A Nineteenth Century Zanja Complex at Los Peñasquitos Ranch House Adobe, San Diego County, California

By Susan M. Hector, Ph.D.


Archaeological and historical research began at the Los Peñasquitos Historic and Archaeological National Register District in the early 1980s, first under the supervision of Dr. Susan Hector, then Dr. Lynne Christenson, and through San Diego City College under the supervision of Dr. Stephen Bouscaren (Bouscaren et al. 2016). In recent years, the San Diego City College field class has been investigating the area south of the ranch house. The prehistoric and historic archaeological deposits associated with the ranch house have been recorded as a separate site, CA-SDI-8125. An important feature was discovered by Dr. Lynne Christenson in 1992, when she was teaching a field class at the site for San Diego State University. While exploring the foundations of the structure known as the lath barn to determine the function of the building, Dr. Christenson found a feature that was subsequently identified as a water conveyance channel, or zanja. The zanja extended from an artesian spring to the west, where it was obscured by the later construction of a duck pond. San Diego City College, under the direction of Dr. Bouscaren, continued the investigation of the zanja, and Dr. Bouscaren discovered a second zanja south of the one found by Dr. Christenson. These are referred to in this report as the northern and southern zanjas.

The 2014 field class, supervised by Dr. Susan Hector, excavated units at the west end of the southern zanja, completed units P5 and P5B, and initiated excavation at unit N10E03 (Figure 1). In addition, the northern zanja was mapped, photodocumented, and backfilled to preserve the feature. Dr. Hector also conducted extensive research in an attempt to provide further information on the zanja. The results of her research are presented in this report.

Brief History of Los Peñasquitos Ranch House National Register District

The archaeology and history of Los Peñasquitos Ranch House National Register District (listed in 2006) has been described in detail in numerous reports and publications (Christenson and Sweet 2008; Hector 1991, 1993, 2003; Hector and Van Wormer 1986; Ward 1984). Site SDI-8125 has been dated at 5,500 years before present, based on shell samples excavated from the midden deposit outside the northeastern end of the present building (radiocarbon dating at site SDI-5220 has yielded a date of over 7,200 years before the present). The site was continuously occupied by Kumeyaay Indians through Spanish settlement of San Diego.

In 1823, Mexican governor Luis Antonio Argüello granted Francisco Maria Ruiz two leagues of land in the canyon; the padres wrote a letter of objection to the governor stating that this land was used by the mission for sheep grazing, vineyards, and orchards (Oliva 1823). Nevertheless, Ruiz gained title to the land and archaeological excavations suggest that he built a small structure where the ranch house is now located. Ruiz deeded the land to Francisco Alvarado in 1837; Ruiz lived with the Alvarado family as he became older and less able to live on his own. Francisco deeded the land to his son, Diego, in 1857. Diego gave the land to his sister, Estefana, and her new husband George Johnson when they married. Johnson and his wife began expanding the existing buildings at the ranch in 1862, and by 1868 had plans to expand and enlarge the house and grounds (Daily Alta California, 13 November 1868, 1:4).

Johnson, who was referred to as Captain because of his role in navigation on the Colorado River at Yuma, Arizona, soon started to explore the development of the many springs on the property. In 1869, he was named as a trustee for the newly-formed San Diego Water Company (Sacramento Daily Union, 24 March 1869). He promoted the high volume of water from his springs through water surveys, which claimed that there was enough water to supply a city of 100,000 (San Diego Union Weekly, 4 April 1871). There was continuing discussion of using the Peñasquitos watershed to supply the city or a new community; dams and reservoirs could be built by taking advantage of natural basins (The Daily World, 25 September 1873).

He built a reservoir, or “tank”, between the adobe ranch house and the creek; a spring flowed into the reservoir, and then into the garden from the overflow (San Diego Union Weekly, 28 April 1869; San Diego Union Weekly, 4 April 1871, 4:3,4; The Daily World, 24 September 1873, 3:1,2). Johnson also built a spring house around the spring nearest the reservoir (The Daily World, 24 September 1873, 3:1,2).

