MAIN FEATURE
SPONSORED BY
A spond serving a new highway in Cheshire.
A swale alongside a road in Buckshaw village, in Lancashire.
crates need additional devices upstream of them to remove sediment and other pollutants, there are now systems that have an in-built and easy-to-clean treatment system. In this example, we deploy the StormTech system which includes an Isolator Row to filter out sediment. This can be cleaned out at intervals using standard sewer jetting equipment, accessed via a manhole.
High risk Case Study 5: Motorway Pollution hazard level
Total suspended solids (TSS) Metals
Hydrocarbons
High 0.8 0.8 0.9
Table 9: Pollution hazard indices for motorway (source: CIRIA C753 Table 26.2)
Type of component* TSS Metals Hydrocarbons Oil/water separator Pond
0.8 0.7
0.6 0.7
0.9 0.5
Table 10: Mitigation indices for SuDS components selected (sources: SPEL Class 1 Separator product literature; CIRIA C753 Table 26.3)
*Remember that after the first SuDS component in the treatment train, only half of the mitigation indices for other downstream components can be used in the calculation.
Although runoff from many motorways and major trunk roads currently goes straight into water courses without being treated, this should not be an option for new motorways. There is a high risk that there will be heavy amounts of pollutants in the water and that
10
these will do harm to wildlife and plants.
For any application with high pollutant loading and a known presence of harmful runoff that can cause damage to the environment, the water should be treated before entering any vegetative components of a SuDS management train. In this example, we would deploy a properly sized oil/water separator which can take out over 80% of the TSS before it goes into the pond/basin and will capture oil spillages from accidents on the carriageway.
Having been treated to remove the sediment, the water could flow into a pond. Choosing a pond rather than a basin means that more of the residual sediment will settle out because the body of water in the pond slows down the flow more effectively and the sediment rests in one place for longer. However, pollutants clinging to the sediment will remain at the bottom of the pond and may need to be removed periodically.
It is important to get the balance right between pre-treatment in a manufactured device, where the sediment can be easily removed, and treatment in the pond where removal of the sediment is more difficult and expensive. Savings made in capital costs by selecting a smaller separator will soon be overshadowed by the long-term costs of removing sludge from the pond.
High risk Case Study 6: waste management site Pollution hazard level
Total suspended solids (TSS) Metals
Hydrocarbons
High 0.8 0.8 0.9
Table 11: Pollution hazard indices for waste management site (source: CIRIA C753 Table 26.2)
| February 2024 |
www.draintraderltd.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72
