. Bulletin. Science. 24 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 40000 2 30000 u 1 E 25000 20000 15000. Year Fig. 2. Yearly mass emissions for total suspended solids, Districts' ocean outfall July 1977 to June 1994. erates a 8 km long, multi-port (500) diffuser, ocean outfall, daily discharging X 108 1 of treated (50% advanced primary and 50% secondary) domestic (80%) and industrial (20%) effluent on the San Pedro Shelf (Fig. 1). From 1977 through 1994 approximately X 105 t of total suspended solids (TSS) have been dis- charged from the outfall to the shelf (Fig. 2). While treatment ch
. Bulletin. Science. 24 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 40000 2 30000 u 1 E 25000 20000 15000. Year Fig. 2. Yearly mass emissions for total suspended solids, Districts' ocean outfall July 1977 to June 1994. erates a 8 km long, multi-port (500) diffuser, ocean outfall, daily discharging X 108 1 of treated (50% advanced primary and 50% secondary) domestic (80%) and industrial (20%) effluent on the San Pedro Shelf (Fig. 1). From 1977 through 1994 approximately X 105 t of total suspended solids (TSS) have been dis- charged from the outfall to the shelf (Fig. 2). While treatment changes caused a major reduction in discharge of TSS between 1982 and 1983, mass emissions of TSS have been relatively stable from 1985 through 1994 hovering about X 104 tyr1 (Fig. 2). The Districts applied for a National Pollutant Discharge Elimination System (NPDES) permit under Section 301(h) of the Federal Clean Waters Act (CWA) to discharge wastewaters, which have received less than full secondary treatment. As a part of its 301 (h) monitoring program, the Districts have conducted an extensive series of studies on the potential effects of wastewater discharges on the ocean habitat. Results of these studies are presented in detail in annual reports and publications (Districts 1988, 1990, 1991, 1992, 1993, 1994; Gerlinger et al. 1993; Robertson et al. 1993). These accounts include descriptions of a large set of annual and seasonal sediment samples. In view of the 1000s of tons of TSS released via the outfall to the shelf, this discharge may be expected to alter the sediment properties of areas adjacent to the outfall. The purpose of this account is to describe long-term changes in sediment properties from the study area. The hypothesis tested here is that the Districts' ocean outfall has not significantly altered local sediment properties through time (1985-1993). Methods Field.—All benthic sampling used a modified Van Veen grab ( m2). Station locations were determine
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