Stormwater Treatment ; Prohibits certain stormwater treatment & net improvement activities; requires DEP to require specified documentation for issuance of environmental resource permit for regional stormwater management systems; provides requirements for environmental resource permits authorizing such systems; authorizes certain permit applicants to purchase & use certain pollution reduction allocations & water quality enhancement credits; requires DEP & water management districts to use specified information to establish drainage areas; provides that certain use of enhancement credits constitutes stormwater treatment; provides that certain pollutant load reductions may not be referred to as enhancement credits; requires DEP to file specified rules for adoption by specified date; provides for water quality enhancement provisional permits; provides for modification of such permits under certain conditions; requires DEP & water management districts to recognize enhancement credits established in provisional permits; clarifies types of mitigation measures for compensating stormwater treatment which DEP or water management district governing boards must consider.