I In order to fulfill drinking water necessity and increase the scope of drinking water service, PDAM Tirta Moedal Semarang city will design water treatment plant (WTP) at Pudakpayung with the capacity of 100 L/second by raw water supply from Garang River. The WTP design will be referred as the design and evaluation qualification from exixting WTP. The Intake consists of bar screen and water channel equipped with submersible pump for deliver water from intake well to coagulation unit. The coagulation unit will use hydraulic coagulation with the gradient velocity (G) being 1,257.6 /seconds and detention time (td) being 5.2 seconds. As for the planned flocculation will be using hydraulic flocculation with hexagonal-shaped tub consisted of 6 compartments with the gradient velocity (G) being 54 - 40/seconds and time detention (td) being 12 minute. The coagulant used in the institute is Chemical Mix Alum (CMA) with dosage of 40 mg/L. The sedimentation unit consists 2 tubs installed with tube settler. The planned filtration unit is a rapid sand filter consists of 4 tubs. As for disinfectant embellishment is using chlorine (Ca(ClO)2) with a dosage of 3.6 mg/L into the reservoir. The reservoir consist of a 2 round-shaped tub with the capacity 180 m3. The result of cost calculation planning WTP at Pudakpayung is Rp2,436,012,606.37. in other word, Rp 24,360,126.06 L/second.