Drainage Features
Scope Tip
Good trail drainage begins with trail alignment, grade, and tread shape. Drainage features are used where specific site conditions or concentrated water require additional measures, such as culverts, drainage crossings, ditches or swales, or subsurface drainage.
Scope Item Definition
Construct specific drainage features used to manage surface or subsurface water affecting the trail.
Drainage features may be needed where water is concentrated, crosses the trail, emerges from surrounding terrain, or cannot be adequately managed through trail alignment, grade, and tread shape alone. Depending on site conditions and trail construction, features may include culverts, drainage crossings, ditches or swales, subsurface drains, and other site-specific drainage features.
Drainage features are often integrated with trail tread construction, tread hardening and surfacing, trail structures, and site restoration and may be included within the overall trail construction price or separately defined and priced.
When / Where It Applies
Drainage features may be needed where surface or subsurface water intersects or affects the trail, where the trail crosses an existing drainage, or where trail construction alters existing drainage patterns.
They may also be needed in association with raised tread, bermed turns, trail structures, hardened areas, or other construction where water needs to be collected, conveyed, redirected, or dispersed.
The need, type, and location of drainage features may be established through the planning and design process or refined in the field based on actual site and drainage conditions.
Scope Considerations
Depending on the project, the scope should consider and clearly define:
Known or anticipated drainage conditions, including concentrated flow, seeps, springs, seasonal water, and other surface or subsurface water.
Location, type, dimensions, materials, and anticipated quantities of drainage features where known.
Performance requirements where specific drainage features or construction details are not prescribed.
Requirements for culverts, drainage crossings, ditches or swales, subsurface drainage, and other applicable features.
Sequencing and integration of drainage features with trail tread construction, including raised tread and bermed turns, tread hardening and surfacing, structures, and other construction.
Excavation, bedding, backfill, compaction, rockwork, stabilization, and restoration associated with drainage construction.
Management of excavated material and spoil.
Construction methods, access, equipment restrictions, and other constraints that may affect the work.
Permit, BMP, resource-protection, and seasonal requirements associated with drainage construction.
Where drainage locations or details may be adjusted based on field conditions and when owner or designer approval is required.
Whether drainage features are included in the trail tread construction price or separately quantified and priced.
Owner-Provided Information
The owner should provide the following, if available and applicable:
Approved planning and design documents, including the trail corridor and/or alignment, maps, GIS data, plans, drawings, and field markings.
Known drainage locations and existing surface or subsurface water conditions.
Locations, types, anticipated quantities, and specifications for drainage features identified during planning or design.
Applicable construction drawings, details, material specifications, and performance requirements.
Known soil, rock, groundwater, or other site conditions that may affect drainage construction.
Information about existing drainage features or infrastructure that the new trail construction may intersect or affect.
Applicable permits, environmental approvals, mitigation measures, BMPs, resource-protection requirements, and seasonal or timing restrictions.
Access routes, equipment restrictions, staging areas, and material-storage limitations.
Available site photographs, videos, surveys, or other documentation of existing conditions.
Construction Specifications + Field Decision-Making
The solicitation should clearly identify which drainage features and construction details are established through the planning and design process and which may be determined or adjusted during construction.
Where field adjustments are allowed, the scope should define the applicable parameters, including performance requirements, materials, permit requirements, and other project constraints, and identify when owner or designer approval is required.
Because drainage conditions may not be fully known before construction, the contract should also establish how previously unidentified water sources or substantially different drainage conditions will be addressed.
Completed Work / Deliverables
Depending on the scope, completed work may include:
Drainage features constructed or installed at required or approved locations and to applicable specifications.
Drainage features appropriately integrated with the trail tread, surrounding terrain, and other construction elements.
Associated excavation, bedding, backfill, compaction, stabilization, and restoration completed as required.
Water conveyed, redirected, or dispersed without creating unintended erosion, instability, or damage to the trail or surrounding area.
Excavated materials and spoil appropriately managed.
Disturbed areas stabilized and adjacent resources protected.
Quality Assurance + Acceptance
The solicitation should define how completed drainage features will be evaluated and accepted, including consistency with approved locations, drawings, specifications, materials, dimensions, grades, and other applicable requirements.
Acceptance should also consider whether drainage features function as intended, integrate appropriately with the trail and surrounding terrain, and avoid creating unintended erosion, ponding, concentrated flow, or other drainage problems.
Where drainage features are measured separately for payment, completed quantities should be documented and verified as specified in the contract.
Pricing & Payment Considerations
Drainage features may be included within the overall trail construction price or separately quantified and priced. Common approaches include:
Included within a trail tread unit price or overall lump-sum construction price.
Priced per drainage feature.
Priced by linear foot or other applicable unit.
Priced using different unit rates for defined feature types, sizes, materials, or construction conditions.
Priced by crew or contractor day rate where work is difficult to quantify and appropriate oversight or contractor trust is established.
Priced on a time-and-materials basis where conditions or quantities cannot reasonably be determined in advance.
Where drainage features are separately priced, the solicitation should clearly define what is included in each unit price, including associated excavation, materials, installation, backfill, compaction, stabilization, and restoration as applicable.
Where drainage needs or quantities cannot be fully determined in advance, unit pricing or another agreed method for pricing additional work can provide a clear basis for addressing conditions encountered during construction.
Common Scope & Contracting Issues
Treating drainage features as a substitute for appropriate trail alignment, grade, and tread shape.
Not identifying known drainage conditions or water sources that may affect construction.
Not adequately defining the location, type, dimensions, materials, quantities, or performance requirements for drainage features.
Not defining when drainage locations or details may be adjusted in the field and when owner or designer approval is required.
Not clearly defining whether drainage features and associated work are included in the trail tread price or separately priced.
Failing to account for drainage needs associated with raised tread, bermed turns, structures, hardened areas, or other construction that may alter drainage patterns.
Not clearly communicating permit requirements, BMPs, seasonal restrictions, or resource-protection requirements.
Not establishing how previously unidentified water sources or substantially different drainage conditions will be addressed and priced.
Constructing drainage features without adequately considering where water will go after it leaves or passes through the feature.