Permeable pavement: Plan review

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Plan checklist

  1. Do the plans include an appropriate construction sequence that is specific to the construction of the permeable pavement?
  2. To avoid soil disturbance and compaction during construction, will the proposed infiltration area be clearly marked before any site work begins?
  3. Do the plans include an appropriate cross-sectional detail for the permeable pavementAn alternative practice to traditional impervious pavement, prevents the generation of runoff by allowing precipitation falling on the surface to infiltrate through the surface course into an underlying stone reservoir and, where suitable conditions exist, into the native soil.?

Design checklist

  1. Verify the drainage areaThe total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds. directed to any proposed porous pavement. If DCIA runoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. from other areas on-site, in addition to the direct (1:1) rainfall onto the porous pavement, is directed onto porous pavement, the porous pavement cannot be considered disconnected. It must instead be considered, and modeled as, a porous pavement structural SMP. The porous surface must be considered, and modeled as, DCIA. Porous pavement structural SMPs require infiltration testing.
  2. For porous pavement structural SMPs, if infiltration is feasible, verify that the porous pavement design meets all Design Guidance Checklist design standards noted in Appendix F.10, Subsurface InfiltrationThe slow movement of water into or through a soil or drainage system.Penetration of water through the ground surface..
  3. For porous pavement structural SMPs, if infiltration is infeasible, verify that the porous pavement design meets all Design Guidance Checklist design standards noted in Appendix F.14, Subsurface DetentionThe temporary storage of stormwater to control discharge rates, and allow for sedimentation..

For porous pavement DIC systems:

  1. Verify that the porous pavement DIC is installed on-site such that it does not create any areas of concentrated infiltration or discharge.
  2. Verify that the surface slope in any direction across porous pavement does not exceed 5%.
  3. Verify that the choker course depth is a minimum of two inches.
  4. If an underdrainA perforated pipe used to assist the draining of soils. is proposed, verify that the first 1.5 inches of runoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. are stored below the lowest invert of the underdrainA perforated pipe used to assist the draining of soils..
  5. Verify that an appropriate porous pavement curve number value is used when performing Flood Control calculations.
  6. Verify that the stone storage bed depth is a minimum of eight inches, except when located beneath walkways or play surfaces, for which a depth of four inches is allowable.
  7. Verify that stone is separated from soil media by a geotextileFilter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils. or a pea gravel filter to prevent sandMineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm., siltSoil or media particles smaller than sand and larger than clay (3 to 60 m), and sedimentSoil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls. from entering the system.
  8. Verify that the stone storage system has a level bottom. Terraced systems may be used to maintain a level infiltration interface with native soilThe natural ground material characteristic of or existing by virtue of geographic origin. while accommodating significant grade changes.
  9. Verify that pretreatmentInitial capturing and removal of unwanted contaminants, such as debris, sediment, leaves and pollutants, from stormwater before reaching a best management practice; Examples include, settling forebays, vegetated filter strips and gravel diaphragms. is provided for all runoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. entering the porous pavement, including pretreatmentInitial capturing and removal of unwanted contaminants, such as debris, sediment, leaves and pollutants, from stormwater before reaching a best management practice; Examples include, settling forebays, vegetated filter strips and gravel diaphragms. of runoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. from all inlets. At a minimum, this can be achieved through the use of sumps and traps for inlets, sump boxes with traps downstream of trench drains, and filter strips for overland flowOpen space floodway channels, road reserves, pavement expanses and other flow paths that convey flows typically in excess of the capacity of the Minor Drainage System..
  10. Verify that, when SMPs are used in series, the storage areas for all SMPs provide cumulative static storage for the WQv.
  11. Verify that any imperviousA hard surface area (e.g., road, parking area or rooftop) that prevents or retards the infiltration of water into the soil. liner, if necessary, is not interrupted by structures within the basinGround depression acting as a flow control and water treatment structure, that is normally dry. footprint. The plans must indicate that the imperviousA hard surface area (e.g., road, parking area or rooftop) that prevents or retards the infiltration of water into the soil. liner is to be continuous and extend completely up the sides of any structures that are located within the lined basinGround depression acting as a flow control and water treatment structure, that is normally dry. footprint to the ground surface. If additional liner material must be added to extend up the structures, the additional liner sections are to be joined to the rest of the liner with an imperviousA hard surface area (e.g., road, parking area or rooftop) that prevents or retards the infiltration of water into the soil. seam per the manufacturers’ recommendations.
  12. Verify that underdrains, if proposed for porous pavement DIC systems, meet the following requirements:
  13. Underdrains must be surrounded by a sandMineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm. or stone layer to filter sedimentSoil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls. and facilitate drainageNatural or artificial means of intercepting and removing surface or subsurface water (usually by gravity)..
  14. The minimum allowable thickness of a sandMineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm. or stone filter layer is six inches both above and beneath the underdrainA perforated pipe used to assist the draining of soils..
  15. To prevent clogging, underdrainA perforated pipe used to assist the draining of soils. pipes must be surrounded by a geotextileFilter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils. fabric if a sandMineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm. layer is used.
  16. Verify that an adequate number of appropriately placed cleanouts, manholes, access panels and other access features are provided to allow unobstructed and safe access to the porous pavement structural SMP for routine maintenance and inspection of inflow, outflow, underdrains, and storage systems.
  17. Verify that an observation well is provided for a storage system that includes stone storage and that it meets the following requirements:
  18. The observation well must be placed at the invert of the stone bed.
  19. An observation well must be located near the center of the stone bed system to monitor the level and duration of water stored within the SMP (drainage time).

