62 STORMWATER TREATMENT
62-1 General
62-1.01 General
62-1.01A Summary
Section 62 -1 includes general specifications for constructing permanent stormwater treatment best management practices. Earthwork must comply with section 19. Concrete and joint seals must comply with section 51. Sealant must comply with section 41 -5. Reinforcement must comply with section 52. Underdrain must comply with section 68 -2. Miscellaneous metal must comply with section 75. Cable railing must comply with section 83 -2.07.
62-1.01B Definitions
Reserved 62-1.01C Submittals At least 5 business days before placing permeable material, submit a certificate of compliance for the gradation of the material from the source. No more than 5 business days after placing permeable material, submit:
1.At least one ASTM D6913 test on permeable mater ial sampled at: 1.1. Job site 1.2. Authorized location
2.Verification that the permeable materials testing results meet the gradation requirements
62-1.01D Quality Assurance
Submit verification that the placed material complies with the gradation for th e Class 4 and Class 5 permeable materials. Submit verification of the uniformity coefficient for Class 5 permeable material. For Department acceptance, the depth of the permeable material will be measured after the in -place washing is complete.
62-1.02 Ma Terials
62-1.02A General
Reserved
62-1.02B Class 4 Permeable Material
Class 4 permeable material must consist of sand, gravel, or crushed stone that is hard, durable, and clean. The material must be free from organic material, clay balls, or other delete rious substances. The percentage composition by weight of Class 4 permeable material in place must comply with the gradation requirements shown in the following table: SECTION 62 STORMWATER TREATMENT Class 4 Permeable Material Gradation Requirements Sieve size Percentage passing 2" 100 1-1/2" 95–100 3/4" 50–100 3/8" 15–55 No. 4 0–25 No. 8 0–5 No. 100 0 Class 4 permeable material must have a durability index of not less than 40.
62-1.02C Class 5 Permeable Material
Reserved
62-1.02D Miscellaneous Metal
Fabricate the parts shown in the table below from the corresponding materials shown: Miscellaneous Metal Parts Part Material Ladders Steel Handrails Steel Trash screen Steel Components of riser support brackets Stainless steel complying with ASTM A276, Grade 304 CIP inserts must be ferrule loop type
62-1.02E Filter Fabric
Class D filter fabric must comply with the requirements shown in the following table: Class D Filter Fabric Quality characteristic Test method Requirement Permittivity (min and max, sec -1) ASTM D4491 1.6–1.8 Apparent opening size, average roll value (min and max, US standard sieve size) ASTM D4751 60–80 Grab breaking load, 1 -inch grip, in each direction (min, lb) ASTM D4632 120 Apparent elongation, in each direction (min, %) ASTM D4632 50 UV resistance, retained grab breaking load, 500 hours (min, %) ASTM D4355 70
62-1.02F 62-1.02I Reserved
62-1.03 Construction
62-1.03A General
Placing filter fabric must comply with section 68 -1.03B.
62-1.03B Permeable Material
62-1.03B(1) General
Before placement, wash Class 4 and Class 5 permeable materials:
1.To remove silt and clay particles
2.With potable water equal to at least 4 times the volume of the material being placed After placement, wash Class 4 and Class 5 per meable materials:
1.With potable water
2.Until the discharged water has a turbidity reading of: 2.1. 30 NTU or less for a project within the Tahoe Hydrologic Unit 2.2. 200 NTU or less for a project outside the Tahoe Hydrologic Unit SECTION 62 STORMWATER TREATMENT Capture the wash wate r. Handle the wash water by any of the following means:
1.Dispose of
2.Use as dust control
3.Disperse onsite in an authorized location other than the BMP
62-1.03B(2) Class 5 Permeable Material
Place Class 5 permeable material:
1.In a way that does no t damage or displace the filter fabric
2.Using methods that produce a finished surface as shown
62-1.03C 62-1.03H Reserved
62-1.04 Payment
Not Used
62-2 Design Pollution Prevention Infiltration Area
Reserved
62-3 Infiltration Trench
62-3.01 General
62-3.01A Summary
Section 62 -3 includes specifications for constructing infiltration trenches. Concrete curb must comply with section 73.
62-3.01B Definitions
Reserved
62-3.01C Submittals
At least 5 business days before placing permeable material , submit a certificate of compliance for the gradation of the material from the source.
62-3.01D Quality Assurance
Reserved
62-3.02 Materials
62-3.02A General
Filter fabric must be Class D.
