Reports
Optimization of ground-water withdrawals from the Lower Patapsco and Patuxent aquifers in the Bryans Road Service Area, Charles County, Maryland
2004, Andreasen, D.C.
Administrative Report
Abstract
The main objective of the study was to minimize drawdown in the Lower Patapsco aquifer while pumping the required rate needed for both current and projected demand. Minimizing drawdown reduces well operational costs. In addition to minimizing drawdown, water levels were constrained from falling below the 80-percent management level. Scheme 1: Optimum withdrawals in the Bryans Road well field to minimize total drawdown. If the existing wells in the Bryans Road well field are required to pump 0.64 million gallons per day by 2020, total drawdown is minimized when only Bryans Road Well 6 (CH Bd 58), screened in the Patuxent aquifer, is pumped. By 2020 drawdown equaled 151 feet in Well 6. Withdrawals from the Lower Patapsco wells, which were significantly less than the Patuxent pumpage at the start of the simulation, were reduced to zero by 2008.
Scheme 2: Optimum withdrawals in the Bryans Road and Strawberry Hills well fields to minimize total drawdown.
If the existing wells in the Bryans Road and Strawberry Hills well fields are required to pump 0.75 million gallons per day by 2020, total drawdown is minimized when only Bryans Road Well 5 (CH Bc 78) and Well 6 (CH Bd 58), both screened in the Patuxent aquifer, are pumped. Pumpage in Wells 5 and 6 equaled 0.013 and 0.72 million gallons per day, respectively, by 2020. By 2020, total drawdown equaled 277 feet in Wells 5 and 6. Withdrawals from the Lower Patapsco aquifer, which were significantly less than the Patuxent pumpage at the start of the simulation, were reduced to zero by 2009.
Scheme 3: Maximum withdrawals from the Bryans Road and Strawberry Hills well fields constrained by the 80-percent management level (Scheme 3A) and pump intakes (Scheme 3B).
A maximum of 2.2 million gallons per day can be withdrawn from the Bryans Road and Strawberry Hills well fields by 2020 without exceeding the 80-percent management level. Approximately 1.7 million gallons per day were withdrawn from the Patuxent aquifer in the Bryans Road well field and 0.46 million gallons per day from the Lower Patapsco aquifer in the Strawberry Hills well field. Withdrawals from the Lower Patapsco aquifer at Bryans Road were reduced to zero by 2013.
A maximum of 1.8 million gallons per day can be withdrawn by 2020 before exceeding pump intakes. Approximately 1.2 million gallons per day were withdrawn from the Patuxent aquifer in the Bryans Road well field and 0.59 million gallons per day from the Lower Patapsco aquifer in the Bryans Road and Strawberry Hills well fields. Withdrawals were constrained by pump intakes in all wells except Bryans Road Well 4 (CH Bd 50) where the design pumping rate was reached before water levels fell below the pump intake. Water levels fell below the 80-percent management level in the Lower Patapsco aquifer in a relatively small area just to the northwest of Bryans Road along the Potomac River.
Scheme 4: Maximum withdrawals from existing wells in the Bryans Road and Waldorf service areas constrained by the 80-percent management level (Scheme 4A) and pump intakes (Scheme 4B).
A maximum of 7.8 million gallons per day can be withdrawn by 2020 from existing wells in the Bryans Road service area and existing wells in the Waldorf service area (plus a proposed well at White Plains Business Park) when drawdown is constrained by the 80-percent management level. Approximately 1.7 million gallons per day were withdrawn from the Patuxent aquifer in the Bryans Road well field and 6.1 million gallons per day were pumped from Lower Patapsco wells in the Waldorf service area. The Lower Patapsco wells at Bensville, Dutton’s Addition, Eutaw Forest, Laurel Branch, Bryans Road, and Strawberry Hills, which are located near the outcrop area where less available drawdown occurs, were not pumped.
A maximum of 7.0 million gallons per day can be withdrawn by 2020 from existing wells in the Bryans Road service area and existing wells in the Waldorf service area (plus a proposed well at White Plains Business Park) when drawdown is constrained by pump intakes. Approximately 1.2 million gallons per day were withdrawn from the Patuxent aquifer in the Bryans Road well field and 5.8 million gallons per day were withdrawn from the Lower Patapsco aquifer (5.3 and 0.5 million gallons per day from the Waldorf and Bryans Road service areas, respectively). Water levels in the Lower Patapsco aquifer fell below the 80-percent management level in a relatively small area just to the northwest of Bryans Road along the Potomac River.
Scheme 5: Future Patuxent aquifer production wells in the Bryans Road service area optimized for minimum total drawdown under a hypothetical 2020 water demand of 3 million gallons per day.
Total drawdown is minimized when three out of six hypothetical wells were pumped along with existing wells at Bryans Road (Wells 5 and 6). Each hypothetical well pumped 0.72 million gallons per day. The optimum withdrawal rates at Bryans Road Wells 5 and 6 were 0.12 and 0.72 million gallons per day, respectively. A large cone-of-depression formed over much of the Bryans Road service area by 2020 as a result of the withdrawals. Total pumping head at the five sites equaled 2,824 feet. Available drawdown remaining by 2020 ranged from 85 feet at Bryans Road Well 5 to 272 feet at Hypothetical Well 2.