Adequate inspection and maintenance access to the observation well must be provided.

  1. A manhole may be used in lieu of an observation well if the invert of the manhole is installed at or below the bottom of the SMP and the manhole is configured in such a way that stormwater can flow freely between the SMP and the manhole at the SMP’s invert.
  2. Verify that access features are provided for all underground storage systems that are not stone storage beds.
  3. Verify that a sufficient number of access points in the system are provided to efficiently inspect and maintain the infiltration area.

For cast-in-place vault systems, verify that access features consist of manholes or grated access panels or doors. Grated access panels are preferred to maintain airflow.

For grid storage or other manufactured systems, verify that the manufacturer’s recommendations are followed.

  1. Verify that ladder access is proposed for vaults greater than four feet in height.
  2. Verify that header pipes, at minimum 36-inch diameter, connected to manholes at each corner of the subsurface system are provided. Alternatively, smaller header pipes may be used if cleanouts are provided on every second manifold pipe/header pipe junction, on alternating sides of the SMP.

Materials checklist

  1. Verify that porous bituminous asphaltA mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces., if proposed, is specified on the plans as meeting the following specifications:
    1. Bituminous surface must be laid with a bituminous mix of 5.75% to 6% by weight dry aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations..
    2. In accordance with American Society of Testing and Materials (ASTM) D6390, drain down of the binder must be no greater than 0.3%.
    3. AggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. material in the asphaltA mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces. must be clean, open-graded, and a minimum of 75% fractured with at least one fractured face by mechanical means of each individual particle larger than ¼-inch, and it must have the following gradations:

Porous AsphaltA mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces. Binder Course AggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. Gradation U.S. Standard Sieve Size Percent Passing By Weight 1” 100% 3/4” 90-100% 1/2” 80-100% 3/8” 50-80%

  1. 4 10-20%
  2. 8 5-10%
  3. 40 3-8%
  4. 200 0-3 %

Porous AsphaltA mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces. Wearing Course AggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. Gradation U.S. Standard Sieve Size Percent Passing By Weight 5/8” 100% 1/2” 95-100% 3/8” 70-95%