62-3.02B Surface Gravel
Surface gravel must be Class 1, Type A permeable material under section 68 -2.02F.
62-3.02C Trench Filler Material
Trench filler material must be Class 6 permeable material and must consist of rock or high porosity backfill material. Rock must be non -crushed, pre -washed, clean, hard, sound, du rable, and uniform in quality. Rock must be free of detrimental quantity of soft, friable, thick elongated or laminated pieces, organic material, clay balls, oil, alkali, or other deleterious substances. The percentage composition by weight of Class 6 perm eable material in place must comply with the gradation requirements shown in the following table: SECTION 62 STORMWATER TREATMENT Class 6 Permeable Material Gradation Requirements Sieve size Percentage passing 4" 100 3" 75 2" 8 1.5" 2 Class 6 permeable material must have a minimum durability index of not less than 40.
62-3.02D Observation Well
PVC pipe for the observation well must be perforated, have a smooth wall, and comply with AASHTO M278. PVC matted end cap and vented well cap must comply with AASHTO M278. Concrete mu st be minor concrete. Pull box must comply with section 86 -1.02C, except an electronic m arker is not required. The cover marking must be OBSERVATION WELL .
62-3.02E Alternative Trench Filler Material
Reserved
62-3.03 Construction
62-3.03A General
Place filter fabric under section 68 -1.03B.
62-3.03B Observation Well
The only joint allowed in the pipe in the observation well is between the perforated and solid wall pipe sections. Place the observation well pipe vertically. No permeable material, san d, or other material must be inside the well pipe.
62-3.04 Payment
Not Used
62-4 Infiltration Basin
Reserved
62-5 Infiltration Gallery
Reserved
62-6 Reserved
62-7 Bioretention
Reserved
62-8 Detention Basin
Reserved
62-9 Austin Earth Berm
Reserved
62-10 Austin Vault Sand Filter
Reserved
62-11 Delaware Sand Filter
Reserved SECTION 62 STORMWATER TREATMENT
62-12 Gross Solids Removal Device
62-12.01 General
Section 62 -12 includes specifications for constructing gross solids removal devices.
62-12.02 Materials
62-12.02A General
Anchorages must comply with the specifications for concrete anchorage devices in section 75 -3.02C.
62-12.02B Miscellaneous Metal
Fasteners used to connect grates and screen to the frame must be vandal resistant. Stainless steel wedge -wire screens, plates, and bars must comply with ASTM A240/ A240M, Type 304, with a no. 2B finish. Finished screens must be descaled by immersion in a nitric/hydrofluoric acid bath, rinsed, and air dried to achieve passivation. Fasteners, anchorage devices, hardware for the inclined screen and screened pipe must be Type 304 stainless steel . Welding of steel members must comply with AWS D1.1, D1.4, and D1.5. Welding of stainless steel members must comply with AWS D1.6. Before welding, prepare and clean with stainless steel brushes and non -ferrous abrasives. Equipment used in the fabrication of carbon steel must not be used. After welding, the stainless steel surface must be smooth and without waves. Fabricate the parts shown in the table below from the corres ponding materials shown: Miscellaneous Metal Parts Part Material Jet plate Steel Deflector Steel Cleanout Steel or Type 304 stainless steel Chain Steel
62-12.02C Fiberglass Reinforced Plastic Components
Reserved
62-12.02D Inclined Screen
Inclined screen must be s tainless steel wedge wire . The screen slot width must be between 0.17 to 0.20 inch. Stainless steel wedge wire screen must have an open area from 60 to 70 percent of the total screen area .
62-12.02E Screened Pipe
Screened pipe, jo ints, supports, hatches, doors and ancillary hardware must be c onstructed of stainless steel. Screened pipe must comply with ASTM A778, and must be Type 316L . Screened pipe must be 0.25 -inch thick well screen with machine -made evenly spaced louvered openin gs perpendicular to the axis of the casing. Fabricate screened pipe with perforations and louvers as shown . Fabrication tolerances on the screened pipe, joints, hatches, and doors must not exceed 0.20 in ch. Screened pipe sections must be joined after fabri cation. Sections must be numbered using a metal tagging system after compatibility matching, with the tag indicating project location and section number. Section numbering must indicate the placement at each location, with the non -louvered section being labeled as the first section and continuing sequentially until the fi nal section for each location. The metal tags must remain in place after installation .
Source: California Standard Specifications, 2024 Edition. Pages 959–963 of 1,372.