Drainage capital planning should connect grading, pavement, inlets, piping, storage, outfalls, maintenance, weather history, public interfaces, construction phasing, and the money required to finish the complete water path.

Start with the property decision—not the puddle

Define the concern and the consequence. Water may pond in parking stalls, enter a building, overtop a curb, freeze along an accessible route, erode a slope, surcharge a structure, undermine pavement, overwhelm a pump, discharge across another parcel, or leave a detention or green-infrastructure practice unable to perform. Identify the affected buildings, drives, loading areas, parking, walks, ramps, yards, landscaped areas and neighbors; the frequency and duration of the event; the weather conditions that trigger it; the operating impact; and whether the decision supports acquisition, refinancing, a reserve plan, an active repair, redevelopment, or completion of sitework under a construction loan.

For lenders and equity partners, connect the physical problem with the funded project. Separate incomplete contract work, a design or construction deficiency, maintenance, damage, changed site conditions, public-utility delay, tenant or owner scope, and a future capital improvement. Reconcile the approved sitework and paving budgets, allowances, retainage, change exposure, responsible contracts, insurance or warranty positions, outstanding public improvements, remaining loan and equity, contingency, schedule, and the cost and access required to reach an accepted condition. A newly paved surface does not resolve completion exposure if the water still has no reliable path out of the property.

Map runoff from the high point to the final discharge

Create a current drainage plan from survey, topography, spot elevations, slopes, surface types, curbs, walls, islands, swales, roof leaders, trench and area drains, catch basins, manholes, pipes, culverts, underdrains, cleanouts, pumps, backflow or tide controls, infiltration, bioretention, permeable pavement, detention or retention, flow-control structures, emergency overflow, discharge points, receiving systems and downstream restrictions. Mark contributing drainage areas and surface changes, low points, building openings, accessible routes, utility conflicts, snow-storage areas, sediment sources, traffic loads, and the path water follows when the intended system is blocked or exceeded.

Reconcile the physical system with civil drawings, stormwater reports, permits, maintenance agreements, easements, as-builts, public-agency records, CCTV or cleaning records, prior repairs, utility maps, property boundaries, tenant obligations, and interviews. Identify which components are public, private, shared, temporary, undocumented, abandoned, inaccessible, or dependent on another owner or authority. FHWA’s HEC-22 provides a detailed framework for urban drainage analysis and inlet, gutter, storm-drain and storage design; UFGS 33 40 00 provides construction and field-quality requirements for stormwater utilities. They are technical references, not substitutes for the locally applicable criteria, permit, professional design, or verified property configuration.

Build a condition and performance baseline

Assemble dated rain, flood and maintenance history: incident photos and video, rainfall and recurrence information, ponding extent and drawdown time, water entry, pump or alarm events, tenant complaints, closures, icing, erosion, sediment and debris, backups, insurance claims, emergency work, utility response, cleaning frequency, and whether symptoms changed after paving, landscaping, utility, roof, building, or adjacent-site work. Observe the site in dry conditions and, where practical and safe, during or soon after representative rainfall. One dry-weather walk cannot prove system capacity or reproduce an intermittent obstruction.

Select investigation methods around the question. Work may include survey and elevation checks, inlet and pipe inventories, cleaning and CCTV, dye or controlled-flow testing, manhole observation, pump testing, soil or infiltration evaluation, pavement cores, geotechnical review, utility locating, limited excavation, outfall confirmation, water-level monitoring, and hydrologic or hydraulic analysis by the responsible professionals. Record access, assumptions, rainfall basis, blocked or submerged components, sediment, deformation, joint or connection issues, infiltration or exfiltration, root intrusion, structural condition, pump duty, controls, power, alarms, and downstream tailwater. Distinguish an observed symptom from the tested cause and list what remains unverified.

Develop repair options around the complete water path

Compare maintenance and cleaning; spot grading; curb, inlet or trench-drain changes; pipe lining or replacement; added collection; pump and control renewal; building-opening protection; slope and erosion repair; underdrainage; detention or flow-control work; permeable pavement, bioretention or other green infrastructure; pavement reconstruction; and larger site reconfiguration. Test each option against the contributing area, design storm and local criteria, downstream capacity, overflow route, groundwater and soil conditions, freeze and snow operations, sediment load, utility conflicts, accessibility, traffic, emergency access, pavement section, landscaping, easements, discharge rights, public approvals, maintenance, service life, failure consequence, and future development.

EPA guidance stresses that green infrastructure serving roads and parking lots requires deliberate installation, inspection, sediment and debris removal, vegetation or media care, and repair of erosion, clogging or damaged components. Do not treat a landscaped practice as a maintenance-free replacement for a pipe, or a pipe as a complete answer where grading and overflow remain wrong. Define who will design, permit, inspect, own and maintain each option; what temporary and enabling work it requires; which parts are allowance-based; what conditions trigger a larger scope; and how the selected work will be measured, priced, accepted, and placed into the property’s maintenance and capital records.

Phase construction around water, traffic, and occupied operations

Sequence survey and investigation, authority and utility coordination, design, permitting, erosion and sediment controls, temporary drainage, traffic and pedestrian routing, utility locating, clearing or demolition, excavation and shoring, dewatering, structure and pipe work, backfill and compaction, drainage media, curbs and grading, green-infrastructure media and planting, pavement, striping, restoration, cleaning, testing, and stabilization. Identify tenant and loading schedules, emergency routes, accessible paths, parking displacement, public interfaces, noise and dust, weather windows, snow operations, contaminated soil or water, trench safety, bypass pumping, downstream protection, material storage, delivery, and the areas that must remain open.

Temporary drainage is part of the design and means-and-methods plan. State how runoff will be collected, conveyed, stored, treated or discharged during each stage; how excavations and new media will be protected from sediment; how a partially connected system will respond to forecast rain; who watches pumps, controls and water levels; and what action follows a storm warning, alarm, failure, or unplanned discharge. Preserve surveys, invert and elevation checks, pipe and structure observations, compaction and material evidence, utility crossings, connections, cleanouts, concealed conditions, quantity changes, and as-built information before the pavement or landscape closes the work.

Accept drainage as a working asset and fund what remains

Define acceptance by component and system: approved materials and submittals, elevations and slopes, pipe alignment and joints, structures and connections, utility separations, backfill and compaction, pavement and accessible-route tolerances, pump and control operation, alarms and backup power where required, cleaning, visual or CCTV review, leakage or infiltration testing where applicable, basin and outlet settings, green-infrastructure installation, erosion control, restoration, record drawings, permits, public-agency sign-off, and correction and retest of deficiencies. Controlled-flow testing can verify connections and local drainage behavior; it does not reproduce every design storm or downstream condition. Plan post-construction observation and maintenance through representative weather.

Closeout should deliver the current site and drainage plan, calculations and design criteria, component and ownership register, permits and agreements, inspection and test results, cleaning and CCTV records, pump and control information, as-builts, warranties, maintenance tasks and frequencies, sediment and material disposal requirements, storm and alarm response, spare parts, seasonal work, and known limits. Reconcile final quantities, changes, allowances, contingency, incomplete and seasonal work, public improvements, retainage, warranty obligations, and remaining funds. For a lender or equity partner, the useful conclusion is not simply that paving appears complete; it is whether the connected drainage scope has been accepted, which risk remains, who owns it, and how much capital and time are still required.

Primary sources

Sources and technical references.

Source review current as of September 2, 2026.