Updated: November 2025
Grading and drainage plans represent essential civil engineering documents for Hermosa Beach properties addressing coastal lot topography, stormwater management, and environmental compliance throughout this premium South Bay beach community. Our licensed Professional Engineers with over 20 years of combined experience specialize in coastal civil engineering, Water Quality Management Plans (WQMP), and Los Angeles County grading permit requirements. Understanding proper grading and drainage design is critical for Hermosa Beach homeowners undertaking new construction, additions, or site improvements on properties averaging $1.8 million where proper water management protects structures, prevents flooding, and preserves the coastal environment.
Hermosa Beach's unique setting, with approximately 20,000 residents living between the Pacific Ocean and steep hillside terrain, creates complex drainage challenges including minimal lot slopes in the flatlands (0.5-2% grades), hillside runoff management in the eastern neighborhoods, and strict environmental regulations protecting Santa Monica Bay water quality. The city's building department and Los Angeles County require comprehensive grading and drainage plans for most projects, ensuring stormwater is properly managed while complying with California's aggressive coastal water quality standards.
What Are Grading and Drainage Plans for Residential Properties?
**Direct Answer:** Grading and drainage plans are civil engineering documents showing proposed lot topography, drainage systems, and stormwater management for residential construction projects. California-licensed Professional Engineers design site grading to direct water away from structures, calculate drainage system sizing, prepare WQMP compliance documentation, and create PE-stamped plans required for grading permits and building department approval. These plans prevent flooding, foundation damage, erosion, and coastal water pollution while ensuring compliance with Los Angeles County and California Coastal Commission requirements.
In California's environmentally regulated coastal zone, grading and drainage design extends far beyond simple gutter installation. Every project must demonstrate how stormwater runoff will be captured, treated for pollutants, and discharged without degrading Santa Monica Bay water quality. Hermosa Beach sits entirely within the California Coastal Zone, requiring Coastal Development Permits for many projects and strict adherence to Post-Construction Stormwater Requirements mandated by the Los Angeles Regional Water Quality Control Board.
The grading and drainage engineering process addresses critical questions: How do you manage runoff on minimal-slope beachfront lots? What drainage systems work in sandy coastal soils? How do you prevent hillside erosion during intense winter storms? What pollutant treatment is required before discharge? Professional civil engineers answer these questions through topographic analysis, hydraulic calculations, and drainage system design that protects both property and the coastal environment. Learn more about our civil engineering services for comprehensive site design support.
What Types of Projects Require Grading and Drainage Plans in Hermosa Beach?
**Direct Answer:** Hermosa Beach requires grading and drainage plans for new construction, additions exceeding 500 square feet, site improvements disturbing more than 50 cubic yards of soil, retaining walls over 4 feet in height, and any project within the Coastal Zone requiring stormwater management. Los Angeles County's building department mandates PE-stamped grading plans for virtually all construction projects, ensuring proper drainage design protects properties and Santa Monica Bay water quality in this environmentally sensitive coastal community.
**New Home Construction**
- Existing and proposed topographic surveys showing elevation changes
- Grading plans with contours, spot elevations, and finished floor elevations
- Drainage system layouts (roof drains, area drains, trench drains)
- Driveway and hardscape grading for proper slope and drainage
- WQMP compliance showing stormwater treatment and discharge
Hermosa Beach's minimal natural drainage (flat lots near beach, steep slopes in hills) demands engineered solutions preventing water from ponding against foundations or flowing onto neighboring properties. Our grading designs typically establish minimum 2% slopes away from buildings, directing water to street or alley drainage systems. With median home values of $1.8 million, proper drainage engineering protects significant real estate investments.
**Additions and Major Remodels**
- Reconfiguring drainage around expanded building footprints
- Managing increased impervious surface area (additional roof and hardscape)
- Updating downspout and underground drainage systems
- Integrating new drainage with existing site conditions
- Demonstrating WQMP compliance for net new impervious area
Additions on hillside lots may require retaining walls, stepped foundations, and comprehensive erosion control measures. Our civil engineers coordinate grading design with structural engineers, ensuring foundation systems integrate with site drainage strategies.
**Retaining Walls and Site Improvements**
- Grading plans showing wall locations, heights, and grades
- Foundation and structural design (coordinated with structural engineer)
- Drainage systems behind walls preventing hydrostatic pressure buildup
- Erosion control during construction
- Geotechnical investigation for walls exceeding 6 feet
Hillside retaining walls often cost $350-$550 per linear foot including engineering, permits, and construction—our grading designs minimize wall heights and optimize drainage reducing total project costs by 15-25%. Explore our retaining wall engineering services for hillside lot solutions.
