Federal approach to contaminated sites: statement of work for risk assessment


This Statement of Work (SOW) has been developed by [Name of organization] to solicit consulting services for a Human Health and/or Ecological Risk Assessment at suspect contaminated sites.

Site Information

This SOW applies to a Human Health and/or Ecological Risk Assessment to be conducted at [location]. [This section is to be filled out by the Project Manager and should include general information pertaining to the sites being examined. For example, it should include information on known suspected areas of contamination, the types of contaminants that the contractor can be expected to find, key problem areas, etc. This information should be general and will vary in content depending on the number of sites.]


The Human Health and/or Ecological Risk Assessment includes an assessment of the risks posed by soil, groundwater, sediment and surface water contamination on human or ecological receptors. It may be carried out concurrently with either the Initial Testing Program or the Detailed Testing Program if it is established early in the contaminated site management process that Risk Assessment is warranted. The objectives of the Human Health and/or Ecological Risk Assessment are:


The following references are listed as guidance documents. This is not an all-inclusive list; therefore, the contractor shall ensure that all applicable references are used. Should more current versions become available during the life of the contract, they shall take precedence and be referred to in subsequent work/reports. With the exception of [project manager's organization] policy documents and previous assessments completed for the property listed herein, copies of other references will not be made available.

  1. [Project Manager's organization] policy documents [if any];
  2. [Previous assessment reports such as Historical Review report, Initial and Detailed Testing Program reports if available, environmental impact assessments, environmental baseline studies, well drilling and geotechnical reports that are available from the project manager's organization, if any];
  3. Guidance Document on the Management of Contaminated Sites in Canada, Section CCME, April 1997;
  4. A Framework for Ecological Risk Assessment: Technical Appendices. CCME, March 1997;
  5. A Protocol for the Derivation of Environmental and Human Health Soil Quality Guidelines. CCME, March 1996;
  6. Guidance Manual for Developing Site-Specific Soil Quality Remediation Objectives for Contaminated Sites. CCME, March 1996;
  7. A Framework for Ecological Risk Assessment: General Guidance. CCME, March 1996;
  8. A Framework for Ecological Risk Assessment at Contaminated sites in Canada: Review and Recommendations. Environment Canada, 1994;
  9. Framework for Ecological Risk Assessment. United States Environmental Protection Agency (U.S. EPA), 1992;
  10. CCME Environmental Quality Guidelines 1999; and
  11. Risk Assessment Guidance for Superfund - Volume 1: Human Health Evaluation Manual. United States Environmental Protection Agency (U.S. EPA), 1991.

Scope of Work

To meet the objectives of this mandate, contractors will carry out the following work, subject to site-specific environmental issues or other factors:

