CONSTRUCTION NOTES 343 



of the statements may be applied equally to pools intended primarily for 

 wading and swimming. 



General considerations. This discussion (with the exception of that 

 portion relating to winter protection of pools) pertains specifically to the 

 construction of various types of formal garden pools and informal pools 

 and ponds. The problem of water supply should be thoroughly investigated 

 as to the available quantity and the probable cost in order to be certain 

 that the construction of any pool is practicable. In connection with larger 

 pools, and especially pond areas which depend upon natural supply from 

 springs or from surface drainage, there may be seasons of the year when, 

 on account of the lack of adequate supply, the loss through excessive evap- 

 oration may create a stagnant and an unsanitary condition in any pool. 

 Pools constructed where frost action is negligible, and especially in sandy 

 soils, do not need the extent of drainage and reinforcing that is required 

 elsewhere. It is very wise, however, in protecting any pool against action 

 from frost, and especially under clay soil conditions, to provide a large 

 factor of safety. 



Bird baths, whether as shown on Plate 146, figure I, or of the standard 

 type, are usually constructed of concrete, or marble or other stone. Pools 

 of the type shown on Plate 146, figures I and 2, are usually constructed of 

 concrete (reinforced when under severe climatic and soil conditions). Such 

 pools may be entirely of concrete or may be veneered on the inside of the 

 pool with brick, stone or tile. Informal pools and pond areas, such as 

 shown on Plate 146, figure 4, are usually constructed of concrete, reinforced 

 where climatic conditions require this precaution. It is seldom that such 

 pools of an informal character are veneered with any material. 



Excavation for pools. The first step in the construction of any pool is to 

 set stakes to indicate definitely the correct lines and grades for the location 

 of the pool and for the proposed elevation at the top of the coping sur- 

 rounding the pool. After stripping the topsoil over the site, the area of the 

 pool should be carefully excavated to conform to the proposed lines of the 

 finished subgrade as shown on Plate 146, figures 2, 3, 4. The depth of this 

 excavation will vary with the water depth required in the proposed pool. 

 The bottom of the side walls surrounding the pool should be below the 

 line of normal frost action if permanent construction is desired. Oftentimes 

 pools are constructed where this wall does not extend so deep, but this is 

 not advisable. The area excavated for the pool should, in heavy clay soils 

 and under severe climatic conditions, extend at least 10 to 12 inches beyond 

 the outside face of the surrounding walls in order to allow for a proper 

 back-fill of cinders to provide necessary drainage. The excavation for any 

 pool should extend to a solid subgrade, and only in exceptional conditions 