But every few years, the springs would mysteriously dry up. On some occasions, it was due to earthquakes, which were mentioned as the cause of irregular water flow (Bangor Daily Whig and Courier, 17 April 1872). Over time, the fickle nature of the springs in the valley prevented reliable development of the water resources on the ranch.Due to a series of financial setbacks, the Johnsons had to sell the property and in 1880 Jacob S. Taylor obtained title. Taylor added some outbuildings, Victorian decorations, and attempted to subdivide and promote the ranch as an ideal place to settle. He even continued to promote the ranch as a water source for the growing region. In 1881, there was a proposal to build a dam 50’ high and 300’ wide to hold 100,000 gallons of water for farms (San Diego Union, 8 May 1881, 1:4). Taylor was as unsuccessful as Johnson in developing the water resource potential of the valley.

In 1910, Charles Mohnike obtained the property, and the wooden portions of the ranch house burned in 1911-12 due to a kitchen fire. Mohnike rebuilt the structure. Subsequently, the ranch was used as a bunkhouse and residence, but was vacant when the County of San Diego acquired the land around it in 1980. Archaeological investigations under the direction of Dr. Susan Hector began in the fall of 1983 when the County started restoration and stabilization of the adobe buildings. It was during these excavations that earlier structures were identified underneath the existing buildings.

Chronological Framework for Archaeological Investigations

Historical and archaeological data have been collected from Los Peñasquitos Ranch House site SDI-8125 for 30 years. Although the preservation of archaeological data is good throughout the site, the deep history of occupation has resulted in challenges to stratigraphic interpretations. Later construction impacted earlier archaeological deposits; this construction was then itself impacted by even more recent development. Of significance for the archaeological work undertaken by City College, the 19th century excavation of the trenches for the zanjas penetrated the prehistoric deposits at SDI-8125, resulting in anthropogenic soils thousands of years old being dumped on top of the ground surface and eventually being incorporated into the complex archaeological record of the site. A chronological framework for interpretation of the recovered materials is critical to understanding the site. The field class continues to excavate in arbitrary and cultural stratigraphic levels, but the research takes into consideration the different cultural and chronological periods of occupation.

Interpretation would be a simple matter if the many periods of occupation and history at the site were neatly arrayed in order, with the earliest period represented by the deepest archaeological deposits. However this is not the case in most locations at SDI-8125. Careful excavation and attention to soil color changes, old trenches and soil disturbance, feature outlines, and mapping are necessary at the site. In addition, the author has developed a chronological framework for interpretation of the archaeological data recovered from the site, using archaeological (Hector and Van Wormer 1986) and historical (Ward 1984) data:

Date                             Period                                      Remarks

+7200 – 1200 BP        Archaic                                    Native; C14 date of 7,200 BP from SDI-5220

1200-200 BP               Late Prehistoric                                   Native; pottery, arrow points

AD 1800-1823                        Contact/Spanish/Mission          Mission and Native use of land

AD 1824-1862                        Mexican                                   Ruiz and Alvarado ownership

AD 1862-1880                        Johnson                                   George Johnson and family

AD 1880-1913                        American I                               Taylor, Mohnike and other owners

AD 1913-1962                        American II                             Use of adobe for ranch barracks

Archaeological materials and features have been found from all seven chronological periods present at the adobe. The Johnson period represents the major construction efforts conducted at the site, and is the most completely documented. The Contact/Spanish/Mission period is the least documented.

Personnel Participating in the 2014 Field Class Excavations

In addition to the professor, Dr. Susan Hector, and the Laboratory and Field Technician, Amy Ross, six San Diego City College students participated in the field class:

Christian Allen

Jose Lemus

Michelle Magnuson

Catherine Terry

Robert Thomas

Celena Westberry

Several volunteers with field class experience participated in the excavations:

Pepe Aguilar

Alec Apodaca

Mikhail Echavarri

Samantha Gartner

Max Gonzalez-Flores

Kirstie McPeek

Sonia Mendoza

Vanessa Rigby

Hector Valtierra (GIS Studies)

Mr. Apodaca was present as a volunteer for most of the work days and assisted in expediting the completion of the units as well as backfilling. Mr. Valtierra and Mr. Echavarri were students in a GIS class at another community college and conducted mapping of the excavation area. Mr. Echavarri stayed on as an excavation volunteer, and was present during most of the work days. The participation of the volunteers was critical to the success of the field class.