**Pool and Spa Installation**
- Pool deck grading and drainage (preventing water flow toward house)
- Equipment pad elevations and drainage
- Backwash discharge systems meeting coastal water quality standards
- Erosion control during excavation
- Coordination with existing site drainage
Hermosa Beach pools typically use salt-chlorination systems and automated chemical controllers minimizing pollutants in backwash discharge, but engineers must still demonstrate WQMP compliance for pool equipment discharge to Santa Monica Bay watershed.
**Hillside Development and Erosion Control**
- Cut-and-fill calculations minimizing soil export
- Temporary and permanent erosion control measures
- Drainage terraces and interceptor drains on slopes
- Retaining wall systems for level building areas
- Geotechnical engineer coordination for slope stability
California's strict erosion and sediment control regulations (SWPPP requirements for projects disturbing 1+ acre) mandate detailed erosion control plans preventing muddy runoff from reaching storm drains and Santa Monica Bay.
How Does the Grading and Drainage Engineering Process Work for Hermosa Beach Projects?
**Direct Answer:** The grading and drainage engineering process typically takes 3-5 weeks from project kickoff to permit-ready plans. The process includes topographic survey review and site analysis, grading design and hydraulic calculations, drainage system design and sizing, WQMP preparation demonstrating water quality compliance, and PE stamping with building department and Coastal Commission submittal. Our licensed Professional Engineers guide Hermosa Beach homeowners through each phase, ensuring Los Angeles County building code compliance, coastal environmental protection, and efficient permit approval.
Phase 1: Topographic Survey Review & Site Analysis (Week 1)
**Hermosa Beach Site Characteristics**
- Existing grades and drainage patterns
- High points, low points, and natural drainage flow paths
- Location of existing drainage structures (catch basins, inlets, underground pipes)
- Neighboring property elevations and drainage impacts
- Street or alley drainage system connection points
- Geotechnical conditions (sandy beach soils vs. hillside formations)
**Flatland vs. Hillside Considerations** Hermosa Beach's geography divides into two distinct drainage contexts:
**Beachfront and Flatland Areas (West of PCH):**
- Minimal natural slope (0.5-2% typical)
- High groundwater near ocean (seasonal water table 6-12 feet below grade)
- Sandy soils with excellent drainage characteristics
- Limited elevation change requiring careful grading to avoid ponding
- Street drainage via alley systems and coastal outfalls
**Hillside Areas (East of PCH):**
- Steep natural slopes (10-30% grades)
- Runoff concentration from uphill properties
- Mixed soils (older sedimentary formations, colluvium)
- Erosion potential during winter storms
- Retaining walls and terracing common
**Regulatory Review**
- Los Angeles County grading ordinance requirements
- WQMP thresholds (projects creating 500+ sq ft net new impervious surface)
- Coastal Development Permit requirements
- Geotechnical investigation needs (walls >6 feet, slopes >15%)
- Erosion control plan requirements
Phase 2: Grading Design & Hydraulic Calculations (Weeks 2-3)
**Key Deliverables:**
- Grading plans showing existing and proposed contours (1-foot intervals typical)
- Spot elevations at building corners, property corners, drainage structures
- Cross-sections through major grade changes
- Cut-and-fill calculations and soil balance analysis
- Finished floor elevations and building pad grades
- Driveway and walkway slope calculations
Grading Design Principles for Hermosa Beach:
**Positive Drainage Away from Structures:**
- Swales along property lines
- Area drains at building transitions
- Trench drains at garage entries
- Underground drainage piping to street/alley connections
**Minimal Site Disturbance:**
- Minimize cut/fill volumes reducing soil export costs ($45-$75/cubic yard)
- Preserve existing trees and landscape features where possible
- Maintain existing drainage patterns avoiding impacts to neighbors
- Use retaining walls strategically minimizing grading footprint
**Hydraulic Calculations:**
- Rational Method (Q = CIA) for peak flow determination
- Los Angeles County rainfall intensity data (5.5 inches/hour for 10-year storm)
- Manning's Equation for pipe and channel sizing
- Inlet sizing and grate selection preventing clogging
- Underground pipe capacity verification
Phase 3: Drainage System Design (Week 3)
Comprehensive drainage systems for Hermosa Beach properties typically include:
**Roof Drainage:**
- Downspout locations and routing (4-6 per typical house)
- Underground drain pipes (4-6 inch diameter PVC or HDPE)
- Connection to street, alley, or infiltration systems
- Cleanout access for maintenance
**Hardscape Drainage:**
- Driveway slope toward street or trench drains (2-4% minimum)
- Patio and deck grading away from house
- Permeable paving consideration for WQMP compliance
- Area drains in low points or transition zones
**Foundation Drainage:**
- Perforated pipe around foundation perimeter (French drain system)