  1. Conduct the Risk Assessment to determine the significance of contamination at the site(s) of concern;
  2. Review the results of previous testing programs to verify that a contaminant exposure pathway exists that may present a human or ecological health concern. For each contaminant, pathway and receptor of concern the contractor shall:
    • review previous information about the site and gather the necessary data to conduct the Human Health and/or Ecological Risk Assessment;
    • conduct an exposure assessment to establish the complexity of the Risk Assessment, appropriate exposure amortization, characteristics of receptors, and the bio-availability of contaminants (as appropriate). The pathways by which individuals, flora or fauna may come in contact with the contaminants of concern will be identified and their exposure will be quantified;
    • conduct the toxicity assessment by classifying the contaminants of concern, establishing the toxicity assessment end-points for ecological receptors, and developing exposure limits, concentration limits and/or potency factors for contaminants of concern, as appropriate; and
    • conduct the risk characterization using equations appropriate to the contaminants of concern, provide a sample calculation of the results, and conduct an evaluation/interpretation of the risk estimates.
  3. Based on the results of the previous investigations and the Risk Assessment, the contractor shall indicate the following:
    • if a human health risk exists at the site (i.e. Numerical Cancer Risk estimate is greater than 1 x 10-6);
    • if an ecological risk exists at the site based on discussions with regulatory agencies (i.e. Hazard Index is greater than 1);
    • whether the risks can be mitigated through the implementation of a risk management strategy;
    • whether the site will self-remediate over the long term through natural processes such as bioremediation;
    • whether site remediation is required; and
    • whether completion of remediation project is justified, and why.
  4. After approval of the work plan by the Project Manager, complete the Risk Assessment process. Prepare a report, making recommendations regarding the action required at the site. If no unacceptable risk is found and there is evidence that the contaminants are naturally degrading, the contractor should indicate that no further work is required. The contractor shall also provide a rationale for the conclusions made in the Risk Assessment.
  5. The work undertaken during the Risk Assessment shall be aimed at:
    • meeting the requirements laid out in the present Statement of Work by taking a logical, structured and cost-effective approach;
    • conducting a review of pertinent documentation related to the site to avoid repetition. The contractor shall also conduct an inspection of the site, noting any changes since the time of the earlier reports. The information gathered should be used to develop an understanding of the potential risks to human and ecological health, based on the types of contaminants, hydrogeological and topographical information, soil characteristics, habitat, habitat adjoining the property, and the current and proposed future land use of the site;
    • conducting an Exposure Assessment of the site(s). This involves determining the concentrations of contaminants in the appropriate environmental media in terms of either a point estimate (e.g. mean, 95th percentile, maximum) or a probability distribution function if a probabilistic approach has been chosen. The contractor shall amortize the exposure to the scenarios under investigation and characterize the receptors concerning the exposure factors. Several steps in the Exposure Assessment will involve discussions with appropriate [Name of organization] personnel and regulatory officials to establish acceptable parameters for the assessment;
    • conducting a Toxicity Assessment of the site(s). For human health risk assessments, this involves classifying each of the contaminants of concern with regard to their potential toxicity or carcinogenicity. For ecological risk assessments, the contractor will propose appropriate assessment end-points for the site, for discussion with the [Name of organization] Project Manager and appropriate regulatory officials. The contractor shall identify Toxicity Reference Values or Concentration Limits for human health assessments or derive limits using standard protocols if appropriate regulatory limits are not available. In the case of ecological assessments, the contractor shall identify or develop appropriate Toxicity Reference Values or Concentration Limits based on receptors of concern; and
    • determining the risks associated with exposure to contaminants on the site for both ecological and human receptors as appropriate. Risks will be calculated as Hazard Quotients or Indices, Numerical Cancer Risk Estimates, or Exposure Ratios. The contractor shall evaluate and interpret the risk estimates and provide sources of uncertainty in the Risk Assessment process. The contractor shall also provide a sample calculation of risk estimates for both a threshold and non-threshold response contaminant.
  6. The report shall outline the procedures, rationales and assumptions made during the assessment, and will clearly state the combinations of contaminants, receptors and pathways that may constitute a health risk. A Conceptual Model of the contaminant source, release mechanism, transportation and fate mechanisms, exposure media, exposure route and receptors will be included in the report for the contaminants that present an unacceptable health risk. The contractor shall make recommendations with regard to the action that should be taken at the site. If multiple sites present unacceptable health risks, the contractor shall prioritize the sites based on their associated risks. If it is determined that the site does not present an unacceptable health risk, the contractor shall recommend, with an appropriate rationale, to cease action at the site.

Special Requirements

  1. All new and existing site layout plans included in the report shall be provided in electronic data form (AutoCad 14 [or format specified by the Project Manager]). Final reports shall be submitted in hard copy ([number of copies to be specified by Project Manager]) and electronic form (WordPerfect and/or Microsoft Word formats), including electronic data copies of all tables and other data as specified by the Project Manager. Information, data, drawings, etc., gathered as part of the project shall be made available only to [name of organization] unless otherwise approved in writing by a representative of [name of organization]. The information, data, drawings, etc., provided will be used by the [name of organization] as it sees fit.
  2. Refer any queries about the project from the public, news media or others to the Project Manager.
  3. The Project Manager shall be notified immediately of conditions that pose an imminent threat to human health and the environment.
  4. Analysis of data will be in relation to agreed CCME guidelines or other guidelines identified by the Project Manager.

