diff --git a/cache/image_cache.go b/cache/image_cache.go
index 461a4446..7023b784 100644
--- a/cache/image_cache.go
+++ b/cache/image_cache.go
@@ -119,7 +119,7 @@ func (c *ImageCache) RetrieveLayer(diffID string) (io.ReadCloser, error) {
 		if IsLayerNotFound(err) {
 			return nil, NewReadErr(fmt.Sprintf("failed to find cache layer with SHA '%s'", diffID))
 		}
-		return nil, NewReadErr(fmt.Sprintf("unknown error retrieving layer with SHA '%s'", diffID))
+		return nil, fmt.Errorf("failed to get cache layer with SHA '%s'", diffID)
 	}
 	return closer, nil
 }
@@ -143,28 +143,3 @@ func (c *ImageCache) Commit() error {
 
 	return nil
 }
-
-// LayerExists checks if a layer exists in the cache
-func (c *ImageCache) LayerExists(diffID string) (bool, error) {
-	layers, err := c.origImage.UnderlyingImage().Layers()
-	if err != nil {
-		return false, errors.Wrap(err, "getting image layers")
-	}
-
-	for _, layer := range layers {
-		d, err := layer.DiffID()
-		if err != nil {
-			return false, errors.Wrap(err, "getting layer diffID")
-		}
-
-		if d.String() == diffID {
-			return true, nil
-		}
-	}
-	return false, nil
-}
-
-// Destroy deletes the cache image
-func (c *ImageCache) Destroy() {
-	c.imageDeleter.DeleteImage(c.origImage)
-}
diff --git a/cache/image_cache_test.go b/cache/image_cache_test.go
index 67e370bf..3a92c45e 100644
--- a/cache/image_cache_test.go
+++ b/cache/image_cache_test.go
@@ -146,7 +146,7 @@ func testImageCache(t *testing.T, when spec.G, it spec.S) {
 		when("layer does not exist", func() {
 			it("returns an error", func() {
 				_, err := subject.RetrieveLayer("some_nonexistent_sha")
-				h.AssertError(t, err, "unknown error retrieving layer with SHA 'some_nonexistent_sha'")
+				h.AssertError(t, err, "failed to get cache layer with SHA 'some_nonexistent_sha'")
 			})
 		})
 	})
@@ -236,7 +236,7 @@ func testImageCache(t *testing.T, when spec.G, it spec.S) {
 					h.AssertNil(t, subject.AddLayerFile(testLayerTarPath, testLayerSHA))
 
 					_, err := subject.RetrieveLayer(testLayerSHA)
-					h.AssertError(t, err, fmt.Sprintf("unknown error retrieving layer with SHA '%s'", testLayerSHA))
+					h.AssertError(t, err, fmt.Sprintf("failed to get cache layer with SHA '%s'", testLayerSHA))
 				})
 			})
 		})
diff --git a/cache/volume_cache.go b/cache/volume_cache.go
index 27da502d..ce1a5ee2 100644
--- a/cache/volume_cache.go
+++ b/cache/volume_cache.go
@@ -168,7 +168,7 @@ func (c *VolumeCache) RetrieveLayer(diffID string) (io.ReadCloser, error) {
 		if os.IsPermission(err) {
 			return nil, NewReadErr(fmt.Sprintf("failed to read cache layer with SHA '%s' due to insufficient permissions", diffID))
 		}
-		return nil, NewReadErr(fmt.Sprintf("unknown error retrieving layer with SHA '%s'", diffID))
+		return nil, fmt.Errorf("failed to get cache layer with SHA '%s'", diffID)
 	}
 	return file, nil
 }
@@ -228,22 +228,3 @@ func (c *VolumeCache) setupStagingDir() error {
 	}
 	return os.MkdirAll(c.stagingDir, 0777)
 }
-
-// LayerExists returns true if the layer with the given diffID exists in the cache
-func (c *VolumeCache) LayerExists(diffID string) (bool, error) {
-	path := diffIDPath(c.committedDir, diffID)
-	if _, err := os.Stat(path); err != nil {
-		if os.IsNotExist(err) {
-			return false, nil
-		}
-		return false, errors.Wrapf(err, "retrieving layer with SHA '%s'", diffID)
-	}
-	return true, nil
-}
-
-// Destroy removes the cache directory and all its contents
-func (c *VolumeCache) Destroy() {
-	if err := os.RemoveAll(c.dir); err != nil {
-		c.logger.Warnf("Unable to delete cache directory: %v", err.Error())
-	}
-}
diff --git a/cache/volume_cache_test.go b/cache/volume_cache_test.go
index 161d72e2..fe14f529 100644
--- a/cache/volume_cache_test.go
+++ b/cache/volume_cache_test.go
@@ -211,7 +211,7 @@ func testVolumeCache(t *testing.T, when spec.G, it spec.S) {
 			when("layer does not exist", func() {
 				it("returns an error", func() {
 					_, err := subject.RetrieveLayer("some_nonexistent_sha")
-					h.AssertError(t, err, "Layer with SHA 'some_nonexistent_sha' not found")
+					h.AssertError(t, err, "failed to find cache layer with SHA 'some_nonexistent_sha'")
 				})
 			})
 		})
@@ -235,7 +235,7 @@ func testVolumeCache(t *testing.T, when spec.G, it spec.S) {
 			when("layer does not exist", func() {
 				it("returns an error", func() {
 					_, err := subject.RetrieveLayerFile("some_nonexistent_sha")
-					h.AssertError(t, err, "Layer with SHA 'some_nonexistent_sha' not found")
+					h.AssertError(t, err, "failed to find cache layer with SHA 'some_nonexistent_sha'")
 				})
 			})
 		})
@@ -345,7 +345,7 @@ func testVolumeCache(t *testing.T, when spec.G, it spec.S) {
 						h.AssertNil(t, subject.AddLayerFile(tarPath, "some_sha"))
 
 						_, err := subject.RetrieveLayer("some_sha")
-						h.AssertError(t, err, "Layer with SHA 'some_sha' not found")
+						h.AssertError(t, err, "failed to find cache layer with SHA 'some_sha'")
 					})
 				})
 
@@ -420,7 +420,7 @@ func testVolumeCache(t *testing.T, when spec.G, it spec.S) {
 						h.AssertNil(t, subject.AddLayer(layerReader, layerSha))
 
 						_, err := subject.RetrieveLayer(layerSha)
-						h.AssertError(t, err, fmt.Sprintf("Layer with SHA '%s' not found", layerSha))
+						h.AssertError(t, err, fmt.Sprintf("failed to find cache layer with SHA '%s'", layerSha))
 					})
 				})
 
diff --git a/phase/exporter.go b/phase/exporter.go
index a6bce1dd..4808e857 100644
--- a/phase/exporter.go
+++ b/phase/exporter.go
@@ -34,9 +34,7 @@ type Cache interface {
 	AddLayerFile(tarPath string, sha string) error
 	ReuseLayer(sha string) error
 	RetrieveLayer(sha string) (io.ReadCloser, error)
-	LayerExists(sha string) (bool, error)
 	Commit() error
-	Destroy()
 }
 
 type Exporter struct {