Photo: Isuku Iwacu SOIL PRE-TEST REPORT RWANDA RURAL SANITATION – ISUKU IWACU ACTIVITY May 2018 DISCLAIMER The opinions and contents of this report are the sole responsibility of SNV and do not necessarily reflect the views of the United States Agency for International Development or the United States Government TABLE OF CONTENTS 1. Introduction……………………………………………………………………………………………..4 2. Scope of the work……………………………………………………………………………………….4 3. Soil identification……………………….………………………………………………………………9 4. Soil description in different Districts…………………………….……………………………………….10 .Kicukiro District………………………………………………………………………………………….10 Nyarugenge District………………………………………………………………………………………20 Rwamagana District………………………………………………………………………………………28 Kayonza District…………………………………………………………………………………………..36 Ngoma District…………………………………………………………………………………………….49 Ruhango District…………………………………………………………………………………………..61 Nyanza District……………………………………………………………………………………………72 Nyabihu District…………………………………………………………………………………………..79 1 LIST OF TABLES AND FIGURES FIGURES - Figure 1:Soil resistance test with penetrometer………………………………………………..4 - Figure 2:Pit excavation in Rwamagana District………………………………………………..5 TABLES - Table 1:Soil classification based on grain size …………………………………………………8 - Table 2: Technical specifications……………………………………………………………….11 - Table 3: Kicukiro soil profile and lithology presentation………………………………………12 - Table 4: Soil characteristics in Kicukiro District……………………………………………….13 - Table 5: Gishikiri village/Kanombe sector soil resistance……………………………………...14 - Table 6: Kabuye village/Gikondo sector soil resistance………………………………………..15 - Table 7: Ruhanga village/Masaka sector soil resistance………………………………………..16 - Table 8: Nyarugenge soil profile and lithology presentation…………………………………...20 - Table 9: Soil characteristics in Nyarugenge District……………………………………………20 - Table 10: Inyambo village/Nyarugenge sector soil resistance…………………………………..21 - Table 11: Kagunga village/Nyamirambo sector soil resistance…………………………………23 - Table 12: Rwamagana soil profile and lithology presentation…………………………………..28 - Table 13: Soil characteristics in Rwamagana District…………………………………………...28 - Table 14: Nyirabiteri village/Fumbwe sector soil resistance…………………………………….29 - Table 15 : Rwamibungo village/Nyakariro sector soil resistance………………………………..32 - Table 16: Kayonza soil profile and lithology presentation………………………………………36 - Table 17: Soil characteristics in Kayonza District……………………………………………….37 - Table 18: Bwiza village/Nyamirama sector soil resistance………………………………………37 - Table 19: Mbarara village/Rwinkwavu sector soil resistance……………………………………39 - Table 20: Nyamata village/Ndego sector soil resistance…………………………………………42 - Table 21: Rugunga village/Murundi sector soil resistance……………………………………….45 - Table 22: Ngoma soil profile and lithology presentation………………………………………...49 - Table 23: Soil characteristics in Ngoma District…………………………………………………50 - Table 24: Kibimba village/Kibungo sector soil resistance……………………………………….50 - Table 25: Nyamabuye village/Mugesera sector soil resistance…………………………………..52 - Table 26: Nyamirindi village/Mutenderi sector soil resistance…………………………………..54 - Table 27: Rugarama village/Gashanda sector soil resistance…………………………………….56 - Table 28: Ruhango soil profile and lithology presentation……………………………………….59 - Table 29: Soil characteristics in Ruhango District………………………………………………..61 - Table 30: Kajevuba village/Mwendo sector soil resistance……………………………………….62 - Table 31: Karama village/Ntongwe sector soil resistance…………………………………………64 - Table 32: Kidoma village/Mbuye sector soil resistance……………………………………………66 - Table 33: Bugarama village/Bweramana sector soil resistance…………………………………….68 - Table 34: Nyanza soil profile and lithology presentation…………………………………………..72 - Table 35: Gahogo village/Busogo sector soil resistance……………………………………………73 - Table 36: Rugarama village/Busasamana sector soil resistance…………………………………….75 - Table 37: Nyabihu soil profile and lithology presentation………………………………………….79 - Table 38: Soil characteristics in Nyabihu District…………………………………………………...79 - Table 39: Kadatemwa village/Kintobo sector soil resistance………………………………………. 80 - Table 40: Muturirwa village/Rambura sector soil resistance…………………………………………82 2 1 INTRODUCTION Under the USAID-funded Isuku Iwacu – Rwanda Rural Sanitation Activity (RRSA) implemented SNV, and including World Vision International and Water for People in the following eight districts: Kayonza, Kicukiro, Ngoma, Nyabihu, Nyanza, Nyarugenge, Ruhango, and Rwamagana, SNV hired Eng. Dominique HITAYEZU, expert in geotechnical, to carry out additional geotechnical studies across the eight districts. The geotechnical investigations have been realized based on technical specifications and terms of reference submitted by the client. The content of this report will be based mainly on in situ soil investigations, laboratory test analysis in terms of defining the site conditions and characteristics of the existing ground in different districts investigated. 