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It seems that the Highways agency may have underestimated the size of the bridge needed over the River Blackwater on their proposed "southern route".
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| Highways Agency/ Hyder Technical Assessment Report p76 (extract) |
| We reject the Highways Agency's proposed solution of constructing a massive bridge across the River Blackwater , its floodplain and ancient water meadows to take its proposed 4-lane highway. |
| The noise pollution from such a bridge would affect the lives of many people who had chosen to live in this quiet, peaceful part of rural Essex. |
It is harder to mitigate noise from raised roads than from carriageways that can be sunk into cuttings.
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| We understand that he bridge would need to be much larger than the 100m total span originally indicated by the Highways Agency, as the floodplain is actually in the region of 400m wide by their chosen site in the |
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| Northern route - Structures |
| "This section of the route would require four major structures, including two structures to carry the new A120 over the existing A120 and two river crossings, over the River Blackwater at Ch. 3600 and over Robins Brook at Ch. 8020. As mentioned in Section 3.7.1, proposed structures over watercourses must now be designed to minimise impact on flood regimes, such that flood risk to property is not increased. The routes have therefore been designed to take advantage of the narrowest points of the flood plains, to minimise the spans required. Environment Agency mapping indicates that in a flood of 1 in 100 year return period, the flood plain boundaries are approximately 100m apart, near Shelborn Bridge." (note: Northern route) |
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| Highways Agency/ Hyder Technical Assessment Report p84 (extract) |
However the Highways Agency are now aware of a visit to the Blackwater Valley by engineers in late April 2005. They were able to observe in some detail the site of the proposed river bridge on the southern route and they noted that at this point the floodplain slopes gently away from the river to an estimated width of some 400m before significant change in ground level in the Blackwater Valley. In the meantime the Environment Agency have also explained to us that - for their approval to be granted - it would be necessary for the road to be designed in such a way as not to increase the flood risk in the area.
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| Southern route - Structures |
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"The new structure over the River Blackwater at Ch. 1000, would again require a 100m total span and could be of a similar type to that proposed for the Northern Route."
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