The Cherry Creek Reservoir in the Denver Metropolitan area is subject to the Cherry Creek Reservoir Control Regulation ͑control regulation͒, which establishes a total maximum annual load for the reservoir of 6,473 kg ͑14,270 lb͒ of phosphorus. The load is distributed among phosphorus sources including background, nonpoint, and regulated storm water, municipal and industrial wastewater facilities, individual sewage disposal systems, and industrial sources. As a part of the control regulation, the Cherry Creek Basin Water Quality Authority ͑CCBWQA͒ is authorized to implement and maintain a trading program that allows phosphorus trading and the sale of phosphorus ͑kg/lb͒ in the Cherry Creek watershed. The trading program allows dischargers seeking new or increased phosphorus waste load allocations to obtain additional kilograms/pounds of phosphorus by constructing nonpoint source projects meeting certain criteria to immobilize phosphorus. This paper provides an overview of the CCBWQA trading program guidelines and describes two Arapahoe County Water and Wastewater Authority ͑ACWWA͒ trade credit projects: Lone Tree Creek Pond L-3 and Windmill Creek Pond W-6/W-7. The Pond L-3 and Pond W-6/W-7 projects are unique because they are the first two ͑and only two to date͒ projects that have successfully obtained trade ratios and estimated trade credits under the CCBWQA trading program. This paper describes the administrative and technical process for determining trade ratios and estimating trade credits for nonpoint-source-to-point-source phosphorus trades in the Cherry Creek watershed. The process for going from an established trade ratio and estimated trade credits to actual trade credits applied to a point source discharge presents its own set of challenges. Actual trade credits must be demonstrated by monitoring, which can be very expensive. The monitoring results must be reviewed and approved by CCBWQA before trade credits are awarded, and the Colorado Department of Public Health and Environment Water Quality Control Division must amend the facility's discharge permit before additional phosphorus can be discharged. Therefore, establishing a trade ratio and estimating trade credits for CCBWQA approval of a phosphorus trading project is only the first step in a potentially expensive and time-consuming process for actually discharging additional phosphorus through a nonpoint-source-to-point-source trade in the Cherry Creek watershed.

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The main aim of this research was studying the water routes and engineering of the aqueducts serving ancient Pompeii, with particular attention to the Aqua Augusta of the Campania region. We performed a study of the topography between the caput aquae in the nowadays village of Serino and Pompeii by means of field GPS investigations. The Aqua Augusta was arguably built between 33 and 12 BC, under the Emperor Augustus. It crossed hilly terrain with channel gradients that varied and, consequently, impacting hydraulics. A flow of at least 1,000 litres per second was estimated. A great portion of the Aqua Augusta was engineered to be tunnelled under the hilly terrain, with some sections as much as 65 to 97 metres below the existing grade