Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized E2905 v3 REPUBLIC OF KENYA MINISTRY OF WATER AND IRRIGATION ATHI WATER SERVICES BOARD (AWSB) FEASIBILITY STUDY AND MASTER PLAN FOR DEVELOPING NEW WATER SOURCES FOR NAIROBI AND SATELLITE TOWNS Preliminary EIA for the Selected Scenario: Nairobi Water Sources, Phases 1 & 2 Version 03 December 2011 in association with : MANGAT, I.B. PATEL & PARTNERS Egis Bceom International Contents in association with MIBP Contents Executive Summary....................................................................................................iv 1 Introduction...........................................................................................................1 1.1 Master Plan for New Water Sources for Nairobi and Satellite Towns.......................1 1.2 Description of the Administrative, Policy and Regulatory Framework .....................2 1.3 World Bank Environmental and Social Safeguards Policies and Triggers ................9 1.4 Consultations............................................................................................................ 12 2 Study Area...........................................................................................................13 2.1 Geology.................................................................................................................... 13 2.2 Topography and Drainage........................................................................................ 13 2.3 Climate..................................................................................................................... 14 2.4 Groundwater Resources ........................................................................................... 15 3 Development of Groundwater Well Fields .........................................................16 3.1 Potential Groundwater Well Fields.......................................................................... 16 3.2 Scoping of Potential Impacts ................................................................................... 17 3.2.1 Preliminary Exploration .............................................................................................17 3.2.2 Development of New Well Fields and Increased Extraction from existing Well Fields ..........................................................................................................................21 4 Development of the Northern Collector Tunnel, Phase 1 ...................................22 5 Downstream Reserve Flows................................................................................24 5.1 Environmental Flows ............................................................................................... 24 5.2 Environmental Flow Characteristics ........................................................................ 27 5.3 Options for Environmental Flow Release ................................................................ 36 5.4 Indicators of Hydrologic Alteration......................................................................... 38 5.4.1 Range of Variability Approach...................................................................................38 5.4.2 RVA Analysis.............................................................................................................38 5.5 Compensation Flows................................................................................................ 42 5.6 Recommendations for Reserve Flow Release.......................................................... 44 5.7 Impacts from Abstraction of Flows.......................................................................... 46 5.8 Recommendations for Operating Rules ................................................................... 47 6 Cumulative Impacts ............................................................................................50 7 Upstream Catchment Areas.................................................................................55 7.1 Catchment Protection............................................................................................... 55 7.2 Water Quality........................................................................................................... 57 7.3 Importance of Tea Cultivation ................................................................................. 58 8 Anticipated Impacts and Mitigation Measures....................................................60 8.1 Protected Areas and Endangered Species ................................................................ 60 8.2 Impacts from Construction....................................................................................... 62 8.2.1 Maragua Intake...........................................................................................................62 8.2.2 Gikigie Intake.............................................................................................................63 8.2.3 Irati Intake ..................................................................................................................65 8.2.4 Outlet Works ..............................................................................................................66 8.2.5 Excavated Material from the Northern Collector Tunnel ...........................................68 8.2.6 Transmission and Distribution Pipelines ....................................................................69 8.3 Impacts from Operation ........................................................................................... 72 8.4 Impacts and Mitigation Measures ............................................................................ 73 8.5 Aquatic and Riparian Environments ........................................................................ 80 8.5.1 Impacts on Aquatic and Riparian Species ..................................................................80 8.5.2 Impacts on Diseases ...................................................................................................81 8.5.3 Interbasin Transfers....................................................................................................83 8.6 Analysis of Alternatives........................................................................................... 84 9 Environmental Monitoring Plan..........................................................................89 9.1 Draft Environment Management Plan...................................................................... 91 FEASIBILITY STUDY AND MASTER PLAN FOR DEVELOPING NEW WATER Page i SOURCES FOR NAIROBI AND SATELLITE TOWNS Preliminary EIA Version 03 Egis Bceom International List of Tables in association with MIBP List of Tables Table 4-1: Northern Collector Phase 1 Components.................................................................................................... 22 Table 5-1: Common Characteristics for each Flow Component for different disciplines ............................................ 27 Table 5-2: Environmental Influences of Different Flow Components ......................................................................... 29 Table 5-3: Characteristic Environmental Flow Components, Irati (RGS: 4BE6+4BE7, 1950-2010) .......................... 30 Table 5-4: Characteristic Environmental Flow Components for Gikigie (RGS: 4BE8, 1950-2010) ........................... 32 Table 5-5: Characteristic Environmental Flow Components for Maragua (RGS: 4BE9, 1950-2010) ......................... 34 Table 5-6: Characteristic Flows at Proposed Abstraction sites on Northern Collector ................................................ 38 Table 5-7: Summary of Assessments of Hydrologic Alteration on flow rates for the proposed intake sites for Northern Collector Phase 1, comparing the release of 2 x Q95 Reserve Flows with Reserve Flows generated by variable abstraction and release procedures...................................................................................................... 41 3 Table 5-8: Estimates for Required Minimum Downstream Reserve Flows (m /s), NC Phase 1 ............................. 43 Table 5-9: Districts directly impacted by modified downstream flows, showing proportion of households using streams and estimated requirements for household use ......................................................................................... 43 Table 6-1: Average flows into Masinga Reservoir (m 3/sec), and potential changes following diversion of water to the Northern Collector Phase 1.......................................................................................................................... 53 Table 8-1: Impacts related to pipeline construction and operation............................................................................... 70 Table 8-2: Impacts due to Construction of weirs, intake structures and tunnels .......................................................... 74 Table 8-3: Impacts due to Operation of Weirs ............................................................................................................. 75 Table 8-4: Yield of Existing Water Sources ................................................................................................................ 84 Table 8-5: Potential New Water Sources Identified..................................................................................................... 85 Table 8-6: Water Demand Forecast: Nairobi City ......................................................................................................