How to Compile a Wastewater Infrastructure Design Report: A Complete Guide

In the field of environmental engineering, compiling a wastewater infrastructure design report is the culmination of a complex, multi-stage process that transforms raw data and engineering calculations into a comprehensive, defensible document . A design report is a final and comprehensive description of the water quality problem and the proposed solution, including applicable design criteria and data supporting the solution . The report must evaluate potential solutions to the defined problem and clearly demonstrate that acceptable engineering principles were used in the evaluation, that the data supports the conclusions, and that the proposed solution has reasonable expectations of solving the water quality problem .

This guide walks you through the entire compilation process, drawing from official state and federal engineering report outlines to help you produce a report that meets regulatory requirements and secures project funding .

Understanding the Purpose of a Design Report

Before compiling the report, it is essential to understand what it is meant to accomplish. Engineering reports:

1. Define the need for the project
2. Identify how the project is expected to protect or improve water quality
3. Evaluate alternative ways to solve the water quality problem
4. Recommend a technically and financially sound alternative 

The selection of a recommended alternative is supported with preliminary design considerations, such as technical standards demonstrating the alternative can solve the problem, life cycle cost estimates, and a schedule from submission through construction completion . The goal is to provide intended audiences regulatory agencies, funding agencies, and governing bodies sufficient information to make an informed decision .

Engineering Report Preparation Standards

A design report must be prepared, stamped, and signed by a qualified professional licensed to practice in the relevant jurisdiction and developed in accordance with the latest editions of applicable standards . These typically include:

1. Recommended Standards for Wastewater Facilities (Ten States Standards)
2. Recommended Standards for Water Works
3. TR-16 Guides for the Design of Wastewater Treatment Works
4. State-specific Stormwater Management Design Manuals
5. State-specific Design Standards for Wastewater Treatment Systems
6. Flood Risk Management Guidance 

In instances where the design engineer proposes a deviation from these standards, the report must clearly explain and justify the deviation . In all cases, facilities must be designed to treat permitted flows and loads.

Minimum Requirements for Funding and Approval

For projects seeking funding, the engineering report must include eight essential elements:

Reports that do not include all these items may not receive funding .

Step-by-Step Guide to Compiling the Design Report

Step 1: Collect Design Data

The compilation process begins with collecting wastewater infrastructure design data . This foundational step involves gathering:

Site Information:

• Location maps showing legal and natural boundaries
• Geologic conditions (soil type, depth to bedrock and groundwater, slope)
• Environmental resources (waterbodies, aquifers, endangered species, wetlands)
• Floodplain considerations including Base Flood Elevation 

Ownership and Service Area:

• Municipality(ies) that own and maintain the infrastructure
• Areas served or to be served
• Population trends and growth (U.S. Census data for at least the past twenty years)
• Residential population served, documented or estimated from Equivalent Dwelling Units (EDUs) 

Existing Facilities:

• General description and history with process flow diagram
• Discharge permit conditions and effluent discharge limits
• Design flows and waste loads (average and peak)
• Existing flows and waste loads from the last three years
• Existing energy consumption 

Step 2: Analyze Design Data

Once data is collected, it must be analyzed to inform design decisions . This includes:

Wastewater Characterization:

• Flow Rates: Average daily flow, maximum daily flow, peak hourly flow, peak wet weather flow
• Wastewater Strength: BOD₅ and TSS in both concentration (mg/L) and mass loading (pounds/day)
• Design Factors: Peaking factors applied to average flows to calculate peak conditions

Population Projections:

• Design period (typically 20 years)
• Design equivalent population accounting for residential growth and industrial contributions 

Step 3: Calculate Design Parameters

With data analyzed, the engineer calculates the design parameters that will determine the size and capacity of the proposed infrastructure .

Treatment Process Design:

• Unit dimensions, rates and velocities, detentions
• Loadings and removal efficiencies through each unit operation
• Total removal efficiency and effluent quality
• Mass balance showing inter-relationship of units 

Collection System Design:

• Pipe sizes, grades, velocities, and capacities
• Pump station calculations including energy requirements and standby power

Hydraulic Profile:

• A “water level map” showing water elevation from influent through each treatment unit to final outfall under both minimum and maximum flow conditions 

Hydraulic Calculations:

• Darcy’s formula, Chezy’s formula, Manning’s formula, Hazen Williams formula 

Step 4: Draw Infrastructure Units

The engineer must create drawings that clearly show all proposed infrastructure . Drawings must include:

• Plan views showing layout and dimensions
• Profiles showing elevations and slopes
• Sections showing structural details
• Process flow diagrams showing treatment train

All drawings must include title, scale, north arrow, date, and professional engineer’s registration seal .

Step 5: Compile the Full Report

Now the engineer compiles all components into the complete design report following the identified format .

The Complete Report Structure

Cover Page

The cover should contain:

• A descriptive project title
• Name of the Owner/Municipality
• Applicable discharge permit number
• Name of the engineering firm
• Date of the report, including revision dates
• Professional Engineer stamp and signature 

Executive Summary

Provide a brief description of the purpose of the report, need for the project, evaluations conducted, recommended alternative, schedule, cost, and next steps .

