The City of Manteca is on a roll.Sales tax receipts are up 10 percent to $8.8 million and are projected to reach $11.3 million in the next 12 months.Property tax receipts are up 9 percent to $12.3 million are projected to reach $12.7 million in the next 12 monthsMotel room tax receipts are up 14 percent to $908,000 and are projected to reach $999,000 in the next 12 months.Overall general fund revenue is expected to be high enough in the next fiscal year starting July 1 to underwrite a spending plan for day-to-day services of $35,331,915. That represents a 5.2 percent increase over the current fiscal year budget of $33,571,826. Once all municipal spending such as the enterprise accounts covering water, sewer and garbage as well as restricted and capital improvement funds are factored in, the overall proposed budget for next fiscal year is $161,899,802.It is against that backdrop that the city council is conducting a budget workshop today at 2 p.m. at the Civic Center, 1001 W. Center St.And while the city has managed to established reserves aimed at cushioning against another economic downtown as well as replacement of costly items and for emergencies, Manteca still faces significant financial challenges.The California Public Employees Retirement System has made it clear that cities will be required to increase contributions in the coming years to keep the retirement fund solvent.The sustainability of the Development Services Fund covering economic development and community development costs that has been an issue since the loss of redevelopment agency funding.The sustainability of the solid waste fund that saw its last garbage rate increase in May 2004.