2:01pm | The health of waterways in Long Beach took a nose dive over the past year, according to Heal the Bay and its 21st annual Beach Report Card, which states that the city’s water quality fell by 40 percent in 2010-11 compared to the previous year.

The contaminated waters of Colorado Lagoon received the lowest grade among local waterways, garnering an “F” for both the lagoon’s north and south testing locations, according to the report.

As the Long Beach Post recently reported, thanks to a recent $3.3 million state grant, the city plans to soon begin the final phase of mitigation efforts at the lagoon, which is slated to be be dredged to rid its waters of about 55,000 cubic yards of contaminated sediment. This grant is in addition to another grant the state had previously awarded the city for lagoon cleanup efforts.

The lagoon’s water quality is so bad that it made Heal the Bay’s “Beach Bummer” list, which identifies the 10 beaches in the state with the worst water quality. The lagoon is ranked as the ninth worst in the state.

Additional testing spots in Long Beach that scored poorly include the stretch of beach between Molino and Coronado avenues, Alamitos Bay and Mother’s Beach. The first two sites each earned a “D,” while Mother’s Beach received an “F.”

Of the city’s 15 beach testing locations, only four received a grade of “A” or “B.” Heal the Bay notes that the city struggles with water quality because Long Beach sits adjacent to the outlet from which the polluted waters of the Los Angeles River spit out into the ocean.

“Extensive studies throughout the city have demonstrated that the Los Angeles River, an enormous pollution source because of its nearly 1,000-square-mile drainage, is the predominant source of fecal bacteria to Long Beach waters,” the report states.

The report also mentions that the city’s investigations into pollution sources revealed various leaking or disconnected sewage pump lines and improperly working storm drain diversions, which have all been repaired. The city has even installed what the report labels “an innovative pilot technology” that disinfects runoff in the storm drains.

Regardless, Heal the Bay is not so optimistic about Long Beach’s ability to improve the quality of water in its waterways.

“Ultimately however, most Long Beach water quality will be directly tied to rainfall amounts and runoff volumes from the Los Angeles River,” the report states.

Though not mentioned in the report, the city’s breakwater is an additional culprit. The man-made barrier traps urban runoff and stormwater from the Los Angeles River inside the harbor. Normally, the ocean’s current and waves would naturally cleanse the coastal waters and prevent water contaminated with chemicals and other pollutants from stagnating.

The large dip in water quality in Long Beach last year could be attributed to the higher-than-average amount of rainfall the city experienced over the last 12 months; the report states that each of the city’s 15 testing sites received an “F” every time tests were conducted directly following a period of precipitation.

The report card grades the water quality at beaches located along the coastline of California, Oregon and Washington. This year is the first time Heal the Bay has included the latter two states. The letter grades “A” through “F” are assigned to beaches based on the risk of adverse health affects to beachgoers, which is determined by measuring the fecal bacteria pollution concentration in the water.

The water quality tests used to grade Long Beach beaches are conducted between April and October as mandated by the state. The report notes that the city’s Environmental Health Division historically tested the water at 25 sites on a weekly basis. The city has tested the water at 10 fewer sites for the past two years due to cost-cutting measures, according to the report.

Click here to download a .pdf copy of the full report.