Purchase order EP15W000281SWCA, INCORPORATED

Description of requirement

THE PURPOSE OF THIS REQUISITION IS TO SECURE HYDROLOGIC AND WATER-QUALITY MONITORING EQUIPMENT FOR THE BARNSTABLE AND CHATHAM BIORETENTION BEST MANAGEMENT PRACTICES. THE EQUIPMENT PURCHASE WILL HELP MEET THE FOLLOWING GOALS: EVALUATION OF BMP PERFORMANCE. THE PRIMARY GOAL OF THE MONITORING PROGRAM IS TO EVALUATE THE PERFORMANCE OF THE BIORETENTION CELLS FOR STORMWATER TREATMENT. ACHIEVING THIS GOAL REQUIRES THE CONSTRUCTION OF ACCURATE WATER AND MASS BALANCES AROUND EACH BIORETENTION CELL. THE VARIABILITY OF QUALITY AND QUANTITY OF STORMWATER INFLOW CREATES CHALLENGES WITH RESPECT TO CONSTRUCTING MASS BALANCES, AND THUS WE HAVE RECOMMENDED A SYSTEM WITH REDUNDANT MEASUREMENTS OF FLOW IN ORDER TO ASSURE ACCURATE MEASUREMENTS OF THE INFLOWS TO AND OUTFLOWS FROM THE BIORETENTION CELL. CHARACTERIZATION OF WATERSHED LOADS. AN ADDITIONAL GOAL OF THE MONITORING IS TO MEASURE THE LOAD OF NUTRIENTS AND OTHER NONPOINT-SOURCE POLLUTANTS FROM THE WATERSHEDS SERVED BY THE BMPS. THE BMPS ARE DESIGNED TO TREAT LOW TO MEDIUM FLOWS AND IT IS EXPECTED THAT STORMWATER WILL BYPASS THE CELLS DURING INTENSE STORMS. THUS, MEASUREMENTS OF THE WATERSHED LOAD WILL PUT IN CONTEXT THE CONTRIBUTION OF THE BMPS TO ADDRESSING NONPOINT-SOURCE POLLUTION FROM THE WATERSHED. WE VIEW THE MONITORING REQUIREMENTS FOR THIS COMPONENT TO BE LESS STRINGENT THAN THOSE FOR EVALUATING BMP PERFORMANCE THE GOAL HERE IS TO PUT BOUNDS ON THE MAGNITUDE OF THE VARIABLE WATERSHED LOAD, WHICH DOES NOT REQUIRE THE SAME ACCURACY AS CONSTRUCTING WATER