Case study:Mill house private hydroelectric power generation scheme and fish pass

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Location: 51° 9' 43", -0° 48' 19"
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Project overview

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Status Complete
Project web site
Themes Fisheries, Hydropower
Country England
Main contact forename Ash
Main contact surname Girdler
Main contact user ID
Contact organisation AGA Group
Contact organisation web site http://http://www.agagroup.co.uk/
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
Plan of works at Mill House (image courtesy of A.Girdler at A.G.A Group). Picture reference - see "Project summary"

Project summary

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Mill House is situated on the banks of the River Wey in Surrey. The wheel house, which is still part of Mill House, had historically held a 15 ft. breast shot water wheel. The aim of the project was to once again put the River Wey to use producing energy, via the installation of an Achilles screw turbine. The scheme also incorporated a geo-thermal heating system installed within the structure for the turbine, with a heat pump to transfer hot water to the domestic quarter's central heating system.

The old wheel house was reinforced and refurbished to accommodate the new hydraulic sluice gate housing and the controls to regulate water levels and flow rates to the turbine channel. A requirement of planning permission was to incorporate a fish pass into the design to ensure the protection of migratory and course fish populations. A reinforced concrete fish pass was construction 200m upstream clear of the turbine channel. One of the key elements to the successful operation of the fish pass channel is the installation of artificial plastic reeds referred to as "fish brushes". These fish brushes slow the water flow down and create eddies and back currents to enable fish to swim up the pass.

A range of bioengineering systems were used to prevent erosion and undercutting of the banks along 200m of the clients bank. Products included unplanted and pre-vegetated coir rolls, A.G.A. Span vertical revetment, rock rolls and hardwood fagots, each used according to the dictates of the site conditions and habitat creation required. As a result of these activities new habitat has been created, water meadows restored and the bio-diversity of the project site enhanced.

Picture reference:

A. Reinforced concrete hydro channel 300mm thick walls with 500mm deep base for turbine

B. Reinforced concrete fish pass

C. Hydraulic sluice gates

D. Waterside decking

E. Two steel and oak bridges

F. Restored iron footbridge

G. Bank erosion control

H. Vegetation and turf reinforcement

I. Water meadow reinstatement


The RRC would like to thank A.G.A Group for providing the information and photographs for this case study.

Monitoring surveys and results

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Lessons learnt

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Image gallery


Fish pass construction (image courtesy of A.Girdler at A.G.A Group)
Bioengineering techniques used (image courtesy of A.Girdler at A.G.A Group)
Bioengineering techniques used (image courtesy of A.Girdler at A.G.A Group)
Fish pass (image courtesy of A.Girdler at A.G.A Group)
Fish pass (image courtesy of A.Girdler at A.G.A Group)
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Catchment and subcatchment

Catchment

River basin district Thames
River basin Wey

Subcatchment

River name South Wey (River Slea confluence to Tilford)
Area category 100 - 1000 km²
Area (km2)
Maximum altitude category 200 - 500 m
Maximum altitude (m) 259
259 m
0.259 km
25,900 cm
Dominant geology Siliceous
Ecoregion Great Britain
Dominant land cover Broadleaved Woodland
Waterbody ID GB106039017780



Site

Name Mill house on the River Wey
WFD water body codes GB106039017780
WFD (national) typology
WFD water body name South Wey (River Slea confluence to Tilford)
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present No
Species of interest
Dominant hydrology
Dominant substrate
River corridor land use
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 500
500 m
0.5 km
50,000 cm
Project started 2011/08/01
Works started
Works completed
Project completed 2012/04/01
Total cost category
Total cost (k€)
Benefit to cost ratio
Funding sources privately funded by property owner

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design AGA group
Stakeholder engagement and communication
Works and works supervision AGA group
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure Hydropower
Hydromorphology Continuity for organisms
Biology Fish
Physico-chemical
Other reasons for the project bioengineering techniques used to improve bankside habitats and create water meadow


Measures

Structural measures
Bank/bed modifications Bank improvement, Bank stabilisation, Bank protection
Floodplain / River corridor water meadow creation
Planform / Channel pattern Bypass channel
Other
Non-structural measures
Management interventions
Social measures (incl. engagement)
Other


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative


Monitoring documents



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Additional links and references

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Supplementary Information

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