ADR Enterprises -- Drainage & Storm Water Division
Residential Drainage Assessment Report
Heavy Rainfall Impact Analysis & Improvement Recommendations
Following recent heavy rainfall events in the Spokane and Inland Northwest region, our team conducted on-site assessments of residential properties exhibiting signs of water accumulation and drainage failure. This report identifies common problem areas observed, provides detailed recommendations for drainage improvements, and outlines sustainable maintenance practices to prevent future water pooling and property damage.
Report Contents
Water Accumulation Problem Areas
Our assessment identified five primary areas where water accumulation poses immediate or long-term risk to the property. Each area is rated by severity to help prioritize improvements.
Foundation Perimeter Pooling
Standing water observed within 3 feet of the home's foundation walls, particularly along the north and east sides. Soil appears saturated with visible signs of backflow toward basement window wells.
Associated Risks
- Foundation cracking and hydrostatic pressure
- Basement flooding and moisture intrusion
- Mold growth in below-grade living spaces
- Soil settlement causing structural shifting
Low-Lying Yard Depressions
Multiple depressions in the rear yard act as collection basins during rainfall events. Water remains pooled 24-48 hours after storms, creating soggy conditions that prevent normal use of the yard.
Associated Risks
- Root rot in surrounding landscape plants
- Mosquito breeding habitat
- Soil erosion widening existing depressions
- Damage to lawn and turf health
Driveway & Walkway Runoff
Impervious surfaces (driveway, patios, walkways) are directing storm water toward the garage foundation and entry areas rather than toward designated drainage paths or the street.
Associated Risks
- Garage slab moisture damage
- Ice formation on walkways in winter
- Accelerated concrete deterioration
- Erosion along driveway edges
Downspout Discharge Zones
Gutter downspouts discharge directly at the foundation base with no extension or redirection. During heavy rain events, concentrated water flow was observed eroding soil and saturating the foundation backfill.
Associated Risks
- Concentrated foundation moisture loading
- Soil washout exposing foundation walls
- Basement water infiltration at seams
- Frost heave damage in winter months
Neighbor Grading Conflicts
Adjacent property grading directs some surface runoff toward the subject property along the western property line, contributing to saturation in the side yard during extended rain events.
Associated Risks
- Cumulative saturation from off-site water
- Difficulty maintaining landscape plantings
- Potential for worsening over time with soil compaction
Improvement Recommendations
The following recommendations are organized by category and prioritized by urgency. All solutions emphasize sustainability, cost-effectiveness, and long-term performance appropriate for the Inland Northwest climate.
Drainage Improvements
French Drain System Installation
Install a perimeter French drain along the north and east foundation walls extending to a daylight outlet or dry well at the lowest yard elevation. This subsurface drainage system will intercept groundwater before it reaches the foundation. Recommended depth: 18-24 inches below grade with 4-inch perforated PVC pipe in a gravel bed wrapped in filter fabric.
Catch Basin Network
Install two catch basins in the rear yard low spots connected by underground solid-wall pipe to a pop-up emitter at the property's natural drainage point. This captures surface water from depressions and actively routes it off the property before pooling occurs.
Downspout Extension & Redirection
Extend all gutter downspouts a minimum of 6 feet from the foundation using buried solid-wall pipe terminating at pop-up emitters. This is a high-impact, lower-cost improvement that eliminates the most concentrated water source at the foundation.
Channel Drain Along Driveway
Install a linear channel drain across the driveway at the garage threshold to intercept surface runoff before it reaches the garage slab. Connect to the underground drainage system.
Grading & Earthwork
Foundation Perimeter Re-Grading
Re-grade soil around the entire foundation perimeter to achieve a minimum 6-inch drop over the first 10 feet from the foundation wall. Use compacted clay-rich fill to create a positive slope that sheds water away from the structure.
Rear Yard Depression Fill & Grading
Fill and re-grade the low-lying depressions in the rear yard to create a consistent slope toward the new catch basin locations. Use a mix of structural fill and topsoil to ensure proper compaction and support for turf regrowth.
Swale Construction Along Property Line
Construct a shallow grass-lined swale along the western property line to intercept neighbor runoff and redirect it toward the street or a designated discharge area. This is a cost-effective, sustainable approach that works with the natural grade.
Landscaping Adjustments
Rain Garden Installation
Convert one of the existing low spots into a designed rain garden planted with native, water-tolerant species such as sedges, rushes, and Pacific Northwest wildflowers. Rain gardens naturally absorb and filter storm water while adding visual interest to the property.
Permeable Landscape Beds
Replace compacted soil in planting beds near the foundation with amended, well-draining soil topped with coarse mulch. This increases the yard's natural absorption capacity and reduces surface runoff toward the foundation.
Strategic Tree Planting
Plant deep-rooted native trees (such as Western Red Cedar or Ponderosa Pine) in the rear yard to increase natural water uptake. Mature trees can absorb up to 100 gallons of water per day, significantly reducing surface saturation over time.
Ongoing Maintenance & Prevention
Even the best drainage systems require regular maintenance. These tips will help homeowners keep their drainage infrastructure functioning properly year-round and prevent future water accumulation issues.
Inspect Gutters & Downspouts Quarterly
Clean gutters and verify downspout extensions are intact and discharging at least 6 feet from the foundation. Replace any damaged sections immediately.
Clear Catch Basins Twice Annually
Remove sediment, leaves, and debris from catch basin grates and sumps in spring and fall. Ensure inlet and outlet pipes are clear of obstructions.
Monitor Grading After Each Season
Walk the property after spring thaw and fall rains. Look for new settling, erosion, or areas where water pools. Early detection prevents small issues from becoming costly repairs.
Maintain Landscape Beds & Rain Gardens
Keep mulch at 2-3 inches depth, remove invasive weeds, and replace dead plants in rain gardens promptly. Healthy plantings maximize water absorption.
Test Sump Pump Before Wet Seasons
If your home has a sump pump, test it by pouring water into the pit and verifying activation. Consider installing a battery backup for power outage protection.
Document & Photograph Annually
Take photos of known problem areas each year for comparison. This record helps track improvements and identify any areas that may need additional attention.
Cost Overview & Prioritization
We recommend a phased approach to implementation, starting with the highest-impact, most urgent improvements and progressing toward long-term sustainable enhancements.
Phase 1 -- Immediate (Within 30 Days)
Address the most critical water intrusion risks that threaten the home's foundation and structure.
- Downspout extension & redirection
- Foundation perimeter re-grading
- French drain system installation
- Catch basin network for rear yard
Phase 2 -- Short-Term (1-3 Months)
Improve yard usability and prevent secondary issues from developing.
- Channel drain along driveway threshold
- Rear yard depression fill & grading
- Permeable landscape beds near foundation
Phase 3 -- Medium to Long-Term (3-12 Months)
Sustainable, natural solutions that improve the property's long-term water management and curb appeal.
- Grass-lined swale along property line
- Rain garden installation
- Strategic native tree planting
Ready to Solve Your Drainage Problems?
ADR Enterprises provides free on-site drainage assessments for homeowners throughout the Spokane and Inland Northwest region. Our team will evaluate your specific property conditions and deliver a custom improvement plan with transparent pricing.