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public is an involved problem and the financing of such facilities is an area of great controversy. Land owners developing property on high ground may be understandably reluctant to pay for facilities to protect neighboring property located in low-lying areas downstream. Public Agency Survey: A survey made in this study of 230 public agencies included the question of who customarily pays for the cost of detention facilities when required by the local jurisdiction. Table 5, Cost Allocation, is a tabulation of responses received. It is seen that land developers usually pay (59 yes) but that the local public agency sometimes pays (14 yes). Payment is also made jointly, in some cases, by the land developer and the public agency (26 yes). TABLE 5 Cost Allocation of On-Site Detention Facilities When Required by Local Jurisdictions Cost Borne by: No. of Public Al!encies Responding Yes No 59 6 14 30 Land Developers Public Agency Jointly by Developer and Public Agency Other 26 24 3 10 Source: 1972 Survey of 230 Agencies by APWA Costs: An accurate estimation of the true costs of constructing, operating and maintaining storm water detention facilities is difficult. The type of facility to be used, storage requirements, geographical and geological conditions, cost of labor, material, and engineering all make the cost of detention facilities variable depending upon local conditions, probable future wages and the need to include both initial and future costs. For example, modification of roofs for rainfall detention may be cheaper than the construction of a pond in an area of high land costs, to provide the same total storage volume. But maintenance costs over many years may prove to be excessively high for roof storage, making pond storage cheaper over the lifetime of the project. Also, land availability and costs will play an important role in determining the cost of storage in open-space ponds. Thus, instead of itemizing costs, it is more useful to list those types of costs that should be considered when designing a detention facility. Thes(\ include the following items: I. land costs for storage basins or ponds, 2. excavation and -grading costs for ponds and basins on ground surfaces, 3. erosion protection measures for detention ponds and channels, 4. fencing and/or other security and safety measures for ponds, 5. pumping facilities and associated energy costs (often the major cost of operation for pumped-storage ponds), 6. installation of inlets, outlets and sewers to and from detention areas, 7. cost of added facilities to enhance the multiple-purpose use of detention areas, 8. cost of modifications of existing urban features to accommodate detention facilities (such as regrading and paving streets, installation of bridges, etc.), 9. cost of hydraulic control facilities to limit outflow, 10. cost of spillway structures to handle rare rainstorms, 11. landscaping of ponds in open spaces, 12. engineering and landscape architecture, 13. operation and maintenance, 14. costs of modifying rooftops, parking lots or plazas, 15. administrative costs, and 16. financing costs. Some of these costs will not be applicable to certain situations, and other cost items may possibly be reduced by incorporating stormwater detention storage in the original land development plans. The cost of providing rooftop storage will be minimized if the storage can be designed into the building prior to construction, rather than added after construction. Estimation of the amount of various cost items would be carried out by methods used in estimating costs for other types of construction. Land costs are by far the largest expenditures for open-space detention ponds and basins. In the case of a detention basin being considered for northeastern Illinois, for 22