Description of Field Work

The focus of the Spring 2014 field class was to complete and backfill the remaining open units, continue to explore the southern zanja, and identify any other features or outlying deposits that could be associated with the zanja or Contact/Spanish/Mexican period at the ranch.

All units excavated were 1 x 1 meter in size and were excavated in 10 cm arbitrary levels. Soils were passed through 1/8th inch mesh hardware cloth. Students were directed to collect all cultural materials that could be picked out of the screens. Depth measurements were taken from a datum corner of the unit. Level records were completed for all levels excavated, and photographs were taken at the completion of most levels (unless no stratigraphic differences could be noted). All units were photographed in profile and plan when completed, prior to backfilling. Students were required to complete field notebooks, detailing their daily activities. These notebooks are on file at City College. A detailed report of the field studies and lab analysis is included in Hector (2014).

Disturbance by burrowing animals (squirrels and gophers) is a continual issue at SDI-8125. The soft midden soils provide easy access for the activities of these small animals. It is not unusual to return to the site after a week to find a cubic foot of spoils from a burrowing animal intruding into the unit. On occasion this activity would result in a collapsed sidewall. The soil from animal burrowing and collapsed walls was screened separately and artifacts were included in the catalog although exact provenience was not possible. Ironically, several significant artifacts were found in the screened burrow spoils.

Chronological Considerations: The Contact/Spanish Mission Period

Two discoveries were made that provide chronological information about the early historic period at SDI-8125. The first is glass trade bead found in a zanja unit. The second consists of fired brick features found in several locations.

Trade Bead. At the 40 cm level in unit Z58, a large, dark blue bead was found under a cobble adjacent to the south wall of the zanja. The bead appeared black initially, but when held up to the light it was dark blue (Photograph 1).


Photograph 1. Russian Blue trade bead.

It had facets covering the surface, and one hole was larger than the other. The length of the bead was 6/10 inch/1.5 cm and the width was 6.5/10 inch/1.7 cm. The larger hole was 0.4 cm across, and the smaller hole was 0.05 cm across. The bead had five rows of facets; two longer facets on the ends with 3 shorter rows along the equator of the bead. Research indicated that this bead is commonly referred to as a Russian Blue trade bead, and was associated with sites in California dating to AD 1800 – 1840.

Although referred to as a Russian Blue bead, the beads were actually made in Bohemia from molded glass. The presumed intent was to imitate crystal beads. The Spanish as well as the Russians traded these beads throughout North America.

In an attempt to standardize historic era bead typologies, Clem Meighan developed a classification system with examples from archaeological sites (Meighan 1953). The beads are now located at the Phoebe A. Hearst Museum of Anthropology at UC Berkeley. Because many of the beads are associated with burials and human remains, working with the actual examples is sensitive. The Museum provided the author of this report with a spreadsheet of the collection, which was used in addition to Meighan’s manuscript to assign the bead from unit Z58 to a type. The closest type of bead was Meighan’s type 140, an oblate spheroid with 5 rows of facets. In his example, one of the holes was larger than the other (Hearst Museum catalog #1-39786). It was from a collection of 109 trade beads found at CA-YOL-13. According to Moratto (1984: 214), material from this site has been dated at AD 650-1150. There must have been a later, historic era occupation that has not been analyzed or documented.

Russian Blue trade beads are commonly found at early historic sites throughout California, particularly in the northern part of the state. In his analysis of glass beads from Santa Ines Mission, Ross (1989) refers to these as Class MPIIa type beads. He noted that the earliest form was found at Fort Vancouver (1829 – 1870). At Mission Santa Ines, the beads were associated with Phase III (1836 – 1870). At San Buenaventura Mission, Gibson (1976) identified several cobalt blue faceted beads, and associated them with Meighan’s types 150, 146, 373a, and 338. The deposit where these beads were found was dated 1785 – 1816. Gibson noted that cobalt faceted beads were also found at the historic portion of the Malibu Creek site, and at Medea Creek.