  1. 4 20-40%
  2. 8 10-20%
  3. 40 0-8%
  4. 200 0-3%

Neat asphaltA mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces. binder modified with an elastomeric polymer to produce a binder meeting the requirements of PG 76-22 as specified in American Association of State Highway and Transportation Officials (AASHTO) MP-1. The elastomer polymer must be styrene-butadiene-styrene, or approved equal, applied at a rate of 3% by weight of the total binder. Hydrated lime should be added at a dosage rate of 1% by weight of the total dry aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. to mixes containing granite. Hydrated lime must meet the requirements of ASTM C 977. The additive must be able to prevent the separation of the asphaltA mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces. binder from the aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. and achieve a required tensile strength ratio of at least 80% on the asphaltA mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces. mix when tested in accordance with AASHTO T 283. The asphaltic mix must be tested for its resistance to stripping by water in accordance with ASTM D-1664. If the estimated coating area is not above 95%, anti-stripping agents must be added to the asphaltA mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces.. The asphaltic mix must be tested for its resistance to stripping by water in accordance with ASTM D 3625. If the estimated coating area is not above 95%, anti-stripping agents must be added to the asphaltA mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces.. Verify that porous concrete, if proposed, is specified on the plans as meeting the following specifications: [Section 4.2.4, 3] Porous concrete must use Portland Cement Type I or II conforming to ASTM C 150 or Portland Cement Type IP or IS conforming to ASTM C 595. AggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. must be No. 8 coarse aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. (3/8-inch to No. 16) per ASTM C 33 or No. 89 coarse aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. (3/8-inch to No. 50) per ASTM D 448. An aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations./cement ratio range of 4:1 to 4.5:1 and a water/cement ratio range of 0.34 to 0.40 should produce porous pavement of satisfactory properties in regard to permeability, load carrying capacity, and durability characteristics.


Verify that permeable paver and grid systems, if proposed, are specified on the plans as meeting the following specifications:

  1. Permeable paver and grid systems must conform to manufacturer specifications.
  2. The systems must have a minimum flow through rate of five inches per hour and a void percentage of no less than 10%.
  3. Gravel used in interlocking concrete pavers or plastic grid systems must be well-graded and washed to ensure permeability.
  4. Verify that stone designed for stormwater storage, if proposed, is specified on the plans as being uniformly graded, crushed, clean-washed stone and that it is noted that PWD defines “clean-washed” as having less than 0.5% wash loss, by mass, when tested per the AASHTO T-11 wash loss test. AASHTO No. 3 and No. 57 stone can meet this specification.
  5. Verify that all aggregatesA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. used within a porous pavement system meets the following requirements:

Maximum wash loss: 0.5% per AASHTO T-11 Minimum durability index: 35 per ASTM D3744 Maximum abrasion: 10% for 100 revolutions and 50% for 500 revolutions per ASTM C131 Verify that all choker course aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. meets the specifications of AASHTO No. 57 and meets the gradation listed in Table 4.2-3 of the Manual. Verify that sandMineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm., if proposed, is specified on the plans to be AASHTO M-6 or ASTM C-33 sandMineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm. and to have a grain size of 0.02 inches to 0.04 inches. Verify that storage chambers for porous pavement structural SMPs, if proposed, are specified on the plans as meeting the following specifications: Pipe used within a subsurface infiltration SMP must be continuously perforated and have a smooth interior with a minimum inner diameter of four inches. High-density polyethylene (HDPE) pipe, if proposed, must meet the specifications of AASHTO M252, Type S or AASHTO M294, Type S. Any pipe materials outside the SMP are to meet City Plumbing Code Standards. Verify that geotextileFilter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils., if proposed, is specified on the plans to consist of polypropylene fibers and to meet the following specifications (AASHTO Class 1 or Class 2 geotextileFilter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils. is recommended): [Section 4.2.4, 9] Grab Tensile Strength (ASTM-D4632): ≥ 120 lbs Mullen Burst Strength (ASTM-D3786): ≥ 225 psi Flow Rate (ASTM-D4491): ≥ 95 gal/min/ft2 UV Resistance after 500 hrs (ASTM-D4355): ≥ 70% Heat-set or heat-calendared fabrics are not permitted Verify that underdrains, if proposed, are made of continuously perforated HDPE plastic piping with a smooth interior and a minimum inner diameter of four inches. HDPE pipe must be specified on the plans to meet the specifications of AASHTO M252, Type S or AASHTO M294, Type S. Verify that observation wells are specified on the plans as consisting of perforated plastic pipe with a minimum inner diameter of six inches. Verify that cleanouts are made of rigid material with a smooth interior having a minimum inner diameter of four inches.



https://www.pwdplanreview.org/manual/appendices/f.-design-guidance-checklist/f.8-porous-pavement