPR Program developed for USGS that evaluates how different data types influence predictive uncertainty and helps prioritize data collection by assessing the value of observations and other independent information.
• GENIE Model-independent parallel run manager that distributes model runs across networks using multithreaded message-passing, developed by SSP&A under USGS contract.
• Environmental Modeling and Hydrogeology Services Groundwater flow, solute-transport, variable saturation, density-dependent, and land-surface process modeling, including model development, calibration, uncertainty analysis, and decision support. For government agencies and industrial clients with water resource and contamination issues.
• Geochemistry Services Expert services in PFAS and emerging contaminants, stable and radiogenic isotopes, geochemical statistics, organic and inorganic contaminants, Monitored Natural Attenuation (MNA), and reactive transport modeling. For government and industrial clients managing contamination.
• Engineering and Remediation Services Site assessments, remedial strategy development, remediation system design (pump and treat, air sparging, SVE, biosparging), brownfields redevelopment, and regulatory compliance. For industrial clients and government agencies with contaminated sites.
• Geophysical Investigations and Analysis Geophysical data collection, modeling, analysis, and interpretation including electrical resistivity, seismic refraction, MASW, and integration with groundwater models. For water resource and environmental remediation projects.
• Data Management and Analysis Services Database management, GIS implementation and design, map creation, time-series and spatial data analysis, web tools, and data integration and visualization, including ML/LLM-based analytics. For clients managing large environmental datasets.
• Client-Specific Specialized Field Services On-site environmental, hydrogeologic, and geophysical services including sampling, monitoring, well installation, remediation oversight, and well-fouling abatement (Well-DOC). For industrial and government sites with field data collection needs.
• Expert Witness and Litigation Support Unbiased, independent, fact-based technical expert services for legal matters related to groundwater, surface water, geochemistry, and soil remediation projects, including expert testimony, deposition responses, technical reports, and litigation support. For plaintiff and defense counsel, courts, and government attorneys.

Quantifiable outcome

• MT3D became the most widely used solute transport code in the world for simulation of contaminant transport in groundwater.
• +3 more outcomes

Named customers18 records

Segments5 records

Ideal customer profiles3 records

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Integration16 records

AI capability6 records

Feature10 records

Partnerships

Nine partnerships are on record, tiered core and minor.

• California Department of Water Resources (CA-DWR)coreStrategic or Co-development Partner · 1 January 2013Co-developed Texture2Par with CA-DWR to integrate sediment texture data for aquifer parameter estimation in IWFM and MODFLOW models. Collaborated with Dr. Can Dogrul (CA-DWR) in development of delayed subsidence in IWFM. Texture2Par and Data2Texture developed on behalf of CA-DWR.
• Dr. John DohertycoreStrategic or Co-development Partner · 1 January 2012Collaboration with developer of PEST on software development. Co-developed PEST.cloud web-based cloud tool for model calibration using PEST on Microsoft Azure. Collaborated on PEST/PEST++ development and course materials.
• U.S. Geological Survey (USGS)coreTechnology or Integration · 1 January 1990Long-standing collaboration with USGS on software development. MT3D developed at SSP&A released in 1990, with most recent version MT3D-USGS released in collaboration with USGS. SSP&A serves as prime contractor and co-developer of PEST++ under USGS contract. OPR-PPR program developed for USGS. SSP&A is part of core development team for MODFLOW 6.
• U.S. Department of Energy (USDOE)coreStrategic or Co-development PartnerContinuous software development and enhancement through USDOE contracts. Contaminant Treatment System (CTS) package originally developed at SSP&A on behalf of USDOE. Hanford Site projects with USDOE.
• U.S. Environmental Protection Agency (USEPA)coreStrategic or Co-development PartnerContinuous software improvements through USEPA contracts. EPA Region 5 awarded 5-year, $10 million contract for groundwater technical support. Collaborated on software development and professional courses.
• U.S. Army Corps of Engineers (USACE)minorStrategic or Co-development PartnerSoftware development and improvements through USACE contracts.
• University of WaterloominorStrategic or Co-development PartnerCollaborated with University of Waterloo to add sub-grid analytical transport capabilities to mod-PATH3DU.
• Dr. Chunmiao ZhengcoreStrategic or Co-development PartnerMT3D developed at SSP&A by Dr. Chunmiao Zheng in 1990, becoming the most widely used contaminant transport simulator worldwide. Co-authored Applied Contaminant Transport Modeling textbook with Gordon Bennett.
• Dr. Weixing Guo and Gordon BennettcoreStrategic or Co-development PartnerDeveloped SEAWAT program for variable density fluid simulation while at SSP&A, later incorporated into MODFLOW family of codes by USGS.

Scale indicators6 records

Recent moves10 records

Expansion highlights6 records

Broad incumbents

• Golder Associates (now part of WSP): Earth and environmental consulting firm (now under WSP) with strong groundwater and contaminated site practices. Comparable to SSP&A in hydrogeology and modeling but with broader geotechnical, mining, and infrastructure footprint.
• Environmental Resources Management (ERM): Global environmental, health, safety, and sustainability consultancy. Competes with SSP&A on large environmental site assessments, PFAS, and remediation, but operates at much larger scale with broader sustainability and EHS offerings.
• SLR Consulting: Global environmental and advisory consultancy with a strong water and contaminated land practice. Comparable to SSP&A on environmental site investigation, remediation, and PFAS work, but with broader EHS, climate, and advisory services.
• Wood Environment & Infrastructure (now part of WSP): Environmental and infrastructure consulting business, now integrated into WSP, with groundwater and remediation capabilities. Comparable on federal environmental contracts but offers a much broader environmental and engineering portfolio.
• Tetra Tech: Large global consulting and engineering firm with a substantial environmental and water resources practice. Overlaps with SSP&A in groundwater modeling, remediation design, and federal environmental contracts, but serves a much broader portfolio across civil, environmental, and international development work.
• Arcadis: Global design and consultancy firm with a significant water and environmental remediation practice. Overlaps with SSP&A on groundwater, PFAS, and federal remediation work but operates at much larger scale across broader infrastructure, mobility, and resilience segments.

Direct peers

• Daniel B. Stephens & Associates (DBS&A): Groundwater and environmental consulting firm specializing in hydrogeology, water resource evaluation, and contaminant transport. Closely comparable to SSP&A in size, technical focus on modeling, and federal/industrial client mix, particularly for mining and nuclear-related work.
• Geosyntec Consultants: Environmental consulting firm with deep expertise in groundwater modeling, contaminant fate-and-transport, and remediation design. Directly comparable to SSP&A in technical specialty, federal/state client base, and litigation/expert witness support, particularly for complex hydrogeology and PFAS matters.
• Haley & Aldrich: Environmental and geotechnical engineering consultancy with a strong groundwater and contaminated site practice. Comparable to SSP&A in serving federal, industrial, and legal clients on hydrogeology and remediation matters, though with a heavier tilt to geotechnical/foundation engineering.
• INTERA Incorporated: Specialty groundwater and environmental consulting firm with strong modeling capabilities and a focus on radioactive waste, environmental remediation, and water resource evaluations. Highly comparable to SSP&A in technical depth, federal agency clients, and MODFLOW/MT3D-based modeling expertise.

Market position

Strengths5 records

Weaknesses4 records

Competitive moat7 records

Key highlights7 records

Customer concentration

Revenue estimate

Valuation estimate

Number of profiles

Profiles15 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

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Frequently asked questions about S.S. Papadopulos & Associates, Inc.