- Gravel backfill and filter fabric preventing soil intrusion
- Discharge to street drainage or sump pump system
- Waterproofing coordination with foundation contractor
**Underground Drainage Network:**
- Main trunk lines collecting multiple drain sources
- Proper pipe slopes (1-2% minimum for self-cleaning)
- Cleanouts every 100 feet and at direction changes
- Connection to public storm drain system or infiltration
**Infiltration Systems (for WQMP Compliance):**
- Drywell systems (gravel-filled chambers allowing water percolation)
- Permeable paving for driveways and patios
- Rain gardens and bioswales for surface runoff treatment
- Infiltration sizing based on soil percolation testing
Phase 4: WQMP Preparation & Environmental Compliance (Week 4)
**Water Quality Management Plans (WQMP)** Los Angeles County requires WQMPs for projects creating 500+ square feet of net new impervious surface. Our WQMP documentation includes:
**Pollutant Source Control Measures:**
- Landscape areas minimizing fertilizer/pesticide runoff
- Covered trash/recycling enclosures
- Proper storage of pool chemicals and maintenance products
- Education on stormwater-friendly practices
**Site Design Best Management Practices (BMPs):**
- Permeable paving reducing runoff volume
- Landscape areas promoting infiltration
- Roof drainage to vegetated areas
- Minimizing directly connected impervious areas
**Treatment Control BMPs (if required):**
- Bioretention planters treating runoff
- Sand filters or proprietary devices
- Extended detention basins (uncommon on small lots)
- Sizing calculations meeting 85th percentile storm treatment
**Maintenance Plans:**
- Annual inspection and maintenance schedules
- Property owner responsibilities
- Record-keeping requirements
Hermosa Beach's coastal location makes WQMP compliance critical—untreated runoff flowing to Santa Monica Bay damages marine ecosystems and violates Clean Water Act mandates enforced by Regional Water Quality Control Board.
Phase 5: PE Stamping & Permit Submittal (Week 5)
Our California-licensed Professional Engineer reviews all designs, verifies code compliance, and applies official PE stamp required for grading permits. We prepare:
- Signed and stamped grading and drainage plan sets (2-4 sheets typical)
- Supporting hydraulic calculations and design documentation
- WQMP documentation and BMP sizing calculations
- Erosion and sediment control plans (ESC) if required
- Geotechnical review coordination and recommendations
Hermosa Beach building department (through Los Angeles County) processes grading permits in approximately 2-3 weeks. Coastal Development Permits (when required) add 6-12 weeks. Our thorough submittals and established relationships minimize revision cycles expediting approvals.
What Are the Grading and Drainage Considerations Specific to Hermosa Beach?
**Direct Answer:** Hermosa Beach grading and drainage requires specialized consideration for minimal-slope beachfront lots, sandy coastal soils with high permeability, Santa Monica Bay water quality protection, hillside runoff management, high groundwater near ocean, and strict Coastal Commission environmental review. Los Angeles County's building codes combined with California Coastal Act requirements create unique civil engineering challenges requiring coastal expertise and environmental sensitivity.
Minimal-Slope Beachfront Drainage Challenges
Hermosa Beach's flatland areas (The Strand, Hermosa Avenue, parallel streets) feature lots with minimal natural slope—often 0.5-1.5% across entire properties. Creating positive drainage requires:
**Strategic Grading Design:**
- Raising building pads 6-12 inches above street elevation
- Creating swales along property lines (6-12 inch depth)
- Installing area drains at low points preventing ponding
- Using underground drainage piping when surface grading is insufficient
**Driveway and Garage Challenges:**
- Trench drains at garage entries capturing water
- Sump pump systems when gravity drainage is unavailable
- Raised thresholds and water barriers
- Underground drainage piping to street system
Beachfront properties may require pump systems when finished floor elevations are lower than street drainage connection points—our designs include automatic sump pumps with battery backup preventing flooding during power outages.
Sandy Coastal Soils and Infiltration
Hermosa Beach's western areas feature sandy beach soils with excellent drainage characteristics (percolation rates 5-15 inches/hour). This creates opportunities and challenges:
**Infiltration System Advantages:**
- On-site drainage via drywells or infiltration trenches
- Reduced need for street drainage connections
- WQMP compliance through infiltration BMPs
- Natural groundwater recharge
**Challenges:**
- High seasonal groundwater (6-12 feet below surface near beach)
- Infiltration systems must avoid groundwater contamination
- Foundation waterproofing critical in sandy, permeable soils
- Soil erosion during construction if not properly controlled
Our geotechnical coordination ensures infiltration systems are located above seasonal high groundwater, typically requiring minimum 3-4 feet clearance between infiltration zone and water table.