Motz and Schulz (1980) stated that the beads were traded by the Russian-American Fur Company along the northwest coast in the late 1700s – early 1800s. The beads show some variability in size and color, although they are usually dark blue. However, they can be green, red, or lavender. The size and number of facets also varies. Similar types of beads were dated to 1833 – 1884 at other sites. Sorenson and LeRoy (1968: 45) show Russian Blue trade beads as their examples 71 and 72, and noted that a dark green faceted bead was found along the Southern Immigrant Trail in San Diego’s San Felipe Valley. Interestingly, a dark green example was identified in the San Diego Museum of Man collection from SDM-W-150, La Rinconada de Jamo, which is located in Pacific Beach (Michael Sampson, personal communication, 2014).

Five historic period beads were found in Room A2 at Los Peñasquitos during excavations conducted prior to restoration of the building (Hector and Van Wormer 1986: 97). The beads were dated to 1785 – 1816, and were within a deposit with Mexican-period artifacts such as Majolica pottery. None of the beads found in Room A2 was like the faceted bead found in 2014; three were oblate spheroid translucent green cane beads, one was a large barrel-shaped translucent cobalt blue cane bead, and one was a disc-shaped translucent blue wire bead. A similar cobalt blue faceted bead was found at archaeological site SDI-12925, Locus 4, by the author (Hector 2004:172). The bead was observed on the ground surface near milling features. This site is located on Volcan Mountain, an area occupied by native people into the mid-1800s.

A question remains about whether the bead at Los Peñasquitos was associated with the Native American or the early historic era occupation. Its location next to the southern zanja, which appears to be the older feature based on its materials and architecture, could be evidence for association with the historic period, perhaps the earliest Mexican occupation of the site in 1823. However, the beads were commonly traded to Native people throughout the state and are often found in archaeological deposits associated with those groups. Gibson noted that the Natives were often paid in beads for their labor (1976: 127), and that J.P. Harrington said that the European beads were used as money by the Natives after shell money was no longer accepted (1976: 128).

Bricks and Ladrillos. Soft red bricks, often referred to in San Diego as “Mormon” bricks, were found in situ on the surface in unit N10E03. Broken pieces were also found loose in the unit in the midden deposit. They are referred to as “Mormon” bricks because the first know brick production in San Diego was undertaken by two retired Mormon soldiers, who made the bricks in 1847 for Juan Bandini (May 1982: 255). Thomas Whaley produced his own bricks in 1856, which were of a different appearance and consistency. These American bricks are typically granular and crumbly, have rounded edges, and are not as well fired as bricks made in the later 19th century. They are also smaller in size than later American bricks, although this may be a consequence of weathering in the case of unit N10E03. This is because they were made from wet clay (soft-mud method) in molds rather than by pressing firm clay which is a more industrialized method requiring specialized equipment. The molds varied in size from place to place until building codes were enacted in the late 19th century defining brick size. The bricks found in N10E03 could also have been hand made, as was typical into the 1830s in the United States (Gurcke 1987: 84-95). Hand made or soft-mud bricks could be easily fired by using a scove or field kiln which would be made from the unfired bricks after they were sufficiently dry (Gurcke 1987: 29-32). This type of kiln was used at Stonewall Mine in the nearby Cuyamaca Mountains to produce a great volume of bricks for the mine and adjacent town of Cuyamaca City (Feature 48; McAleer 1986:95). Construction at the mine and townsite began in 1870, roughly contemporary with Johnson’s construction at the ranch. At Stonewall, the brick production area consisted of a pit for excavation of the clay, a brickyard where the bricks were dried, and the scove itself. Feature 48 was visited by the report author on May 15, 2014, to determine if the appearance of the scove at Stonewall Mine was similar to the features and materials found in unit N10E03. The clay pit was obvious, even after over 100 years. Piles of broken brick and crumbled low-fire clay were present. There was no obvious scorching or burning observed, although this could have been covered by a layer of soil.

