Kaštelanski zaljev je zbog neriješenog sustava prikupljanja i obrade komunalnih i industrijskih otpadnih voda gradova Trogir, Kaštela, Solin i Split dugi niz godina bio jedan od najopterećenijih zaljeva u Sredozemlju s izrazito negativnim pojavama eutrofikacije i onečišćenja. U svrhu poboljšanja ekološkog stanja u zaljevu provodi se integralni projekt zaštite Kaštelanskog zaljeva (Eko-Kaštelanski zaljev) koji osim rješenja otpadnih voda obuhvaća i dogradnju i poboljšanje vodoopskrbnih sustava gradova Splita, Solina, Kaštela i Trogira. U okviru tih aktivnosti otpadne vode grada Splita koje su ispuštane u Vranjički bazen preusmjerene su krajem 2004. godine novoizgrađenim podmorskim ispustom u Brački kanal.. U okviru programa „Praćenje utjecaja podmorskog ispusta Stobreč na okoliš“, koji  provodi Institut za oceanografiju i ribarstvo Split za potrebe Vodovoda i kanalizacije d.o.o. Split, obavljaju se ispitivanja fizikanih, kemijskih i bioloških parametara, te ispitivanja sanitarne kakvoće mora. U radu su prikazani rezultati monitoringa koji ukazuju na značajno poboljšanje stanja u Kaštelanskom zaljevu, a s druge strane stanje kemijskih i bioloških parametara u području Bračkog kanala nakon puštanja podmorskog ispusta u rad je uglavnom nepromijenjeno u odnosu na ranija istraživanja („nulto stanje“)..; Due to the unsolved system collection and treatment of urban and industrial wastewater of the towns Trogir, Kaštela, Solin and Split, the Kaštela Bay has long been the one of the Mediterranean bays with the highest loads and significantly negative occurrences of eutrophication and pollution. With the aim of improving the ecological status in the bay, the project of integrated protection of the Kaštela Bay (Eco Kaštela Bay) is implemented, which, besides wastewater solution, also includes extension and improvement of water supply systems of the towns Split, Solin, Kaštela and Trogir. As part of these activities, wastewater from the town Split, which had been discharged into the Vranjic Basin, was redirected through a newly constructed submarine outfall into the Brač Strait at the end of 2004.. As part of the programme “Monitoring of Environment Impact of the Submarine Outfall Stobreč”, Which is carried out by the Institute of Oceanography and Fisheries Split on behalf of the Water Supply and Sewerage Company VIK d.o.o. Split, investigations are carried out of physical, chemical and biological parameters as well as marine water quality. The paper presents the monitoring results which indicate a significant water quality improvement in the Kaštela bay, but generally show no change of the state of chemical and biological parameters in the Brač Strait with regards to the earlier investigations (“zero state”) after the submarine outfall became operational.