2 SCOPE OF THE WORK. Before starting the site investigation, a site visit has been organized for visual inspection of the project. A reconnaissance visit was done in each District for making identification of the site locations in different cells for each District. The second phase of our mission was devoted to conduct Geotechnical Investigations divided into two tranches: - The first tranche consisted of conducting the penetration test using a light dynamic penetrometer in order to determine the allowable stress of soil in each area identified, and to provide the necessary information on the nature and behaviour of the soil or rock layers in place. Figure1: Soil resistance test with Penetrometer. 3 - The second tranche consisted of conducting soil reconnaissance by making pits 2 m deep each followed by soil sampling. All samples collected were conducted in the laboratory for identification. Figure 2: 2m deep Pit excavation in Rwamagana Our geotechnical study has been conducted in terms of making soil investigations on existing natural ground, making deep investigations on all locations where construction of latrines will be made for determining and defining the soil stability of the materials in place; carrying out all problems encountered and finding the sustainable solutions for each problem. All activities realized are presented in the table below: DISTRICT SECTOR/VILLAGE N0 PITS N0 DCP SOIL SAMPLES GIKONDO/KABUYE 1 1 1 KANOMBE/GISHIKIRI 1 1 1 KICUKIRO GAHANGA/RUKORE 1 0 1 MASAKA/RUHANGA 1 1 1 NYAMIRAMBO/KAGUNGA 1 1 1 NYARUGENGE NYARUGENGE/INYAMBO 1 1 1 FUMBWE/NYIRABITERI 1 1 1 RWAMAGANA NYAKARIRO/RWAMIBUNGO 1 1 1 MURINDI/RUGUNGA RWINKWAVU/MBARARA KAYONZA NDEGO/NYAMATA NYAMIRAMA/BWIZA MUTENDERI/NYAMIRINDI KIBUNGO/KABIMBA NGOMA GASHANDA/RUGARAMA MUGESERA/NYAMABUYE RUHANGO MWENDO/KAJEVUBA BWERAMA/RUGARAMA 4 MBUYE/KIDOMA NTONGWE/KARAMA BUSORO/GAHOGO NYANZA BUSASAMANA/RUGARAMA RAMBURA/KAMIRO NYABIHU KINTOBO/KADATERURWA 3. DYNAMIC CONE PENETRATION TESTS REALIZATION The testing was carried out at the existing ground with a TRL Dynamic Cone Penetration (DCP) which is an instrument designed for the rapid in situ measurement of the structural properties of existing ground with unbound granular materials . The underlying principle of the DCP is that the rate of penetration of the cone, when driven by a standard force, is inversely related to the strength of the material as measured by, for example, the California Bearing Ratio (CBR) test. Where the soil layers have different strengths, the boundaries between the layers can be identified and the thickness of the layers determined. During our DCP testing, we followed TRL instructions stipulating that « penetration rates as low as 0.5 mm/blow are acceptable but if there is no measurable penetration after 20 consecutive blows it can be assumed that the DCP will not penetrate the material. Under these circumstances a hole can be drilled through the layer using either an electric or pneumatic drill or by coring. The lower layers of the ground can then be tested in the normal way ». DCP results have been processed in appendix No.1. The test was conducted by means of a standard TRL DCP device having the following features: - Drop weight: 8 kg - Drop height: 575 mm - Cone diameter: 20 mm - Apex angle of cone: 60° DCP testing were conducted at nine (8) points as follow: - Rwamagana District: 2points - Nyanza District: 2 points - Nyabihu District: 2 points - Nyarugenge District: 2points 4. LABORATORY TESTING The trial pit research was followed by sampling and collection of all samples to the laboratory for identification and analysis. The following laboratory tests have been made on each sample - Sieve analysis 5 - Natural moisture content - Atterberg limits 4.1 Geotechnical investigations This section highlights the detailed subsoil investigation of identified areas . This is based on the field and laboratory tests conducted on all trial pits made. Description of subsoil condition, soil characteristics and details of different parameters will be based on the following tests: 4.2. Index properties and soil classification Index properties refer to those properties of a soil that indicate the type and conditions of the soil, and provide parameters for the classification. They are also referred as classification properties and classification or index tests are performed in laboratory for determination of these properties. Basically, two types of tests are performed to identify the type and conditions of the soil. These include: · Particle size