In contrast to the scove at Stonewall Mine, the bricks in unit N10E03 were mortared together. Of interest is the fact that chronologically these bricks would be associated with the Johnson period, although no brick construction was found during excavations at the adobe structures. The presence of these few mortared bricks in unit N10E03 is enigmatic.

Further excavation at N10E03 revealed older bricks (Spanish bricks or ladrillos), also in place and mortared together beginning in the 10-20 cm level (Photograph 2).


Photograph 2. Unit N10E03, 20 cm, showing American bricks (lower) and Spanish bricks in place.

Of the four visible Spanish bricks in N10E03, only one was entirely visible. It measures 10″ x 8″ x 1 1/2″. The bricks were placed in a row, end to end. Mortar is visible on the long end of the westernmost brick; it appears that there were other bricks against it at one time. Unfortunately, these could not be completely exposed by the end of the field class.

Spanish bricks are also present in the southern zanja (east end) in addition to unit N10E03. Both whole and fragmented ladrillos were used in the construction of the zanja. The whole bricks were used on the floor of the channel that carried water. Fragments were used, along with small round cobbles, to support the sides of the zanja in a matrix of white mortar. Because the zanja was not damaged or disassembled by the field class, it was not possible to measure a complete ladrillo as used in the floor of the channel. The best example measured 8” long or wide and 2 1/2” thick; one dimension was not possible to obtain since the brick was still in place in the zanja.

Spanish brick sizes of others that were partially visible (one dimension could not be measured):

9½” long or wide, still in mortar

8½” long or wide and 1 ¾” thick

7½ “ long or wide and 1” thick

8½” long or wide, still in mortar

Knowing that the fully exposed Spanish brick in unit N10E03 measures 10” x 8” x 1 ½”, it is likely that the exposed dimension of the zanja bricks is the width rather than the length, and that the longer dimension creates the latest channel bottom of the zanja, extending from one side to the other. It is important to note that these dimensions do not match the standard size for bricks set in Mexico City, which was 1/3 vara long, by 1/6 vara wide, by 3 dedos thick (9” x 4.6” x 1.6”) (Schuetz-Miller 1994: 45). However, as noted in the paragraphs below, there was significant variability in the size of bricks made in Hispanic California.

During the Fall 2014 analysis class, in the collection of historic period ceramics studied by Grace Lemus, a piece of curved tile was identified from the 2013 field class (Photograph 3).


Photograph 3. Curved tile fragment from Unit P5, 46 cm in depth (2013 excavations). Each square is ¼ inch in size.

It was recovered from Unit P5 at 46 cm. (catalog number 13-520). This artifact is a low fired brick, with the marks of having been fired in an open pit or field kiln due to the irregular scorch marks on the interior (indicating variable and uncontrolled firing temperatures). Curved tiles were used as the flow channel in flumes and zanjas (McMorrow 1968; Ressler 1966: 72). Since it has not been possible to view a cross section of the southern zanja, we cannot confirm this proposition, but the form, manufacturing methods, and chronology of the tile piece matches the ladrillos that are present in the water feature. It is unlikely that the tile is from a roof, since no other roof tiles have ever been identified at the ranch, nor was it known to have been roofed with tile historically.

The presence of Spanish bricks and tiles at the site raises an important research question: do they represent possible early 19th century development at the site, perhaps from the Mission period, since they are associated with mission construction methods? Or are they associated with the transport and use of Spanish brick to the ranch from elsewhere during Ruiz’s ownership (Mexican Period)?

No Spanish bricks were found during the many years of excavations at the ranch house. One ladrillo was identified in a feature 600 feet west of the ranch house during monitoring for a mitigation project. Feature 3 consisted of ash and cobbles, in addition to the ladrillo, and both Native American and historic period artifacts. It may be the remains of a Native American house (Van Wormer et al. 2004: 24). No measurement of the size of the brick was provided in the report.

