be rejected if the highest historical level of the water table is too close to the lowest point of the sanitary landfill. This condition is usually specified by state regulations/guidance or during permit review. Because the conditions affecting groundwater problems are so complex, it is essential that investigation of the landfill site include an evaluation by a qualified groundwater hydrologist. 4.2.6.25 Soil. Soil conditions must be suitable for preventing groundwater pollution, for excavating and covering the fill, and for vehicle access. Most soil types can be used for cover material; however, well-graded soils are preferable to other types because of better compactability and workability in all weather conditions. The most ideal soils are silt and clay soils, which restrict leachate and gas movement. Peat, granular, and highly organic soils shall not be utilized for landfills because they contain a large amount of voids and are difficult to compact. Types of materials used for cover material are dependent on the type of leachate control system used in the landfill. Final cover may consist of soils, natural or synthetic liners, or chemically or physically amended earthen materials underlying at least 6 in. of topsoil or other soil that will sustain the growth of vegetation. The cover material shall have a permeability of 1 x 10-5 to 1 x 10-7 cm/s. Federal and state regulations shall be consulted to determine the exact requirements for the specific state in which the landfill is located. 4.2.6.26 Other considerations. The relationship of the potential landfill site to other installation activities must be considered. 1. Aircraft. Sites shall not be located in the vicinity of military or 2. Social consideration. 3. Potential socioeconomic effects of a site should be determined. Sites shall be selected away from human Utilities. The site shall have access to electricity, sanitary 4.2.6.27 Methodology 4.2.6.28 Adherence to a carefully planned sequence of activities to develop a landfill design minimizes project delays and expenditures. A checklist of design activities is presented in Table 4-2-6A, to aid in planning the design effort. These activities are listed in their general order of performance, but the order can vary considerably from site to site and from jurisdiction to jurisdiction, depending on specific conditions. 4.2.6.29 As shown in Table 4-2-6A, initial tasks consist of compiling existing information and generating new information on solid waste characteristics and site conditions. A listing of possible sources for existing information is shown in Table 4-2-6B. A summary of methods to obtain new information is shown in Table 4-2-6C. 4.2.6.30 Throughout the design phase, it is advisable to periodically contact regulatory agency representatives to ensure that the design will meet any new requirements and procedures for permit application submittals. (A sample of documentation requirements for the State of Virginia is included in Appendix A.) Maintenance of close liaison with state and local regulatory officials throughout the design effort is normally helpful in securing a permit without excessive redesigns, especially at a time when environmental protection legislation and regulations are rapidly changing. Two general types of design packages are prepared for a sanitary landfill: 1. Conceptual (preliminary) design plan 2. Construction design plan and specifications. 4.2.6.31 Conceptual design plans normally consist of the following elements provided in sufficient detail to describe proposed filling plans to regulatory agencies and the public. The conceptual design can also serve as a guide for landfilling operations in the event that design construction drawings are not required. 1. Conceptual design plans include: a. An installation map showing existing site conditions. The map shall be of sufficient detail, with contour intervals of 1 ft to 5 ft and a scale of 1 in. = 50 ft to 1 in. = 200 ft, depending on the steepness of the terrain and size of the landfill, respectively. b. A site preparation plan locating the areas and depths designated for cover soil excavation and soil stockpile deposits. Also shown are site facilities locations such as structures, access roads, and utilities. c. Development plans showing final filling and excavation contours. Development plans shall show interim (4- to 6-year) filling and excavation contours if a long-lived site is planned. d. Elevations showing cross sections to illustrate excavation and landfill surface development at several locations across the fill. Cross sections shall be prepared for each phase of the development plan (i.e., interim and final). Step 1 2 Compile existing and generate new site information. a. Perform boundary and topographic survey. b. Prepare base map of existing conditions on-site and near-site: (1) Property boundaries (2) Topography and slopes (3) Surface water (4) Utilities (5) Roads (6) Structures (7) Land use. C. Compile hydrogeological information and prepare location map: (1) Soils (depth, texture, structure, bulk density, porosity, (3) Groundwater (average depth, seasonal fluctuations, hydraulic d. Compile climatological data: e. (1) Precipitation (2) Evaporation (3) Temperature (4) Number of freezing days (5) Wind direction. Identify regulations (federal, state, and local) and design (1) Loading rates (2) Frequency of cover (3) Distances to residences, roads, and surface water (4) Monitoring (5) Roads (6) Building codes (7) Contents of application for permit. C. (1) Excavation plans including benches (3) Completed fill plans (4) Fire, litter, vector, odor and noise controls. Compute solid waste storage volume, soil requirement volumes, and site life d. Develop final site plan showing: (1) Local area (2) Normal fill areas (3) Special working areas (4) Leachate controls (5) Gas controls (6) Surface water controls (7) Access roads (8) Structures (9) Utilities (10) Fencing 11) Lighting 12) Washracks (13) Monitoring wells (14) Landscaping (15) Debris or litter controls (16) Prevailing winds. e. Prepare elevation plans with cross sections of: |