Santa Monica Bay Water Quality Protection
Hermosa Beach drains entirely to Santa Monica Bay, a Marine Protected Area with strict water quality regulations. Our WQMP designs emphasize:
**Pollutant Source Control:**
- Minimizing fertilizer use in landscape design
- Covered storage for pool chemicals
- Drip irrigation reducing runoff
- Native and drought-tolerant plantings
**Treatment Before Discharge:**
- Bioretention planters treating runoff
- Permeable paving filtering water
- Landscape infiltration areas
- Proprietary treatment devices (when required for larger projects)
**Environmental Compliance:**
- Demonstrating compliance with Los Angeles MS4 Permit
- Coastal Commission review for projects in Coastal Zone
- Clean Water Act Section 402 compliance
- Total Maximum Daily Load (TMDL) requirements for Santa Monica Bay
Failure to demonstrate proper water quality protection can delay or deny permits—our environmental engineering expertise ensures compliance while avoiding project delays.
Hillside Runoff and Erosion Control
Eastern Hermosa Beach hillside properties receive concentrated runoff from uphill areas. Grading designs must address:
**Interceptor Drains:**
- Drainage systems at top-of-slope capturing uphill runoff
- Diversion to street drainage preventing erosion
- Properly sized for tributary area drainage
**Terraced Grading:**
- Step-wise building pads reducing cut/fill
- Retaining walls at terrace breaks
- Drainage systems between terrace levels
- Erosion control on slopes
**Erosion and Sediment Control:**
- Silt fencing and fiber rolls during construction
- Temporary drainage swales and downchute systems
- Stabilized construction entrances preventing mud tracking
- Hydroseeding or erosion control blankets on exposed slopes
Winter storms in Southern California can deliver 3-6 inches of rain in 24 hours—proper erosion control prevents sediment from washing to Santa Monica Bay and violating Clean Water Act regulations.
How Much Do Grading and Drainage Plans Cost in Hermosa Beach?
**Direct Answer (2025 Pricing):** Grading and drainage engineering in Hermosa Beach typically costs $3,000-$6,000 for new single-family homes on standard lots and $2,000-$4,000 for additions or remodels. Complex hillside sites with retaining walls, challenging drainage, or extensive WQMP requirements range $6,000-$10,000. Costs include grading plans, drainage design, hydraulic calculations, WQMP preparation, erosion control plans, PE stamping, and one round of revisions for building department plan check.
Standard Lot Grading (Flatland/Beachfront)
**New Construction (2,000-3,500 sq ft homes)** $3,000-$5,000 for comprehensive grading and drainage plans on relatively flat beachfront lots. Typical projects include standard foundation grading, roof and hardscape drainage systems, WQMP compliance, and street/alley drainage connections. Hermosa Beach's 30x90 foot typical lots allow straightforward drainage design when significant grade changes aren't required.
**Additions and Remodels (500-1,500 sq ft additions)** $2,000-$3,500 for grading plans addressing expanded building footprints and modified drainage patterns. Simpler than new construction since existing site drainage often remains functional with minor modifications. WQMP documentation still required for net new impervious surface.
**Pool and Spa Projects** $2,500-$4,000 for pool grading, drainage, and equipment pad design. Includes pool deck grading, backwash discharge systems, WQMP compliance for pool equipment, and coordination with existing site drainage.
Hillside Lot Grading
**Moderate Slopes (10-20% grade)** $5,000-$7,500 for hillside grading with one or two retaining walls (under 8 feet height), terraced building pads, and drainage systems managing uphill runoff. Includes geotechnical engineer coordination, erosion control planning, and hillside-specific drainage solutions.
**Steep Slopes (20%+ grade or multiple walls)** $7,500-$12,000 for complex hillside sites requiring extensive retaining walls, challenging drainage, cut-and-fill balancing, and comprehensive erosion control. These projects may involve multiple geotechnical reviews, detailed stability analyses, and complex drainage networks managing concentrated runoff.
**Extensive Site Work** $10,000-$15,000+ for projects involving major site reconstruction, large cut/fill operations (500+ cubic yards), or environmental mitigation requirements. May include Coastal Commission review, biological surveys, or specialized water quality treatment systems.
Factors Affecting Hermosa Beach Grading Costs
**Lot Topography:** Flat beachfront lots cost 30-40% less to engineer than comparable hillside properties due to simpler grading, fewer retaining walls, and straightforward drainage patterns.