Spanish bricks were used extensively in the construction of the California missions and associated waterworks. Perhaps the best examples of the use of these bricks is at Mission La Purisima (aqueduct finished in 1808) and Mission Santa Barbara (water system c. 1820), where waterworks outbuildings and zanjas extend far beyond the actual mission. In 1840-42, Duflot de Mofras described the standardized construction methods used in the Spanish missions. He stated that the ordinary brick used was 1 ½ to 2 inches thick, and 10” x 10” square (Egenhoff 1952: 181). He also noted that the mortar was made by burning lime, most likely from shell. A lime kiln has been recorded at Mission San Luis Rey (built 1798) but no excavations have been conducted to determine the source of the lime. Mortar used to build the Mission San Diego flume, which was started in 1813, may have come from lime deposits in Mission Valley (McMorrow 1968) although the locations of these purported lime sources has never been verified (White and Cranham 1999: 95). The flume was made from Spanish brick laid at an angle against cobble supports, with a curved roof tile forming the bottom of the channel. Although the Mission Dam flume has been reburied to protect it, an example of one of its Spanish bricks is on display at the Visitor’s Center.

One suggestion has been that the Spanish brick used to build the southern zanja at SDI-8125 was obtained from the Mission San Diego flume. If they were from the Mission San Diego flume, they must have been removed after secularization in 1834. It is unlikely that George Johnson would have used Spanish brick after 1862; his construction at the adobe reflects his American style preferences (see extensive discussions in Hector and Van Wormer 1986). Given this time frame, the southern zanja would have to date to the Mexican period at the site, representing re-use of materials by the Ruiz and Alvarado families.   However, as discussed below, the construction methods represent Spanish Mission Period design and technology.

To test the proposition that the Spanish bricks at SDI-8125 are from the Mission San Diego flume, the author measured several complete Spanish bricks located currently at the Casa Estudillo in Old Town San Diego State Historic Park[1]. During restoration of the casa in 1909, the architect Hazel Waterman had workers remove bricks from the Mission San Diego flume to use as flooring in the rooms (Brandes and Moriarty 1976: 9). The bricks at Casa Estudillo from the flume measure as follows:

Flume Sample 1:           14 ½” x 7” x 2”

Flume Sample 2:           15” x 7” x 1 ½”

Flume Sample 3:           14” x 6 ¾” x 1”

The flume bricks are over twice as long as they are wide. The examples from the southern zanja and unit N10E03 are not of these proportions, being only slightly rectangular. This evidence argues against the proposition that the bricks at SDI-8125 are from the Mission Dam flume.

Cave Couts used masonry from Mission San Luis Rey in his construction of Rancho Guajome Adobe in 1852-53. In addition to relocating the roofing tiles from the mission to his home, Couts also removed Spanish bricks, tiles and large wooden beams. An analysis comparing the Spanish brick at Guajome with those remaining at the mission proved that they were the same (Hector 1999). Transporting the thin, low-fired ladrillos must have resulted in many broken specimens; however, the route from the mission to Guajome is relatively level and easily traveled. In addition, Couts had an abundance of labor and resources to transport the materials. The difficulty of transporting these finished materials from their nearest source, if assumed to be Mission San Diego or its flume, to Los Peñasquitos would argue for their manufacture on site using local clay and molds.

Skowronek et al (2009:7) studied architectural ceramics from the mission period and suggested that trade in roof and floor tiles was impractical due to the weight of the pieces and high likelihood of breakage. Ideally, the bricks were made and fired near the clay source and construction site; the only way to transport the fired bricks and tiles was by oxcart due to their size and weight (Imwalle 2014: 120). It was more economical for low-fired unglazed earthenware to be produced where needed. The technology to do this was available as of 1781 so training and skill were the only necessary ingredients (Skowronek at al. 2014: 179). Training in the skills of masonry were available at the missions beginning in 1769, in San Diego (Schuetz-Miller 1994).

The instrumental neutron activation analyses of architectural ceramics associated with the missions indicated that clays were local. In a study of plain earthenware ceramics from the San Diego region, Skowronek et al. (2014: 186, 212) determined that all were made of local materials – including tile from from San Diego Mission flume, Old Town, Fort Guijarros, and the Presidio.

Preliminary Conclusions from the 2014 Field Class Excavations and Analyses

The 2014 field class excavations were focused on continuing excavations at the zanja features, and a unit placed north of the zanja features. Features found during excavation in these locations provide important information about the chronology and function of the ranch.

