Los Peñasquitos Marsh Natural Preserve and Lagoon is a coastal marsh in San Diego County, California, United States situated at the northern edge of the City of San Diego, forming the natural border with Del Mar, California.Torrey Pines State Preserve , 2008 This bar-built estuary divides a colony of the endangered Torrey pine on a narrow coastal strip.C.Michael Hogan (2008) Torrey Pine: Pinus torreyana, Globaltwitcher, ed. Nicklas Stromberg Three streams empty into the lagoon: Carroll Creek, Carmel Creek, and Los Peñasquitos Creek, with a total drainage basin area of 95 square miles.
Names The name "Los Peñasquitos" is Spanish for "The Little Cliffs" or "crags". Previously the lagoon was also called Cordero Slough or Cordero Delta (named after late 18th century settlers), Soledad Lagoon, Torrey Pines Lagoon, and Sorrento Lagoon.
Physical and natural aspects The mouth of Carmel Creek is in the northern part of the lagoon, Los Peñasquitos and Carroll creeks flow through the Los Peñasquitos Canyon and Carroll Canyon respectively, then merge in Sorrento Valley and drain into the lagoon from the south. Los Peñasquitos Creek has by far largest drainage area (about 70% of the total basin). Historically, the streams were seasonal, usually drying out in summer. After urbanization of the surrounding areas the streams became perennial due to the irrigation runoff with winter flows to summer flows ratio from 16:1 (Carmel Valley Creek) to 58:1 (Los Peñasquitos).
The wetlands inside the lagoon are spread over about 500 acres.
Historical configurations Due to the fast rise of the sea level at the end of the last glacial period (6000 years BP) the lagoon became a deep bay with the rocky shores. As the sea level rise slowed down, the sediment carried by the streams started to accumulate, and the sandy beaches appeared around 4000 years BP. With sea level stabilization, the lagoon by 3600 years BP turned into a brackish marsh and by 2800 years BP became a salt marsh.
Until the late 19th century, the lagoon went inland for as much as 1.75 miles, its salt marshes, salt flats, and mud flats/open water occupied approximately 380 acres, with salt marshes constituting about 72% of the area. The lagoon was almost separated from the ocean by the sand and dune barrier that was about 300 feet wide and up to 30 feet high. Few tidal channels merged into a single large channel at the northern part of the beach. Historically, the mouth of the channel (inlet of the lagoon) was open and closed intermittently. A "high wall composed of small rocks" was located along the beach side of the lagoon (the route of the modern North Torrey Pines Road). This barrier was mined for cobbles that were used to pave the streets of San Diego.
Human impact Most of the freshwater entering the Los Peñasquitos Lagoon arrives from Los Peñasquitos Canyon via Los Peñasquitos Creek. For many years, the Los Peñasquitos Lagoon had evolved from a tidal estuary to a lagoon that was closed to tidal action for long periods of time. Since becoming a part of the State Park System, there have been a number of changes that have increased the tidal action within the lagoon.
History
During the prehistoric period, as early as 6000–5000 years BP, the Kumeyaay tribe collected scallops, chione clams, and oysters in the area; few archeologic sites exist around the lagoon, including the village of Ystagua (existed since 1300 BP) in the modern-day Sorrento Valley.
In the 19th century the valley was used for crops, with Rancho Los Peñasquitos being the first land grant (1823) within the limits of the modern San Diego County. First railroad line, a California Southern Railroad link between National City and Oceanside passed through the eastern part of the area in 1881–1882, with a "Beach Shingle" spur line (also known as “Sea Wall Spur”) running on the north side to the beach in order to transport the construction materials used to pave the streets in San Diego. The new Santa Fe Railroad line went through the center of the lagoon in early 1900s, and Pacific Coast Highway in 1912-1915 (the latter was expanded in 1932–1933, with “Sorrento Overhead” providing a railroad overpass). In 1965–1967, Interstate 5 was built, North Beach parking lot followed in 1968. As a result, three transportation links intersect the lagoon: Highway 101 runs along the beach on the western side, Santa Fe Railroad line crosses in the center, Interstate 5 lies in the east.
Freshwater inflow The urbanization of the surrounding area caused an inflow of fresh water in the summer months due to irrigation runoff ("urban drool"), the resulting changes in habitat were beneficial to mosquito Culex tarsalis, a carrier of the encephalitis and West Nile virus diseases.
Railroad causeway Originally, the railroad tracks travelled straight from Sorrento Valley on the eastern side of the Lagoon and ran parallel north of what is now Carmel Valley Road, therefore the impact on the tidal circulation and the mouth was much smaller than for the other lagoons nearby. However, in 1925, the Santa Fe Railroad built a single-track roadbed causeway embankment down the center of the lagoon for its Surf Line, which still is in use today on a daily basis by the Coaster and Pacific Surfliner as well as BNSF Railway freight trains. This embankment severely restricted the normal historical lagoon drainage for the first time, and changed the tidal flow and current pattern. The four original wooden trestle bridges crossing the lagoon (three over the water and one over the McGonigle Road) were replaced between 2015 and 2017 with new concrete bridges to help modernize the railroad traffic to and from San Diego. Even though the bridges were replaced, this area was not double-tracked because it is possible that these tracks will eventually be bypassed by a two-track tunnel underneath Del Mar.