Definition of the Problem

Succinctly define the water quality issue, considering:

• Compliance with discharge permits
• Health, sanitation, and security concerns
• Aging or inadequate infrastructure
• Infiltration and inflow issues
• Groundwater/surface water contamination
• Reasonable growth and its impact on flow rates 

Project Background and History

Site Information: Describe location, geologic conditions, environmental resources, floodplain considerations, and impacts to Environmental Justice Areas .

Ownership and Service Area: Describe ownership, areas served, outside users, population trends, and residential population served .

Existing Facilities: Provide overview with process flow diagram, permit conditions, compliance issues, design flows, existing flows and waste loads, energy consumption, and photographs .

Alternatives Analysis

Present a systematic comparison of feasible solutions including:

• Schematic diagrams of each alternative
• Preliminary design for cost estimates
• Total project costs dated and keyed to construction cost indices
• Advantages and disadvantages
• Process effluent characteristics
• Environmental assessment
• Operation and maintenance expenses 

Non-monetary factors:

• Operability: Ease of operation and maintenance
• Reliability: Proven process to meet permit limits
• Flexibility: Capability to handle variations
• Environmental Effects: Odor, noise, visual impacts
• Expandability: Area available for future expansion 

Summary and Comparison of Alternatives

Present a clear comparison using a matrix format that allows decision-makers to understand the relative merits of each option .

Recommended Alternative

With the problem defined and alternatives evaluated, present the recommended solution with:

• A fully developed description of the proposed project
• Basis of design
• Facility layout plan and flow schematic
• Detailed description of treatment process
• Pumping station specifications
• Collection system layout
• Hydraulic calculations
• Implementation schedule 

Maps and Figures

Include or attach:

• Location maps on a regional map
• Service area maps
• Proposed facility layout plans
• Process flow diagrams
• Hydraulic profiles

Appendices

Appendix A: Energy Efficiency Best Practices

• Document energy conservation measures
• NYSERDA Summary of Baseline Standard Practices
• Payback period calculations 

Appendix B: Short-Lived Assets

• Equipment expected to require replacement before loan end
• Time frames: 0-5 years, 5-10 years, 10-15 years 

Appendix C: Engineering Report Certification

• Statement that the engineer studied and evaluated cost and effectiveness of processes, materials, and technologies 

Appendix D: Additional Considerations

• Guidance on specific technologies and project types
• Collection/conveyance systems
• Treatment plant components
• Special considerations (odor, corrosion, noise, energy, safety, aesthetics) 

Appendix E: Permit Application Forms

• SPDES Permit Application Supplemental Information Form 

Special Considerations for Different Project Types

Industrial Wastewater Facilities

The report must include:

• Type of industry and kind and quantity of finished product
• Quantity and quality of process wastewater, domestic wastewater, and noncontact cooling water
• Amount and kind of chemicals used
• Basic design data and sizing calculations
• Discussion of site suitability
• Description of treatment process with flow diagram
• Provisions for bypass and spill control
• Detailed outfall analysis
• Statement that effluent will meet permit limitations 

Land Application Projects

For land application projects, the report shall include:

• Depth to groundwater and groundwater movement
• Water balance analysis of the discharge area
• Effects upon groundwater
• Soils and their permeability
• Availability of public sewers
• Reserve areas for additional subsurface disposal 

Collection System Projects

For collection system projects, address:

• Description of service area
• Inventory and map of proposed additions
• Initial and projected loadings
• Isolation from water supply wells
• Unusual construction problems
• Basement flooding prevention 

Best Practices for Compilation

Currency and Timeliness

Engineering reports must be current. Reports more than four years old are likely to require revisions . The EFC requires previously submitted reports to be rewritten to be consistent with the current Engineering Report Outline .

Coordination with Stakeholders

During the entire study period, the team shall work in close coordination with local authorities and stakeholders. The report should document:

• Understanding of project features by service providers
• Commitment by local authorities to participate and contribute
• Commitment to provide required land for project facilities
• General attitude of users toward implementation 

Review Process

Allocate sufficient time for review, comment, comment resolution, and approval . The review process involves multiple agencies and stakeholders, and the report must address all comments before receiving final approval.

Report Organization

The final report should be clear, concise, and well-organized . It should include a Table of Contents with page numbers, and all supporting documentation should be included in appendices .

Conclusion: A Framework for Success

Compiling a wastewater infrastructure design report is a structured process that follows a proven framework for ensuring critical water infrastructure projects are designed with clarity, accountability, and long-term sustainability. The objective is to present the technical and nontechnical issues that are most commonly addressed in the planning and design reports for wastewater treatment facilities .

By following this step-by-step guide from collecting data to drawing infrastructure units to compiling the complete report engineers provide a clear, defensible, and comprehensive plan that protects public health and the environment for generations. Whether you’re a consulting engineer preparing your first design report or a reviewer evaluating submitted documentation, understanding and following the compilation process is essential for successful project delivery and regulatory approval.