As discussed in the beginning paragraphs of the report, the presence of springs was a critical factor to the historic-period settlement at Los Peñasquitos. George Johnson built the spring house[2] and reservoir to control the water flow. Newspaper accounts at the time describe the setting as follows (San Diego Daily World, 8 April 1873, 1:2, 3):

There are two large springs within a few yards of the main building, the waters of which are confined and utilized with rare judgment, supplying the house, the orchard, and the garden with an amount needed for household purposes or irrigation. A beautiful pond is also formed from these springs….

Since there is an elevation difference between the springs and the main house, a hydraulic ram pump could have been used to lift water from the springs or reservoir into a small cistern that was located between Wing B and Wing C. Hydraulic ram pumps were patented in the U.S. in 1809, but were not widely available until 1840 when many companies started offering them for sale. The “water rams” could lift water at least 16’ up to 1000’, depending on the water pressure. The concept of a water ram uses gravity to force water from a spring or running creek into a pipe. When the pipe is full, a valve closes. The force of the water in the closed pipe causes a water hammer to rise under pressure, which opens a delivery valve. This water then flows into the delivery pipe. Water can therefore flow uphill until it slows and starts to backflow, which closes the delivery valve. With the water hammer closed, a suction is produced which draws water into the delivery valve again.

It is also possible that the windmill shown in an 1892 photograph and probably present earlier could have been used to lift the water from the springs (Dr. Stephen Bouscaren, personal communication). In any case, moving water from the springs to the ranch house or dwellings was within the scope of mid-19th century technology.

Archaeological excavations in the zanja and spring house areas have discovered many old iron pipes in the ground running north-south (toward the ranch house). These are in units nearest the spring house, suggesting that this spring was used by Johnson with a water ram to bring water up to the house area.

But if Johnson used a water ram to take water from the spring house or reservoir to his home and gardens, what was the function of the zanjas and how old are they? A newspaper article extolling the value of Peñasquitos to the future of San Diego as a water source noted that there were springs above Johnson’s house that “were walled in with stone and cement, and supplied an irrigating zanja in the old days. Both basin and zanja have been permitted to fall to ruin, but both cold be very readily renewed” (The Daily World, 25 September 1873, 3:1). These statements support the fairly obvious conclusion that the zanja features pre-date Johnson’s occupation of the ranch.

An important research issue is understanding why there are two zanjas at the site, parallel to each other – and which was built first. It is the author’s opinion that the southern zanja is the earlier one, perhaps dating as early as the 1820s (Native/Contact/Mission Period) and built to support mission activities at the rancho. The reason for this assertion is that the southern zanja contains Spanish brick and mortar, and its construction is similar to the methods used by the padres to build mission waterworks. During the mission period, lime for plaster and mortar was made locally from shell or limestone, and was reduced by layering the material with wood fuel. This kiln could have been used to fire bricks (Schuetz-Miller 1994: 43). The kiln might have been a field clamp made out of green bricks, and was therefore disassembled after firing (Imwalle 2014: 123).

In describing “aqueducts” at the missions that are built in the ground, Ressler (1966: 82-84) noted that these channels were built up with sides of cobbles or stone, and lined with mortared brick and tile, with plaster lining at some points. The southern zanja is built in this manner. In contrast, the northern zanja is constructed of large cobbles and small amounts of mortar, similar to the foundation of Wing A which dates to the time Ruiz owned the property.

At some time after construction, the channel of the southern zanja had been filled in with the same mortar that was used to construct it (Photograph 4).


Photograph 4. Southern zanja showing Spanish brick (whole and fragments) incorporated into the structure, and mortar fill in the channel.

The entire opening was filled in, and the top of the mortar plug was neatly flattened and finished. It is not known why the channel was filled in but a possible reason is that the structure shifted or collapsed in places and the filling was an attempt to maintain gravity flow. Ressler (1966: 109-110) noted that San Diego’s mission dam flume was filled and patched with plaster to compensate for uneven grades and settling; in fact he observed that in some areas the channel was filled nearly to the top. Eventually the southern zanja was no longer effectively carrying water to its destination. This may be when the northern zanja was built.

