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Managing sediment pollution -...
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www.tauranga.govt.nz 91 Willow Street Private Bag 12022 Tauranga 3110 Phone (07) 577 7000 www.tauranga.govt.nz ONYX 15950 Managing sediment pollution on small earth works sites Key to Site Diagram The following sediment and erosion control measures should be regularly checked and maintained as required. 1. Clean water diversions Divert overland flow away from the site works with a stabilised bund or diversion channel. This will greatly reduce the effort required to prevent erosion and sediment runoff. 2. Minimise exposed areas Expose only as much ground as needed at any one time. Topsoil and revegetate exposed ground as soon as possible. 3. Cover stockpiles Excavated materials should be covered when not in use and stored away from low points and run off channels. Runoff from stockpiles needs to be treated by a sediment control measure such as a silt fence. 4. Silt fence Silt fences are useful for small disturbed areas. For steep slopes, use more than one silt fence and decrease spacing between fences as the slope increases. A decanting earth bund used in conjunction with silt fences should be used on sites with high stormwater flows. 5. Retaining walls Retaining walls must be built before the building foundations are constructed. > 1.5m All retaining walls at or over 1.5m high require a building consent. < 1.5m Retaining walls less than 1.5m high may not require a building consent, if and only if the wall does not and will not be bearing a surcharge. 6. Temporary downpipes and surface drains Temporary downpipes should be fitted as soon as the roof is installed and directed to the clean water system to further reduce nuisance. 7. Site wash out pit/bund Concrete washings, paint, water blasting, equipment washing, concrete and tile cutting can be highly alkaline and contain oxides, heavy metals or petroleum products which will affect waterways. Care must be taken to contain them so a wash out pit/bund should be constructed to capture the discharge. 8. Stabilised construction entranceway A stabilised construction entranceway should be built using crushed rock aggregate before construction vehicles enter the site to prevent tracking of dirt onto the road and into the stormwater network. Minimum 2m wide and 150mm deep 9. Install private stormwater reticulation Install private stormwater reticulation to enable clean stormwater to be discharged to the Council stormwater network at the earliest possible stage. 10. Install vehicle crossing clear of street furniture The vehicle crossing is to be located clear of street furniture and trees. (Failure to comply may result in the asset protection bond not being refunded and expensive remedial works required.) Silt fence detail Post driven firmly into ground Direction of flow Geotextile filter fabric fixed firmly to post/waratah 400mm min above ground 200mm min depth for geotextile 400mm min post depth 2m max Sediment from building and development sites is not “just dirt”. It contains contaminants which are harmful to the environment. The Stormwater Pollution Prevention Bylaw makes it an offence to discharge contaminants to Council’s stormwater network and also requires that the network must be protected from damage or alteration.
Transcript of Managing sediment pollution -...
www.tauranga.govt.nzwww.tauranga.govt.nz
91 Willow Street Private Bag 12022 Tauranga 3110 Phone (07) 577 7000
www.tauranga.govt.nzON
YX 1
5950
Managingsedimentpollution
on small earth works sites
Key to Site DiagramThe following sediment and erosion control measures should be regularly checked and maintained as required.
1. Clean water diversions Divert overland fl ow away from the site works with a stabilised bund or diversion channel. This will greatly reduce the effort required to prevent erosion and sediment runoff.
2. Minimise exposed areasExpose only as much ground as needed at any one time. Topsoil and revegetate exposed ground as soon as possible.
3. Cover stockpilesExcavated materials should be covered when not in use and stored away from low points and run off channels. Runoff from stockpiles needs to be treated by a sediment control measure such as a silt fence.
4. Silt fenceSilt fences are useful for small disturbed areas. For steep slopes, use more than one silt fence and decrease spacing between fences as the slope increases.
A decanting earth bund used in conjunction with silt fences should be used on sites with high stormwater fl ows.
5. Retaining wallsRetaining walls must be built before the building foundations are constructed.> 1.5m All retaining walls at or over 1.5m high require a building consent.< 1.5m Retaining walls less than 1.5m high may not require a building consent, if and only if the wall does not and will not be bearing a surcharge.
6. Temporary downpipes and surface drainsTemporary downpipes should be fi tted as soon as the roof is installed and directed to the clean water system to further reduce nuisance.
7. Site wash out pit/bundConcrete washings, paint, water blasting, equipment washing, concrete and tile cutting can be highly alkaline and contain oxides, heavy metals or petroleum products which will affect waterways. Care must be taken to contain them so a wash out pit/bund should be constructed to capture the discharge.
8. Stabilised construction entrancewayA stabilised construction entranceway should be built using crushed rock aggregate before construction vehicles enter the site to prevent tracking of dirt onto the road and into the stormwater network. Minimum 2m wide and 150mm deep
9. Install private stormwater reticulationInstall private stormwater reticulation to enable clean stormwater to be discharged to the Council stormwater network at the earliest possible stage.
10. Install vehicle crossing clear of street furnitureThe vehicle crossing is to be located clear of street furniture and trees. (Failure to comply may result in the asset protection bond not being refunded and expensive remedial works required.)
Silt fence detailPost driven fi rmly into groundDirec
tion of
fl ow
Geotextile fi lter fabric fi xed fi rmly to post/waratah
400mm min above ground
200mm mindepth for geotextile
400mm minpost depth
2m max
Sediment from building and development sites is not “just dirt”. It contains contaminants which are harmful to the environment. The Stormwater Pollution Prevention Bylaw makes it an offence to discharge contaminants to Council’s stormwater network and also requires that the network must be protected from damage or alteration.
3. Cover stockpilesPrevent dirt piles from washing away.
1. Clean water diversions Install a raised bund to divert rain water away from the work site.
7. Site washout / bund pit Have a safe place for concrete washings, paint etc.
4. Silt fence Captures loose sediment from the work site.
8. Stabilised construction entranceway Install before construction vehicles arrive to help keep dirt on site.
10. Install vehicle crossing clear of street furniture
9. Install private stormwater reticulation Install this at the earliest possible stage.
2. Minimise exposed areas Expose only as much earth as needed at any one time.
6. Temporary downpipes and surface drains Fit these as soon as the roof is installed.
A Consent should be applied for and received before earthworks commence. Once earthworks start an appropriate combination of erosion and sediment control measures should be used.
This guide provides a brief outline of appropriate measures that can be used. For more in depth advice, see The Builders Pocket Guide or visit www.bpg.co.nz
If you are doing any sort of earth works you need to follow these simple measures to prevent sediment from entering the Council’s stormwater system.
If you are doing any sort of earth works you need to follow these simple measures to prevent sediment from entering the simple measures to prevent sediment from entering the Council’s stormwater system.
www.tauranga.govt.nz
5. Build retaining wallsbefore constructing the building foundations.
