Site Landscaping & Drainage Inspection

Per EN 1997-1, site grading must be designed to direct surface water away from building foundations and towards the drainage system. Finished ground levels must fall away from buildings at a minimum gradient of 1:60 per common European practice. Fill materials used for grading must be suitable and compacted in layers not exceeding 300 mm to achieve a minimum 95 % of maximum dry density per the Proctor test. Subgrade preparation must comply with the earthworks specification and EN 16907 series for earthworks.

1. Survey finished ground levels to verify gradients fall away from buildings at a minimum of 1:60 in all directions

2. Check that fill materials are suitable engineering fill, free from organic matter, and comply with the earthworks specification per EN 16907

3. Verify compaction of fill layers using in-situ density testing — minimum 95 % of maximum dry density per the Proctor test

4. Inspect transitions between cut and fill areas for differential settlement potential and confirm appropriate treatment

5. Confirm that finished levels match the approved landscaping design drawings within permitted tolerances

- Ground levels falling towards the building rather than away, directing surface water against foundations

- Fill material placed in layers exceeding 300 mm or compacted insufficiently, leading to long-term settlement

- Organic topsoil mixed into structural fill, causing decomposition and settlement over time

- Finished levels not matching design drawings, creating unintended low points where water ponds

Per EN 752, surface water drainage must be designed to manage runoff from the 1 in 30 year rainfall event without flooding and the 1 in 100 year event with climate change allowance without damage to property. Channel drains, gullies, and gratings must comply with EN 1433 and be selected for the appropriate load class (A15 to F900) per the traffic conditions. Surface water must not discharge to the foul sewer unless specifically permitted by the drainage authority. Paved areas must achieve minimum falls of 1:80 to prevent ponding.

1. Verify that surface gradients on paved areas achieve a minimum fall of 1:80 towards collection points (gullies, channels, or permeable surfaces)

2. Check that gullies and channel drains are correctly positioned at low points and are of the correct load class per EN 1433

3. Confirm that surface water drainage is connected to the surface water sewer or attenuation system — not to the foul sewer

4. Inspect gratings for correct slot width, load rating, and secure installation flush with the finished surface

5. Verify the drainage design accounts for the required rainfall return period per EN 752 including climate change allowance

- Paved areas with insufficient falls, causing ponding and potential slip hazards or surface degradation

- Gullies positioned away from the actual low points due to construction tolerances in finished levels

- Surface water incorrectly connected to the foul sewer, causing overloading during storm events

- Channel drain load class too low for the traffic conditions, leading to cracking or collapse under vehicle loads

Per EN 1610, subsurface drains and sewers must be constructed on a stable bed, laid to the designed gradient, and tested for water tightness before backfilling. Pipe materials must comply with the relevant product standard (EN 1401 for PVC-U, EN 13476 for structured-wall pipes, EN 295 for vitrified clay). Filter media and geotextiles must comply with EN 13252 to prevent clogging and allow water passage. Manholes and inspection chambers must comply with EN 476 and be accessible for maintenance.

1. Verify pipe material and class comply with the design specification and relevant product standard (EN 1401, EN 13476, or EN 295)

2. Check pipe gradient using a surveying level — gradient must match the design and provide self-cleansing velocity per EN 752

3. Carry out water tightness testing per EN 1610 Clause 13 (air or water pressure test) before backfilling

4. Inspect bedding and surround material for compliance with the specification — typically Class S, B, or N bedding per EN 1610

5. Confirm manholes and inspection chambers are at all changes of direction, gradient, and pipe size, and are accessible per EN 476

- Pipes laid off-gradient due to inadequate bed preparation, creating low spots where sediment accumulates

- Water tightness test not carried out before backfilling, leaving undetected joint failures

- Incorrect bedding class used, providing inadequate support for the pipe under backfill and traffic loads

- Geotextile filter wrapping omitted around gravel drains, leading to siltation and loss of drainage capacity

Per EN 752 and the principles of sustainable drainage systems (SuDS), stormwater management must control the rate and volume of runoff to pre-development levels or better. Attenuation systems (tanks, crates, ponds) must be designed for the critical storm duration at the required return period. Flow control devices (vortex limiters, orifice plates) must restrict discharge to the permitted rate agreed with the drainage authority. Permeable paving systems must comply with the manufacturer's specifications and maintain infiltration capacity. Water quality treatment must be provided before discharge per local regulatory requirements.