General Requirements

  1. The Project Manager shall be a person from [Name of organization] or a designated alternate.
  2. Work

    The contractor will be responsible for providing the people and resources to fulfil the terms of this Statement of Work, including the qualified personnel, office space, reference documents, laboratory and data-processing supplies, and machinery and equipment to:

    1. conduct the Human Health and/or Ecological Risk Assessment; and
    2. submit required reports and deliverables.
  3. Liabilities
    1. The contractor shall assume responsibility for any accident or damage caused by its employees or equipment to [Name of organization] property or personnel as a result of the contractor's activities.
    2. The contractor shall assume responsibility for the security of its equipment and materials during and after working hours. [Name of organization] shall not be liable for any vandalism, theft or loss.
  4. Notifications/Permits

    The contractor shall be responsible for making whatever representations are necessary to the pertinent organizations in order to carry out the work required to fulfil the terms of this SOW. The costs incurred in obtaining these documents shall be borne by the contractor.

  5. Progress Reporting and Meetings
    1. Progress Reports. Written progress reports in the form of 1- to 4-page faxes shall be provided to the Project Manager for periods determined by the Project Manager. The progress reports shall include a synopsis of work completed during the latest report period and the projected work plan for the following period. The contractor shall be prepared to meet with the Project Manager and to discuss any matter concerning the progress and findings of the site investigation.
    2. Meetings. The contractor shall attend meetings as requested by the Project Manager. Personnel in attendance shall include the contractor's project manager and representative(s) familiar with all technical aspects of the project. The contractor shall prepare minutes of the meetings and send the draft minutes to the [Name of organization] Project Manager for review and approval prior to their dissemination for action. At the discretion of the Project Manager, the contractor may be required to maintain an action item list.
  6. Quality Assurance and Quality Control

    The contractor is expected to identify and adhere to acceptable quality assurance and quality control (QA/QC) procedures throughout the project. QA/QC measures shall be explicitly identified in the contractor's work plans and project reports.

  7. Health and Safety Program

    A detailed health and safety plan (HASP) shall be maintained on site at all times. Adherence to the health and safety measures specified in that plan shall be mandatory for all on-site personnel and all site visitors.

  8. Responsibilities and Communication

    All formal communication (e.g. letters of direction, approvals, etc.) will be between the Project Manager and the contractor.

Bidders' Conference and Proposals

  1. Bidders' Conference

    A bidders' conference will be held at [location] on [date, time] to communicate the requirements of the contract and address any concerns of the interested contractors. At the conference, contractors will be given access to the following information:

    1. [Name of organization] policy documents;
    2. available site drawings; and
    3. previous reports such as Environmental Baseline Studies (EBS) and environmental assessment or audit reports for the property.

    [Where possible, the Project Manager will make hard copies of the relevant information or provide the contractors with the information on computer disc. For information that will not be copied (i.e. baseline studies), a schedule will be developed to permit contractors to view these documents].

  2. Letter of Interest

    Contractors wishing to bid on the work shall submit a Letter of Interest to the Project Manager at [location] on or before [date - a minimum of 2 weeks should be given to the contractors to review the pertinent information]. The letter is to provide a condensed version of the technical and management information requested in the full proposal (next section), and an overall cost estimate. The letter shall not be more than six (6) pages in length (3 leaves, double-sided) on 8½" x 11" paper, and the text shall be written in 12 point font. Only the first six pages will be reviewed and scored. The letter will be used to evaluate and select the contractor to carry out the work. If additional information is required prior to making a selection, the four (4) contractors with the highest score will be invited to submit full proposals.