**Coastal Commission Involvement:** Projects requiring Coastal Development Permits may need additional environmental documentation, biological surveys, or public access analysis, adding $2,000-$5,000 to engineering costs and 8-16 weeks to permit timelines.
**Geotechnical Complexity:** Sites requiring multiple geotechnical investigations (retaining wall foundations, slope stability, infiltration testing) add $3,000-$8,000 in geotechnical engineer fees coordinated by civil engineer.
**WQMP Complexity:** Standard WQMPs for single-family homes cost $800-$1,500 (included in base civil engineering fees). Complex projects requiring proprietary treatment devices or extensive bioretention systems add $1,500-$3,000.
**Permit Fees & Additional Costs:**
- Los Angeles County grading permits: $1,200-$3,500
- Plan check fees: $600-$1,500
- Coastal Development Permits (when required): $2,500-$8,000
- Geotechnical reports: $2,500-$6,000
- Topographic surveys: $1,500-$3,500
**Construction Administration:** Optional construction phase services (site inspections, grading verification, RFI responses) typically cost $1,500-$3,000 but prevent installation errors and facilitate final approvals.
How Do You Select the Right Civil Engineer for Hermosa Beach Grading and Drainage?
**Direct Answer:** Choose a California-licensed Professional Engineer with active Civil credentials, proven coastal residential experience, Los Angeles County grading permit expertise, and WQMP compliance knowledge. Verify license status at bpelsg.ca.gov, review completed projects in beach communities, confirm professional liability insurance coverage, and ensure understanding of Coastal Commission requirements and Santa Monica Bay water quality regulations specific to Hermosa Beach's environmental sensitivity.
Essential Qualifications
**California Civil PE License & Coastal Experience**
- Active California Professional Engineer license (Civil specialty)
- 10+ years coastal residential grading and drainage design
- Portfolio demonstrating beach community projects (Hermosa, Manhattan, Redondo, Newport, Laguna, etc.)
- Knowledge of Los Angeles County grading ordinance and amendments
- Professional liability insurance ($1-2 million minimum)
**WQMP and Environmental Expertise**
- Los Angeles County MS4 Permit requirements
- WQMP preparation and BMP selection
- Santa Monica Bay TMDL requirements
- California Coastal Commission review processes
- Clean Water Act compliance and enforcement
Ask potential engineers about their WQMP approval track record and experience with Coastal Commission permits.
Geotechnical Coordination Experience
Many Hermosa Beach projects require geotechnical investigations. Civil engineers should:
- Coordinate soils reports and infiltration testing
- Interpret geotechnical recommendations for grading design
- Work with geotechnical engineers on retaining wall design
- Understand coastal soil conditions and challenges
Our established relationships with South Bay geotechnical firms ensure seamless coordination, preventing the delays and conflicts common when civil and geotechnical engineers don't collaborate effectively.
Why Choose AAA Engineering Design for Hermosa Beach Grading and Drainage?
**Direct Answer:** AAA Engineering Design provides California PE-licensed civil engineering with 20+ years of coastal residential experience. We've completed 60+ projects in Hermosa Beach, Manhattan Beach, and South Bay communities, offering expertise in beachfront drainage, hillside grading, WQMP compliance, and Coastal Commission coordination. Our understanding of Hermosa Beach's unique challenges—from minimal-slope lots to Santa Monica Bay protection—delivers grading solutions that protect properties and the environment while ensuring efficient permit approval.
South Bay Coastal Expertise
We serve Hermosa Beach and surrounding communities:
- Manhattan Beach
- Redondo Beach
- El Segundo
- Torrance
- Palos Verdes Peninsula
- Los Angeles coastal areas
- All Southern California beach cities
**Local Hermosa Beach Knowledge:**
- Understanding of beachfront vs. hillside drainage challenges
- Familiarity with Los Angeles County building department processes
- Relationships with local geotechnical engineers
- Knowledge of Coastal Commission permitting requirements
- Experience with Santa Monica Bay WQMP standards
Comprehensive Civil Engineering Services
From initial feasibility to construction closeout:
- Grading and drainage plan preparation
- WQMP compliance documentation
- Erosion and sediment control planning
- Retaining wall design coordination
- Geotechnical engineer coordination
- Construction administration and inspection
- Final grading certification
Competitive Pricing
Hermosa Beach grading and drainage fees: $3,000-$8,000 for most residential projects
- Fixed-price agreements
- 3-5 week typical turnaround
- One revision round included
- Responsive communication
Contact us today for a free consultation on your Hermosa Beach grading and drainage project.
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