1. Verify that the attenuation system volume matches the design calculation for the critical storm duration and required return period

2. Inspect flow control devices for correct sizing and installation — confirm the restricted discharge rate matches the drainage authority's consent

3. Check permeable paving installation for correct sub-base depth, geotextile separation, and edge restraint per the manufacturer's specification

4. Confirm water quality treatment is provided (e.g., silt traps, filter drains, interceptors) before discharge to watercourses

5. Verify that overflow or exceedance routes are provided and directed away from buildings for storm events exceeding the design capacity

- Attenuation volume undersized due to incorrect storm duration or return period used in calculations

- Flow control device set to a higher discharge rate than the drainage consent permits

- Permeable paving sub-base contaminated with fines during construction, reducing infiltration capacity before handover

- No exceedance route provided for storms exceeding design capacity, risking uncontrolled flooding

Per EN 1997-1 Clause 9, retaining structures must be designed to resist earth pressure, water pressure, surcharge loads, and seismic actions where applicable. Drainage behind retaining walls is essential to prevent hydrostatic pressure build-up and must include a granular drainage blanket or geocomposite drain connected to a collector pipe per EN 1997-1 Clause 9.4.2. Weep holes or drainage outlets must be provided at regular intervals. Backfill materials must be suitable granular fill compacted in layers. Movement joints must be provided at the spacing specified in the design.

1. Verify that retaining wall construction matches the approved structural design including dimensions, reinforcement, and concrete specification

2. Inspect the drainage blanket or geocomposite drain installation behind the wall before backfilling — must cover the full retained height

3. Confirm the collector drain at the base of the wall is correctly laid to gradient and connected to the drainage system

4. Check that backfill is placed in layers not exceeding 300 mm and compacted without applying excessive lateral force to the wall

5. Verify weep holes or drainage outlets are provided and not blocked by backfill or landscaping materials

- Drainage behind the wall omitted or inadequate, leading to hydrostatic pressure build-up and potential wall failure

- Backfill compacted using heavy equipment too close to the wall, applying excessive lateral loads during construction

- Weep holes blocked by soil, landscaping fabric, or planting, preventing water discharge

- Movement joints omitted or incorrectly positioned, leading to uncontrolled cracking of the wall

Per EN 1997-1 and relevant horticultural standards, topsoil must be of adequate quality, depth, and composition for the intended planting. Topsoil must be free from contamination per the site's remediation strategy and meet the chemical and physical requirements of the landscape specification. Planting pits for trees must be of adequate size (minimum 1.5 times the root ball diameter) and incorporate appropriate root barriers where trees are near structures, pavements, or services. Ground cover and grass seeding rates must comply with the landscape specification.

1. Verify topsoil quality by checking the soil analysis report for pH, nutrient content, organic matter, and contamination levels against the landscape specification

2. Confirm topsoil depth meets the specification — typically minimum 150 mm for grass, 300 mm for shrubs, and 600 mm for trees

3. Inspect tree planting pits for adequate size, correct planting depth (root flare at ground level), and installation of root barriers where specified

4. Check that tree staking and protection are installed correctly to support the tree without damaging the trunk

5. Verify seeding and planting rates comply with the landscape specification and confirm mulch is applied to planted beds at the specified depth

- Topsoil contaminated with construction debris, cement, or hydrocarbons, inhibiting plant establishment

- Topsoil depth insufficient, particularly where subsoil has been compacted by construction traffic

- Trees planted too deep with the root flare buried, causing trunk rot and long-term decline

- Root barriers omitted near structures and pavements, allowing tree roots to cause heave damage