The construction method for the northern zanja was different than the southern zanja (Photographs 5 and 6).


Photograph 5. Southern (top) and northern zanja features showing different construction methods.


Photograph 6. Southern (top) and northern zanja features.

The northern zanja was made from large round cobbles, with small amounts of mortar used to fill the voids between the stones. No Spanish bricks were used. The trough was deeper in the northern zanja, although the southern zanja was more substantial in bulk.

Johnson built over the zanjas when he was developing and expanding his ranch. He built his spring house and reservoir over the features. He also built a structure referred to by archaeologists as a “lath barn” on top of the two zanjas (his name appears on one of the pieces of lumber used to construct the building). This structure was the focus of Dr. Christenson’s San Diego State University field class in 1992. Dr. Christenson exposed the entire interior of the structure, revealing a heavy wooden floor. Conjecture over the function of this small building has continued over the decades of archaeological investigation[3], but its position between two springs supports the use of this wooden building as a wash house or bath house (see below; such a building was noted as present). Such structures would have been located next to a spring or flowing stream. By the time Johnson was expanding his ranch, the zanja features were in ruin.

Preliminary analysis of the zanja features indicates that the southern zanja was built first, possibly during the Native/Contact/Mission Period, to convey water from a spring to the downstream fields. This conclusion is based on construction methods, materials used, and the attempted repairs of the zanja that led to the development of the northern zanja during the Mexican Period when the southern one could no longer convey water. Repairs to the collapsing southern zanja consisted of filling in the channel to try and maintain gravity flow – to the point where the channel was completely filled in some sections.

A possible demolished structure perhaps dating to the Native/Contact/Mission or Mexican periods was identified during 2014. Unit N10E03 contained pieces of brick slag and coal. Pieces of lumber and square cut nails were also identified, as well as a large quantity of window glass. Wire nails were also present in the unit. A large piece of abalone shell was recovered intermixed with loose bricks. During excavation, smears of clay and mortar were recorded in the unit as excavation proceeded. The presence of construction materials, including mortared American and Spanish brick, supports a preliminary conclusion that a building once stood in this location. Coal and brick slag may indicate that a scove was located nearby as well. Intact Spanish brick could mean that the feature dates to the Native/Contact/Mission or Mexican periods, although the American brick and construction artifacts are mid-19th century. Further excavation is necessary to understand the function and chronology of this feature. Images from the 1880s show buildings in this vicinity, and the ranch had “outhouses, barns, stables, milkhouse[4], wash-house, and bath-house” (San Diego Union Weekly, 24 March 1869), many of which have not been identified archaeologically. It is possible that Unit N10E03 and the area adjacent to it contain evidence for a previously unidentified structure.


The author would like to acknowledge the work and support of Amy Ross, who is the City College lab and field tech for the analysis and excavation classes. Her diligence and attention to detail are noteworthy. In addition, the project could not proceed without the support provided by Dr. Stephen Bouscaren, Dean Lori Erreca, and Dr. Tori Randall of City College; and Beth Dirksen, Cailin Hunsaker, and Paul Kucharczyk of San Diego County Parks. Ellen Sweet and the staff at the History Center of the Department of Parks and Recreation answered questions, conducted research, and provided documents that supported analysis of the artifacts and features at the site. Jake Enriquez and the staff of Rancho Guajome Adobe National Historic Landmark provided access to that building and participated in discussions that helped with questions about architectural ceramics.   Finally, the students and volunteers who worked with the author at the site in 2014 are commended for their dedication, work ethic, and serious approach to the research. City College students are the best ever, no question about it.

References Cited

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[1] Thank you to Burt Randlett and the staff of Old Town San Diego State Historic Park for allowing the author to have access to the interior rooms of Casa Estudillo and for providing information on the 1909 restoration.

[2] The stone structure currently called the Spring House is labeled as a Milk House on some maps. Its construction methods support the use of the building to store milk and other perishable foods.

[3] The structure is called a Chicken Coop on some Department of Parks and Recreation maps.

[4] Most likely the stone building over the spring now referred to as the Spring House.

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