Highway 101 When the Pacific Coast Highway (U.S. Route 101 in California) was expanded in the 1930s, the roadbed along the beach was heightened, and a bridge was built over the mouth the lagoon. This bridge had many wooden pilings that easily got clogged with sand and debris, impacting the water transfer between the ocean and lagoon.
Sewage treatment effluent Over the years, at least three different waste water treatment plants have pumped their treating effluent into the lagoon. The Callan Treatment plant pumped per day during the 1950s; the Sorrento plant produced per day starting in 1962; and the Pomerado Waste Water Treatment Plant pumped treated sewage into the lagoon from 1962 to 1972.
North Beach Parking Lot The triangular North Beach Parking Lot was built in 1968. It is accessible via Carmel Valley Road at McGonigle Road / Del Mar Scenic Parkway, and is bounded on three sides by the arch bridge at North Torrey Pines Road, the railroad causeway, and the lagoon's ocean inlet. Previous to the State Park, there had been a number of tourist beach houses in the area, called Sunken City, that had been moved from the open beach during the 1932 construction of the large causeway for North Torrey Pines Bridge.
According to LPL Foundation and the State Coastal Conservancy, this fully paved parking lot significantly altered the lagoon's hydrology.
Sediment deposition Due to the high rate of sediment deposition that surpasses the federally-mandated total maximum daily load, Los Peñasquitos Lagoon is listed as a category 5 impaired body of water under section 303(d) of the Clean Water Act. This is primarily due to the adverse effects of sedimentation in the lagoon itself and also within its vast watershed. These effects include drops in photosynthetic productivity, higher concentrations of heavy metals, and overall loss of ecosystem biodiversity within the estuary. In addition to ecological impacts, sedimentation in the Los Peñasquitos watershed has led to significant issues within its storm water infrastructure. Specifically, sediment accumulation in flood control channels has greatly reduced original storm water conveyance capacity. This is primarily due to the vegetation that grows within the channels as a result of siltation. Regular maintenance of these channels by the Storm Water Division is therefore a necessity to ensure proper flood control. Despite the need for sufficient flood control through regular channel maintenance, the extensive permitting process involved requires selection and planning that extends nearly two years before any service activities.
Restoration and preservation M.H.S. Elwany in 2011 named the following main threats to the ecosystem of the lagoon: lagoon mouth closures cause increase of salinity (from brackish conditions to hypersaline), causing reduced biodiversity (for example, in the eastern part of the lagoon pickleweed displaces the California cordgrass); sedimentation increase due to greater water flow from the creeks. Deposits cause a loss of salt marsh, turning it into the coastal scrub or riparian habitat; increased freshwater runoff also reduces the salt marsh area, turning this habitat into the riparian or cattail marsh. Elwany named the following potential low-cost improvements: keeping the lagoon inlet open and excavating the main lagoon channel; these measures will increase the water circulation; creating new flow channels to divert the freshwater into the main channel; removing the deposits in the east of the lagoon and adding new tidal channels there; adding a catch basin for the freshwater runoff and pumping the water into the storm drain; removing the invasive plants; recreating salt marshes and salt pannes; reducing future sedimentation by either adding the sediment basins or improving the water management in the new developments in the area; decreasing the pollution through education of the populace; setting aside wildlife corridors.
California State Parks The California Division of Parks and Recreation has designated the status of Los Peñasquitos Lagoon as a State Preserve, which has much more restricted access than the State Park designation. There is very limited public use of Los Peñasquitos Marsh Natural Preserve, with most of the area signed as "Do Not Enter". The California State Preserve status is granted to only the rarest and most fragile of the state owned lands.
The State Preserve covers the saltwater lagoon area of over adjacent to Torrey Pines State Beach and Torrey Pines State Natural Reserve. An additional of marshland was added to this California State Parkland in 1987, when it was purchased from SDG&E for $2.25 million. SDG&E has originally purchased the land in 1966 as a possible site for a new nuclear power plant that was never built.
Los Peñasquitos Lagoon Enhancement Plan In 1985, the California Coastal Conservancy created the Los Peñasquitos Lagoon Enhancement Plan to deal with a number of human-caused problems. A lagoon management program is now in place to monitor water quality, manage the manual removal of sand and debris upon lagoon mouth closures, give oversight and recommendations for improved usage, and coordinate with other agencies to protect and restore the lagoon.Annual Report for Los Peñasquitos Lagoon Foundation (2001) The Los Peñasquitos Lagoon Foundation, formed in 1983, is 501 3(c) non-profit and is the management entity charged with implementing the enhancement plan in coordination with State Parks and the State Coastal Conservancy. More information on Los Peñasquitos Lagoon and its watershed, the Los Peñasquitos Lagoon Foundation (LPLF) and resource management within the lagoon and its watershed can be found at the following website: lospenasquitos.org
Managed breaches