Cleanup of Sewage Lakes: Case Studies in Jeddah and Riyadh

Background Jeddah Sewage Lake – Drivers and project overview – Recommended plan – Clean-up Completion Al-Nazeem Sewage Lake (Riyadh) – Project overview – Sediment management – Clean-up status Project’s Benefits

Septage issues in nearly all Cities – ~50 % of population served by central collection systems – Country-wide issue that is independent of city size

No inventory available for sewage lakes Jeddah – Only 6 percent of municipal planning area is currently sewered – ~140,000 m3/day hauled by tanker trucks Riyadh – ~50 percent of population on central collection system Wastewater pumped from cesspits and trucked to sewage lake – Air pollution from trucks – Significant energy investment in trucking

Background Jeddah Sewage Lake – Drivers and project overview – Recommended plan – Clean-up Completion Al-Nazeem Sewage Lake (Riyadh) – Project overview – Sediment management – Clean-up status Project’s Benefits

Received 1500 to 2000 tanker trucks/day Up to 50,000 m3/day of sewage Lake grew to 2.8 km2 in surface area

May 2010 – Custodian of the Two Holy Mosques King Abdullah bin Abdulaziz issued a royal decree ordering that the hazardous Sewage Lake be emptied within 1 year – NWC took responsibility for the project June 2010 – NWC hires Lake Contractor July 2010 – Water evacuation efforts initiated – Planning consultant hired October 2010 – Lake Evacuation completed November 2010 to July 2011 – Sediment clean-up July 25, 2010 October 2, 2010

Flood Management – Removal of the Sewage Lake Dam Water Management – Evacuation of the Lake – Water Use and Agricultural Activities Sediment Management – Characterization – Treatment/Management alternatives Regulatory Requirements Mitigation Needs Recommended Plan Plan Supervision 9

Additional sediment depth sampling points – 125 measurements Sediment depths – Main Lake – <0.5 m – West Lake - <1.2 m Sediment volume – Main Lake 300,670 m 3 – West Lake 84,724 m 3 10 Total Volume = 385,000 m3

11 ~ 3-5 cm thick Characteristics of silty clay

Main Lake Data – Data indicated meeting KSA criteria for agricultural use of sludge and US EPA “Exceptional Criteria” – A few sites with elevated petroleum hydrocarbons Secondary Lake – Showed sediments also met KSA and EPA Criteria – Did show general contamination by petroleum hydrocarbons

Open Water and Wetlands Ecosystem Upland Ecosystem Planted Forest

Continued drying of sediments – Use mineral material as a drying agent – Sample new areas as can be accessed Mix thinner sediments in place – When sufficiently dry Excavate thicker sediments – Spread in upper areas of the Main lake with thin deposits Mix sediments that have been spread Conduct “Site Release Sampling Plan” – Verification of site safety Excavate sediment material littered with trash from former conveyance channel and dispose at a land fill

16 Organic Sediment <50% Organic Matter ~0.75 g/cc Mineral Soil <1% Organic Matter ~1.5 g/cc Subsoil Mixed Topsoil <25% Organic Matter ~1.0 g/cc Subsoil Stratified Sediment Before Mixing Topsoil Condition After Mixing 20 cm 10 cm 30 cm Tillage

17 Stratified Sediment Before Mixing Topsoil Condition After Mixing Tillage

October 2010 – Lake Evacuation completed November - December – Sediment drying and mixing activities – Additional sediment characterization December-February 2011 – Completion of report documentation – Additional rainfall events partially refilling the lake to ~2m depth March – August 2011 – Pumping to evaporation ponds – Continued sediment drying and mixing activities – Completed site release sampling 29 March 2011

Lake evacuation – Delayed because of availability of pumps – Started in March 2011 – Completed in May 2011 Sampling grid – Final grid included 205 cells – Thick vegetation along margins prevented sampling of infrequently flooded areas

Total Organic Carbon – low levels indicating sediments are stable Metals – maximum values <12% of criteria Microbiological – Fecal Coliform – Maximum value of 24 MPN/g versus standard of 1000 MPN/g – Parasite eggs – None detected Petroleum Hydrocarbons – Only 3 sites showed some values exceeding levels of 2000 mg/kg for Total Petroleum Hydrocarbons – Additional mixing and re-sampling significantly reduced levels Cleanup plan was executed and site release sampling demonstrated site was safe for turnover back to the municipality

Background Jeddah Sewage Lake – Drivers and project overview – Recommended plan – Clean-up Completion Al-Nazeem Sewage Lake (Riyadh) – Project overview – Sediment management – Clean-up status Project’s Benefits 23

Lake has been used for approximately 20 years Received – 1000 to 1500 trucks per day – ~20,000 to 30,000 m3/day Mixture of Domestic and Industrial Waste – Domestic waste eliminated in January 2011 – Industrial waste eliminated in Mid-May

Lake area is ~3.5 km2 When cleanup began in June/July 2011 – very little water remained Cleanup focus – Sludge characterization – Sludge drying – Sludge treatment Lake are divided into 4 zone with 39 separate lakes

Characterization focus – Metals – Microbiological indicators – Petroleum hydrocarbon fractions – Volatile and Semi-volatile compounds Results – Zones 3 & 4 – no results exceed criteria – Zones 1 & 2 Metals and hydrocarbon issues at several locations

Clean-up has involved excavation, mixing and combining with clean sand Lake contractor is conducting verification sampling Upon completion – site release sampling will be conducted by an independent laboratory

Background Jeddah Sewage Lake – Drivers and project overview – Recommended plan – Clean-up Completion Al-Nazeem Sewage Lake (Riyadh) – Project overview – Sediment management – Clean-up status Project’s Benefits 30

NWC Efforts have eliminated two long standing health hazards Detailed investigations have led to environmentally sensitive solutions Jeddah Lake project recognized with GLOBAL WATER INTELLIGENCE Reuse Project of the Year (reuse of sludge to enhance soils)

Cleanup of Sewage Lakes: Case Studies in Jeddah and Riyadh