    It is recognized that industry spends a great deal of time, effort and money to develop proposals. By taking this approach, [Name of organization] assures technical credibility and cost effectiveness without asking every contractor to expend time, money and resources to produce full proposals.

  3. Full Proposal [if required]

    [Time period - 3 weeks is suggested] following the bidders' conference, four (4) contractors will be notified of their eligibility to submit their full proposals to [specified address] on or before [date/time]. The proposal is to be submitted in [number] copies outlining the approach to the Risk Assessment, the technologies that will be used, a proposed work schedule, and a detailed cost estimate for the work. The proposal should display a logical, cost-effective approach and include the necessary information to address the evaluation criteria.

Evaluation Criteria

  1. General

    Both the Letter of Interest and full proposal will be evaluated and scored in accordance with the following criteria. Contractors must cover each criterion. Proposals should expand on requirements stated in the SOW and describe how the contractor plans on meeting the work requirement.

Item Criteria Weight
1. Understanding of Scope, Objectives and Possible Problems 15
2. Approach and Methodology 35
3. Level of Effort 20
4. Managerial Experience 30
Total Empty 100
  1. Technical Proposal
    1. Understanding of Scope, Objectives and Possible Problems. The bidder should demonstrate a comprehensive understanding of the project's scope and objectives. As well, the contractor must demonstrate that direct and peripheral problems have been anticipated. Proposed solutions to anticipated problems must be presented.
    2. Approach and Methodology. The proposed approach and methodology should follow an efficient and logical sequence that will fulfil the requirements of the Statement of Work. The proposal should explain how sample results will be obtained and analyzed, how quality assurance and quality control will be maintained, and how the health and safety requirements will be met. The contractor should demonstrate its ability to competently evaluate the results and provide meaningful recommendations. A work schedule should show that the project milestones and objectives, both technical and administrative, will be met.
    3. Level of Effort. The contractor should show that a sufficient level of effort will be applied to address the technical requirements of the project in an efficient and cost-effective manner. Proposals will be evaluated on their value-for-money, where value is interpreted as the quality and quantity of work to be done in direct support of the project. Full proposals shall include a breakdown of anticipated work by task and quantity, including:
      • management and supervision;
      • analysis; and
      • disbursements.
  2. Management Proposal

    Managerial Experience. The contractor should demonstrate that its organization, including partners and subcontractors, has the necessary technical and managerial background and experience. Include the background, experience, geographic proximity to the project site and level of involvement by task for each key individual. The contractor should also demonstrate technical background and experience by citing projects of comparable scope and nature that show successful and timely completion (include client references and their points of contact). Indicate other tasks the key individuals may have during the project. The backup for key personnel should be named.

  3. Contractor Selection

    Selection. Selection of the contractor may take place based on the information provided in the Letter of Interest, or, depending on the complexity of the project, it may be necessary to ask contractors to submit their full proposals.

    Letter of Interest (LOI). The bidder selected for contract award or invited to submit a full proposal will be the contractor that:

    1. addresses each evaluation criterion in sufficient depth to allow proper evaluation;
    2. obtains a proposal evaluation score of 75% or higher in each category;
    3. meets all the mandatory requirements set out in the Request for Proposal; and
    4. obtains the highest final score on 100, which includes both the technical proposal and cost. The technical proposal score obtained following the evaluation will be recalculated in relation to a maximum of 90. The lowest budgetary price gets a score of 10, with the next lowest getting 8, 6, 4, 2 and 0. Contractors should be prepared to commit to the budgetary price.

    Full Proposal. If full proposals are requested, the four (4) highest scoring bidders will be asked to submit full proposals. Where more than four (4) LOIs score above 75% and where the scores are tightly grouped, up to six (6) bidders will be invited to submit full proposals. The successful contractor will be the one meeting the technical requirements specified in the previous paragraph and obtaining the highest score on 100, including both the technical proposal score and the cost score within the proper budget ceiling of $ [insert average budget price].

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